Determination of glutaraldehyde in solution as its bis-2,4-dinitrophenylhydrazone derivative; determination of geometrical isomer ratios

A reversed-phase HPLC method for the determination of glutaraldehyde in fresh 2% w/v activated alkaline solutions was developed, which used derivatization with 2,4-dinitrophenylhydrazine to its bis-2,4-dinitrophenylhydrazone. The chromatographic conditions were based on those for the Occupational Safety and Health Administration method for the determination of glutaraldehyde in air. The column was a 250 × 4.5 mm Zorbax 5 μm nitrile column, with a mobile phase of acetonitrile: 0.1% v/v aqueous phosphoric acid (62:38) at a flow rate of 1 ml/min. The injection volume was 10 μl and UV detection was at 365 nm. Derivatization was maximal after 80 min. The chromatography was linear in the range 0.02–0.2 μg glutaraldehyde injected and the whole method was linear in the range 0.8–4% w/v glutaraldehyde. The precision of chromatography was in the range 0.3–0.5% relative standard deviation and the within-run precision was ±0.035% w/v (95% confidence limits). Derivatized samples and standards were stable for at least three months in the dark at room temperature: the stability data were used to estimate the day-to-day precision as ±0.09% w/v (95% confidence limits). The mean recovery of glutaraldehyde spiked into Cidex brand glutaraldehyde solution was 97.3%±3.2% (95% confidence limits) and to Asep was 101.8%±3.4% (95% confidence limits). The E,E and E,Z geometric isomers of glutaraldehyde-bis-2,4-dinitrophenylhydrazone were formed in the same proportions in both samples and standards. However, with the isolated bis-hydrazone, the proportions were different, making it potentially unsuitable as a standard as an alternative to glutaraldehyde solution.