Speciation analysis of manganese in tea samples using flame atomic absorption spectrometry after cloud point extraction

The speciation of Mn(II) in tea infusion was studied using cloud point extraction (CPE). In tea infusion, the flavonoid-bound Mn(II) was extracted at pH 5.0 using Triton X-100 (TX-100), the remaining free aquated Mn(II) and weakly-complexed Mn(II) in solution were both chelated with 8-hydroxyquinoline (HOx) and CPE-preconcentrated with TX-100. The enriched analyte was determined by flame AAS. The optimal concentrations for CPE of 0.02 ppm Mn were as follows: TX-100, 0.2% (v/v); HOx, 1.0 × 10⁻⁴ M; NaCl, 1.0% (w/v). LOD was 1.9 μg/L with a preconcentration factor of 10–20. The method was validated using a standard XAD-resin separation procedure and applied to synthetic seawater and CRM samples.     

黔产市售绿茶重金属的含量特征及健康风险评估

为研究黔产市售绿茶中重金属的含量分布特征及健康风险,以五个生产加工地的黔产市售绿茶为研究对象,分析其9种重金属(Pb、Cr、Cd、Hg、Cu、Zn、Mn、Ni和As)含量,利用美国环境保护署(USEPA)推荐的健康风险评价模型进行人体重金属的健康风险评价。结果表明,五种茶叶中Cr、Cd、Pb、Hg、Cu和As含量均低于国家限量标准。黔产市售绿茶的重金属浸出率大小次序为Zn>Mn>Hg>As>Cd>Pb>Cr>Cu>Ni。健康风险评价结果表明,五个产地的绿茶中重金属通过饮茶途径所产生的健康危害个人年风险大小次序为Cd>As>Mn>Ni>Cr>Hg>Pb>Zn>Cu,茶叶中重金属通过饮茶途径所产生的个人健康危害年风险总和为4.33×10-6~5.73×10-6 a-1,均低于USEPA和ICRP推荐的最大可接受风险水平,表明重金属引起的健康危害极小,其对暴露人群造成的健康危害可忽略不计,绿茶中重金属均处于安全范围内。     

Identification of elements in plant drugs and their water infusion using X-ray fluorescence analysis

The present work gives preliminary results of analysis of drug mixtures (NEPHROSAL tea bag) and its water infusion. In a sample of dried drugs the elements K, Ca, Mn, Fe, Ni, Cu, Zn, Br, Rb, Sr, Pb were identified, whereas in their water infusion only Ca, Mn, Zn and Sr were found. The method applied was radionuclide X-ray fluorescence analysis using a radionuclide source¹⁰⁹Cd, a Si/Li semiconductor detector and a multichannel analyzer Canberra 8100.     

Effects of different extraction methods and conditions on the phenolic composition of mate tea extracts

A simple and rapid HPLC method for determination of chlorogenic acid (5-O-caffeoylquinic acid) in mate tea extracts was developed and validated. The chromatography used isocratic elution with a mobile phase of aqueous 1.5% acetic acid-methanol (85:15, v/v). The flow rate was 0.8 mL/min and detection by UV at 325 nm. The method showed good selectivity, accuracy, repeatability and robustness, with detection limit of 0.26 mg/L and recovery of 97.76%. The developed method was applied for the determination of chlorogenic acid in mate tea extracts obtained by ethanol extraction and liquid carbon dioxide extraction with ethanol as co-solvent. Different ethanol concentrations were used (40, 50 and 60%, v/v) and liquid CO? extraction was performed at different pressures (50 and 100 bar) and constant temperature (27 ± 1 °C). Significant influence of extraction methods, conditions and solvent polarity on chlorogenic acid content, antioxidant activity and total phenolic and flavonoid content of mate tea extracts was established. The most efficient extraction solvent was liquid CO? with aqueous ethanol (40%) as co-solvent using an extraction pressure of 100 bar.     

