Determination of phthalates in wine by headspace solid-phase microextraction followed by gas chromatography-mass spectrometry. Use of deuterated phthalates as internal standards

Method development of stir bar sportive extraction coupled with thermal desorption-gas chromatography-mass spectrometry for the analysis of phthalates in Peruvian pisco

In this work, for the first time, a stir bar sorptive extraction (SBSE) coupled with thermal desorption-gas chromatography-mass spectrometry (TD-GC-MS) was developed and validated for the determination of seven phthalates in Peruvian pisco. The phthalate compounds considered were dimethyl phthalate (DMP), diethyl phthalate (DEP), bis(2-ethylhexyl) hexahydrophthalate (BEHP), benzyl butyl phthalate (BBP), di-n-butyl phthalate (DBP), di-isodecyl phthalate (DIDP) and di-isobutyl phthalate (DIBP). The best overall analytical conditions obtained from the optimization were as follow: extraction time of 120 min, size of polydimethylsiloxane (PDMS) twister (20 mm length x 1 mm thickness), NaCl content (20 %) and sample volume (40 mL). The in-house validation of SBSE/TD-GC-MS method was performed taking into account the ISO/IEC 17,025 requirements and EURACHEM/CITAC guideline. Under optimal conditions, very low limits of detection of 1.3-0.21 µg L-1 were obtained. Furthermore, the limits of quantification ranged from 4.2-70 µg L-1, and the correlation coefficients were found to be ≥ 0.991. The method was precise, with relative standard deviations (RSD, %) for inter twister repeatability and the inter day repeatability precisions from 1.1 to 11 and from 6.2 to 15.9, respectively. The pisco samples were analysed with recoveries between 91-124.4%, and DBP, BEHP, and BBP were the most commonly found compounds in the samples. The optimized methodology was also evaluated in terms of green character, and it obtained almost the best AGREE score when it was compared with other previous methods for the analysis of phthalates in alcoholic beverages. Therefore, the SBSE/TD-GC-MS method has proved to be suitable for routine practice because it is simple, less laborious, economical, precise, accurate and green, and it would be applicable for pisco safety regulations.

A Critical Review of Analytical Methods for the Quantification of Phthalates Esters in Two Important European Food Products: Olive Oil and Wine

Phthalic acid esters (PAEs) are a class of chemicals widely used as plasticizers. These compounds, considered toxic, do not bond to the polymeric matrix of plastic and can, therefore, migrate into the surrounding environment, posing a risk to human health. The primary source of human exposure is food, which can become contaminated during cultivation, production, and packaging. Therefore, it is imperative to control and regulate this exposure. This review covers the analytical methods used for their determination in two economically significant products: olive oil and wine. Additionally, it provides a summary and analysis of information regarding the characteristics, toxicity, effects on human health, and current regulations pertaining to PAEs in food. Various approaches for the extraction, purification, and quantification of these analytes are highlighted. Solvent and sorbent-based extraction techniques are reviewed, as are the chromatographic separation and other methods currently applied in the analysis of PAEs in wines and olive oils. The analysis of these contaminants is challenging due to the complexities of the matrices and the widespread presence of PAEs in analytical laboratories, demanding the implementation of appropriate strategies.

Commercial beers: A source of phthalates and di-ethylhexyl adipate

Beer is one of the most consumed beverages worldwide. Different materials used along its production and packaging can result in human exposure to phthalates and adipates. The aim of this study was to assess simultaneously the levels of phthalates and di-ethylhexyl adipate (DEHA) in commercial beer samples (n = 66) with a method based on DLLME and detection with GC-MS/MS, and further evaluate human exposure. Six out of seven compounds studied were found in the beers analysed, with levels ranging from 1.77 to 205.40 µg/L. The most prevalent was DEHA at 205.40 µg/L, while dimethyl phthalate (DMP) was not present in any sample. Samples with 5-6 % alcohol, packed in aluminium cans and produced in an industrial environment presented the highest level of these contaminants. Despite low-risk exposure to phthalates and adipate with beer, it is important to remember the ubiquitous nature of these compounds, which can lead to cumulative exposure.

