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SYNOPSIS-A modified technique in paper chromatography whereby components of mixtures are separated into circular zones, is described, together with resultant advantages, such as speed, simplicity of apparatus and reproducibility. Some new methods of detecting colourless adsorbates are outlined, and examples given of the application of the technique in the analysis of dyes, biological materials and inorganic substances. The possible importance of solubility considerations as a guide to choice of developers is discussed.IN a previous communication1 a brief description was given of a new technique in paper chromatography, by means of which the substances under analysis are separated into circular zones, instead of the usual spots or bands. The present paper is intended to provide fuller details of the practice, applications and advantages of this method.According to the technique, two parallel cuts, about 2 mm. apart, are made from the same edge up to the centre of an 11-cm. circular filter paper, and the "tail" so formed is bent at the joint perpendicular to the plane of the paper and cut down to approximately 1.5 cm. in length. Care must be taken to ensure that the parallel cuts are equal in length, otherwise the "tail" will not be squarely perpendicular to the plane of the paper and development may not be truly circular.The solution to be analysed is then placed as a drop on the joint and generally air-dried. The "tail" is then immersed in developing solvent contained in a small capsule inside a Petri dish, the sides of which support the filter paper in a horizontal plane. A glass plate,

Understanding the stability of drugs in a forensic toxicology setting is critical for the evaluation of drug concentrations. Synthetic cathinones are new psychoactive substances structurally derived from cathinone, the psychoactive component of Catha edulis (“khat”), a shrub that is indigenous to the Middle East and East Africa. Previous research has evaluated the stability of synthetic cathinones in biological matrices, including blood preserved with the combination of NaF and K 2 C 2 O 4 used in gray-top tubes. However, it does not assess their stability in blood preserved with Na 2 EDTA, used for some clinical samples. Further, stability in unpreserved urine samples was only studied for two weeks. This research evaluates the stabilities of four Schedule I synthetic cathinones: mephedrone, MDPV (3,4-methylenedioxypyrovalerone), naphyrone, and α-PVP (alpha-pyrrolidinopentiophenone) at 20°C (room temperature), 4°C (refrigerator), and −20°C (freezer). Stability was assessed in methanolic and acetonitrile solutions, as well as in Na 2 EDTA-preserved blood and unpreserved urine. Solutions (1 mg/L) of each drug in each matrix stored in aliquots (100 μL, solvents; 1.2 mL, biological samples; n = 12) at each of the three temperatures for triplicate analysis on days 3, 7, 14, and 30. On day 0 of each study, three additional aliquots of each solution were analyzed. Biological samples underwent solid-phase extraction before analysis. All samples were analyzed in full-scan by gas chromatography-mass spectrometry (GC-MS). The results of this study show that under room temperature and refrigerator storage conditions, mephedrone, naphyrone, and MDPV will degrade in methanol. This degradation starts are early as day 3. Additionally, all four drugs will degrade in Na 2 EDTA-preserved human whole blood samples in at least one evaluated storage environment. However, when in acetonitrile-based working solutions and unpreserved urine samples, they proved to be more stable. Methanolic working solutions and samples of Na 2 EDTA-preserved blood containing these cathinones should be stored in the freezer and used or tested with urgency to ensure that quantitative sample analysis is as accurate as possible in forensic casework.

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