The Application of Salting-Out in the Analysis of Methoxy-Phenolic Compounds in Pu-erh Tea

This paper presents the application of salting-out in the analysis of methoxy-phenolic compounds in pu-erh tea by using headspace solid microextraction (HS-SPME) combined with gas chromatography mass spectrometry (GC/MS). At first, the influences of extraction and the best extraction condition were investigated, include SPME fibers, extraction time and extraction temperature. Under the optimum condition, the salting-out performances of NH4Cl, KCl, NaCl, MgCl2, Na2SO4, (NH4)(2)SO4 and C6H5O7Na3 were studied. Sodium citrate exhibits the highest extraction efficiency. Compared with unsalted, the total peak area of methoxy-phenolic compounds increased by 2.8 times with sodium citrate added. With C6H5O7Na3, the proposed method affords wide of linearity, good linear regression coefficients (0.992-0.999), detection limits varied from 1.54 to 14.53 ng/g and the relative standard deviations for repeatability were below 10 %. Recovery was ranged from 82.05 to 112.04 % and the relative standard deviations were below 10 %.