Elemental analysis of teas, herbs and their infusions by means of total reflection X-ray fluorescence

X-ray fluorescence spectrometry for environmental analysis: Basic principles, instrumentation, applications and recent trends

In recent years, the conceptual advancement on green analytical chemistry (GAC) has moved in parallel with efforts to incorporate new screening or quantitative low-cost analytical tools to solve analytical problems. In this sense, the role of solid state techniques that allow the non-invasive analysis (or with a minimum sample treatment) of solid samples cannot be neglected. This review describes the basic principles, instrumentation and advances in the application of X-ray fluorescence instrumentation to the environmental sciences research topics, published between 2006 and 2020. Obviously, and because of the enormous number of works that can be found in the literature, it is not possible to exhaustively cover all published articles and the diversity of topics related to the environment in which a solid state technique like XRF has been applied successfully. It is a question of making a compilation of the instrumentation in use, the significant advances in XRF spectrometry and sample treatment strategies to highlight the potential of its implementation for environmental assessment.

Multi-elemental Analysis and Health Risk Assessment of Commercial Yerba Mate from Brazil

Consumption of yerba mate occurs mostly in the form of hot infusion (chimarrão). Water solubility of elements found in commercialized yerba mate is needed to establish nutritional value and risks associated with potentially toxic elements. In this study, yerba mate products marketed in three Brazilian states (Paraná, Santa Catarina, and Rio Grande do Sul) for chimarrão were analyzed. Total (dry product) and hot water-soluble concentrations of Al, As, B, Ba, Ca, Cd, Co, Cs, Cu, Fe, K, Li, Mg, Mn, Mo, Ni, P, Pb, Rb, S, Se, Sr, Ti, V, and Zn were determined by inductively coupled plasma mass spectroscopy (ICP-MS). Total concentrations of the ten top elements followed the order of K>Ca>Mg>Mn>P>S>Al>Fe>Ba>Zn. The most soluble elements were B, Cs, Ni, Rb, and K, with values greater than 80%. The lowest water-soluble elements were V, Fe, and Ti (values <10%), followed by Ba, Cd, Al, As, Sr, Ca, and Pb with solubility between 10 and 20%. Although total Cd levels in yerba mate products were often above those permitted by South America legislation, estimated daily consumption intake indicated no risk associated with the chimarrão beverage. Manganese was the micronutrient with the highest total and soluble levels in yerba mate, which surpassed recommended daily intake values when considering a consumption amount of 50 g day^-1 of yerba mate as chimarrão. The consumption of yerba mate is safe and contributes to intake of nutrients. The Cd and Pb reference values of yerba mate products sold in South America should be revised.

Evaluation of Na and K in anti-diabetic ayurvedic medicine using LIBS

Diabetes mellitus, known as diabetes, is a challenging issue, and to control diabetes, a large population is lining toward ayurvedic medicine. In the present study, four brands of anti-diabetic ayurvedic medicines, along with a home remedy, are analyzed using the laser-induced breakdown spectroscopic (LIBS) technique. The study is carried out to know the elements responsible for glycemic potential. The laser-induced breakdown (LIB) spectra elucidate the presence of organic and inorganic elements like Al, Ba, C, Ca, Cu, Fe, H, K, Mg, N, Na, O, Si, Sr, Zn, and the molecular band of CN molecule in medicines. LIBS result also reveals Na and K's distinct concentration, which plays a vital role in diabetes management. The presence of the CN band and organic elements indicate the presence of organic molecular compositions in medicines. For confirmation of organic composition in the drugs, Fourier transform infrared spectroscopy (FT-IR) has been performed. Principal component analysis (PCA) on the LIBS data of the medicines has been used for instant discrimination based on their elemental/molecular compositions.

Herbs and herbal infusions: Determination of natural contaminants (mycotoxins and trace elements) and evaluation of their exposure

Herbal infusions are amongst the world's most popular and widely enjoyed beverages, due to both large variety and convenience. However, natural contaminants, such as mycotoxins and trace elements can accumulate in aromatic herbs, which may have serious food safety and public health implications. In this study, the presence of mycotoxins, as well as the content of trace elements was evaluated in herbs and herbal infusions commercialized in Brazil. For the determination of fourteen mycotoxins, including the emerging mycotoxins enniatins (EN), beauvericin (BEA), and sterigmatocystin (STE), a liquid-chromatography tandem mass spectrometry (LC-MS/MS) method was validated. Overall, 42 out of 58 herb samples (72%) were contaminated, being BEA the most usual mycotoxin, present in 43% of the samples, followed by STE and HT-2 toxin, present in 37% and 24% of the samples, respectively. In herbal infusions, the occurrence of mycotoxins was 88% lesser than those verified in raw products. Despite these low levels, the hazard quotient (HQ) calculated revealed a potential health concern for HT-2 in infusions. The margin of exposure values for aflatoxins (AF), and ochratoxin A (OTA) from six herbal infusions were below 10,000, indicating also potential health risks. The twenty-one trace elements comprising toxic elements such as arsenic (As), cadmium (Cd), and lead (Pb) were determined in herb raw materials by inductively coupled plasma-mass spectrometry (ICP-MS). The levels of trace elements in herbs were very varied, with aluminum (Al) presenting the highest amount. The levels of legislated elements (As, Cd, Pb) analyzed in herbs were lower than 3.03 µg g^-1 (Pb), thus not exceeding the legal limits defined for herbal medicinal by both European and Brazilian pharmacopeia.

