Simultaneous Determination of Elon and Hydroquinone in Photographic Developers

A sample of the developer solution is diluted with a pH 5 acetate buffer and its absorbancy
^†
measured at two wavelengths in the ultraviolet region. The concentration of Elon‡ and hydroquinone in a fresh unused developer solution can be determined directly from these two absorbancies. Used or old developer solutions are analyzed by extracting the unoxidized Elon and hydroquinone with ethyl acetate. Absorbancy measurements made on the system before and after extraction serve to determine the amount of Elon and hydroquinone present.