Automated determination of nitrite in aqueous samples with an improved integrated flow loop analyzer

Abstract

A compact loop flow analyzer was developed for automated determination of nitrite in aqueous samples based on Griess reaction and spectrophotometric detection. The integrated system employed a customized single chip microcomputer based hardware and laboratory-programmed software written by LabVIEW to control the injection valve, pumps and optical detection module. Experimental parameters related to nitrite analysis, including the reagent volume, sample temperature and salinity were evaluated and optimized. This fully automated analyzer showed a limit of detection as low as 0.02μM with sample throughput of 15h−1. The calibration curves prepared in pure water and low nutrient seawater were consistent over the linear range of 0–10μM (R2=0.999), showing insignificant interference from the common ions in seawater. Different aqueous samples were successfully analyzed using both the present analyzer and the standard benchtop method, and the results from the two techniques showed no significant difference according to the statistical t-test (P=0.95). This compact automatic analyzer is simple, fully integrated, and user-friendly, making it highly suitable for field applications, such as on-line environmental monitoring and underway analysis.