Use of pi-acceptors for spectrophotometric determination of dicyclomine hydrochloride

Simple, rapid, accurate, and sensitive spectrophotometric methods are described for the determination of dicyclomine hydrochloride. The methods are based on the reaction of this drug as an n-electron donor with 2,3-dichloro-5,6-dicyano-p-benzoqunione (DDQ), p-chloranilic acid (p-CA), and chloranil (CL) as pi-acceptors to give highly colored complex species. The colored products are measured spectrophotometrically at 456, 530, and 650 nm for DDQ, p-CA, and CL, respectively. Optimization of the different experimental conditions were studied. Beer's law was obeyed in concentration ranges of 20-100, 50-250, and 80-600 microg/mL for DDQ, pCA, and CL, respectively. Colored complexes are produced in organic solvents and are stable for at least 1 h. The methods were applied to Spasmorest antispasmotic tablets and ampoules with good accuracy and precision.     

Spectrophotometric determination of rifampicin through chelate formation and charge transfer complexation in pharmaceutical preparation and biological fluids

Two simple and accurate spectrophotometric methods for determination of Rifampicin (RIF) are described. The first method is based on charge transfer (CT) complex formation of the drug with three pi-electron acceptors either 2,3-dichloro-5,6-dicyano-1,4-benzoquinone (DDQ), 7,7,7,8-Tetracyanoquinodimethane (TCNQ) or 2,3,5,6-Tetrachloro-1,4-benzoquinone (p-chloranil) in acetonitrile. The method is followed spectrophotometrically by measuring the maximum absorbance at 584 nm, 761 nm (680 nm) or 560 nm for DDQ, TCNQ and p-chloranil, respectively. Under the optimized experimental conditions, the calibration curves showed a linear relationship over the concentration ranges of 5-140 microg/ml, 2-45 microg/ml (5-120 microg/ml) and 15-200 microg/ml, respectively. The second method is based on the reaction of RIF with iron(III) forming a water insoluble violet complex which is extracted into chloroform. The method determines RIF in concentration range of 10-240 microg/ml at 540 nm. The proposed methods applied to determination of RIF in capsule, human serum and urine samples with good accuracy and precision. The results were compared statistically with the official method and showed no significant different between the methods compared in terms of accuracy and precision.     

Development and Validation of Selective Spectrophotometric Methods for the Determination of Pregabalin in Pharmaceutical Preparation

Three simple, quick and sensitive methods are described for the spectrophotometric determination of pregabalin (Pgb) in pharmaceutical preparations. Among them, the first two methods are based on the reaction of Pgb as n-electron donors with 2,3-dichloro-5,6-dicyano-1,4-benzoquinone (DDQ) and 7,7,8,8-tetracyanoquinodimethane (TCNQ) as π-acceptors to give highly colored complex species. The colored products were quantitated spectrophotometrically at 494 and 841 nm for DDQ and TCNQ, respectively. Optimization of the different experimental conditions was conducted. Beer’s law was obeyed in the concentration ranges 2.0—30.0 and 1.5—10 µg•mL－1 for DDQ and TCNQ methods, respectively. The third method is based on the interaction of ninhydrin (NN) with primary amine present in the pregabaline. This reaction produces a blue coloured product in N,N-dimethylformamide (DMF) medium, which absorbs maximally at 573 nm. Beer’s law was found in the concentration range 40.0—180.0 μg•mL－1. The methods were applied successfully to the determination of this drug in pharmaceutical dosage forms.     

Spectrophotometric and electrical studies of charge-transfer complexes of sodium flucloxacillin with pi-acceptors

The present study is interested to develop a simple, rapid and accurate spectrophotometric method for determination of sodium flucloxacillin (fluc) in pure form and pharmaceutical formulations. The charge-transfer (CT) interactions between sodium flucloxacillin as electron donor and chloranilic acid (CLA), dichloroquinone 4-chloroimide (DCQ), 2,3-dichloro-5,6-dicyano-p-benzoquinone (DDQ) and 7,7,8,8 tetracyano-p-quinodimethane (TCNQ), as pi-electron acceptors have been investigated spectrophotometrically. Different variables affecting the reaction were studied and optimized. Under the optimum conditions, linear relationships with good correlation coefficients (0.9979-0.9995) were found between the absorbance and the concentration of the drug in the range 16-880 microg ml(-1). The proposed methods were applied successfully to the determination of the examined drug either in pure or pharmaceutical dosage forms with good accuracy and precision. The formation of the CT-complexes and the sites of interaction were confirmed by elemental analysis CHN, UV-vis, IR, (1)H NMR and mass spectra techniques. Based on Job's method of continuous variation plots, the obtained results indicate the formation of 1:1 charge-transfer complexes with the general formula [(fluc)(acceptor)]. Statistical analysis of the obtained results showed no significant difference between the proposed method and official method.     

