Gas Chromatographic Determination of Guanidino Compounds Using Hexafluoroacetylacetone and Ethyl Chloroformate as Derivatizing Reagents

Guanidino compounds guanidine, methylguanidine, guanidinoacetic acid, guanidinobutyric acid, guanidinopropionic acid, and guanidinosuccinic acid after derivatization with hexafluoroacetylacetone and ethyl chloroformate at pH 9 in aqueous phase, eluted, and separated from gas chromatographic column HP-5 (30 m × 0.32 mm id) with film thickness of 0.25 μm at an initial column temperature 90 °C for 2 min, followed by heating rate of 10 °C min^?1 up to 220 °C with nitrogen flow rate of 1 mL min^?1. The detection was by flame ionization detector. The linear calibration ranges of each of guanidino compounds were obtained within 1–10 μg mL^?1, and the limit of detection was within 0.014–0.19 μg mL^?1. The derivatization and gas chromatography elution and separation were repeatable in terms of retention time and peak height/peak area with relative standard deviation (RSD) (n = 4) within 1.7–2.9 % and 1.4–2.8 %, respectively. The method was applied for the determination of guanidino compounds from deproteinized serum of uremic patients and healthy volunteers, and was found in the range below the limit of quantitation (BLOQ) to 1.25 μg mL^?1 with RSD within 1.4–3.6 %, and BLOQ to 0.4 μg mL^?1 with RSD 1.3–3.4 %, respectively. A number of pharmaceutical additives did not effect the determination with RSD within ±3.1 %.