Simplified tea classification based on a reduced chemical composition profile via successive projections algorithm linear discriminant analysis (SPA-LDA)

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

“…Surprisingly, there are many contributions in the literature, in which the direct analysis of infusions of BTs and GTs was used (Altintig et al 2014;Dambiec et al 2013;Derun 2014;Diniz et al 2015;Froes et al 2014;Jeszka-Skowron et al 2015;Malik et al 2008;Mehra and Baker 2007;Memic et al 2014;Ozcan et al 2008;Ozdemir et al 2014;Street et al 2006). Unfortunately, in the overwhelming majority of cited papers (with exception for Diniz et al 2015;Froes et al 2014), no validation of sample preparation procedures used and results achieved was undertaken. Even when the accuracy of results was checked by the spiking experiment and recoveries obtained were quantitative (Diniz et al 2015;Froes et al 2014), this could not be a sufficient condition for obtaining accurate results.…”

“…Black and oolong teas are typically produced from older leaves, while green tea is made from the flush containing only young leaves (Szymczycha-Madeja et al 2012). When steeping tea leaves or brewing tea bags, different bioactive compounds are extracted into infusions making these beverages a valuable source of antioxidants and phytochemicals (Diniz et al 2015;Jeszka-Skowron et al 2015). Except for organic bioactive substances, infusions of black and green teas also contain various elements that are leached from tea leaves and enhance their pro-health activity (Jeszka-Skowron 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).…”

“…In addition, graphite furnace atomic absorption spectrometry (GFAAS) (JeszkaSkowron et al 2015;Wrobel et al 2000) and inductively coupled plasma mass spectrometry (ICP MS) (Milani et al 2015;Schwalfenberg et al 2013;Shen and Chen 2008;Sofuoglu and Kavcar 2008) were used. 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).…”

“…Unfortunately, reported methods of the direct analysis of infusions of BTs and GTs (Altintig et al 2014;Dambiec et al 2013;Derun 2014;Jeszka-Skowron et al 2015;Malik et al 2008;Mehra and Baker 2007;Memic et al 2014;Ozcan et al 2008;Ozdemir et al 2014;Street et al 2006), or their acidification (Salahinejad and Aflaki 2010;Schwalfenberg et al 2013) were not validated nor verified, therefore, the quality of the data achieved in above-cited works could be questioned. 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.…”