Spectrophotometric study of the reaction mechanism between DDQ as pi-acceptor and potassium iodate and flucloxacillin and dicloxacillin drugs and their determination in pure and in dosage forms

Two simple and accurate spectrophotometric methods are presented for the determination of beta-lactam drugs, flucloxacillin (Fluclox) and dicloxacillin (Diclox), in pure and in different pharmaceutical preparations. The charge transfer (CT) reactions between Fluclox and Diclox as electron donors and 2,3-dichloro-5,6-dicyano-p-benzoquinone (DDQ) pi-acceptor and potassium iodate via oxidation reduction reaction where the highly coloured complex species or the liberated iodine have been spectrophotometrically studied. The optimum experimental conditions have been studied carefully. Beer's law is obeyed over the concentration range of 2-450 microg ml(-1) for Fluclox and 10-450 microg ml(-1) for Diclox using DDQ reagent and at 50-550 microg ml(-1) for Fluclox and 50-560 microg ml(-1) for Diclox using iodate method, respectively. For more accurate results, Ringbom optimum concentration range is calculated and found to be 6-450 and 15-450 microg ml(-1) for Fluclox and Diclox using DDQ, respectively, and 65-550 and 63-560 microg ml(-1) for Fluclox and Diclox using iodine, respectively. The Sandell sensitivity is found to be 0.018 and 0.011 microg cm(-2) for DDQ method and 0.013 and 0.011 microg cm(-2) for iodate method for Fluclox and Diclox, respectively, which indicates the high sensitivity of both methods. Standard deviation (S.D.=0.01-0.80 and 0.07-0.98) and relative standard deviation (R.S.D.=0.13-0.44 and 0.11-0.82%) (n=5) for DDQ and iodate methods, respectively, refer to the high accuracy and precision of the proposed methods. These results are also confirmed by between-day precision of percent recovery of 99.87-100.2 and 99.90-100% for Fluclox and Diclox by DDQ method and 99.88-100.1 and 99.30-100.2% for Fluclox and Diclox by iodate method, respectively. These data are comparable to those obtained by British and American pharmacopoeias assay for the determination of Fluclox and Diclox in raw materials and in pharmaceutical preparations.     

Spectrophotometric study of the reaction mechanism between DDQ Pi- and iodine sigma-acceptors and chloroquine and pyrimethamine drugs and their determination in pure and in dosage forms

Two simple and accurate spectrophotometric methods are presented for the determination of anti-malarial drugs, chloroquine phosphate (CQP) and pyrimethamine (PYM), in pure and in different pharmaceutical preparations. The charge transphere (CT) reactions between CQP and PYM as electron donors and 2,3-dichloro-5,6-dicyano-p-benzoquinone (DDQ) pi-acceptor and iodine sigma-acceptor reagents to give highly coloured complex species have been spectrophotometrically studied. The optimum experimental conditions have been studied carefully. Beer' law is obeyed over the concentration range of 1.0-15 microg ml(-1) for CQP and 1.0-40 microg ml(-1) for PYM using I(2) and at 5.0-53 microg ml(-1) for CQP and 1.0-46 microg ml(-1) for PYM using DDQ reagents, respectively. For more accurate results, Ringbom optimum concentration range is calculated and found to be 10-53 and 8-46 microg ml(-1) for CQP and PYM using DDQ, respectively and 5-15 and 8-40 microg ml(-1) for CQP and PYM using iodine, respectively. The Sandell sensitivity is found to be 0.038 and 0.046 g cm(-2) for DDQ method and 0.0078 and 0.056 g cm(-2) for I(2) method for CQP and PYM, respectively which indicates the high sensitivity of both methods. Standard deviation (S.D.=0.012-0.014 and 0.013-0.015) and relative standard deviation (R.S.D.=0.09-1.4 and 1.3-1.5%) (n=5) for DDQ and I(2) methods respectively, refer to the high accuracy and precision of the proposed methods. These results are also confirmed by between day precision of percent recovery of 99-100.6%, and 98-101% for CQP and PYM by DDQ method and 99-102% and 99.2-101.4% for CQP and PYM by I(2) method respectively. These data are comparable to those obtained by British and American pharmacopoeias assay for the determination of CQP and PYM in raw materials and in pharmaceutical preparations.     

