Measurement of nutrients in saline and hypersaline waters by discrete analyzer colorimetry without matrix matched calibration standards.

Automated, colorimetric analysis of nutrients in samples with high and variable salinity can be time consuming due to the need to matrix match calibration and reference solution matrices with those of samples-particularly when using flow-based analyzers that are prone to detector artifacts caused by optical inhomogeneities, "schlieren," that form at interfaces between samples and deionized water carrier or wash solutions. Such detector artifacts do not occur in discrete analyzers. Here we report spike recoveries when nitrite plus nitrate, nitrite, ammonia, orthophosphate, and silica were determined in estuarine waters, seawater, and hypersaline surface water samples without calibrator matrix matching using an automated discrete analyzer set up with standard colorimetric methods.