Oolong Tea Samples Research Articles

Determination of trace levels of thiazopyr residues in oolong tea samples using metal sieve-linked double syringe based liquid-phase microextraction coupled with gas chromatography-mass spectrometry

Thiazopyr has raised concerns about its potential impact on human health. Hence, detection of trace levels of thiazopyr herbicide has become critically important. This study presents a highly precise and accurate method to determine thiazopyr at trace levels using a combination of metal sieve-linked double syringe based liquid-phase microextraction (MSLDS-LPME) and Gas Chromatography-Mass Spectrometry (GC-MS) system. A thorough optimization of all parameters affecting the method's efficiency was performed using a univariate optimization approach, followed by an evaluation of the system's analytical performance. Employing the developed method in conjunction with the MSLDS-LPME-GC-MS system yielded a limit of detection (LOD) of 2.73 µg/kg and a limit of quantification (LOQ) of 9.11 µg/kg. To assess the method's applicability, a recovery study was conducted using oolong tea as a real sample matrix, employing a matrix-matching calibration approach. The results of recovery studies demonstrated acceptable recoveries ranging from 87.5 % to 101.9 %.

Comparative study of the volatile fingerprints of roasted and unroasted oolong tea by sensory profiling and HS-SPME-GC-MS

Roasting plays important roles in shaping the volatile profile of oolong tea. In this study, the sensory attributes and volatile compositions of 153 roasted or unroasted oolong tea samples, belonging to four typical types, namely, High Mountain oolong tea (HMT), Tieguanyin tea (TGYT), Dongding oolong tea (DDT) and Wuyi rock tea (WRT), were studied in detail. Based on the sensory evaluation by tea evaluation experts, their respective sensory profiles were established and compared. Unroasted teas had more pronounced fresh and green flavors, while roasted teas had higher scores in pungent and caramel flavors. In particular, WRT demonstrated a unique fragrance of floral fruity flavors. By using HS-SPME-GC-MS analysis, a total of 128 compounds were identified across all samples. Notably, it was found that roasting largely increased the variety of volatile compounds in oolong tea. Furthermore, the characteristic volatile compounds of each type of tea were identified by PLS-DA modeling. Linalool and geraniol were the characteristic volatiles of HMT. Four volatiles, including (E)-nerolidol, jasmin lactone, benzeneacetaldehyde, and 4-methyl benzaldehyde oxime were identified as the characteristic volatiles of TGYT. Seven volatiles, including N-ethyl pyrrole, 3-(hydroxy methyl) pyridine, 4-pyridylcarbinol, 1-methyl pyrrole-2-carboxaldehyde, 2-ethyl-3,5-dimethyl pyrazine, 4-amino-2,3-xylenol, and 4,6-dimethyl pyrimidine were the characteristic volatiles of DDT. For WRT, 2,2,6-trimethyl cyclohexan-1-one, hexanoic acid, benzaldehyde, benzyl alcohol, β-cyclocitral, (E)-β-ionone, α-ionone, and octanoic acid were the characteristic volatiles. These findings expand our knowledge of the volatile fingerprints of oolong tea.

Health-risk Assessment and Evaluation of Different Metals in Different Tea Products Consumed in Jordan Using ICP-MS and ICP-OES

This study aimed to analyze the concentrations of heavy metals and trace elements in black, green, white and oolong tea samples in different brands that are widely consumed in Jordan to assess the health risk associated with their consumption. Inductively Coupled Plasma equipped with Mass Spectrometry and Optical Emission Spectrophoto¬metry (ICP-MS/OES) were used for analysis after sample preparation. The mean concentrations of Cr, Co, Ni, Cu, Zn, As, Se, Sr, Mo, Pb, Sn, Cd, Ca, Fe, K, Mg and Na were found to be in the range of not detected to 135.4 mg/kg and 0.10–389.93 mg/kg for both infused and digested samples, respectively. The daily intake of Ca, K, Na and Mg was found in the range of 0.31–9.03% of their Recommended Dietary Intake (RDA). The Estimated Daily Intake (EDI), Target Hazard Quotient (THQ), Hazard Index (HI) and Target Cancer Risk (TR) were used for the assessment of health risks associated with the metals’ intake. THQ, HI and TR values of all elements were found to be below the allowable limits determined by the World Health Organization (WHO) and the United States Environmental Protection Agent (US-EPA), suggesting that the consumption of different tea products from the Jordanian market does not pose a significant risk to human health.

