Surface-activated chemical ionization in the analysis of arginine in plasma samples

Alterations of arginine plasma levels are involved in several disorders of amino acid metabolism such as hurtnup, argininosuccinic aciduria, histidinemia, citrullinuria, and cystinuria. In this work a new liquid ionization source, surface-activated chemical ionization (SACI), has been used to analyze arginine in human and rat plasma samples. Arginine was extracted and diluted ten times through protein precipitation. The diluted arginine samples were then analyzed using an ion-exchange chromatographic column coupled with the SACI source and an ion trap analyzer using MS(3) monitoring in order to increase the sensitivity and specificity of the analysis. The multiple-point standard additions method was used to quantify the arginine. This method was employed to eliminate the matrix effect that affects all liquid ionization sources (APCI, ESI, SACI, etc.), and also does not require use of an internal standard. High-quality results in terms of sensitivity, limit of detection, lower limit of quantitation, linearity and reproducibility, are demonstrated.