simultaneous voltammetric determination of phenolic antioxidants in food using a boron-doped diamond...

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Analytical Methods

Simultaneous voltammetric determination of phenolic antioxidants in food using

a boron-doped diamond electrode

Roberta Antigo Medeiros, Romeu C. Rocha-Filho, Orlando Fatibello-Filho *

Departamento de Qumica, Universidade Federal de So Carlos, C.P. 676, 13560-970 So Carlos, SP, Brazil

a r t i c l e i n f o

Article history:Received 4 August 2009

Received in revised form 9 February 2010

Accepted 1 May 2010

Keywords:

Phenolic antioxidants

Butylated hydroxyanisoleButylated hydroxytoluene

Simultaneous determination

Square-wave voltammetry

Boron-doped diamond electrode

a b s t r a c t

A method for the simultaneous determination of butylated hydroxyanisole (BHA) and butylated hydroxy-toluene (BHT) in food was developed using square-wave voltammetry (SWV). The determination of these

phenolic antioxidants was carried out using a cathodically pre-treated boron-doped diamond electrode(BDD) and an aqueous-ethanolic (30% ethanol, v/v) 10 mmol L1 KNO3 solution (pHcond. 1.5) as supporting

electrolyte. In the SWV measurements using the BDD electrode, the oxidation peak potentials of BHA andBHT present in binary mixtures were separated by about 0.3 V. The attained detection limits for thesimultaneous determination of BHA and BHT (0.14 and 0.25lmol L1, respectively) are lower than the

ones by voltammetric techniques reported in the literature. The proposed method was successfully

applied in the simultaneous determination of BHA and BHT in food products, with results similar to thoseobtained using a high-performance liquid chromatography method, at a 95% confidence level.

2010 Elsevier Ltd. All rights reserved.

1. Introduction

Antioxidants (natural and synthetic) play a significant role in

retarding lipid oxidation reactions in food products. Thus, currentlythere are around 30 types of synthetic antioxidants whose additionto food directly or indirectly is allowed. The phenolic compoundsBHA and BHT are among the primary synthetic antioxidants widelyused to interrupt the chain of free radicals involved in the autoxi-

dation that constitutes the most common form of deterioration offats used in the food industry. They have been used both alone andin mixtures in oils, margarine, and mayonnaise (Delgado-Zamar-reno, Gonzalez-Maza, Sanchez-Perez, & Martinez, 2007; Diaz, Cab-

anillas, Franco, Salinas, & Vire, 1998), but their use is not aproblem-less solution. Since BHA and BHT are suspected of beingresponsible for liver damage and carcinogenesis in laboratory ani-mals, their potential harmful effects on health have been exten-

sively discussed and studied. Therefore, in several countries theuse of these additives is subject to regulations, which define spe-cific approved antioxidants, establish permitted use levels, and in-

clude labelling requirements. However, there are differencesamong the individual countries, i.e., antioxidants permitted inone country may be prohibited in another. Internationally, the JEC-FA (Joint FAO/WHO Expert Committee on Food Additives) periodi-

cally considers food additives, including synthetic phenolicantioxidants (SPAs), on the basis of all available scientific data, to

establish acceptable daily intake levels and specifications of iden-tity and purity for them (FAO/WHO, 1995; Guan, Chu, Fu, Wu, &Ye, 2006). In the European Union, for example, the amount of syn-thetic antioxidants in food is limited to 0.01% (100 mg kg1) foreach antioxidant, if used individually, and to 0.02% as total fraction,if the antioxidants are used in mixtures (Delgado-Zamarreno et al.,2007). In Brazil, the use of these antioxidants is controlled by TheNational Health Surveillance Agency (ANVISA), which limits the

amount to 200 mg kg1, for BHA, and to 100 mg kg1, for BHT(ANVISA, 2005). Thus, the determination of SPAs in foods is neces-sary to ensure the fulfilment of legal requirements as well as qual-ity-control procedures in the food industry.

