Chlorate and perchlorate in tea leaves from major producing regions in China and related human exposure risk.

Chlorate and perchlorate are emerging pollutants that may interfere with thyroid function. Since they are highly water soluble, chlorate and perchlorate in tea leaves cause health concerns but have scarcely been studied. In this study, chlorate and perchlorate concentrations in 216 tea samples from different regions of China were determined. Perchlorate was detected in all the samples with a median concentration of 44.1 µg kg-1, while the chlorate detection frequency was 15.7%. We observed regional differences in perchlorate contents in tea leaves, with the highest quantity found in the central region of China. Except for dark tea, the concentration of perchlorate in tea infusions decreased with the increased number of times the tea leaves were brewed. The hazard quotients (HQs) of chlorate and perchlorate in all the samples were less than 1, suggesting negligible health risks caused by these pollutants from tea consumption. To the best of our knowledge, this is the first study to investigate chlorate and perchlorate contamination in tea infusions by simulating brewing behavior.

Monitoring and risk assessment of perchlorate in tea samples produced in China.

Accumulation of potentially perchlorate in tea is a new concern for tea consumers. The information on perchlorate contamination in tea is highly limited. This study aimed to investigate the occurrence and accumulation of perchlorate in tea samples from China and to assess human exposure risks. A total of 288 tea samples collected from 16 provinces of China were tested, and nearly 94.8% of the samples were found to have detectable perchlorate contamination. Concentrations of perchlorate ranged from below LOQ to 1274.3 µg/kg, with a mean value of 294.6 µg/kg. Tea samples collected from Central China had the highest mean perchlorate concentration (403.4 µg/kg). The mean and median perchlorate levels in the dark and black samples were much higher than that of other types of tea samples. After brewing tea, the dissolution rates of perchlorate from the dried tea ranged from 58.9% to 89.2%. For the worst-case scenario, the estimated daily intakes (EDIs) of tea samples in 16 investigated provinces ranged from 25.9 to 157.8 ng/kg bw/day and 29.7-180.7 ng/kg bw/day for male and female respectively, indicating no significant health risks to local residents via tea consumption.

Accumulation and distribution of perchlorate in spinach and chard growing under greenhouse: Implications for food safety in baby foods commodities.

Very little information is available with regards to the bioavailability of perchlorate in spinach or chard used in the production of baby foods commodities. In the present study, the uptake and accumulation of perchlorate were compared under two different treatments (T1: 1 and T2: 10 mg L-1 ClO4-). Our results indicate that spinach has a higher capacity to accumulate perchlorate than chard (p < 0.0185). Concentrations of perchlorate in leaves, stems and roots (leaves > stem > roots) all gradually increased (p < 0.0001) as vegetable growing and treatment (T2 > T1). No significant differences were found between the control and T1. The daily intake for perchlorate (control) is below the proposed international standard, however, it was exceeded in T1 and T2. The results suggested that perchlorate is actively accumulate in high concentrations in vegetables used in the production of baby food commodities and the exposure of perchlorate via the food consumption (baby foods) was evaluated as not safe.

Biosynthesized silver nanoparticle-coated electro-membrane extraction of perchlorate in different seafood samples.

In this work we developed a rapid and straightforward technique in which biosynthesized silver nanoparticles (Ag-NPs) were coated on a porous membrane utilizing electrical potential to extract perchlorate from seafood samples. The biosynthesized Ag-NPs were well characterized using UV-Vis. spectrophotometry, X-ray diffraction, and scanning electron microscopy. After extraction, analyses were performed using ion chromatography. The Ag-NP-coated porous polypropylene membrane shows higher extraction efficiency due to the high electrical conductivity of the Ag-NPs. The performance of this efficient technique was compared with those previously reported in the literature. The extraction variables that affect extraction of the target analyte and influence percentage recovery, such as pH of the sample solution, extraction time, and applied voltage, were investigated and optimized. The results demonstrated optimum conditions to achieve low detection limits [LODs (limits of detection)]: sample solution (pH = 6), short extraction time (10 min), and applied voltage (5 V). The developed method shows excellent linearity for perchlorate ion in the range from 0.001 to 350 µg L-1 with a coefficient of determination (r2 ) of 0.9991. The detection limit (LODs) and quantification limits (limits of quantification) were found to be 0.04 and 0.1225 µg kg-1 , respectively. The mean recovery percentages for three replicates of 10 different spiked fish samples by 3 µg g-1 of perchlorate were between 92.2 and 106.2%, with an observed relative standard deviation in the range of 0.8-3.7%. The proposed method is rapid, sensitive, inexpensive, environmentally friendly, and highly effective in extracting perchlorate from different seafood samples.

A highly-efficient and cost-effective pretreatment method for selective extraction and detection of perchlorate in tea and dairy products.

