Simple high-performance liquid chromatographic analysis of free primary amino acid concentrations in rat plasma and cisternal cerebrospinal fluid.

The quantitation of 16 acidic, basic, small and large neutral amino acids was performed using 10-microliters sample aliquots of cisternal cerebrospinal fluid (CSF) and blood plasma of rats. The analytical technique is based upon a two-buffer HPLC system with fluorimetric detection of pre-column derivatized primary amino acids with o-phthaldialdehyde (OPA). A modification of a well established method, the power of the present technique comes from an improved resolution and sensitivity by installing a column heater adjusted to 43 degrees C and strictly reducing any contamination by background amino acids. The analysis is simplified by separating the amino acid derivatives with a linear buffer gradient and less time consuming by the use of a short analytical column with a higher flow-rate. Analytical precision, linearity of response and reproducibility were highly acceptable at both CSF and plasma concentrations of amino acids without changing any of the separation or detection parameters.