the spectrophotometric multicomponent analysis of a ternary

Hindawi Publishing CorporationJournal of SpectroscopyVolume 2013 Article ID 405210 7 pageshttpdxdoiorg1011552013405210

Research ArticleThe Spectrophotometric Multicomponent Analysis ofa TernaryMixture of Paracetamol Aspirin and Caffeine bythe Double Divisor-Ratio Spectra Derivative Method

Reza Hajian1 and Ahmad Soltaninezhad2

1 Young Researchers Club Gachsaran Branch Islamic Azad University 7581863876 Gachsaran Iran2Chemistry Department Gachsaran Branch Islamic Azad University 7581863876 Gachsaran Iran

Correspondence should be addressed to Reza Hajian hajianiaugacir

Received 25 October 2012 Accepted 10 December 2012

Academic Editor Roohollah Torabi Kachoosangi

Copyright copy 2013 R Hajian and A Soltaninezhad is is an open access article distributed under the Creative CommonsAttribution License which permits unrestricted use distribution and reproduction in any medium provided the original work isproperly cited

Double divisor-ratio spectra derivative method based on the spectrophotometric data was developed for the simultaneous analysisof a ternary mixture containing paracetamol aspirin and caffeine without prior separationis method is based on the use of thederivative of the ratio spectrum obtained by dividing the absorption spectrum of the ternary mixture by a standard spectrum of amixture of two of the three compounds in the titlemixturee concentrations of three compounds in theirmixture are determinedby using their respective calibration graphs which are obtained by measuring the amplitude at either the maximum or minimumwavelengths selectede selectedwavelengths for determination of aspirin caffeine and paracetamol are 2415 256 and 2585 nmrespectively All of the solutions adjusted to pH11 before recording the spectra in the range of 220 to 320 nmAlso themathematicalexplanation of the procedure is illustrated e method was applied for the assay of Excedrin containing paracetamol aspirin andcaffeine

1 Introduction

For the simultaneous determination of two or more activecompounds in the same mixtures without a separationstep several spectrophotometric methods such as classicalderivative spectrophotometry [1ndash4] Vierordtrsquos method [5]and its modied version [6] orthogonal function method[7] dual wavelength spectrophotometry [8ndash10] pH-induceddifferential spectrophotometry [11] the least square method[12] the multicomponent analysis program [13 14] anda method and multiwavelength linear regression analysis(MLRA)whichwas referred to byBlanco and co-workers [15]have been utilized

Salinas et al [16] and Nevado et al [17] developed twomethods for the resolution of two or more compounds inmixtures by ratio spectra derivative spectrophotometry andthe derivative ratio spectra-zero crossing method Salinasrsquomethod is based on the use of the derivative of the ratio

spectra for a binary mixture e absorption spectrum of themixture is divided by the absorption spectrum of one of thecompounds and the rst derivative of the ratio spectrum isobtained e concentrations of active compounds are thendetermined from the calibration graphs obtained by measur-ing the amplitudes at points corresponding to the minimumor maximum wavelengths In Berzas Nevadorsquos method thesimultaneous determinations of three compounds in ternarymixtures are based on the measurements of the amplitude atthe zero crossing points in the derivative spectrumof the ratiospectra

In the present research a sensitive selective accurateand inexpensive procedure was applied for simultaneousdetermination of paracetamol (PAR) aspirin (ASP) andcaffeine (CAF) by double divisor-ratio spectra derivativemethod with simultaneous standard additions of three ana-lytes is method is a novel standard addition methodbased on the derivative of the ratio spectra concept In this

2 Journal of Spectroscopy

paper an attempt was made to calculate the derivative of thedouble divisor-ratio spectra and attribute them to the analyteconcentration using spectrophotometry technique

2 Experimental

21 Reagents Paracetamol aspirin and caffeine were kindlyprovided by the Iranian Pharmaceutical Companies (TehranIran) Analytical grade phosphoric acid boric acid aceticacid and sodium hydroxide were supplied from Merck(Darmstadt Germany) All other reagents were of analyticalgrade Britton-Robinson (B-R) buffer (01mol Lminus1) in the pHrange of 2ndash10 was used throughout

A 10 times 10minus3mol Lminus1 paracetamol solution was prepareddaily by dissolving 00074 g PAR (990) in ethanol (96)and was diluted in a 100mL volumetric ask to the markA 10 times 10minus3mol Lminus1 aspirin solution was prepared daily bydissolving 00090 g of ASP (995) in ethanol (96) anddiluted in a 100mL volumetric ask A 10 times 10minus3mol Lminus1caffeine solution was prepared daily by dissolving 00097 gof CAF (995) in double distilled water and diluted intoa 100mL volumetric ask ese solutions were kept ina refrigerator at 4∘C in dark More dilute solutions wereprepared by serial dilutions with double distilled water

22 Instrumentation and Soware UV-visible absorptionspectra were recorded by a spectrophotometer (PerkinElmer) model Lambda 25 with the use of 10 cm quartz cells

A Pentium IV (253GHz) computer controlled all thesetting and data processing e spectrum of each solutionwere recorded in the wavelength range of 200ndash320 nm andsaved as text les Double divisor-ratio derivative spectracalculated in Excel (2007) program

A pH-meter (Metrohm Model 827) with a double junc-tion glass electrode was used to adjust the pH of the solutions

23 Preparation of Real Samples To assay Excedrin tabletcontaining paracetamol (325mg) aspirin (325mg) and caf-feine (65mg) in each tablet the content of ve tablets aremixed together e quantity of 00203 g of the powderwas accurately weighted and then dissolved in 100mL ofethanol (96) Aer being mixed completely the solutionwas diluted to the mark with ethanol is solution was keptin refrigerator at 4∘C