Many methods for determining BHA and BHT individually orsimultaneously have been recently reported, based on spectropho-tometry (Capitan-Vallvey, Valencia, & Nicolas, 2004), liquid and gaschromatography (Guo, Xie, Yan, Wan, & Wu, 2006; Perrin & Meyer,

2002; Saad et al., 2007), micellar electrokinetic chromatography(Delgado-Zamarreno et al., 2007; Guan et al., 2006), and flow injec-tion and HPLC with amperometric detection (Luque, Rios, & Valcar-

cel, 1999; Riber, de la Fuente, Vazquez, Tascon, & Batanero, 2000;Ruiz, Garcia-Moreno, Barbas, & Pingarron, 1999). But they areprone to many drawbacks, such as expensiveness, complicatedand lengthy procedures, and unsuitability for field use.

Electrochemical techniques, such as the voltammetric ones, area promising alternative to classical approaches due to their rela-tively low operational cost, good miniaturization potential, and ra-pid and sensitive detection procedures, which are suitable for

faster analyses. Some methods for determining BHA and BHT by

0308-8146/$ - see front matter 2010 Elsevier Ltd. All rights reserved.doi:10.1016/j.foodchem.2010.05.010

* Corresponding author. Tel.: +55 16 33518098; fax: +55 16 33518350.

E-mail address: [email protected] (O. Fatibello-Filho).

Food Chemistry 123 (2010) 886891

Contents lists available at ScienceDirect

Food Chemistry

j o u r n a l h o m e p a g e : w w w . e l s e v i e r . c o m / l o c a t e / f o o d c h e m
http://dx.doi.org/10.1016/j.foodchem.2010.05.010mailto:[email protected]://dx.doi.org/10.1016/j.foodchem.2010.05.010http://www.sciencedirect.com/science/journal/03088146http://www.elsevier.com/locate/foodchemhttp://www.elsevier.com/locate/foodchemhttp://www.sciencedirect.com/science/journal/03088146http://dx.doi.org/10.1016/j.foodchem.2010.05.010mailto:[email protected]://dx.doi.org/10.1016/j.foodchem.2010.05.010


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voltammetric techniques were already reported (Ag, Reviejo,Yanezsedeno, & Pingarron, 1995; Ceballos, 2006; Ceballos & Fer-

nandez, 2000a; Ceballos & Fernandez, 2000b; De la Fuente, Acuna,Vazquez, Tascon, & Batanero, 1999; Diaz et al., 1998; Kumar &Narayanan, 2008; Ni, Wang, & Kokot, 2000; Raymundo, Paula,Franco, & Fett, 2007). Diaz et al. (1998) studied the voltammetric

behaviour of propyl gallate (PG), BHA, and BHT at a glassy-carbon

(GC) electrode (static and rotating) in an acetonitrilewater med-ium; they used a chemometric procedure for the determinationof these antioxidants in different spiked samples of packet soup.

Ni et al. (2000) studied the voltammetric behaviour of BHA, BHT,PG, and tert-butylhydroquinone, at a GC electrode in a 0.1 mol L1

perchloric acid solution containing 1% methanol, using chemomet-ric approaches such as classical least squares, principal-component

regression, and partial least squares. Linear calibration plots wereobtained in the concentration ranges 2.883lmol L1, for BHA,and 2.836 lmol L1, for BHT, with detection limits of 1.0 and

0.68 lmol L1, respectively. The method was applied to determinethe four antioxidants in a set of synthetic mixtures as well as inseveral commercial food samples. Ceballos and Fernandez(2000b) used SWV with carbon-disk ultramicroelectrodes to deter-

mine BHA and BHT in vegetable oils. The determinations were car-ried out directly in benzene/ethanol/H2SO4 solutions or inacetonitrile after an extractive procedure, with better results inthe latter case. Ag et al. (1995) used cylindrical carbon-fibre

microelectrodes in the simultaneous determination of BHA andBHT by SWV, obtaining detection limits of 4.0 lmol L1, for BHA,and 0.37 lmol L1, for BHT; however, the supporting electrolyteused contained acetonitrile, a high-cost reagent.

