xac dinh crpm trong nuoc va dat
TRANSCRIPT
-
8/3/2019 Xac Dinh Crpm Trong Nuoc Va Dat
1/37
CHAPTER 2
NEW REAGENTS FOR THE SPECTROPHOTOMETRIC
DETERMINATION OF CHROMIUM
2.1 INTRODUCTION
2.2 ANALYTICAL CHEMISTRY
2.3 APPARATUS
2.4 REAGENTS AND SOLUTIONS
2.5 PROCEDURES
2.6 RESULTS AND DISCUSSION
2.7 APPLICATIONS
2.8 CONCLUSIONS
2.9 REFERENCES
-
8/3/2019 Xac Dinh Crpm Trong Nuoc Va Dat
2/37
2.1 INTRODUCTION
Chromium was discovered by Nicolas-Louis Vauquelin in 1797 in Siberian
red lead, the mineral crocoite (PbCrO4). Chromium is the sixth most abundant
element in the earths crust. This metal always occurs in combination with other
elements, displaying a wide variety of colors. Fourcroy and Huay suggested the
name chromium (from Greek chroma means color) for this new element because of
its many colored compounds [1]. In 1798, Tobias Lowitz and Martin Heinrich
Klaproth independently found chromium in chromite samples from Russia, and also
Tassaert, a German Chemist at the Paris school of Mines, found it in French
chromite. This ore, a spinel, Fe(CrO2)2, is the only commercial sources of chromium.
Chromium metal was obtained by Moissan in 1893 by reduction of chromic oxide
with carbon in electric furnace. In 1894 Goldschmidt developed the alumino
thermite process for producing chromium by reduction of oxide with aluminium
powder [2]. The only impartant chromium ore is chromite, a spinel [3]. Only
meterorites contain free chromium and most chromium appears in chromite ore,
which contains iron and oxygen [4]. Exposure to chromium compounds occurs
primarily in the occupational setting where chromium commonly is used in the
following 3 basic industries: chemical, metallurgical, and refractory (heat-resistant).
The carcinogenesis of hexavalent chromium compounds was recognized first in the
late 19th century when nasal tumors were described in Scottish chrome pigment
workers [5]. Case reports in the 1930s focused attention on the incidence of lung
cancer in chromate workers, and lung cancer in German chromate workers was
accepted as a work-related disease in 1936 [6].
In the 1960s and 1970s, chromium containing slag was a substantial
component of landfills in a variety of residential and commercial settings in HudsonCounty, New Jersey. Health concerns about exposure to this soil were based on
experience with workers exposed to chromium. Epidemiological studies of chromate
workers indicate an increased risk of death from lung cancer in workers exposed to
hexavalent chromium compounds [7,8]. Hexavalent chromium compounds are both
skin and pulmonary sensitizers, producing a generalized irritation of the conjunctiva
and mucous membranes, nasal perforations [9], and a contact dermatitis [10]
(Blackjack disease in card players exposed to chromium in green felt). Trivalent
-
8/3/2019 Xac Dinh Crpm Trong Nuoc Va Dat
3/37
chromium is an essential trace metal necessary for the formation of glucose
tolerance factor and for the metabolism of insulin.
The two most important function of chromium in steels are improving the
mechanical properties particularly hardenability and increasing the corrosion
resistance [11]. The magnitude of the effect in each case is roughly proportional to
the percent chromium in steel. Low chromium steels (< 3 % of Cr) produced in all
structural shapes such as bars, tubes, sheets, plates etc., are used extensively as
engineering materials in every branch of industry. For all but heaviest duty
applications, chromium content is generally less than 6%. Steels contain more than
10% chromium and are designated stainless because of their resistance to corrosion
and oxidation. Non-hardenable grade contain 0.08-0.2 % carbon and 11.25-27.0%
chromium. Type 430 (AISI) is used in large quantities for trim on buildings,
automobiles, etc., and for nitric acid manufacturing equipment. The austenitic
stainless steels (non-hardenable) contain 16-26% of chromium and 0.15-1.25%
carbon.
Chromium is the recently recognized biologically essential trace metal. The
first conclusive evidence demonstrating a metabolic role of chromium was obtained
by Mertz and Schwarz in a series of investigation of which the first report appeard in
1955 [12,13].
Trivalent chromium is an essential trace metal necessary for the normal
metabolism of cholesterol, fat and glucose. Although trivalent chromium has the
potential to form complexes with proteins and nucleic acids, hexavalent chromium
must first be converted to the trivalent state before it combines with nucleic acids
and proteins [14]. Trivalent chromium forms tight bonds with oxygen and sulfur
containing ligands and some chromium complexes with histidine and cysteine are
relatively inert because of these tight bonds [15]. Trivalent chromium potentiates the
action of insulin, probably through a glutathione-like complex composed of niacin,
trivalent chromium and amino acids [16].
Chromium deficiencies in the diet produce elevated circulating insulin
concentrations, hyperglycemia, hypercholesterolemia, elevated body fat, decreased
sperm counts, reduced fertility, and a shortened life span. Severe chromium
-
8/3/2019 Xac Dinh Crpm Trong Nuoc Va Dat
4/37
deficiency may cause weight loss, poor coordination, destruction of the nerves in the
extremities of the body and inflammation of the brain. The effects of excessive
dietary chromium are not well known. Some forms of chromium that are found in
the environment may be cancer causing (carcinogenic), but this type of chromium is
different from dietary chromium. Food with high chromium content are fruits,
vegetables, whole grains (oats and barley) seeds, nuts, legumes (peas and beans) and
brewers yeast. When these food is processed, particularly using stainless steel
equipment (e. g. when cocking or canning), their chromium content may increase.
Allergy to chromium compounds carries in men a worse prognosis than dose
sensitization to other allergens. The reason is not known. Continued contact with
unrecognized chromium compounds in the environment or possibly ingestion of
chromium compounds have been considerd as possible explanation [17].
The determination of micro amounts of chromium in soil and other naturally
occurring materials are of considerable interest because of the contrasting biological
effects of its two common oxidation states, chromium(III) and chromium(VI).
Chromium(III) is an essential nutrient for maintaining normal physiological function
[18] whereas, chromium(VI) is toxic [19]. It is difficult, however, to determine
chromium directly in natural water samples because of its very low concentration
level. It is known that an increase in the content in soils makes them infertile and
toxic effect depends to some extent on the chromium oxidation state. On the other
hand the introduction of chromium salts in to soil have some positive effects due to
activation of some biochemiocal processes [20].
2.2 ANALYTICAL CHEMISTRY
Many methods have been reported for the quantitative determination of
chromium. The analytical technique varies from intensively coupled plasma-atomic
emission spectroscopy [21], neutron activation analysis [22], X-ray absorption
spectroscopy [23], atomic absorption spectroscopy [24], complexometry [25],
catalytic-kinetic [26], flow injection [27], sequential injection [28,29] to flourogenic
method [30]. Divrikli et al. [31] developed a method for the determination of
chromium based on co-precipitation with cerium(IV) hydroxide by flame atomic
absorption spectrometry.
-
8/3/2019 Xac Dinh Crpm Trong Nuoc Va Dat
5/37
A survey of literature revealed that a large number of reagents are suitable
for the spectrophotometric determination of chromium. Cahnmann and Ruth [32]
used 1,5-diphenylcarbazide as a spectrophotometric reagent for the determination of
chromium in blood, in the course of investigations of lung cancers among chromium
workers by using a Beckman DU spectrophotometer and a wave length of 543 nm,
the reaction was sensitive to 0.005 ppm.
Miller and Yoe [33] used diphenylcarbazide as a spectrophotometric reagent
for the determination of chromium in human plasma and red cells. Traces of
chromium in human blood was determined by a method which utilized the red-violet
complex formed by the reaction of Cr2O72- with diphenylcarbazide. The
concentration of chromium in normal human plasma ranged from 0.017 to 0.052
ppm, which was in good agreement with previously reported values. The
concentration of chromium in red cells ranged from 0.014-0.038 ppm. Standard
deviation by the method was 1.6%. Motojima and Hashitani [34] reported 8-
hydroxyquinaldine as a spectrophotometric reagent for the determination of
chromium in uranium. Todorovska et al. [35] described the direct electrothermal
atomic absorption spectrometry (ETAAS) for the determination of chromium in
serum and urine samples without any preliminary sample pretreatment. Rosa and
Maria [36] determined the total amount of chromium based on an on-line
ultrasound-assisted sample digestion procedure exploiting the stopped-flow mode,
followed by flow injection chromium preconcentration using a minicolumn filled
with a commercially available chelating resin (Chelite Che).
