Long-wavelength stopped-flow fluorimetric determination of lysozyme

The use of Cresyl Violet and sodium dodecyl sulphate for the kinetic fluorimetric determination of lysozyme from dynamic fluorescence measurements at a long wavelength in the range near 600 nm was explored. The high initial rate of this system allows analytical measurements to be made within ca. 2 s after the reactants are mixed, by using the stopped-flow mixing technique, which makes the method applicable to automatic routine analysis. The calibration graph is linear over the range 0.5-40 mug ml(-1) lysozyme hydrochloride and the detection limit of 0.19 mug ml(-1). The precision is less than 2% (relative standard deviation). The results obtained by applying the proposed method to the analysis of pharmaceutical samples with no pretreatment shown how readily it can be adapted for routine analyses. Analytical recoveries ranged between 94.0 and 104.0%.