Simultaneous derivatization and extraction of free cyanide in biological samples with home-made hollow fiber-protected headspace liquid-phase microextraction followed by capillary electrophoresis with UV detection

A new method is reported for the simultaneous derivatization and extraction of free cyanide in biological samples using home-made hollow fiber-protected headspace liquid-phase microextraction (HF-HS-LPME) followed by capillary electrophoresis (CE) determination. The acceptor phase containing Ni(II)-NH3 (as derivatization agent), sodium carbonate and ammonium pyromellitate (as internal standard) is held within a hollow fiber membrane, affixed to a syringe needle and immersed in the headspace of sample container. The extracted cyanide from the neutral samples forms a stable Ni(CN)42− complex which is determined by CE. Parameters affecting extraction efficiency were investigated and optimized. For optimum peak shapes, the capillary was coated with cetyltrimethylammonium bromide (CTAB). The calibration curve was linear for concentrations of CN− in the range from 0.1 to 20 μmol L−1 (R2 = 0.9987). The LOD (S/N = 3) was estimated to be 0.01 μmol L−1 of CN− concentration. Such a detection sensitivity is high enough for free cyanide determination in common environmental and biological samples. Excellent repeatability of the extraction (RSD ≤ 5.6%, n = 5) was achieved. The feasibility of this method was demonstrated by analyzing human urine and saliva samples with spiked recoveries in the range of 92–103.4%. This work provided an efficient alternative to the present headspace microextraction techniques such as headspace solid-phase microextraction (HS-SPME) and headspace single-drop microextraction (HS-SDME).