A high performance liquid chromatographic method for the measurement of total carnitine in human plasma and urine.

Total carnitine in plasma and urine can be measured by high performance liquid chromatography (HPLC) using the novel fluorescent derivatisation reagents 6'-methoxynaphthacyl trifluoromethanesulfonate and 2'-phenanthrenacyl trifluoromethanesulfonate. Sample preparation for total carnitine analysis involves: extraction of plasma and urine in methanol, the optional addition of serine betaine as an internal standard, saponification of acyl carnitines with calcium hydroxide, followed by derivatisation with 6'-methoxynaphthacyl trifluoromethanesulfonate or 2'-phenanthrenacyl trifluoromethanesulfonate. The derivatives were separated using an alumina column and measured by fluorescence detection. The coefficient of variation was below 5% using internal standard calibration, and recoveries of acyl carnitines after saponification were over 90%. The total carnitine method was shown to be linear at biological levels for plasma (over the range 30-130 micromol/l) and urine (over the range 80-180 micromol/l). Advantages of this method include good precision, accuracy and linearity, the use of fluorescence to gain sensitivity, the small sample volume required and a relatively low sample preparation time.