Optimum TLC system for identification of phenothiazines and tri- and tetracyclic antidepressants

Abstract

Abstract. The TLC separation of twelve drugs from three pharmaceutical groups: phenothiazines and triand tetracyclic antidepressants is presented. Three kinds of eluents and two types of solid phases (RP 18 and Silica gel 60) were used. The composition of mobile phases was optimized by the Simplex method. In the basic optimization criterion the differences between Rf values of the spots corresponding to individual drugs were taken into account. An auxiliary criterion was based on the colour of the spots, which were developed with appropriate reagents. The experimental data obtained during optimization were interpreted using a matrix presentation. In the optimal conditions the differences between positions of the spots enable identification of ten of the examined drugs, but two remained unresolved. Key words: antidepressants identification, TLC, optimization.Depression is one of the most serious and frequent problems of contemporary society. Frequently, as a remedy for this state the physician prescribes tricyclic antidepressants -with or without phenothiazines. Recently the use of these drugs has considerably increased. The specificity of the above mental state and the high frequency of taking the drugs involves a serious danger of overdosing -accidentally or for suicidal purposes. Consequently, the analytical pro-* To whom correspondence should be addressed ** Parts of this paper were presented at the 33rd International Congress on Forensic Toxicology, August 27-31, 1995, Thessaloniki, Greece, and the V th Polish Conference on Analytical Chemistry, September 3-8, 1995, Gdansk cedures capable of both identifying and quantifying these drugs are needed in forensic toxicological practice.A variety of analytical methods for determination of specific tricyclic drugs and phenothiazines and their metabolites has been published, including spectroscopy [1], fluorescence spectrophotometry [2], isotope derivative dilution [3] and thin-layer chromatography (TLC) [4,5], as well as the most popular, nowadays, gas (GC) [6,7] and liquid (HPLC) [8][9][10][11] chromatography, and immunoassay [12][13][14]. None of these methods, however, appears fully satisfactory for our problem, i.e. simple and fast identification of unknown drugs in cases of overdose intoxication or poisoning.The problems concerning identification of phenothiazones and tricyclic antidepressants are caused mainly by their similar chemical structures and, consequently, similar physicochemical parameters (especially within each group), as illustrated in Fig. 1 [15]. Rather poor chemical stability of the drugs causes another problem, solved by determination of phenothiazines together with their metabolites [9,10]. Phenothiazines and their metabolites are known to interfere in the quantification of tricyclic antidepressants [16]. A method based on the interaction of individual or a few drugs with special reagents solves this problem [17,18]. An example of the above mentioned method [17] is phenothiazine structure compounds conversion to diphenylamine by desulfurizat...

Development and validation of stability indicating chromatographic method for determination of impurities in maprotiline pharmaceutical tablets

“…Re commended analytical methods for maprotiline in volve mainly GC in combination with a nitrogen phosphorus detector [4][5][6], HPLC with UV [7][8][9], di od array as well as fluorescence detectors [10][11][12], HPLC with chemiluminescence [13], spectophoto metric, spectrofluorimetric [1,14], and TLC [15]. Methods included in the United States Pharmacopoe ia and European Pharmacopoeia address only the analysis of maprotiline drug substance and tablets without impurities determination in solid dosage forms [16,17].…”