Isolation of acylcarnitines from urine: a comparison of methods and application to long-chain acyl-CoA dehydrogenase deficiency.

Carnitine esters from acetylcarnitine (C2 acyl chain) to octadecanoylcarnitine (C18 acyl chain) can be extracted from urine with recoveries of greater than 80%. However, to obtain such recoveries, it is important to choose the method of extraction appropriate to the acylcarnitines of interest. For acylcarnitines with acyl chain length C2 to C8 (acetylcarnitine to octanoylcarnitine), an ion-exchange procedure is recommended. Acylcarnitines with acyl chain length C8 to C12 (octanoylcarnitine to dodecanoylcarnitine) are best isolated from carefully acidified urine by solvent extraction with butan-1-ol. For long-chain acylcarnitines, C10 to C18 (decanoylcarnitine to octadecanoylcarnitine), solvent extraction of unacidified urine with hexan-2-ol is particularly simple and effective.