title: Capillary zone electrophoresis of potassium in human vitreous humour: validation of a new method.
abstract: 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.
authors.affiliation: Institute of Forensic Medicine, University of Verona, Policlinico, Italy.
authors.forename: F
authors.initials: F
authors.lastname: Tagliaro
authors.forename: G
authors.initials: G
authors.lastname: Manetto
authors.forename: F
authors.initials: F
authors.lastname: Cittadini
authors.forename: D
authors.initials: D
authors.lastname: Marchetti
authors.forename: F
authors.initials: F
authors.lastname: Bortolotti
authors.forename: M
authors.initials: M
authors.lastname: Marigo
mesh_terms: D001082:Aqueous Humor / Q000737:chemistry*; D001464:Barium / Q000032:analysis; D002021:Buffers; D002118:Calcium / Q000032:analysis; D019075:Electrophoresis, Capillary / Q000379:methods*; D006801:Humans; D006863:Hydrogen-Ion Concentration; D011188:Potassium / Q000032:analysis*; D000644:Quaternary Ammonium Compounds / Q000032:analysis; D012680:Sensitivity and Specificity; D012964:Sodium / Q000032:analysis; D014822:Vitreous Body
chemical_list: D002021:Buffers; D000644:Quaternary Ammonium Compounds; D001464:Barium; D012964:Sodium; D011188:Potassium; D002118:Calcium