24 General Procedure e general procedure for the anal-ysis of PAR ASP and CAF in a ternary mixture was asfollows To approximately 10mL of sample solution in a100mL volumetric ask 10mL B-R buffer (pH 110) isadded and the nal volume was diluted to the mark withdouble distilled water aer successive standard additions ofthe three components (PAR IBU and CAF) at the samemole ratio For simultaneous determination of PAR ASPand CAF the spectra of ternary mixture aer each standardaddition divided to the standard binary samples of ASP +CAF CAF + PAR and PAR+ASP in the same concentrationsof 20 120583120583mol Lminus1 for each species en the ratio spectra weretransformed to Matlab soware and converted to derivative

0

004

008

012

016

02

220 240 260 280 300 320

Ab

sorb

ance

(A) (B)(C)

Wavelength (nm)

F 1 Absorption spectra of aspirin 50 120583120583mol Lminus1 (a) caffeine20 120583120583mol Lminus1 (b) paracetamol 20 120583120583mol Lminus1 (c) at B-R buffer pH 110

0

02

04

06

08

1

Ab

sorb

ance

12345

6

220 240 260 280 300 320

Wavelength (nm)

F 2 e spectra of the ternary mixture aer addition ofstandards ASP CAF and PAR in the same mole ratios in theconcentration range of 10ndash60 120583120583mol Lminus1 for spectra 1ndash6 e initialsolution contains a ternary mixture of ASP (50 120583120583mol Lminus1) CAF(20 120583120583mol Lminus1) and PAR (20 120583120583mol Lminus1)

ratio spectra and the values of PAR ASP and CAF in theternary mixtures were determined by standard addition plotsat wavelengths 2585 2415 and 256 nm respectively

For better understanding this phenomenon let us con-sider a mixture of PAR ASP and CAF in the same concentra-tion of 100 120583120583mol Lminus1 for each component To determine ASPin the presence of PAR andCAF the absorption spectra of theternary mixture aer successive standard additions of threecomponents were prepared (Figure 2) and divided by thespectrum of the standard mixture solution of PAR and CAF(20 120583120583mol Lminus1 each in B-R buffer) and the ratio spectra wereplotted (Figure 3) e rst derivatives of the ratio spectrawere plotted with Δ120582120582 120582 120582 nm (Figure 4) e amount ofASPwas determined bymeasuring the amplitude at 2415 nmcorresponding to a minimum in the rst derivative of theratio spectra in the spectral region selected (Figure 5)

25 Double Divisor-Ratio Spectra Derivative Method Asshown in Figure 1 the absorption spectra of paracetamolaspirin and caffeine overlapped in the wavelength range of220ndash320 nm erefore double divisor-ratio spectra deriva-tive method proposed for simultaneous determination of

Journal of Spectroscopy 3

0

2

4

6

8

10

12

14

16

18

20

1

2

3

4

5

6

200 210 220 230 240 250 260 270 280

Wavelength (nm)

CA

F

F 3 Double divisor of the ratio spectra for a ternarymixture of aspirin caffeine and paracetamol aer simultaneousstandard addition of three components in the concentration rangeof 10ndash60 120583120583mol Lminus1 (1ndash6) Double divisors concentrations are CAF20 120583120583mol Lminus1 + PAR 20 120583120583mol Lminus1 All of the conditions are as Figure2

0

05

1

15

200 210 220 230 240 250 260 260 280

Wavelength (nm)

minus15

minus1

minus05

F 4 First-derivative double divisor-ratio spectra for a ternarymixture of aspirin caffeine and paracetamol aer simultaneousstandard addition of three components in the concentration rangeof 10ndash60 120583120583mol Lminus1 Δ120582120582 120582 120582120582120582 nm All of the conditions are as Figure3

0 5 10 15 20 25 30 35 40 45

minus06minus07minus08minus09minus1minus11minus12minus13minus14

F 5 Standard addition plot for the derivative of double divisor-ratio spectra for amixture of ASP (50 120583120583mol Lminus1) CAF (20 120583120583mol Lminus1)and PAR (20 120583120583mol Lminus1) aer standard addition of three compo-nents in the same mole ratios in the concentration range of10ndash60 120583120583mol Lminus1 e initial solution contains a ternary mixture ofASP (50 120583120583mol Lminus1) CAF (20 120583120583mol Lminus1) and PAR (20 120583120583mol Lminus1)

compounds in ternary samples If Beerrsquos law is obeyed for allcompounds over the whole wavelength range used and if thepath length is 1 cm the absorption spectrum of the ternarymixture can be written in the form of the following equation

119860119860119898119898119898120582120582119894119894 120582 120576120576PAR119898120582120582119894119894119862119862PAR + 120576120576ASP119898120582120582119894119894119862119862ASP + 120576120576CAF119898120582120582119894119894119862119862CAF119898 (1)

where 119860119860119898119898119898120582120582119894119894 is the absorbance of the mixture at wavelength120582120582119894119894 and 120576120576PAR 120576120576ASP and 120576120576CAF are the absorptivities of PAR ASPandCAF respectively A similar equation for two compoundsin the same ternary mixture as in a standard binary mixturecan be written as

119860119860119898119898119898120582120582119894119894 120582 120576120576ASP119898120582120582119894119894119862119862120582ASP + 120576120576CAF119898120582120582119894119894119862119862

120582CAF120582 (2)

If (1) is divided by (2) corresponding to the spectrum ofa standard solution of two of the components in the ternarymixture the ratio spectrum is obtained in

119860119860119898119898119898120582120582119894119894

120576120576ASP119898120582120582119894119894119862119862120582ASP + 120576120576CAF119898120582120582119894119894119862119862

120582CAF

120582120576120576ASP119898120582120582119894119894119862119862ASP + 120576120576CAF119898120582120582119894119894119862119862CAF

120576120576ASP119898120582120582119894119894119862119862120582ASP + 120576120576CAF119898120582120582119894119894119862119862