Hoshi et al. [37] proposed a method for the spectrophotometric
determination of chromium(VI) based on preconcentration with collection of metal
complexes on a chitin has been applied to the spectrophotometric determination of
chromium(VI) in water. The chromium(VI) was collected as its 1,5-
diphenylcarbazide -(DPC) complex on a column of chitin in the presence of dodecyl
sulfate as counter-ion. The Cr-DPC complex retained on the chitin was eluted with a
methanol-1 M acetic acid mixture (7:3) and the absorbance of the eluent was
measured at 541 nm. Revanasiddappa and Kiran Kumar [38] used leuco xylene
cyanol-FF as a sensitive reagent for the spectrophotometric determination of trace
amounts of chromium in steels, industrial effluents and pharmaceutical samples.
-
8/3/2019 Xac Dinh Crpm Trong Nuoc Va Dat
6/37
The method was based on the oxidation of leuco xylene cyanol-FF to its blue form
of xylene cyanol-FF by Cr(VI) in H2SO4 medium (pH 1.2-2.4), the absorbance of
the formed dye was measured in an acetate buffer medium (pH 3.0-4.6) at 615 nm.
The method was obeyed Beers law in the concentration range of 0.05-mL-1
of chromium. Molar absorptivity and Sandells sensitivity of the system was
8.23x104 L mol-1cm-1-2
Narayana and Cherian [39] used variamine blue as a chromogenic reagent for
the spectrophotometric determination of trace amounts of chromium.
Chromium(VI) reacts with potassium iodide in acid medium to liberate iodine,
which oxidizes variamine blue to form a violet colored species having an absorption
maximum 556 nm. Beers law was obeyed in the range 2-12 gmL -1 of Cr(VI).
Same authors used azure B [40] as a chromogenic reagent for the
spectrophotometric determination of trace amounts of chromium. The method was
based on the oxidation of azure B. Molar absorptivity and Sandells sensitivity of the
system were found 3.77x104 L mol-1cm-1 and 2.76x10-2 gcm-2 respectively. Cheng
[41] used xylenol orange and methylthymol blue as chromogenic reagents for the
spectrophotometric determination of trace amounts of chromium. The molar
absorptivity was found to be 19.0 x 103
L mol-1
cm-1
. Mohamed and El-Shahat [42]
developed a method for the spectrophotometric determination of Cr(VI) based on
their reactions with perphenazine to instantaneously give a red colored product
exhibiting a maximum absorbance at 526 nm. Girish Kumar and Muthuselvi [43]
used 2-hydroxybenzaldiminoglycine as a reagent for the spectrophotometric
determination of trace amounts of chromium.
Zaitoun [44] described a method for the spectrophotometric determination of
chromium(VI), based on the absorbance of its complex with 1,4,8,11-
tetraazacyclotetra-decane (cyclam). The complex showed a molar absorptivity of 1.5
104
L mol-1
cm-1
at 379 nm. Under optimum experimental conditions, a pH of
4.5 and 1.960 103
mgL-1
cyclam were selected, and all measurements were
performed 10 min after mixing. Major cations and anions did not showed any
interference; Beer's law was obeyed in the concentration range 0.2-20 mgL-1
with a
detection limit of 0.001 mgL-1
. The standard deviation in the determination is 0.5
-
8/3/2019 Xac Dinh Crpm Trong Nuoc Va Dat
7/37
mg L-1 for a 15.0 mg L-1 solution. Carvalho et al. [45] used 4-(2-thiazolylazo)-
resorcinol as a reagent for the spectrophotometric determination of chromium.
Boef and Poeder [46] described spectrophotometric determinations of
milligram amounts of chromium(III) with complexans, based on the fact that the
chromium(IIl) complexes are formed rapidly at boiling temperatures, but very
slowly at room temperature, while the formation of some interfering complexes
takes place instantaneously. Determinations with EDTA were more sensitive, but the
combined presence of cobalt and other metals still interferes; there was no
interference with the less sensitive NTA. The combined presence of a l00-fold
amount of copper, nickel, cobalt and iron generally has no effect on the results. The
use of DCTA, DTPA and HEDTA was discussed. Katsuya and Yukiteru [47] used
2-hydroxy-1-(2-hydroxy-4-sulfo-1-naphtyhylazo)-naphthalein, Jacobsen and Lund
[48] used 3-thianaphthenoyltrifluoro-acetone and Johnston and Holland [49] used
thioglycollic acid for the spectrophotometric determination of chromium.
Yotsuyanagi et al. [50] described the extraction-spectrophotometric
determination of chromium(III) with 4-(2-pyridylazo)-resorcinol (PAR). PAR(H2R)
forms a 1:3 complex with chromium(III) in a boiling acetate buffer solution at pH 5.
The complex forms an ion-association compound with tetradecyldimethylbenzyl
ammonium ion (TDBA+):Cr(R)(HR)2
--TDBA
+which can be extracted into
chloroform, the molar absorptivity being 4.7x104
at 540 nm. If EDTA was added as
a masking agent after the Cr(HR)3 has been formed, only iron, cobalt and nickel
interfere seriously, and the method can be made specific for chromium by a
preliminary extraction of these metals with cupferron. The sensitivity of the method
was seven times higher than that of the diphenylcarbazide method. Gowda and Raj
[51] reported fluphenazine hydrochloride as a reagent for the determination of
chromium. Fluphenazine hydrochloride formed a red colored species with
instantaneously at room temperature in 2.0- 5.5 M H3PO4 medium. The red colored
species exhibited maximum absorbance at 500 nm with molar absorptivity of
2.061x 104 L mol-1cm-1. Beers law was valid over the concentration range 0.05-1.85
ppm of chromium. Rizvi et al. [52] used tropolone for the spectrophotometric
determination of chromium. Chromium formed a golden yellow complex with
-
8/3/2019 Xac Dinh Crpm Trong Nuoc Va Dat
8/37
tropolone on heating on a water bath, the colored moiety was extracted in CHCl3.
The complex exhibited maximum absorbance at 400 nm.
Hussain and Venkata [53] used cyclohexane-1,3-dionebisthiosemicarbazione
monohydrochloride for the rapid spectrophotometric determination of chromium(VI).
The reagent produced yellow colored solutions with Cr(VI) in NaOAC-HCl medium.
Molar absorptivity value of the system was 1.21x104
L mol-1
cm-1
at 370 nm.
Nagaraj et al. [54] developed a spectrophotometric method for the determination of
chromium. The method was based on the diazotization of dapsone in hydroxylamine
hydrochloride medium and coupling with N-(1-napthyl)ethylenediamine
dihydrochloride by electrophilic substitution to produce an intense pink azo-dye,
which has absorption maximum at 540 nm. The Beer's law was obeyed from
0.02--1
and the molar absorptivity was 3.4854x104
L mol-1
cm-1
. The limits
-1 and
-1
respectively. Ram et al. [55] used malachite green for the
spectrophotometric determination of chromium in waste water. Reagent formed a
green colored complex with chromium in acetic acid at pH 2.5. The Molar
absorptivity of the system was found to be 8.0x104
L mol-1
cm-1
at 560 nm.
Benzyltributylamonium [56] was also reported as spectrophotometric reagent for the
determination of chromium in waste water and steels.
