Abstract: A chemically modified electrode was prepared with 50% NiO, 7% PVC and graphite and packing the mixture into a PTFE cavity (4 mm i.d.). The electrode was used in a FIA system for the amperometric detection of alditols. The wall-jet detection cell also had a Ag/AgCl(3 M KCl) reference electrode and a stainless-steel auxiliary electrode; the working electrode was maintained at +0.5 V. The carrier electrolyte (0.5 ml/min) was 0.1 M NaOH and the sample injection volume was 50 µL. Calibration graphs were linear up to 50 mM alditol (or 25 mM sorbitol) and detection limits were 0.02 M for sorbitol, myo-inositol and xylitol, 0.05 M for dulcitol, 0.08 M for mannitol and 0.1 M for D-arabitol. The RSD for 0.5 mM of analyte were 0.8-1.5% (n = 4-6). The performance of the electrode was stable over 72 h.

Abstract: A vitreous C electrode (0.125 cm2 area) was coated with a polyaniline (PANI) film by galvanostatic polymerization from a solution containing 85 mM aniline in 0.1 M H2SO4 by cycling the potential between -0.1 and 1.1 V (vs. SCE) for five cycles at 50 mV/s. The coated electrode was immersed in 50 mM CuCl2 in 0.1 M H2SO4 for 5 min and then a potential of -0.3 V was applied for 3 min. The Cu-PANI sensor was evaluated for determining amino-acids and polyhydric compounds. Molar response factors for carbohydrates and amino-acids were measured using a FIA system and 0.1 M NaOH as the carrier stream (1 ml/min). A potential of 0.55 V vs. Ag/AgCl was applied to the sensor. A Carbopac PA 1 anion-exchange column (25 cm x 4 mm i.d.) was coupled to the FIA system to analyze carbohydrates and amino-acids. Xylitol, sorbitol, glucosamine, glucose, lactose and sucrose were separated using 0.15 M NaOH as the mobile phase (0.6 ml/min) and the detection limits were 2-6 pmol. Alanine, glycine, lysine methionine and glutamine were separated with 0.1 M NaOH as the mobile phase (0.5 ml/min) and the detection limits were 5-15 pmol. The linear dynamic range was three-four orders of magnitude above the detection limits. The electrode was stable for >=3 h in flowing streams.