This article was downloaded by: [Michigan State University]On: 04 February 2015, At: 16:37Publisher: Taylor & FrancisInforma Ltd Registered in England and Wales Registered Number:1072954 Registered office: Mortimer House, 37-41 Mortimer Street,London W1T 3JH, UK

Analytical LettersPublication details, including instructions forauthors and subscription information:http://www.tandfonline.com/loi/lanl20

The Resolution of DyeBinary Mixtures byBivariate Calibration UsingSpectrophotometric DataP. L. López-de-Alba a , L. López-Martínez a , K.Wróbel-Kaczmarczyk a , K. Wróbel-Zasada a & J.Amador-Hernández aa Instituto de Investigaciones Científicas ,Universidad de Guanajuato , 36000, MéxicoPublished online: 22 Aug 2006.

To cite this article: P. L. López-de-Alba , L. López-Martínez , K. Wróbel-Kaczmarczyk , K. Wróbel-Zasada & J. Amador-Hernández (1996) The Resolutionof Dye Binary Mixtures by Bivariate Calibration Using Spectrophotometric Data,Analytical Letters, 29:3, 487-503, DOI: 10.1080/00032719608000413

To link to this article: http://dx.doi.org/10.1080/00032719608000413

PLEASE SCROLL DOWN FOR ARTICLE

Taylor & Francis makes every effort to ensure the accuracy of allthe information (the “Content”) contained in the publications on ourplatform. However, Taylor & Francis, our agents, and our licensorsmake no representations or warranties whatsoever as to the accuracy,completeness, or suitability for any purpose of the Content. Any opinionsand views expressed in this publication are the opinions and views ofthe authors, and are not the views of or endorsed by Taylor & Francis.The accuracy of the Content should not be relied upon and should beindependently verified with primary sources of information. Taylor andFrancis shall not be liable for any losses, actions, claims, proceedings,demands, costs, expenses, damages, and other liabilities whatsoever

or howsoever caused arising directly or indirectly in connection with, inrelation to or arising out of the use of the Content.

This article may be used for research, teaching, and private studypurposes. Any substantial or systematic reproduction, redistribution,reselling, loan, sub-licensing, systematic supply, or distribution in anyform to anyone is expressly forbidden. Terms & Conditions of accessand use can be found at http://www.tandfonline.com/page/terms-and-conditions

Dow

nloa

ded

by [

Mic

higa

n St

ate

Uni

vers

ity]

at 1

6:37

04

Febr

uary

201

5

ANALYTICAL LETTERS, 29(3), 487-503 (1996)

THE RESOLUTION OF DYE BINARY MIXTURES BY BIVARIATE

CALIBRATION USING SPECTROPHOTOMETFUC DATA

Key Words: Bivariate Calibration, Dye Mixtures, Spectrophotometry

Ldpez-de-Alba, P. L. *, Ldpez-Martinez, L., Wrdbel-Kaczmrczyk, K.,

Wrdbel-Zasada, K., and Amador-Herndndez, J.

Instituto de Investigaciones Cientificas, Universidad de Guanajuato, 36000

Mexico

ABSTRACT

A new, simple spectrophotometric method for resolution of dye binary mixtures is

proposed in this work. A simple mathematical algorithm was designed, in which the data

are used from four linear regression calibration equations: two calibrations for each

component at two selected wavelengths. The method of Kaiser was applied for the

selection of the optimum two-wavelength sets for all mixtures under study. The recovery

experiments were carried out in ten mixtures of the following dyes: Tartrazine, Amaranth,

Erythrosin B, Sunset Yellow and Allura Red. The obtained results were compared with

the results of a commonly used derivative spectrophotometric procedure (zero-crossing

technique). The statistical evaluation of the method bias was performed and it was

concluded that the proposed methodoloa may be competitive with the derivative

procedure for the resolution of such dye binary mixtures.

* Author to whom the correspondence should be addressed.

487

Copyright @ 1996 by Marcel Dekker, Inc.

