SCIENTIFIC NOTES Simple Method for Concentration of Cerebrospinal Fluid for Protein Electrophoresis

A rapid method for concentrating protein solutions is described. It utilizes dialysis against a dextran solution under vacuum. MOST CLINICAL LABORATORIES use paper electrophoresis for the separa-hon and quantitation of serum proteins. There has been increasing iii-terest in the fractionation of proteins Ill other body fluids, particularly cerebrospinal fluid. Successful paper electrophoresis requires a high protein concentration in the fluid applied to the l)POF strips, If tile total protein content of spinal fluid is normal or only slightly elevated, the fluid must be concentrated as much as 50 times prior to electrophoresis. Ideally, such concentration must be accomplished rapidly and without lleat, to avoid dellaturizatioll of the protein. Methods previously sug-gested have illcluded acetone precipitation, (1) pressure filtration through a eollodion sac (2) and dialysis against a dextran solution (3). Hofsten and Falkbring (4) used dialysis against a solution under vacuum. Cumings (5) concentrated fluid by dialysis against 20 % (w/v) dextran or 30 % (w/v) polyvinylpvrrolidone, but required about 24 hr. for adequate concentration. By using a combination of the methods de-scribed above we have been ai)le to concentrate spinal fluid very rapidly with 110 anparent denaturization of the protein. A collodion bag is mounted in a glass suction apparatus * (Fig. 1). The coliodioll bag is filled with 5-7 ml. of clear filtered cerebrospinal fluid and the suction vessel is filled with a 10 % (w/v) dextran solution. A small vacuum pump is attached to the vessel. The 5-7 ml. of fluid in the collodion bag can he concentrated to about 0.1 ml. ill ai)Out 2 hr. rllhe concentrated fluid is then applied directly t