5.1 a sensitive derivative spectrophotometric method for the determination of zineb...

142

5.1 A sensitive Derivative Spectrophotometric method for the

Determination of Zineb (Zinc ethylenebisdithiocarbamate)

fungicide using Sodium Molybdate

5.1.1 Introduction

Zineb is a light colored ethylenebisdithiocarbamate (EBDC) fungicide used to prevent

crop damage in the field and to protect the harvested crops from deterioration during

storage or transport. It is a non-systemic (surface acting) fungicide, commercially

available as wettable powder, dust formulations and also in mixture with other fungicides

under the trade names like Dithane Z-78, Amitan, etc, Like other EBDCs, it also shows

strong metal binding properties [1, 2] and hence is capable of blocking enzymes and

affecting the biological systems. Even the breakdown products of zineb viz.

ehtylenethiourea (ETU) and ethylene thiuram monosulfide are quite harmful. The US

EPA has classified ETU as a probable human carcinogen. Hence, the residues of Zineb in

food and fodder are harmful and these can also pass through soil and leach into the

ground water.

Figure 5.1.1: Structure of Zineb

Many methods like spectrophotometric [1,3-8], flame absorption spectrometry [9,10],

FTIR [11], gas chromatography [12,13], HPLC [14-16], polarographic [17,18], biosensor

[19] and enzyme linked immuno sorbent assay [20] are available for the determination of

143

Zineb and other dithiocarbamates.

Most of the applied methods are using different techniques like spectrophotometry and

gas chromatography [3] based on analysis of CS2, H2S or amines which are evolved by

the decomposition of EBDCs. Dithiocarbamates have been determined in vegetables and

food stuffs using HPLC

[21], extraction voltammetry [22] and titrimetry [23].

Dithiocarbamates (DTCs) can also be determined by methods, like iodometry [24, 25]

and indirect complexometry [26], etc. But the methods discussed above have various

disadvantages like:

1. Methods other then gas chromatography are indirect, time consuming and less

sensitive.

2. Gas chromatographic methods are sensitive but suffer from lack of the selectivity

since all dithiocarbamate pesticides evolve carbon disulphide on acid hydrolysis.

Moreover, the dithiocarbamate decompositions are strongly dependent on

temperature and on individual dithiocarbamates. The evolution of CS2 requires

more than two hours for the decomposition of dithiocarbamate

3. HPLC methods are expensive as these involve the use of the toxic and expensive

solvents.

DTCs are also determined using FTIR spectrometry but the method is less sensitive and

time consuming [27]. Here, a relatively fast, simple, sensitive and selective derivative

spectrophotometric method is presented for the analysis of Zineb by converting it into

molybdenum complex. Zineb reacts with sodium molybdate on heating to form a blue

colored complex. Zineb and sodium molybdate combine in the ratio 1:2 to form complex.

Zineb releases Zn2+

and dithiocarbamate unit, the latter forms complex with sodium

molybdate which is then extracted into methyl isobutyl ketone (MIBK) and determined

144

by derivative spectrophotometry. The significant advantage of this method over the gas

chromatographic methods is that it can be applied for the direct determination of Zineb in

the presence of other dithiocarbamates like Ziram, Thiram and Ferbam.

5.1.2 Experimental

5.1.2.1 Equipment and Reagents

Elico SL-164, Double Beam UV-Vis spectrophotometer was used. Zineb standard was

obtained from Riedel de Haën, Germany. A stock solution was prepared by dissolving

100 mg of Zineb in 100 mL of 0.1M NaOH. Further dilutions were carried out with 0.1M

NaOH as required. A 2% (W/V) solution of sodium molybdate was prepared in doubly

distilled water.

5.1.3 Procedure

5.1.3.1 Absorption spectra

To an aliquot containing 100 g of Zineb were added 2 mL of 2% sodium molybdate

solution and 1 mL of 2 M H2SO4. The mixture was boiled for 5 minutes, cooled and

water was added to make the volume 5 mL. The blue complex formed was extracted into

5 mL of MIBK (methyl isobutyl ketone) with shaking. The organic layer was collected

into a test tube containing fused CaCl2 to remove any moisture. The solution was then

decanted into a 1 cm cell and the spectra were taken against a reagent blank. The

molybdenum complex shows peaks at 670 nm and 956 nm (Figure 5.1.2), but the peak at

956 nm has much higher absorbance; hence all the measurements were made at this

wavelength. The first derivative, second derivative, third derivative and fourth derivative

curves were given in figures 5.1.3-5.1.6 respectively.

145

In DS (Derivative Spectrophotometry), the λ reproducibility and S to N ratio are quite

important. The features like peak height and noise level depend on parameters chosen

like order of derivative; scan speed and integration time during recording of spectra. The

use of optimum parameters will give better resolution and more sensitivity. For the 4th

derivative spectra, Δλ = 9 nm was found to be ideal.

5.1.3.2 Preparation of calibration curve

The known volumes of sample solutions having 10-250 µg of Zineb were analyzed by

general procedure and the derivative spectra were obtained against a reagent blank

prepared under the similar conditions. The characteristics of zero order and derivative

spectra are summarized in Tables 5.1.1 and 5.1.2, respectively.

5.1.4 Results and Discussion

5.1.4.1 Beer’s law and Sensitivity

The optimum wavelength interval was found to be 9 nm for high resolution and

sensitivity. The wavelength range to obtain spectra was selected from 600 nm to 1100

nm. The calibration curve was obtained by measuring the peak height between

wavelength of 850 and 938 nm. Absorbance of sodium molybdate complex with Zineb

recorded against a reagent blank was linear over the concentration range from 2 µg to 40

µg per 5mL of the final solution. The detection limit is 0.006 µg mL-1

for Zineb when

S/N ratio was 3.

5.1.4.2 Effect of heating time

It was observed that the absorbance of the complex increased up to a certain extent on

146

increasing heating time. Therefore, the reaction mixture was heated for different intervals

of time. It was observed that an optimum heating time of 5 minutes was sufficient to

obtain maximum absorbance. Increasing the heating time beyond this did not increase the

absorbance as the complete complexation was achieved by heating for 5 minutes.

5.1.4.3 Effect of acid concentration

Maximum absorbance was observed when volume of acid added was between 1 mL to

1.5 mL. A decrease in absorbance was observed on further increasing the amount of acid

added as higher acid concentration is not conducive for complex formation.

5.1.4.4 Effect of other ions

Sample solutions containing 5 µg mL-1

of Zineb and various amounts of different alkali

metal salts or metal ions were prepared and the general procedure was applied. It was

observed that 20 mg of following foreign anions didn't interfere in the determination of

Zineb: bromide (11 mg), acetate (15 mg), chloride (3.5 mg), fluoride (2 mg), citrate (20

mg) and EDTA (0.06 mg). Of the metal ions examined; Zn(II)(0.066 mg), Mo(IV) (0.14

mg), Ni(II) (0.30 mg), Co(II) (0.009 mg) did not interfere. A 1 mL of 5% NaF solution

was used to mask Fe (II) and Fe (III) ions whereas 2 mL of 5% sodium citrate was used

to mask Hg (II) and Cu (II). Mn (II) was masked using 1.5 mL of 1% potassium bromide

solution.

