Plasmatic and urinary pyroglutamic acid measurement by capillary zone electrophoresis in chronic poisoning with acetaminophen in children

Abstract

An increase of pyroglutamic acid, or 5-oxoproline plasmatic concentration was reported in metabolic acidosis observed after chronic intake of some drugs, as acetaminophen. We developed a simple, fast and reproducible method by capillary zone electrophoresis using a commercial Anion Analysis Kit® to quantify pyroglutamic acid, in plasma after acetonitrile precipitation, and after simple dilution in urines. Fumaric acid was used as internal standard in both. In less than 7min, the method separates pyroglutamic acid from other organic and inorganic anions. The method is linear between 0.25 and 10mmol/L in plasma, and 0.15 and 10mmol/L in urines. The quantification limits are 0.25mmol/L and 0.15mmol/L for plasma and urines, respectively. For repeatability and intermediate precision, the variation coefficients are less than 15% and the bias values are between ±10%. For the 2 matrices, the recoveries are between 88% and 101%. The method does not interfere with physiological organic and inorganic anions. Pyroglutamic acid concentrations measured in 9children were between 0.45 and 3.96mmol/L in the plasma and between 0.15 and 3.2mmol/L in the urine. No correlation between pyroglutamic acid and acetaminophen concentrations were found, regardless of the biological media. In conclusion, our method measures pathophysiological concentrations of pyroglutamic acid and highlights the increase in other organic acids that may explain metabolic acidosis due to chronic acetaminophen intake.