Analysis of carbamazepine and its active metabolite, carbamazepine-10,11-epoxide, in human plasma using high-performance liquid chromatography

A sensitive method based on high-performance liquid chromatography (HPLC) with ultraviolet (UV) detection was developed for the determination of carbamazepine (CBZ) and one of its active metabolites, carbamazepine-10,11-epoxide (CBZ-E) in human plasma. CBZ, CBZ-E and the internal standard (IS) 10,11-dihydrocarbamazepine were extracted from human plasma into methyl tert-butyl ether. CBZ, CBZ-E and the IS were successfully separated on an RP C18 column with a mobile phase of acetonitrile:methanol:water (18:19:63, v/v/v) and monitored via UV detection at 210 nm. The calibration curves were linear over the concentration ranges of 0.01–10 μg/mL for CBZ and 0.005–5 μg/mL for CBZ-E in human plasma, respectively. The method displayed excellent sensitivity, precision and accuracy, and was successfully applied to the quantification of CBZ and CBZ-E in human plasma after oral administration of a single 200 mg CBZ CR tablet. This method is suitable for bioequivalence studies following single doses given to healthy volunteers.     

High-performance liquid chromatographic determination of carbamazepine and carbamazepine 10,11-epoxide in plasma and saliva following solid-phase sample extraction

A rapid, sensitive and simple to operate high-performance liquid chromatographic method for the simultaneous determination of carbamazepine (CBZ) and carbamazepine 10,11-epoxide (CBZ-EP) in plasma and saliva is described. The drug and its metabolite are extracted from both plasma and saliva using commercially available reversed-phase octadecylsilane bonded silica columns (Bond-Elut C18, 2.8 ml capacity). Separation of CBZ and CBZ-EP was achieved by reversed-phase chromatography, using a mobile phase consisting of acetonitrile-methanol-water (19:37:44) at a flow-rate of 1.8 ml/min in conjunction with a Nova-Pak C18 column. The analytical column, in Radial-Pak cartridge form, was used in combination with a Z-module RCSS and protected by a Guard-Pak precolumn module containing a Guard-Pak mu Bondapak C18 insert. Using ultraviolet detection at 214 nm, levels in the region of 50-100 ng/ml for CBZ and CBZ-EP can be measured with only 250 and 500 microliters of plasma and saliva, respectively. The method, which has been used to determine steady-state concentrations of the drug and its metabolite in paediatric patients receiving CBZ monotherapy, is also suitable for pharmacokinetic studies.     

Routine monitoring of carbamazepine and carbamazepine-10,11-epoxide in plasma by high-performance liquid chromatography using 10-methoxycarbamazepine as internal standard

Carbamazepine and carbamazepine-10,11-epoxide were separated by high-performance liquid chromatography (HPLC) with acetonitrile-water as mobile phase, and detection was effected by UV absorption at 215 nm with a total retention time of less than 10 min. Plasma samples were extracted with dichloromethane and 4 M sodium hydroxide, and 10-methoxy-carbamazepine was added as internal standard. Other commonly used anticonvulsant drugs present in plasma showed no significant interference. The within-batch coefficient of variation for carbamazepine was 4.9% and carbamazepine-10,11-epoxide 5.9%. Between-batch coefficients of variation were 3.7% and 5.3%, respectively. Mean recovery for carbamazepine was 100.2% and for carbamazepine-10,11-epoxide 100.6%. This HPLC method was compared with both an enzyme immunoassay procedure (EMIT) and a gas-liquid chromatographic (GLC) method. Correlation coefficient between HPLC/EMIT for carbamazepine was 0.983, HPLC/GLC carbamazepine 0.988 and HPLC/GLC carbamazepine-10,11-epoxide 0.981.     

Determination of carbamazepine and carbamazepine-10,11-epoxide in human serum and plasma by micellar electrokinetic capillary chromatography in the absence of electroosmosis

