A spectrophotometric study was carried out for three proteins assays when modification of their serum procedures using bromcresol green, bromcresol purple and biuret reagents were applied to the determinations of total proteins and albumin in cerebrospinal fluids. A novel concentration device wherein the sample itself was used as the primary diluent for the three reagents concentrated to contain the proper amounts of chemicals in smaller volumes than suggested in their serum procedures allowed reasonable absorbance signals to be obtained. Low molecular weight molecules were separated from the albumin and globulins of the fluids by centrifugal ultrafiltration using a 25K cutoff and spectra were obtained for both high and low molecular weight fractions. Some materials were obtained in the separated ultrafiltrates which gave reactions with all three reagents, reactions which either overlapped the spectra of the albumin reactions or superimposed the spectra obtained with the total protein reaction. A screening procedure for cerebrospinal fluid total proteins or centrifugally ultrafiltercd albumin appears reasonable as an inference from studies made, although further elucidation of the low molecular weight fractions in needed as a confirmation device.
THIS STUDY WAS UNDERTAKEN IN ORDER TO IN-
VESTIGATE the applicability of a total protein and two albumin assays for cerebrospinal fluid (CSF). It would be convenient to be able to utilize the simplicity and specificity of the direct biuret reaction for the routine determination of CSF total protein concentrations. However, as with any procedure, enough color must be produced to facilitate accurate spectrophotometric measurements with relative ease. Although there is no known way to increase the inherent sensitivity of the biuret chromogen itself in the visible range, it was believed to be possible to increase the absorbance advantageously by utilizing the sample rather than the reagent as diluent where the sample volume would be larger than the reagent volume. This is a somewhat novel approach in that a relatively large volume of sample is used to dilute a relatively small volume of reagent in a manner such that the concentration of the various