Fabiyi et al. [57] reported, variamine blue as a chromogenic reagent for the
spectrophotometric determination of nano amounts of chromium. Chromium(VI)
reacts with potassium iodide in acid medium to liberate iodine that oxidizes
variamine blue to produce violet-colored substances having an absorption maximum
at 615 nm with molar absorptivity of 8.12x104
L mol-1
cm-1
. Beers law was valid
over the concentration range 0.0003-15 -1
. Kamburova [58] described for the
spectrophotometric determination of chromium. The interaction of
iodonitrotetrazolium chloride and tetrazolium violet with chromium(VI) has been
studied and the formation of ion-associates with a 1:1 composition in hydrochloric
acid medium established. Extraction photometric methods for determination of
chromium in steels and soils have been developed. Same author used methylene blue
[59] as reagent for the determination of chromium. The interaction of Cr(VI) and the
thiazine dye methylene blue has been examined. The ion-associate formed is
-
8/3/2019 Xac Dinh Crpm Trong Nuoc Va Dat
9/37
extractable into 1,2-dichlorethane. Triphenyltetrazolium chloride [60] used by the
same author for the spectrophotometric determination of chromium.
Yoshiaki et al. [61] described a method for the determination of chromium.
Chromium(VI) reacts with O,O-dibutyl dithiophosphate ion to form tris(dibutyl
dithiophosphato)chromium(III) and tetrabutyl thiophosphoryl disulfide in an acidic
solution (pH 1.2-1.7). Both of the products are extracted into hexane and the
absorbance at 278 nm based on these products was utilized for the determination of
chromium(VI). The chromium(III) complex corresponding to two-thirds of the
initial chromium(VI) concentration and the disulfide corresponding to three-halves
of the initial chromium(VI) concentration were extracted under the optimum
conditions. The calibration graph obtained is linear over the range of
210-6
-110-4
mol/dm3
chromium(VI) concentration, and the apparent molar
absorptivity was 1.69104
mol-1
dm3
cm-1
. Arya and Anvita [62] used ferron for the
spectrophotometric determination of chromium.
Raj and Gowda [63] described a method for the spectrophotometric
determination of chromium by using thioridazine hydrochloride. The reagent forms
a blue colored radical cation with chromium(VI) instantaneously at room
temperature in 14 mol L1
orthophosphoric acid medium. The blue species exhibits
an absorption maximum at 640 nm with a molar absorption coefficient of
2.577104
L mol1
cm1
. Rosa et al. [64] proposed a method for the
spectrophotometric determination of chromium with 2-(5-chloro-2-pyridylazo)-5-
dimethylaminophenol. A useful absorptionmetric method was proposed for Cr(III)
in concentrations ranging from 15 to 400 ppb. The methods were applied to
chromium determination in water samples with very satisfactory results. Maheswari
and Balasubramanian [65] used Rhodamine-6G, Ressalan et al. [66] used
3-hydroxy-3-phenyl-1-o-hydroxyphenyltriazene and Ressalan et al. [67] used
3-hydroxy-3-phenyl-p-tolyl-1-o-nitrophenyltriazene for the determination of
chromium.
Melwanki and Seetharamappa [68] reported propericiazine as a
spectrophotometric reagent for the determination of chromium in environmental
samples. Propericiazine formed a red colored radical cation, exhibited maximum
absorption at 510 nm in H3PO4 medium. Beers law was valid over the concentration
-
8/3/2019 Xac Dinh Crpm Trong Nuoc Va Dat
10/37
range of 0.15-2.25 mgL-1. The Sandells sensitivity of the reaction was found to be
3.42 ngcm-2
. Methdilazine hydrochloride [69] was also reported as reagent for the
spectrophotometric determination of chromium. Revanasiddappa and Kiran Kumar
[70] used trifluroperazine hydrochloride as a reagent for the spectrophotometric
determination of chromium. The method was based on the oxidation of
trifluroperazine hydrochloride by chromium(VI) in the presence of H3PO4. The red
colored species exhibited an absorption maximum at 505 nm. The system was
obeyed Beers law at 2-18 g of chromium(VI) in a final volume of 10 mL. The
molar absorptivity of the color system was 2.08x104 L mol-1 cm-1 and the developed
color was stable for 2 hours.
Lourenco et al. [71] reported a spectrophotometric method for the
determination of chromium, which was based on the formation of
chromium(III)/azide complexes was established by investigating a new band in the
ultraviolet region. The maximum molar absorptivity coefficient at 287 nm
(1.4810.008104 L mol-1 cm-1), leading to the determination of metal ion
concentrations one hundred times lower than the ones formerly determined in the
visible region. The system obeyed Beers law and is suitable for chromium
determination in the 0.702-2.81 mgL-1
concentration range. Revanasiddappa and
Kiran Kumar [72] reported citrazinic acid as a new coupling agent for the
spectrophotometric determination of trace amounts of chromium by oxidation of
hydroxylamine in acetate buffer of pH 4.00.5. Molar absorptivity of the system was
2.12x104
L mol1
cm1
and Sandells sensitivity of the system was 0.00246 gcm-2
at
470 nm. The color was stable for 6 hours and the system was obeyed Beers law in
the range 2.0-15 g of Cr(VI) in a final volume of 10 mL.
Cherian and Narayana [73] reported saccharin as a new coupling agents for
the spectrophotometric determination of chromium. The method obeyed Beers law
in the concentration range of 1-16 gmL1
for chromium with p-nitroaniline-
saccharin and 0.6-14 gmL1 of chromium with sulphanilamide-saccharin couples.
The molar absorptivity, Sandells sensitivity of the systems with p-nitroaniline-
saccharin and sulphanilamide-saccharin couples were found to be
5.41104
L mol1
cm1
, 1.93103
gcm2
and 2.63104
L mol1
cm1
, 3.9103
gcm2
, respectively.
-
8/3/2019 Xac Dinh Crpm Trong Nuoc Va Dat
11/37
Tarafder et al., [74] reported an improved spectrophotometric method for
chromium(VI) determination in rocks, minerals and water samples. The method was
based on the determination of nitrite produced by Cr(VI) during the oxidation of
hydroxylamine (NH2OH). Beer's law was obeyed in the range of 0.02-10 gmL-1
of
Cr(VI). The molar absorptivity and Sandell's sensitivity of the system were found to
be 4.2x104 L mol-1 cm-1 -2, at 540 nm Comparison of
spectrophotometric reported methods for the determination of chromium(VI) with
proposed method are summarized in table 2.1
The aim of the present work is to provide a simple and sensitive method for
the determination of chromium using -naphthol,-naphthol, pyrocatechol and N-
(1-naphthyl)ethylenediamine dihydrochloride as new coupling agents. The proposed
method has been employed to the determination of chromium in alloy, soil sample
pharmaceutical preparation and natural water samples.
2.3 APPARATUS
2.3.1 Spectrophotometer
A SHIMADZU (Model No: UV-2550) UV-Visible spectrophotometer with
1 cm matching quartz cells were used for the absorbance measurements.
2.3.2 pH Meter
A WTW pH 330 pH meter was used.
2.4 REAGENTS AND SOLUTIONS
All chemicals used were of analytical reagent grade, and doubly distilled
water was used in the preparation of all solutions in the experiments. Standard stock
solution containing 1000 gmL
-1
of chromium(VI) was prepared by dissolving0.2829 g of K2Cr2O7 in 100 mL volumetric flask with distilled water and
standardized by titrimetric method [25]. The stock solution was further diluted as
needed. 2,4-Dinitrophenylhydrazine (DNPH)(1%), -naphthol (1%), -naphthol
(1%), pyrocatechol (1%) and N-(1-naphthyl)ethylenediamine dihydrochloride
(NEDA)(1%) were used. The following reagents were prepared by dissolving
appropriate amounts of reagents in distilled water: 2M HCl and 2M NaOH.