Quality Characteristics of Oolong Tea Products in Different Regions and the Contribution of Thirteen Phytochemical Components to Its Taste

Regionality is a term used in the tea industry to describe the particular style of tea produced by a growing region. Determining the characteristics of the tea of specific regions can help growers predict tea plant quality before harvesting and eventually production. As such, in this study, we collected representative Oolong tea samples from 15 regions in 8 countries. Quantitative description analysis (QDA) and a flavor wheel were used to analyze their sensory characteristics. Chemometrics was used to screen the phytochemical components that significantly contribute to the taste of Oolong tea. We preliminarily obtained 35 sensory characteristic descriptors and constructed a flavor wheel for Oolong tea. We found that Oolong tea in each region has unique sensory quality characteristics. The content of thirteen phytochemical components of Oolong tea in different regions widely varied, and the average coefficient of variation was 45.56%. Among of them, we found the largest difference in free amino acids. We identified the relationship between taste sub-attributes, and the thirteen phytochemical components was found through correlation analysis. Finally, we selected phytochemical components with significant effects on five taste sub-attributes that were selected from the thirteen detected phytochemical components. The construction of the Oolong tea flavor wheel can help realize the qualitative and quantitative sensory evaluation of Oolong tea from different origins and contribute to the quality identification and directional improvement of Oolong tea products.

Effects of manufacturing procedures and preparation conditions on European Union priority polycyclic aromatic hydrocarbons in Oolong tea samples

The study evaluated the changes in polycyclic aromatic hydrocarbons (PAHs) of Oolong tea samples at each heat treatment stage of the manufacturing process, different post-treatment methods and different brewing conditions. The content of PAHs in the tea leaves was significantly increased during stir fixation (280 °C for 8 min) stage of the manufacturing process. In the subsequent heat treatment process, the PAHs content did not change much until the Oolong tea product (primary) was further roasted. The level of PAHs increased with the roasting time. Charcoal roasting resulted in higher PAHs content in the product compared with electric roasting. Higher brewing temperature caused higher level of PAHs released into the tea infusion. The level of released PAHs decreased with the increase of the number of tea brewing (the total released PAHs was about 4%). The risk assessment results for PAHs in the tea infusions showed a low level of health concern.

Preparation of covalent organic framework based on room temperature solution-suspension approach and its application to solid-phase microextraction of pyrethroids in tea

拟除虫菊酯(PYs)类农药被广泛用于茶园病虫害的防治。随着国内外对进出口茶叶中农药残留限量的要求日益严格,我国迫切地需要开发能应用于检测茶叶中痕量PYs的方法。研究通过简单、温和的溶液悬浮法(SSA),在室温下制备了共价有机骨架(COF)材料TpBD,该材料具有优异的热/化学稳定性、较高的孔隙度和比表面积。通过简单物理黏附的方法,将TpBD制备成固相微萃取(SPME)纤维。将准备好的纤维应用于固相微萃取技术并与气相色谱-串联质谱(GC-MS/MS)联用,建立用于检测PYs的高灵敏分析方法。该方法对氟氯氰菊酯、氯氰菊酯、氟氰菊酯、氰戊菊酯和溴氰菊酯的富集倍数为702~2687,并表现出低的检出限(0.1~0.5 ng/L)、宽的线性范围(0.2~800 ng/L)、良好的线性关系(相关系数≥0.9991)、可接受的重复性(RSD≤11.0%, n=3)。将所建立的方法用于实际绿茶和乌龙茶样品中PYs残留量的检测,并成功地从实际茶样中检测出5种痕量PYs,并且具有满意的回收率(80.2%~109.5%)。实验结果表明,所建立的分析方法适用于茶叶中PYs农药残留量的分析和检测。此外,通过SSA成功地制备了TpBD材料,证实了该方法具有较好的普适性,具有简便合成其他COFs材料的潜力。

Characteristics and upregulation of antioxidant enzymes of kitchen mint and oolong tea kombucha beverages.