Thin films of BDD have emerged as excellent electrode materialsfor several electrochemical applications, especially electroanalyti-cal ones, mainly due to properties such as: a wide potential windowin aqueous solutions (up to 3 V), low background currents, long

term stability, and low sensitivity to dissolved oxygen (Hupertet al., 2003; Panizza & Cerisola, 2005). The properties of BDD arecommonly affected by the quantity and kind of the doping agent,

morphologic factors and defects in the film, presence of impurities(sp2 carbon), crystallographic orientation, and surface terminations(hydrogen or oxygen) that may be markedly determined by electro-chemical pre-treatments (Salazar-Banda et al., 2006; Suffrediniet al., 2004). Suffredini et al. (2004) called to attention that a catho-

dic pre-treatment of a BDD electrode dramatically increased theelectroanalytical detection limit for chlorophenols, indicating thatthe analytical performance of BDD electrodes greatly depends ontheir surface termination, i.e., whether they are hydrogen or oxygen

terminated. Recently, in our research group cathodically pre-trea-ted BDD electrodes were used for the determination of aspartameand cyclamate in dietary products, individually (Medeiros, de Carv-

alho, Rocha-Filho, & Fatibello-Filho, 2007; Medeiros, de Carvalho,Rocha-Filho, & Fatibello-Filho, 2008b) or simultaneously (Medeiros,

de Carvalho, Rocha-Filho, & Fatibello-Filho, 2008a), acetylsalicylicacid (Sartori, Medeiros, Rocha-Filho, & Fatibello-Filho, 2009), para-

cetamol and caffeine (Loureno, Medeiros, Rocha-Filho, Mazo, &Fatibello-Fiho, 2009) or sulfamethoxazole and trimethoprim (And-rade, Rocha-Filho, Cass, & Fatibello-Filho, 2009) simultaneously,and sildenafil citrate Viagra (Batista, Sartori, Medeiros, Rocha-

Filho, & Fatibello-Filho, 2010) in pharmaceutical formulations.In this paper, we report on the coupling of voltammetric tech-

niques with the unique properties of the BDD electrode for thedevelopment and optimisation of a method for the simultaneous

determination of BHA and BHT in several food products. The prac-tical use of the method is demonstrated by determining the con-centration of BHA and BHT in commercial margarine andmayonnaise samples and by comparing the obtained results with

those from a high-performance liquid chromatography (HPLC)method.

2. Materials and methods

2.1. Apparatus

The cyclic (CV), differential pulse (DPV), and square-wave(SWV) voltammetric experiments at a stationary BDD electrode

were performed using an Autolab PGSTAT-30 (Ecochemie) poten-

tiostat/galvanostat controlled with the GPES 4.0 software. Athree-electrode cell system was also used: a BDD working elec-trode, a Pt-wire auxiliary electrode, and an Ag/AgCl (3.0 mol L1

KCl) reference electrode to which all electrode potentials hereinaf-ter are referred.

The boron-doped (8000 ppm) diamond (0.72 cm2 exposed area)

film on a silicon wafer was obtained from the Centre Suisse deElectronique et de Microtechnique SA (CSEM), Neuchatl, Switzer-land (Salazar-Banda et al., 2006). Prior to use, the BDD electrodewas cathodically or anodically pre-treated in a 0.5 M H 2SO4 solu-

tion by applying 1.0 A cm2 or 1.0 A cm2, respectively, during120 s. A GC electrode (0.2 cm2) was also used for comparative pur-poses. Prior to use, this electrode was pre-treated by sequentialpolishing with alumina (1 and 0.05 lm)/water slurries on felt pads,

followed by rinsing with ultra-pure water.The BHA and BHT determinations by HPLC were carried out

using an LC-10 AT Shimadzu system, with an ultravioletvis detec-tor (SPD-M10-AVP) set at 290 and 278 nm. A Shim-Pack CLC-ODS

(6.0 mm 250 mm, 5 lm) chromatographic column was used.The mobile phase was an acetonitrile/methanol mixture (50/50,v/v) at a flow rate of 1.0 mL min1, while the injection volumewas 30 lL (Perrin & Meyer, 2002).