5.1.4.5 Effect of standing time

It was observed that the absorbance of the solution became constant after 2-3 min so after

extracting into MIBK, a 5 min. standing time was selected. The absorbance of the

complex remained practically constant for about 30 minutes with the R.S.D. values of the

147

absorbance varying between 0.69 to 1.6 % for different concentrations.

5.1.5 Applications

5.1.5.1 Determination of Zineb from fortified samples of wheat grains, cabbage and

rice

The method was applied to the determination of Zineb from fortified samples of wheat

grains, cabbage and rice. 20 grams of the foodstuff was finely crushed and solution

containing a known amount of zineb was added, it was mechanically shaken with 100 mL

of Acetonitrile (ACN) for 1 hour. This mixture was filtered and the residue in funnel was

washed with 3 x 10 mL portions of ACN. The extracts were evaporated on a water bath

(70-90oC). The last traces of solvent were removed using a current of dry air. The Zineb

content in the residue was determined by the general procedure and the results indicated

good recoveries in all cases. The results of the determinations were given in Table 5.1.3.

5.1.5.2 Determination of Zineb in commercial samples

The method was applied for determination of Zineb in a commercial sample Dithane Z 78

and Hexathane 75% W.P. The formulated product sample solutions were prepared as

discussed earlier and determined by the general procedure. The results of the

determinations were given in Table 5.1.4.

5.1.5.3 Simultaneous determination of Zineb in presence of Ziram in synthetic

mixtures

The method was applied for the simultaneous determination of Ziram and Zineb in

synthetic mixtures. Ziram forms a yellow complex with sodium molybdate in cold, which

absorbs at 420 nm [28] whereas Zineb forms complex on heating, all other conditions

148

remaining the same. Synthetic mixtures of zineb and ziram were made in different

proportions. To the binary mixture, 0.15 mL of 2 M H2SO4 and 2 mL of 2% sodium

molybdate were added. Molybdenum-ziram complex was extracted into 5 mL MIBK and

zineb remained in aqueous phase. The absorbance of ziram-molybdenum complex was

measured at 420 nm. To the aqueous phase containing zineb was added 1 mL of 4M

H2SO4 and 2 mL of 2% Na2MoO4 solution. The solution was boiled for 5 minutes, cooled

and extracted into 5 mL MIBK, the spectra of blue complex of zineb was taken between

600 nm and 1100nm. Thus, this method was applied for the simultaneous determination

of ziram and zineb. Ziram was determined from the standard calibration curve [28]. The

results of the determinations are given in Table 5.1.5.

5.1.6 Conclusions

The present method is more sensitive than the carbon disulphide evolution methods. By

this method 0.006 µg mL-1

of Zineb can be determined which is equivalent to 0.0033

µgmL-1

of evolved carbon disulphide. Thus, it is superior to the reported methods and the

direct simultaneous determination of ziram and zineb is possible. The sensitivity of the

present method is comparable to other spectrophotometric methods [Table 5.1.6]. The

selectivity of the present method is superior to other methods. The wide applicability of

this method makes it suitable for dithiocarbamate analysis in foodstuffs and in

commercial samples.

149

Figure 5.1.2: Absorption spectra of molybdenum ehtylenebisdithiocarbamate

complex: Zineb (2 mL) with sodium molybdate (2 %) in presence of H2SO4 (2 M),

extracted into MIBK against a reagent blank.

0.2

0.3

0.4

0.5

0.6

0.7

600 700 800 900 1000 1100

Ab

sorb

an

ce

Wavelength, nm

150

Figure 5.1.3: 1

st derivative curve of molybdenum-

ethylenebisdithiocarbamate complex a, b, c, d representing

the amount of Zineb in final solutions (a: 10 µg mL-1,

b:

100 µg mL-1

, c: 200 µg mL-1

, d: 250 µg mL-1

)

Figure 5.1.4: 2nd

derivative curve of molybdenum-

ethylenebisdithiocarbamate complex a, b, c, d

representing the amount of Zineb in final solutions (a:

50 µg mL-1

, b: 100 µg mL-1

, c: 150 µg mL-1

, d: 200 µg

mL-1

)

-0.015

-0.01

-0.005

4E-17

0.005

0.01

0.015

0.02

600 650 700 750 800 850 900 950 1000

dA

/dλ

Wavelength, nm

d

c

b

a

-0.0021

-0.0016

-0.0011

-0.0006

-0.0001

0.0004

0.0009

625 675 725 775 825 875 925 975

d2A

/dλ

2

Wavelength, nm

a

b

c

d

151

Figure 5.1.5 3rd derivative curve molybdenum-


representing the amount of Zineb in final solutions. (a:

10 µg mL-1

, b: 50 µg mL-1

, c: 100 µg mL-1

, d: 200 µg

mL-1

)

Figure 5.1.6 4th derivative curve molybdenum-


representing the amount of Zineb in final solutions.

(a: 10 µg mL-1

, b: 50 µg mL-1

, c: 100 µg mL-1

, d: 200

µg mL-1

)

-0.0002

-0.0001

-1E-18

1E-04

0.0002

0.0003

600 650 700 750 800 850 900 950

d3A

/dλ

3

wavelength(nm)

d c b

a

-5E-05

-3E-05

-1E-05

1E-05

3E-05

5E-05

7E-05

600 650 700 750 800 850 900 950

d4A

/dλ4

wavelength, nm

d

c

b

a

152

Table 5.1.1: Different parameters of zero order spectra

S.No. Parameter

Zero derivative spectra of Zineb-

Sodium molybdate complex

1. Molar Absorptivity (L mol-1

cm-1

) 1.4 x 104

2. Specific Absorptivity (mL g-1

cm-1

) 35.2

3. Sandell’s Sensitivity (μg mL-1

) 2.84x10-2

4. Analytical Sensitivity (μg mL-1

) 2.80x10-2

5. Linear Range 2 μg mL-1

to 40 µg mL-1

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Table 5.1.2: Comparison of calibration curves of Zineb using different derivative spectra

Zineb

complex

Order of

derivative

λ

nm

Regression

Equation R

2

R.S.D.

(%)

S.D. of

slope S.D. of intercept

Analytical

Sensitivity (µg mL-1

)

1. 1st 852 y = 6E-05x+0.007 0.9997 +1.9 1.01 x10

-6 1.4 x 10

-4 1.20

2. 2nd

907 y = 6E-06x +0.009 0.9937 +1.5 8.16 x 10-8

1.6 x 10-4

0.16

3. 3rd

937 y = 8E-07x+9E-05 0.9992 +1.9 8.16 x10-9

8.16 x 10-7

0.20

4 4th

902 y = 3E-07x-9E-06 0.9994 +1.3 5.03 x 10-9

8.16 x 10-8

0.006

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Table 5.1.3: Analysis of Zineb from fortified samples

Sample Crop

Zineb addeda

(μg)

Zineb

found b(μg)

Recovery

%age and

RSD%

Rangaswamy et al30

method

Zineb found Recovery

%age

Wheat 10

9.7

97.0±2.4

9.6

96.0

15

14.8

98.6±2.3

14.7

98.0

Zineb 20

19.8

99.0±1.9

19.8

99.0

Rice 8

7.8

97.5±2.5

7.6

95.0

10

9.9

99.0±2.3

9.6

96.0

12

11.8

98.3±2.2

11.6

96.6

12

11.8

98.3±2.3

11.7

97.5

14

13.8

98.5±2.4

13.7

97.8

Cabbage

18

18.1

100.5±2.2

17.6 97.8

aAmount of crop: 10 g,

bEach result is mean of five experiments.

