VOLUME 33 NÚMERO 4 AGOSTO 1999© Copyright Faculdade de Saúde Pública da USP. Proibida a reprodução mesmo que parcial sem a devida autorização do Editor Científico. Proibida a utilização de matérias para fins comerciais. All rights reserved.

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Street drugs when in great demand in an illicit market become not only more expensive but are also subject to extensive adulteration and dilution. These fraudulent practices may also contribute to the amplification of toxic effects observed in the abuse of certain drugs including cocaine hydrochloride. The number of seizures reflects the increase of illicit use of cocaine powder in the city of S.Paulo, where the identity of the suspected drug is its hydrochloride form. Routine analytical procedures in enforcement laboratories in Brazil now comprise techniques involving thin layer chromatography for presumptive identification of the drug and eventually gas chromatography for its confirmation or quantification whenever required. The determination of cocaine content, adulterants and diluents in street samples is not only of clinical value but also important for enforcement activities, recognition of its geographical distribution and allocation. So, the aim of this study was to continue examining the quality of cocaine hydrochloride in the illicit market of the city of S.Paulo. Cocaine and adulterant contents were determined as well as the identification of several diluents in 389 out of 1958 samples of "white powder" seized in the city of São Paulo. Thin-layer and gas-liquid chromatography (FID) and GC-MS were used for the determination of cocaine and adulterant contents. Spot-tests and thin-layer chromatography were the techniques applied for the identification of diluents. The results were as follows: neither cocaine nor adulterants were detected in 17 samples (4.4%); of all positive samples (95.6 %) for cocaine, 14% consisted of no more than 200 mg/g; in 70% cocaine purity ranged from 201 to 550 mg/g and in 16% it was not greater than 700 mg/g. The local anesthetics lidocaine and procaine were detected in 19 samples (4,9%) in a range from 10 to 602 mg/g. Caffeine was present in only two samples (179 and 356 mg/g). The main diluents detected were carbonates and bicarbonates (19.2%); silicates (13.8%), sugars (9.59%); starch (5.6%), borate (3.8%) and sulphates(2.8%). Contaminants (secondary products) originated from coca paste refining or decomposition processes were not analysed.