Dow

nloa

ded

by [

Mic

higa

n St

ate

Uni

vers

ity]

at 1

6:37

04

Febr

uary

201

5

4xx LOPEZ-DE-ALBA ET AL

INTRODUCTION

Several natural and artificial dyes are widely used as alimentary additives. For

many commercial products, two or more different dyes are added and legislation exists

to control the quality of such dyes and their content in the alimentay products'**. Thus,

analytical procedures are needed to rapidly and reliably determine the dyes in food

products. Spectrophotometric methods are most frequently used for such purposes. For

the simultaneous spectrophotometric determination of two sample components, the choice

of an analytical procedure is strictly related to the observed resolution between the

individual absoi-ption peaks of these components. Such a determination is not

problematic, if the absoi-ption peaks are satisfactorily resolved, but if the individual

component signals are partly or totaly overlapped, then chemometric techniques are

needed. There exist several powerful, well established multivariate calibration techniques

which can be used in the modem spectrophotometry: classical least squares (CLS),

inverse least squares (ILS). pi-incipal component regression (PCR) or partial least squares

(PLS)'". These techniques have been widely used for the simultaneous determination of

the two or more components of the sample and excellent analytical results have been

reported. On the other hand, derivative spectrophotometry has also been satisfactorily

applied for such kind of analyses6-'*. However, most of the techniques mentioned above

require full-spectrum infonnation and the spectral data have to be processed using highly

specialized software. In many cases, especially for dye mixtures, there is no need to use

such sophisticated and expensive techniques.

In the present work a new, simple procedure is proposed for the resolution of

binary dye mixtures. The recovery experiments results are compared with the results

obtained by commonly used derivative speckophotometric procedure and the method bias

is evaluated.

OUTLINE OF THE BIVARIATE METHOD PROPOSED

ln the ideal (error-fiee conditions), the absoiption of t h o component mixture (A and

B) at one chosen wavelength may be described accoiding to the Lambert-Beer law, by

the equation

Dow

nloa

ded

by [

Mic

higa

n St

ate

Uni

vers

ity]

at 1

6:37

04

Febr

uary

201

5

DYE BINARY MIXTURES 489

A,= Eibc,+ E;bc,, (1)

where: Am is the absorbance value of the mixture at this wavelength; E,, E, are molar

absorption coefficients of components A and B at this wavelength; c,, c, are the molar

concentrations of both components and b is the optical path length.

However, in real conditions, when the individual responses A, and A, are affected by

the analyt~cal and measurement errors, the calibration curve formulas for each component

at one selected wavelength (Ai), are:

A, = mAi' C, + eAi (2)

where: m,, mB, are the slope values of linear regressions; C,, C, are the concentrations

of both components (for practical reasons the concentration units of mg L-' were used in

this work) and e,, e,, are the intercept values, which reflect the differences between the

model and the real system.

If the measurements of the binary mixture are performed at two selected wavelengths

( 1 and 2), we have two equations:

where eml, e,,are the sum of the intercepts of linear calibration at two wavelengths (e,,

= eAi + %,). The resolution of such equations set allows the evaluation of,C an4C

values:

Dow

nloa

ded

by [

Mic

higa

n St

ate

Uni

vers

ity]

at 1

6:37

04

Febr

uary

201

5

400 LOPEZ-DE-ALBA ET A L

This simple mathematic algorithm allows the resolution of the binary mixture by

measuring the absorbance of the mixture at two selected wavelengths and using the

parameters of the linear regression functions evaluated individually for each component

at these same wavelengths

In such a procedure the problem arises of which set of wavelengths should be

selected to assure the best sensitivity and selectivity of the determination. In this work,

the method of Kaiser" was applied for the selection of the optimum wavelengths. A

series of sensitivity matrices, K, was created for each binary mixture:

where mA1, m, are the sensitivity parameters of the component A at two selected

wavelengths (1, 2) and mRI, mRZ are these parameters for the component B. It was decided

to use the values of the linear regression calibration slope evaluated for one component

at h, as the sensitivity factor. The determinants of these matrices were calculated and the

obtained values were used as the optimization criterion: the wavelength set selected was

the one for which the highest matrix determinant value was obtained.

All calculation were performed using a simple GWBASIC program.

