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

Franco Tagliaro, G Manetto, Francesca Cittadini, Daniela Marchetti, Federica Bortolotti, M. Marigo

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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 mM imidazole, 5 mM 18-crown-6 ether and 6 mM D,L alpha-hydroxybutyric acid (HIBA), adjusted to pH 4.5. Constant voltage runs were carried out by applying a voltage of 500 V/cm at 25 degrees 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 mM to 16.25 microM, with an r2 value of 0.9994. The limit of detection, based on a signal-to-noise ratio of three, was 9.0 microM. Absolute intra-day RSDs of migration times were <0.40%, while the day-to-day values were < or =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 r2 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 r2 of 0.904 and a Y-intercept of 4.75 mM, in agreement with the existing literature.
Original languageEnglish
Pages (from-to)273-279
Number of pages7
Publication statusPublished - 1999


  • Aqueous Humor
  • Barium
  • Buffers
  • Calcium
  • Electrophoresis, Capillary
  • Humans
  • Hydrogen-Ion Concentration
  • Potassium
  • Quaternary Ammonium Compounds
  • Sensitivity and Specificity
  • Sodium
  • Vitreous Body


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