2.2. Reagents, supporting electrolyte and standards

All reagents were of analytical grade: BHA and BHT (Sigma),KNO3 (Aldrich), and ethanol (Quemis, Brazil). An aqueous-etha-nolic (30% ethanol, v/v) 10 mmol L1 KNO3 solution (pHcond 1.5adjusted with 1.0 mol L1 HNO3) was used as supporting electro-

lyte. Standard 1.0 mmol L1 BHA and BHT solutions were preparedin this supporting electrolyte. All solutions were prepared usingultra-purified water supplied by a Milli-Q system (Millipore) with

a resistivity greater than 18 MO cm.

2.3. Measurement procedures

After optimising the experimental parameters for the proposedmethods, the analytical curves were constructed by adding smalland equal volumes of the concentrated standard solutions of the

two analytes to the supporting electrolyte in order to have the fol-lowing concentrations: 0.6, 1.0, 2.0, 3.0, 4.0, 5.0, 6.0, 7.0, 8.0, 9.0,and 10.0 lmol L1. The detection limit was calculated as threetimes the standard deviation for the blank solution divided by

the slope of the analytical curve.

2.4. Influence of voltammetric techniques in the determination of the

antioxidants

The electrochemical behaviour of the antioxidants was investi-

gated using three different voltammetric techniques. CV was usedfor preliminary studies, such as the choosing of supporting electro-lyte and pH. DPV and SWV were used for investigating the deter-mination of the antioxidants and finding the best conditions.

2.5. Treatment of commercial food samples

A procedure similar to that proposed by Luque et al. (1999) andRaymundo et al. (2007) was followed for the determination of BHA

R.A. Medeiros et al. / Food Chemistry 123 (2010) 886891 887


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and BHT in commercial margarine and mayonnaise samplespurchased at a local supermarket. A sample of about 1.0 g was

dissolved in 1 mL of ethanol contained in a large test tube. Aftershaking for 5 min, this mixture was centrifuged at 5000 rpm for10 min. This extraction procedure was repeated twice; the extractswere collected and then diluted to 5 mL with the supporting elec-

trolyte. A 500 lL aliquot was transferred to the electrochemical cell

already containing 9.5 mL of the supporting electrolyte, where BHAand BHT were simultaneously determined by using the standardaddition method. For the HPLC measurements, after the extraction

procedure, the extracts were diluted in 5 mL of the mobile phase;previous to injection, a 500lL aliquot was further diluted to10 mL with the mobile phase.

3. Results and discussion

3.1. Investigation of the electrochemical behaviour of BHA and BHT

Firstly, CV was used to investigate the electrochemical behav-iour of both compounds in various supporting electrolytes: phos-phate buffer, BrittonRobinson buffer, acetate buffer, andpotassium nitrate, all prepared with an aqueous-ethanolic (30%

ethanol, v/v) mixture as solvent. The best results were obtainedwith a 10 mmol L1 KNO3 solution (pHcond. 1.5 adjusted with1.0 mol L1 HNO3). Using this supporting electrolyte, peak oxida-tion potentials of 0.65 and 0.93 V were obtained for BHA and

BHT, respectively, and the obtained voltammograms presentedan irreversible behaviour (results not shown), in agreement withdata previously reported in the literature (Ag et al., 1995). A lin-ear plot of the peak current vs. the square root of the scan rate was

obtained for both antioxidants (r= 0.999 and 0.996 for BHA andBHT, respectively), indicating that the electrode process is con-trolled by mass transport.

