FLOW-INJECTION SPECTROPHOTOMETRIC DETERMINATION OF CHLOROGENIC ACID IN SOME NATURAL SAMPLES

A flow-injection spectrophotometric system was developed and utilized for determination of chlorogenic acid (CGA) with the sample volume of 175 µl using 3-amino-5-methylisoxazole (3A5MI) as diazotizing agent. The method was validated over the concentration range of 1.0-50.0 mg/ml for CGA with correlation coefficient of 0.9994. The limit of detection (LOD) and limit of quantification (LOQ) were 0.30 mg/ml and 0.99 mg/ml, respectively. The rate of sampling was 60 samples/h, with the RSD% and Error% of 2.254% and +3.4966%, respectively. The influences of seventeen phenolic compounds (as interferences) such as dopamine, tyrosine, catechol, tannin, 2, 4-dihydroxybenzoic acid, caffeic acid and p-cresol on determination of CGA were studied. An ultrasonic technique was used for extracting CGA in the samples by using 80% (v/v) methanol aqueous solution. The method was simple, rapid and economical, and was successfully applied for the determination of CGA content in natural sources such as grape, tobacco and black tea plants.