Therapeutic drug monitoring of carbamazepine (CBZ), a widely used antiepileptic drug, is required for optimization of pharmacotherapy with this drug and for assessment of the patient's compliance to therapy. The suitability of employing micellar electrokinetic capillary chromatography (MEKC) in the absence of electroosmosis for the determination of CBZ and its main metabolite carbamazepine-10,11-epoxide (CBZE) in extracts of human serum and plasma is reported. Using micelles formed by dodecyl sulfate, analyses performed in untreated fused-silica capillaries at acidic pH and in commercially available coated capillaries under application of reversed polarity are compared. Uncoated and polyvinyl alcohol coated capillaries proved to be unsuitable for this purpose, whereas capillaries coated with linear polyacrylamide and N-acryloylaminoethoxyethanol and operated at pH 7.6 are shown to provide high-quality and reliable data on a short time scale. Assay performance is discussed via statistical analysis of the data produced from a set of quality control sera that contain up to 14 different drugs and via analysis of patient samples. Intraday and interday imprecision data for concentrations between 4.0 and 84 microM are demonstrated to be < 10%. Run times are shown to be < 50% compared to those observed in conventional MEKC at alkaline pH (i.e., in the presence of electroosmosis).     

Simultaneous quantitation of salivary carbamazepine, carbamazepine-10,11-epoxide, phenytoin and phenobarbitone by high-performance liquid chromatography

A rapid, sensitive and accurate high-performance liquid chromatographic method for the simultaneous quantitation of phenobarbitone, phenytoin, carbamazepine and carbamazepine-10,11-epoxide in saliva is described. Only small volumes of saliva (100 microliters) are required. Separation of the drugs is achieved by reversed-phase chromatography on a Nova-Pak C18 column, with a mobile phase of acetonitrile-phosphate buffer at a flow-rate of 2.0 ml/min. Detection is effected by ultra-violet absorption at 215 nm. The total run time is under 12.5 min per assay. A precipitation but no extraction step is involved, simplifying the assay method. Salivary concentrations in the range 0.25-25 micrograms/ml for carbamazepine, 0.5-20 micrograms/ml for phenytoin and phenobarbitone and 0.4-20 micrograms/ml for carbamazepine-10,11-epoxide can be measured. Recovery varies from 94 to 108%. The method has been used for routine measurements of anticonvulsants in saliva collected daily from patients with intractable epilepsy.     

In vivo solid-phase microextraction for single rodent pharmacokinetics studies of carbamazepine and carbamazepine-10,11-epoxide in mice

The use of solid-phase microextraction (SPME) for in vivo sampling of drugs and metabolites in the bloodstream of freely moving animals eliminates the need for blood withdrawal in order to generate pharmacokinetics (PK) profiles in support of pharmaceutical drug discovery studies. In this study, SPME was applied for in vivo sampling in mice for the first time and enables the use of a single animal to construct the entire PK profile. In vivo SPME sampling procedure used commercial prototype single-use in vivo SPME probes with a biocompatible extractive coating and a polyurethane sampling interface designed to facilitate repeated sampling from the same animal. Pre-equilibrium in vivo SPME sampling, kinetic on-fibre standardization calibration and liquid chromatography–tandem mass spectrometry analysis (LC–MS/MS) were used to determine unbound and total circulating concentrations of carbamazepine (CBZ) and its active metabolite carbamazepine-10,11-epoxide (CBZEP) in mice (n = 7) after 2 mg/kg intravenous dosing. The method was linear in the range of 1–2000 ng/mL CBZ in whole blood with acceptable accuracy (93–97%) and precision (<17% RSD). The single dose PK results obtained using in vivo SPME sampling compare well to results obtained by serial automated blood sampling as well as by the more conventional method of terminal blood collection from multiple animals/time point. In vivo SPME offers the advantages of serial and repeated sampling from the same animal, speed, improved sample clean-up, decreased animal use and the ability to obtain both free and total drug concentrations from the same experiment.     

Simultaneous spectrophotometric determination of carbamazepine and phenytoin in serum by PLS regression and comparison with HPLC

Carbamazepine (CBZ) and phenytoin (PHT) are two antiepileptic drugs which are used simultaneously. In this paper a partial least-squares (PLS) calibration method is described for the simultaneous spectrophotometric determination of CBZ and PHT in plasma. Standard binary mixtures of CBZ and PHT have been resolved by application of PLS-1 to their UV spectra. Then, the binary standard solutions, spiked to plasma, were prepared and after the extraction of the drugs, their corresponding UV spectrum were analyzed by PLS regression to calculate the concentration of drugs in unknown plasma. A leave one out cross-validation procedure was employed to find the optimum numbers of latent variables using PRESS. A HPLC method was also applied for simultaneous determination of two drugs in the plasma and in methanol. The mean recoveries obtained by PLS were 98.4 and 98.2 for CBZ and PHT and those obtained by HPLC were 100.1 and 101.7, respectively. Although, the HPLC method showed better performance than PLS, it was found that the results obtained by PLS were comparable with those obtained by HPLC method.     