Kombucha is a healthy traditional beverage which is made by fermenting products with a symbiotic culture of acetic acid bacteria and yeasts. In present study, leaves of kitchen mint (Mentha cordifolia Opiz. Ex Fresen) and leaves of oolong tea (Camellia sinensis) were fermented in kombucha formula. After fermentation, titratable acidity contents and ethanol of kitchen mint, oolong tea, and mixtures of oolong tea and kitchen mint kombucha samples gradually increased with a period of fermentation time. At day 14 of fermentation, phenolic compounds and flavonoids were increased in all kombucha samples. The numbers of acetic acid bacteria and yeast in kombucha had gradually raised during 7-14days of fermentation. DPPH and ABTS scavenging activities of these kombucha increased over a period of fermentation time and shown the highest antioxidant capacity on day 14 of fermentation. In addition, all kombucha samples exhibited the antioxidant effects by attenuating H2 O2 -induced ROS production, increasing mRNA expression of catalase, glutathione reductase (GRe), and Mn-SOD, and inducing GRe enzymatic activity in HEK-293 cells. Kombucha beverage can be used as the healthy beverages for attenuation of oxidative stress in many diseases.

Effects of fermentation time and shooting period on amino acid derivatives and free amino acid profiles of tea

This study aimed to investigate the effect of oxidation on free amino acids and their derivatives in tea. Oolong tea samples, oxidized for 0, 10, 30, and 60 min, green tea, and black tea were produced from the same batch of fresh tea leaves. Effects of shooting periods on free amino acids and their derivatives were also evaluated in this study. Free amino acids and their derivatives were extracted with water and analyzed by LC-MS/MS. It was observed that total amino acid content of teas in the first shooting period (16231 ± 241 μg/g-31391 ± 2034 μg/g) was higher than the second (9635 ± 379 μg/g-11665 ± 426 μg/g) and third (13937 ± 360 μg/g-17661 ± 1359 μg/g) shooting periods. Content of most amino acids including gamma aminobutyric acid (GABA) in black and oolong teas were higher than those of green tea. However, theanine contents of black and oolong teas were lower than that of green tea. Kynurenine, kynurenic acid, quinolinic acid, dopamine, tyramine, phenylethylamine and tryptamine were found in all tea samples. Kynurenic acid content was the highest (1 ± 0.1 μg/g-3±0.4 μg/g) in green, oolong and black tea samples. Concentrations of kynurenine, kynurenic acid, quinolinic acid, and dopamine were mostly found to be higher in green tea than black tea.

A new PARAFAC-based algorithm for HPLC-MS data treatment: herbal extracts identification.

Role of highly informative high-performance liquid chromatography mass spectrometry (HPLC-MS) methods in quality control is increasing. Complex herbal products and formulations can simultaneously contain extracts from different plants. Therefore, due to the leads to lack of commercial standards it is important to develop novel approaches for comprehensive treatment of big datasets. The aim of this study is to create a straightforward and information-saving algorithm for the identification of plants extracts in commercial products. In total, 34 samples, including Glycyrrhiza glabra and Panax ginseng dried roots; and Abrus precatorius dried leaves, their double and triple mixtures and flavoured oolong tea samples were analysed by HPLC-MS and combined in a three-dimensional dataset (retention time-mass-to-charge ratio (m/z)-samples). This dataset was subjected to smoothing and denoising techniques and further decomposed using parallel factor analysis (PARAFAC). Samples were divided into eight clusters; loading matrices were interpreted and the presence of the most characteristic triterpene glycoside groups was demonstrated and supported by the characteristic chromatogram approach. The occurrence of Abrus precatorius and G. glabra additives in flavoured tea was confirmed. Developed HPLC-MS-PARAFAC method is potentially reliable and an efficient tool for handling untreated experimental data and its future development may lead to more comprehensive evaluation of chemical composition and quality control of food additives and other complex mixtures.

