RESUMEN
A valve-free continuous flow method and instrument were established,with only a multi-channel pump for delivering the sample and reagent,and without any injection or solenoid valves and sample loop for selecting and adding the sample or reagent.Nitrate was reduced to nitrite with Cu-Cd reductant column,and then detected with spectrophotometric detector.The proposed method was suitable for determination of nitrate at normal level in most of estuary and coastal seawaters.With the optimum parameters,the linear range and detection limit were 5-180 μmol/L and 0.27 μmol/L,respectively.The samples of 10 and 80 μmol/L nitrate were continually measured for 11 times,and the relative standard deviations were 1.4％ and 1.3％,respectively.The recovery of real samples at different salinity ranged between 99.4％ and 106.1％.There was no significant difference in the analytical results between the proposed method and the flow injection analysis (FIA).In comparison with FIA,the method and instrument were less cost and easy to operate,and was suitable to be applied in general laboratories and field for continuous monitoring.The method was successfully used to measure the nitrate in seawater samples in Xiamen's Western Harbor and monitor nitrate in Jiulongjiang estuary.
RESUMEN
0.999 0, and RSDs were not more than 3.26%. The recovery rates were 94.12%-104.30% .The lowest detected concentration was 1.43 mg/L. There was no significant difference between the results of this method and Na2EDTA titration. Conclusion The method was rapid, accurate and highly sensitive.
RESUMEN
Objective To establish a continuous flow analytical method for determination of potassium in environmental water sample.Methods The concentration of patassium in environmental water sample was determined by ALLIANCE auto-matic analyzer,and its data were compared with the data obtained from atomic absorption spectrophotometry.Results The de-tection limit of this method was0.5?g /ml.The method revealed linear relationship at the potassium concentrations of5-1000?g /ml.The recovery rate of standard addition method ranged from to97%to102%.The relative standard deviations were0.82%-1.23%.Conclusion The contents of potassium in environmental water samples could be accurately and rapidly deter-mined by continuous flow analysis.