Capillary zone electrophoresis of potassium in human vitreous humour: validation of a new method

• Published in: Journal of chromatography. B, Biomedical sciences and applications Vol. 733; no. 1; pp. 273 - 279
• Main Authors: Tagliaro, Franco, Manetto, Giulia, Cittadini, Francesca, Marchetti, Daniela, Bortolotti, Federica, Marigo, Mario
• Format: Journal Article
• Language: English
• Published: Netherlands Elsevier B.V 15.10.1999
• Subjects: Aqueous Humor - chemistry; Barium - analysis; Buffers; Calcium - analysis; Electrophoresis, Capillary - methods; Humans; Hydrogen-Ion Concentration; Potassium; Potassium - analysis; Quaternary Ammonium Compounds - analysis; Sensitivity and Specificity; Sodium - analysis; Vitreous Body; Vitreous humour; Potassium
• ISSN: 0378-4347; 1387-2273
• DOI: 10.1016/S0378-4347(99)00338-2

The analysis of potassium in the vitreous humour has long been regarded as an important tool in medicolegal and forensic toxicological investigation, particularly for the determination of the post-mortem interval. The present work was aimed at the optimisation and validation of a reliable, simple and fast capillary electrophoresis method for potassium analysis in the human vitreous humour with indirect UV detection at a wavelength of 214 nm. Electrophoretic separations were carried out in a running buffer comprising 5 m M imidazole, 5 m M 18-crown-6 ether and 6 m M d,l α-hydroxybutyric acid (HIBA), adjusted to pH 4.5. Constant voltage runs were carried out by applying a voltage of 500 V/cm at 25°C. The samples were injected in the hydrodynamic mode at the anodic end of the capillary (0.5 p.s.i. for 10 s; 1 p.s.i.=6894.76 Pa). The method showed good linearity in the concentration range from 6.5 m M to 16.25 μ M, with an r 2value of 0.9994. The limit of detection, based on a signal-to-noise ratio of three, was 9.0 μ M. Absolute intra-day RSDs of migration times were <0.40%, while the day-to-day values were ⩽1.72%. Absolute peak area reproducibility was always better than 2.50%. A comparison of capillary electrophoresis with flame photometry on twelve real autopsy samples showed an excellent correlation with an r 2 value of 0.9333. A preliminary application to real cases (20 subjects) was carried out plotting vitreous humour potassium vs. post-mortem interval with a resulting r 2 of 0.904 and a Y-intercept of 4.75 m M, in agreement with the existing literature.