1645
Anal. Chem. 1983, 55, 1645-1647
suggestions in the drafting of this paper.
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I
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3
for review December
lgg2’ Accepted
13,
1983.
Discrete Injection Segmented Flow Analysis of Nutrients in Small-Volume Water Samples Wayne S. Gardner” aind John M. Malczyk National Oceanic and Atmospheric Administration, Great Lakes Environmental Research Laboratory, 2300 Washtenaw A venue, Ann Arbor, Michigan 48 104
Continuous flow, wet chemical analyses usually involve one of two separately developed techniques: segmented flow analysis (SFA) or flow injection analysis (FIA). General features of these techniques have been summarized (1-5) and their relative merits debated (6-10). Although both employ similar chemical reactions to provide detectable end producb, they differ in the “mechanics” of sampling and use different approaches to achieve suitable precision and accuracy. SFA is potentially more sensitive than FIA because sample volumes and chromatophore reaction times for SFA are usually adjusted to achieve hydraulic steady-state chromatophore formation (Le., plateau signal response) (5). In contrast, FIA techniques seldom require steady-state derivative formation but quantify peaks formed after injection of small, precise volumes of sample. Because of sample dispersion during analysis, FIA is not suited to kinetically slow reactions unless stop-flow techniques arle used ( 4 ) . T o investigate nutrient conversions by microbes and invertebrates in sediment water systems, we needed to analyze small (
