title: Determination and confirmation of isopropyl p-toluenesulfonate in cosmetics by HPLC-diode array detector method and GC-MS.
abstract: OBJECTIVE
  Isopropyl p-toluenesulfonate (IPTS) is a potentially genotoxic by-product formed during the esterification of palm oil-based palmitic and palm kernel oil-based myristic acid with isopropanol to produce isopropyl palmitate or isopropyl myristate. There are no methods described for the analysis of IPTS in cosmetic products. In this work, we have established a simple, precise and accurate method to determine the presence and level of IPTS in various finished cosmetic products which contain palm-based esters in their formulations.
  
  
  METHODS
  An Agilent 1200 series high-performance liquid chromatography (HPLC) unit using a diode-array detector (DAD) has been employed and optimized to detect IPTS in cosmetic products. For the separation, a reverse-phase Hypersil Gold C8 column (5 μm, 4.6 mm i.d. 250 mm) 5 mM tetrabutylammonium phosphate buffer 50 : 50, (v/v) solution in acetonitrile as mobile phase, in isocratic mode and a flow rate of 0.8 mL min-1were used. A second method using a gas chromatography/mass selective detector GC-MSD was also developed to confirm the IPTS identity in the cosmetic products.
  
  
  RESULTS
  Recoveries of IPTS from cosmetic matrices such as a lotion, cleansing milk and a cream ranged from 94.0% to 101.1% with <5% relative standard deviation (%RSD) showing good accuracy and repeatability of the method. The six-point calibration curves (determined over the range 0.5-50 μg mL-1) have a correlation coefficient of 0.9999 (based on HPLC peak area) and 0.9998 (based on HPLC peak height). The intra- and interday precisions (measured by the %RSD) of the method were <2% and <5%, respectively, indicating that the developed method is reliable, precise and reproducible. The detection and quantification limit of the method were found to be 0.5 μg mL-1and 1.6 μg mL-1, respectively. Analyses of 83 commercial cosmetics showed no presence of IPTS.
  
  
  CONCLUSIONS
  The validation data indicated that this method was suitable for the quantitative analysis of IPTS in commercial cosmetics. This method is applicable for analyses of trace levels of IPTS in cosmetics and has the advantage of using only simple sample preparation steps.
authors.affiliation: Malaysian Palm Oil Board, No. 6 Persiaran Institusi, Bandar Baru Bangi, Kajang Selangor, 43000, Malaysia.
authors.forename: B Y P
authors.initials: BY
authors.lastname: Tay
authors.affiliation: Faculty of Science and Technology, The National University of Malaysia, (UKM), Bangi Selangor, 43600, Malaysia.
authors.forename: S C
authors.initials: SC
authors.lastname: Yung
authors.affiliation: Faculty of Science, University of Malaya, Kuala Lumpur, 50603, Malaysia.
authors.forename: T Y
authors.initials: TY
authors.lastname: Teoh
mesh_terms: D001557:Benzenesulfonates / Q000737:chemistry*; D002851:Chromatography, High Pressure Liquid / Q000379:methods*; D003358:Cosmetics; D008401:Gas Chromatography-Mass Spectrometry / Q000379:methods*; D012015:Reference Standards
chemical_list: D001557:Benzenesulfonates; D003358:Cosmetics; C029501:4-toluenesulfonic acid
keywords: 
  HPLC
  ; GC-mass spectroscopy; Isopropyl p-toluenesulfonate; chemical analysis; cosmetics; isopropyl esters; safety testing