Pfaff, Kenneth J

Abstract A chromatographic system for organic acids has been developed, with improved stability, resolution, and sensitivity for measuring organic anions in biological samples. A calibration mixture containing 100 nEq each of 18 organic anions was clearly resolved, with a signal-to-noise ratio greater than 100:1. The baseline was essentially flat throughout the chromatogram. With scale expansion, the sensitivity limit was about 0.2 nEq per constituent. The width of each peak at half its height was 1 to 2% of its retention time. The system could thus resolve 50 or more constituents. In chromatograms of whole blood and urine more than 40 compounds are resolved. The system is basically a liquid-liquid partition between an acidified aqueous phase on silicic acid and a gradient of nonpolar and polar solvents. Eluted organic acids are detected photometrically by mixing the column effluent with a miscible solvent containing a suitable indicator. Samples require about 6 h for complete chromatography at present.

Abstract A glucose oxidase-peroxidase method for continuous automated monitoring of blood glucose has been developed. The response is linear over the range 0-800 mg/100 ml. Sensitivity can be maintained for 24 hr or longer and can be restored by rinsing the analytic system with sulfuric acid to permit studies of longer than 48 hr in duration. A precision of ± 1% can be maintained between rinses for samples containing 100-600 mg of glucose per 100 ml. This method is satisfactorily specific for glucose: The response with other sugars is less than 1% of the response obtained with the same concentration of glucose. Ascorbic acid causes no significant inhibition of the response to glucose. The inhibition by uric acid has been reduced fifty-fold compared to that in other methods. Transit through the sampling catheter and analytic system requires 15 min. Timed from the first detectable response to a change in concentration, 25% of total response is achieved in 30 sec and 90% in 80 sec. Fifty percent of an oscillation with a half-period of 45 sec can be detected; no oscillations this short were observed in records of human blood glucose. Applicability and feasibility of this method have been demonstrated in over 2000 hr of repeated blood glucose recordings in 12 diabetic and 6 normal subjects.