Spontaneous conversion of prenyl halides to acids: application in metal-free preparation of deuterated compounds under mild conditions

Here we reveal a simple generation of deuterium halide (DX) from common and inexpensive reagents readily available in a synthetic chemistry laboratory, i.e. prenyl-, allyl-, and propargyl halides, under mild conditions. We envisaged that in situ generation of an acid, deuterium halide, would be useful for acid-catalyzed reactions and could be employed for organocatalytic deuteration. The present work reports a metal-free method for deuterium labeling covering a broad range of substrate including phenolic compounds (i.e. flavonoids and stilbenes), indoles, pyrroles, carbonyl compounds, and steroids. This method was also applied for commonly used drugs such as loxoprofen, haloperidol, stanolone, progesterone, androstenedione, donepezil, ketorolac, adrenosterone, cortisone, pregnenolone, and dexamethasone. A gram-scale chromatography-free synthesis of some deuterated compounds is demonstrated in this work. This work provides a simple, clean and by-product-free, site-selective deuteration, and the deuterated products are obtained without chromatographic separation. When applying these initiators for other acid-catalyzed reactions, the deuterium isotope effects of DX may provide products which are different from those obtained from reactions using common acids. Although the mechanism of the spontaneous transformation of prenyl halides to acid is unclear, this overlooked chemistry may be useful for many reactions.

Critical Review on the Presence of Phthalates in Food and Evidence of Their Biological Impact

Phthalates are a huge class of chemicals with a wide spectrum of industrial uses, from the manufacture of plastics to food contact applications, children's toys, and medical devices. People and animals can be exposed through different routes (i.e., ingestion, inhalation, dermal, or iatrogenic exposure), as these compounds can be easily released from plastics to water, food, soil, air, making them ubiquitous environmental contaminants. In the last decades, phthalates and their metabolites have proven to be of concern, particularly in products for pregnant women or children. Moreover, many authors reported high concentrations of phthalates in soft drinks, mineral waters, wine, oil, ready-to-eat meals, and other products, as a possible consequence of their accumulation along the food production chain and their accidental release from packaging materials. However, due to their different physical and chemical properties, phthalates do not have the same human and environmental impacts and their association to several human diseases is still under debate. In this review we provide an overview of phthalate toxicity, pointing out the health and legal issues related to their occurrence in several types of food and beverage.

Fabrication of UMCM-1 based monolithic and hollow fiber - Metal-organic framework deep eutectic solvents/molecularly imprinted polymers and their use in solid phase microextraction of phthalate esters in yogurt, water and edible oil by GC-FID

In this study, for the first time, hollow fiber and monolithic fiber were fabricated based on metal-organic framework deep eutectic solvents/molecularly imprinted polymers (MOF- DES/MIPs) and were used for microextraction of phthalate esters under termed hollow fiber liquid membrane-protected solid-phase microextraction (HFLMP-SPME) followed by gas chromatography- flame ionization detection. Several parameters influencing extraction recoveries of phthalate esters including adsorption and desorption parameters were investigated and optimized using fabricated MOF- DES/MIPs monolithic fiber. Under optimal conditions, detection limits (S/N = 3) of the method were in a range of 0.008-0.03 µg L^-1 and limits of quantification (S/N = 10) were between 0.028 and 0.12 µg L^-1. RSD (%) for intra-day and inter-day precisions were between 2.4-4.7% and 2.6-3.4%, respectively. Subsequently, this procedure was successfully applied with satisfactory results in the determination of phthalate esters in yogurt, water, and soybean oil samples. The R (%) ranged from 95.5 to 100.0% in different samples.

A green and simple procedure based on deep eutectic solvents for the extraction of phthalates from beverages

In this work, a green, inexpensive, simple and fast deep eutectic solvent (DES)-based dispersive liquid-liquid microextraction was evaluated, for the first time, for the extraction of phthalates (i.e. benzylbutyl phthalate, diisobutyl phthalate, diisopentyl phthalate, di-n-pentyl phthalate, di-(2-ethylhexyl) phthalate, di-n-octyl phthalate, diisononyl phthalate, diisodecyl phthalate) from different beverages. Separation and determination were achieved by high performance liquid chromatography-diode-array detection while confirmation was carried out by tandem mass spectrometry. The main factors affecting the extraction such as type and volume of DES and emulsifier, pH and ionic strength, were optimised. Choline chloride:phenol-based DES showed the best results. The methodology was validated for tea, apple-based beverage and pineapple juice. Recovery values ranged from 84 to 120% with relative standard deviation values lower than 11%. Limits of detection of the method were in the range 5.1-14.2 µg L^-1 for tea, 5.3-17.8 µg L^-1 for apple beverages and 5.9-15.6 µg L^-1 for pineapple juices.

