MULTISITE DETECTION IN FLOW-ANALYSIS .3. PERIODATE TUBULAR ELECTRODE WITH LOW INNER VOLUME AS A RELOCATABLE DETECTOR

Periodate oxidation was exploited for the determination of sucrose and glycerol with potentiometric monitoring of the remaining periodate. F or this task, a tubular electrode with a small inner volume and a fast response time was used in a flow-injection procedure with multi-site detection. With parallel monitoring, two almost identical systems shar ed the same detection unit. After peak maximum measurement, the detect or was displaced to the other analytical channel, and then washing tim e was no longer a limiting factor with respect to sampling rate. The a pproach was applied to the determination of glycerol in soaps, deterge nts and lixivia samples. The sampling rate was improved by 85% relativ e to a comparable conventional flow-injection system without impairing other favourable analytical characteristics. The reagent consumption was only 190 mu g of NaIO4 per determination. With serial monitoring, measurements were made at two manifold sites under different sample pr ocessing conditions. In this way, sucrose was determined in sugar-cane juice and syrups by monitoring the sample zone prior to and after in- line acidic hydrolysis. The proposed system is very stable, no baselin e drift being observed during 4-h operation periods. It provides 50 me asurements per hour and yields precise results (R.S.D. usually < 2%) i n agreement with liquid chromatography. Clarification of the sample is not required.