-
8/3/2019 Xac Dinh Crpm Trong Nuoc Va Dat
12/37
2.5 PROCEDURE
2.5.1 Using 2,4-Dinitrophenylhydrazine--Naphthol as Reagents
Aliquots of sample solution containing 0.02-4.0 gmL-1
of chromium(VI)
was transferred in to series of 10 mL calibrated flask. To each of the flask, 1 mL of
2,4-dinitrophenylhydrazine and 1 mL of 2 M HCl solutions were added. Each
-naphthol and
1 mL of 2M NaOH solution, again allowed to stand for 5 min with occasional
shaking to complete the reaction. After dilution to 10 mL with distilled water, the
absorbance of the red colored dye was measured at 663 nm against the
corresponding reagent blank and the calibration graph was constructed. The results
are summarized in table 2.2A
2.5.2 Using 2,4-Dinitrophenylhydrazine- -Naphthol as Reagents
Aliquots of sample solution containing 0.05-9.0 gmL-1
of chromium(VI)
was transferred in to series of 10 mL calibrated flask. To each of the flask, 1 mL of
2M HCl and 1 mL of 2,4-dinitrophenylhydrazine solution were added. Each mixture
-naphthol and 1 mL of
2M NaOH, again allowed to stand for 5 min with occasional shaking to complete the
reaction. After dilution to 10 mL with distilled water, the absorbance of the violet
colored dye was measured at 503 nm against the corresponding reagent blank and
the calibration graph was constructed. The results are summarized in table 2.2B
2.5.3 Using 2,4-Dinitrophenylhydrazine- Pyrocatechol as Reagents
Aliquots of sample solution containing 0.1-6.0 gmL-1
of chromium(VI) was
transferred in to 10 mL calibrated flask. To each of the flask, 1 mL of 2 M HCl and
1 mL of 2,4-dinitrophenylhydrazine solution were added. Each mixture was allowed
to stand for 5 min, and then added 1 mL of 1% pyrocatechol and 1 mL of 2M
NaOH, again allowed to stand for 5 min with occasional shaking to complete the
reaction. After dilution to 10 mL with distilled water, the absorbance of the violet
colored dye was measured at 619 nm against the corresponding reagent blank and
the calibration graph was constructed. The results are summarized in table 2.2C.
-
8/3/2019 Xac Dinh Crpm Trong Nuoc Va Dat
13/37
2.5.4 Using 2,4-Dinitrophenylhydrazine- N-(1-Naphthyl)ethylenediamine
Dihydrochloride as Reagents
Aliquots of sample solution containing 0.01-4.0 gmL-1
of chromium(VI)
was transferred in to series of 10 mL calibrated flask. To each of the flask, 1 mL of
2,4-dinitrophenylhydrazine and 1 mL of 2 M HCl solutions were added. Each
mixture was allowed to stand for 5 min, then added 1 mL of 1% N-(1-
naphthyl)ethylenediamine dihydrochloride and 1 mL of 2M NaOH solution, again
allowed to stand for 5 min with occasional shaking to complete the reaction. After
dilution to 10 mL with distilled water, the absorbance of the red colored dye was
measured at 525 nm against the corresponding reagent blank and the calibration
graph was constructed. The results are summarized in table 2.2D
2.5.5 Analysis of Chromium in Alloy Steel
About 0.1 g of a steel sample containing 1.02% of chromium was weighed
accurately and placed in a 50 mL beaker. To it, added 10 mL of 20% H2SO4 and
carefully covered with a watch glass until the brisk reaction subsided. The solution
was heated and simmered gently after addition of 5 mL of conc. HNO3 until all
carbides were decomposed. Then, 2 mL of a 1:1 H2SO4 solution was added and the
mixture was evaporated carefully until the dense white fumes derived off the oxides
of nitrogen, and then cooled to room temperature. After appropriate dilution with
water, the contents of the beaker were warmed to dissolve the soluble salts. The
solution was then cooled and neutralized with a dilute NH4OH solution. The
resulting solution was filtered. The residue (silica) was washed with a small volume
of hot 1% H2SO4 followed by water and the volume was made up to the mark with
water. Suitable aliquots of sample solution were analyzed according to the procedure
for chromium. The results are summarized in table 2.3A, 2.3B, 2.3C and 2.3D.
2.5.6 Determination of Chromium in Soil
An air-dried homogenized soil sample (1 g) was weighed accurately and
placed in a 100 mL Kjeldahl flask. The sample was digested and the content of flask
was filtered through a Whatman no. 40 filter paper into a 25 mL calibrated flask and
neutralized with dilute ammonia. It was then diluted to the mark with water.
Appropriate aliquots of 1-2 mL of the solution was transferred in to a 10 mL
calibrated flask and analyzed for chromium content according to the general
-
8/3/2019 Xac Dinh Crpm Trong Nuoc Va Dat
14/37
procedure. They tested negative. To these samples known amounts of chromium(VI)
sample was added and analyzed by the proposed procedure for chromium. The
results are summarized in table 2.2A, 2.2B, 2.2C and 2.2D.
2.5.7 Determination of Chromium in Water Samples
Each filtered environmental water sample (100 mL) was analyzed for
chromium. They tested negative. To these samples known amounts of
chromium(VI) sample was added and analyzed by the proposed procedure for
chromium.
2.5.8 Analysis of Chromium in Pharmaceutical Preparation
Samples of the finely ground multivitamin/multimineral tablet (Chromoplex)containing chromium was treated with 5 mL 2M HNO3, and the mixture was
evaporated to dryness. The residue was leached with 5 mL 0.5 M H 2SO4. The
solution was diluted to a known volume with water, after neutralizing with dilute
ammonia. Suitable aliquots of sample solution were analyzed by the present method
for chromium determination. The results are summarized in table 2.4A, 2.4B, 2.4C
and 2.4D.
2.6 RESULTS AND DISCUSSION
2.6.1 Absorption Spectra
2.6.1.1 -naphthol as a reagent
This method is based on the oxidation of 2,4-dinitrophenylhydrazine and
coupling reaction. Chromium(VI) oxidizes 2,4-dinitrophenylhydrazine to its
diazonium salt in an acid medium. The diazonium salt is then coupled with
-naphthol in an alkaline medium, which gives an azo dye with absorption
maximum at 663 nm. Diazotization and coupling reactions are found to be
temperature dependent. Diazotization is carried out at 0-50C and coupling reaction is
carried out at room temperature, above 350C there is a decrease in intensity of the
color. The absorption spectrum of the colored species of an azo dye is presented in
figure II.1A and reaction system is presented in scheme 2.1.
2.6.1.2 Using-naphthol as a reagent
This method is based on the oxidation of 2,4-dinitrophenylhydrazine and
coupling reaction. Chromium(VI) oxidizes 2,4-dinitrophenylhydrazine to its
-
8/3/2019 Xac Dinh Crpm Trong Nuoc Va Dat
15/37
diazonium salt in an acid medium. The diazonium salt is then coupled with
-naphthol in an alkaline medium, which gives an azo dye with absorption
maximum at 503 nm. Diazotization and coupling reactions are found to be
temperature dependent. Diazotization is carried out at 0-50C and coupling reaction is
carried out at room temperature, above 350
there is a decrease in intensity of the
color. The absorption spectrum of the colored species of an azo dye is presented in
figure II.1A and reaction system is presented in scheme 2.1.
2.6.1.3 Using as N-(1-naphthyl)ethylenediamine dihydrochloride as a reagent
This method is based on the oxidation of 2,4-dinitrophenylhydrazine and
coupling reaction. Chromium(VI) oxidizes 2,4-dinitrophenylhydrazine to its
diazonium salt in an acid medium. The diazonium salt is then coupled with N-(1-
naphthyl)ethylenediamine dihydrochloride in an alkaline medium, which gives an
azo dye with absorption maximum at 525 nm. Diazotization and coupling reactions
are found to be temperature dependent. Diazotization is carried out at 0-50C and
coupling reaction is carried out at room temperature, above 350 there is a decrease in
intensity of the color. The absorption spectrum of the colored species of an azo dye
is presented in figure II.1B and reaction system is presented in scheme 2.1.
2.6.1.4 Using pyrocatechol as a reagent
This method is based on the oxidation of 2,4-dinitrophenylhydrazine and
coupling reaction. Chromium(VI) oxidizes 2,4-dinitrophenylhydrazine to its
diazonium salt in an acid medium. The diazonium salt is then coupled with
pyrocatechol in an alkaline medium, which gives an azo dye with absorption
maximum at 619 nm. Diazotization and coupling reactions are found to be
temperature dependent. Diazotization is carried out at 0-50C and coupling reaction is
carried out at room temperature, above 350C there is a decrease in intensity of the
color. The absorption spectrum of the colored species of azo dye is presented in
figure II.1B and reaction system is presented in scheme 2.1.
