Plasma hemoglobin determination by recording derivative spectrophotometry.

Recording derivative spectrophotometry (DS) is a technic for analyzing absorbance curves by measuring the derivative (slope) of those curves. The derivative is a mathematical function that enhances rapid changes of direction of a curve and suppresses slow changes. We are presenting a simple, rapid, and reproducible method for determining plasma hemoglobin concentration, even in the presence of bilirubin, myoglobin, or marked turbidity. No toxic reagents are used and, since the analysis is purely physicomathematic, the sample is not altered and can be used for additional tests.