High-performance liquid chromatographic determination of memantine in human urine following solid-phase extraction and precolumn derivatization.

A validated HPLC-UV method is presented for the quantification of urinary memantine hydrochloride, a novel medication approved to treat moderate and advanced cases of Alzheimer's disease. The drug and amantadine hydrochloride, the internal standard, were extracted from human urine using SPE. The extract was then buffered and derivatized at room temperature using o-phthalaldehyde in the presence of N-acetyl-L-cyteine.

A rapid first-derivative spectrophotometric analysis of cephalexin and cephradine in human urine.

A rapid, simple, and accurate first-derivative spectrophotometric method has been established for the determination of either cephalexin or cephradine in urine. Quantitative analysis of each antibiotic was achieved by measuring the peak amplitude at 268 nm. The relative and absolute recoveries ranged from 98.

Application of some colorimetric methods for the spectrophotometric determination of phenylbutazone and oxyphenbutazone.

Two methods for determination of phenylbutazone and oxyphenbutazone are described. In the first, naphthoquinone reacts with the product of acid hydrolysis of phenylbutazone or oxyphenbutazone to give an orange colour, having maximum absorption at 480 and 465 nm respectively. In the second, lead tetra-acetate reacts with the hydrolysis product of phenylbutazone (benzidine) to develop a green colour which on heating or addition of excess of reagent changes to yellow, with maximum absorption at 340 nm.

Some spectrophotometric methods for determination of certain antipyretic and antirheumatic drugs.

Heating paracetamol in strongly alkaline medium with 4-nitrosoantipyrine gives a red colour with maximum absorption at 515 nm. Mefenamic and flufenamic acids can be determined colorimetrically after extraction as ion-pairs with Methylene Blue.

Oxidative degradation of 6-selenoguanosine in aqueous solutions.

The degradation of 6-selenoguanosine (NSC 137679) (I) in water and in various buffer systems was investigated. Drug degradation in aqueous media was monitored by high-pressure of I in various chromatography. Some kinetic aspects of the degradation of I in various buffer systems at 25 degrees also were studied spectrophotometrically.

Antioxidants in purification, stabilization, and formulation of the antineoplastic agent 6-selenoguanosine.

6-Selenoguanosine (NSC 137679) was stablized and formulated as a lyophilized parenteral paroduct using ascorbic acid as an antioxidant. In addition to preventing the oxidation of 6-selenoguanosine to the corresponding diselenide in aqueous solution, ascorbic acid reduced the diselenide already in the bulk drug. Dithioerythritol and sodium bisulfite also were evaluated as antioxidants.

Spectrophotometric determination of some phenothiazine derivatives and opipramol with chloramine-T.

This paper describes a spectrophotometric method for the assay of phenothiazines (and also opipramol, which is similar but contains a CC linkage instead of the S atom of the phenothiazines) as the pure drug or in tablets or solutions for injection. The colour is produced by heating a solution of the drug or drug preparation with a solution of chloramine-T. The coloured product can be extracted into chloroform before the colour measurement or the whole process carried out in ethanol solution, the colour of which is then measured.

Synthesis of some 4-hydroxypiperazine and N.N.-dibenzylhydroxylamine esters with potential local anaesthetic activity.

In the synthetic approach to some new local anaesthetics, it was desirable to prepare esters of N1-methyl-N4-hydroxypiperazine and N.N-dibenzylhydroxylamine. Their local anaesthetic activity testing is in progress.

Pharmaceutical analysis of some tranquillizers and antidepressants with iodine monochloride.

A titrimetric method for the evaluation of some tranquillizers and antidepressants is proposed. The method is based on the oxidation of these drugs by iodine monochloride, in strong acid medium, the iodine liberated being titrated with potassium iodate by the Andrews method. The proposed method is applied successfully for the determination of 9 phenothiazines, 1 thioxanthene, 2 acid hydrazides and 1 dibenzazepine containing a double bond (Opipramol).

Spectrophotometric determination of some penicillins with ammonium vanadate.

A spectrophotometric method for determining some penicillins has been developed. A known volume of the penicillin solution-in phosphate buffer of pH 6.8 is boiled with ammonium vanadate solution-in sulphuric acid medium-for 10 min and the absorbance of the colour formed is measured at 750 nm.