Continuous and stopped flow injection for catalytic determination of totaliodine in urine

This paper describes the use of flow injection (FI) techniques for the dete rmination of iodine in urine, based on the catalytic effect of iodide in th e redox reaction between Ce(IV) and As(III). The proposed procedures minimi ze errors in the conventional batch method arising from the reading of abso rbance at a fixed time after addition of Ce(IV) reagent. Two FI systems, fo r the continuous and stopped modes of operation were assembled. In the cont inuous-FI system, a thermostated bath was used to increase the sensitivity. However this is not necessary for the stopped-FI system. The two systems a re comparable in terms of sensitivity, sample throughput and detection limi t. The continuous-FI and the stopped-FI exhibited detection limits (3 sigma ) of 2.3 and 3 mug I 1(-1) respectively. Both systems have equal sample thr oughputs of 35 samples h(-1). Calibration plots for both techniques are lin ear. The FI procedures provide very short analysis times compared to the ba tch procedure. Using the linear regression test, then is no significant dif ference between the results from the four methods, i.e., continuous-FI, sto pped-FI, conventional method and ICP-MS. The proposed methods are readily a pplicable for automation and can be an alternative to the conventional proc edure for the survey of the iodine deficiency disorder. A condition for sam ple digestion is also proposed to reduce the amount of chloric acid require d for complete digestion. Kinetic information of the reaction can also be o btained from the stopped flow mode.