Manganese Detection Using Stencil‐printed Carbon Ink Electrodes on Transparency Film

Mn concentrations were determined using square‐wave cathodic stripping voltammetry (CSV) with inexpensive, stencil‐printed carbon ink electrodes generated on polypropylene transparency films. Using an optimized pH 5 ammonium acetate buffer and addition of 1,4‐benzoquinone, a detection limit as low as 500 nM (30 ppb) was achieved. Addition of 1,4‐benzoquinone improved peak potential reproducibility and height, while addition of 3.5 % w/w sodium chloride to the background solution approximately doubled the sensitivity (μA/ppm). Tolerance tests with interfering metals were conducted and the method was found to be resilient to chromium(VI), iron(III), magnesium(II), nickel(II), and zinc(II), but susceptible to aluminum(III), copper(II), iron(II), and lead(II) at concentration ratios at or below one. This technique was successfully used to measure Mn levels in yerba mate and green tea samples as an example application.     

Antioxidant activity of polyphenols from green and toasted mate tea

The production and distribution of toasted mate tea in Brazil has increased, which has resulted in its greater consumption. Mate tea is obtained by roasting non-fermented erva-mate in order to produce toasted erva-mate or toasted mate tea. However, although the product is much appreciated, studies of its chemical composition and the concentration of polyphenols, particularly flavonols present in toasted mate tea, are few and often controversial. This paper elucidates some misunderstandings involving the nomenclature of erva-mate and toasted mate, and mainly provides an overview of the composition of polyphenols and antioxidant capacity of toasted mate tea and its raw material, erva-mate, in comparison with other teas, the compositions of which were found in the literature.     

Quality Assessment of Wild and Cultivated Green Tea from Different Regions of China

Natural products have always enjoyed great popularity among consumers. Wild tea is an interesting alternative to tea from intensive plantations. The term “wild tea” is applied to many different varieties of tea, the most desirable and valued of which are native or indigenous tea plants. Special pro-health properties of wild tea are attributed to the natural conditions in which it grows. However, there are no complex studies that describe quality and health indicators of wild tea. The aim of this research was to evaluate the quality of wild and cultivated green tea from different regions of China: Wuzhishan, Baisha, Kunlushan, and Pu’Er. The assessment was carried out by verifying the concentration of selected chemical components in tea and relating it to the health risks they may pose, as well as to the nutritional requirements of adults. Wild tea was characterized by higher micronutrient concentration. The analyzed teas can constitute a valuable source of Mn in the diet. A higher concentration of nitrates and oxalates in cultivated tea can be associated with fertilizer use. The analyzed cultivated tea was a better source of antioxidants with a higher concentration of caffeine. There were no indications of health risks for wild or cultivated teas.     

Comparison of heating extraction procedures for Al, Ca, Mg, and Mn in tea samples.

A focused-microwave-assisted procedure was adopted for the extraction of Al, Ca, Mg, and Mn in tea leaves. The efficiency of extraction was evaluated using diluted acids and a water-soluble alkaline tertiary-amines solution. The extraction procedure was implemented in 5 min. A conventional hot-plate digestion procedure was employed for a comparison. A colorless digest was obtained for all tea samples and the total contents determined for each analyte were employed for estimating the efficiency of extraction. Tea infusions were also prepared. Subsequent determinations of Al, Ca, Mg, and Mn were carried out using flame atomic absorption spectrophotometry (FAAS) and inductively coupled plasma optical emission spectrometry (ICP-OES). In most cases, quantitative, or at least semi-quantitative, extractions were attained for Ca, Mg, and Mn. Lower recoveries were attained to Al, which seems to be related to compounds that bind this element in the sample matrix. Large variations in the trace-element composition of teas were observed; these results are discussed with reference to both extraction media and type of tea.     