Cellulose nanofibers coated with silver nanoparticles as a flexible nanocomposite for measurement of flusilazole residues in Oolong tea by surface-enhanced Raman spectroscopy

Cellulose nanofibers (CNF) coated with inorganic nanoparticles are novel hybrid nanocomposites that have great potential in various areas including agriculture and food science. The objectives of this study were to synthesize nanocomposites consisted of CNF coated with silver nanoparticles (AgNPs), which can be used as a surface-enhanced Raman spectroscopy (SERS) platform for measuring pesticides in Oolong tea. CNF were coated with AgNPs to form uniform CNF-AgNP nanocomposites that were investigated by transmission electron microscopy. Three-dimensional and porous CNF structures were loaded with AgNPs with an average size of 41 nm. CNF-AgNP substrates were applied in characterization and measurement of flusilazole in Oolong tea samples by SERS. A detection limit of 0.5 mg/kg for flusilazole was obtained based on partial least squares (PLS) regression analysis. These results indicate that CNF-AgNP nanocomposites combined with SERS is an accurate, sensitive, and efficient technique for identification and quantification of pesticide residues in Oolong tea.

A spectroscopic approach to detect and quantify phosmet residues in Oolong tea by surface-enhanced Raman scattering and silver nanoparticle substrate

There have been increasing concerns among consumers about pesticide residues in Oolong tea. This study aimed to establish surface-enhanced Raman scattering (SERS) method for rapid measurement of chemical contaminants in Oolong tea. Synthesis of SERS substrate was achieved by synthesizing silver nanoparticles (AgNPs) via a reduction method. AgNPs were spherical and highly monodispersed, which created remarkable electromagnetic fields during SERS activities to measure phosmet in the methanol-water solution and Oolong tea. Partial least squares regression models were established to predict the concentrations of phosmet in the methanol-water solution (r = 0.934; slope = 0.880; RMSEP = 1.001 mg/L) and Oolong tea samples (r = 0.927; slope = 0.938; RMSEP = 1.157 mg/kg) with the detection limit of 0.1 mg/kg. The results indicate that SERS coupled with silver nanoparticles is a fast, sensitive, and reliable method for detection and characterization of pesticide contaminants in Oolong tea products.

Investigation of free amino acids, bioactive and neuroactive compounds in different types of tea and effect of black tea processing

This study aimed to investigate free amino acids, bioactive amines, and tryptophan derivatives in kynurenine pathway in white, green, oolong, black and pu-erh tea samples. Effects of black tea processing stages (withering, rolling, fermentation and drying) on these compounds were also investigated. Analyses of free amino acids, bioactive and neuroactive compounds were performed by using tandem mass spectrometry. Total free amino acid content of tea increased in withering stage while decreased in drying stage. Although all tea samples were found to contain gamma-aminobutyric acid (GABA) and kynurenic acid, only pu-erh tea contained tyramine and histamine. Furthermore, dopamine was detected in some white (0.8 mg/kg) green (0.3–0.6 mg/kg) and oolong (0.3–0.6 mg/kg) teas. Serotonin, kynurenine and tryptamine were not found in any tea samples. Concentrations of kynurenic acid in white, oolong, green, black and pu-erh tea were found to be within the range of 1.1 ± 0.3 and 13.0 ± 0.9 mg/kg. GABA and kynurenic acid concentration of tea increased 33% and 53% after withering, respectively. Dried tea contained lower GABA and kynurenic acid than withered tea. Tea could have health-promoting effects due to containing neuroactive compounds such as GABA, kynurenic acid and dopamine and, processing stages of tea affects the level of these compounds.