Facts about phthalate toxicity in humans and their occurrence in alcoholic beverages

Phthalates are esters of phthalic acid and aliphatic alcohol added to plastic to improve its softness, flexibility, and extensibility. They easily migrate from plastic products into the environment because of their physical and chemical properties. This review summarises their characteristics, distribution in the environment, monitoring, use, toxic effects on human health, regulatory limits in different matrices and products, and tolerable daily intake. The studies we have reviewed suggest that phthalates have a potential to affect reproduction and development in humans. Due to the inconsistent data, further studies are needed and, in the meantime, precautionary policies must be implemented. Here we draw attention to the methods of determining phthalate levels in alcoholic beverages and reported levels in plum spirits produced in Croatia. Legally produced and moderately consumed plum spirits do not seem to increase the risk of phthalate toxicity for human health. We conclude with recommendations for the effective monitoring of phthalate exposure in humans and for the implementation of alternative materials in alcohol production.

High-Throughput and Low-Cost Analysis of Trace Volatile Phthalates in Seafood by Online Coupling of Monolithic Capillary Adsorbent with GC-MS

A simple, sensitive, and high-throughput method was developed for the determination of six volatile phthalate esters-dimethyl phthalate (DMP), diethyl phthalate (DEP), dibutyl phthalate (DBP), benzylbutyl phthalate (BBP), di(2-ethylhexyl) phthalate (DEHP), and di-n-octyl phthalate (DnOP)-in seafood samples by using monolith adsorbent in a capillary coupled to a gas chromatography-mass spectrometry (GC-MS) system. The freeze-dried samples were subjected to an ultrasonication with hexane, followed by vortex mixing. The liquid extract was quantitatively determined by a direct application to an online silica monolith capillary adsorbent coupled with a gas chromatograph with mass spectrometric detection. Method validation in seafood matrix gave recoveries of 72.8-85.4% and a detection limit of 6.8-10.0 ng g(-1) for bivalve samples. Reusability of the monolith capillary for trapping coextracted matrix was up to six times, allowing high-throughput analysis at the parts per billion level. When compared with the Food and Environment Research Agency (FERA) method, no significant difference in the result was observed, confirming the method was valid and applicable for the routine analysis of phthalates in seafood samples for food and environmental laboratories.

Screening of phthalate esters in 47 branded perfumes

In the last few years, the use of phthalates in perfumes has gained attention because these chemicals are sometimes added intentionally as a solvent and a fixative. Five phthalate esters, dimethyl phthalate (DMP), diethyl phthalate (DEP), dibutyl phthalate (DBP), benzyl butyl phthalate (BBP), and diethyl hexyl phthalate (DEHP), were measured in 47 branded perfumes using headspace solid phase microextraction (SPME) followed by gas chromatography-mass spectrometry (GC-MS). The results revealed considerable amounts of phthalate in all 47 brands with detection frequencies > limit of quantitation in the following order: DEP (47/47) > DMP (47/47) > BBP (47/47) > DEHP (46/47) > DBP (23/45). Of the 47 brands, 68.1, 72.3, 85.1, 36.2, and 6.7 % had DEP, DMP, BBP, DEHP, and DBP levels, respectively, above their reported threshold limits. Of these phthalates, DEP was found to have the highest mean value (1621.625 ppm) and a maximum of 23,649.247 ppm. The use of DEP in the perfume industry is not restricted because it does not pose any known health risks for humans. DMP had the second highest level detected in the perfumes, with a mean value of 30.202 ppm and a maximum of 405.235 ppm. Although DMP may have some uses in cosmetics, it is not as commonly used as DEP, and again, there are no restrictions on its use. The levels of BBP were also high, with a mean value of 8.446 ppm and a maximum of 186.770 ppm. Although the EU banned the use of BBP in cosmetics, 27 of the tested perfumes had BBP levels above the threshold limit of 0.1 ppm. The mean value of DEHP found in this study was 5.962 ppm, and a maximum was 147.536 ppm. In spite of its prohibition by the EU, 7/28 perfumes manufactured in European countries had DEHP levels above the threshold limit of 1 ppm. The DBP levels were generally low, with a mean value of 0.0305 ppm and a maximum value of 0.594 ppm. The EU banned the use of DBP in cosmetics; however, we found three brands that were above the threshold limit of 0.1 ppm, and all were manufactured in European countries. The results of this study are alarming and definitely need to be brought to the attention of the public and health regulators. Although some phthalate compounds are still used in cosmetics, many scientists and environmental activists have argued that phthalates are endocrine-disrupting chemicals that have not been yet proven to be safe for any use, including cosmetics. Phthalates may also have different degrees of estrogenic modes of action. Furthermore, we should not dismiss the widespread use of phthalates in everyday products and exposure to these chemicals from sources such as food, medications, and other personal care products.