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Table 5.1.4: Determination of Zineb in commercial samples

Commercial

Samples

Zineb taken

(μg)

Zineb founda

(μg)

RSD

(%)

Rangaswamy et al30

method

Zineb found Recovery (%)

Dithane Z-78 8

20

7.7

19.9

2.1

2.3

7.6

19.8

95.0

99.0

Hexathane

75% W.P

5

15

4.9

15.1

1.9

2.2

4.7

14.6

94.0

97.3

a Each result is mean of five experiments

Table 5.1.5: Determination of Zineb and Ziram in synthetic mixtures

a Each result is mean of five experiments

Zineb

added

( μg)

Ziram

added

( μg)

Zineb found

(μg)

Ziram found

(μg)

Recovery (%) a

and

RSD (%)

Zineb Ziram

60 40 59.0 39.5 98.3±2.3 98.7±2.7

50 50 49.7 49.0 99.4±2.8 98.0±2.5

30 70 29.5 69.5 98.3±3.1 99.3±2.4

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Table 5.1.6: Comparison of Molar Absorptivity of Zineb determination with earlier

methods

Method Molar absorptivity

(L mol-1

cm-1

)

Remarks Reference

Cupric acetate

N.R.

Low sensitivity, long

tedious procedure

[30]

Molybdenum 0.62x104 Less sensitive [28]

Phenylfluorone + CPBa 6.9x10

4

Selective & sensitive [31]

1-(2-pyridylazo)-2-naphthol 5.06x104 Column pre-

concentration factor is

required

[32]

Molybdenum (at 956 nm) and

derivative spectrophotometry

1.4x104 Improved molar

absorptivity

Present Work

a: Cetylpyridinium bromide

N.R. Not reported

157


Determination of Maneb (Manganese ethylenebis

dithiocarbamate) fungicide using Sodium Molybdate

5.2.1. Introduction

Maneb (manganese ethylenebisdithiocarbamate is a common dithiocarbamate (DTC)

fungicide available as dust and dispersible powder [33]. Maneb is active against a wide

range of bacterial and fungal species, so, it is widely used on vegetable crops, in fields,

orchards and vines, greenhouses, forestry and also for seed treatment [34]. Maneb is not

systemic but rather a protective fungicide. Hence, its residues can be found on the fodder,

fruit and other crops where it is sprayed. Ethylenebisdithiocarbamate (EBDC) fungicides

like maneb have low human toxicity but their degradation to Ethylene thiourea (ETU) is

of great toxicological concern [35, 36, 37] as it is associated with carcinogenic and

teratogenic properties [38]. DTC complexes are toxic and have mutational effect [39].

Rathore et al [40] have studied the mobility of DTC pesticides through soil and this

aspect of their behavior presents severe hazards for the mankind as they can be washed in

to drinking water sources thus entering our food chain. In the wake of above knowledge,

it is imperative that highly sensitive and efficient methods be developed for the residue

analysis of dithiocarbamate pesticides like maneb in various food and environmental

samples. Most of the developed methods like spectrophotometry and gas chromatography

[3] are based on the analysis of CS2, H2S or amines, which are evolved during

decomposition of EBDCs.One of the earliest colorimetric methods for Maneb

determination was developed by Hylin et al [41]. Türker et al devised a flame atomic

absorption spectrometry method for indirect determination of dithiocarbamate fungicides

158

[42]. Crnogorac and Schwack have provided insight into the various methods for the

residue analysis of dithiocarbamate fungicides [43].

Figure 5.2.1 Structure of Maneb

Waseem et al have used a flow-injection method for the analysis of DTC fungicides with

chemiluminescence detection [44]. A microwave assisted extraction method involving

hydrolysis of dithiocarbamates and their analysis in tobacco leaves was developed by

Vryzas et al [45]. A Differential pulse polarographic (DPP) technique has been employed

for the determination of DTC residues by Schwack et al [46]. Lo et al have determined

propineb, zineb, maneb and mancozeb by an HPLC method [47]. Česnik et al have

developed validation for a GC-MS method for the determination of DTCs in foodstuffs

[48]. Cronogorac et al have presented a method using hydrophilic interaction- LC-

Tandem Mass Spectrometry for the determination for DTC fungicide residues in fruit and

vegetables [49]. In the present work, a relatively fast, simple, sensitive and selective

derivative spectrophotometric method is presented for the analysis of Maneb by

converting it into molybdenum complex. Maneb reacts with sodium molybdate on

heating to form a blue coloured complex. Maneb and sodium molybdate combine in the

ratio 1:2 to form complex. Maneb releases Mn2+

and dithiocarbamate unit, the latter

forms complex with sodium molybdate, which is then extracted into methyl isobutyl

159

ketone (MIBK) and determined by derivative spectrophotometry. The significant

advantage of this method over the gas chromatographic methods is that it can be applied

for the direct determination of Maneb in the presence of other dithiocarbamates like

Ziram, Nabam and Zineb.

5.2.2 Experimental


Elico SL-164, Double Beam UV-Vis spectrophotometer was used. Maneb standard was

obtained from Riedel de Haën, Germany. A stock solution was prepared by heating100

mg of Maneb in 100 mL of 0.1 mol L-1

of NaOH. Further dilutions were carried out with

0.1 mol L-1

of NaOH as required. A 2% (m/v) solution of sodium molybdate was

prepared in doubly distilled water.

5.2.3 Procedures


To an aliquot containing 100 g of Maneb were added 2 mL of 2% sodium molybdate

solution and 1 mL of 2 mol L-1

of H2SO4. The mixture was boiled for 5 minutes, cooled

and water was added to make the volume 5 mL. The blue complex formed was extracted

into 5 mL of MIBK (methyl isobutyl ketone) with shaking. The organic layer was

collected into a test tube containing fused CaCl2 to remove any moisture. The solution

was then decanted into a 1 cm cell and the spectra were taken against a reagent blank.

The molybdenum complex shows peaks at 670 nm and 956 nm [Figure 5.2.2], but the

peak at 956 nm has much higher absorbance; hence all the measurements were made at

this wavelength. The first derivative, second derivative, third derivative and fourth

160

derivative curves were given in figures 5.2.3-5.2.6 respectively. In DS (Derivative

Spectrophotometry), the λ reproducibility and S to N ratio are quite important. The

features like peak height and noise level depend on parameters chosen like order of

derivative; scan speed and integration time during recording of spectra. The use of

optimum parameters will give better resolution and more sensitivity. For the 4th

derivative

spectra, Δλ = 9 nm was found to be ideal.


The known volumes of sample solutions having 10-250 µg of Maneb were analyzed by

general procedure and the derivative spectra were obtained against a reagent blank

prepared under the similar conditions. The characteristics of zero order spectrum are

summarized in Table 5.2.1. The figures 5.2.3-5.2.6 show the derivative spectra of

different orders. The comparison of calibration curves of different derivative spectra are

provided in the Table 5.2.2.


5.2.4.1 Beer’s law and Sensitivity



nm. The calibration curve was obtained by measuring the peak height between

wavelength of 850 and 938 nm. Absorbance of sodium molybdate complex with Maneb

recorded against a reagent blank was linear over the concentration range from 2 µg 5

mL-1

to 40 µg 5mL-1

of the final solution. The detection limit is 0.0011 µg mL-1

for

Maneb when S/N ratio was 3.