Detection and quantification of carbendazim in Oolong tea by surface-enhanced Raman spectroscopy and gold nanoparticle substrates

The contamination of pesticide residues in Oolong tea has raised much concern in recent years. The objective of this study was to synthesize gold nanoparticles (AuNPs) and develop surface-enhanced Raman spectroscopy (SERS) methods for detection and quantification of pesticides in Oolong tea. Facile synthesis of spherical and monodispersed AuNPs with an average diameter of 15 nm was achieved, which induced strong electromagnetic fields in SERS analysis. AuNP substrates were employed for rapid detection and quantification of carbendazim in Tieguanyin Oolong tea. Partial least squares (PLS) analysis and leave-one-out cross validation were utilized in spectral data analysis. The PLS results for Oolong tea samples were obtained: R value = 0.964; the detection limit = 100 μg/kg. These results demonstrate that SERS coupled with gold nanoparticle substrate is a simple, rapid, and sensitive analytical tool for measurement and quantification of carbendazim residues in Oolong tea.

UHPLC analysis of major functional components in six types of Chinese teas: Constituent profile and origin consideration

In this study, an effective ultra-high performance liquid chromatography (UHPLC) method for simultaneous determination of 15 constituents of catechins, caffeine, gallic acid and theaflavins was developed. Employing the developed UHPLC method, the contents of the 15 constituents were analyzed in 245 samples of 6 types of Chinese teas collected from different places. The catechin contents in these samples ranged from 16.50 to 94.35 mg/g. Theaflavins were not detected in green tea and white tea, and caffeine did not strongly relate to germplasm resource or fermentation degree. Principal component analysis (PCA) of UHPLC data revealed that white, oolong and green tea samples could be clustered closely, demonstrating notable difference of functional components between the three types of teas resulting from preparation process and varieties. The constituent profile could be primarily attributed to the structural transformation of catechins and pigments during tea processing. This study would advance our understanding of chemical profile of Chinese teas afforded by different processing technologies.

Identification of natural antimicrobial peptides from bacteria through metagenomic and metatranscriptomic analysis of high-throughput transcriptome data of Taiwanese oolong teas

BackgroundAnti-microbial peptides (AMPs), naturally encoded by genes and generally containing 12–100 amino acids, are crucial components of the innate immune system and can protect the host from various pathogenic bacteria and viruses. In recent years, the widespread use of antibiotics has resulted in the rapid growth of antibiotic-resistant microorganisms that often induce critical infection and pathogenesis. Recently, the advent of high-throughput technologies has led molecular biology into a data surge in both the amount and scope of data. For instance, next-generation sequencing technology has been applied to generate large-scale sequencing reads from foods, water, soil, air, and specimens to identify microbiota and their functions based on metagenomics and metatranscriptomics, respectively. In addition, oolong tea is partially fermented and is the most widely produced tea in Taiwan. Many studies have shown the benefits of oolong tea in inhibiting obesity, reducing dental plaque deposition, antagonizing allergic immune responses, and alleviating the effects of aging. However, the microbes and their functions present in oolong tea remain unknown.ResultsTo understand the relationship between Taiwanese oolong teas and bacterial communities, we designed a novel bioinformatics scheme to identify AMPs and their functional types based on metagenomics and metatranscriptomic analysis of high-throughput transcriptome data. Four types of oolong teas (Dayuling tea, Alishan tea, Jinxuan tea, and Oriental Beauty tea) were subjected to 16S ribosomal DNA and total RNA extraction and sequencing. Metagenomics analysis results revealed that Oriental Beauty tea exhibited greater bacterial diversity than other teas. The most common bacterial families across all tea types were Bacteroidaceae (21.7%), Veillonellaceae (22%), and Fusobacteriaceae (12.3%). Metatranscriptomics analysis results revealed that the dominant bacteria species across all tea types were Escherichia coli, Bacillus subtilis, and Chryseobacterium sp. StRB126, which were subjected to further functional analysis. A total of 8194 (6.5%), 26,220 (6.1%), 5703 (5.8%), and 106,183 (7.8%) reads could be mapped to AMPs.ConclusionWe found that the distribution of anti-gram-positive and anti-gram-negative AMPs is highly correlated with the distribution of gram-positive and gram-negative bacteria in Taiwanese oolong tea samples.

