Determination of Phenobarbital in Serum in the Presence of other Barbiturates, Sulphonamides, Salicylates, and other Interfering Drugs

Abstract

A rapid two-dimensional, thin-layer chromatographic procedure for the quantitative determination of phenobarbital in serum is described. 3 ml of serum was extracted with chloroform. One-quarter of the concentrated extract was applied to a kieselgel covered plate (4 tests on a 20x20 cm plate) and two-dimensional chromatography was carried out. The phenobarbital spots were located by means of reference spots, scraped off and extracted with methanol. E₂₄₀nm alkaline - E₂₄₀nm acid was measured and the phenobarbital content calculated. The SD of single determinations was 1.2 mg/l. The specificity was studied in vitro. Phenobarbital could be separated from 18 sulphonamides, 3 antidiabetic drugs, 17 other barbiturates, salicylic acid, salicylamide, and phenytoin. The separation from metabolites was not investigated.