Microplate fluorimetric assay of soil enzymes

Use of the microplate format in soil enzyme assays offers the advantages of simultaneous analysis of multiple enzymes using a small quantity of soil. Quantification of 4-methylumbelliferyl (MUF) in soil requires a calibration curve be developed for each soil. For quantitative detection, it is also important to treat standards, blanks, and samples in exactly the same manner, prepare all solutions using the same reagents and preparation techniques, and measure at the same temperature after the same amount of time. This chapter describes MUF-based microplate format enzyme assays using four enzymes involved in transforming carbon, nitrogen, phosphorus, and sulfur as examples. Buffering pH in these assays is based on reports by Tabatabai and Parham and Deng. Interferences from soil matrices in the detection of MUF are corrected by employing additional controls and calibration curves that are developed in the matrix for each assayed soil.