EXPERIMENTAL

Appurutus

A Spectronic 3000 Diode Array Milton Roy spectrophotometer with 0.35nm

resolution was used which was coupled to a 486 PC and User data Version 2.01 Milton

Roy Inst. Co software for spectral data acquisition, storage and manipulation. All data

treatment operations were carried out using an Hewlett Packard Vectra 486/66 VL

microcomputer equipped with the GRAMS/386 tm software package, version 3.01A

(Galactic Ind. Co., Salem, USA)

Dow

nloa

ded

by [

Mic

higa

n St

ate

Uni

vers

ity]

at 1

6:37

04

Febr

uary

201

5

DYE BINARY MIXTURES 49 1

Reagents

All chemicals were of analybcal-reagent grade.

The dyes: Tartrazine (FD&C Yellow-5, YS), Amaranth (FD&C Red-2, R2) and

Erythrosin B (FD&C Red-3, R3) were obtained &om Aldrich Chemical Company and the

dyes: Sunset Yellow (FD&C Y6) and Allura Red (FD&C R40) were from "Quimica

I.R.S.A. de Mexico".

The buffer solution (2molL-', pH 4.6) was prepared by mixing acetic acid and

sodium acetate in molar ratio 1: 1 and adjusting pH with hydrochloric acid lmol.L-'.

Stock solutions containing 250mg-L-' of the dye were prepared. These solutions

were stable approximately one month14, the working solutions were prepared daily by

appropriate dilution.

Pure water of Milli-Q class (Labconco) was used throughout.

Procedures

A series of the dye solutions in the concentration range from 1 to 22 mg L-' were

prepared for one-component calibration.

All possible binary mixtures of the five dyes selected were studied: YS-Y6, Y5-

R2, YS-R3, Y5-R40, Y6-R2, Y6-R3, Y6-R40, R2-R3, R2-R40 and R3-R40. For each

mixture a series of ten solutions were prepared, which contained different concentrations

of the components (in the range 2 to 22 mg L" with the exception of R3, for which the

range of 2 to 12 mgL-' was used).

The spectra of all solutions were registered in the spectral range 350-65Om using

the buffer solution (5ml of 2M buffer solution diluted to 25mL) as the reference. The

absorbance values at selected wavelengths were obtained from these spectra.

First derivative spectra were calculated (AA=8.75nm) from the smoothed spectra

(25 experimental points) using the Savitsky-Golay procedure',.

RESULTS AND DISCUSSION

The individual absorption spectra of five dyes under study are presented in Fig. = 1. As can be observed, these spectra are partly overlapped (A,,, = 427.5nm,

Dow

nloa

ded

by [

Mic

higa

n St

ate

Uni

vers

ity]

at 1

6:37

04

Febr

uary

201

5

492 LOPEZ-DE-ALBA ET AL

0.6

0.4

0.2

0.0

350 415 480 545 610 Wavelength, nm

Figure 1. The absoipfion spectra of 1 - Tartraztne (Y5, 14mg L 'j, 2- Amaranth (R2.

ISmgL'), 3 - Erythrosm B (R3, 7mgL'), 4 - Sunset Yellow (Y6, 14mgL'),

5 - Allura Red (R40, 141ngL ') with the buffer solution as a blank

482.0nm,

binary mixtures using conventional methods is impossible.

= 522.0nn-1, Lac: = 527.5nm, = 499.0nm) and the resolution of

The analytical characteristics for one-component determination at wavelengths

corresponding to the absorption maximum were evaluated for Y5, Y6, R2, R3 and R40

and the obtained results are given in Table I . For the binaiy mixtures studies, the

concentration range for each dye was taken according to the linear range of the individual

calibration function.

The two wavelengths sets for the proposed bivariate procedure were selected using

the method of Kaiser. Nine wavelengths were chosen and the ( m , , A- component, i - wavenumber) slope values of the linear regression calibration were estimated for five

Dow

nloa

ded

by [

Mic

higa

n St

ate

Uni

vers

ity]

at 1

6:37

04

Febr

uary

201

5

DYE BINARY MIXTURES

420

427

43 7

449

474

491

511

521

53 1

493

0 17 67 167 667

0 51 I54 668

0 106 630

0 516

0

Table 1. The sensitivities evaluated for Y5 and R2 determination in one-component solutions at

nine selected wavelengths (q-the slope value of linear regression calibration of i-component),