120582CAF

+120576120576PAR119862119862PAR

120576120576ASP119898120582120582119894119894119862119862120582ASP + 120576120576CAF119898120582120582119894119894119862119862

120582CAF

120582

(3)

e ratio of the sum of 120576120576ASP119898120582120582119894119894119862119862ASP and 120576120576CAF119898120582120582119894119894119862119862CAF

to the sum of 120576120576ASP119898120582120582119894119894119862119862120582ASP and 120576120576CAF119898120582120582119894119894119862119862

120582CAF is equal to a

constant (119896119896119896 with respect to 120582120582 in a certain region or pointof wavelength ese coinciding points of the derivative ofthe ratio spectra can be selected as working wavelengths forthe determinations of the subject compounds in the ternarymixture If the above constant is replaced in (3) we obtain

119860119860119898119898119898120582120582119894119894

120576120576ASP119898120582120582119894119894119862119862120582ASP + 120576120576CAF119898120582120582119894119894119862119862

120582CAF

120582 119896119896 +120576120576PAR119862119862PAR

120576120576ASP119898120582120582119894119894119862119862120582ASP + 120576120576CAF119898120582120582119894119894119862119862

120582CAF

120582

(4)

However if the standard concentrations of119862119862120582ASP and119862119862

120582CAF in

(2) are equal or very close to each other we could write

120576120576ASP119898120582120582119894119894119862119862120582ASP + 120576120576CAF119898120582120582119894119894119862119862

120582CAF 120582 119862119862120582

CAF 10077141007714120576120576ASP119898120582120582119894119894 + 120576120576CAF119898120582120582119894119894 10077301007730 120582 (5)

Substituting (5) into (4) (6) is derived as follows

119860119860119898119898119898120582120582119894119894

120576120576ASP119898120582120582119894119894119862119862120582ASP + 120576120576CAF119898120582120582119894119894119862119862

120582CAF

120582 119896119896 +120576120576PAR119894119894

119862119862PAR

119862119862120582CAF 10077141007714120576120576ASP119898120582120582119894119894 + 120576120576CAF119898120582120582119894119894 10077301007730

120582

(6)

If the rst derivative of (6) is taken since the derivative of aconstant is zero (7) will be obtained as follows

119889119889119889119889120582120582

10077191007719119860119860119898119898119898120582120582119894119894

119862119862120582CAF 10077141007714120576120576ASP119898120582120582119894119894 + 120576120576CAF119898120582120582119894119894 10077301007730

10077351007735

120582119889119889119889119889120582120582

10077191007719120576120576PAR

10076501007650120576120576ASP119898120582120582119894119894 + 120576120576CAF119898120582120582119894119894 1007666100766610077351007735119862119862PAR

119862119862120582CAF

120582

(7)


0

005

01

015

02

025

03

035

04

0 2 4 6 8 10 12

pH

ASP

CAF

PAR

Absorbance

(a)

pH

220

240

260

280

300

1 2 3 4 5 6 7 8 9 10 11 12

ASP

CAF

PAR

(b)

F 6 Effect of pH on the sensitivity (a) and selectivity (b) of the spectra of ASP CAF and PAR All of the conditions are as Figure 1

T 1 Replicative determination of paracetamol aspirin and caffeine in some ternary mixtures by double divisor-ratio spectra derivativemethod

Mixture Added (120583120583mol Lminus1) Found (120583120583mol Lminus1) RSD ()PAR ASP CAF PAR ASP CAF PAR ASP CAF30 30 30 2908 2881 3106

1 30 30 30 2894 2919 3091 258 188 27430 30 30 3032 2990 295430 50 40 3201 4870 3884

2 30 50 40 3003 5001 3807 330 142 15430 50 40 3150 4980 395020 8 10 1808 808 1010

3 20 8 10 2193 799 998 456 058 57320 8 10 2090 801 908

Equation (7) is the mathematical foundation of multi-component analysis which permits the determination of theconcentration of each of the active compounds in solutionwithout interference from the other components of theternary system In practice (7) corresponding to the rstderivative ratio spectrum of PAR is obtained by dividing theabsorption spectrum of the ternarymixture of PAR ASP andCAF by the standard spectrum of two of the compounds inthe ternary mixture Also in (7) the derivative signal of theratio spectrum of the ternary mixture is dependent only onthe concentration values of PAR and 1198621198620CAF but is indepen-dent of the concentration values119862119862ASP and119862119862CAF in the ternarymixture In the developedmethod the concentration of119862119862PARin the ternary mixture is proportional to the rst derivativesignals corresponding to a maximum or minimum point

e double divisor spectra of binary mixtures calculatedas the following steps

(a) A standard binary mixture of analytes added to theunknown sample and recorded its spectrum

(b) e spectrum of unknown sample recorded in thewavelength range of 220 to 320 nm

(c) e spectrum of double divisor in the presence ofmatrix effect calculated by the subtract the spectrumof step ldquobrdquo from step ldquoardquo

e stored spectra of the ternary mixture are divided bythe spectrum of double divisors aer addition of pure PARusingMATLAB sowareederivative of the ratio spectra atwavelength 2585 nmplotted against standard concentrationsof PAR As explained here this technique can be used fordetermination of other compounds in the ternary mixtureusing other double divisors containing PAR + CAF and PAR+ ASP for the determination of ASP and CAF respectivelyIn this research simultaneous standard additions of threecompounds of PAR ASP and CAF into the ternary mixturepresented and the analysis of PAR ASP and CAF is alsoapplicable using the doubled divisor-ratio derivative methodfor the rst time is technique is very simple and fast incomparison with the individual standard addition method

3 Results and Discussions

e absorption spectra of the three compounds PAR ASPand CAF overlapped closely in the region 220ndash320 nm inFigure 1 For this reason the determination of the above