Geographical Origin Discrimination of Oolong Tea (TieGuanYin, Camellia sinensis (L.) O. Kuntze) Using Proton Nuclear Magnetic Resonance Spectroscopy and Near-Infrared Spectroscopy

A total of 90 oolong tea samples were collected from three different growing places in the Fujian province of China. Both proton nuclear magnetic resonance (1H NMR) and near-infrared spectroscopy (NIR) were used to analyze the collected tea samples. With the aid of chemometric methods, differential components in 1H NMR data and characteristic wavenumbers from NIR spectra were identified. Since NMR and NIR provide complementary information for tea samples, data fusion was carried out by combining 1H NMR and NIR spectra of the collected tea sample. Experimental results showed that a better discrimination accuracy of geographical origins of oolong tea could be achieved by combining NMR and NIR data (86.2–95.8%), as compared to using NMR data (68.2–78.7%) or NIR data (80.0–89.3%) alone. The current data suggested that a combination of NMR and NIR methods could serve as an efficient way for geographical origin discrimination and qualitative control of oolong tea.

Determination of Contents of Catechins in Oolong Teas by Quantitative Analysis of Multi-components Via a Single Marker (QAMS) Method

The catechins in oolong tea are related to its flavor and health benefits. In this paper, a new strategy for a quantitative analysis of multi-components via a single marker (QAMS) was developed and validated to analyze six catechins (epigallocatechin, catechin, epicatechin, epigallocatechin gallate, gallocatechin gallate, and epicatechin gallate) in oolong tea by HPLC. Catechin was chosen as the internal reference substance. The relative correction factors (RCFs) between catechin and the other five catechins were investigated for the QAMS calculation using five different types of chromatographic columns. Meanwhile, the content of each of the six analytes was also determined by a conventional external standard method. Finally, the angle cosine value revealed that there was no significant difference between the QAMS method and the external standard method. The QAMS method established in this study solved the problem of the availability and high cost of some standard substances and would be useful for providing an efficient and feasible quality assessment method for oolong tea and other botanic samples.

Theanine and Caffeine Content of Infusions Prepared from Commercial Tea Samples.

Background:Caffeine and L-theanine are pharmacologically important constituents of tea, especially due to their effects on the central nervous system. The effects of these two compounds are opposite: While caffeine is a well-known stimulant, theanine has a relaxing effect. Tea processing may influence the caffeine and theanine content of tea leaves.Objective:The aim of our work was to quantify these constituents from a set of commercial products to reveal the possible correlations of caffeine and theanine content and processing methods.Materials and Methods:Theanine and caffeine contents of 37 commercial white, green, oolong, black, and pu-erh tea samples were quantified by high-performance liquid chromatography-diode array detector.Results:The mean L-theanine content of white, green, oolong, and black teas were 6.26, 6.56, 6.09, and 5.13 mg/g, respectively. The same values for caffeine content were 16.79, 16.28, 19.31, and 17.73 mg/g.Conclusion:Though the effect of processing on theanine content was evident, quantification for these analytes does not seem to be a good criterion to discriminate the different types of tea. Caffeine content provided no information on the effect of processing, and the theanine content of the samples was rather variable, independently from the type of the tea. The quantitative analysis of caffeine and theanine is essential to assess the stimulating effect of the tea, however, for chemical profiling further secondary metabolites have to be determined.SUMMARY Thirty-seven commercial white, green, oolong, black, and pu-erh tea samples were analyzed for caffeine and theanine contentWhile the caffeine content was similar, the theanine contents of black teas were slightly lower and practically zero in pu-erhThe great variability of these two compound within the tea categories allows no discrimination of tea types based solely on theanine and caffeine quantificationContrary to the previous data, the way of processing has no determining effect on theanine content. FigureAbbreviations used: CZE: Capillary zone electrophoresis, DAD: Diode array detector, EEG: Electroencephalography, GC: Gas chromatography, HPLC: High-performance liquid chromatography, IR: Infrared spectroscopy, MEKC: Micellar electrokinetic capillary chromatography, MS: Mass spectrometry, RP: Reversed phase, RSD: Relative standard deviation, SD: Standard deviation, TLC: Tile liquid chromatography, UV: Ultraviolet