Extraction and GC-MS analysis of phthalate esters in food matrices: a review

According to the Scopus database, using “phthalate” and “GC” as keywords, 758 papers have been found between 1990 and 2014, showing strong and increasing interest in this class of compounds from the scientific community.

Determination of phthalate esters in cleaning and personal care products by dispersive liquid-liquid microextraction and liquid chromatography-tandem mass spectrometry

Phthalic acid esters (PEs) were preconcentrated from cleaning products, detergents and cosmetics using ultrasound assisted extraction (UAE) in the presence of acetonitrile, and then submitted to dispersive liquid-liquid microextraction (DLLME). For DLLME, 3mL of acetonitrile extract, 150μL carbon tetrachloride and 10mL aqueous solution were used. The enriched organic phase was evaporated, reconstituted with 25μL acetonitrile and injected into a liquid chromatograph with a mobile phase (acetonitrile:10mM ammonium acetate, pH 4) under gradient elution. Detection was carried out using both diode-array (DAD) and electrospray-ion trap-tandem mass spectrometry (ESI-IT-MS/MS) in the multiple reaction monitoring mode (MRM) of the positive fragment ions. Quantification was carried out using matrix-matched standards. Detection limits were in the range 0.04-0.45ngmL(-1) for the six PEs considered. The recoveries obtained were in the 84-124% range, with RSDs lower than 10%. Thirty three different cleaning products were analyzed. The most frequently found compound was diethyl phthalate.

Analysis of phthalates in wine using liquid chromatography tandem mass spectrometry combined with a hold-back column: Chromatographic strategy to avoid the influence of pre-existing phthalate contamination in a liquid chromatography system

This paper describes the development and application of a novel method for the analysis of phthalates in wine using HPLC-MS/MS combined with a hold-back column. Phthalates are ubiquitous contaminants in the environment and can be widely found in laboratory materials and equipment. A HPLC system is no exception and can be the source of contamination affecting the accuracy and precision of analytical results. The new method successfully separates phthalates from the different sources, a wine sample and HPLC system by a simple technique using an additional HPLC column (a hold-back column) placed upstream of the injection valve. The hold-back column effectively retains the HPLC-derived contaminants during column equilibrium time and delays their elution times from an analytical column. Consequently, a phthalate from a wine sample can be baseline separated as it elutes sufficiently earlier than the same phthalate from the HPLC system. HPLC-MS/MS analysis combined with the hold-back column demonstrated virtually no influence of the HPLC contaminants on the quantification of phthalates present in wine. Together with a simple and rapid sample preparation and the use of labeled internal standards, the method was confirmed to be robust and reliable to determine concentrations of phthalates in wine. Quantification limits were within the range of 1.6-9.8μgL^-1 for dimethyl, diethyl, dibutyl, benzylbutyl, bis(2-ethylhexyl) and dioctyl phthalates, and 7.5-26.6μgL^-1 for multiple isomeric phthalates, di-iso-nonyl and di-iso-dodecyl phthalates.

Determination of Phthalate Plasticisers in Palm Oil Using Online Solid Phase Extraction-Liquid Chromatography (SPE-LC)

Contamination of phthalates plasticisers to food has raised concern as some of the phthalates are suspected to be endocrine disruptors. The phthalates have high affinity with oily environment and analysing these chemicals in such matrices is difficult because of the trace amount of the analyte and interference from matrix. An online solid phase extraction (SPE) technique using a large volume (3.5 mL) injection was developed for the analysis of 6 common plasticisers in palm oil. A simple sample preparation involving alumina as a fat retainer and methanol : acetonitrile (1 : 1) as the extraction solvent was performed prior to the usage of online SPE-LC system. This system consists of two columns, C16for the solid phase extraction (SPE) and C18as the analytical column, and a photo diode array detector. The calibration curves were linear from 5 to 1000 μg L−1, with correlation coefficients above 0.99. The instrumental limit of detection was 3 μg L−1and satisfactory recovery was obtained. A screening on a few samples in the retail market revealed the presence of dibutyl phthalate (DBP) and butylbenzylphthalate (BBP) in the palm oil, with concentration less than 1 mg L−1.

