A spectrophotofluorometric method for the estimation of barbiturates-separated by instant thin layer chromatography

Sensitive thin-layer chromatographic method for urine screening of barbiturates

A simple and sensitive thin-layer chromatographic (TLC) method is described for the detection of barbiturates and other sedatives at therapeutic levels in the urine. The method consists of an extraction followed by TLC on a single plate in a solvent system which separates the barbiturates from most of the other drugs. The upper portion of the plate is sprayed with a new visualization reagent, N,2,6-trichloro-p-benzoquinone imine, followed by heating. The barbiturates appear as blue spots. This procedure is capable of detecting barbiturates at levels of 0.1 mg/dl in urine.

Thin-layer chromatographic determination of barbiturates and phenytoin in serum and blood

A method is described for the measurement of blood, serum and/or plasma levels of hexobarbital, phenobarbital, cyclobarbital and phenytoin by ultraviolet reflectance photometry on thin-layer chromatograms. The lowest concentrations measured were 0.3-0.7 mug/ml. The accuracy was similar to that of gas chromatographic procudures. For phenytoin determinations 5-(p-methylphenyl)-5-phenylhydantoin may be used as internal standard. The method has been applied to clinico-pharmacological assays, to the measurement of cyclobarbital elimination in man following a therapeutic dose, and to the study of phenobarbital kinetics in rats using serial blood samples.

Why Measure Blood Barbiturates?

Phenobarbitone levels in the blood do not always provide a reliable guide in the management of the poisoned patient. They may rise in response to active treatment though the patient may be improving clinically. Some reasons for this are considered, with illustrations from three cases. It is concluded that the poor correlation of phenobarbitone levels with a patient's condition is due not to inadequate analytical techniques but to the poor representation of the “whole body” situation by a single blood specimen. The usefulness of analysing such specimens is questioned.