A comparison of fluorimetric and colorimetric methods for the determination of α-mannosidase activity in bovine plasma

SUMMARY This paper compares both manual colorimetric and fluorimetric methods for the assay of acidic α‐mannosidase activity in bovine EDTA plasma. The effect of variable blood volumes per 10 ml blood collecting tube has been investigated, and the colorimetric assay conditions adjusted (for example, zinc concentration in pre‐incubation buffer) to cope with low blood volumes resulting in high EDTA/plasma ratios. We have shown that with non‐haemolysed EDTA plasma samples, the two methods give similar results, but for haemolysed samples, the colorimetric method yields significantly lower results than those obtained fluorimetrically.Using the manual fluorimetric method, samples can be assayed more rapidly and simply than by using the colorimetric method. This provides definite advantages in a laboratory receiving variable numbers of samples, or which cannot afford the high cost of automated equipment.