Application of High Resolution-Continuum Source Flame Atomic Absorption Spectrometry (HR-CS FAAS): Determination of trace elements in tea and tisanes

Comparison and Validation of Different Alternative Sample Preparation Procedures of Tea Infusions Prior to Their Multi-Element Analysis by FAAS and ICP OES

“…Except for Cr, Mg, and Na, it was found that mean concentrations of studied metals in infusions of BTs were lower by about 10-20 % (Fe, K, Zn), 20-40 % (Al, Ba, Cu, Sr), or even more, i.e., 80 and 120 % in case of Mn and Ca, respectively, than mean concentrations of these metals evaluated for GTs. This was likely attributed to a stronger binding of metal ions by constituents of the matrix of BTs than this of GTs (Paz-Rodriguez et al 2015). Mean concentrations of Cr, Mg, and Na in infusions of BTs were higher by about 10-20 % than those found in infusions of GTs.…”

“…To visualize the data into 2 or 3 dimensions (Diniz et al 2015;Froes et al 2014;Paz-Rodriguez et al 2015), the principle component analysis (PCA) was applied to a data matrix that comprised all analyzed teas (objects) and concentrations of 13 metals (variables) determined in infusions of these teas, i.e., Al, Ba, Ca, Cr, Cu, Fe, K, Mg, Mn, Na, Ni, Sr, and Zn (with the exception of Cd, Co, and Pb that concentrations were <QLs). Missing values in 2 cases for Cr were replaced with a respective QL value (Paz-Rodriguez et al 2015).…”

“…The most popular and extensively used in the analysis of tea infusions are spectrochemical methods, including flame atomic absorption spectrometry (FAAS) (Dambiec et al 2013;Gallaher et al 2006;Malik et al 2008;Memic et al 2014;Paz-Rodriguez et al 2015;Polechonska et al 2015;Tahir Soomro et al 2008) and inductively coupled plasma optical emission spectrometry (ICP OES) (Altintig et al 2014;Dash et al 2008;Diniz et al 2015;Derun 2014;Fernandez et al 2002;Froes et al 2014;Malik et al 2008;Mehra and Baker 2007;Ozcan et al 2008;Ozdemir et al 2014;Salahinejad and Aflaki 2010;Street et al 2006). In case of FAAS, it is particularly convenient in reference to selected metals that are highly abounded in tea infusions, i.e., Ca, Fe, K, Mg, Mn, and Na (Szymczycha-Madeja et al 2012).…”

“…Among different sample preparation procedures reported so far for infusions of black (BTs) and green (GTs) teas before their spectrochemical analysis, it appears that no treatment and direct measurements of metals in them was preferred in case of FAAS (Dambiec et al 2013;Malik et al 2008;Memic et al 2014;Polechonska et al 2015), ICP OES (Altintig et al 2014;Derun 2014;Diniz et al 2015;Froes et al 2014;Malik et al 2008;Mehra and Baker 2007;Ozcan et al 2008;Ozdemir et al 2014;Street et al 2006, andGFAAS (Jeszka-Skowron et al 2015). In addition, infusions of teas were acidified with HNO 3 to a concentration of 0.28 mol L −1 (Salahinejad and Aflaki 2010) or 1.4 mol L −1 (Schwalfenberg et al 2013) or HCl to a concentration of 0.12 mol L −1 (Paz-Rodriguez et al 2015). Otherwise, infusions were evaporated to near dryness while sample residues left were digested with concentrated solutions of HNO 3 and HClO 4 (Tahir Soomro et al 2008) or HCl (Gallaher et al 2006).…”

“…Although spike-and-recovery experiments were made in case of few direct analyses of infusions and quantitative recoveries were obtained, i.e., 91.9-113 % for infusions of GTs (Froes et al 2014) and 85.2-113 % for infusions of BTs and GTs (Diniz et al 2015), it should be noted that the recovery study is selectively used and does not have a high priority when another analytical method is available for comparison purposes. Paz-Rodriguez et al (2015) compared concentrations of Ca, Co, Cu, Fe, Mn, Ni, Na, and Zn determined by FAAS in infusions of BTs and GTs acidified with HCl when using the standard addition method and simple standards for the calibration. By indicating the lack of systematic errors, they additionally checked that recoveries of added metals were also quantitative, i.e., 90.3-108 and 88.0-110 %, respectively, for infusions of BTs and GTs samples.…”