Determination of alkylphenols and phthalate esters in vegetables and migration studies from their packages by means of stir bar sorptive extraction coupled to gas chromatography-mass spectrometry

This paper describes a method for the determination of three alkylphenols (APs), 4-tert-octylphenol (tOP), 4-n-octylphenol (OP) and 4-nonylphenol (NP), and six phthalate esters (PEs), dimethylphthalate (DMP), diethylphthalate (DEP), di-n-butylphthalate (DBP), n-butylbenzylphthalate (BBP), di-2-ethylhexylphthalate (DEHP) and di-n-octylphthalate (DOP), in vegetables using stir bar sorptive extraction (SBSE) in combination with thermal desorption-gas chromatography-mass spectrometry (TD-GC-MS). Ultrasonic radiation was used to extract the analytes from the solid food matrix, and the extract obtained was preconcentrated by SBSE. The different parameters affecting both stages were carefully optimized. The method was applied to analyze commercial vegetables, in the form of plastic packed salads and canned greens, as well as the corresponding filling liquids of the canned food. Quantification of the samples was carried out against aqueous standards using an internal standard (anthracene). The analysis of a 2 g vegetable sample provided detection limits between 12.7 and 105.8 pg g⁻¹ for OP and DEHP, respectively. Migration studies from the plastic packages of the vegetables samples analyzed were carried out. DEP, DBP and DEHP were found to have migrated from the bags to the simulant and the same compounds were quantified in lettuce, corn salad, arugula, parsley and chard, at concentration levels in the 8-51 ng g⁻¹ range. However, OP and NP were found in only two vegetable samples and one filling liquid, but neither was detected in any package. The proposed method provided recoveries of 83-118%.

Determination of phthalate esters in physiological saline solution by monolithic silica spin column extraction method

Monolithic silica spin column extraction (MonoSpin-SPE) was developed as a simple, sensitive, and eco-friendly pretreatment method which combined with ultra-fast liquid chromatography-mass spectrometry (UFLC-MS) to determine the levels of six phthalate esters, dimethyl-(DMP), diethyl-(DEP), dipropyl- [DPrP], butyl-benzyl-(BBP), dicyclohexyl(DcHP), and di- n-octyl-(DOP) phthalate in physiological saline samples. Under optimized experimental conditions, the method was linear in the following ranges: 0.2- 50 μ/L for DMP, DEP, DPrP, DcHP and DOP; 5 – 100 μ/L for BBP. The correlation coefficients (R²) were in the range of O. 9951 – O. 9995 for all the analytes and the limits of detection (LODs) and limits of quantification (LOQs) were in the ranges of 0.02 – 0.9 μ/L and 0.08 – 2.7 μ/L, respectively. The pretreatment process showed good reproducibility with inter-day and intra-day relative standard deviations (RSDs) below 8.5% and 11.2%, respectively. This method was used to determine the levels of six phthalate esters in physiological saline samples and the recoveries ranged from 71.2% to 107. 3%. DMP and DEP were found in actual physical saline samples (brand A and brand B).

Determination of phthalate esters in cow milk samples using dispersive liquid-liquid microextraction coupled with gas chromatography followed by flame ionization and mass spectrometric detection

A simple and economic method for the analysis of phthalate esters, dimethyl phthalate, diethyl phthalate, di-iso-butyl phthalate, di-n-butyl phthalate, and di-2-ethylhexyl phthalate in cow milk samples by means of gas chromatography-flame ionization detection and gas chromatography-mass spectrometry has been developed. In this work, NaCl and ACN were added to 5 mL of the milk sample as the salting out agent and extraction solvent, respectively. After manual shaking, the mixture was centrifuged. In the presence of NaCl, a two-phase system was formed: upper phase - acetonitrile containing phthalate esters -and lower phase - aqueous phase containing soluble compounds and the precipitated proteins. After the extraction of phthalate esters from milk, a portion of supernatant phase (acetonitrile) was removed, mixed with 1,2-dibromoethane at microliter level and injected by syringe into NaCl solution. After the extraction of the selected phthalate esters into 1,2-dibromoethane, phase separation was performed by centrifugation and the enriched analytes in the sedimented phase were determined by gas chromatography-flame ionization detection and gas chromatography-mass spectrometry. Under the optimum extraction conditions, low limits of detection and quantification between 1.5-3 and 2.5-11 ng/mL, respectively was observed. Enrichment factors were in the range of 397-499. The relative standard deviations for the extraction of 100 ng/mL of each phthalate ester were in the range of 3-4% (n = 6). Finally, some milk samples were successfully analyzed using the proposed method and two analytes, di-n-butyl phthalate and di-2-ethylhyxel phthalate, were determined in them in nanogram per milliliter level.