A. m,,E-3 m,E-3

420 43.68 7.37

427

43 7

449

474

49 1

44.26

43 30

38 90

20 28

6 40

7.85

8.84

10.39

18.69

26.43

511 5.59 33.18

521 1.65 34.34

53 1 1.60 33.38

Table 2. Application of the method of Kaiser for the selection of the best wavelengths set: the

absolute values of determinants of sensitivity matrices (K).

a\A. I 420 427 437 449 474 491 511 521 531

1107

1120

1088

962

416

0

1408

I425

1387

1233

568

65

0

1488

1507

1472

1319

666

176

137

0

1446

1465

143 1

1282

647

171

134

0.1

0

Dow

nloa

ded

by [

Mic

higa

n St

ate

Uni

vers

ity]

at 1

6:37

04

Febr

uary

201

5

494 LOPEZ-DE-ALBA ET AL.

Table 3. The analytical characteristics for the dye determination in a one-component solution at

I m a x

Detection Limit I inearity Range

(mgL.') (mg.L-') 12 (a=o 05) Dye

Y5 2 5E-2 2 - 22 0 9999

Y6 16E-2 2 - 2 2 0 9999

R2 3 1E-2 2 - 22 0 9997

R3 6E-3 2 - 12 0 9999

R40 2 OE-2 2 - 22 0 9999

Table 4. The selected two-wavelength sets for the binary mixture resolution by the bivariate

method proposed

Binary Mixture 1, (nm) 1 2 ( 4

Y5 - Y6 427 5 494 1

Y 5 - R 2 427 5 521 8

Y5 -R3 427 5 527 5

Y5 - R40 449 3 484 7

Y 6 - R 2 477 7 531 8

Y6 - R3 492 7 522 5

Y6 - R40 476 6 534 9

R2 - R3 516 7 527 6

R2 - R40 498 8 508 8

R3 - R40 493 8 527 5

Dow

nloa

ded

by [

Mic

higa

n St

ate

Uni

vers

ity]

at 1

6:37

04

Febr

uary

201

5

DYE BINARY MIXTURES 495

Table 5 . Linear regression calibration formulas used for the bivariate algorithm.

Calibration Equations Binary Mixture Component

J.1 J.2

Y5 A = 0.0442.C + 0.0023 A = 0.0049C + 0,0018

Y6 A = 0.0434.C + 0.0049

Y5 A = 0.0020C + 0.0016

R2 A = 0.0343.C + 0.0029

Y5 A = 0.0442.C + 0.0023 A=O

Y5-Y6 A = 0.0203C + 0.0002

A = 0.0442.C + 0.0023

A = 0 0079.C + 0.0005 Y5-R2

Y5-R3 R3 A = 0.0028.C - 0.0008 A = 0.0886.C - 0.0070

Y5 A = 0.01 1OC + 0.0017

R40 A=0.0174C - 0.0014 A=0.0375C +0.0013

Y6 A = 0.0105C + 0.0003

R2 A = 0.0203.C + 0.0018 A = 0.0332.C + 0.0037

Y6 A = 0.0226C + 0.0020

A = 0.0389.C + 0.0022 Y5-R40

A = 0.0448.C + 0.0030 Y6-R2

A = 0.0438.C + 0.0049 Y6-R3

R3 A = 0.0292.C - 0.0039 A=0.0819C - 0.0068

Y6 A = 0.0082C + 0.0002

R40 A 0.0324.C - 0.0002 A = 0.0293.C + 0.0290

R2 A = 0.0340C + 0.0033

A = 0 0445.C + 0.0029 Y6-R40

A = 0 0340.C + 0.0026 R2-R3

R3 A = 0.0652.C - 0.0062 A = 0.0886.C - 0.0070

R2 A = 0.0326.C + 0.0022

R40 A = 0 0408.C + 0.0102 A = 0.0384.C + 0.0193

A = 0 0295.C + 0.0022 R2-R40

R3 A = 0.0298.C - 0.0041 A = 0.0866.C - 0.0071 R3-R40

R40 A = 0.0403C + 0.0074 A = 0.03 14.C + 0.0344

Dow

nloa

ded

by [

Mic

higa

n St

ate

Uni

vers

ity]