Analytical Assessment of Bioelements in Various Types of Black Teas from Different Geographical Origins in View of Chemometric Approach

A comprehensive approach to the mineral composition of black teas of different origins was studied using the Flame Atomic Absorption Spectrometry (FAAS) method, supported by chemometric tools including Principal Component Analysis PCA) and Classification and Regression Trees (CART). Significant differences between the teas from seven countries (Japan, Nepal, Kenya, Iran, Sri Lanka, India, and China) were shown. K was the main element determined in all teas, with an average concentration of 11,649 mg/kg, followed by Ca, Mg and Mn. In general, regarding all investigated black teas, the element content was ranked in the following order: K > Ca > Mg > Mn > Fe > Na > Zn > Cu. The applied chemometric methods allowed us to recognize black tea clusters based on their mineral composition and place of cultivation, and allowed us to find correlations between particular elements in black teas. The performed analyses revealed interesting correlations between the concentration of various elements in black teas: K was negatively correlated with Na, Fe, Mn and Cu; K was positively correlated with the content of Ca and Mg. Significant positive correlations between Mn and Fe and Mn and Zn in the studied black tea samples were also revealed. It was shown that mineral composition may be a significant factor regarding the origin of the black tea, not only considering the country, but also the region or province.     

Ultrasound-assisted solubilization of trace and minor metals from plant tissue using ethylenediaminetetraacetic acid in alkaline medium

A simplified and fast sample pretreatment method based on ultrasound-assisted solubilization of metals from plant tissue with ethylenediaminetetraacetic acid in alkaline medium is described. Powdered unknown and certified plant samples (particle size < 50 microns) were slurried in the solubilization medium and subjected to high intensity ultrasonication by a probe ultrasonic processor (20 kHz, 100 W). Metal solubilization can be accomplished within 3 min using a 30% vibrational amplitude and 0.1 M EDTA at pH 10, the supernatant obtained upon centrifugation being used for analysis. The method is applied to several food plants with unknown metal contents and certified plant samples such as CRM GBW07605 tea leaves, BCR CRM 61 aquatic moss and BCR CRM 482 lichen, with good trueness and precision. Intensive treatments with concentrated acids involving total matrix decomposition can be avoided. Metal determination (Ca, Cd, Mg, Mn, Pb and Zn) in the alkaline extracts was carried out by flame and electrothermal atomic absorption spectrometry.     

Ultrasound-assisted solubilization of trace and minor metals from plant tissue using ethylenediaminetetraacetic acid in alkaline medium

A simplified and fast sample pretreatment method based on ultrasound-assisted solubilization of metals from plant tissue with ethylenediaminetetraacetic acid in alkaline medium is described. Powdered unknown and certified plant samples (particle size < 50 μm) were slurried in the solubilization medium and subjected to high intensity ultrasonication by a probe ultrasonic processor (20 kHz, 100 W). Metal solubilization can be accomplished within 3 min using a 30% vibrational amplitude and 0.1 M EDTA at pH 10, the supernatant obtained upon centrifugation being used for analysis. The method is applied to several food plants with unknown metal contents and certified plant samples such as CRM GBW07605 tea leaves, BCR CRM 61 aquatic moss and BCR CRM 482 lichen, with good trueness and precision. Intensive treatments with concentrated acids involving total matrix decomposition can be avoided. Metal determination (Ca, Cd, Mg, Mn, Pb and Zn) in the alkaline extracts was carried out by flame and electrothermal atomic absorption spectrometry.     

