COMPARISON OF HIGH-PERFORMANCE LIQUID-CHROMATOGRAPHIC, SPECTROPHOTOMETRIC, AND FLUOROMETRIC METHODS FOR DETERMINING CHLOROPHYLL A CONCENTRATIONS IN ESTUARINE SEDIMENTS

There are currently three methods that are used for routine measurements of chlorophyll (Chl)alpha concentrations in extraction solvents. High-performance liquid chromatography (HPLC) provides the most accurate measurement of Chl alpha, but requires ca. 20 to 25 min processing time for each sample. Spectrophotometric (SPEC) and fluorometric (FLUO) methods are less accurate, but require much less (1 to 5 min) processing time per sample. The purpose of this study was to determine the accuracy of SPEC. and FLUO methods for measuring Chl alpha extracted from estuarine sediment samples. The SPEC method overestimated the Chl alpha concentration by 16% but the relationship between SPEC and HPLC values was constant. The FLUO method underestimated Chl alpha concentrations by 3% and the relationship to HPLC determined values was also constant. A paired-comparison of SPEC and FLUO methods showed that although the values were linearly correlated, the FLUO method produced lower Chl alpha values than the SPEC method. Although SPEC and FLUO methods overestimate and underestimate (respectively) sediment Chi a concentrations, the relationship was linear across a wide range of naturally occurring concentrations. Both SPEC and FLUO methods are suitable for showing relative differences in Chl alpha concentrations, but should be corrected when absolute concentrations are important.