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Water-soluble vitamins in multi-vitamin preparations have been analysed by ion-pair chromatography using alkyland amino-bonded phase-column packings [1, 2 and 3]. However, the efficiency of high-performance liquid chromatography (HPLC) as an analytical technique in terms of analysis time can often be fully realized only where rapid sample preparation techniques are available. Ideally this should involve automated sample preparation directly coupled to the chromatograph. The use of continuous-flow techniques to perform the sample preparation in an automatic HPLC system has been described for the analysis offat-soluble vitamins [4 and 5], and for drugs in blood serum [-6 and 7]. The potential application of. the technique to water-soluble vitamins has been outlined in a review by Burns [8-1 of systems for automated preand postcolumn reactions. This article describes a system which analyses nicotinamide, thiamin, pyridoxine and riboflavin in pharmaceutical products at a rate of five to 10 samples/h. FAST-LC-8 column (167 B183 01): a 150x 4.6mm column packed with 5#m particles of porous silica bonded with dimethyloctylchlorosilane. Calibrators: the vitamin standards used were manufactured by Roche; the internal standard, NN’diethyl nicotinamide, was obtained from the Sigma Chemical Company, Poole, Dorset, UK. A daily working standard solution is prepared such that 5 ml contains the nominal quantity per tablet ofeach vitamin to be measured. When preparing this solution the nicotinamide and riboflavin are added to 20 ml water. Sufficient 2 M sodium hydroxide solution is added to dissolve the riboflavin, taking care not to add an excess, which causes riboflavin to decompose, after which the other vitamins are added and the solution is diluted to 50ml with water. The solution is stored in the dark and is stable for 10 h. 5 ml of this standard solution is measured into a sample cup for calibration. A 10o solution of the internal standard is prepared daily and a volume containing approximately as much internal standard as there is riboflavin in the product is measured into a hard gelatin capsule. One of these capsules is then placed in each sample cup.

High-performance liquid chromatographic analysis of water-soluble vitamins in tablets with automatic continuous-flow sample preparation