PCDD/PCDF, chlorinated pesticides and PAH in Chinese teas

Monitoring of environmental exposure to polycyclic aromatic hydrocarbons: a review

Polycyclic aromatic hydrocarbons (PAHs) are a large group of organic compounds with two or more fused aromatic rings. They have a relatively low solubility in water, but are highly lipophilic. Most of the PAHs with low vapour pressure in the air are adsorbed on particles. When dissolved in water or adsorbed on particulate matter, PAHs can undergo photodecomposition when exposed to ultraviolet light from solar radiation. In the atmosphere, PAHs can react with pollutants such as ozone, nitrogen oxides and sulfur dioxide, yielding diones, nitro- and dinitro-PAHs, and sulfonic acids, respectively. PAHs may also be degraded by some microorganisms in the soil. PAHs are widespread environmental contaminants resulting from incomplete combustion of organic materials. The occurrence is largely a result of anthropogenic emissions such as fossil fuel-burning, motor vehicle, waste incinerator, oil refining, coke and asphalt production, and aluminum production, etc. PAHs have received increased attention in recent years in air pollution studies because some of these compounds are highly carcinogenic or mutagenic. Eight PAHs (Car-PAHs) typically considered as possible carcinogens are: benzo(a)anthracene, chrysene, benzo(b)fluoranthene, benzo(k)fluoranthene, benzo(a)pyrene (B(a)P), dibenzo(a,h)anthracene, indeno(1,2,3-cd)pyrene and benzo(g,h,i)perylene. In particular, benzo(a)pyrene has been identified as being highly carcinogenic. The US Environmental Protection Agency (EPA) has promulgated 16 unsubstituted PAHs (EPA-PAH) as priority pollutants. Thus, exposure assessments of PAHs in the developing world are important. The scope of this review will be to give an overview of PAH concentrations in various environmental samples and to discuss the advantages and limitations of applying these parameters in the assessment of environmental risks in ecosystems and human health. As it well known, there is an increasing trend to use the behavior of pollutants (i.e. bioaccumulation) as well as pollution-induced biological and biochemical effects on human organisms to evaluate or predict the impact of chemicals on ecosystems. Emphasis in this review will, therefore, be placed on the use of bioaccumulation and biomarker responses in air, soil, water and food, as monitoring tools for the assessment of the risks and hazards of PAH concentrations for the ecosystem, as well as on its limitations.

Use of headspace solid-phase microextraction coupled to liquid chromatography for the analysis of polycyclic aromatic hydrocarbons in tea infusions

A sensitive and solvent-free procedure for the determination of 11 polycyclic aromatic hydrocarbons in tea infusions using headspace solid-phase microextraction coupled to liquid chromatography with fluorimetric detection is described. A medium polarity polydimethylsiloxane-divinylbenzene 60 microm fiber was found to be suitable for extraction at 90 degrees C and with an extraction time of 60 min under continuous stirring. Desorption was carried out using the static mode for 5 min. Under the optimized conditions, when 1.75 g of tea sample were extracted with boiling water, the precision ranged from 4 to 16% (RSD) and detection limits were between 4 and 145 ngL(-1), depending on the compound. The reliability of the procedure was corroborated by means of GC-MS. The results obtained for a standard reference material were within the range indicated by the supplier.

Simultaneous determination of 102 pesticide residues in Chinese teas by gas chromatography-mass spectrometry

An efficient and sensitive method for simultaneous determination of 102 pesticide residues in teas has been established and validated. The multi-residue analysis of the pesticides in teas involved extraction with acetone-ethyl acetate-hexane, clean-up using gel permeation chromatography (GPC) and solid-phase extraction (SPE), and subsequent identification and quantification of the selected pesticides by gas chromatography-mass spectrometry (GC-MS) under retention time locked (RTL) conditions. For most of the target analytes, the optimized pretreatment processes led to no significant interference on analysis from sample matrix, and the determination of 102 compounds was achieved in about 120 min. Pesticide residues could be determined in low sub-ppb range, from 0.01 microg/mL for hexachlorobenzene to 2.5 microg/mL for propargite, with average recoveries ranging from 59.7 to 120.9% (mean 88%) and relative standard deviations (RSDs) in the range 3.0-20.8% (mean 13.7%) for all analytes across three fortification tea levels. The limits of detection (LODs) were much lower than the maximum residue levels established by the European Union (EU) legislations.