at 1

6:37

04

Febr

uary

201

5

496 LOPEZ-DE-ALBA ET AI

Table 6. Recovery results for individual dyes in their binary mixtures obtained using the bivariate

method

Binary Mixtures

Y5 Y6

YS R2

YS R3

YS R40

Y6 K2

Y6 R3

Y6 R40

R 2 R3

R2 R40

R3 R40

Average Recovery Fi SD, %

First Component Second Component

9 0 0 k O 5

9 8 2 k 0 4 9 7 8 * 1 3

9 9 4 i 0 6 9 9 3 * 2 3

9 6 6 i 0 9 9 8 S i 0 9

100 5 + 0 7 9 5 0 k 3 2

101 2 * 0 5 101 4 * 1 9

1 0 2 6 * 10 1 8 6 8 * 8 3

9 6 9 * 0 6 9 7 6 i 2 2

8 9 7 i 7 3 1 0 1 0 1 7 3

100 2 * 0 7

S 8 2 5 3 6 1 0 4 0 i 5 2

dyes at these nine wavelengths (see Table 2, where the results obtained for Y5 and R2 are

presented as an example). Using the obtained data, the sensitivity matrices were created

for each mixture and the respective determinants were calculated. The sensitivity results

obtained for the mixture of Y5 and R2 are presented in Table 3, where it can clearly be

seen that the wavelengths 427 nm and 52 I nm should be used in the bivariate procedure.

The two-wavelength sets evaluated for all dye mixtures under study are given in Table

4. At these selected wavelengths the one-component calibration curves were obtained. For

the linear response range, in each case, the linear regression calibration function (9 >

0.9990) was calculated and q, e, values were taken for the bivariate algorithm (Table 5).

Then, the resolution of the binary mixtures was performed. For each mixture type, the

recovery experiments were carried out in ten solutions containing the two components in

varying concentration ratios (from 1 : 1 1 up to 1 1 : I , and the mixtures containing R3 from

1.6 up to 6 : l ) . In Table 6 the obtained results are presented, where each value was

calculated as the average recoveiy of one component in ten binary solutions prepared. As

Dow

nloa

ded

by [

Mic

higa

n St

ate

Uni

vers

ity]

at 1

6:37

04

Febr

uary

201

5

DYE BINARY MIXTURES 497

0.008

0.004

0.000

-0.004

-0.008

-0.012

350 41 5 480 545 61 0 Wavelength, nrn

Figure 2. The first-derivative spectra of. 1 - Tartrazine (Y5, 14mgL"), 2- Amaranth

(R2, 18mgL-'), 3 - Erythrosin B (R3, 7mgE ), 4 - Sunset Yellow (Y6,

14mgL-'), 5 - Allura Red (R40, 14mgL ) with the buffer solution as a

blank.

can be observed in tlus Table, satisfactory results (recoveries in the range 88 -104%) were

obtained for all binary mixtures.

In further development these same binary mixtures were resolved using the first

derivative spectra (the derivative spectra of all five dyes are given in Figure 2). The zero-

crossing measurement method was applied. The selected wavelengths and the formula of

caIibration function for each component in ten mixtures studied are presented in Table

7. Using the equations obtained, those same recoveiy experiments were repeated, as in

the bivariate procedure. The obtained results are presented in Table 8. In this case, poorer

Dow

nloa

ded

by [

Mic

higa

n St

ate

Uni

vers

ity]

at 1

6:37

04

Febr

uary

201

5

4Y8 LOPEZ-DE-ALBA ET AL

Table 7. The calibration formulas for the individual dyes in their binary mixtures obtained using

the zero-crossing method for the derivative spectra.