T 2 Determination of aspirin caffeine and paracetamol in some ternary mixtures

Mixture Added (120583120583mol Lminus1) Found (120583120583mol Lminus1) Recovery ()ASP CAF PAR ASP CAF PAR ASP CAF PAR

1 200 300 400 1990 2985 4017 995 995 100432 200 100 100 1971 990 1007 9855 9900 100703 100 200 80 1000 1958 803 1000 9790 100384 300 100 80 2985 1000 801 9950 10000 100135 400 200 300 3928 1996 3033 9820 9980 101106 500 500 500 1517 5074 5000 3034 10148 100007 600 300 300 6022 3001 3101 10037 10003 103378 700 300 200 7017 2998 2052 10024 9993 102609 100 100 100 998 1036 1070 9980 10360 1070010 100 300 500 906 2912 5223 9060 9707 10446

T 3 Determination of paracetamol aspirin and caffeine in Excedrin tablets by the proposed method

Samplelowast Added (mg) Found (mg) Recovery ()PAR ASP CAF PAR ASP CAF PAR ASP CAF

Brand I mdash mdash mdash 32578 6650 33151 10024 10230 102008850 6500 6513 40899 12870 32270 10600 9560 9400

Brand II mdash mdash mdash 32948 6695 32893 10137 10300 1012023722 19500 19657 57408 27365 53140 10311 10600 10300

Average 10268 10172 10005RSD () 244 431 410lowastBrands 1 and 2 are Excedrin tablets containing paracetamol (325mg) aspirin (325mg) and caffeine (65mg) in each tablet from Bristol-Meys Squibb andNovartis Consumer Health companies for brands 1 and 2 respectively

0

005

01

015

02

025

03

200 220 240 260 280 300 320minus005

minus01

minus015

minus02

a1

a2

b1

b2

c1

c2

Wavelength (nm)

F 7 e coincident spectra of the rst derivative of theratio spectra of (a1) 20 120583120583mol Lminus1 pure ASP and (a2) ternary mix-ture of 20 120583120583mol Lminus1 ASP 50 120583120583mol Lminus1 CAF 20 120583120583mol Lminus1 PAR and20 120583120583mol Lminus1 CAF + 20 120583120583mol Lminus1 PAR as a double divisor (b1)50120583120583mol Lminus1 pure CAF and (b2) ternary mixture of 20 120583120583mol Lminus1ASP 50 120583120583mol Lminus1 CAF 20 120583120583mol Lminus1 PAR and 20 120583120583mol Lminus1 ASP +20 120583120583mol Lminus1 PAR as a double divisor and (c1) 20 120583120583mol Lminus1 purePAR and (c2) ternary mixture of 20 120583120583mol Lminus1 ASP 50 120583120583mol Lminus1 CAF20120583120583mol Lminus1 PAR and 20 120583120583mol Lminus1 ASP + 20 120583120583mol Lminus1 CAF as adouble divisor

compounds was not possible from direct measurementsof absorbances in the zero-order spectra In this researchdouble divisor-ratio spectra derivative method based on thespectrophotometric data was developed for the simultaneousanalysis of the ternary mixtures containing paracetamolaspirin and caffeine without prior separation

0

001

002

003

004

005

0 5 10 15 20 25 30 35 40 45 50 55 60 65

Cal

ibra

tio

n s

lop

e

c

b

a

F 8 Effect of double divisor concentrations on the slopes ofthe calibration curves of (a) ASP (b) CAF and (c) PAR

31 Optimization of the Parameters In the following theeffective parameters involving pH working wavelengths anddouble devisor concentrations studied on the accuracy of theproposed method

311 Optimization of pH It has been shown that the maxi-mum absorbances for CAF and PAR are independent of thepH of the solution within the pH range of 18 to 110 in termsof sensitivity (Figure 6(a)) e maximum wavelengths forPAR and ASP are close to each other in the range of 18 to80 but at pH gt 80 overlapping spectra between PAR and


ASP decreased therefore B-R buffer at pH 110 was selectedto adjust the pH of solutions before recording the spectra

312 Selection of the Working Wavelengths In the applica-tion of this method the rst derivative of the ratio spectra ofpure compound and its ternary mixture would be coincidedin the spectral region corresponding to amaximumpoint or aminimumpoint of thewavelength as shown in Figure 7esecoinciding points of the derivative of the ratio spectra canbe selected as working wavelengths for the determinationsof the subject compounds in the ternary mixture e bestworking wavelengths selected at 2585 2415 and 256 nmfor determination of paracetamol aspirin and caffeinerespectively

313e Effect of Double Divisor Concentrations Accordingto the theory [16] the concentrations of double divisorsshould be equal but the slope of the calibration graphsproportionally decreased by increasing concentrations ofdivisors (Figure 8)ese results conrm the reliability of theratio spectra method in the present instance According tothe above results concentration of 20 120583120583mol Lminus1 was chosenas the divisor concentrations

32 Figures of Merit To check the reproducibility of theproposed method three replicate experiments for the deter-mination of paracetamol aspirin and caffeine in ternarymixtures have been designed (Table 1) e relative standarddeviation values are in the range of 058 to 573

e limit of detection calculated as LOD = 3119878119878119862119862 [18]where 119878119878119862119862 is the standard deviation of several (119899119899 = 3) repli-catedmeasurement of zero concentration of the analyte usingthe proposed method e corresponding values obtainedwere 046 053 and 068 120583120583mol Lminus1 for PAR ASP and CAFrespectively

e calibration plots were linear in the ranges of04ndash3200 120583120583mol Lminus1 08ndash1600 120583120583mol Lminus1 and 04ndash2600120583120583mol Lminus1 respectively for PAR ASP and CAF with thecorrelation coefficients of 09979 09999 and 09991

