Dispersive Liquid-Liquid Microextraction of Famotidine and Nizatidine from Water Samples.

A new extraction method was developed for isolation of the antihistaminic drugs (histamine H2 receptor antagonists) famotidine (FMT) and nizatidine (NZT) from aqueous samples. A low solvent consumption method using dispersive liquid-liquid microextraction (DLLME) was applied for this purpose. The parameters of the isolation, namely, volume of extraction and disperser solvents, pH of sample and shaking time were optimized. The influence of foreign substances on the extraction process was also studied. After separation of FMT and NZT using DLLME, the analytes in organic extracts were determinated by high-performance liquid chromatography combined with UV spectrophotometry and liquid chromatography connected with tandem mass spectrometry (LC-MS-MS). The use of DLLME for selective isolation of analytes enables their preconcentration. Enrichment factors 23 and 61 were obtained for FMT and NZT, respectively. These procedures enable detection of the analytes in real samples at levels 0.24 µg mL-1 (limits of detection (LOD) of FMT: 7.2·10-7 mol L-1 and LOD of NZT: 7.3·10-7 mol L-1). The method was applied for the determination of the studied antihistaminic drugs in river water and wastewater samples. The use of LC-MS-MS in conjunction with DLLME enabled detection of FMT in Netta river at a concentration level of 0.46 ± 0.04 ng mL-1.

Application of Micellar Extraction for Isolation of Famotidine from Aqueous Samples Prior to its Chromatographic Determination.

Micellar extraction was applied to isolate famotidine from aqueous samples. This drug is an H2 receptor antagonist used for the treatment of stomach diseases. The process was performed with a mixture of anionic sodium dodecylsulfate and nonionic Triton X-114 surfactants. The effect of different parameters on the efficiency of the micellar extraction such as electrolyte and surfactant concentration, pH of sample, temperature, shaking and centrifugation time was investigated. The influence of foreign substances on a studied process was tested. The elaborated procedure was applied for HPLC-UV determination of famotidine in natural water samples. The calibration graph was recorded in the range 1.35-37.12 µg mL-1 of the studied compound. The repeatability of the method was equal to 7.4%. The limit of detection and quantification values for the determination of famotidine by using the proposed method amounted to 0.40 and 1.25 µg mL-1, respectively.

The usage of micellar extraction for analysis of fluvastatin in water and wastewater samples.

This work illustrates the development of new procedures for the isolation and preconcentration of fluvastatin (FLU) from aqueous solutions. Micellar extraction (ME) combined with high performance liquid chromatography (HPLC-UV) has been successfully applied for this purpose. It was found that the analyte created micelle with anionic sodium dodecylsulfate (SDS) and/or with the binary mixture of surfactants nonionic triton X114 (TX114) and cationic tetra-n-butyloammonium bromide (TBAB). The optimal analytical conditions for the proposed extraction procedures (solution pH, concentration of surfactants, centrifugation time and electrolyte type) were ascertained. The calibration curves were recorded. The linearity ranges for FLU, isolated by SDS and the mixture of TX114/TBAB, were 0.21-28.79 µg mL(-1) and 0.21-16.45 µg mL(-1) with limit of detection (LOD) 0.19 µg mL(-1) and 0.14 µg mL(-1), respectively. The recoveries afforded by the proposed methods were high, approximately 97%. These preconcentration procedures were applied for the isolation of the statin from water and wastewater samples taken from the local rivers and wastewater treatment plants.

Extraction of ranitidine and nizatidine with using imidazolium ionic liquids prior spectrophotometric and chromatographic detection.

A new extraction medium was proposed for liquid-liquid extraction of the histamine H2 receptor antagonists ranitidine (RNT) and nizatidine (NZT). The ionic liquids with low vapor pressure and favorable solvating properties for a range of compounds such as 1-butyl-3-methylimidazolium hexafluorophosphate [C4mim][PF6] and 1-butyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide [C4mim][Tf2N] were tested for isolation of analytes. The extraction parameters of RNT and NZT, namely, amount of ionic liquid, pH of sample solution, shaking and centrifugation time were optimized. The isolation processes were performed with 1 mL of the ionic liquids. The extracted samples (pH values near 4) were shaken at 1750 rpm. The influence of interfering substances on the efficiency of extraction process was also studied. Methods for the histamine H2 receptor antagonists (ranitidine and nizatidine) determination after their separation using imidazolium ionic liquids by high performance liquid chromatography (HPLC) combined with UV spectrophotometry were developed. The application of ionic liquids in extraction step allows for selective isolation of analytes from aqueous matrices and their preconcentration. The above methods were applied to the determination of RNT and NZT in environmental samples (river water and wastewater after treatment).

Quantification of ranitidine hydrochloride in the presence of its decomposition product by spectrophotometric methods. Application for kinetic study.

Three spectrophotometric methods, based on a spectral analysis, are proposed for quantification of ranitidine hydrochloride (RHCl) in the presence of its decomposition product (R-ox) without isolation from the matrix. One of them is a zero-crossing derivative-spectrophotometry. A value of the first derivative at 332 nm generated by the Savitzky-Golay algorithm (delta lambda = 22 nm and the first polynomial degree) allows for quantification of RHCI in the concentration range 0.5-35.1 microg/mL. The second proposed spectrophotometric procedure, called Vierordt method, utilizes an additivity of the absorbance. The assay of studied compound was realized by the direct reading of absorbance at 312 nm and 202 nm for ranitidine hydrochloride and its decomposition product, respectively. The quantitative results were obtained by resolving of an appropriate system of equations. The third method is based on the bivariate calibration algorithm. The absorbance values were measured at optimum wavelengths found by Kaiser method at 228 nm and 202 nm and used for the quantification of RHCI in the presence of its decomposition product. The Beer's law was obeyed in the concentration range 0.5-35.1 microg/mL for RHCl. The discussion of applicability of all elaborated methods is presented. The proposed methods were applied for assay of ranitidine hydrochloride contents in its preparation Ranigast and for investigation of kinetics of its reaction with hydrogen peroxide.