161



increasing the heating time. Therefore, the reaction mixture was heated for different

intervals of time. It was observed that an optimum heating time of 5 minutes was

sufficient to obtain maximum absorbance. Increasing the heating time beyond this did not

increase the absorbance as the complete complexation was achieved by heating for 5 min.


Maximum absorbance was observed when volume of acid added was between 1 mL to

1.5 mL. A decrease in absorbance was observed on further increasing the amount of acid


5.2.4.4 Effect of other ions


of Maneb and various amounts of different alkali

metal salts or metal ions were prepared and the general procedure was applied. It was

observed that 20 mg of following foreign anions didn't interfere in the determination of

Maneb: bromide (11 mg), acetate (15 mg), chloride (3.5 mg), fluoride (2 mg), citrate (20

mg) and EDTA (0.06 mg). Of the metal ions examined, Mn (II) (0.066 mg), Mo(IV)

(0.14 mg), Ni(II) (0.30 mg), Co(II) (0.009 mg) did not interfere. Fe (II) and Zn(II) were

masked with 1 mL of 5% NaF solution and 1 mL of 5% KCN solution respectively. 1 mL

of 5% potassium iodide and thiourea were used to mask Hg (II) and Cu (II) respectively.

It is thus clear that several ions like Fe, Zn, Hg etc. interfered in maneb determination.


It was observed that the absorbance of the solution became constant after 2-3 min. so

162

after extracting into MIBK, a 5 min. standing time was selected. The absorbance of the

complex remained practically constant for about 30 minutes with the R.S.D. of

absorbance values varying between 0.69 to 1.6 % for different concentrations.

5.2.5 Applications (Determination of Maneb from fortified samples of wheat grains

and soft drinks)

The method was applied to the determination of Maneb from fortified samples of wheat

grains, cabbage and soft drink samples.

5.2.5.1 Sample preparation for food stuffs

The foodstuff (20 g) taken was finely crushed and a solution containing known amount of

maneb was added, it was mechanically shaken with 100 mL of ACN (Acetonitrile) for 1

hour. This mixture was filtered and the residue in funnel was washed with 3 x 10mL

portions of ACN. The extracts were evaporated on a water bath (70-90oC). The last traces

of solvent were removed using a current of dry air. The Maneb content in the residue was

determined by the general procedure and the results indicated good recoveries in all

cases. The results of the determinations were given in Table 5.2.3.

5.2.5.2 Sample preparation for soft drinks

The soft drinks (coke and limca) were locally obtained. These were diluted ten times,

filtered and spiked with known amount of maneb solution. The maneb content was

determined by the general procedure using a reagent blank prepared under similar

conditions.

163

5.2.5.3 Determination of Maneb in commercial samples

The method was applied for determination of Maneb in commercial samples. The

formulated product sample solutions were prepared as discussed earlier and determined

by the general procedure. The results of the determinations were given in Table 5.2.4.

5.2.5.4 Simultaneous determination of Maneb in presence of Ziram in synthetic

mixtures

The method was applied for the simultaneous determination of Ziram and Maneb in

synthetic mixtures. Ziram forms a yellow complex with sodium molybdate in cold, which

absorbs at 420 nm [26] whereas Maneb forms complex on heating, all other conditions

remaining the same. Synthetic mixtures of maneb and ziram were made in different

proportions. To the binary mixture, 0.15 mL of 2 mol L-1

of H2SO4 and 2 mL of 2%

sodium molybdate were added. Molybdenum-ziram complex was extracted into 5 mL

MIBK and maneb remained in aqueous phase. The absorbance of ziram-molybdenum

complex was measured at 420 nm. To the aqueous phase containing maneb was added

1mL 4 mol L-1

H2SO4 and 2mL of 2% Na2MoO4 solution. The solution was boiled for 5

minutes, cooled and extracted into 5 mL MIBK, the spectra of blue complex of maneb

was taken between 600 nm and 1100nm. Thus, this method was applied for the

simultaneous determination of ziram and maneb. Ziram was determined from the

standard calibration curve. The results of the determinations are given in Table 5.2.5.

5.2.6 Conclusions

The present method is more sensitive than the carbon disulphide evolution methods. It is

superior to the reported methods and the direct simultaneous determination of ziram and

164

maneb is possible. The sensitivity of the present method is comparable to other

spectrophotometric methods [Table 5.2.6]. The selectivity of the present method is

superior to other methods. The wide applicability of this method makes it suitable for

dithiocarbamate analysis in foodstuffs and in commercial samples.

165

Figure 5.2.2: Absorption spectrum of Maneb-molybdate complex: Maneb (2 mL)

with sodium molybdate (2%) in presence of H2SO4 (2M), extracted into MIBK

against a reagent blank.

0

0.05

0.1

0.15

0.2

0.25

0.3

0.35

0.4

0.45

600 650 700 750 800 850 900 950 1000

Ab

sorb

ance

Wavelength (nm)

166

Figure 5.2.3: 1st derivative curves of molybdenum- ethylenebisdithiocarbamate

complex: a, b, c, d representing the amounts of Maneb in final solutions (a: 10, b:

20, c: 30 and d: 40 μg mL-1

)

Figure 5.2.4: 2nd

derivative curves of molybdenum- ethylenebisdithiocarbamate


20, c: 30 and d: 40 μg mL-1

)

d c b a

a b c d

167

Figure 5.2.5: 3rd



20, c: 30 and d: 40 μg mL-1

)

Figure 5.2.6: 4th



20, c: 30 and d: 40 μg mL-1

)

168

Table 5.2.1: Different parameters of zero order spectrum

Serial

No.

Parameter Zero order spectrum of

maneb- sodium molybdate

complex

1.

Molar Absorptivity

(L.mol-1

cm—1)

8.16 x 104

2.

Sandell’s Sensitivity (μg mL

-1)

0.0049

3.

Analytical Sensitivity (μg mL

-1)

0.0011

4.

Linear Range (μg mL

-1)

2 to 40

Table 5.2.2: Comparison of calibration curves of Maneb using different derivative

spectra

Zineb

Complex

Order of

Derivative

λ

(nm)

Regression Equation R2

S.D. of

Slope

Analytical

Sensitivity

µg/mL

1.

1st

814 y= 4 X 10-5

x -0.0001

0.9997

1.2 X 10-6

1.4

2. 2nd

950 y= 7 X 10-6

x -0.0002 0.9992 2.4 X 10-7

0.9

3.