33 Application of the Proposed Method in Synthetic andReal Samples In order to evaluate the applicability of theproposed method for the determination of PAR ASP andCAF in real samples the utility of the developed method wastested by determining of the compounds in several model(mixed) samples (Table 2) and pharmaceutical formulations(Table 3) e good recoveries of the spiked samples areindicative of the successful applicability of the proposedmethod for simultaneous determination of paracetamolaspirin and caffeine All of the recoveries in real samples weresatisfactory in the range of 940 to 1060

4 Conclusions

is work formulates a new approach to the simultaneousanalysis of ternary mixtures of paracetamol aspirin andcaffeine which have overlapping spectra In the double

divisor-ratio spectra derivative method for each compoundin ternary mixture without searching for the critical pointfor the separated peaks the maximum amplitude of theseparated peaks can be measured is can be considered asan advantage of the new method over alternative methodsfor the resolution of ternary mixtures Our new method hasgreat promise for the routine determination of two or morecompounds in mixtures and for the analysis of Excedrintablets in control process of products

Conict of nterests

It needs to be mentioned that the Merck materials (phos-phoric acid boric acid acetic acid and sodium hydroxide)were provided to the author by theGachsaran Branch IslamicAzad University where the author work as a member of thefaculty and these materials which are running very low havebeen purchased by the university around the year 2005

Acknowledgments

e authors gratefully acknowledge the support of this workby Islamic Azad University of Gachsaran and the assistanceof Farabi Pharmaceutical Company for donation of purecompounds

References

[1] A T Giese and C S French ldquoe analysis of overlappingspectral absorption bands by derivative spectrophotometryrdquoApplied Spectroscopy vol 9 pp 78ndash96 1955

[2] T C OrsquoHaver and G L Green ldquoNumerical error analysisof derivative spectrometry for the quantitative analysis ofmixturesrdquo Analytical Chemistry vol 48 no 2 pp 312ndash3181976

[3] T C OrsquoHaver ldquoDerivative and wavelength modulation spec-trometryrdquo Analytical Chemistry vol 51 pp 91Andash100A 1979

[4] R Rohilla andU Gupta ldquoSimultaneous determination of cobalt(II) and nickel (II) by rst order derivative spectrophotom-etry in micellar mediardquo E-Journal of Chemistry vol 9 pp1357ndash1363 2012

[5] L Heilmeyer Spectrophotometry in Medicine Adam HilgerLondon UK 1943

[6] A L Glenn ldquoe importance of extinction ratios in the spec-trophotometric analysis of mixtures of two known absorbingsubstancesrdquo e Journal of Pharmacy and Pharmacology vol12 pp 595ndash608 1960

[7] A L Glenn ldquoe use of orthogonal functions to correct forirrelevant absorption in two component spectrophotometricanalysisrdquo e Journal of Pharmacy and Pharmacology vol 15pp 123Tndash130T 1963

[8] S Shibata M Furukawa and K Goto ldquoDual-wavelengthspectrophotometry General methodrdquo Analytica Chimica Actavol 46 no 2 pp 271ndash279 1969

[9] S Shibata M Furukawa and K Goto ldquoDual-wavelengthspectrophotometry e determination of mixturesrdquo AnalyticaChimica Acta vol 53 no 2 pp 369ndash377 1971


[10] S Shibata K Goto and Y Ishiguro ldquoDual-wavelength spec-trophotometrymdashpart III Determination of arsenazo I in arse-nazo IIIrdquo Analytica Chimica Acta vol 62 no 2 pp 305ndash3101972

[11] A M Wahbi and A M Faraghaly ldquoApplication of the ΔAmethod to the determination of morphinerdquo Journal of Phar-macy and Pharmacology vol 22 pp 848ndash850 1970

[12] A M Wahbi H Abdine M A Korany and F A El-YazbildquoSpectrophotometric analysis of binary mixtures of antazolineand naphazolinerdquo Journal of Pharmaceutical Sciences vol 67no 1 pp 140ndash141 1978

[13] Y R Tahboub andH L Pardue ldquoEvaluation ofmultiwavelengthrst- and second-derivative spectra for the quantitation ofmixtures of polynuclear aromatic hydrocarbonsrdquo AnalyticalChemistry vol 57 no 1 pp 38ndash41 1985

[14] D T Rossi and H L Pardue ldquoEffects of wavelength range onthe simultaneous quantitation of polynuclear aromatic hydro-carbons with absorption spectrardquo Analytica Chimica Acta vol175 pp 153ndash161 1985

[15] M Blanco J Gene H Iturriaga S Maspoch and J RibaldquoDiode-array detectors in ow-inection analysis Mixture res-olution by multi-wavelength analysisrdquo Talanta vol 34 no 12pp 987ndash993 1987

[16] F Salinas J J B Nevado and M A Espinosa ldquoA newspectrophotometric method for quantitative multicomponentanalysis resolution ofmixtures of salicylic and salicyluric acidsrdquoTalanta vol 37 no 3 pp 347ndash351 1990

[17] J J B Nevado C G Cabanillas and F Salinas ldquoSpectropho-tometric resolution of ternary mixtures of salicylaldehyde3-hydroxybenzaldehyde and 4-hydroxybenzaldehyde by thederivative ratio spectrum-zero crossing methodrdquo Talanta vol39 no 5 pp 547ndash553 1992

[18] J C Miller and J N Miller Statistics for Analytical ChemistryEllis Horwood New York NY USA 3rd edition 1993

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paper an attempt was made to calculate the derivative of thedouble divisor-ratio spectra and attribute them to the analyteconcentration using spectrophotometry technique