Binary Mixture Component h(nm) Calibration Equation ?(a=0.05)

Y5-Y6

Y5-R2

Y5-R3

Y5-R40

Y6-R2

Y6-R3

Y6-R4O

R2-R3

R2-R40

Y5

Y6

Y5

R2

Y5

R3

Y5

R40

Y6

R2

Y6

R3

Y6

R40

R2

R3

R2

R40

R3

482 7

536 8

377 0

572 9

382 7

539 3

49s 8

553 2

522 I

575 5

572 2

482 7

49s 8

575 4

576 9

522 I

498 8

522 1

49s 8 R3-R40

R40 527 + 572 ID = -2.709E-4.C - 3 65E-5

'D = -3 047E-4.C + 2.88E-5

'D = -2.417E-4.C

ID = 2.190E-4.C - 2.7E-6

'D = -2.266E-4.C - 8.08E-5

'D = 2 110E-4.C - 5.7E-6

'D=-I.5416E-3.C + 1.288E-4

ID = -1 240E-4.C + 8.1E-6

ID = -2.692E-4.C - 4.080E-4

'D = -5.143E-4.C - 6.66E-5

ID = -2 239E-4.C - 8.55E-5

ID = -4.689E-4.C-6 11E-5

ID = 3.587E-4.C-4 85E-5

'D=-9.713E-5.C -1.96E-5

ID = - I 2 18E-4.C + 2.44E-5

ID = -2 21 1E-4.C - 4 11E-5

ID = 7.717E-4.C - 4.09E-5

ID = 1.361E-4.C - 8.8E-6

ID = - 1 2 1 OE-4.C + 9.09E-5

ID = 2.441E-4.C - 5.30E-5

0 9998

0 9994

0 9996

0 9995

0 9996

0 9999

0 9987

0 9924

0 999s

0 9994

0 999s

0 9993

0 9980

0 9981

0 9994

0 9997

0 9991

0 9967

0 9989

0 999s

Dow

nloa

ded

by [

Mic

higa

n St

ate

Uni

vers

ity]

at 1

6:37

04

Febr

uary

201

5

DYE BINARY MIXTURES 499

Table 8. Recovery results for the individual dyes in their binary mixtures (n = 10) obtained using

derivative spectrophotometric method.

Average Recovery Ti SD, %

First Component Second Component

Binary Mixture

Y5 Y6 93.4 f 1.5 104.9 f 3.1

Y5 R2 96.6 f 3.3 90.3 f 7.2

Y5 R3 99.4 f 2.3

Y5 R40 81.0 f 22.3

Y6 R2 98.9 f 0.6

97.3 f 1.0

97.6 f 4.0

96.7 * 8.7

Y6 R3 9 8 0 + 1 5 105 1 f 1 8

Y6 R40 104 8 f 49 6 1 0 8 9 f 9 1

R2 R3 1 1 2 9 1 13 1 9 8 5 5 1 9

R2 R40 1077* 1 6 117 0 f 20 8

R3 R40 1 1 2 9 f 1 6 6 I04 0 f 5 9

average recoveries were obtained (in the range 80-1 13%) as compared with the results

of the bivariate procedure (see Table 6).

To study the observed differences in more detail, the individual recovery results

obtained in ten solutions (containing different dye ratios) were considered for each binary

mixture under study. In Figure 3 the relationship is given between the real and the found

concentrations of Y5 and R40 in their mixture. As can be seen, much better results were

obtained for each composition of the mixture using the bivariate procedure (Fig.3a) than

using common derivative procedure (Fig.3b).

The obtained results suggest that the proposed bivariate procedure could be

competitive to the derivative spectrophotometric method in applications involving the

resolution of dye binary mixtures. The evaluation of method bias was camed out using

statistical tests. The F- and T- tests were performed for the results obtained for each

component in each mixture, and the difference between the results obtained in two

Dow

nloa

ded

by [

Mic

higa

n St

ate

Uni

vers

ity]

at 1

6:37

04

Febr

uary

201

5

500 LOPEZ-DE-ALRA 6T AL

J

I ! 1 n 1 '2 T 16

Figure 3. The relation between the real and the found concentrations of Y5 and R40

in their mixtures: (.4) bivariate procedure

(B) first derivative procedure.

procedures tested were considered statistically significant only in the case when for both

components the t orf value was higher than the theoretical valueI3. First the F-test was

performed, andfq <Aeor ( a=0.05) were found for the mixtures: Y6-R2, Y6-R3, Y6-R40,

Y2-R3, Y2-R40, R3-R40, while for the mixtures: Y5-Y6, YS-W, Y5-R3, Y5-R40,

signifigant differences in precision were detected between both procedures under study.