超声搅拌悬浮液进样FAAS法测定茶叶中的微量元素

将超声搅拌悬浮液进样技术应用于火焰原子吸收光谱法,测定了茶叶中Fe、Mn、Zn、Ca、Mg的含量。结果表明,加标回收率97.1%~103.2%,RSD为2.1%~5.5%,该法快速、简单、准确。有利于人们了解茶叶中微量元素的含量,合理科学饮茶和开发茶叶保健饮品。     

Substoichiometric isotope dilution determination of manganese in biological smples using 2-thenoyltrifluoroacetone in isobutyl methyl ketone

A substoichiometric isotope dilution method was developed for the determination of microgram amounts of manganese. The method involves the use of carrier-free ⁵⁴Mn with Mn(II) carrier and its complexation with 2-thenoyltrifluoroacetone (TTA) at pH 8.5, the complex then being extracted into isobutyl methyl ketone. A minimum of 50 ng of manganese can be determined. The method was applied to the determination of manganese in several standard reference materials and biological samples such as tea leaves, spices and condiments. The method is simple and fast and yields results with high accuracy and precision.     

Speciation of Manganese in Tea Leaves and Tea Infusions

Abstract

A speciation scheme was developed for identification of the chemical forms of manganese in tea leaves and tea infusions. The range of manganese in five different groups of tea leaves was found to be 1107 – 2205 μg/g on a dry basis. It was noted that 30.0% of Mn was passed into the water that was present in the form of Mn(II), and also 2.5% of Mn was found as the total organic bound fraction and passed into the various solvents.     

Determination of Manganese (II) in Foodstuffs by β-Cyclodextrin Polymer Phase Spectrophotometry with 1-(2-Pyridylazo)-2-naphthol

The chromogenic agent, 1-(2-pyridylazo)-2-naphthol (PAN) was included in g -Cyclodextrin polymer ( g -CDP) and the modified polymer of inclusion of PAN ( g -CDP-PAN) was obtained. Based on the fact that g -CDP-PAN can adsorb Mn (II) in solution to form Mn (II)-PAN complex, a sensitive and selective solid phase spectrophotometric method for the determination of trace amounts of Mn (II) has been developed. The maximum absorbance of Mn (II)-PAN complex in g -CDP was at 514 nm. The working range of the calibration graph was 2-12 w g of Mn (II). The interference of molybdenum, lead, cobalt, chromium, iron, nickel, zinc, tin, cadmium, and copper that form colored species with PAN in the polymer phase was investigated. The method was applied to the determination of Mn (II) in black rice and tea samples. A new method for the determination of trace amounts of manganese by polymer phase spectrophotometry is described. Manganese reacted with 1-(2-pyridylazo)-2-naphthol (PAN) that was included in a g -cyclodextrin polymer. The absorbance of the colored polymer, packed into a 5 mm quartz cell, was determined directly at 514 nm. The proposed method was applied to the determination of manganese in black rice and tea samples.     

Study on essential and toxic elements intake from drinking of Chinese tea

Twenty different brands of Chinese tea were analyzed for multiple trace elements, including some essential and toxic elements, by neutron activation analysis (NAA). A comparison among tea brands from China, India, US and other countries was made for the ranges and averages of concentrations for Na, K, Mn, Cu, and Br. It has been observed that the trace element contents in tea leaves are largely dependent upon the soil and the environment where the tea grows. Chinese tea is rich in Mn and Cu comparing with those of other counties surveyed, but is indigent in Na. The transference ratio for each element determined (i.e., the fraction of an element in tea leave transferred into solution when tea is leached by percolation) is also reported. Adult daily intakes of some essential and toxic elements from tea drinking were also estimated.     

原子吸收光谱法测定冬枣叶茶中的8种金属元素

采用湿法对沾化冬枣叶茶样进行消化处理,利用火焰原子吸收光谱法测定了茶中K、Na、Ca、Mg、Fe、Mn、Cu、Zn的含量.结果表明,该法的加标回收率为95.2%～104.2%,RSD≤3.35%.该法操作简单,结果准确,为开发和利用冬枣叶茶提供了一定的科学依据.     