Polycyclic aromatic hydrocarbons in food samples collected in Barcelona, Spain

This study reports on the concentrations of eight polycyclic aromatic hydrocarbons (PAHs) in food samples collected in the city of Barcelona (Catalonia, Spain) from 2003 to 2004. Food samples included meat products, fish (fresh and smoked), other seafood (cephalopods, crustaceans, and bivalves), vegetable oil, and tea. Concentrations of benz[a]anthracene, benzo[b]fluoranthene, benzo[k]fluoranthene, benzo[g,h,i]perylene, benzo[alpha]pyrene, benzo[e]pyrene, dibenz[a,h]anthracene, and indeno[1,2,3-c,d]pyrene were determined by reversed-phase high-performance liquid chromatography with fluorescence detection. PAHs were detected in most tea samples (94%), which had the highest concentration of total PAHs (mean concentration of 59 microg/kg). Other food groups with a high presence of PAHs were bivalves (present in 34% of the samples; mean value of 2.7 microg/kg) and meat products (present in 13% of the samples; mean value of 1.7 microg/kg). The PAHs detected most frequently were benzo[e]pyrene and benzo[b]fluoranthene. No sample had levels above current regulation standards. Nevertheless, the frequent presence of PAHs in bivalves, tea samples, and meat products, together with the fact that dietary sources are the main exposure to these carcinogenic compounds, suggests the need for some monitoring scheme to follow up on these trends.

Factors affecting transfer of polycyclic aromatic hydrocarbons from made tea to tea infusion

Factors affecting transfer percentages of 12 polycyclic aromatic hydrocarbons (PAHs) were investigated, including tea variety, tea/water ratio (TWR, g/mL), brewing times, washed tea or unwashed tea, and covered cup or uncovered cup. It was observed that %PAH transfer varied with tea variety and increased with the decrease of TWR. The mean %PAH transfer with TWR = 1/150 was 1.12 and 1.65 times higher than that with TWR = 1/100 and 1/50, respectively. %PAH transfer reduced greatly as the brewing times increased. The mean %PAH transfer in the first brewing time occupied 51.6% of the total three mean %PAH transfers in the three brewing times. The mean %PAH transfer decreased by 30.4% after the tea had been washed immediately before brewing. Brewing the tea within uncovered cup diminished %PAH transfer by a degree of 4.31-31.7% compared to brewing the tea within a covered cup.

Tea plant uptake and translocation of polycyclic aromatic hydrocarbons from water and around air

This study, which aimed to investigate the capacity of tea plant uptake and translocation of polycyclic aromatic hydrocarbons (PAHs), was divided into two sections. One was to study tea plant root uptake of PAHs from water and translocation to leaves. The other was to research tea plant leaf uptake of PAHs from air. It was observed that tea plant roots and leaves could strongly accumulate PAHs from around the environment. The capacity of tea plant uptake and translocation of PAHs were found to be closely relative to the physical-chemical properties of PAHs. With the increase of IgK(ow) (octanol-water partition coefficient) of the PAHs, both root concentration factors and leaf concentration factors increased exponentially, while translocation factors from roots to leaves decreased exponentially.

Stir bar sorptive extraction and high-performance liquid chromatography–fluorescence detection for the determination of polycyclic aromatic hydrocarbons in Mate teas

A simple procedure based on stir bar sorptive extraction (SBSE) and high-performance liquid chromatography-fluorescence detection (HPLC-FLD) is presented for the determination of 15 polycyclic aromatic hydrocarbons (PAHs) in herbal tea prepared with Mate leaves (Ilex paraguariensis St. Hil.). The influence of methanol and salt addition to the samples, the extraction time, the desorption time and the number of desorption steps, as well as the matrix effect, were investigated. Once the SBSE method was optimised (10 mL of Mate tea, 2h extraction at room temperature followed by 15 min desorption in 160 microL of an acetonitrile (ACN)-water mixture), analytical parameters such as repeatability (< or = 10.1%), linearity (r2 > or = 0.996), limit of detection (LOD, 0.1-8.9 ng L(-1) ), limit of quantitation (LOQ, 0.3-29.7 ng L(-1) and absolute recovery (24.2-87.0%) were determined. For calibration purposes, a reference sample was firstly obtained by removing the analytes originally present in the lowest contaminated Mate tea studied (via SBSE procedure) and then spiked at 1-1200 ng L(-1)range. The proposed methodology proved to be very convenient and effective, and was successfully applied to the analysis of 11 Mate tea samples commercialised in Brazil. The results of the commercial Mate tea samples found by the SBSE approach were compared with those obtained by liquid-liquid extraction (LLE), showing good agreement.

