Determination of Glutaraldehyde by Photometric Microtitration

The deteriorating quality of the environment and consequently stricter emission limits force the produc­ ers of pollutants to modernize their current technolo­ gies, to reduce technologies with toxic materials or to v minimalize emissions. The industrial use of formaldehyde in various fields such as textile, wood, leather, and food process­ ing industry causes a major environmental problem. Formaldehyde is a highly toxic matter which, due to its volatility, not only contaminates working environ­ ment but also remains in residual concentration in final products, so that it endangers consumers. One of the possibilities to solve this problem is to replace formaldehyde with less volatile aldehydes, e.g. glu­ taraldehyde. For this case it will be necessary to have a fast, accurate and reliable method for its determi­ nation even in very low concentrations. In papers published so far on glutaraldehyde de­ termination various methods are mentioned. For ex­ ample, the absorption of ultraviolet radiation is ob­ served. Glutaraldehyde sample shows two maximums at the wavelengths of 235 nm and 280 nm. Absorp­ tion band at 235 nm is ascribed to polymer products which originate in glutaraldehyde solutions. Their ab­ sorption coefficient is about 160 times higher than that of glutaraldehyde and that is why they dominate in the spectrum [1]. Glutaraldehyde can also be deter­ mined by spectrophotometry after reaction with hydroxylamine, hydrazine or methylamine [2]. The Po­ larographie method of determination consists in the conversion of glutaraldehyde to the imino form by reaction with ammonia. This form is more easily re­ ducible than the original compound and in the DPP regime it shows a peak with maximum in the poten­ tial range from -1.2 V to -1.3 V against SCE. The position of the maximum is influenced by the value of pH [3]. Another method is gas chromatography. It can be realized in column filling with stationary phase Carbowax 20 M. Its usage is suitable namely if there are interfering materials in the analyzed solu­ tion. Furthermore, gas chromatography with mass de­ tector is capable to solve completely the composition of glutaraldehyde solution [1]. For the determination of higher concentrations of glutaraldehyde its reaction with sodium hydrogen sulfite is used where appro­ priate bisulfite compound is formed. The unreacted amount of sodium hydrogen sulfite is determined by iodometric titration [4]. This determination is loaded with a systematic error. The reaction is reversible and during the titration of the excess of sodium hydrogen sulfite with iodine the addition product partially de­ composed into aldehyde and sodium hydrogen sulfite. The magnitude of the error depends on the equilib­ rium constant of the reaction of aldehyde used and on the reaction period, on the amount of addition com­ pound, and on the amount of iodine. Besides, for the determination an everyday check-up of the concentra­ tion of the unstable sodium hydrogen sulfite solution is necessary. In this work, for the glutaraldehyde determination its reaction with sodium sulfite was applied, based on the following scheme