3rd

932

y= 3 X 10-6

x -5 X10-5

0.9995

1.4 X 10-8

0.032

4. 4th

904 y= 8 X 10-7

x +7 X10-6

0.9994 2.3 X 10-9

0.0011

169

Table 5.2.3: Determination of Maneb in fortified samples (mean values and

standard deviations, n=5)

Fungicide Sample Maneb added

(μg)

Maneb found

(μg)

Recovery (%)

± RSD (%)

Wheat 10 9.8 98 ± 2.1

15 14.9 99.3 ±1.9

20 19.8 99 ± 1.9

Cabbage 8 7.8 97.5 ± 2.2

Maneb 10 9.7 97 ± 1.9

Coke 10 9.1 91 ± 2.4

20 18.6 93 ± 2.1

25 23.9 95.6 ± 2.5

Limca 10 9.0 90 ± 2.2

20 18.2 91 ± 1.8

25 23.6 94.4 ± 1.8

170

Table 5.2.4: Determination of Maneb in commercial samples (mean values and

standard deviations, n=5)

Commercial

Sample

Maneb

taken (μg)

Maneb

found (μg)

Recovery (%)

± RSD(%)

Rangaswamy et al

method22

Maneb found Recovery %

(μg)

Dithane M-45

(80% W.P.) 20 19.9 99.5 ±1.5 19.7 98.5

30 30 100 ± 1.8 29.8 99.3

40 39.9 99.8 ± 1.6 39.8 99.5

Dithane M-22

(80% W.P.) 20 19.8 99 ± 1.6 19.7 98.5

30 29.8 99.3 ± 1.4 29.6 98.7

40 39.9 99.8 ± 1.5 39.8 99.5

171

Table 5.2.5: Determination of Maneb and Ziram in synthetic mixtures (mean values

and standard deviations, n=5)

Maneb

added (μg)

Ziram added

(μg)

Maneb

found (μg)

Ziram found

(μg)

Recovery (%) ± RSD (%)

Maneb Ziram

30 40 29.5 38.8 98.3 ± 2.3 97 ± 2.3

20 30 19.6 29.0 98.0 ± 2.6 96.7 ± 2.5

15 20 14.5 19.0 96.7 ± 2.1 95 ± 2.6

Table 5.2.6 Comparison of molar absorptivities of Maneb complexes

Procedure

Molar

Absorptivity

(L.mol-1

cm-1

)

Remarks Reference

Molybdenum

0.4 x 10 4

Low sensitivity and

selectivity

28

Rangaswamy et al method

_

Low sensitivity, long

tedious procedure

30

Complex formation with

diphenylcarbazone and

pyridine

6.5 x 104

Extraction not rapid

and uses toxic pyridine

51

Complex formation with

PAN

4.1 x 104

Less sensitive than

present method

52

Molybdenum (at 956 nm)

and derivative

spectrophotometry 8.1 x 10

4 Better sensitivity Present work

172


Determination of Propineb (Zinc propylene bis

dithiocarbamate) fungicide using Sodium Molybdate

5.3.1 Introduction

Propineb [polymeric zinc propylenebis dithiocarbamate)] [(C5H8N2S4Zn)x] is a polymeric

dithiocarbamate substance that acts as a potent, nonsystemic, protective fungicide.

Figure 5.3.1: Structure of Propineb

The dithiocarbamate pesticides like propineb are favored worldwide as their properties

like low toxicity, high effectiveness and low production costs make them a popular

choice for fungal crop protection on various crops like potato, tomatoes, apples, grapes

etc [53, 54]. A new, commercially available fungicide formulation, Propineb 70% WP,

belonging to the group of propylenebisdithiocarbamates is also suitable for above

purposes [55, 56]. Though dithiocarbamates are known to display low acute and chronic

toxicities in human and experimental animals [57], but propineb and its residues like PTU

(phenyl thiourea) are extremely reactive due to their metal-chelating ability [58], and

high affinity for proteins containing the -SH group. DTC complexes are toxic and have

mutational effect [59], several researchers have studied the adverse effects of DTC

173

compounds including propineb [60-65]. The mobility of dithiocarbamate fungicides such

as mancozeb, sodium diethyldithiocarbamate, ziram, propineb and zineb through the soil

was studied by Rathore et al [40], whereas, Aktar et al studied the persistence and

dissipation of propineb in potato tubers [66]. A number of methods are available in the

literature for propineb analysis. Banerjee et al [67] and Schwack et al [68] determined the

Propineb residues in terms of CS2. A new cellular biosensor was developed for

determining the propineb residues by Flampouri et al [69] whereas Lo et al have

described HPLC and Atomic absorption methods for distinguishing between

dithiocarbamate fungicides like propineb, zineb, maneb and mancozeb [46]. Kazos et al

[70] developed a GC–MS and an improved HPLC method. Gas chromatographic

methods were also developed by Royer et al 1 and Česnik et al [48]. Nakazawa et al

[16] developed a reversed-phase ion-pair liquid chromatography with chemiluminescence

method for the determination of dithiocarbamates like propineb and mancozeb. Sharma et

al [71] have discussed various analytical methods for thiram analysis. The above

discussed methods have several disadvantages like the methods apart from gas

chromatography are less sensitive, indirect and time inefficient. Gas chromatographic

methods on the other hand have better sensitivity but are not selective as all

dithiocarbamates evolve CS2. The liquid chromatographic methods are comparatively

expensive and further use toxic and costly solvents. The present method is based on the

complexation of dihtiocarbamate fungicide zineb with sodium molybdate as developed

by Rao et al [5]. This method was also applied by Sharma et al [73] for the determination

of fungicide thiram in grains and commercial samples. In this method the

dithiocarbamate unit of the fungicide forms coloured complex with the molybdate ion

which is then extracted into the methyl isobutyl ketone (MIBK) for spectrophotometric

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174

analysis. The present work describes a sensitive, efficient and more selective derivative

spectrophotometric method for the determination of dithiocarbamate fungicide, propineb

where it is complexed with sodium molybdate. Propineb can be determined in presence

of dithiocarbamate fungicides ziram or thiram by this method.

5.3.2 Experimental


Elico SL-164, Double Beam UV-Vis spectrophotometer was used. Propineb standard was

obtained from Riedel de Haën, Germany. A stock solution was prepared by heating100

mg of Propineb in 100 mL of 0.1 mol L-1

of NaOH. Further dilutions were carried out

with 0.1 mol L-1

of NaOH as required. A 2% (m/v) solution of sodium molybdate was

prepared in doubly distilled water.

5.3.3 Procedures


2 mL of 2% sodium molybdate solution and 1 mL of 2 mol L-1

of H2SO4 were added to an

aliquot containing 100 µg of Propineb. The mixture was boiled for 5 minutes, cooled and

water was added to make the volume 5 mL. The blue complex formed was extracted into

5 mL of MIBK (methyl isobutyl ketone) with shaking. The organic layer was collected

into a test tube containing fused CaCl2 to remove any moisture. The solution was then

decanted into a 1 cm cell and the spectra were taken against a reagent blank. The

molybdenum complex shows peaks at 670 nm and 956 nm (Figure 5.3.2), but the peak at

956 nm has much higher absorbance; hence all the measurements were done at this

wavelength. The fourth derivative curve is given in figure 3 and the calibration curve for

175

fourth order spectra is presented in figure 5.3.3. In DS (Derivative Spectrophotometry),

the λ reproducibility and S to N ratio are quite important. The features like peak height

and noise level depend on parameters chosen like order of derivative; scan speed and

integration time during recording of spectra. The use of optimum parameters will give

better resolution and more sensitivity. For the 4th

derivative spectra, Δλ = 9 nm was found

to be ideal.


The known volumes of sample solutions having 20-300 µg 5mL-1

of Propineb were

analyzed by general procedure and the derivative spectra were obtained against a reagent

blank prepared under the similar conditions. The characteristics of 1st to 4

th order spectra

are summarized in Table 5.3.1.

