CAPILLARY ION ANALYSIS OF POTASSIUM CONCENTRATIONS IN HUMAN VITREOUS-HUMOR

Capillary ion analysis (CIA) is a form of capillary electrophoresis wh ich uses the differential electrophoretic mobility of ions to perform a separation of an ionic mixture. Application of this technique for di rect detection of potassium concentrations in human vitreous humor was the purpose of this investigation. CIA was performed using a Waters Q uanta 4000 Capillary Electrophoresis System with a 745 Data Module usi ng a 75 mu m x 60 cm capillary and a run electrolyte of 67.7 mg hydrox yisobutyric acid (HIBA), 52.8 mg 18-crown-6-ether and 64 mu L UV-CAT-I reagent (4-ethylbenzylamine) in a volume of 100 mt water (18 Mohm) wi th a voltage of 20 kV using ultraviolet absorption detection at 214 nm . Migration times were: ammonium ion, 2.86 min; potassium, 3.24 min; c alcium, 3.84 min; sodium, 3.98 min; barium (internal standard), 4.68 m in; and lithium, 4.79 min. Correlation coefficients (r) between peak a rea ratios and concentration ranges of 2.5-144 mmole/L (100-1000 ppm) were from 0.9855 to 0.9999. Coefficients of variation (CV) ranged from 1.45 to 13.8% between days and from 1.38 to 9.43% within-day. Applica tion of this methodology to twenty-five vitreous humor specimens from forensic cases was compared to analysis by ion-specific electrode for potassium concentration. Comparison of CIA to ion-specific electrode a nalysis of vitreous humor potassium concentrations revealed a correlat ion coefficient of 0.9642. CIA is applicable to forensic analysis of p otassium concentration in forensic vitreous humor specimens. Quantitat ion of numerous cation concentrations is possible by direct CIA of vit reous humor.