Utility of Certain σ and π-Acceptors for the Spectrophotometric Determination of Sildenafil Citrate (Viagra)

 The molecular interaction between sildenafil citrate as electron donor and each of iodine; 7,7,8,8-tetracyanoquinodimethane (TCNQ); 2,3-dichloro-5,6-dicyano-1,4-benzoquinone (DDQ); tetracyanoethylene (TCNE); 2,4,7-trinitro-9-fluorenon (TNF); chloranilic acid (CLA); chloranil (CL) and bromanil (BL) as acceptors have been investigated spectrophotometrically. Different variables affecting the reaction were studied and optimized. Beer’s law was obeyed in a concentration limit of 10–260 μg/mL for sildenafil citrate. For more accurate analysis, Ringbom optimum concentration range was found to be between 20–240 μg/mL. The limits of detection and determination were calculated and found to be 1.5 and 5.2 μg/mL, respectively. The standard deviations were calculated for different concentrations of sildenafil citrate using various acceptors. A Job’s plot of the absorbance versus the molar ratio of the sildenafil citrate to each of acceptors under consideration indicated (1:1) ratio. The proposed methods were found to be rapid, accurate, precise and sensitive and could be applied for determination of sildenafil citrate in pharmaceutical dosage forms (Viagra) without interferences from common additives encountered. Received August 30, 2000. Revision January 5, 2001.     

Spectrophotometric determination of ciprofloxacin in pure form and in tablets through charge-transfer complexation reactions

Three simple, quick and sensitive spectrophotometric methods are described for the determination of ciprofloxacin. The methods are based on the reaction of this drug as ann-electron donor with 2,3-dichloro-5,6-dicyano-p-benzoquinone (DDQ), 7,7,8,8,-tetracyanoquinodimethane (TCNQ) andp-chloranil (CL) as -acceptors to give highly coloured complex species. The coloured products are quantitated spectrophotometrically at 460, 843 and 550 nm for DDQ, TCNQ and CL, respectively. Optimization of the different experimental conditions is described. Beer's law is obeyed in the concentration ranges 5–50, 1.5–15 and 20–200 g ml^–1 ciprofloxacin, but the concentration ranges for best accuracy are 10–48, 2.5–15 and 35– 195 g ml^–1 of drug for DDQ, TCNQ and CL, respectively. The relative standard deviations are less than 1.5%. Applications of the suggested methods to ciprofloxacin tablets are presented and compared with the USP method. The stability constants of the 11 DDQ and CL complexes were 1.086 × 10⁴ and 2.581 × 10⁴ lmol^–1, respectively, whereas for the 12 TCNQ complex it was 3.62 × 10⁸1. mol^–1.     

Validated spectrophotometric and fluorimetric methods for analysis of clozapine in tablets and urine

Five spectrophotometric methods and one fluorimetric method have been developed and validated for the analysis of clozapine. The spectrophotometric methods were based on the charge-transfer complexation reaction between clozapine as electron donor and each of iodine as sigma-acceptor or 7,7,8,8-tetracyanoquinondimethane (TCNQ), 2,3-dichloro-5,6-dicyano-1,4-benzo-quinone (DDQ), tetracyanoethane (TCNE), and p-chloranilic acid (pCA) as pi-acceptors. The obtained complexes were measured spectrophotometrically at 365, 843, 460, 414, and 520 nm for iodine, TCNQ, DDQ, TCNE, and pCA, respectively. The fluorimetric method was based on the oxidation of clozapine in the presence of perchloric acid by cerium (IV), and subsequent measuring the fluorescence of the produced cerium (III) fluorimetrically at lambda(excitation) 260 and lambda(emission) 355 nm. Under the optimum assay conditions, Beer's law was obeyed at concentrations ranged from 4-200 microg mL(-1) for the spectrophotometric methods and from 24-250 ng mL(-1) for the fluorimetric method. The limits of detection for the spectrophotometric methods were 1.12, 1.76, 2.22, 0.95, and 13.26 microg mL(-1) for iodine, TCNQ, DDQ, TCNE, and pCA, respectively. The limit of detection for the fluorimetric method was 6.69 ng mL(-1). The proposed methods were successfully applied to the analysis of clozapine in tablets with good recoveries. The fluorimetric method could also be applied to the analysis of clozapine in spiked urine samples. The molar ratios and the reaction mechanisms were investigated.     