2 Experimental

21 Reagents Paracetamol aspirin and caffeine were kindlyprovided by the Iranian Pharmaceutical Companies (TehranIran) Analytical grade phosphoric acid boric acid aceticacid and sodium hydroxide were supplied from Merck(Darmstadt Germany) All other reagents were of analyticalgrade Britton-Robinson (B-R) buffer (01mol Lminus1) in the pHrange of 2ndash10 was used throughout

A 10 times 10minus3mol Lminus1 paracetamol solution was prepareddaily by dissolving 00074 g PAR (990) in ethanol (96)and was diluted in a 100mL volumetric ask to the markA 10 times 10minus3mol Lminus1 aspirin solution was prepared daily bydissolving 00090 g of ASP (995) in ethanol (96) anddiluted in a 100mL volumetric ask A 10 times 10minus3mol Lminus1caffeine solution was prepared daily by dissolving 00097 gof CAF (995) in double distilled water and diluted intoa 100mL volumetric ask ese solutions were kept ina refrigerator at 4∘C in dark More dilute solutions wereprepared by serial dilutions with double distilled water

22 Instrumentation and Soware UV-visible absorptionspectra were recorded by a spectrophotometer (PerkinElmer) model Lambda 25 with the use of 10 cm quartz cells

A Pentium IV (253GHz) computer controlled all thesetting and data processing e spectrum of each solutionwere recorded in the wavelength range of 200ndash320 nm andsaved as text les Double divisor-ratio derivative spectracalculated in Excel (2007) program

A pH-meter (Metrohm Model 827) with a double junc-tion glass electrode was used to adjust the pH of the solutions

23 Preparation of Real Samples To assay Excedrin tabletcontaining paracetamol (325mg) aspirin (325mg) and caf-feine (65mg) in each tablet the content of ve tablets aremixed together e quantity of 00203 g of the powderwas accurately weighted and then dissolved in 100mL ofethanol (96) Aer being mixed completely the solutionwas diluted to the mark with ethanol is solution was keptin refrigerator at 4∘C

24 General Procedure e general procedure for the anal-ysis of PAR ASP and CAF in a ternary mixture was asfollows To approximately 10mL of sample solution in a100mL volumetric ask 10mL B-R buffer (pH 110) isadded and the nal volume was diluted to the mark withdouble distilled water aer successive standard additions ofthe three components (PAR IBU and CAF) at the samemole ratio For simultaneous determination of PAR ASPand CAF the spectra of ternary mixture aer each standardaddition divided to the standard binary samples of ASP +CAF CAF + PAR and PAR+ASP in the same concentrationsof 20 120583120583mol Lminus1 for each species en the ratio spectra weretransformed to Matlab soware and converted to derivative

0

004

008

012

016

02

220 240 260 280 300 320

Ab

sorb

ance

(A) (B)(C)

Wavelength (nm)

F 1 Absorption spectra of aspirin 50 120583120583mol Lminus1 (a) caffeine20 120583120583mol Lminus1 (b) paracetamol 20 120583120583mol Lminus1 (c) at B-R buffer pH 110

0

02

04

06

08

1

Ab

sorb

ance

12345

6

220 240 260 280 300 320

Wavelength (nm)

F 2 e spectra of the ternary mixture aer addition ofstandards ASP CAF and PAR in the same mole ratios in theconcentration range of 10ndash60 120583120583mol Lminus1 for spectra 1ndash6 e initialsolution contains a ternary mixture of ASP (50 120583120583mol Lminus1) CAF(20 120583120583mol Lminus1) and PAR (20 120583120583mol Lminus1)

ratio spectra and the values of PAR ASP and CAF in theternary mixtures were determined by standard addition plotsat wavelengths 2585 2415 and 256 nm respectively

For better understanding this phenomenon let us con-sider a mixture of PAR ASP and CAF in the same concentra-tion of 100 120583120583mol Lminus1 for each component To determine ASPin the presence of PAR andCAF the absorption spectra of theternary mixture aer successive standard additions of threecomponents were prepared (Figure 2) and divided by thespectrum of the standard mixture solution of PAR and CAF(20 120583120583mol Lminus1 each in B-R buffer) and the ratio spectra wereplotted (Figure 3) e rst derivatives of the ratio spectrawere plotted with Δ120582120582 120582 120582 nm (Figure 4) e amount ofASPwas determined bymeasuring the amplitude at 2415 nmcorresponding to a minimum in the rst derivative of theratio spectra in the spectral region selected (Figure 5)

25 Double Divisor-Ratio Spectra Derivative Method Asshown in Figure 1 the absorption spectra of paracetamolaspirin and caffeine overlapped in the wavelength range of220ndash320 nm erefore double divisor-ratio spectra deriva-tive method proposed for simultaneous determination of


0

2

4

6

8

10

12

14

16

18

20

1

2

3

4

5

6

200 210 220 230 240 250 260 270 280

Wavelength (nm)

CA

F


0

05

1

15

200 210 220 230 240 250 260 260 280

Wavelength (nm)

minus15

minus1

minus05


0 5 10 15 20 25 30 35 40 45






119860119860119898119898119898120582120582119894119894 120582 120576120576ASP119898120582120582119894119894119862119862120582ASP + 120576120576CAF119898120582120582119894119894119862119862

120582CAF120582 (2)


119860119860119898119898119898120582120582119894119894

120576120576ASP119898120582120582119894119894119862119862120582ASP + 120576120576CAF119898120582120582119894119894119862119862

120582CAF

120582120576120576ASP119898120582120582119894119894119862119862ASP + 120576120576CAF119898120582120582119894119894119862119862CAF

120576120576ASP119898120582120582119894119894119862119862120582ASP + 120576120576CAF119898120582120582119894119894119862119862

120582CAF

+120576120576PAR119862119862PAR

120576120576ASP119898120582120582119894119894119862119862120582ASP + 120576120576CAF119898120582120582119894119894119862119862

120582CAF

120582

(3)





