Solid-phase extraction and HPTLC determination of isoniazid and acetylisoniazid in serum. Comparison with HPLC.

A new solid-phase extraction (SPE) and quantitative determination of isoniazid (INH) and its acetyl metabolite (AcINH) in serum by high-performance thin-layer chromatography (HPTLC) is presented. Alkalized serum samples with nicotinamide as an internal standard are applied to an SPE cartridge containing a new SPE sorbent, [poly (divinylbenzene-co-N-vinylpyrrolidone )]. A simple procedure of conditioning, washing, and eluting steps is described. After evaporation of the eluates to dryness and reconstitution, one-dimensional HPTLC is performed on silica gel plates with ethyl acetate-methanol (70:30) as a mobile phase. Quantitation is done by densitometry. Convenient validation parameters are obtained (linearity, limits of detection and quantitation, precision, and accuracy) for INH and AcINH. The method is compared with a high-performance liquid chromatographic (HPLC) technique developed in the laboratory, and satisfactory correlation is found between data from the two techniques. The HPTLC method is sensitive and specific and is used to quantitate INH and AcINH in patient blood serum, and the results are compared with those obtained by HPLC.

Synthesis, characterization and liquid chromatographic behaviours of a new chemically bonded liquid crystal.

A new bonded liquid crystal stationary phase (2OC12) for high-performance liquid chromatography was studied. It resulted from coupling of LiChrospher Si 100 NH2 and a mesogenic carboxylic acid, 4-(4-(4-(3,4-didoceyloxystyrenyl)phenyl-diazenyl)phenyloxy-methylene) benzoic acid (ILC). ILC was characterized with proton NMR and differential scanning calorimetry, while 2OC12 was characterized by solid state 13C NMR and elemental analysis. 2OC12 surface area was determined by the BET method. The chromatographic behaviour of 2OC12 was investigated under both normal- and reversed-phase conditions. The plots of ln k against 1/T showed transition temperatures at 325 and 337 K. Polyaromatic hydrocarbons (PAHs) were separated using hexane, isooctane or hexane-chloroform. Above the transition temperatures, the bonded material exhibited a liquid crystal-like behaviour: (i) the plate number N was always highest possible, and (ii) the more retained the solute the more elongated it was (anthracene is eluted after phenanthrene, chrysene before tetracene, pentacene after dibenzo-a,h-anthracene). Using acetonitrile/water (60/40), reversed-phase data of aromatic hydrocarbons are similar (highest values of N, better resolution below than during the transitions).

Assay of tinidazole in human serum by high-performance thin-layer chromatography--comparison with high-performance liquid chromatography.

Determination of tinidazole in human serum by high-performance thin-layer chromatography (HPTLC) is presented. It includes use of 10 x 10 cm plates coated with silica gel 60 and chloroform-acetonitrile-acetic acid (60 + 40 + 2) as mobile phase. Quantitation was performed by densitometry at 320 nm. The linearity (1-10 ng), precision (6%), reproducibility (5%), recovery (96%), and detection limit (1 mg/L) of tinidazole determination by HPTLC were comparable with corresponding method parameters by reversed-phase HPLC. A satisfactory correlation was found between the 2 analytical methods. The procedure was used to quantitate tinidazole in patient sera.

Direct assay of tinidazole in human serum by micellar liquid chromatography.

A liquid chromatographic procedure for the direct determination of tinidazole in human serum is presented. It includes the use of a micellar mobile phase consisting of SDS (5.10(-2) M): propan-1-ol; (94:6, v/v) and a mu Bondapak CN column with UV detection at 320 nm. No solvent extraction or deproteinization are necessary. The linearity (0.1-10 mg L), the precision (3%), the reproducibility (1.3%), the recovery (99%), and the detection limit (0.1 mg L) in the tinidazole determination are comparable and sometimes greater than the corresponding tinidazole parameters when deproteinization and conventional reversed-phase HPLC are used. One hundred injections of serum samples do not affect the column life. The procedure is applied to ascertain the pharmacokinetics of 10 mg/kg of tinidazole.

Direct determination of theophylline in human serum by high-performance liquid chromatography using zwitterionic micellar mobile phase. Comparison with an enzyme multiplied immunoassay technique.

A liquid chromatographic procedure is reported for the direct determination of theophylline in human serum. It includes the use of a micellar zwitterionic mobile phase [10(-3) mol l-1 3-(dimethyldodecylammonio) propanesulfonate (also known as C12 DAPS)-propanol (97 + 3, v/v) and a muBondapak phenyl column. Detection is based on ultraviolet absorption at a wavelength of 273 nm. After dilution with the mobile phase, the serum is injected into the chromatography; no solvent extraction or deproteinization is performed. The linearity of the method described was excellent over the range 0.5-20 mg l-1. The within-run precision was better than 2%, and the recovery of the theophylline approached 98%. Two hundred direct injections of serum samples did not affect the column life. The total analysis time, including chromatography, was approximately 15 min. As little as 0.5 mg l-1 of theophylline could be detected, and the results were in good agreement with those of an enzyme multiplied immunoassay technique.

Chemical taxonomic studies of cuticular hydrocarbons in locusts of theSchistocerca americana complex (Acrididae: Cyrtacanthacridinae): Chemical relationships between new world and old world species.

Genetics studies gave an insight into the evolutionary systematics of theS. americana complex. Chemical analysis and comparison of the cuticular hydrocarbons of five species of this complex (S. gregaria, cancellata,americana, piceifrons, andpallens) confirmed the species status previously established by hybridization and also revealed new elements. We have shown the existence of two groups of species:S. gregaria andS. cancellata on one hand,S. americana andS. piceifrons on the other.S. pallens does not fit into either of these groups. These analyses thus have shed some light on the possible origins ofS. gregaria vis-à-visS. cancellata for which an explanation is proposed.

Determination of furosemide in rat plasma using HPLC and liquid scintillation.

A rapid and convenient HPLC method for the determination of furosemide in plasma is described. The method uses a buffered mobile phase containing 22% (v/v) acetonitrile. The precision, detection limit and the correlation between the HPLC method and a liquid scintillation determination of furosemide are satisfactory. A pharmacokinetic study of furosemide in the rat is described.