A.M. Abd El-Aty

Residues and contaminants in tea and tea infusions: a review

Consumers are very aware of contaminants that could pose potential health hazards. Most people drink tea as an infusion (adding hot water); however, in some countries, including India, China and Egypt, tea is drunk as a decoction (tea and water are boiled together). An infusion usually brings the soluble ingredients into solution, whereas a decoction brings all soluble and non-soluble constituents together. Therefore, a cup of tea may contain various kinds of contaminants. This review focuses on green and black tea because they are most commonly consumed. The target was to examine the transfer rate of contaminants – pesticides, environmental pollutants, mycotoxins, microorganisms, toxic heavy metals, radioactive isotopes (radionuclides) and plant growth regulators – from tea to infusion/brewing, factors contributing to the transfer potential and contaminants degradation, and residues in or on the spent leaves. It is concluded that most contaminants leaching into tea infusion are not detected or are detected at a level lower than the regulatory limits. However, the traditional practice of over-boiling tea leaves should be discouraged as there may be a chance for more transfer of contaminants from the tea to the brew.

Dynamic behaviour and residual pattern of thiamethoxam and its metabolite clothianidin in Swiss chard using liquid chromatography-tandem mass spectrometry.

A simultaneous method was developed to analyse thiamethoxam and its metabolite clothianidin in Swiss chard using tandem mass spectrometry (in the positive electrospray ionisation mode using multiple reaction monitoring mode) to estimate the dissipation pattern and the pre-harvest residue limit (PHRL). Thiamethoxam (10%, WG) was sprayed on Swiss chard grown in two different areas under greenhouse conditions at the recommended dose rate of 10 g/20 L water. Samples were collected randomly up to 14 days post-application, extracted using quick, easy, cheap, effective, rugged, safe (QuEChERS) acetate-buffered method and purified via a dispersive solid phase extraction (d-SPE) procedure. Matrix matched calibration showed good linearity with determination coefficients (R(2)) ⩾ 0.998. The limits of detection (LOD) and quantification (LOQ) were 0.007 and 0.02 mg/kg. The method was validated in triplicate at two different spiked concentration levels. Good recoveries (n=3) of 87.48-105.61% with relative standard deviations (RSDs) < 10 were obtained for both analytes. The rate of disappearance of total thiamethoxam residues in/on Swiss chard was best described by first-order kinetics with half-lives of 6.3 and 4.2 days. We predicted from the PHRL curves that if the residues were <19.21 or 26.98 mg/kg at 10 days before harvest, then total thiamethoxam concentrations would be below the maximum residue limits during harvest.

Consequences of the matrix effect on recovery of dinotefuran and its metabolites in green tea during tandem mass spectrometry analysis

Determining the residues of dinotefuran and its metabolites (MNG, UF, and DN) is highly problematic because of their polar characteristics. Additionally, tea contains many compounds that can interfere with residue analysis. Thus, the aim of the present study was to refine the extraction method that assures good recoveries for dinotefuran and its metabolites and removes most of the matrix components in green tea using liquid chromatography-tandem mass spectrometry (LC/MS/MS). We attempted to increase the extraction efficiency of the QuEChERS method by selecting the appropriate solvents among ethyl acetate, acetone, isopropanol, 25% methanol in acetonitrile, and methanol. We found that methanol was the best extraction solvent for dinotefuran and its polar metabolites in dry green tea samples; however, due to a limitation of an appropriate partitioning salt, acetonitrile was used as the extraction solvent. Matrix enhancement and suppression effects were observed for all analytes, which made the recovery rates variable. DN recovery was <70% when compared with matrix-matched calibration, whereas it was within the acceptable range (70-120%) when compared with solvent calibration. The opposite was observed for MNG and dinotefuran due to a matrix suppression effect. UF recovery was consistent in both matrix-matched and solvent calibrations despite having little suppressive effect. The method was successfully applied and dinotefuran and its metabolite residues were found in field-incurred green tea samples. The current findings suggest that using methanol as an appropriate QuEChERS solvent for problematic polar pesticides and investigating a suitable partitioning salt would considerably strengthen the practical impact of such data.

Simultaneous multi-determination and transfer of eight pesticide residues from green tea leaves to infusion using gas chromatography

A method for determining eight pesticide (cyhalothrin, flufenoxuron, fenitrothion, EPN, bifenthrin, difenoconazole, triflumizole, and azoxystrobin) residues in made green tea as well as a tea infusion (under various brewing water temperatures; 60, 80, and 100°C) using gas chromatography (GC) micro-electron capture detector (μECD) was developed and validated. The extraction method adopted the relatively commonly used approach of solid sample hydration, with the green tea hydrated before being extracted through salting out with acetonitrile followed by a cleanup procedure. The analytes were confirmed using GC-coupled to tandem mass spectrometry (GC/MS/MS) with a triple quadrupole. The linearity of the calibration curves yielded determination coefficients (R(2)) >0.995. Recoveries were carried out using blank samples spiked with all analytes at two levels. The results demonstrated that all pesticides were recovered within the range of 77-116% with a relative standard deviation (RSD) ⩽14%. The quantification limits of 0.015-0.03 mg/kg were lower than the maximum residue limits (MRLs) set by the Korea Food and Drug Administration (KFDA) for all analytes (0.05-10mg/kg). The infusion study indicated that cyhalothrin, flufenoxuron, and bifenthrin did not infuse into the tea brew from the made tea. Increases in brewing time resulted in increased transfer of azoxystrobin, fenitrothion, and difenoconazole from the made tea to the brew; however, this was not the case with triflumizole or EPN. We conclude that transfer of pesticides appeared to be dependent on their water solubilities and drinking a cup of tea is recommended to be at a water temperature of 60°C.