Secondly, electroanalytical procedures were developed for BHA

and BHT individually using SWV and DPV. The optimisation of theexperimental parameters that affect the SWV and DPV responses

was carried out. The optimum values obtained for SWV were: fre-quency, 100 Hz; amplitude, 50 mV; scan increment, 4 mV. For DPV,

they were: pulse amplitude, 60 mV; scan rate, 60 mV s1; Modula-tion time, 10 ms. According to the obtained results, the electroan-alytical procedure developed using SWV yielded the best values forthe figures of merit, for both antioxidants. Therefore, SWV was the

technique chosen for the subsequent development of an electroan-alytical procedure for the simultaneous determination of BHA andBHT.

3.2. Simultaneous determination of BHA and BHT

Fig. 1 shows the square-wave voltammetric curves obtained atBDD and GC electrodes for 10 lmol L1 BHA and 10 lmol L1 BHT

simultaneously in the supporting electrolyte. Well-defined peakcurrents were obtained for both antioxidants; however, the vol-

tammogram obtained with the BDD electrode yielded higherpeak-current values, especially the one for BHT. Hence, furtherstudies were carried out only with the BDD electrode.

The square-wave voltammograms obtained for both antioxi-

dants with the BDD electrode after anodic and cathodic pre-treat-ments are shown in Fig. 2. As it can be seen, when the cathodicallypre-treated electrode is used, two well-defined oxidation wavescan be observed. The first (Ep = 0.65 V) and the second

(Ep = 0.93 V) waves correspond to the oxidation of BHA and BHT,respectively. When the anodically pre-treated electrode was used,the magnitude of these two waves decreased and their peak poten-tials became more positive. Consequently, all subsequent experi-

ments were carried out using a cathodically pre-treated BDDelectrode.

According to the accepted SWV theories (Scholz, 2005), thenumber of electrons transferred in the redox process can be inves-

tigated using the relationship:

DEp=D log f 2:3RT=anF 1

where a is the transfer coefficient and n the number of electrons in-volved in the redox reaction, the other terms having their usual

meaning. The slopes obtained from the Ep vs. log f plots were

0.0608, for BHA, and 0.0591, for BHT; thus, by means of Eq. (1), val-ues equal to 0.970 V (BHA) and 0.993 V (BHT) were determined for

an. If the value ofa is assumed as equal to 0.5, a common feature for

organic molecules, these results indicate that the oxidation of BHAand BHT involves two electrons per molecule. From these resultsand considering the proposed oxidation mechanisms for com-pounds BHA and BHT (Ceballos, 2006; de la Fuente et al., 1999),

the electrochemical oxidation of BHA or BHT is believed to occurby a two-electron mechanism (Fig. 3).

The approximate surface concentration (C) of the adsorbed spe-cies was also calculated according to the accepted SWV theories,using the following equation (Scholz, 2005):

Ip 5 1 102Aan2FfaDEsC 2

where A is the electrode geometric area. The calculated values forCwere 0.10 nmol cm2, for BHA, and 11 nmol cm2, for BHT.

0.4 0.6 0.8 1.0

0.0

0.5

1.0

1.5

2.0

j(A

cm-2)

E / V vs. Ag/AgCl (3.0 M KCl)

Fig. 1. SWV curves for 10 lmol L1 BHA and 10 lmol L1 BHT on a CG electrode

(dashed lines) and a BDD electrode (solid line). Supporting electrolyte: aqueous-

ethanolic (30% ethanol, v/v) 10 mmol L1 KNO3 solution (pHcond. 1.5).

0.4 0.6 0.8 1.0 1.2

0.0

0.4

0.8

1.2

1.6

I/

E / Vvs.

Ag/AgCl (3.0 M KCl)Fig. 2. SWV curves obtained on an anodically (dashed line) and a cathodically (solid

line) pre-treated BDD electrode, using a mixture of 10 lmol L1 BHA and

10 lmol L1 BHT. Supporting electrolyte: aqueous-ethanolic (30% ethanol, v/v)

10 mmol L1 KNO3 solution (pHcond. 1.5).

