I. Soc. Cosmet. Chem., 26, 377-387 (August 1975) Quantitative Analysis of Methyl and Propylparaben by High Performance Liquid Chromatography F. A. FITZPATRICK *A. F. SUMMA, and A.D. COOPERT Synopsis-A HIGH PERFORMANCE LIQUID CHROMATOGRAPHIC method for the quantit•tive analysis of METHYLPARABEN and PROPYLPARABEN in EMULSION and SUSPENSION systems is described. Low cost, laboratory assembled instrumentation not requiring excessive pressure capabilities (less than 500 psig) is used for the analysis. The method, which is simple, rapid, and precise, involves breaking of the emulsion, ad- dition of an internal standard solution, and filtration, followed by chromatographic an- alysis on a permanently BONDED REVERSED PHASE liquid chromatographic column. For suspensions, the sample is mixed vigorously with the internal standard and alcohol before filtration and chromatography. Total time for sample preparation and analysis is less than 30 min. INTRODUCTION Authors of several recent papers have indicated the potential of high per- formance liquid chromatography (HPLC) in the area of drug and cosmetic analysis (1-5). Steroids, alkaloids, antibiotics, preservatives, and vitmnins, which are often difficult to separate and analyze by other methods, have been determined successfully by HPLC. HPLC affords simple preparation of many samples, avoiding extensive extractions usually necessary for ultraviolet (uv) or colorimetric assays. It avoids problems associated with thermal instability in gas chromatography and the occasional need for preparing volatile deriva- tives prior to analysis and it overcomes the time factor and manipulative problems of quantitative thin-layer chromatography (tlc). It also provides the resolution necessary to separate compounds of interest from interfering sub- *Present address: Drug Metabolism Unit, Upjohn Cmnpany, Kalamazoo, Mich. 49001. '•Vick Divisions Research and Development Richardson-Merrell Inc., Mount Vernon, N.Y. 10553. 377

378 JOURNAL OF THE SOCIETY OF COSMETIC CHEMISTS stances commonly found in the complex matrices of many foods, drugs, and cosmetics and quantitation can be performed analogously to gas chromato- graphic methods. Despite its increasing use, relatively few papers have been reported concerning routine quantitative analysis for ingredients in cosmetics. This paper describes a simple and reliable HPLC method using a reversed phase-packing material for quantitating individual parabens in cosmetic emulsions or suspensions with a liquid chromatographic apparatus construc- ed from available components. Several significant advantages accompany this approach. Primary among these is the low cost and reliability of the instru- mentation involved. Most articles published on quantitative HPLC techniques have employed expensive instruments and high pressures (greater than 1000 psig) to achieve adequate separations. Our experience has shown that many analyses can be performed at reasonable pressures (500 psig or less) with low cost components available from various suppliers and assembled in the lab- oratory. The expense involved in purchasing and operating most commercial instruments precludes their exclusive use for a particular quantitative analy- sis. For paraben analyses specifically, a reversed phase chromatographic sys- tem eliminates potential losses due to reduced solubility of the higher paraben homologs in the aequeous ion exchange system described by Nelson (6). Ease of sample handling and analysis time (less than 30 min per ample) compare favorably with other methods commonly in use (7), and the technique de- scribed is applicable to a wide variety of formulations containing parabens. EXPERIMENTAL Apparatus An HPL chromatograph shown in Fig. 1 was assembled as follows. The sol- vent delivery system was a Milton Roy Minipump,©* Model 196-31, capable of operation at pressures up to 1000 psig. Connected in sequential order froin the pump outlet were a Chromatronix©* pressure relief valve, a 1000 psig pressure gauge, and a 6 ft x 0.03 in. inside diameter (i.d.) length of Teflon© tub- ing, whose function was to minimize pulsations caused by the reciprocating delivery of solvent from the pump. A subsequent modification has re- placed the tnbing with a bellows-type pluse dampers to improve baseline stability. A 30 x 0.2-cm i.d. glass column packed with Vydac©0 reversed phase *Milton Roy Company, 5000 Park St. N., St. Petersburg, Fla. 33733. *Chromatronix, Division of Spectra Physics, 2905 Stender Way, Santa Clara, Calif. 95050. -*Laboratory Data Control, P.O. Box 10235, Interstate Industrial Park, Riv- iera Beach, Fla. 33404. 0Separations Group, 8738 Oakwood Street, Hesperia, Calif. 92345.