Residue analysis of orthosulfamuron herbicide in fatty rice using liquid chromatography–tandem mass spectrometry

In the present study, orthosulfamuron residues were extracted from fatty (unpolished) rice and rice straw using a modified QuEChERS method and analyzed using liquid chromatography–tandem mass spectrometry. The matrix-matched calibration was linear over the concentration ranges of 0.01–2.0 mg/kg with determination coefficient (R2) ⩾ 0.997. The recovery rates at two fortification levels (0.1 and 0.5 mg/kg) were satisfactory and ranged between 88.1% and 100.6%, with relative standard deviation (RSD) <8%. The limit of quantitation, 0.03 mg/kg, was lower than the maximum residue limit, 0.05 mg/kg, set by the Ministry of Food and Drug Safety in the Republic of Korea. The developed method was applied successfully to field samples harvested at 116 days and none of the samples were positive for the residue.

Analyses and decreasing patterns of veterinary antianxiety medications in soils

An ultrasonic-assisted extraction method was developed to detect 16 antianxiety medications in soil samples using liquid chromatography-high resolution mass spectrometry (LC-HRMS), Orbitrap mass spectrometer. The determination method resulted in satisfactory sensitivity, linearity, recovery, repeatability, and within-laboratory reproducibility. Acepromazine, azaperone, and xylazine were incubated in control, amended, and sterilized soils. The amendment with powdered blood meal affected the relatively fast dissipations of acepromazine, azaperone, and xylazine in the soils. Dissipation kinetics of acepromazine were consistent with bi-phasic kinetics (first-order multi compartment) and the other couples were fit to single first-order kinetics. A hydroxylated acepromazine was identified from soil samples using Orbitrap mass spectrometry. According to sorption batch experiments, the adsorption of acepromazine and azaperone was greatly high, whereas that of xylazine was relatively low. Xylazine was persistent in the incubated soils, and acepromazine demonstrated fast initial dissipation; hence, xylazine could have a potential harmful effect on the environment. To the best of our knowledge, this is the first report on the dissipation and adsorption-desorption patters of animal pharmaceutical tranquilizers and α, β-blockers.

The effects of different night-time temperatures and cultivation durations on the polyphenolic contents of lettuce: Application of principal component analysis.

The present study was conducted to characterize the polyphenolic contents of lettuce leaves grown under different night-time temperatures (4, 12, and 20 °C) and cultivation durations (5, 15, and 20 days) using high performance liquid chromatography-tandem mass spectrometry (LC/MS/MS). The assay method was validated based on specificity, linearity, accuracy, precision, and the performance limit. The total polyphenolic contents were highest (2462.6 mg/kg) after transplantation at a night temperature of 20 °C on day 20 and lowest (1132.7 mg/kg) at the same temperature on day 5. Quantification and principal component analysis showed that the relative contents of quercetin and kaempferol were markedly higher during the early stage of cultivation (day 5) than those of day 15 and 20, and that night-time temperatures of 12 and 20 °C on day 20 were favorable for producing polyphenol-rich lettuce containing caffeic acid. In conclusion, a synergistic effect between high night-time temperatures (12 and 20 °C) and cultivation duration (20 days) produced lettuce rich in polyphenols compared to that at low temperature (4 °C).

Analysis of abamectin residues in green tea using QuEChERS method and liquid chromatography-tandem mass spectrometry

The present study estimated the residue levels of abamectin (B1a) in green tea leaves and tea infusion. Samples were hydrated with water prior to extraction by using the quick, easy, cheap, effective, rugged, safe method and was analyzed with liquid chromatography-tandem mass spectrometry in positive ion mode. The matrix-matched calibration was linear over the concentration range of 0.01–2mg/kg with determination coefficients (R2) >0.995. Recovery rates at two spiking levels (0.1 and 0.5 mg/kg) ranged between 80.5–99.7% with a relative standard deviation <11%. The compound was stable at 20°C for 174 days with a recovery estimate of 109.9%. Although the maximum residue limit was not established by the Ministry of Food and Drug Safety, Republic of Korea, the limit of quantitation was very low at 0.01 mg/kg. The method was successfully applied to field incurred samples and detected residue of 0.02 mg/kg in green tea samples sprayed twice (7-3 days). Abamectin was not transferred to tea infusion.