Concentrations and health risk of polycyclic aromatic hydrocarbons in tea

Sixteen polycyclic aromatic hydrocarbons (PAHs) were simultaneously measured in 8 brands of tea and in infusions of one brand of black tea. It was observed that the total contents of the 16 PAHs (summation PAHs) in the tea samples ranged from 323 to 8800 microg/kg with the highest summation PAHs found in a black tea. PAHs (3-4 rings) were dominant in all tea samples, with a contribution of 77.7-98.7% of the summation PAHs. Infusion times from 10 to 120 min were studied during which 3.03-7.69% of the total PAHs contained in the black tea was released into the liquor. The percentages of PAHs released (RR) from the tea into the liquor were inversely proportional to the lgK(ow) of the PAHs with a mean formula of RR=261.7/lgK(ow)-41.32 and R=0.899. To analyze the potential health risk, sanitary standards of the 16 PAHs for tea leaves were calculated to be 0.1-110 mg/kg and the daily PAHs intake from the black tea was calculated to be 6.36 microg per person.

Polycyclic aromatic hydrocarbons: pollution and source analysis of a black tea

Investigations into the manufacturing process of one kind of black tea revealed that it included five steps: withering, rolling, fermentation, drying, and drying and sorting. A total of 16 polycyclic aromatic hydrocarbons (PAHs) were simultaneously measured in fresh leaves, withered leaves, rolled leaves, fermented leaves, crude black tea, and black tea sampled after each manufacturing stage and in the indoor and outdoor air of the drying house. It was observed that the total contents of the 16 PAHs (SigmaPAHs) in the crude black tea and the black tea were obviously higher than those in the tea leaves sampled after each manufacturing step before the drying stage; the air SigmaPAHs in the drying house were about 100 times higher than those outside the drying house. It can be concluded that quantities of PAHs were released into the drying house from the combustion of pine firewood during the drying stage, and then were absorbed by the tea leaves, thus resulting in the high PAH contents in the black tea.

Passive sampling and/or extraction techniques in environmental analysis: a review

The current state-of-the-art of passive sampling and/or extraction methods for long-term monitoring of pollutants in different environmental compartments is discussed in this review. Passive dosimeters that have been successfully used to monitor organic and inorganic contaminants in air, water, sediments, and soil are presented. The application of new approaches to the determination of pollutants at the sampling stage is discussed. The main milestones in the development of passive techniques for sampling and/or extraction of analytes, and in biomonitors used in environmental analysis, are summarized in this review. Passive samplers and biomonitors are compared.

Application of polyphenylmethylsiloxane coated fiber for solid-phase microextraction combined with microwave-assisted extraction for the determination of organochlorine pesticides in Chinese teas

Polyphenylmethylsiloxane (PPMS) as a novel coating for solid-phase microextraction (SPME) combined with microwave-assisted extraction (MAE) has been applied to determine the concentrations of organochlorine pesticides (OCPs) in Chinese teas. The characteristics of PPMS fiber, the extraction modes of SPME, the extraction time, temperature, and salt effects were investigated. Microwave irradiation time and power were also studied. Compared with commercial polydimethylsiloxane (PDMS) fiber and homemade sol-gel polymethylsiloxane (PMS) fiber, the novel porous sol-gel PPMS fiber exhibited high sensitivity and selectivity for OCPs compounds, higher thermal stability (to 350 degrees C) and long service life (more than 150 times). The recoveries of MAE is compared with that of ultrasonic extraction (USE), MAE-SPME-gas chromatography (GC)/electron-capture detection (ECD) methods showed better results for Chinese teas. Linear ranges of OCPs in the blank green tea was 0.1-10(3) ng/l. Detection limits of this method are below 0.081 ng/l. Recoveries of this method are between 39.05 and 94.35%. The repeatability of the technique was less than 16% relative standard deviation (R.S.D.). The tested pesticides in three Chinese teas were at the ng/g level.