5.3.4 Applications

5.3.4.1 Determination of Propineb from fortified food stuff samples

The method was applied to the determination of Propineb from fortified samples of

apples, grapes, potato, tomato and aubergines (egg plant).

5.3.4.1.1 Sample preparation for food stuffs

20 grams of the foodstuff was finely crushed and solution containing a known amount of

Propineb was added, it was mechanically shaken with 100 mL of Acetonitrile for 1 hour.

This mixture was filtered and the residue in funnel was washed with 3 x 10mL portions

of ACN. The extracts were evaporated on a water bath (70-90oC). The last traces of

solvent were removed using a current of dry air. The Propineb content in the residue was

176

determined by the general procedure and the results indicated good recoveries in all

cases. The recoveries from the fruit and vegetable samples show minor decrease due to

slight decomposition of pesticide during extraction [30]. The results of the determinations

were given in Table 5.3.2.

5.3.4.2 Determination of Propineb in commercial samples

The method was applied for determination of propineb in commercial samples. The

formulated product sample solutions were prepared as discussed earlier and determined

by the general procedure. The results of the determinations were given in Table 5.3.3.

5.3.4.3 Simultaneous determination of Propineb in synthetic mixtures

The method was applied for the simultaneous determination of Ziram and Propineb and

thiram and propineb in synthetic mixtures. Ziram forms a yellow complex with sodium

molybdate in cold, which absorbs at 420 nm [28] whereas Propineb forms blue complex

on heating, all other conditions remaining the same. Synthetic mixtures of Propineb and

Ziram were made in different proportions. To the binary mixture, 0.15 mL of 2 mol L-1

of

H2SO4 and 2 mL of 2% sodium molybdate were added. Molybdenum-ziram complex was

extracted into 5 mL MIBK and propineb remained in aqueous phase. The absorbance of

ziram-molybdenum complex was measured at 420 nm. 1 mL of 4 mol L-1

H2SO4 and 2

mL of 2% Na2MoO4 solution were added to the aqueous phase containing propineb was

added. The solution was boiled for 5 minutes, cooled and extracted into 5 mL MIBK, the

spectra of blue complex of propineb was taken between 600 nm and 1100 nm. Thiram

forms complex with sodium molybdate without heating which has absorption maxima at

360 nm. Thiram and propineb were determined simultaneously by the above method.

177

Thus, this method was applied for the simultaneous determination of propineb with ziram

or thiram. The results of the determinations are given in Table 5.3.4.


5.3.5.1 Analytical Performance



nm. The calibration curve for 4th

derivative spectra was obtained by measuring the peak

height at 956 nm. Absorbance of sodium molybdate complex with Propineb recorded

against a reagent blank was linear over the concentration range from 5µg mL-1

to 60 µg

mL-1

of the final solution. The detection limit has been found to be 0.0088 µg mL-1

from

4th

order spectra for Propineb when S/N ratio was 3.



increasing the heating time. Therefore, the reaction mixture was heated for different

intervals of time. It was observed that an optimum heating time of 5 minutes was

sufficient to obtain maximum absorbance. Increasing the heating time beyond this did not

increase the absorbance as the complete complexation was achieved by heating for 5

minutes


Maximum absorbance was observed when volume of acid added was between 1 mL to1.5

mL. A decrease in absorbance was observed on further increasing the amount of the acid

178


5.3.5.4 Interferences


of Propineb and various amounts of different

alkali metal salts or metal ions were prepared and the general procedure was applied. It

was observed that given amount of the following foreign anions didn't interfere in the

determination of Propineb : bromide (11 mg), acetate (15 mg), chloride (3.5 mg), fluoride

(2 mg), citrate (20 mg) and EDTA (0.06 mg). Of the metal ions examined, Mn (II) (0.066

mg), Mo (IV) (0.14 mg), Ni (II) (0.30 mg), Co (II) (0.009 mg) did not interfere. The

tolerable amounts of foreign species during determination of propineb are summarized in

table 5.3.5. Fe (II) and Zn (II) were masked with 1 mL of 5% NaF solution and 1 mL of

5% KCN solution respectively. 1 mL of 5% potassium iodide and thiourea were used to

mask Hg (II) and Cu (II) respectively. It is thus clear that several ions like Fe, Zn, Hg etc.

interfered in propineb determination. Thiram, ziram and ferbam if present could be

separated by extraction with chloroform followed by the propineb determination.

Propineb can be determined in presence of Thiram or ziram, as both form complexes with

sodium molybdate without heating, hence their complex can be extracted and propineb

left can then be determined by the method. Zineb and maneb interfere if present.


It was observed that the absorbance of the solution became constant after 2-3 min. so

after extracting into MIBK a 5 min standing time was selected. The absorbance of the

complex remained practically constant for about 30 minutes with R.S.D. of absorbance

values varying between 0.69 to 1.6 % for different concentrations.

179

5.3.6 Conclusion

The present method is more sensitive than the carbon disulphide evolution methods. It is

superior to the reported methods and the direct simultaneous determination of ziram and

propineb is possible. The sensitivity of the present method is good when compared to

other methods (Table 5.3.6) and has wide applicability as it doesn’t require expensive

reagents and equipments. The present method permits the determination of propineb in

presence of other dithiocarbamate fungicides Ziram or Thiram which is not possible with

gas chromatographic and liquid chromatographic methods. The recoveries were found to

be good during the simultaneous determinations. The large scope and application of this

method makes it suitable for dithiocarbamate analysis in foodstuffs and in commercial

samples.

180

Figure 5.3.2: Absorption spectrum of Propineb-molybdate complex: Propineb (2

mL) with sodium molybdate (2%) in presence of H2SO4 (2M), extracted into MIBK

against a reagent blank.

Figure 5.3.3: 4th derivative curves of molybdenum-propylenebisdithiocarbamate

complex: a, b, c, d, representing the amounts of propineb in final solutions ( a:30, b:

40, c: 50 and d: 60 µg mL-1

)

0.15

0.2

0.25

0.3

0.35

0.4

0.45

600 700 800 900 1000

Ab

so

rban

ce

Wavelength (nm)

-0.001

-0.0005

0

0.0005

0.001

0.0015

605 705 805 905

d4/d

λ4

Wavelength (nm)

d

c

b

a

181

Table 5.3.1: Comparison of Calibration curves of propineb-molybdate complex using different derivative spectra

Propineb

Complex

Order of

derivative

λ

(nm)

Linear Range

(µg mL-1

) Regression Equation R

2

Standard

Deviation of

Slope

LOD

(µg mL-1

)

1. 1st 872 5-60 y=5×10

-5x-0.0003 0.999 2.1×10

-4 13.86

2. 2nd 901 5-60 y=2×10

-5x+0.00025 0.994 2.1×10

-5 3.3

3. 3rd

928 5-60 y=6×10-6

x-0.0001 0.998 1.2×10-6

6.6

4. 4th

956 5-60 y=2×10-5

x-5×10-6 0.999 2.3×10

-6 0.38

182

Table 5.3.2: Determination of Propineb in fortified samples (n=5)

Fungicide Sample Propineb added

(µg )

Propineb

found (µg ) Recovery % ± R.S.D.