Determination of phthalates in fruit jellies by dispersive SPE coupled with HPLC-MS

In this study, a simple, rapid and sensitive method for the determination of five phthalates including dimethyl phthalate, diethyl phthalate, dipropyl phthalate, benzyl butyl phthalate, and dicyclohexyl phthalate in fruit jellies by LC coupled with MS has been developed. Samples were pretreated by a dispersive SPE method, termed QuEChERS, which is an acronym for quick, easy, cheap, effective, rugged, and safe. The standard calibration curves were linear for all the analytes over the concentration range of 10-250 ng/mL, and the correlation coefficients ranged from 0.9976 to 0.9991. The LODs and LOQs were in the ranges of 0.09-3.68 ng/mL and 0.28-11.25 ng/mL, respectively. The accuracy of this method was evaluated by measuring the recovery from spiked samples. The recoveries of all five phthalates from samples spiked at three different concentrations (0.01, 0.03, and 0.05 mg/kg), were in the ranges of 83.5-103.9%, 86.7-95.8%, and 87.1-95.2%, respectively. The RSD values for the samples spiked at 0.01, 0.03, and 0.05 mg/kg ranged from 2.0-7.6%, 1.4-6.4%, and 1.2-3.8%, respectively. The method has been used for the analysis of real samples and BBP and DEP were found in real samples.

Detection of diethyl phthalate in perfumes by extractive electrospray ionization mass spectrometry

Recent findings suggest that long-term exposure to diethyl phthalate (DEP), one of the widely used phthalate esters, can lead to serious health problems. Most perfumes contain non-negligible amounts of DEP. Rapid and sensitive detection of DEP in perfumes is thus of increasing importance. A novel procedure based on extractive electrospray ionization mass spectrometry (EESI-MS) has been developed for fast detection and identification of DEP in perfumes without the need for any sample pretreatment. The limit of determination for DEP in perfume was less than 100 ppb using tandem mass spectrometry on a commercial quadrupole time-of-flight mass spectrometer. The dynamic range of this method was about 4 orders of magnitude. A single sample analysis was completed within a few seconds, providing a rapid way to obtain semiquantitative information on the DEP content in perfumes. This study shows that both volatile and nonvolatile analytes (e.g., amino acids) in liquids can be directly sampled by neutral desorption, providing a convenient way for high-throughput screening of target compounds using EESI-MS.

Dispersive liquid-liquid microextraction method based on solidification of floating organic drop combined with gas chromatography with electron-capture or mass spectrometry detection

A simple dispersive liquid-liquid microextraction (DLLME) method based on solidification of a floating organic drop (DLLME-SFO) technique combined with gas chromatography/electron-capture detection (GC/ECD) or gas chromatography/mass spectrometry (GC/MS) has been developed. The proposed method is simple, low in cost, and of high precision. It overcomes the most important problem in DLLME, the high-toxic solvent used. Halogenated organic compounds (HOCs) in water samples were determined as the model compounds. The parameters optimized for the DLLME-SFO technique were as follows: A mixture of 0.5 mL acetone, containing 10 microL 2-dodecanol (2-DD-OH), was rapidly injected by syringe into the 5 mL water sample. After centrifugation, the fine 2-DD-OH droplets (8+/-0.5 microL) were floated at the top of the screwcap test tube. The test tube was then cooled in an ice bath. After 5 min the 2-DD-OH solvent had solidified and was then transferred into a conical vial; it melted quickly at room temperature and 3 microL (for GC/ECD) or 2 microL (for GC/MS) of it was injected into a gas chromatograph for analysis. The limit of detection (LOD) for this technique was 0.005-0.05microgL(-1) for GC/ECD and was 0.005-0.047 microgL(-1) for GC/MS, respectively. The linear range of the calibration curve of DLLME-SFO was from 0.01 to 500 microgL(-1) with a coefficient of estimation (r2)>0.996 for GC/ECD and was from 0.02 to 500 microgL(-1) with a coefficient of estimation (r2)>0.996 for GC/MS.