Trace elements in Camellia sinensis marketed in southeastern Brazil: Extraction from tea leaves to beverages and dietary exposure

The presence of Al, As, Ba, Cd, Cr, Cu, Fe, Mn, Ni, Pb, Se, and Zn in 30 samples of tea (Camellia sinensis) purchased from markets in southeastern Brazil were evaluated by ICP-MS. This study was performed for both tea leaves and their infusions. The results provide data that permits an evaluation of the exposure or dietary intake of these trace elements. For some samples, the levels in the tea leaves were above the standards established by the Brazilian and MERCOSUL regulatory bodies. For example, As was detected in 33% of the red oolong tea samples and Pb was detected in 67% and 100% of the white and red oolong samples, respectively. Although some of these tea leave samples possessed high toxic elements levels, the concentrations of the trace elements in the infusions were measured to be at safe levels. An evaluation of dietary intake demonstrated the remarkable importance of tea in achieving the daily intake of manganese. Indeed, a single cup of green tea may provide 16% of the daily value established by FDA. Principal component analysis classified the tea into three distinct groups on the basis of the inorganic constituents in the tea leaves.

High Throughput Analytical Techniques for the Determination and Confirmation of Residues of 653 Multiclass Pesticides and Chemical Pollutants in Tea by GC/MS, GC/MS/MS, and LC/MS/MS: Collaborative Study, First Action 2014.09.

Thirty laboratories from fom North and South America, Europe, and Asia participated in this AOAC collaborative study (15 from China; five from Germany; two each from Italy and the United States; and one each from the Republic of Korea, Canada, Spain, Japan, Belgium, and India). Participants represented government regulatory, commercial testing, university, research institute, and private laboratories. The single-laboratory validated (SLV) tea method was evaluated in the collaborative study to determine the recovery and reproducibility of the method under multilaboratory conditions. Since there were no restrictions regarding the type of analytical instrumentation to use for the analyses, laboratories used a combination of equipment that included GC/MS, GC/MS/MS, and LC/MS/MS instruments from 22 different manufacturers, 21 brands of GC and LC columns, 13 different GC temperature programming profiles, 11 LC gradient elution programs, and six different vendor manufactured SPE cartridges. Even though all the analytical performance parameters for all the 653 compounds had been determined in the SLV study, guidance was obtained from an expert review panel of the AOAC Method-Centric Committee on Pesticide Residues to conduct the multilaboratory collaborative study based on 20 selected compounds that can be analyzed by GC/MS and 20 compounds that can be analyzed by LC/MS/MS. Altogether, 560 samples covering the 40 selected pesticides were analyzed in the study. These samples included green tea and oolong tea samples fortified typically at the European Union maximum residue limit for regulatory guidance and compliance, aged tea samples incurred with 20 pesticides, and green tea and oolong tea samples incurred with five pesticides. The analysis of the 560 samples generated a total of 82 459 test results by the 30 participating laboratories. One laboratory failed to meet the proficiency requirements in the precollaborative study. Therefore, its data submitted for the collaborative study were excluded from further analysis and interpretation. The results presented are therefore the 6638 analytical results obtained from the 29 remaining laboratories, which included 1977 results generated by GC/MS, 1704 results by GC/MS/MS, and 2957 results by LC/MS/MS. It was determined after application of the Grubbs and Dixon tests for outliers to the data sets that there were 65 outlier results from the 1977 GC/MS results (3.3%), 65 outlier results from the 1704 GC/MS/MS results (3.8%), and 57 outlier results out of 2957 LC/MS/MS results (1.9%), representing 0.98, 0.98, and 0.86%, respectively, of the 6638 results generated in the study. Analysis with the AOAC statistical software package also confirmed that the method is rugged, and average recovery, average concentration, RSDr, RSDR, and HorRat values all meet recovery and reproducibility criteria for use in multiple laboratories. The Study Director is recommending this method for adoption as an AOAC First Action Official MethodSM.