An unknown guanidino-positive peak has been identified in urines of three sisters affected with hyperargininaemia. Identification was made on the basis of its similarity with the liquid and thin-layer chromatographic characteristics of enzymatically synthesized 2-oxo-5-guanidinovaleric acid. Identification was also made by combined gas chromatography-mass spectrometry of the unknown compound pe...

Stir bar sorptive extraction is an innovative sample extraction technique that can be used to process blood, urine, and tissue samples for routine drug screening in the forensic toxicology laboratory. The Gerstel Twister desorption unit (TDU) system is a multifunctional desorption unit capable of determining the presence of analytes from liquid samples after extraction using the Twister stir ba...

valproic acid (vpa) is one of the mostly used antiepileptic drugs that may have some side effects so, it is highly recommended to evaluate its serum concentrations. the aim of this study was to develop a simple, fast and economic method using gas-chromatography equipped with flame ionization detector (gc/fid) and vpa analysis. to do this, 200 µl of serum was mixed with an aliquot of caproic aci...

A sensitive, selective, and simple gas chromatography-mass spectrometry method is developed for quantitation of phenazopyridine (PAP) in human plasma using internal standard (diazepam). PAP and IS are extracted from plasma by liquid-liquid extraction and analyzed on a DB-5MS column with mass selective detector. Excellent linearity is found between 5-500 ng/mL (r = 0.9992, n = 7) for PAP in huma...

fatty acids play important roles in biological systems and the newborns fatty acids requirements are covered only by the milk. it is of particular interest to qualify the content of the fatty acids in the milk. this study was performed to determine the levels of some fatty acids in the infant formulas and also to describe a method without derivatization for the fatty acids analysis and applying...

An analysis is made of some of the practical problems of ion-exchange chromatography. A comparison is made with gas—liquid chromatography and this leads to the suggestion that improvements can be made in the monitoring system and in the selection of eluents for specific separations. The need for a general purpose gradient elution apparatus is stressed. Some theoretical aspects of several factor...

Under normal circumstances, a test specimen is reported as "negative" when the response of the analyte is absent. However, if the intensity of the internal standard (IS) is low, indicating interference factors, the test could be considered "inconclusive." A quantitative hypothesis, A=(R x I x S)/L, serves as the "cutoff" for the acceptable signal-to-noise (S/N) ratio for the IS in making "negat...

the dried aerial parts of scutellaria lateriflora l. (family labiatae), have been used for many years as a domestic remedy for epilepsy, hysteria, and nervous tension states. although several phytochemical investigations have been made regarding the constituents present in this species (i. e. flavonoids, iridoids), none has been recorded concerning the cuticular wax. using thin-layer chromatogr...

Sampling and sample introduction are two key steps in quantitative gas chromatography. In this thesis, a development of a previously described sampling technique as well as a novel concept for sample introduction in gas chromatography are presented. The thesis is based on two papers. Paper I describes a method for preparing physically mixed polymers for use as sorbent phases in open tubular tra...

Compounds with primary amino groups react with o-phthalaldehyde in solution to yield highly fluorescent products. This reaction is now in wide use for detecting amino acids and amines in liquid-chromatography effluents. We report here a method for using o-phthalaldehyde to detect primary amines in the effluent of a gas-liquid-chromatographic column. The effluent gas, nominally 20 mL/min, is del...