Validation and uncertainty analysis of a multiresidue method for 42 pesticides in made tea,tea infusion and spent leaves using ethyl acetate extraction and liquid chromatography–tandem mass spectrometry

A rapid, specific and sensitive multiresidue method to determine 42 pesticides in made tea, tea infusion and spent leaves has been developed and validated for the routine analysis by liquid chromatography–tandem mass spectrometry (LC–MS/MS). The method was reproducible (Horwitz ratio (HorRat) <0.5 at 50 ng/g) and validated by the analysis of sample spiked at 50 and 100 ng/g in made tea, tea infusion and spent leaves. The samples were extracted with ethyl acetate + cyclohexane (9:1; v/v), and the extracts were cleaned up by dispersive solid phase extraction with primary secondary amine sorbent + graphitized carbon black + Florisil. The recoveries of all the pesticides were between 70% and 120% with a relative standard deviation of less than 15% and correlation coefficient for each pesticide was R² ≥0.99. The matrix effect on signal of respective compounds was measured by comparing matrix-matched calibration standards with those in solvent-only. The limits of quantitation (LOQ) met the requirements of the maximum residue limits (MRLs) for pesticides in tea as recommended by the European Union.     

Analysis of Salvia officinalis plant extracts by capillary electrophoresis

Salvia officinalis (commonly called Sage) and similar plants contain many compounds of pharmaceutical interest and are used as a tea or in various pharmaceutical products. In this work, the use of CE for analysis of aqueous or ethanolic extracts from various Salvia plants has been studied. Especially, several buffers like borate, phosphate, acetate, etc., were examined under different concentrations, pH, separation voltage, injection time, and other parameters to find the optimal separation conditions. The optimization was also performed using experimental design and artificial neural networks. The optimal conditions were: separation voltage +20 kV, 40 mM buffer borate, pH 9.2, injection time 5 s, and UV detection at 280 nm. A new CE method has been developed, validated, and applied to analyze samples of S. officinalis from various countries.     

Effects of different steeping methods and storage on caffeine, catechins and gallic acid in bag tea infusions

Bag teas, packed 3g of ground black, green, oolong, paochoung and pu-erh tea leaves (the particle size used was 1-2mm), were steeped in 150 mL of 70, 85 or 100 degrees C hot water to study the effects of the number of steeping (the same bag tea was steeped repeatedly eight times, 30s each time, as done in China for making ceremonial tea) and varied steeping durations (0.5-4 min) on caffeine, catechins and gallic acid in tea infusions. The changes in tea infusions during storage at 4 or 25 degrees C for 0-48 h and the variations in these compounds of bag tea infused with 150 mL of 4 or 25 degrees C cold water for 0.5-16 h were also investigated. A HPLC method with a C18 column and a step gradient solvent system consisting of acetonitrile and 0.9% acetic acid in deionized water was used for analysis. Results for all kinds of tea samples showed that the second tea infusion contained the highest contents of caffeine, catechins and gallic acid when bag teas were steeped in 70 degrees C water. It was different from that steeped at 85 and 100 degrees C, the highest contents existed in the first infusion. These compounds decreased gradually in later infusions. Higher amounts of caffeine, catechins and gallic acid could be released from bag teas as hotter water was used. As steeping duration prolonged, these ingredients increased progressively, however, their levels were lower than that cumulated from the infusions with the identical bag tea prepared recurrently at the same temperature and time points. (-)-Gallocatechin gallate and (+)-catechin existed in these tea infusions rarely and could not be detected until a certain amount of them infusing. Except gallic acid that showed a significant increase and caffeine that exhibited no significant change, all kinds of catechins decreased appreciably after tea infusions were stored at 25 degrees C for 36 h; nevertheless, all of them showed no evident changes at 4 degrees C storage. The caffeine, catechins and gallic acid in tea infused with cold water also increased with increasing duration. Their contents in 25 degrees C steeped tea were higher than that made at 4 degrees C; moreover, their infusion rates from bag teas to cold water were markedly lower than that steeped in hot water. Infusing efficiencies of non-gallated catechins were higher than gallated catechins under cold water steeping.