2.6.2 Effect of Reagent Concentration
A volume of 1 mL of 1% 2,4-dinitrophenylhydrazine solution was required
for maximum absorbance and it was found that, addition of 1 mL-naphthol
(1%) or 1 mL-naphthol (1%) or 1 mL of NEDA (1%) or 1 mL of pyrocatechol
(1%) reagents provides maximum absorbance. Larger excess of reagent produced no
-
8/3/2019 Xac Dinh Crpm Trong Nuoc Va Dat
16/37
further increase in the absorbance. Oxidation of 2,4-dinitrophenylhydrazine by
chromium is most effective in acidic medium. The reaction is studied using excess
2,4-dinitrophenylhydrazine and varying quantities of HCl. The reaction is allowed to
-naphthol (1%)
-naphthol (1%) or NEDA (1%) or pyrocatechol (1%) in an alkaline medium.
Absorbance of the azo dyestuff is then measured at 663 nm or 503 nm or 525 nm or
619 nm against reagent blank. It was found that absorbance at 663 nm or 503 nm or
525 nm or 619 nm was maximum. When concentration of HCl during the oxidation
reaction is greater than 2M and further increase in acid concentration does not affect
the absorbance.
2.6.3 Analytical Data
2.6.3.1 Using -naphthol as a reagent
In this method adherence to Beers law is studied by measuring the
absorbance values of solutions varying chromium concentration. A straight line
graph is obtained by plotting absorbance against concentration of chromium. Beers
law is obeyed in the concentration range 0.024.0 gmL of chromium. Adherence
to Beers law graph for the determination of chromium using -naphthol is presented
in figure II.2A. The molar absorptivity and Sandells sensitivity of the method are
found to be 1.2x104
L mol-1
cm-1
and 4.3x10-3
gcm. The detection limit
(DLL=1
the regent blank (n=5) and S is the slope of the calibration curve) of the chromium
determination are found to be 0.752 gmLand 2.280 gmLrespectively.
2.6.3.2 Using -naphthol as a reagent
In this method adherence to Beers law is studied by measuring the
absorbance values of solutions varying chromium concentration. A straight line
graph is obtained by plotting absorbance against concentration of chromium. Beers
law is obeyed in the concentration range 0.059.0 gmL
of chromium. Adherence
to Beers law graph for the determination of chromium using -naphthol is presented
in figure II.2B. The molar absorptivity and Sandells sensitivity of the method are
found to be 3.44x104
L mol-1
cm-1
and 1.51x10-3
gcm. The detection limit
(DLL
-
8/3/2019 Xac Dinh Crpm Trong Nuoc Va Dat
17/37
the regent blank (n=5) and S is the slope of the calibration curve) of the chromium
determination are found to be 0.616 gmLand 1.866 gmLrespectively.
2.6.3.3 Using pyrocatechol as a reagent
In this method adherence to Beers law is studied by measuring the
absorbance values of solutions varying chromium concentration. A straight line
graph is obtained by plotting absorbance against concentration of chromium. Beers
law is obeyed in the concentration range 0.16.0 gmL of chromium. Adherence
to Beers law graph for the determination of chromium using pyrocatechol is
presented in figure II.2C. The molar absorptivity and Sandells sensitivity of the
method are found to be 1.96x104 L mol-1 cm-1 and 2.6x10-3 gcm. The detection
limit (DL=3.3 L=10
deviation of the regent blank (n=5) and S is the slope of the calibration curve) of
the chromium determination are found to be 0.332 gmL
and 1.008 gmL
respectively.
2.6.3.4 Using N-(1-naphthyl)ethylenediamine dihydrochloride as a reagent
In this method adherence to Beers law is studied by measuring the
absorbance values of solutions varying chromium concentration. A straight line
graph is obtained by plotting absorbance against concentration of chromium. Beers
law is obeyed in the concentration range 0.014.0 gmL
of chromium. Adherence
to Beers law graph for the determination of chromium using N-(1-
naphthyl)ethylenediamine dihydrochloride is presented in figure II.2D. The molar
absorptivity and Sandells sensitivity of the method is found to be 1.56x104
L mol-1
cm-1
and 3.3x10-3
gcm, The detection limit (DL
limit (QL
S is the slope of the calibration curve) of the chromium determination are found to
be 0.252 gmL
and 0.765 gmL
respectively.
2.6.4 Effect of Divers Ions
The effect of various non-target species on the determination of chromium
was investigated. The tolerance limits of interfering species are established at those
concentrations that do not cause more than 2% error in absorbance values with
fixed concentration of chromium. The present method is based on the oxidation of
DNPH with chromium then coupled with coupling reagents. Therefore, strong
-
8/3/2019 Xac Dinh Crpm Trong Nuoc Va Dat
18/37
oxidizing or reducing species are expected to interfere. The results indicated that
Ce(IV) and Hg(II) showed severe interference. However, the tolerance level of these
ions may be increased by the addition of 2 mL of 2% EDTA. The results are given
in table 2.5A, 2.5B, 2.5C and 2.5D.
2.7 APPLICATIONS
The developed method is applied to the quantitative determinations of traces
of chromium in different samples such as alloys, pharmaceutical preparations,
natural water and soil samples. Statistical analysis of the results by t- and F- tests
show that, there is no significant difference in accuracy and precision of the
proposed and reference method [57]. The precision of the proposed method is
evaluated by replicate analysis of samples containing chromium at different
concentration.
2.8 CONCLUSIONS
1. The reagents provide a simple and sensitive method for the
spectrophotometric determination of chromium.
2. The reagents have the advantage of high sensitivity and low absorbance of
reagent blank.
3. The developed method does not involve any stringent reaction conditions
and offers the advantages of color stability over 5 hours.
4. The statistical analysis of the results by t- and F- tests show that, there is no
significant difference in accuracy and precision between the proposed
method and reference method.
5. The proposed method successfully applied for the determination of
chromium(VI) in pharmaceutical, steel and environmental samples.
-
8/3/2019 Xac Dinh Crpm Trong Nuoc Va Dat
19/37
TABLE 2.1: COMPARISON OF SPECTROPHOTOMETRIC METHODS FOR
THE DETERMINATION OF CHROMIUM(VI) WITH PROPOSED METHOD
ReagentMolar
Absorptivity
(L mol-1
cm-1
)
Remarks
1. Variamine blue [57] 8.12 x 103
Low sensitive
2. Citrazinic Acid [72] 2.12 x 104
Less stable less detection limit
3. Chitin [37] 3.50 x 104
Require solvents for the extraction
4. Trifluoperazine-
hydrochloride [70]
2.08 x 104 Color is stable only 2 h and less
detection limit
5. Cyclam [44] 1.50 x 104 Low detection limit not applicable to
lower concentration (0.220 mgL-1
)
6. 4-(2-Thiazolylazo)-
resorcinol [45]
2.73 x 104 N-Cetyl-,N,Ntrimethylammonium
bromide is required for the reaction
7. Perphenazine [42] 1.87 x 104
Color is stable up to 30 min only
Proposed Reagents
DNPH --naphthol
DNPH --naphthol
1.20 x 104
3.44 x 104
Color is stable up to 5 hours, less
interference, facile, sensitive, rapid
and non extractive
-
8/3/2019 Xac Dinh Crpm Trong Nuoc Va Dat
20/37
TABLE 2.2A: DETERMINATION OF CHROMIUM IN NATURAL WATER
AND SOIL SAMPLE USING DNPH--NAPHTHOL REAGENTS
Proposed method Reference method [57]
Sample
Cr(VI)
added
-1
Cr(VI)
found in
-1SDa
Recovery
%
Cr(VI)
found in
-1 SDa
Recovery
%
t-testb F-testc
Natural
water
1.0
2.0
3.0
0.96 0.05
1.96 0.05
2.95 0.06
96.00
98.00
98.33
0.95 0.05
1.97 0.06
2.97 0.06
95.00
98.50
99.00
1.78
1.78
1.78
1.04
1.04
1.04
Soil
1.0
2.0
3.0
0.99 0.04
1.99 0.04
2.98 0.06
99.00
99.50
99.33
0.99 0.04
1.99 0.04
2.98 0.04
99.00
99.50
99.33
0.60
0.51
0.78
1.16
1. 09
2.03
aMeanStandard deviation (n = 5)
bTabulated t-value for 8 degrees of freedom at P(0.95) is 2.65
c
Tabulated F-value for (4, 4) degrees of freedom at P (0.95) is 5.72.
