Anal. Chem. 1982, 54, 1185-1187
1185
Determination of Phosphate in Seawater by Flow Injection Analysis with Injection of Reagent Kenneth S. Johtnson" and Robert L. Petty Marine Science Institute, Unlversity of California, Santa Barbara, California 93 106
A modlflcatlon of flow Injection analysls is descrlbed that can Increase the sensitlvlty of an analysis. The technlque was tested by udng It for the determlnation of dlssolved phosphate in seawater with ithe coiorlmetrlc phosphomolybdate complex method. The procislon of the method is 1.5% at the 3 /AM level, and the de9ectlon limit Is 0.05 pM. Samples can be analyzed at raters exceeding 90 samples per hour.
This paper describes a high sensitivity variation of the technique of flow injection analysis (FIA). The variation consists of injectiing small volumes of reagent into the flowing sample stream, rather than the conventional injection of sample into a flowing reagent (or inert carrier) stream. Injection of reagenits into the sample or carrier stream in FIA has been used before to minimize reagent consumption ( I ) and to produce large pH gradients (2). However, the potential of this technique to enhance analytical sensitivity has not been previously recognized. During its relatively short lifetime, the technique of flow injection analysis has proven to be highly versatile and capable of automating a wide variety of analytical procedures (3-6). A simple FIA system typically consists of a length of small bore (
