Microsequential injection analysis: Determination of rutin and quercetin in food supplements and pharmaceutical products

Conditions for the oxidative coupling of rutin and quercetin with 3-methylbenztiazolinon-2-hydrazone have been determined under the conditions of microsequential flow analysis (‘lab-on-a-valve’). To provide the high sensitivity of the determination, methods aimed at improving the overlapping of the zones in the flow have been utilized; these are stopped flow and injection of a ‘spacer’ zone. Good results have been obtained using a new approach, the injection of a ‘spacer’ zone with a rate gradient. A program of operations for the automatic spectrophotometric determination of rutin and quercetin has been composed. The analytical range is (6–50) × 10⁻⁵ M for the determination of rutin and (5–50) × 10⁻⁵ M for the determination of quercetin, the productivity of analysis being 59 samples per hour. The procedure has been applied to the analysis of plant extracts and pharmaceutical product Askorutin.