-
8/3/2019 Xac Dinh Crpm Trong Nuoc Va Dat
21/37
TABLE 2.2B: DETERMINATION OF CHROMIUM IN NATURAL WATER
AND SOIL SAMPLE USING DNPH --NAPHTHOL REAGENTS
Proposed method Reference method [57]
Sample
Cr(VI)
added
-1
Cr(VI)
found in
-1 SDa
Recovery
%
Cr(VI)
found in
-1 SDa
Recovery
%
t-testb F-testc
Natural
water
1.0
2.0
3.0
0.99 0.025
1.98 0.028
2.99 0.036
99.00
99.00
99.66
0.95 0.05
1.97 0.06
2.97 0.06
95.00
98.50
99.00
1.78
1.78
1.78
1.04
1.04
1.04
Soil
1.0
2.0
3.0
0.98 0.028
1.99 0.030
2.99 0.035
98.00
99.50
99.66
0.99 0.04
1.99 0.04
2.98 0.04
99.00
99.50
99.33
0.60
0.51
0.78
1.16
1. 09
2.03
aMeanStandard deviation (n = 5)
bTabulated t-value for 8 degrees of freedom at P(0.95) is 2.65
c Tabulated F-value for (4, 4) degrees of freedom at P (0.95) is 5.72.
-
8/3/2019 Xac Dinh Crpm Trong Nuoc Va Dat
22/37
TABLE 2.2C: DETERMINATION OF CHROMIUM IN NATURAL WATER
AND SOIL SAMPLE USING DNPH- PYROCATECHOL REAGENTS
Proposed method Reference method [57]
Sample
Cr(VI)
added
-1
Cr(VI)
found in
-1SDa
Recovery
%
Cr(VI)
found in
-1 SDa
Recovery
%
t-testb F-testc
Natural
water
1.0
2.0
3.0
1.02 0.02
2.01 0.04
2.99 0.03
102.00
100.50
99.66
0.95 0.05
1.97 0.06
2.97 0.06
95.00
98.50
99.00
2.23
0.27
0.79
2.32
2.25
1.77
Soil
1.0
2.0
3.0
0.99 0.03
1.98 0.02
2.98 0.03
99.00
99.00
99.33
0.99 0.04
1.99 0.04
2.98 0.04
99.00
99.50
99.33
0.79
2.23
1.49
1.77
2.23
2.10
aMeanStandard deviation (n = 5)
bTabulated t-value for 8 degrees of freedom at P(0.95) is 2.65
c Tabulated F-value for (4, 4) degrees of freedom at P (0.95) is 5.72.
-
8/3/2019 Xac Dinh Crpm Trong Nuoc Va Dat
23/37
TABLE 2.2D: DETERMINATION OF CHROMIUM IN NATURAL WATER
AND SOIL SAMPLE USING DNPH- NEDA REAGENTS
Proposed method Reference method [57]
Sample
Cr(VI)
added
-1
Cr(VI)
found in
-1SDa
Recovery
%
Cr(VI)
found in
-1 SDa
Recovery
%
t-testb F-testc
Natural
water
1.0
2.0
3.0
0.99 0.02
1.99 0.02
2.99 0.03
99.00
99.50
99.66
0.95 0.05
1.97 0.06
2.97 0.06
95.00
98.50
99.00
1.06
1.01
0.79
1.53
1.39
1.36
Soil
1.0
2.0
3.0
0.98 0.02
2.01 0.03
2.99 0.04
98.00
100.5
99.66
0.99 0.04
1.99 0.04
2.98 0.04
99.00
99.50
99.33
2.23
0.65
0.57
2.04
1. 37
1.69
aMeanStandard deviation (n = 5)
bTabulated t-value for 8 degrees of freedom at P(0.95) is 2.65
c Tabulated F-value for (4, 4) degrees of freedom at P (0.95) is 5.72.
-
8/3/2019 Xac Dinh Crpm Trong Nuoc Va Dat
24/37
TABLE 2.3A: DETERMINATION OF CHROMIUM IN ALLOY USING DNPH -
-NAPHTHOL REAGENTS
Sample
Chromium
certified
in %
Amount of
chromium
found SDa
Recovery
%t-test
bF-test
c
GKW Steel, India
(0.05g/100mL); C 0.54,
Mn 0.89, S 0.018, P
0.034, Si 0.33, V 0.13
1.02 1.01 0.04 99.01 0.57 1.05
aMeanStandard deviation (n = 5)
b Tabulated t-value for 4 degrees of freedom at P(0.95) is 2.78
cTabulated F- value for (4,4) degree of freedom at 95% probability level is 6.39;
TABLE 2.3B: DETERMINATION OF CHROMIUM IN ALLOY USING DNPH -
-NAPHTHOL REAGENTS
Sample
Chromium
certified in
%
Amount of
chromium
found SDa
Recovery
%t-test
bF-test
c
GKW Steel, India
(0.05g/100mL); C 0.54,
Mn 0.89, S 0.018, P
0.034, Si 0.33, V 0.13
1.02 1.01 0.034 99.01 0.65 1.00
aMeanStandard deviation (n = 5)
bTabulated t-value for 4 degrees of freedom at P(0.95) is 2.78
cTabulated F- value for (4,4) degree of freedom at 95% probability level is 6.39;
-
8/3/2019 Xac Dinh Crpm Trong Nuoc Va Dat
25/37
TABLE 2.3C: DETERMINATION OF CHROMIUM IN ALLOY USING DNPH-
PYROCATECHOL REAGENTS
Sample
Chromium
certified
in %
Amount of
chromium
found SDa
Recovery%
t-testb
F-testc
GKW Steel, India
(0.05g/100mL); C 0.54,
Mn 0.89, S 0.018, P
0.034, Si 0.33, V 0.13
1.02 1.01 0.03 99.01 0.29 2.25
a MeanStandard deviation (n = 5)b
Tabulated t-value for 4 degrees of freedom at P(0.95) is 2.78
cTabulated F- value for (4,4) degree of freedom at 95% probability level is 6.39;
TABLE 2.3D: DETERMINATION OF CHROMIUM IN ALLOY USING DNPH-
NEDA REAGENTS
Sample
Chromium
certified
in %
Amount of
chromium
found SDa
Recovery
%t-test
bF-test
c
GKW Steel, India
(0.05g/100mL); C 0.54,
Mn 0.89, S 0.018, P
0.034, Si 0.33, V 0.13
1.02 1.01 0.03 99.01 0.82 1.82
aMeanStandard deviation (n = 5)
b Tabulated t-value for 4 degrees of freedom at P(0.95) is 2.78
cTabulated F- value for (4,4) degree of freedom at 95% probability level is 6.39;
-
8/3/2019 Xac Dinh Crpm Trong Nuoc Va Dat
26/37
TABLE 2.4A: DETERMINATION OF CHROMIUM IN PHAMACEUTICAL
PREPARATION USING DNPH- -NAPHTHOL REAGENTS
SampleChromium
certified
Chromium
found SDa
Recovery
%t-test
bF-test
c
Chromoplex 0.200 0.198 0.02 99.00 1.86 1.17
aMeanStandard deviation (n = 5) [mg/tablet]
bTabulated t-value for 4 degrees of freedom at P(0.95) is 2.78
cTabulated F- value for (4,4) degree of freedom at 95% probability level is 6.39;
TABLE 2.4B: DETERMINATION OF CHROMIUM IN PHAMACEUTICAL
PREPARATION USING DNPH - -NAPHTHOL REAGENTS
SampleChromium
certified
Chromium
found SDa
Recovery
%t-test
bF-test
c
Chromoplex 0.200 0.198 0.03 99.00 1.78 1.04
aMeanStandard deviation (n = 5) [mg/tablet]