Validated spectrophotometric methods for the determination of amiodarone hydrochloride in commercial dosage forms using p-chloranilic acid and 2,3-dichloro-5,6-dicyano-1,4-benzoquinone.

Two simple, sensitive and economical spectrophotometric methods have been developed for the determination of amiodarone hydrochloride in pure form and commercial dosage form. These methods (A and B) are based on the reaction of amiodarone base as n-electron donor with p-chloranilic acid and 2,3-dichloro-5,6-dicyano-1,4-benzoquinone (DDQ) as pi-acceptors to give highly colored complex species which absorb maximally at 535 and 570 nm, respectively. Beer's law is obeyed in the concentration ranges 10.0 - 360.0 and 2.0 - 65.0 microg ml(-1) for methods A and B, respectively. Application of the proposed methods to commercial pharmaceutical tablets are presented.     

Utility of certain pi-acceptors for the spectrophotometric determination of some penicillins

Two simple and sensitive spectrophotometric methods are described for the determination of six penicillin derivatives. The methods are based on the reaction of these drugs as n-electron donors with either 2,3-dichloro-5,6-dicyano-p-benzoquinone (DDQ) or 7,7,8,8-tetracyanoquinodimethane (TCNQ) as pi-acceptors, to give a highly coloured radical anion. The coloured products are quantified spectrophotometrically at 460 and 842 nm for DDQ and TCNQ, respectively. The optimization of the different experimental conditions is described. The interference from streptomycin sulphate and common degradation products was also studied. The proposed methods were applied successfully to the determination of the different penicillins investigated, either in pure or dosage forms, with good accuracy and precision. The results were compared with those given by the official United States Pharmacopeial XXI method.     

Simultaneous determination of aluminium and iron in glasses,phosphate rocks and cement using first- and second-derivative spectrophotometry

First- and second-derivative spectrophoto-metric methods for the simultaneous determination of aluminium and iron in their mixtures are described. The methods are based on the colored complexes formed by aluminium and iron with hematoxylin in the presence of cetyltrimethylammonium bromide as a surfactant. The zero-crossing method has been utilized to measure the first- and second-derivative value of the derivative spectrum. Aluminium (0.05-1 microg ml(-1)) could be determined in the presence of iron (0.09-1.6 microg ml(-1)) and vice versa. The detection limits of aluminium and iron are 0.01 and 0.09 microg ml(-1), respectively in the first-derivative mode and 0.014 and 0.1 microg ml(-1) in the second-derivative mode. The proposed method has been applied to the simultaneous determination of aluminium and iron in glasses, phosphate rocks, cement and magnesite alloy.     

New Spectrophotometric Methods for Microdetermination of Fluoxacillin and Cloxacillin in Pure and Dosage Forms

 Two simple, rapid and sensitive methods for the microdetermination of penicillin derivatives are described. The studied compounds are fluoxacillin and cloxacillin. The methods are based on the reaction of these drugs as n-electron donors with either 2,3-dichloro-5,6-dicyano-p-benzoquinone (DDQ) or 7,7, 8,8-tetracyanoquinodimethane (TCNQ) as π-acceptors, to give a highly coloured radical anion. The coloured products were quantified spectrophotometrically at 460 and 840 nm for DDQ and TCNQ, respectively. The proposed methods were applied successfully to the determination of the two penicillins investigated, either in pure or dosage forms, with good accuracy and precision. The results were compared with those given by the official method. Received December 15, 2000. Revision July 10, 2001.     

In situ synthesis, photometric and spectroscopic studies of chelating system during the 1,4,7,10,13,16-hexaoxacyclooctadecane charge transfer reaction with different acceptors

