Gas-liquid chromatographic and difference spectrophotometric techniques for the determination of benzaldehyde in benzyl alcohol.

Simple, sensitive, rapid and selective gas-liquid chromatographic and difference spectrophotometric methods have been described for the determination of benzaldehyde, an oxidation product of benzyl alcohol, in benzyl alcohol intended for use in the manufacture of parenteral dosage forms. The GLC method comprises chromatography of a mixture of benzaldehyde and benzyl alcohol on a CP-Sil5 WSCOT capillary column after dilution with chloroform and addition of 4-chlorocresol as the internal standard, using nitrogen as the mobile phase and a flame ionization detector. The difference spectrophotometric method involves the measurement of the absorbance of benzaldehyde relative to an equimolar solution in which benzaldehyde has been reduced by sodium borohydride. Both methods are accurate, precise and selective for the determination of benzaldehyde in benzyl alcohol in the presence of benzoic acid, a second oxidation product of benzyl alcohol.