In view of the high polarity and ubiquitous occurrence of perchlorate, achieving an ultra-trace analysis has become a challenging task. The present study aimed to develop a simple and generic pretreatment protocol based on cold-induced liquid-liquid extraction to efficiently extract perchlorate from tea and dairy products and remarkably decrease potential matrix interferences and laborious cleanup. By optimizing the pretreatment conditions, the enrichment factor of perchlorate increased by 7.79 times under the compromise between the matrix effect and extraction recovery. The validated method presented satisfactory selectivity, linearity, accuracy, precision, and matrix effect, providing recoveries of 78.2%-106.2% with RSDr ranging from 1.2% to 7.9% and RSDR less than 10.7% for tea and dairy products. This pretreatment protocol depended only on shaking, freezing, and centrifugation in one step, without additional equipment or tedious operations, which will be explored to a greater extent in complex biological or food matrices.

LC-ESI-MS/MS determination of oxyhalides (chlorate, perchlorate and bromate) in food and water samples, and chlorate on household water treatment devices along with perchlorate in plants.

The results of the validation study of the LC-ESI-MS/MS method for the determination of chlorate (ClO3-), perchlorate (ClO4-) and bromate (BrO3-) in water and food samples are summarized. Towards this, 284 samples of drinking water were analysed, out of which the 69% contained chlorate above the limit of quantitation (LOQ) of 0.01 mg/L, with maximum amount of 1.1 mg/L. Only 6 samples were found to be positive with perchlorate at levels <0.01 mg/L. Bromate was detected in 5 drinking water samples at levels above the LOQ, at concentrations up to 0.026 mg/L. For the validation of the method in food, 108 blank samples were spiked with chlorate and perchlorate for the LC-MS/MS analysis at two levels. In total 247 food samples from the market of 19 different commodities including fruits, vegetables, cereals and wine, were analysed. The maximum concentration of chlorate was found at 0.83 mg/kg in a sample of cultivated mushrooms. The number of samples contaminated with perchlorate was also small, with all the determined concentrations below the LOQ of 0.05 mg/kg. Experiments for the chlorate reduction in drinking water, showed that reverse osmosis treatment is effective in particular with newly installed cartridges. Finally, according to the results of the pilot study when chlorinated water is used for the plant irrigation, accumulation of chlorate is observed, especially in the green parts of the plant. Perchlorate was also detected in leafy samples, although it was not present in the irrigation water.

Quantitative determination and contamination pattern of perchlorate in tea by ultra performance liquid chromatography and tandem mass spectrometry.

Perchlorate causes great health concerns for its inhibition on the iodide intake of human. However, the contamination pattern of perchlorate in tea remains unclear although tea is substantially consumed worldwide. Thus, the present study established an efficient method using ultra performance liquid chromatography-tandem mass spectrometry (UPLC-MS/MS) in combination with external standard method, and further lucubrated the contamination level of perchlorate in made tea, fresh tea leaves, along with the waters and soils from tea gardens. Fresh tea leaves with higher maturity generally contains more perchlorate. The observation explains well why the residual of perchlorate in dark tea is generally higher than that in black tea or green tea from the perspective of raw material. In consideration of the ubiquitous existence of perchlorate in waters and soils from tea gardens, perchlorate might accumulate in tea leaves via soil. This study not only provides an alternative quantification method of perchlorate when the isotope internal standard is out of stock, but also illuminates the contamination pattern of perchlorate in tea from planting process.

Determination of perchlorate from tea leaves using quaternary ammonium modified magnetic carboxyl-carbon nanotubes followed by liquid chromatography-tandem quadrupole mass spectrometry.

The novel quaternary ammonium modified magnetic carboxyl-carbon nanotubes (QA-Mag-CCNTs) have been synthesised and characterized. QA-Mag-CCNTs were applied in magnetic dispersive solid phase extraction (Mag-dSPE) for preconcentration of perchlorate from tea leaves prior to liquid chromatography-tandem quadrupole mass spectrometry (LC-MS/MS) analysis. The Mag-dSPE procedure for preconcentration of perchlorate succeed in overcoming the flaw (containing target analyte randomly) of commercially available SPE cartridge. Under optimal conditions, the results showed higher extraction efficiency of QA-Mag-CCNTs, with recoveries between 85.2% and 107%. And the satisfactory precision with inter-day and intra-day RSD values were lower than 8.0%. Furthermore, QA-Mag-CCNTs were evaluated for reuse up to 20 times. The limit of quantification (LOQ) for perchlorate was 8.21 ng kg-1. The developed method was successfully applied in tea leaves for food-safety risk monitoring in Zhejiang province, China. The results showed the concentrations of perchlorate in 229 out of 240 collected samples were in the range of 0.082-988 µg kg-1. It was confirmed that QA-Mag-CCNTs were highly effective materials used for preconcentration of perchlorate.

