Optimization of Tea Sample Preparation Methods for ICP-MS and Application to Verification of Chinese Tea Authenticity

Abstract

In this study, 35 black, oolong, and green tea samples from China were analyzed by inductively coupled plasma mass spectrometry after a digestion method was developed on the basis of a response surface methodology. Linear discriminant analysis of whole data sets was performed in order to discriminate and classify Chinese tea samples according to their origin and type. The analysis revealed an excellent separation between tea samples according to their type and origin with a discrimination efficiency of 100%. The varieties of selected elements in Chinese tea were analyzed based on their origins and types. Keywords: tea, ICP-MS, minerals and trace elements, authenticity IntroductionTea (Camellia sinensis L) is a highly popular nonalcoholic beverage consumed by over two-thirds of the world's population owing to its medicinal and refreshing effects (Karak and Bhagat 2010). Since tea contains several essential nutrients and trace elements, drinking tea is considered beneficial for human health.The presence of heavy metals at trace levels in tea has received much attention because they are directly related to health.The efficacy of discriminating the geographical origin of teas is complicated by disparities in growing conditions such as soil and climate . The attributes of tea according to its geographical origin are also often recognized and appreciated by the consumers. Therefore, the discrimination of tea according to its geographical origin is presently the focus of attention (MoredaPiñeiro et al., 2003). However, it is not easy to determine its geographical origin by sensory evaluation. On the other hand, since elemental composition can provide accurate information about the provenance (Cubadda et al., 2006) of a tea sample, it is possible to identify the origin of tea on the basis of its elemental composition.In general, based on the different processing methods, teas are classified as: unfermented green tea (GT), fully fermented black tea (BT), and partially fermented oolong tea (OT), which are the most popular and frequently consumed teas in the world (Han et al., 2014). The processing method used affects the concentrations of elements in the processed tea. Therefore, the discrimination of tea types based on elemental fingerprinting is very urgent and important.Because of its low limit of detection (LOD) and multi-element measurement capability (Salomon et al., 2002), inductively coupled plasma mass spectrometry (ICP-MS) is used in a number of food analysis laboratories for determining elements at trace and ultratrace levels (Walczyk 2001). Therefore, ICP-MS is considered to be one of the most effective tools for determining the provenance of tea (Chudzinska et al., 2012;Herwig et al., 2011). This technique has been employed for the determination of trace metals in olive oil (Llorent-Martínez et al., 2011), honey (Chudzinska and Baralkiewicz 2011), tomato (Bressy et al., 2013, and particularly in tea. The number of studies on the application of this technique to tea has increased in recent years (Chudzinska ...

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Rapid classification of commercial teas according to their origin and type using elemental content with X-ray fluorescence (XRF) spectroscopy

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