Quality control of commercial tea by x‐ray fluorescence

Salvador, Marcos José; Lopes, Guido N.; Filho, V. F. Nascimento; Zucchi, Orghêda Luíza Araújo Domingues

doi:10.1002/xrs.546

Cited by 39 publications

(18 citation statements)

References 11 publications

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“…Analysis of variance of the data showed no statistically significant differences in mean Cr content among the different kinds of tea (p > 0.05). Salvador et al (24) determined Cr presence in black tea, although levels were not detectable. However, Onianwa et al (25) reported values of Cr The mean Mn contents in green, black, and oolong teas were 541.6, 285.9, and 354.0 µg/g, respectively.…”

Section: Resultsmentioning

confidence: 99%

Determination of Tea Components with Antioxidant Activity

Cabrera

Giménez

López

2003

J. Agric. Food Chem.

390

237

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Levels of essential elements with antioxidant activity, as well as catechins, gallic acid, and caffeine levels, in a total of 45 samples of different teas commercialized in Spain have been evaluated. Chromium, manganese, selenium, and zinc were determined in the samples mineralized with HNO 3 and V 2 O 5 , using ETAAS as the analytical technique. The reliability of the procedure was checked by analysis of a certified reference material. Large variations in the trace element composition of teas were observed. The levels ranged from 50.6 to 371.4 ng/g for Cr, from 76.1 to 987.6 µg/g for Mn, from 48.5 to 114.6 ng/g for Se, and from 56.3 to 78.6 ng/g for Zn. The four major catechins [(-)-epigallocatechin gallate (EGCG), (-)-epigallocatechin (EGC), (-)-epicatechin gallate (ECG), and (-)-epicatechin (EC)], gallic acid (GA), and caffeine were simultaneously determined by a simple and fast HPLC method using a photodiode array detector. In all analyzed samples, EGCG ranged from 1.4 to 103.5 mg/g, EGC from 3.9 to 45.3 mg/g, ECG from 0.2 to 45.6 mg/g, and EC ranged from 0.6 to 21.2 mg/g. These results indicated that green tea has a higher content of catechins than both oolong and fermented teas (red and black teas); the fermentation process during tea manufacturing reduces the levels of catechins significantly. Gallic acid content ranged from 0.039 to 6.7 mg/g; the fermentation process also elevated remarkably gallic acid levels in black teas (mean level of 3.9 ( 1.5 mg/g). The amount of caffeine in the analyzed samples ranged from 7.5 to 86.6 mg/g, and the lower values were detected in green and oolong teas. This study will be useful for the appraisal of trace elements and antioxidant components in various teas, and it will also be of interest for people who like drinking this beverage.KEYWORDS: Tea; trace elements; catechins; gallic acid; antioxidants; caffeine INTRODUCTIONTea, a leaf extract of the plant Camellia sinensis, is the second most consumed beverage in the world, with an estimated 18-20 billion cups consumed daily and, for instance, an estimated average consumption of 1 L/person/day in the United Kingdom (1). Depending on the manufacturing process, teas are classified into three major types: nonfermented green tea (produced by drying and steaming the fresh leaves and thus, no fermentation, i.e., oxidation, occurs); semifermented oolong tea (produced when the fresh leaves are subjected to a partial fermentation stage before drying); and fermented black and red (pu-erh) teas (which undergo a full fermentation stage before drying and steaming, although the fermentation of black tea is oxidation and that of pu-erh tea is attained using microorganisms) (2).Originating from China, tea has gained the world's taste in the past 2000 years. Initially, it was consumed only by Chinese monks, but its use spread to other regions, such as Great Britain, which allowed its effective diffusion to Western countries. Nowadays, consumption of tea is part of people's daily routine, as an everyday drink and as a therapeutic aid in m...

