LC-MS/MS signal enhancement for estrogenic hormones in water samples using experimental designElectronic supplementary information (ESI) available. See DOI: 10.1039/c6ra06526k

• Main Authors: Karapinar, Ilgi, Erta, F. Nil, ahintürk, Binnaz, Aftafa, Can, Kiliç, Ela
• Format: Journal Article
• Published: 20.04.2016
• ISSN: 2046-2069
• DOI: 10.1039/c6ra06526k

This paper describes optimization of LC-MS/MS conditions to develop a method for selective and sensitive determination of estrogens, namely: estradiol (E2), estrone (E1), estriol (E3), and synthetic estrogen as ethinyl estradiol (EE2) by using statistical experimental design methods. The optimization studies were conducted in three stages: (i) determination of minimum alkaline volume ratio (0-17% NH 4 OH at 0.2 M) in mobile phase to maximize peak area by single factor experimental design; (ii) optimization of LC elution conditions including flow rate, acetonitrile concentration in standard and in mobile phase by Box-Behnken response surface method (RSM), and (iii) optimization of LC-MS/MS conditions for seven factors to maximize peak areas by Box-Behnken RSM. NH 4 OH volume ratio significantly affected the peak area and it was maximized at 3-5% volume ratio. Predicted optimal LC elution conditions were % ACN standard : 28, % ACN mobile :44 and flow rate of 137 μL min −1 . The optimum instrumental conditions were determined as sheath gas pressure:33 arbitrary unit (Arb), ion sweep gas pressure: 0.4 Arb, aux gas pressure: 17 Arb, capillary temperature: 254 °C, vaporizer temperature: 352 °C, collision gas pressure: 1.9 mTorr, and spray voltage: 2740 V. Optimization provided substantial improvements in peak symmetry and resolution factor and a 20-25 times peak signal gain with respect to the instrumental self-optimized condition at detection limits of ng L −1 levels were achieved. The lower detection limits were obtained by coupling the method with a SPE procedure for attaining high pre-concentration factors. The signal enhancement was about three orders of magnitude, which constitutes a remarkable sensitivity of the method. Present paper describes the optimization of LC-MS/MS conditions by using experimental design for selective and sensitive determination of estrogenic hormones namely estradiol (E2), estrone (E1), estriol (E3) and ethinyl estradiol (EE2).