Gas chromatographic determination of guanidino compounds in uremic patients using glyoxal as derivatizing reagent.

The guanidino compounds guanidine, methylguanidine, guanidinoacetic acid, guanidinopropionic acid, guanidinobutyric acid and guanidinosuccinic acid were eluted and separated after pre-column derivatization with glyoxal from an HP-5 column (30 m × 0.32 mm i.d.) with film thickness 0.25 µm at an initial column temperature of 100 °C for 2 min, with ramping of 20°C/min up to 250 °C and a nitrogen flow rate of 3 mL/min. Detection was by flame ionization detection. Linear calibrations were observed within 0.1-20.0 µmol/L, with limit of detection within 0.024-0.034 µmol/L for each compound. The separation was repeatable with relative standard deviation (RSD) (n = 6) within 1.2-1.8 and 1.1-1.6% in terms of retention time and peak height/peak area, respectively. The method was applied for the determination of the guanidino compounds from serum of uremic patients (n = 7) and healthy volunteers (n = 8), and amounts were observed within 1.33-11.71 and 0.07-0.39 µmol/L with RSD 1.1-3.5 and 1.1-3.0%, respectively. The results were further supported by the standard addition method.