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Section: Resultsmentioning

confidence: 99%

Determination of Tea Components with Antioxidant Activity

Cabrera

Giménez

López

2003

J. Agric. Food Chem.

390

237

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“…In this respect, several groups have proposed different conditions to obtain clean herbal water extracts. 23,24,27,28 In traditional medicine and as a common drinking beverage in many Eastern and Oriental countries, the preparation of herbal drinks for oral intake involves cooking the plants with water for 30-90 min. In modern herbal medicine, the herbs are cooked with water or ethanol and then processed into tablets, pills or liquids.…”

Section: Infusion Preparationmentioning

confidence: 99%

Quantitative determination of essential and trace element content of medicinal plants and their infusions by XRF and ICP techniques

et al. 2005

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Macro-and microelement contents of five medicinal plants (Taraxacum officinale Weber, Eucalyptus globulus Labill, Plantago lanceolata L., Matricaria chamomilla L. and Mentha piperita L.) and their infusions were evaluated by the combined use of x-ray fluorescence (WDXRF and EDXRF, bulk raw plants) and inductively coupled plasma (ICP-MS and ICP-AES, infusions) techniques. The analytical methods allow the determination of 17 elements (Na, Mg, Al, Si, P, S, K, Ca, Ti, Mn, Fe, Cu, Zn, As, Rb, Sr, and Pb) both in plants and in the infusions. The use of XRF techniques offer a good multielemental approach for the rapid quality control of bulk raw plant materials whereas ICP techniques are well suited for the analytical control of infusions in order to ascertain the nutritional role of medicinal plants and the daily dietary intake.

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“…Generally, the determination of total concentrations of various macro-and micro-elements in different teas as well as medicinal plants is carried out with the use of flame atomic absorption spectrometry (FAAS) (Aksuner et al 2012;Colak et al 2005;Kumar et al 2005;Li et al 2006;Malik et al 2008;Narin et al 2004a,b;Seenivasan et al 2008;Soylak et al 2007), graphite furnace atomic absorption spectrometry (GF AAS) (Dash et al 2008;Seenivasan et al 2008), inductively coupled plasma optical emission spectrometry (ICP OES) (Chen et al 2009;Dash et al 2008;Kara 2009;Malik et al 2008;Matsuura et al 2001;McKenzie et al 2010;Mierzwa et al 1998;Özcan et al 2008), inductively coupled plasma mass spectrometry (ICP MS) (Kara 2009;Matsuura et al 2001;Nookabkaew et al 2006;Shen and Chen 2008) and X-ray fluorescence spectrometry (XRFS) (Salvador et al 2002;Xie et al 1998). As a rule, the decomposition of the matrix of tea samples is an indispensable and mandatory step before their elemental analysis by the majority of these spectrometric methods.…”

Section: Introductionmentioning

confidence: 99%

Simple and Fast Sample Preparation Procedure Prior to Multi-element Analysis of Slim Teas by ICP OES

2014

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The knowledge about mineral content of slim teas is of great importance since the consumption of these beverages has rapidly increased for the past several years. An increasing popularity of these tea products is mainly attributed to their nutritional properties, flavor, taste and health effects. Therefore, the main goal of the present work was to develop a precise and accurate method of the multi-element analysis of slim teas by inductively coupled plasma optical emission spectrometry (ICP OES) without the need for a laborious and tedious sample treatment preceding spectrometric measurements. Five sample preparation procedures, i.e., the total decomposition in a mixture of HNO 3 and H 2 O 2 solutions using closed vessel microwave-assisted or open vessel hot-plate systems, the solubilisation in aqua regia or a tetramethyl ammonium hydroxide solution and the extraction in a diluted HNO 3 solution, were compared. The performance of the compared procedures was determined in terms of the precision and the accuracy of results achieved and limits of detection of elements. It was found that the solubilisation in aqua regia gave the best results, i.e., limits of detection between 0.15 and 98.4 ng l −1 , the precision within 0.6−3.0 % and the accuracy better than 5 %. The developed method of the analysis, being a useful alternative to timeconsuming wet digestion procedures, was successfully applied to the analysis of five slim tea products.

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Quality control of commercial tea by x‐ray fluorescence

Cited by 39 publications

References 11 publications

Determination of Tea Components with Antioxidant Activity

Determination of Tea Components with Antioxidant Activity

Quantitative determination of essential and trace element content of medicinal plants and their infusions by XRF and ICP techniques

Simple and Fast Sample Preparation Procedure Prior to Multi-element Analysis of Slim Teas by ICP OES

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