bTabulated t-value for 4 degrees of freedom at P (0.95) is 2.78
cTabulated F- value for (4,4) degree of freedom at 95% probability level is 6.39;
-
8/3/2019 Xac Dinh Crpm Trong Nuoc Va Dat
27/37
TABLE 2.4C: DETERMINATION OF CHROMIUM IN PHAMACEUTICAL
PREPARATION USING DNPH-PYROCATECHOL REAGENTS
Sample Chromium
certified
Chromium
found SDa
Recovery
%
t-testb F-testc
Chromoplex 0.200 0.199 0.03 99.50 0.82 2.19
aMeanStandard deviation (n = 5) [mg/tablet]
bTabulated t-value for 4 degrees of freedom at P (0.95) is 2.78
cTabulated F- value for (4,4) degree of freedom at 95% probability level is 6.39;
TABLE 2.4D: DETERMINATION OF CHROMIUM IN PHAMACEUTICAL
PREPARATION USING DNPH- NEDA REAGENTS
Sample Chromium
certified
Chromium
found SDa
Recovery
%
t-testb
F-testc
Chromoplex 0.200 0.200 0.04 100.00 0.55 1.00
aMeanStandard deviation (n = 5) [mg/tablet]
bTabulated t-value for 4 degrees of freedom at P (0.95) is 2.78
cTabulated F- value for (4,4) degree of freedom at 95% probability level is 6.39;
-
8/3/2019 Xac Dinh Crpm Trong Nuoc Va Dat
28/37
TABLE 2.5A: EFFECT OF DIVERSE IONS ON THE DETERMINATION OF
CHROMIUM (2 gmL) USING DNPH- -NAPHTHOL REAGENTS
Diverseions
Tolerance
limit
(gmL)
Diverseions
Tolerancelimit(gmL)
Diverseions
Tolerance
limit
(gmL)
Na+
CHCOO
K+
BO33
Mg2+
Ca
2+
Mn2+
Ni2+
3000
3000
3000
3000
200
200200
200
citrate
oxalate
tartarate
Al3+
Cd2+
Ba
2+
Co2+
Zn2+
500
500
500
500
500
500500
500
Cu2+
*
Ce4+*
Fe3+
*
Sn2+
*
Pb2+*
Hg
2+
*W
6+*
Mo6+
*
25
25
25
25
25
2525
25
* Masked by masking agent
TABLE 2.5B: EFFECT OF DIVERSE IONS ON THE DETERMINATION OF
CHROMIUM (3 gmL) USING DNPH - -NAPHTHOL REAGENTS
Diverse
ions
Tolerance
limit(gmL
)
Diverse
ions
Tolerance
limit(gmL
)
Diverse
ions
Tolerance
limit(gmL
)
K+
BO33
Na+
CHCOO
tartarate
citrate
oxalate
Ba2+
2500
2500
2500
2500
2500
2500
2500
500
Co2+
Zn2+
Al3+
Cd2+
Mn2+
Ni2+
Mg2+
Ca2+
500
500
100
100
100
100
100
100
Sn2+*
Pb2+
*
W6+
*
Mo6+
*
Hg2+*
Cu2+
*
Ce4+
*
Fe3+
*
50
50
50
50
50
50
50
50
* Masked by masking agent
-
8/3/2019 Xac Dinh Crpm Trong Nuoc Va Dat
29/37
TABLE 2.5C: EFFECT OF DIVERSE IONS ON THE DETERMINATION OF
CHROMIUM (3 gmL) USING DNPH-PYROCATECHOL REAGENTS
Diverse
ions
Tolerance
Limit(gmL)
Diverse
ions
Tolerance
limit(gmL)
Diverse
ions
Tolerance
limit(gmL)
Na+
K+
CHCOO
Citrate
Oxalate
Tartarate
BO33
Al3+
> 3000
> 3000
> 3000
> 3000
> 3000
2500
1000500
Cd2+
Ba2+
Co2+
Zn2+
Mg2+
Ca2+
Mn
2+
Ni2+
500
500
500
500
300
300
300300
Sn2+
*
Pb2+
*
Fe3+
*
W6+
*
Mo6+
*
Cu2+
*
Ce
4+
*Hg
2+*
50
50
50
50
50
20
2050
* Masked by masking agent
TABLE 2.5D: EFFECT OF DIVERSE IONS ON THE DETERMINATION OF
CHROMIUM (2 gmL) USING DNPH-NEDA REAGENTS
Diverse
ions
Tolerance
limit(gmL
)
Diverse
ions
Tolerance
limit(gmL
)
Diverse
ions
Tolerance
limit(gmL
)
Na+
K+
CHCOO
citrate
oxalate
tartarate
BO33
> 3000
> 3000
> 3000
> 3000
> 3000
> 3000
2000
SO42
Al3+
Cd2+
Ba2+
Co2+
Zn2+
Mg2+
1000
800
800
800
500
500
200
Ca2+
Mn2+
Ni2+
Cu2+
*
Ce
4+
*Hg
2+*
200
200
200
25
2525
* Masked by masking agent
-
8/3/2019 Xac Dinh Crpm Trong Nuoc Va Dat
30/37
FIGURE II.1A: ABSORPTION SPECTRA OF AZO DYES: DNPH-
-NAPHTHOL COUPLE VS REAGENT BLANK (a), DNPH- -NAPHTHOL
COUPLE VS REAGENT BLANK (b) AND REAGENT BLANK VS DISTILLED
WATER (c)
FIGURE II.1B: ABSORPTION SPECTRA OF AZO DYES: DNPH- NEDA VS
REAGENT BLANK (a), DNPH- PYROCATECHOL COUPLE VS REAGENT
BLANK (b) AND VS REAGENT BLANK VS DISTILLED WATER (c)
-
8/3/2019 Xac Dinh Crpm Trong Nuoc Va Dat
31/37
FIGURE II.2A: ADHERENCE TO BEERS LAW FOR THE DETERMINATION
OF CHROMIUM USING DNPH--NAPHTHOL REAGENTS
FIGURE II.2B: ADHERENCE TO BEERS LAW FOR THE DETERMINATION
OF CHROMIUM USING DNPH--NAPHTHOL REAGENTS
-
8/3/2019 Xac Dinh Crpm Trong Nuoc Va Dat
32/37
FIGURE II.2C: ADHERENCE TO BEERS LAW FOR THE DETERMINATION
OF CHROMIUM USING DNPH- PYROCATECHOL REAGENTS
FIGURE II.2D: ADHERENCE TO BEERS LAW FOR THE DETERMINATION
OF CHROMIUM USING DNPH- NEDA REAGENTS
-
8/3/2019 Xac Dinh Crpm Trong Nuoc Va Dat
33/37
REACTION SCHEMES 2.1
O2NNH
NH 2
NO 2
+ Cr2O 72- O2N N
+
N
NO 2
+ Cr(III) + H 2O
O2NN
+
N
NO 2
+
OHOH -
O2N
N
N
NO 2
OH
O2NN
+
N
NO 2OH O2N
N
N
NO 2
OH
+
OH -
ClHCl
-
Cl-
Cl-
O 2N N+
N
NO 2
+NH
NH 2
O H -
O2N N+
N
NO 2OH
OH
O2N
N
N
NO 2
OH
OH+
O H -
O 2N
N
N
NO 2
NH
NH 2
Cl-
Cl-
2HCl
-
8/3/2019 Xac Dinh Crpm Trong Nuoc Va Dat
34/37
2.9 REFERENCES
1. M. J. Udy, History of Chromium, Reinhold, New York, (1956).
2. R. Chadwick, New Extraction Processes for Metals, Oxford University
Press, London. (1958).
3. F. E. Bacon, Chromium and Chromium Alloys, p. 451; W. H. Hartford and
R. L. Copson, Chromium Compounds, p. 473; Encyclopedia of Chemical
Technology, Interscience, New York, 2nd Edn., (1964).
4. V. Bencko,J. Hyg. Epidemiol Microbiol Immunol, 29 (1985) 37.
5. M.D. Cohen, B. Kargacin, C.B. Klein and M. Costa. Crit. Rev. Toxicol, 23
(1993) 255.
6. L. Teleky,Dtsch. Med. Wochenschr, 62 (1936) 1353.
7. S. Langard and T. Vigander,Br. J. Ind. Med., 40 (1983) 71.
8. K. Satoh, Y. Fukuda, K. Torii, M. Eng and N. Katsuno, J. Occup. Med., 23
(1981) 835.