Propineb Tomato 10 8.9 89.0 ± 2.2

15 13.1 87.3 ± 2.2

20 17.5 87.5 ± 1.9

Potato 10 8.9 89.0 ± 2.1

15 13.0 86.7 ± 2.4

20 18.0 90.0 ± 1.9

Grapes 15 13.5 90.0 ± 2.5

20 17.8 89.0 ± 2.2

Apple 20 18.0 90.0 ± 2.1

25 22.6 90.4 ± 2.3

Aubergines 10 9.3 93.0 ± 1.8

20 18.3 91.5 ± 1.8

183

Table 5.3.3: Determination of Propineb in commercial samples (mean values and standard deviation, n=5)

Commercial Sample Propineb taken(µg) Propineb found

(µg) Recovery % ± R.S.D. (%)

Antracol (70% W.P.) 20 18.6 93.0±2.5

30 28.7 95.7±2.6

40 38.4 96.0±2.0

Propineb 70% WP 20 19.3 96.5±1.6

30 29.2 97.3±1.6

40 38.7 96.7±1.8

184

Table 5.3.4: Determination of Propineb in synthetic mixtures, (mean values and standard deviations n=5)

Propineb

added (µg)

Ziram

added (µg)

Propineb

found (µg)

Ziram

found (µg)

Recovery % ± R.S.D. %

Propineb Ziram

30 40 27.8 38.7 92.7±3.7 96.75±3.8

20 30 18.7 28.8 93.5±4.2 96.0±3.4

25 25 23.2 24 92.8±4.3 96.0±3.3

Propineb

added (µg)

Thiram

added (µg)

Propineb

found (µg)

Thiram

found (µg)

Recovery% ± R.S.D.%

Propineb Thiram

30 50 28.2 47.6 94.0±2.3 95.2±2.5

40 40 38.1 38.2 95.3±2.1 95.5±2.1

185

Table 5.3.5: Effect of Foreign ions on Propineb determination

S. No. Foreign species Tolerable Amount (mg)

1. Bromide 11.0

2. Acetate 15.0

3. Chloride 3.5

4. Fluoride 2.0

5. Citrate 20.0

6. EDTA 0.06

7. Mn(II) 0.07

8. Mo(IV) 0.14

9. Ni(II) 0.30

10. Co(II) 0.01

186

Table 5.3.6: Comparison of limit of detection of propineb from different methods

S. No. Method Matrix LOD (µg mL-1

) Remarks Reference

1. Spectrophometric: CS2 evolution Tea leaves 0.10 Low sensitivity 67

2.

Spectrophometric: CS2 evolution Onion 0.20 (LOQ) Low sensitivity

77

3.

Photometric

determination

Miscellaneous 0.05 Low sensitivity

76

4.

HILIC column (LC-MS/MS) Apples,

tomatoes, etc.

0.001

Good sensitivity

but expensive

equipment

71

5.

Ion pair LC with

chemiluminescence detection using

Luminol

Vegetables 0.00042 High sensitivity but

expensive method

16

6. Derivative spectrophotometric

using sodium molybdate

Apples,grapes,

tomatoes, etc.

0.38,

0.0088

(analytical

sensitivity)

High sensitivity Present

method

187

References

1. S. K. Mehta, A. K. Malik, B. Singh and A. L. J. Rao, Talanta 67 (2005) 725.

2. A. K. Malik and C. Camara, Ethylenebisdithiocarbamates (Analysis) In

Encyclopedia of Agrochemicals, J. R. Plimmer, D. W. Gamon and N. N.

Ragsdale (Eds.), (2003) John Wiley and Sons Inc.,p 1.

3. R. Kesari and V. K. Gupta, Talanta 45 (1998) 1097.

4. V. Agarwal, P. Shivhare and V. K. Gupta, Fresenius J. Anal. Chem. 344

(1992) 350.

5. A. L. J. Rao and N. Verma, Talanta 36 (1989) 1041.

6. M. I. Walsh, F. Belal, M. E. Metwally and M. M. Hefnawy, Food Chem. 47

(1993) 411.

7. A. K. Malik and A. L J.; Rao, Talanta 38 (1991) 941.

8. J. Kapoor and A. L. J. Rao, Pestic. Sci. 42 (1994) 109.

9. J. R. Baena, M. Gallego and M. Valcarcel, Analyst 125 (2000) 1495.

10. R. J. Cassella, V. A. Salim, S. Garrigues, R. E. Santelli and M.dela Guardia,

Anal. Sci. 18 (2002)1253.

11. A. R. Cassella, R. J. Cassella, S. Garrigues, R. E. Santelli, R. C. de Campos

and M. de la Guardia, Analyst 125 (2000) 1829.

12. P. Maini and R. Boni, Environ. Bull. Contam. Toxicol. 37 (1986) 931.

13. K. Friedrichs, H.D. Winkeler and P. Gerhards, Z. Lebensm. Unters. Forsch.

201(1995) 69.

14. V. Bardarov, C. Zaikov and M. Mitewa, J. Chromatogr. 479 (1989) 97.

15. K. W.Weissmahr, C.L. Houghton and D.L. Sedlak, Anal. Chem. 70 (1998)

4800.

16. H. Nakazawa, Y. Tsuda, K. Ito, Y. Yoshimura, H. Kuba and H. Homma, J.

188

Liq. Chromatgr. Rel. Tehnol. 27 (2004) 705.

17. A. K. Malik and A.L.J. Rao, J. Indian Chem. Soc. 75 (1998) 491.

18. M. S.Lin, B. I. Jan, H. J. Leu and J. S. Lin, Anal. Chim. Acta 388 (1999) 111.

19. T. Noguer, Gradinaru, A.; Ciucu, A.; Marty, J. L., Anal. Lett. 32 (1999) 1723.

20. F. Gueguen, F. Boisdé, A. L. Queffelec, J. P. Haelters, D. Thouvenot, B.

Corbel and P. Nodet, J. Agric. Food Chem. 48 (2000) 4492.

21. A. K. Malik and A. L. J. Rao, J. Agric. Food Chem. 48 (2000) 4044.

22. N. A. Ulakhovich, E. P. Medyantseva, V.P. Frolova and O. N. Romanova, Zh.

Anal. Khim. 38 (1983) 1963.

23. B. C.Verma, H. S. Sidhu and R. K. Sood, Talanta 29 (1982) 703.

24. A. F. Grand and M. Tamres, Anal. Chem. 40 (1968) 1904.

25. D. D. Clyde, J. Assoc.Off. Anal. Chem.66 (1983) 646.

26. A. S. Hyman, Analyst 94 (1969) 152.

27. A. K. Malik and A. L. J. Rao, Talanta 37 (1990) 1205.

28. N. Verma, Ph.D.Thesis, (1985) Punjabi University, Patiala, India.

29. J. Kapoor, Ph.D.Thesis, (1993) Punjabi University, Patiala, India.

30. J. R. Rangaswamy, P. Poornima and S. K. Majumdar, J. Assoc. Off. Anal.

Chem. 54 (1971) 1120.

31. A. K. Malik, J. Kapoor and A. L. J. Rao, J. Environ. Monit. 2 (2000)367.

32. A. K. Malik, V. Sharma, V. K. Sharma and A. L. J. Rao, J. Agric. Food Chem.

52 (2004) 7763.

33. FAO Specifications FAO Plant Protection Products “Maneb (manganese

ethylenebisdithiocarbamate)”, Food and Agriculture Organisation of the

United Nations, Rome, 1979.