Better precision is obtained using the bivariate procedure, (see Tables 6 and 8). For the

Dow

nloa

ded

by [

Mic

higa

n St

ate

Uni

vers

ity]

at 1

6:37

04

Febr

uary

201

5

DYE BINARY MIXTURES 50 1 - real c , rug. L-'

Y.5

16 12 8 4 0

12 1; 8 1 4 -

-

0 I I 1 I I I I I

- 0

3 9 - 12

c

- It5

0 4 8 12 16

real cR,, , mg.~- ' .. #

Figure 3. Continued

former group of mixtures, the parametric T-test was applied and for the latter group the

non-paramehic test of Wilcoxon was applied. The results obtained indicate that for the

mixtures Y5-Y6 and Y6-R3 there exists statistically signifigant differences between

results obtained by the two procedures tested (texp > t,e,n). Better recoveries are obtained

by the bivariate procedure (see Tables 6 and 8).

CONCLUSIONS

In this work, a new bivariate procedure was proposed for the resolution of the two-

component mixtures of dyes. The results of the recovery experiments carried out in ten

Dow

nloa

ded

by [

Mic

higa

n St

ate

Uni

vers

ity]

at 1

6:37

04

Febr

uary

201

5

502 LOPEZ-DE-ALBA ET AL.

binary mixtures and the results of the statistical evaluation of method bias indicate that

this procedure may be competitive and, in some cases, even superior to commonly used

first derivative spectrophotometric procedure as applied to the resolution of the binary

mixtures of the dyes. Simplicity is an important advantage of the presented procedure.

There is no need for full-spectrum information and no spectral data processing is

required.

ACKNOWLEDGEMENTS

The authors gratefully acknowledge financial support from the CONACyT

(MCxico), project 3 179-E9307.

REFERENCES

1. T. E. Furia, Handbook of Food Additives, CRC Press Inc., 2nd Ed., Boca Raton, Florida

(1980)

2. R. L. Hall, Flavor Research and Food Acceptance, Reinhold Publishing Co., New York

(1958).

3. P. M. Fredericks, J. B. Lee, P. R. Osborn and D. A. J. Swinkels, AppZ. Spectrosc., 39,303

(1985).

4. D. Haaland and E. V. Thomas, Anal. Chem., 60, 1193 (1988)

5 . D. Haaland and E. V. Thomas, Anal. Chem., 60, 1202 (1988).

6. F. Salinas, A. Espinosa-Mansilla and P. L. Lopez-de-Alba, Analius, 22, 188 (1994).

7. P. L. Lbpez-de-Alba and L. Lopez-Martinez, 1 Rudiounul. NucZ. Chem., Letters 164 (5 ) , 309

(1 992).

8. J. A. Murillo, J. Rodriguez, J. M. Lemus and A. Alaiion, Analyst, 115, 1 117 (1990).

Dow

nloa

ded

by [

Mic

higa

n St

ate

Uni

vers

ity]

at 1

6:37

04

Febr

uary

201

5

DYE BINARY MIXTURES 503

9. M. Martinez Galera, J. L. Martinez Vidal and A. Garrido Frenich, Talanfu, 41, 1545 (1994).

10. T. Galeano Dim, L. Lopez-Martinez and F. Salinas Lopez, Microchem. Jour., 48 (1993).

11. A. Espinosa-Mansilla, A. Mufioz de la PeAa, F. Salinas and A. Zamoro, Anal. Chim. Acta,

258, 47 (1992).

12. I. Dol, M. Kochen and C. Altesor, Analyst, 116, 69 (1991)

13. D. L. Massart, B. G. M. Vandeginste, S. N Deming, Y. Michotte and L. Kaufman,

Chemometrics: a textbook, Elsevier, Amsterdam, 124 (1988).

14. S. Flores Montiel, Determinucion de colorantes sinteficos en alimenfos, Degree Licenciature,

Faculty of Chemistry, Guanajuato University, pp 149, November 1983.

15. A. Savitzky and M. J. E. Golay, Anal. Chem., 36, 1627 (1964)

Received: 22 August, 1995

Accepted: 20 October, 1995

Dow

nloa

ded

by [

Mic

higa

n St

ate

Uni

vers

ity]

at 1

6:37

04

Febr

uary

201

5