A simple, inexpensive, and precise spectrophotometric method for evaluating the concentration of ascorbic acid in CSF samples: data from different neurological pathologies

A method is presented for evaluating the concentration of ascorbic acid in 10 microliters samples of cerebrospinal fluid (CSF) with just ultraviolet (UV) scanning in the 220-300 nm range. The method assumes that the two main UV absorbing CSF components are proteins (with a peak at 280 nm) and ascorbic acid (with a peak at 264 nm). On this basis, the absorbances at those wavelengths are the starting points for a calculation that evaluates the sheer contribution of ascorbic acid to the absorbance at 264 nm. The rapidity of the UV analysis (just a few min), together with the precaution of keeping the samples under argon, along the short preparatory procedure, is especially suitable in the analysis of an air labile substance, such as ascorbic acid. The results of the UV procedure have been checked with parallel HPLC determinations for 19 test CSF samples and the results have shown an excellent correspondence. Finally, data are presented about the evaluation of ascorbic acid concentrations in CSF samples from various neurological pathologies in comparison with normal cases. These data show the interesting result of a significant reduction in the average ascorbic acid CSF level in patients suffering from Alzheimer's disease. However, a decrease in that parameter is found also for a few other pathologies.