34. Risks of Mancozeb and Maneb uses to the federally listed California Red

Legged Frog(Rana aurora draytonii)”, Pesticide effects determination, Office

189

of Pesticide Programs, Wahington D. C. Oct. 18, 2007.

35. J. W. Hylin, Bull. Environ. Contam. Toxicol. 10 (1973) 227.

36. W. D. Marshall and W. R. Jarvis, J. Agric. Food Chem. 27 (1979) 766.

37. K. L. Dearfield, Mut. Res. 317 (1994) 111.

38. B. M. Ulland, J. H. Weisburger, E. K. Weisburger, J. M. Rice and R. Cypher,

J. Nat. Cancer Institute 49 (1972) 583.

39. Committee for analytical methods for residue of pesticides and veterinary

products in food stuffs, Ministry of Agriculture Fisheries and Food, Analyst

106 (1981) 782.

40. H. S. Rathore, G. Varshney and K. Ishratullah, Ind. J. Chem. Technol. 14

(2007) 400.

41. J. W. Hylin, Y. Kawano and W. Chang, Bull. Environ. Contam. Toxicol. 20

(1978) 840.

42. A. R. Türker and B. Sezer, Turk. J. Pharm. Sci. 2 (2005) 35.

43. G. Crnogorac and W. Schwack, Trends Anal. Chem. 28 (2009) 40.

44. A. Waseem, M. Yaqoob and A. Nabi, Anal. Sci. 25 (2009) 395.

45. Z. Vryzas, E. N. Papadakis and E. Papadopoulou-Mourkidou, J. Agric. Food

Chem. 50 (2002) 2220.

46. C. C. Lo, M. H. Ho and M. D. Hung, J. Agric. Food Chem. 44 (1996) 2720.

47. W. Shwack, B. Brüger and S. Nyanzi, Fresenius J. Anal. Chem. 351 (1995)

297.

48. H. B. Česnik and A. Gregorčič, Acta Chim. Slovenia 53 (2006) 100.

49. G. Crnogorac,

S. Schmauder and W. Schwack, Rapid Commun. Mass

Spectrom. 22 (2008) 2539.

50. J. R. Rangaswamy and Y. N. Vijayashankar, J. Assoc. Off. Anal. Chem. 58

(1975) 1232.

190

51. A. K. Malik, J. Kapoor and A. L. J. Rao, Chem. Environ Res. 1 (1992) 29.

52. A. L. J. Rao, A. K. Malik and J. Kapoor, Talanta (40) 1993 201.

53. H.van Lishaut and W. Schwack, J. AOAC Int. 83 (2000) 720.

54. C. Tomlin, The Pesticide Manual, 10th Edition, BCPC/RSC (1994), Crop

Protection Publications, Farnham and Cambridge, UK, p 3.

55. Anon. 19 1. “Antracol” Technical Information, Bayer (India) Limited,

Mumbai, p 12.

56. I. D. Sharma, A. Nath and J. K. Dubey, J. Food Sd. Tech. 31 (1994) 215.

57. J. Liesivuori and K. Savolainen, Toxicol. 91 (1994) 37.

58. P. Allain and N. Krari, Life Sci. 48 (1991) 291.

59. Committee for analytical methods for residue of pesticides and veterinary

products in food stuffs, Ministry of agriculture fishery and food, Analyst 106

(1981) 782.

60. D. B. Miller, Neurobehav. Toxicol. Teratol. 4 (1982) 779.

61. B. Viviani, S. Bartesaghi, M. Binaglia, E. Corsini, M. Boraso, E. Grazi, C.

L.Galli and M. Marinovich, Toxicol. Lett. 182 (2008) 63.

62. G. Schmuck, H. J. Ahr, F. Mihail, B. Stahl and M. Kayser M, Arch. Toxicol.

76 (2002) 414.

63. W. J. Hayes, Fungicides and related compounds: Dithiocarbamates, Handbook

of Pesticides Toxicology, W.J. Hayes and E.R. Laws (eds.), (1998) Academic

Press, San Diego.

64. I. D. Cohen and H. I. Robins, Invest New Drugs 8 (1998) 137.

65. L. Soleo, G. DeFazio, R. Scarselli, R. Zefferino, P. Livrea and V. Foà, Arch

Toxicol. 70 (1996) 678.

66. Md. W. Aktar, M. Paramasivam and D. Sengupt, Kasetsart J. (Nat. Sci.) 43

(2009) 50.

http://www.sciencedirect.com/science/journal/03784274


http://www.springerlink.com/content/?Author=Gabriele+Schmuck

http://www.springerlink.com/content/?Author=Hans-J%c3%bcrgen+Ahr

http://www.springerlink.com/content/?Author=Florin+Mihail

http://www.springerlink.com/content/?Author=Bernhard+Stahl

http://www.springerlink.com/content/?Author=Martin+Kayser

191

67. H. Banerjee, P. Ganguly, S. Roy, D. Banerjee, M. Paramasivam, T. Banerjee

and K. K. Sharma, Environ. Monit. Assess. 170 (2010) 311.

68. W. Schwack, B. Brüger and S. Nyanzi, Fresenius J. Anal. Chem. 351 (1995)

297.

69. K. Flampouri, S. Mavrikou, S. Kintzios, G. Miliadis and P. Aplada-Sarlis,

Talanta 80 (2010) 1799.

70. C. C. Lo, M. H. Ho and M. D. Hung, J. Agric. Food Chem. 44 (1996) 2720.

71. G. Crnogorac, S. Schmauder and W. Schwack, Rapid Commun. Mass

Spectrom. 22 (2008) 2539.

72. E. A. Kazos, C. D. Stalikas, C. G. Nanos and C. N. Konidari, Chromosphere

68 (2007) 2104.

73. A. Royer, M. Me´nand and A. Grimault, J. Agric. Food Chem. 49 (2001)

2152.

74. V. K. Sharma, J. S. Aulakh and A. K. Malik, J. Environ. Monit. 5 (2003) 717.

75. V. K. Sharma, J. S. Aulakh and A. K. Malik, Talanta 65 (2005) 375.

76. Ethylene and Propylene bisdithiocarbamate Fungicides Method S-2, pages

407-412 from “Manual of Pesticide Residue Analysis, Volume I and II”, ds.

H. P. Thier, J. Kirchhoff, Pesticides Commission, VCH (1984).

77. P. Ganguly, D. Banerjee, M. Paramasivam, S. Roy, T. Banerjee and H.

Banerjee, Pes. Res. J. 21(2009) 89.

http://www.ncbi.nlm.nih.gov/pubmed?term=%22Banerjee%20H%22%5BAuthor%5D

http://www.ncbi.nlm.nih.gov/pubmed?term=%22Ganguly%20P%22%5BAuthor%5D

http://www.ncbi.nlm.nih.gov/pubmed?term=%22Roy%20S%22%5BAuthor%5D

http://www.ncbi.nlm.nih.gov/pubmed?term=%22Banerjee%20D%22%5BAuthor%5D

http://www.ncbi.nlm.nih.gov/pubmed?term=%22Paramasivam%20M%22%5BAuthor%5D

http://www.ncbi.nlm.nih.gov/pubmed?term=%22Banerjee%20T%22%5BAuthor%5D

javascript:AL_get(this,%20'jour',%20'Environ%20Monit%20Assess.');

http://www.medworm.com/rss/search.php?qu=Talanta&t=Talanta&s=Search&f=source

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