2378
Anal. Chem. 1983,55,2378-2382
Determination of Reactive Silicate in Seawater by Flow Injection Analysis Jens Thomsen, Kenneth S. Johnson,* and Robert L. Petty Marine Science Institute, University of California, Santa Barbara, California 93106
Flow lnjectlon analysls was used to automate the determlnatlon of slllcate In natural waters by the molybdenum blue method. The analysis rate Is 80 per hour when a contlnuous stream of seawater Is analyzed. Thlrly dlscrete samples can be analyzed In dupllcate per hour. The relative preclslon was better than 1% for slllcate concentrations above 10 pM. A detection llmlt of 0.5 pM SI was achleved. The refractive Index Interference has been ellmlnated. This allows a low detection llmlt to be obtalned for a wlde range of sallnltles. A lower detection llmlt of 0.1 pM SI can be obtalned wlth longer reaction coils and a lower sampllng rate. There Is a small salt effect and little Interference from phosphate. The method was tested on an oceanographic crulse from Monterey Bay (Callfornla) to San Franclsco Bay.
Silicon is an essential and, in some cases, growth-limiting micronutrient for marine organisms that form siliceous tests ( I ) . Concentrations of available silicon are often low (