888 R.A. Medeiros et al. / Food Chemistry 123 (2010) 886891


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The SWV curves presented a good peak-potential separation

(about 0.3 V), which clearly allows the simultaneous determina-tion of the compounds. Firstly, the separate determination of

BHA in the concentration range 0.6010 lmol L1 was accom-plished in solutions containing BHT at the fixed concentration of7.0 lmol L1 (Fig. 4). An examination ofFig. 4A allows concludingthat the peak oxidation current for BHA increases regularly as its

concentration is increased at a fixed concentration of BHA (its peakoxidation current remained constant RSD = 3.0%). Similarly, asshown in Fig. 4B, the peak oxidation current for BHT increases reg-

ularly as its concentration is increased at a fixed concentration ofBHA of 1.0 lmol L1 (its peak oxidation current remained fairlyconstant RSD = 8.1%).

After this previous study, both antioxidants were determined by

simultaneously changing their equal concentrations (see Fig. 5). By

analyzing the insets in this figure one can conclude that the respec-tive analytical curves presented a good linearity in the investigatedconcentration range (0.6010 lmol L1, for both BHA and BHT).

The corresponding calibration equations are (r= 0.9996, for both):

Ipa=lA 0:00179 0:227c=lmol L1

for BHA

Ipa=lA 0:0244 0:0973c=lmol L1

for BHT

The detection-limit values calculated for BHA and BHT were0.14 and 0.25 lmol L1, respectively, which are lower than thosereported by both Ag et al. (1995) and Ni et al. (2000). In the case

of BHA, the obtained detection limit is almost 30 or seven timeslower than the one reported by Ag et al. (1995) or Ni et al.

(2000), respectively. For BHT, the detection limit here reported isslightly lower than the ones reported by these authors.

The intra- and inter-day repeatabilities were determined bysuccessive measurements (n = 5) of BHA and BHT in different con-centrations; the obtained RSD values were: for BHA, intra-day,1.4%, and inter-day, 2.4%; for BHT, intra-day, 2.4%, and inter-day,

2.7%.Next, the selectivity of the proposed method was evaluated by

the addition of possible interferents (NaCl, soluble starch, EDTA,citric acid, and acetic acid) in a standard solution containing

10 lmol L1 BHA and 10 lmol L1 BHT, in the concentration ratios(standard solution:interferent) 10:1, 1:1, and 1:10; the obtainedcurrent signals were compared with those in the absence of eachpossible interferent. The analysis of the obtained responses al-

lowed concluding that these compounds do not significantly inter-fere with the here proposed method. The highest deviation was

found for EDTA at the concentration ratio 1:10, but it amountedto only 5.7%.

Finally, BHA and BHT were determined in seven different com-

mercial products (five mayonnaises and two margarines) by thestandard addition method. Recovery experiments carried out to

OCH3

OH

C(CH3)3

H2O

O

O

C(CH3)3

CH3OH H3O+

BHA

H2O

(CH3)3C C(CH3)3

O

CH3

H3O+

2 e-

OCH3

C(CH3)3

O

H3O+

2 e-2H2O

+

BHT

(CH3)3C C(CH3)3

OH

CH3

Fig. 3. BHA and BHT oxidation mechanisms at the BDD electrode surface.

0.0

0.5

1.0

1.5

2.0

2.5

I/


(A)

1

9

0.5 0.6 0.7 0.8 0.9 1.0 1.1

0.0

0.3

0.6

0.9

1.2

I/


(B)

1

12

0.5 0.6 0.7 0.8 0.9 1.0 1.1

Fig. 4. (A) SWV curves for various concentrations of BHA at a fixed concentration of

BHT (7.0 106 mol L1). BHA concentrations (19): 0.6010 lmol L1. (B) SWV

curves for various concentrations of BHT at a fixed concentration of BHA(1.0 lmol L1). BHT concentrations (212): 0.6010 lmol L1. Supporting electro-

lyte: aqueous-ethanolic (30% ethanol, v/v) 10 mmol L1 KNO3 solution (pHcond. 1.5).



