Colorimetric microdetermination of l-lactate in deproteinized blood

The method by MacQueen and Plaut was modified to devise simple microdetermination method of l-lactate which is applicable to deproteinized blood sample. Blood was deproteinized with addition of 25% (w/w) trichloroacetic acid (TCA), and 0.075 M 2-amino-2-methyl-1, 3-propanediole (AMPD) was used to make pH of the reaction mixture optimal. It was validated in recovery and precision study, and showed good correlation with usual UV method; correlation coefficient was 0.985, and slope was 0.994. TCA-blood mixture may be kept at room temperature for at least 2 hr without centrifugation, and the supernatant may be preserved for at least 2 weeks at 4 degrees C.