9. E. Lindberg and G. Hedenstierna.Arch. Environ. Health, 38 (1983) 367.
10. A. A. Fisher. Cutis, 18 (1976) 21.
11. M. C. Udy, Physical Properties of Chromium, its Alloys and Metallurgical
use in Chromium, Reinhold, New York. (1956).
12. W. Mertz and K. Schwarz,Arch. Biochem. Biophys., 58 (1955) 504.
13. W. Mertz, Physiol. Reviews, 49 (1969) 163.
14. Agency for Toxic Substances and Disease Control. ATSDRs Toxicological
Profiles: Chromium. Boca Raton, Florida: Lewis Publishers, CRC Press, Inc.,
(1997).
15. A. Zhitkovich, V. Voitkun and M. Costa,Biochem., 35 (1996) 7275.
16. W. Mertz,Nutr. Rev., 33 (1975) 129.
17. R. H. Rosen and S. Freeman, Contact Dermatitis, 29 (1993) 88.
18. J. Vertick, and R. Cornelis,Anal. Chim. Acta, 116 (1980) 217.
19. J.M. Eckert, R.J. Judd, P.A. Lay and A.D. Symons, Anal. Chim. Acta, 255
(1991) 31.
20. M. Kamburova, Talanta, 40 (1993) 713.
21. S. Harita, Y. Umezaki and M. Ikeda,Anal. Chem, 58 (1986) 2602.
-
8/3/2019 Xac Dinh Crpm Trong Nuoc Va Dat
35/37
22. R. R. Greenberg, R. Zeisler, H. M. Kingston and T.M. Sullivan, Fresenius J.
Anal. Chem., 332 (1988) 652.
23. R. E. Shaffer, J. O. Cross, S. L. Rose-Pehrsson and W. T. Elam, Anal. Chim.
Acta, 442 (2001) 295.
24. C. M. Davidson, R. P. Thomas, S. E. McVey, R. Perala, D. Littlejohn and
A. M. Ure,Anal. Chim. Acta, 291 (1994) 277.
25. G. H. Jeffery, J. Bassett, J. Mendham, and R. C. Denney, A. I. Vogel, A
Textbook of Quantitative Inorganic Analysis, 5th
Edn., Longmans, (1989).
26. Q. Wei, C. Duan, J. Wang, H. Ma and B. Du, Annali di Chimica, 96 (2006)
451.
27. M. Kaneko, M. Kurihara, S. Nakano and T. Kawashima, Anal. Chim. Acta,
474 (2002) 167.
28. Y. Luo, S. Nakano, D.A. Holman, J. Ruzicka and G.D. Christian, Talanta 44
(1997) 1563.
29. W. Jianya and X. Bin,Anal. Sci., 22 (2006) 1233.
30. Y. Xiang, L. Mei, N. Li and A. Tong,Anal. Chim. Acta, 581 (2007) 132.
31. U. Divrikli, M. Soylak and L. Elci, Environ. Monit. Assess., 138 (2008) 167.
32. H. J. Cahnmann and B. Ruth,Anal. Chem., 24 (1952) 1341.
33. D. O. Miller. Dwight and J. H. Yoe, Clin. Chim. Acta, 4 (1959) 378.
34. K. Motojima and H. Hashitani,Anal. Chem., 33 (1961) 239.
35. N. Todorovska, I. Karadjova, S. Arpadjan and T. Stafilov, Cent. Eur. J. Chem.,
5 (2007) 230.
36. R. M. Cespon and M.C. Yebra,Microchim. Acta, (2008) DOI 10.1007/s00604-
007-0916-7.
37. S. Hoshi, K. Konuma, K. Sugawara, M. Uto and K. Akatsuk, Talanta, 47
(1998) 659.
38. H. D. Revanasiddappa and T. N. Kiran Kumar, Talanta 60 (2003) 1.
39. B. Narayana and T. Cherian,J. Braz. Chem. Soc., 16 (2005) 197.
40. B. Narayana and T. Cherian, Oxid. Commun., 28 (2005) 923.
41. K. L. Cheng, Talanta, 14 (1967) 875.
42. A. A. Mohamed and M. F. El-Shahat,Anal. Sci., 16 (2000) 151.
-
8/3/2019 Xac Dinh Crpm Trong Nuoc Va Dat
36/37
43. K. Girish Kumar and R. Muthuselvi,J. Anal. Chem., 61 (2006) 28.
44. M. A. Zaitoun,Intern. J. Environ. Anal. Chem. 85 (2005) 399.
45. L. S. de Carvalho, A. C. S. Costa, S. L. C. Ferreira and L. S. G. Teixeira, J.
Braz. Chem. Soc., 15 (2004) 153.
46. G. den-Boef and B. C. Poeder,Anal. Chim. Acta, 30 (1964) 261.
47. U. Katsuya and K. Yukiteru,Bull. Chem. Soc. Japan, 38 (1965) 2010.
48. E. Jacobsen and W. Lund,Anal. Chim. Acta, 36 (1966) 135.
49. J. R. Johnston and W. J. Holland,Microchim. Acta, 60 (1972) 321.
50. T. Yotsuyanagi, Y. Takeda, R. Yamashita and K. Aomura, Anal. Chim. Acta,
67 (1973) 297.
51. H. S. Gowda and J. B. Raj,J. Indian Chem. Soc., 59 (1982) 1398.
52. G. H. Rizvi, B. P. Gupta and R. P. Singh,Microchim. Acta, 60 (1972) 459.
53. R. K Hussain and R. D. Venkata,Analyst, 108 (1983) 1247.
54. P. Nagaraj, N. Aradhana, A. Shivakumar, A. K. Shrestha and A. Gowda,
Environ.Monit. and Assess., (2008) DOI: 10.1007/s10661-008-0557-2
55. P. Ram, B. Reeta, K. Ajit and S. K. Rehani, Talanta, 38 (1991) 1163.
56. D. T. Burns, M. Harriott and S. A. Barakat,Anal. Chem. Acta, 259 (1992) 33.
57. F. A. S. Fabiyi, and A. Z. Donnio, Synth. Reactivity Inorg. Met-Org. Nano-
Met. Chem., 37 (2007) 809.
58. M. Kamburova, Talanta, 40 (1993) 707.
59. M. Kamburova, Talanta, 40 (1993) 713.
60. M. Kamburova, Chem. Anal, (Warsaw), 38 (1993) 189.
61. S. Yoshiaki, T. Shoji, M. Yoshiko and N. Hiroaki,Anal Sci., 10 (1994) 71.
62. S. P. Arya and B. Anvita, Fresenious J. Anal. Chem., 348 (1994) 772.
63. J. B. Raj and H. S. Gowda,Analyst, 120 (1995) 1815.
64. A. Rosa, M. Hector and O. Roberto,Anal. Sci., 11 (1995) 431.
65. V. Maheswari and N. Balasubramanian, Chem. Anal., (Warsaw), 41 (1996)
569.
66. S. Ressalan, R. S. Chauhan, A. K.Goswami and D. N. Purohit,Asian J. Chem.,
10 (1998) 1004.
-
8/3/2019 Xac Dinh Crpm Trong Nuoc Va Dat
37/37
67. S. Ressalan, R. S. Chauhan, A. K.Goswami and D. N. Purohit, Oriental J.
Chem., 14 (1998) 345.
68. M. B. Melwanki and J. Seetharamappa, Indian J. Environ. Protection, 20
(2000) 801.
69. M. B. Melwanki and J. Seetharamappa,Indian J. Chem., 40A (2001) 659.
70. H. D. Revanasiddappa and T. N. Kiran Kumar, Chem. Anal. (Warsaw), 47
(2002) 311.
71. L. M. Lourenco, F. G. Martins, V. R. Balbo, A. C. Pimenta, J. R. M. Castro
and J. F. Andrade,Ecl. Quim., 31 (2006) 31.
72. H. D. Revanasiddappa and T. N. Kiran Kumar, J. Anal. Chem., 56 (2001)
1084.
73. T. Cherian and B Narayana,Indian J. Chem. Tech., 12 (2005) 596.
74. P. K. Tarafder, S. B. Singh and D. P. S, Rathore, Fresenius' J. Anal. Chem.,
354 (1996) 124.