Quantitative determination of perchlorate in bottled water and tea with online solid phase extraction high-performance liquid chromatography coupled to tandem mass spectrometry.

Due to the similarity in ionic radius, perchlorate has been reported to inhibit the iodide intake in the thyroid gland, which may lead to low heart rate, weight gain, and fatigue. In recent years, the presence of perchlorate in drinking water, surface water, soil, and food supplies in the United States has raised a great concern on establishing the maximum residue limit (MRL) for perchlorate to reduce its possible adverse influence on human health. US EPA currently puts perchlorate on the final third Contamination Candidate List (CCL3) and suggests a health reference level at 4.9 µg L⁻¹. The MRL of perchlorate was therefore set at 5.0 µg L⁻¹ by the authors for method validation. In this study, large volume injection (up to 1-mL) and online solid phase extraction (SPE) were utilized for pre-concentrating perchlorate ions and removing unretained matrix components prior to reversed-phase HPLC analysis using ESI-tandem MS under the negative mode. After eluting perchlorate from online SPE, 0.1% formic acid solution was utilized for isocratic HPLC analysis without any organic solvent. Multiple reaction monitoring (MRM) and the internal standard, Cl18O4⁻, were utilized for quantitatively determining perchlorate in bottled water and bottled tea samples. Two linear ranges, 0.05-0.50 µg L⁻¹ and 0.50-10.00 µg L⁻¹, were established to better estimate the residual amounts of perchlorate in bottled water samples with a method detection limit (MDL, signal-to-noise ratio of 3) of 0.01 µg L⁻¹. The linear range was 1.50-10.00 µg L⁻¹ for bottled tea samples with a MDL of 0.5 µg L⁻¹. In addition, the proposed method was further validated based on the EU Commission Decision 2002/657/EC, including within-laboratory reproducibility, decision limit (CCα), and detection capability (CCß) for bottled water and bottled tea samples. The intra-day/inter-day precision and accuracy as well as within-laboratory reproducibility were determined by calculating the relative standard deviation (RSD) at three spiked levels (0.5 MRL, 1 MRL, 1.5 MRL). The within-laboratory reproducibility (n=18) for both bottled water and bottled tea samples, spiked at MRL (5.0 µg L⁻¹) of ClO4⁻, was less than 10%. The values of CCα/CCß were reported as 5.43/5.74 µg L⁻¹ and 5.03/5.75 µg L⁻¹ for bottled water and bottled tea samples, respectively.

Determination of low levels of perchlorate in lettuce and spinach using ion chromatography-electrospray ionization mass spectrometry (IC-ESI-MS).

A sample preparation method was developed to quantify environmentally relevant (low micrograms per liter) concentrations of perchlorate (ClO4(-)) in leafy vegetables using IC-ESI-MS. Lettuce and spinach were macerated, centrifuged, and filtered, and the aqueous extracts were rendered water-clear using a one-step solid-phase extraction method. Total time for extraction and sample preparation was 6 h. Ion suppression was demonstrated and was likely due to unknown organics still present in the extract solution after cleanup. However, this interference was readily eliminated using a Cl(18)O4(-) internal standard at 1 microg/L in all standards and samples. Hydroponically grown perchlorate-free butterhead lettuce was spiked to either 10.3 or 37.7 microg/kg of fresh weight (FW), and recoveries were between 91 and 98% and between 93 and 101%, respectively. Five types of lettuce and spinach from a local grocery store were then analyzed; they contained from 0.6 to 6.4 microg/kg of FW. Spike recoveries using the store-bought samples ranged from 89 to 100%. The method detection limit for perchlorate in plant extracts is 40 ng/L, and the corresponding minimum reporting limit is 200 ng/L or 0.8 microg/kg of FW.

Determination of actinide speciation in solution using high-energy X-ray scattering.

High-energy X-ray scattering (HEXS) has been used to understand the coordination environment of the uranyl ion in a perchlorate solution. Assuming the two coordinating oxo ligands bound to U(VI) are represented in a peak in the pair distribution function (PDF) at 1.766(1) A, integration of the peak intensity is used to quantify the charge located on the oxygens. The dioxo ligands are essentially neutral, as predicted by numerous published calculations, with a charge of -16.4(8) electrons. The peak in the PDF at 2.420(1) A is consistent with equatorial ligating waters. The intensity of this peak is inconsistent with an integral coordination number and is used to propose a solution equilibrium of five and four waters coordinating to the uranyl(VI) ion favoring the five-coordinate species. This equilibrium is then used to experimentally determine that five-coordinate uranyl is 1.19+/-0.42 kcal/mol more stable than its four-coordinate counterpart under the conditions of the experiment. Further peaks in the Fourier transform of the scattering data at 4.50, 7, and 8.7 A are attributed to uranium-solvent correlations.