Quantitative assay of diclofenac in biological material by gas-liquid chromatography.

Diclofenac and an internal standard are isolated from biological samples by acid-specific extraction and converted into the corresponding indolones with 0.5% sulphuric acid in 2,2,2-trifluorethanol. The neutral derivatives are isolated by solvent extraction and subjected to gas-liquid chromatography. The use of an electron capture detector permits the assay of diclofenac at levels down to 2 ng per sample.     

Assay of ambroxol in biological fluids by capillary gas-liquid chromatography

A sensitive and rapid method for the determination of ambroxol in biological fluids is described. It comprises a single extraction step, derivatization and selective determination with capillary gas-liquid chromatography (in split-mode) and electron-capture detection. The limit of quantification in plasma is ca. 3 ng/ml. The method is applied to the pharmacokinetics of ambroxol in humans.     

The determination of phanquone in biological material by gas-liquid chromatography.

A gas-liquid chromatographic method for the quantitative determination of phanquone is described, based on the formation of a dimethoxine prior to its extraction from biological material. The sensitivity of the procedure is about 15 ng/ml in biological fluid.     

Quantitative measurements of inorganic mercury and organomercurials in water and biological media by gas-liquid chromatography

Gas-liquid chromatography is used to determine inorganic mercury in the presence and absence of organomercurials in water and biological media after alkylation or arylation. Best results for inorganic mercury were realized with pentacyanomethylcobaltate(III) and tetraphenylborate(III), via the generated methyl and phenyl mercurial. Tetraethyltin, forming ethylmercury, was less satisfactory. Lower detection limits with these reagents were in the range 10–30 ng Hg ml^-1 of medium. Co-determination of inorganic mercury and various organomercurials was carried out by sequential or simultaneous procedures with several column temperatures and packings. Optimal Chromatographic results were achieved with Durapak Carbowax 400 (low K') on Porasil F and 10% DEGS on Anakrom SD.     

Quantitative gas-liquid chromatography of iproniazid and iproclozide.

Analytically packed columns prepared with Versamid-930, Versamid-900, XE-60, and OV-225 as stationary phases were examined for quantitative gas-liquid chromatography of the potent monamine oxydase inhibitor (MAOI) drugs iproniazid and iproclozide. With the aid of chemically related substances as internal standards, response ratios were determined and linearities calculated by regression analysis. Using the 2-butyl analogs of compounds all four column systems permit quantitation of iproniazid and iproclozide with a percent standard deviation sigmaK of about 1% or less.     

Quantitative gas-liquid chromatography of non-protein amino acids.

The quantitative gas--liquid chromatographic analysis of non-protein amino acids, in the presence of protein amino acids, is described. The amino acids were determined as their N-trifluoroacetyl n-butyl esters on an ethylene glycol adipate column. The relative molar responses of 38 amino acids are reported.     

Micro-determination of total phthalate esters in biological samples by gas-liquid chromatography.

A method was investigated in which all of the phthalate esters in biological samples were determined as phthalic acid by gas-liquid chromatography. The method is based on the separation of phthalate esters from the sample with n-hexane, saponification of the esters with an alkaline ethanolic solution to give phthalic acid, purification of the acid by extraction with diethyl ether and column chromatography using silica gel, and conversion of the acid into bis(2,2,2-trifluoroethyl) phthalate with a 2,2,2-trifluoroethanol solution containing boron trifluoride. The derivative obtained is highly sensitive to an electron-capture detector, giving a sensitivity of 0.1 pg. Biological samples fortified with di(2-ethylhexyl) phthalate at levels of 5-100 ppb were analyzed, with recoveries of 70-100%.     

Determination of luxabendazole in biological fluids by high-performance liquid chromatography.

Luxabendazole, a new benzimidazole, is a highly potent broad-spectrum anthelmintic. A high-performance liquid chromatographic method has been developed for its determination in serum and urine samples. In order to optimize the clean-up of samples we compared two procedures: C18 Sep-Pak cartridges and ultrafiltration through a cellulose membrane with a 30,000 relative molecular mass cut-off. In order to obtain the most suitable mobile phase, we studied the influence of pH and acetonitrile content on the capacity factor (k'). Chromatographic separation and quantification were performed on a reversed-phase column packed with 5-microns Nucleosil C18. The mobile phase was acetonitrile-0.05 M phosphate buffer (pH 7.0), (40:60, v/v). The column effluent was monitored by ultraviolet-visible spectrophotometry at 290 nm. The method shows good recovery, precision and accuracy. The lower limit of detection for luxabendazole is 15 ng/ml in serum samples and 25 ng/ml in urine samples.     

Determination of tertatolol enantiomers in biological fluids by high-performance liquid chromatography.

A stereospecific high-performance liquid chromatographic method for the quantification of (-)- and (+)-tertatolol in plasma and urine is described. The method involves solid-phase extraction followed by derivatization with S(+)-naphthylethylisocyanate to form the urea derivative, which is more sensitive to fluorescence detection. The separation of the diastereomeric derivatives was performed by reversed-phase high-performance liquid chromatography. Fluorimetric detection (lambda excitation = 220 nm, lambda emission = 320 nm) allows the quantification of tertatolol enantiomers down to 6 ng/ml. The assay was used to study the pharmacokinetic profile of tertatolol enantiomers following oral administration of racemic tertatolol; preliminary results suggest enantioselective absorption and/or disposition of tertatolol.