Device for eluting proteins from starch gel by freezing and thawing.

The cetylpyridinium chloride turbidity screening test for glycosaminoglycan excretion discussed by Manley, Severn, and Hawksworth (1968) has been used in this laboratory. In this method (cetylpyridinium chloride turbidity) the precipitation time of four minutes is critical since, after this time interval, turbidity may continue to rise or may fall due to aggregation of particles. As a result of this, false positive results may be found in normal subjects. Precipitation of glycosaminoglycan by cetylpyridinium is also affected by ionic strength and pH, false positive results also being found in urine of high pH or high ionic strength. Therefore, it seemed desirable to try and overcome the critical time dependence and adjust the urine pH with a buffer in such a way that differences in final ionic strength and pH between samples would be negligible. Preliminary experiments showed that a citrate buffer at pH 4-8 was