Features of sample preparation techniques in the total-reflection X-ray fluorescence analysis of tea leaves

Tea is a popular drink around the world and contains essential minerals and trace elements for human health. In this study, the analytical capabilities of the total-reflection X-ray fluorescence method (TXRF) were considered for the analysis of tea. Different sample preparation techniques, e.g. suspension, open vessel acid digestion, and microwave acid digestion were examined. The influence of particle size was investigated in the analysis of the suspension of tea samples. Mass-absorption coefficients for the tea matrix and the critical surface density of the specimen were calculated. The data obtained explain the presence of absorption effects in the determination of P, S, Cl, and K in suspensions. The digestion procedure is chosen as an optimal sample preparation technique for the TXRF analysis of tea. Nineteen real tea samples were analyzed using TXRF. The advantages of TXRF have been presented through the comparison of results with the wavelength-dispersive X-ray fluorescence spectrometry method.

Total reflection X-ray fluorescence analysis of elemental composition of herbal infusions and teas

BACKGROUND

The elemental composition of herbal infusions and teas has not been sufficiently investigated. It could potentially be used for defining fingerprints for individual herbal / tea infusions, differentiation of botanical families, detecting the influence of packaging, and other purposes. The objective of this study was to determine the elemental composition, including the trace element content, of various herbal infusions and teas by means of total reflection X-ray fluorescence analysis (TXRF), with a chemometrics approach using principal component analysis (PCA).

RESULTS

This study determined the elemental composition of various herbal infusions and teas, including trace elements, using total reflection X-ray fluorescence (TXRF). The methodology for the sample preparation was established, including the multiple-steepings procedure for the two tea samples (Oolong and Pu-erh). Data from 29 samples were collected. We hypothesized that the elemental content of infusions could reflect certain features, such as the influence of processing and the type of tea.

CONCLUSION

A chemometric approach (PCA) was applied, and differences between teas and herbal infusions were found. This was further corroborated by explicit differentiation of one botanical family, Theaceae. The influence of packaging (tea bags) on herbal material was identified. The three types of tea (Camellia sinensis) appeared to be separated with PCA, and elemental concentrations in Pu-erh changed with multiple steepings.

The level of 210Pb extraction efficiency in Polish herbal teas and the possible effective dose to consumers

The article presents the results of a study on the level of ²¹⁰Pb efficiency extraction in Polish herbal teas as a possible additional source of this radioactive isotope in the human diet. The twelve most popular herbal teas available in Poland and their infusions in filtered and tap water were analyzed as well as ²¹⁰Pb activity concentrations and effective doses (radiation) were calculated. The highest activity concentration of ²¹⁰Pb in dried plants was determined in cistus - 35.5 Bq kg^-1dry wt, while the lowest was in milk thistle - 3.25 Bq kg^-1dry wt what gives respectively for cistus 46.1 ± 0.7 and 6.50 ± 0.29 mBq for milk thistle per one tea bag. The extraction efficiencies in the filtered water oscillated from 5.1 ± 0.5 for milk thistle to 27.3 ± 0.8% for cistus, while for the tap water they ranged from 7.3 ± 0.6% for lime to 33.3 ± 2.2% for white mulberry. Based on the study, it was found that the analyzed herbal tea consumption would give a small portion of the annual effective dose of ²¹⁰Pb received in Poland - the annual effective radiation dose of ²¹⁰Pb taken with herbal tea infusions (one glass daily) was calculated from 0.08 ± 0.01 to 3.17 ± 0.08 µSv.

Total reflection X-ray fluorescence

Total reflection X-ray fluorescence (TXRF) spectrometry is a non-destructive and surface sensitive multi-element analytical method based on energy dispersive X-ray fluorescence spectrometry with detection limits in the lower picogram range. It utilizes the total reflection of the primary X-ray beam at or below the critical angle of incidence. At this angle, the fluorescence intensity is substantially enhanced for samples present as small granular residue or as thin homogenous layer deposited at the surface of a thick substrate. Generally, two types of application exist: micro- and trace-analysis as well as surface and thin-layer analysis. For micro- and trace-analysis, a small amount of the solid or liquid sample is deposited on an optically flat substrate, typically quartz or polycarbonate. The dried residue is analyzed at a fixed angle setting slightly below the critical angle. Quantification is carried out by means of internal standardization. For surface and thin-layer analysis, the surface of an optically flat substrate is scanned. Variations of the incident angle of the primary X-ray beam provide information about the type and sometimes also the amount of material present at or slightly below the surface of the substrate. Major fields of application are environmental samples, biological tissues, objects of cultural heritage, semiconductors and thin-layered materials and films.