Rapid and easy ICP OES determination of selected major, minor and trace elements in Pu-erh tea infusions using the response surface methodology along with the joint desirability function approach

Abstract

A new analytical method was proposed for multielement (Al, Ba, Ca, Cu, Fe, K, Mg, Mn, Na, Sr and Zn) analysis of Pu-erh teas infusions by inductively coupled plasma optical emission spectrometry. The Box-Behnken response surface design together with individual desirability functions and the joint desirability function approach was applied to develop experimental conditions of this new procedure, being alternative to high-temperature wet digestion. The procedure involved the samples to be just 5-fold diluted with 1.7 mol L−1 HNO3. The proposed method was precise (relative standard deviations within 2–8%), true (relative errors from −8 to +6%) and guaranteed very good detectability (detection limits within 1–6 ng g−1, except for Ca and Fe). It was used for analysis of infusions of Pu-erh teas as well as to verify the effect of their preparation conditions (steeping water temperature, steeping time).