Determination of d-lactate by enzymatic methods in biological fluids: study of interferences

摘要

Analysis of nondeproteinized samples with an enzymatic method to determine d-lactate indicated interferences. The presence of l-lactate dehydrogenase (LD) and l-lactate in the sample led to underestimation of d-lactate content when a sample blank was processed and overestimation when it was omitted. We proved that this interference is not due to lack of d-LD stereospecificity. Moreover, assessment of d-LD and l-LD K M for NAD+ allowed us to rule out the different affinities for this coenzyme as a cause of the interference. Our results underline the importance of deproteinizing samples for d-lactate analysis when enzymatic methods are used. The ultrafiltration procedure we propose is convenient and shows acceptable mean recovery (108%) and good imprecision (within-run CV = 4.2% and 3.0% for d-lactate at 31 and 107 μmol/L, respectively; between-run CVs were 7.3% at 49 μmol/L d-lactate and 3.1% at 115 μmol/L d-lactate).