119860119860119898119898119898120582120582119894119894

120576120576ASP119898120582120582119894119894119862119862120582ASP + 120576120576CAF119898120582120582119894119894119862119862

120582CAF

120582 119896119896 +120576120576PAR119862119862PAR

120576120576ASP119898120582120582119894119894119862119862120582ASP + 120576120576CAF119898120582120582119894119894119862119862

120582CAF

120582

(4)


120582CAF in


120576120576ASP119898120582120582119894119894119862119862120582ASP + 120576120576CAF119898120582120582119894119894119862119862

120582CAF 120582 119862119862120582

CAF 10077141007714120576120576ASP119898120582120582119894119894 + 120576120576CAF119898120582120582119894119894 10077301007730 120582 (5)


119860119860119898119898119898120582120582119894119894

120576120576ASP119898120582120582119894119894119862119862120582ASP + 120576120576CAF119898120582120582119894119894119862119862

120582CAF

120582 119896119896 +120576120576PAR119894119894

119862119862PAR

119862119862120582CAF 10077141007714120576120576ASP119898120582120582119894119894 + 120576120576CAF119898120582120582119894119894 10077301007730

120582

(6)


119889119889119889119889120582120582

10077191007719119860119860119898119898119898120582120582119894119894

119862119862120582CAF 10077141007714120576120576ASP119898120582120582119894119894 + 120576120576CAF119898120582120582119894119894 10077301007730

10077351007735

120582119889119889119889119889120582120582

10077191007719120576120576PAR

10076501007650120576120576ASP119898120582120582119894119894 + 120576120576CAF119898120582120582119894119894 1007666100766610077351007735119862119862PAR

119862119862120582CAF

120582

(7)


0

005

01

015

02

025

03

035

04

0 2 4 6 8 10 12

pH

ASP

CAF

PAR

Absorbance

(a)

pH

220

240

260

280

300

1 2 3 4 5 6 7 8 9 10 11 12

ASP

CAF

PAR

(b)




1 30 30 30 2894 2919 3091 258 188 27430 30 30 3032 2990 295430 50 40 3201 4870 3884

2 30 50 40 3003 5001 3807 330 142 15430 50 40 3150 4980 395020 8 10 1808 808 1010

3 20 8 10 2193 799 998 456 058 57320 8 10 2090 801 908












1 200 300 400 1990 2985 4017 995 995 100432 200 100 100 1971 990 1007 9855 9900 100703 100 200 80 1000 1958 803 1000 9790 100384 300 100 80 2985 1000 801 9950 10000 100135 400 200 300 3928 1996 3033 9820 9980 101106 500 500 500 1517 5074 5000 3034 10148 100007 600 300 300 6022 3001 3101 10037 10003 103378 700 300 200 7017 2998 2052 10024 9993 102609 100 100 100 998 1036 1070 9980 10360 1070010 100 300 500 906 2912 5223 9060 9707 10446






0

005

01

015

02

025

03

200 220 240 260 280 300 320minus005

minus01

minus015

minus02

a1

a2

b1

b2

c1

c2

Wavelength (nm)



0

001

002

003

004

005

0 5 10 15 20 25 30 35 40 45 50 55 60 65

Cal

ibra

tio

n s

lop

e

c

b

a












4 Conclusions



Conict of nterests


Acknowledgments


References





























Journal of

Chemistry


Advances in

Physical Chemistry



Journal of

Volume 2014














Journal of

Spectroscopy



Journal of


Quantum Chemistry






CatalystsJournal of


0

2

4

6

8

10

12

14

16

18

20

1

2

3

4

5

6

200 210 220 230 240 250 260 270 280

Wavelength (nm)

CA

F


0

05

1

15

200 210 220 230 240 250 260 260 280

Wavelength (nm)

minus15

minus1

minus05


0 5 10 15 20 25 30 35 40 45






119860119860119898119898119898120582120582119894119894 120582 120576120576ASP119898120582120582119894119894119862119862120582ASP + 120576120576CAF119898120582120582119894119894119862119862

120582CAF120582 (2)


119860119860119898119898119898120582120582119894119894

120576120576ASP119898120582120582119894119894119862119862120582ASP + 120576120576CAF119898120582120582119894119894119862119862

120582CAF

120582120576120576ASP119898120582120582119894119894119862119862ASP + 120576120576CAF119898120582120582119894119894119862119862CAF

120576120576ASP119898120582120582119894119894119862119862120582ASP + 120576120576CAF119898120582120582119894119894119862119862

120582CAF

+120576120576PAR119862119862PAR

120576120576ASP119898120582120582119894119894119862119862120582ASP + 120576120576CAF119898120582120582119894119894119862119862

120582CAF

120582

(3)





119860119860119898119898119898120582120582119894119894

120576120576ASP119898120582120582119894119894119862119862120582ASP + 120576120576CAF119898120582120582119894119894119862119862

120582CAF

120582 119896119896 +120576120576PAR119862119862PAR

120576120576ASP119898120582120582119894119894119862119862120582ASP + 120576120576CAF119898120582120582119894119894119862119862

120582CAF

120582

(4)


120582CAF in


120576120576ASP119898120582120582119894119894119862119862120582ASP + 120576120576CAF119898120582120582119894119894119862119862

120582CAF 120582 119862119862120582

CAF 10077141007714120576120576ASP119898120582120582119894119894 + 120576120576CAF119898120582120582119894119894 10077301007730 120582 (5)


119860119860119898119898119898120582120582119894119894

120576120576ASP119898120582120582119894119894119862119862120582ASP + 120576120576CAF119898120582120582119894119894119862119862

120582CAF

120582 119896119896 +120576120576PAR119894119894

119862119862PAR

119862119862120582CAF 10077141007714120576120576ASP119898120582120582119894119894 + 120576120576CAF119898120582120582119894119894 10077301007730

120582

(6)