Electron donor acceptor complexes (EDA) of the 1,4,7,10,13,16-hexaoxacyclooctadecane (18-crown-6) as a rich donor were spectrophotometrically discussed and synthesized in solid form according the interactions with different nine of usual π-acceptors like 2,3,5,6-tetrachlorocyclohexa-2,5-diene-1,4-dione (p-chloranil; p-CHL), tetrachloro-1,2-benzoquinone (o-chloranil; o-CHL), 2,3-dichloro-5,6-dicyano-1,4-benzoquinone (DDQ), tetracyanoquinodimethane (TCNQ), 2,6-dichloroquinone-4-chloroimide (DCQ), 2,6-dibromoquinone-4-chloroimide (DBQ), 2,5-dichloro-3,6-dihydroxy-1,4-benzoquinone (chloranilic acid; CLA), N-bromosuccinimide (NBS), 2,4,6-trinitrophenol (picric acid; PA). Spectroscopic and physical data such as formation constant (K(CT)), molar extinction coefficient (?(CT)), standard free energy (ΔG°), oscillator strength (f), transition dipole moment (μ), resonance energy (R(N)) and ionization potential (I(p)) were estimated in chloroform or methanol at 25°C. Based on the elemental analysis and photometric titrations the CT-complexes were formed indicated the formation of 1:1 charge-transfer complexes for the o-CHL, TCNQ, DCQ, DBQ and NBS acceptors but 1:3 ratio for p-CHL, DDQ, CLA and PA, respectively. The charge-transfer interactions were interpretative according to the formation of dative ion pairs [18C6(?+), A(?-)], where A is acceptor. All of the resulting charge transfer complexes were isolated in amorphous form and the complexes formations on IR and (1)H NMR spectra were discussed.     

Spectrophotometric determination of anilines based on charge-transfer reaction

The molecular interactions between aniline, p-toluidines, benzidine and p-phenylenediamine as electron donors and 7,7,8,8-tetracyanoquinodimethane (TCNQ) as acceptor have been investigated by spectrophotometric method. Different variables affecting the reaction were studies and optimized. At the optimum reaction conditions Beer's law was obeyed in a concentration limit of 0.6-3.0, 0.3-3.0, 0.3-3.0 and 0.3-2.7 microg ml(-1) for aniline, p-toluidines, benzidine and p-phenylenediamine. The developed methods were applied successfully for the determination of the studied compounds in waste water and relative standard deviation of the methods were 0.8-3.0%. Percentage recoveries ranged from 97.22% to 102.78%.     

Spectrophotometric determination of terfenadine in pharmaceutical preparations by charge-transfer reactions

A simple, rapid and accurate method for the spectrophotometric determination of terfenadine has been developed. The proposed method based on the charge-transfer reactions of terfenadine, as n-electron donor, with 7,7,8,8-tetracyanoquinodimethane (TCNQ), tetracyanoethylene (TCNE), 2,3-dichloro-5,6-dicyano-1,4-benzoquinone (DDQ) or 2,5-dichloro-3,6-dihydroxy-1,4-benzoquinone (chloranilic acid, p-CLA) as π-acceptors to give highly colored complexes. The experimental conditions such as reagent concentration, reaction solvent and time have been carefully optimized to achieve the highest sensitivity. Beer's law is obeyed over the concentration ranges of 3–72, 3–96, 12–168 and 24–240 μg mL⁻¹ terfenadine using TCNQ, TCNE, DDQ and p-CLA, respectively, with correlation coefficients 0.9999, 0.9974, 0.9997 and 0.9979 and detection limits 0.3, 0.4, 2.6 and 12.3 μg mL⁻¹, for the reagents in the same order. DDQ and p-CLA react spontaneously with terfenadine to give colored complexes that can be applied for the flow injection analysis of terfenadine in the concentration ranges 2.4–120 and 24–240 μg with correlation coefficients 0.9990 and 0.9985 and detection limits 0.8 and 2.7 μg for DDQ and p-CLA, respectively, in addition to the high sampling through output of 40 sample h⁻¹.     

Spectroscopic characterizations on the N,N′-bis-alkyl derivatives of 1,4,6,8-naphthalenediimide charge-transfer complexes

Charge-transfer (CT) complexes formed from the reactions of two N,N′-bis-alkyl derivatives of 1,4,6,8-naphthalenediimide such as N,N′-bis-[2-hydroxyethyl]-1,4,6,8-naphthalenediimide (BHENDI) and N,N′-bis-[2-N,N-dimethylaminoethyl]-1,4,6,8-naphthalenediimide (BDMAE NDI) with DDQ, CHL, TCNQ, DCQ and DBQ as π-acceptors have been studied spectrophotometrically in chloroform and/or methanol at 25 °C. The photometric titration curves for the reactions indicated that the data obtained refer to 1:1 charge-transfer complexes of [(BHENDI)(DDQ)], [(BDMAENDI)(DDQ)], [(BHENDI)(CHL)], [(BDMAENDI)(CHL)], [(BHENDI)(TCNQ)], [(BDMAENDI)(TCNQ)], [(BHENDI)(DCQ)], [(BDMAENDI)(DCQ)], [(BHENDI)(DBQ)] and [(BDMAENDI)(DBQ)] were formed. Benesi–Hildebrand and its modification methods were applied to the determination of association constant (K), molar extinction coefficient (?). The solid CT complexes have been synthesized and characterization by different spectral methods.     