Applications of the extractive methods in chemical analysis of some psychotropic drugs.

The review is devoted for the solid phase extraction and the extractive spectrophotometric methods for the determination of some psychotropic drugs, e.g. phenothiazines, thioxanthenes, dibenzothiazines, fluoxetine, fluvoxamine, trazodone.

Spectrophotometric determination of olanzapine by its oxidation with N-bromosuccinimide and cerium(IV)sulfate.

Three simple spectrophotometric methods have been described for the assay of olanzapine in its pure and pharmaceutical formulations. The direct method (A) is based on the drug oxidation with excess of N-bromosuccinimide in acidic medium and the two indirect methods (B and C) are based on the oxidation of the drug with excess of N-bromosuccinimide and cerium(IV)sulfate, followed by the reaction of the unconsumed oxidants with celestine blue. The calibration graphs were linear over the range 10 - 120 microg mL(-1) (method A), 0.5 - 6.0 microg mL(-1) (method B) and 0.6 - 3.0 microg mL(-1) (method C). After validation, the proposed methods were successfully applied to assay of olanzapine in its commercial tablets with mean percentage recoveries of 101.23 +/- 0.10, 96 +/- 0.10 and 94 +/- 0.04%. The mechanism of olanzapine oxidation with N-bromosuccinimide was also proposed.

The use of the new SPE methods for isolation of some tricyclic antidepressant drugs from human serum.

Solid-phase extraction (SPE) methods were applied to isolation of amitriptyline (AMI), imipramine (IMI) and chlorprothixene (CPX) from blood human serum. SPE was carried out using the octadecyl (C(18)) column for isolation of AMI and cyclohexyl (CH) columns in the case of IMI and CPX. The spiked serum samples were used to examine the recoveries of these drugs from C(18) and CH sorbent materials. The volume of serum sample was 500 microl. The recoveries of SPE method using CH cartridge were 100.3+/-1.63% (n=7), 99.7+/-2.3% (n=9) for IMI and CPX, respectively. The recovery of AMI from C(18) cartridge was 99.5+/-1.5% (n=8). Finally, after SPE sample clean-up step the antidepressant drugs were assayed by the own extractive-spectrophotometric methods.

Analytical application of the reactions of amitriptyline with eriochrome cyanine R and pyrocatechol violet.

Eriochrome cyanine R (ECR) and pyrocatechol violet (PCV) have been tested as reagent for the determination of amitriptyline (AMT). They react in aqueous media with AMT forming coloured compounds sparingly soluble in walter. Optimal conditions for the reaction have been established and new extractive-spectrophotometric methods have been developed for the determination of amitriptyline. It can be assayed in the concentration range 8.0-80.0 microg/ml for the ECR method and in the range 1.5-15.0 microg/ml in the case of PCV. The methods were applied to the determination of amitriptyline in albumin and pharmaceutical preparations. The UV-VIS studies of the reagents and the formed compounds were performed.

Studies and analytical application of reaction of imipramine with chrome azurol S.

Chrome azurol S (CAS) was tested as a spectrophotometric reagent for the determination of imipramine (IMP). It reacts in aqueous media with IMP forming pink-red, sparingly soluble in water ion association compound. This compound was quantitatively extracted with chloroform and the absorbance of organic phase was measured at 510 nm. The extraction conditions were studied using a batch method. On the basis of the results obtained with batch method, three-line flow-injection system was constructed. Batch and flow-injection methods were successfully applied for the determination of IMP in pharmaceutical preparation.

[Methods of determination of fluoxetine nad fluvoxamine]. / Wybrane metody oznaczania fluoksetyny i fluwoksaminy.

Two selective serotonin reuptake inhibitors (SSRIs) have been introduced: fluoxetine and fluvoxamine. The literature review shows most methods allow quantitative determination of SSRIs pharmaceutical preparations and plasma, in the lower ng/ml range and that they are, therefore, suitable for therapeutic drug monitoring purposes of this category of drugs. Most procedures are based on investigation of this drugs by spectrophotometric, electrochemical and chromatographic procedures with detection by various detectors.

Simultaneous LC determination of some antidepressants combined with neuroleptics.

A reversed-phase HPLC method with UV detection at 252 nm is presented for the simultaneous determination of some tricyclic antidepressants (amitriptyline, imipramine) and neuroleptics (chlorprothixene, thioridazine) in their quaternary mixtures. Sample analysis was performed on a bonded reversed phase C-18, 5 microm, 250 x 4.6 mm ID (Lichrospher 100RP-18) column using acetonitrile and 0.01 M aqueous solution of triethylamine (1:1) as the mobile phase at 0.9 ml/min. The pH was adjusted to 2.7 with concentrated phosphoric acid. The retention time was for imipramine, amitriptyline, chlorprothixene, and thioridazine 5.8, 6.5, 8.3, 10.8 min, respectively. The linearity was obeyed up to 15 ppm for imipramine and amitriptyline, 12 ppm for chlorprothixene and 10 ppm for thioridazine. The presented method also allows the determination of the mentioned drugs individually in their pharmaceutical preparations.