Modification of an Ultraviolet Spectrophotometric Determination of the Active lngredients in APC Tablets Michael K. Yarnelle and Kevin J. West Indiana University-Purdue University at Fort Wayne, Fort Wayne, IN 46805 Analgesic tahlets have been used over the years in a variety of laboratory experiments that quantify the active ingredients in the tahlets. These auantitative methods include ultraviolet spectrophotometr; (I), infrared spectrophotometry (2),thin-layer chromatography 13-51, titrimetry (61, and high-performance liquid chromatography (7-9). A common analeesic tahlet used in these methods is APC tablets. ~ecently,-the manufacturers of APC tablets have replaced phenacetin with paracetamol (a synonym for acetaminaphen) in their formulations because of the side effects that phenacetin may cause. The more recent high-performance liquid chromatography methods tend t o avoid using APC tahlets while employing other analgesics containing phenacetin. T h e second semester of analytical chemistry has included a determination of the comnonents in APC tahlets usine an extraction procedure followed by an ultraviolet spectroGhotometric measurement. With the older APC tablets containing phenacetin, this method worked well. However, prohlems were encountered when the newer APC tahlets containing acetaminophen were used with the same procedure, the acetaminophen was not found in either of the solutions suhjected to the ultraviolet spectrophotometric analysis. It was decided that if an appropriate modification could he found, the procedure should he retained as an experiment for the analytical course as it utilized a nra1 sample. Experimental The extraction prwedurc used is similar to the m e fuund in Christian'sonolytical chemistry textbook ( 1 I . A neighed APC ublrt is crushed and d~rsalvrdm 811 mL of mrthvlrne chloride. This methylene chloride solution is then extracted with two 40-mL portions of 4% (wlv) sodium bicarbonate solution and one 20-mL portionofwater. Thecombined aqueous extracts are washed with three 25-mL portions of methylene chloride, and the methylene chloride washes added to the original methylene chloride solution. The methylene chloride solution is diluted to 250 mL with methylene chloride, and a 1-mLaliquot further diluted to 50 mL with methylene chloride. This solution contains the caffeine. The aqueous extract is acidified using sulfuric acid, final pH = 12, and extracted with 10 20-mL portions of methylene chloride. This methvlene ,~ chloride extract is diluted to 250 mL with methvlene chloridr, and n 2-ml. nliqu