119889119889119889119889120582120582

10077191007719119860119860119898119898119898120582120582119894119894

119862119862120582CAF 10077141007714120576120576ASP119898120582120582119894119894 + 120576120576CAF119898120582120582119894119894 10077301007730

10077351007735

120582119889119889119889119889120582120582

10077191007719120576120576PAR

10076501007650120576120576ASP119898120582120582119894119894 + 120576120576CAF119898120582120582119894119894 1007666100766610077351007735119862119862PAR

119862119862120582CAF

120582

(7)


0

005

01

015

02

025

03

035

04

0 2 4 6 8 10 12

pH

ASP

CAF

PAR

Absorbance

(a)

pH

220

240

260

280

300

1 2 3 4 5 6 7 8 9 10 11 12

ASP

CAF

PAR

(b)




1 30 30 30 2894 2919 3091 258 188 27430 30 30 3032 2990 295430 50 40 3201 4870 3884

2 30 50 40 3003 5001 3807 330 142 15430 50 40 3150 4980 395020 8 10 1808 808 1010

3 20 8 10 2193 799 998 456 058 57320 8 10 2090 801 908












1 200 300 400 1990 2985 4017 995 995 100432 200 100 100 1971 990 1007 9855 9900 100703 100 200 80 1000 1958 803 1000 9790 100384 300 100 80 2985 1000 801 9950 10000 100135 400 200 300 3928 1996 3033 9820 9980 101106 500 500 500 1517 5074 5000 3034 10148 100007 600 300 300 6022 3001 3101 10037 10003 103378 700 300 200 7017 2998 2052 10024 9993 102609 100 100 100 998 1036 1070 9980 10360 1070010 100 300 500 906 2912 5223 9060 9707 10446






0

005

01

015

02

025

03

200 220 240 260 280 300 320minus005

minus01

minus015

minus02

a1

a2

b1

b2

c1

c2

Wavelength (nm)



0

001

002

003

004

005

0 5 10 15 20 25 30 35 40 45 50 55 60 65

Cal

ibra

tio

n s

lop

e

c

b

a












4 Conclusions



Conict of nterests


Acknowledgments


References





























Journal of

Chemistry


Advances in

Physical Chemistry



Journal of

Volume 2014














Journal of

Spectroscopy



Journal of


Quantum Chemistry






CatalystsJournal of


0

005

01

015

02

025

03

035

04

0 2 4 6 8 10 12

pH

ASP

CAF

PAR

Absorbance

(a)

pH

220

240

260

280

300

1 2 3 4 5 6 7 8 9 10 11 12

ASP

CAF

PAR

(b)




1 30 30 30 2894 2919 3091 258 188 27430 30 30 3032 2990 295430 50 40 3201 4870 3884

2 30 50 40 3003 5001 3807 330 142 15430 50 40 3150 4980 395020 8 10 1808 808 1010

3 20 8 10 2193 799 998 456 058 57320 8 10 2090 801 908












1 200 300 400 1990 2985 4017 995 995 100432 200 100 100 1971 990 1007 9855 9900 100703 100 200 80 1000 1958 803 1000 9790 100384 300 100 80 2985 1000 801 9950 10000 100135 400 200 300 3928 1996 3033 9820 9980 101106 500 500 500 1517 5074 5000 3034 10148 100007 600 300 300 6022 3001 3101 10037 10003 103378 700 300 200 7017 2998 2052 10024 9993 102609 100 100 100 998 1036 1070 9980 10360 1070010 100 300 500 906 2912 5223 9060 9707 10446






0

005

01

015

02

025

03

200 220 240 260 280 300 320minus005

minus01

minus015

minus02

a1

a2

b1

b2

c1

c2

Wavelength (nm)



0

001

002

003

004

005

0 5 10 15 20 25 30 35 40 45 50 55 60 65

Cal

ibra

tio

n s

lop

e

c

b

a












4 Conclusions



Conict of nterests


Acknowledgments


References





























Journal of

Chemistry


Advances in

Physical Chemistry



Journal of

Volume 2014














Journal of

Spectroscopy



Journal of


Quantum Chemistry






CatalystsJournal of




1 200 300 400 1990 2985 4017 995 995 100432 200 100 100 1971 990 1007 9855 9900 100703 100 200 80 1000 1958 803 1000 9790 100384 300 100 80 2985 1000 801 9950 10000 100135 400 200 300 3928 1996 3033 9820 9980 101106 500 500 500 1517 5074 5000 3034 10148 100007 600 300 300 6022 3001 3101 10037 10003 103378 700 300 200 7017 2998 2052 10024 9993 102609 100 100 100 998 1036 1070 9980 10360 1070010 100 300 500 906 2912 5223 9060 9707 10446






0

005

01

015

02

025

03

200 220 240 260 280 300 320minus005

minus01

minus015

minus02

a1

a2

b1

b2

c1

c2

Wavelength (nm)



0

001

002

003

004

005

0 5 10 15 20 25 30 35 40 45 50 55 60 65

Cal

ibra

tio

n s

lop

e

c

b

a












4 Conclusions



Conict of nterests


Acknowledgments


References





























Journal of

Chemistry


Advances in

Physical Chemistry



Journal of

Volume 2014














Journal of

Spectroscopy



Journal of


Quantum Chemistry






CatalystsJournal of









4 Conclusions



Conict of nterests


Acknowledgments


References





























Journal of

Chemistry


Advances in

Physical Chemistry



Journal of

Volume 2014














Journal of

Spectroscopy



Journal of


Quantum Chemistry






CatalystsJournal of




















Journal of

Chemistry


Advances in

Physical Chemistry



Journal of

Volume 2014














Journal of

Spectroscopy



Journal of


Quantum Chemistry






CatalystsJournal of

the spectrophotometric multicomponent analysis of a ternary

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