Spectrophotometric determination of some antihistaminic drugs using 7,7,8,8-tetracyanoquinodimethane (TCNQ)

A simple and sensitive spectrophotometric method is suggested for analysis of 3 antihistaminic drugs, acrivastine (I), mequitazine (II), and dimethindene maleate (III). The method is based on reaction of the drugs with 7,7,8,8-tetracyanoquinodimethane (TCNQ) in acetonitrile to form highly stable colored products that are measured at 750, 766, and 844 nm for I and II, and 480 and 618 nm for III. Beer's law is obeyed in the ranges of 5-60 microg/mL for 1, 5-50 microg/mL for II, and 10-70 microg/mL for III. The optimum assay conditions and their applicability to the determination of the cited drugs in pharmaceutical formulations are described. The method is statistically analyzed as compared with the European Pharmacopoeia (2001) method for the analysis of dimethindene maleate and reference methods for acrivastine and mequitazine drugs revealing good accuracy and precision.     

Use of charge-transfer complexation in the spectrophotometric analysis of certain cephalosporins

Three simple, rapid and sensitive spectrophotometric procedures were developed for the analysis of cephapirin sodium (1), cefazoline sodium (2), cephalexin monohydrate (3), cefadroxil monohydrate (4), cefotaxime sodium (5), cefoperazone sodium (6) and ceftazidime pentahydrate (7) in pure form as well as in their pharmaceutical formulations. The methods are based on the reaction of these drugs as n-electron donors with the σ-acceptor iodine, and the π-acceptors: 2,3-dichloro-5,6-dicyano-p-benzo-quinone (DDQ) and 7,7,8,8-tetracyanoquinodimethane (TCNQ). Depending on the solvent polarity, different coloured charge-transfer complexes and radicals were developed. Different variables and parameters affecting the reactions were studied and optimized. The obtained charge-transfer complexes were measured at 364 nm for iodine (in 1,2-dichloroethane), 460 nm for DDQ (in methanol) and 843 nm for TCNQ (in acetonitrile). Ultraviolet–visible, infrared and ¹H-nuclear magnetic resonance techniques were used to study the formed complexes. Due to the rapid development of colours at ambient temperature, the obtained results were used on thin-layer chromatograms for the detection of the investigated drugs. Beer's plots were obeyed in a general concentration range of 6–50, 40–300 and 4–24 μg ml⁻¹ with iodine, DDQ and TCNQ, respectively, with correlation coefficients not less than 0.9989. The proposed procedures could be applied successfully to the determination of the investigated drugs in vials, capsules, tablets and suspensions with good recovery; percent ranged from 96.47 (±1.14) to 98.72 (±1.02) in the iodine method, 96.35 (±1.62) to 98.51 (±1.30) in the DDQ method, and 95.98 (±0.78) to 98.40 (±0.87) in the TCNQ method. The association constants and standard free energy changes using Benesi–Hildebrand plots were studied. The binding of cephalosporins to proteins in relation to their molar absorptivities was studied.     

Simultaneous determination of benserazide and levodopa by capillary electrophoresis-chemiluminescence using an improved interface

A capillary electrophoresis coupling with indirect chemiluminescence detection method for the simultaneous determination of benserazide and levodopa has been developed. The detection interface was improved to simplify the capillary electrophoresis-chemiluminescence (CE-CL) system and the features of this improved interface were illustrated in this paper. The CE-CL conditions for the simultaneous determination of benserazide and levodopa were optimized. Under the optimal conditions, the CL intensity was linear with concentrations of levodopa in the range of 1.0 to 100.0 microg ml(-1), and benserazide in the range of 10.0 to 1,000 microg ml(-1), respectively. The detection limits (S/N=3) in turn were 1.85 microg ml(-1) for BS and 0.12 microg ml(-1) for L-dopa with relative standard deviations of less than 3%. The proposed method has been successfully applied to the determination of benserazide and levodopa in medopar tablets and spiked urine samples, demonstrating the feasibility and reliability of the proposed method.