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evaluate matrix effects after standard-solution additions yieldedexcellent average recoveries for both substances (101% for BHAand 99% for BHT), indicating that there were no important matrix

interferences for the samples analyzed by the proposed SWVmethod. Table 1 presents the BHA and BHT concentrations deter-mined simultaneously in the analyzed food products employingthe proposed SWV method and an HPLC method (Perrin et al.,

2002). By analyzing the results obtained for the seven commercialfood products (Table 1), one can conclude that the values obtainedby the proposed method agree quite well with those obtained bythe reference HPLC method. Applying the paired t-test to the re-

sults obtained by both methods, the resulting t values (0.128 forBHA and 0.232 for BHT) are smaller than the critical one (2.31,

a = 0.05), indicating that there is no difference between the ob-

tained results, at a confidence level of 95%.

4. Conclusions

The obtained results allow concluding that SWV along with acathodically pre-treated BDD electrode can be used with somebenefits for the quantitative determination of BHA and BHT, alone

or mixed as commonly found in food products. Very low detectionlimits were obtained in the simultaneous determination of BHA

(0.14 lmol L1) and BHT (0.25 lmol L1); these values are lowerthan the ones previously reported in the literature using voltam-

metric methods. Besides, addition and recovery studies allowedconcluding that the matrix effect did not present any significantinterference. The concentration values obtained for BHA and BHTare similar to those obtained using a HPLC method. Hence, the

SWV method here reported is effective for the simultaneous deter-

mination of BHA and BHT in food products; furthermore, it is a verysimple, inexpensive, and rapid method.

Acknowledgements

The authors gratefully acknowledge financial support from the

Brazilian funding agencies FAPESP, CNPq, and CAPES.

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0.0 0.2 0.4 0.6 0.8 1.0

0.0

0.5

1.0

1.5

2.0

0.0

0.2

0.4

0.6

0.8

1.0

Ip/

[BHT] / 10-6

mol L-1

(B)

0 2 4 6 8 1 0

0 2 4 6 8 1 00.0

0.5

1.0

1.5

2.0

2.5

Ip/

[BHA] / 10-6

mol L-1

(A)

I/


1

12

Fig. 5. SWV curves obtained for the oxidation of BHA and BHT. The concentrations

of both BHA and BHT were equal and changed simultaneously (212): 0.60

10 lmol L1. Inset: the respective analytical curves for BHA (A) and BHT (B).

Supporting electrolyte: aqueous-ethanolic (30% ethanol, v/v) 10 mmol L1 KNO3solution (pHcond. 1.5).

Table 1

Results obtained in the simultaneous determination of BHA and BHT in food products

by HPLC and the proposed method (SWV).

Samples BHA (mg/100 g) BHT (mg/100 g) BHA BHT

Mayonnaise HPLCa SWVa HPLCa SWVa Error

(%)bError

(%)b

1 2.0 0.1 1.9 0.1 1.1 0.1 1.1 0.1 5.0 0

2 1.7 0.2 1.7 0.1 1.3 0.2 1.2 0.2 0 7.7

3 2.3 0.2 2.2 0.2 1.8 0.2 1.7 0.2 4.3 5.5

4 2.3 0.1 2.3 0.1 1.4 0.2 1.5 0.1 0 7.4

5 1.9 0.1 1.8 0.1 1.6 0.2 1.6 0.2 5.2 0

Margarine

6 n.d.c n.d.c 4.2 0.2 4.0 0.2 4.8

7 n.d.c n.d.c 3.8 0.2 3.7 0.1 2.6a Average of three measurements.b Error (%) = 100 (SWV valueHPLC value)/HPLC value.c n.d. = not detected.

890 R.A. Medeiros et al. / Food Chemistry 123 (2010) 886891
http://www.anvisa.gov.br/http://www.anvisa.gov.br/http://www.anvisa.gov.br/http://www.who.int/ipcs/food/jecfa/en/index.htmlhttp://www.who.int/ipcs/food/jecfa/en/index.htmlhttp://www.who.int/ipcs/food/jecfa/en/index.htmlhttp://www.who.int/ipcs/food/jecfa/en/index.htmlhttp://www.anvisa.gov.br/http://www.anvisa.gov.br/


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