Simultaneous determination of citrulline and arginine in human blood plasma by capillary electrophoresis with ultraviolet absorption detection

A new capillary electrophoresis method to measure human blood plasma arginine and
citrulline levels in a single run without derivatization was established. After adding homoarginine
as internal standard, plasma proteins were removed by a 90:10 v/v acetonitrile/ammonia
mixture. Arginine and citrulline were detected by an ultraviolet detector at
190 nm and separated in 11.65 and 20.43 min, respectively, by using a 75 mmol/L Tris
phosphate solution at pH 1.2 as a background electrolyte. Limits of detection were 0.8 and
5 mol/L for arginine and citrulline, respectively. Precision tests indicated a good repeatability
of migration times and of peak area both for citrulline (CV% = 0.82 and 3.19) and
arginine (CV% = 0.65 and 2.79). The CV% for intra- and interassay tests were, respectively,
1.84 and 3.23 for citrulline and 1.25 and 1.50 for arginine. Mean recovery was 101.5 and
98.5% for citrulline and arginine, respectively. The performance of the developed method
was assessed by measuring plasma arginine levels in 52 subjects and the data were compared
with those obtained by our previous assay. The new method was then applied to assess
plasma citrulline and arginine in ten chronic kidney disease patients under hypolipidemic
therapy with statin.