A sensitive and highly selective extractive spectrophotometric method for the determination of palladium

Summary A Sensitive and Highly Selective Extractive Spectrophotometric Method for the Determination of Palladium Palladium forms an anionic chelate with 4-(2-pyridylazo)resorcinol (PAR, H₂R) which is extractable with xylometazolonium cation (XMH) into chloroform in the pH range 7.2–7.8 giving an intensely pinkish red coloured solution. The coloured species exhibits maximum absorbance at 520 nm with molar absorptivity 3.34×10⁴1·mole^–1·cm^–1 and obeys Beer's law in the range 0.8–5.30g/ml of palladium. The composition of the extracting species is found to be 111 for Pd(II)PARXMH. Large concentrations of EDTA and oxalate have no interference in the spectrophotometric determination of palladium by this procedure. Based on this a highly selective and sensitive method for the determination of palladium in the presence of Zn(II), Cd(II), Hg(II), Fe(III), Mn(II), Co(III), Mo(VI), Ru(IV), Sb(III), Al(III) is described. The application of this method for the determination of palladium in synthetic mixtures corresponding to the composition of jewel alloy and stibiopalladinite mineral is also demonstrated.     

A spectrophotometric method for the simultaneous determination of peucedanin and oreoselone

Conclusions A spectrophotometric method for the simultaneous determination of peucedanin and oreoselone has been proposed     

An extractive spectrophotometric method for the determination of tetramisole hydrochloride in pharmaceutical preparations

A simple extractive photometric method for the determination of tetramisole hydrochloride in pharmaceutical preparations is described. The method uses the formation of coloured complexes of the drug with reagents such as Solochrome Dark Blue, Solochrome Black T, Bromocresol Purple, Bromothymol Blue, Bromophenol Blue and Bromocresol Green in an acidic buffer. The ion-pair complexes formed are quantitatively extracted into chloroform under the experimental conditions.     

A rapid spectrophotometric method for the simultaneous determination of cumene and benzene in air

Summary The paper deals with recent analytical methods for the determination of cumene and benzene.In the method emphasized here cumene and benzene are determined at 258, 260 and 268 nm in n-heptane solution. The concentration is obtained graphically by means of a calibration diagram.Silica gel is used for the adsorption of benzene and cumene from air samples.

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Zusammenfassung Die neueren analytischen Methoden zur Bestimmung von Cumol und Benzol werden besprochen.Nach der hier angegebenen Methode erfolgt die Bestimmung von Cumol und Benzol UV-spektrophotometrisch bei 258, 260 und 268 nm in n-Heptan. Die Konzentration wird graphisch mit Hilfe eines Eichdiagramms ermittelt.Für die Adsorption der gesuchten Stoffe aus Luft- und Gasproben wird Silicagel verwendet.

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Technical assistance in this investigation was provided by Mrs. J. Krídlova.     

A ratio derivative spectrophotometric method for the simultaneous determination of uranium and plutonium

A ratio derivative spectrophotometric method has been developed for the simultaneous determination of uranium and plutonium at mg levels in 1M HNO₃ medium. In this method the overlapping spectra of uranium and plutonium are well resolved by making use of the first derivative of the ratios of their direct absorption spectra. The derivative ratio absorbances of uranium and plutonium are measured at 411.2 and 473.8 nm, respectively for their quantification. The method is simple, fast and does not require separation of uranium and plutonium. Another salient feature of the method is that it does not lead to generation of analytical waste thereby minimising the efforts required for the recovery of plutonium. Uranium in the conc. range of 10–25 mg/g and plutonium in the conc. range of 0.5 to 2 mg/g (U/Pu ratio varying from about 10 to 25) were determined in the same aliquot with a precision and accuracy of about 0.5% and 1%, respectively.     

停流流动注射-诱导动力学光度法同时测定微量铁和锑

依据诱导反应的基本原理, 提出了一种同时测定多元素的方法; 研究了Fe(II)、Sb(III)诱导的Cr(VI)-I^-氧化还原反应体系, 并据此建立了停流-诱导动力学光度法同时测定微量铁和锑的工作条件。线性范围分别为0~1.2μg.mL^-1Fe(II)和0~2.0μg.mL^-1Sb(III); 检测限为0.012μg/mL^-1Fe(II)和0.014μg.mL^-1Sb(III)。除Ti(III)、V(IV)及As(III)外, 其余共存离子不影响测定。用本法测定了锌标准物及模拟样品中的铁和锑含量, 结果满意。     

A rapid extractive spectrophotometric method for the determination of tin in canned foods with 5,7-dichloro-8-quinolinol

A rapid method for the spectrophotometric determination of tin in canned foods, based on formation of the binary Sn(IV)-5,7-dichloro-8-quinolinol complex and extraction into chloroform has been developed. The absorption maximum at 390nm ( = 1.26 x 10(4) l.mole(-1).cm(-1)) is used for the determination. Beer's law is obeyed up to 6mug of tin per ml. Organic matter is destroyed by digestion with acid. Potential interferences have been studied. The detection limit for tin is 2.5mg kg .     

Chemometrics-assisted spectrophotometric method for simultaneous determination of vitamins in complex mixtures

An advanced independent component analysis algorithm (MILCA) is applied for simultaneous chemometric determination of fat- and water-soluble vitamins in complex mixtures. The analysis is based on the decomposition of spectra of multicomponent mixtures in the UV region. The key features of the proposed method are simplicity, accuracy, and reliability. Comparisons between the new algorithm and other established methods (MCR-ALS, SIMPLISMA, other ICA techniques) were made. Our results indicate that in most cases, MILCA is comparable or even outperforms other chemometrics methods taken for comparisons. The influence of different factors (abundance of components, noise, step of spectral scan, and scan speed) on decomposition performance has been investigated. The optimal conditions for spectroscopic registration have been identified. The proposed method was used for analysis of model mixtures and real objects (multivitamin drugs, food additives, and energy drinks). The resolved concentrations match well with the declared amounts and the results of reference methods.     

A rapid derivative spectrophotometric method for simultaneous determination of naphazoline and antazoline in eye drops

A zero-crossing first-derivative spectrophotometric method is applied for the simultaneous determination of naphazoline hydrochloride and antazoline phosphate in eye drops. The measurements were carried out at wavelengths of 225 and 252 nm for naphazoline hydrochloride and antazoline phosphate, respectively. The method was found to be linear (r2>0.999) in the range of 0.2-1 microg/ml for naphazoline hydrochloride in the presence of 5 microg/ml antazoline phosphate at 225 nm. The same linear correlation (r2>0.999) was obtained in the range of 1-10 microg/ml of antazoline phosphate in the presence of 0.5 microg/ml of naphazoline hydrochloride at 252 nm. The limit of determination was 0.2 microg/ml and 1 microg/ml for naphazoline hydrochloride and antazoline phosphate, respectively. The method was successfully used for simultaneous analysis of naphazoline hydrochloride and antazoline phosphate in eye drops without any interference from excipients and prior separation before analysis.     

HPLC method for determination of cefuroxime in plasma

Summary This paper describes an HPLC method for the determination of cefuroxime in human plasma. The method uses solid phase extraction (SPE) and has acceptable sensitivity, precision and accuracy. The limit of quantification in plasma samples is 0.1 μg mL⁻¹. Calibration curves were linear within 0.1–20 μg mL⁻¹, with mean correlation coefficient of 0.9982. Mean inter day precision and accuracy were 7.8% and 6.4%, respectively. The method was applied to determine cefuroxime levels in patients receiving cefuroxime, 3 time per day.     

Rapid spectrophotometric method (aqueous and extractive) for the determination of titanium in silicate rocks

A sensitive and highly selective aqueous as well as extractive spectrophotometric method has been developed for the determination of titanium(IV) using 2,3-dihydroxynaphthalene (H(2)ND) as a chromogenic agent. The reagent (H(2)ND) forms a 1:3 (TiOH(3+):ligand) complex at pH 4-9. The molar absorptivity and Sandell's sensitivity are 3.2 x 10(4) l . mol(-1)mol . cm(-1) and 0.001 microg/cm(2), respectively at lambda(max) 375 nm. The method has been found highly selective for Ti(IV) determination in rock samples. Solvent extraction of Ti(IV) in ethylacetate greatly improves the detection limit of the method. The method has been successfully applied to diverse silicate rock samples and results obtained are favourably comparable with those obtained from the tiron method. The reagent (H(2)ND) used in the present investigation is a much better variant than tiron for titanium(IV) determination in silicate rock samples in terms of sensitivity, selectivity, operational simplicity and economy.