Screening method for phthalate esters in water using liquid-phase microextraction based on the solidification of a floating organic microdrop combined with gas chromatography-mass spectrometry

A simple and efficient liquid-phase microextraction (LPME) technique was developed using directly suspended organic microdrop coupled with gas chromatography–mass spectrometry (GC–MS), for the extraction and the determination of phthalate esters (dimethyl phthalate, diethyl phthalate, diallyl phthalate, di-n-butyl phthalate (DnBP), benzyl butyl phthalate (BBP), dicyclohexyl phthalate and di-2-ethylhexyl phthalate (DEHP)) in water samples. Microextraction efficiency factors, such as nature and volume of the organic solvent, temperature, salt effect, stirring rate and the extraction time were investigated and optimized. Under the optimized extraction conditions (extraction solvent: 1-dodecanol; extraction temperature: 60 °C; microdrop volume: 7 μL; stirring rate: 750 rpm, without salt addition and extraction time: 25 min), figures of merit of the proposed method were evaluated. The values of the detection limit were in the range of 0.02–0.05 μg L⁻¹, while the R.S.D.% value for the analysis of 5.0 μg L⁻¹ of the analytes was below 7.7% (n = 4). A good linearity (r² ≥ 0.9940) and a broad linear range (0.05–100 μg L⁻¹) were obtained. The method exhibited enrichment factor values ranging from 307 to 412. Finally, the designed method was successfully applied for the preconcentration and determination of the studied phthalate esters in different real water samples and satisfactory results were attained.     

Phthalates determination in pharmaceutical formulae used in parenteral nutrition by LC-ES-MS: importance in public health

A method for determining a group of phthalate esters in pharmaceutical formulae used in parenteral nutrition samples (with and without vitamins) has been developed. The phthalic acid esters (PAEs) studied were dimethyl phthalate, diethyl phthalate, butyl benzyl phthalate, dibutyl phthalate, di-(2-ethylhexyl) phthalate, and dioctyl phthalate. This group of phthalates was determined by high performance liquid chromatography (HPLC)–electrospray ionization–mass spectrometry, working in positive ion mode. The phthalates analyzed were extracted from the sample using hexane and sodium hydroxide. The hexane was then evaporated, and the compounds were redissolved in acetonitrile. The compounds were separated by HPLC working in gradient mode with acetonitrile-ultrapure water starting from 5% to 75% acetonitrile in 5 min, followed by isocratic elution for 27 min. Standard calibration curves were linear for all the analytes over the concentration range 10–250 μg L⁻¹. The method was precise (with RSD from 3.3% to 12.9%) and sensitive. The proposed analytical method has been applied to the analysis of these compounds in different pharmaceutical formulae (with different compositions) for parenteral nutrition samples in order to check the presence of phthalates and determine their concentration.     

Investigation of feasibility of bamboo charcoal as solid-phase extraction adsorbent for the enrichment and determination of four phthalate esters in environmental water samples

This paper demonstrates, for the first time, that adsorptive potential of bamboo charcoal for solid-phase extraction of phthalate esters was investigated. The four phthalate esters, dimethyl phthalate (DMP), diethyl phthalate (DEP), butyl benzyl phthalate (BBP) and di-n-butyl phthalate (DBP), are quantitatively adsorbed on a bamboo charcoal packed cartridge, then the analytes retained on the cartridge are quantitatively desorbed with optimum amounts of acetone. Finally, the analytes in the eluant acetone are determined by high-performance liquid chromatography-ultraviolet detectior. Important parameters influencing the extraction efficiency, such as eluant and its volume, flow rate of sample, sample volume, pH, the amount of adsorbent and ionic strength were investigated and optimized in detail. Under the optimum conditions, the limits of detection were 0.35-0.43 microg/L for four phthalate esters. The proposed method has been applied to the analysis of rainwater and tap water samples. And satisfactory spiked recoveries were obtained in the range of 75.0-114.2%. All the results indicated that the bamboo charcoal has great potential as a novel adsorbent material for the enrichment and determination of phthalate esters in real environmental water samples.     

Direct determination of trace phthalate esters in alcoholic spirits by spray‐inlet microwave plasma torch ionization tandem mass spectrometry

A direct analytical method based on spray‐inlet microwave plasma torch tandem mass spectrometry was applied to simultaneously determine 4 phthalate esters (PAEs), namely, benzyl butyl phthalate, diethyl phthalate, dipentyl phthalate, and dodecyl phthalate with extremely high sensitivity in spirits without sample treatment. Among the 4 brands of spirit products, 3 kinds of PAE compounds were directly determined at very low concentrations from 1.30 to 114 ng·g⁻¹. Compared with other online and off‐line methods, the spray‐inlet microwave plasma torch tandem mass spectrometry technique is extremely simple, rapid, sensitive, and high efficient, providing an ideal screening tool for PAEs in spirits.     

Magnetic nanoporous carbon as an adsorbent for the extraction of phthalate esters in environmental water and aloe juice samples

In this work, magnetic nanoporous carbon with high surface area and ordered structure was synthesized using cheap commercial silica gel as template and sucrose as the carbon source. The prepared magnetic nanoporous carbon was firstly used as an adsorbent for the extraction of phthalate esters, including diethyl phthalate, diallyl phthalate, and di‐n‐propyl‐phthalate, from lake water and aloe juice samples. Several parameters that could affect the extraction efficiency were optimized. Under the optimum conditions, the limit of detection of the method (S/N = 3) was 0.10 ng/mL for water sample and 0.20 ng/mL for aloe juice sample. The linearity was observed over the concentration range of 0.50–150.0 and 1.0–200.0 ng/mL for water and aloe juice samples, respectively. The results showed that the magnetic nanoporous carbon has a high adsorptive capability toward the target phthalate esters in water and aloe juice samples.     

Ultrasound-assisted Low Density Solvent Based Dispersive Liquid-liquid Microextraction for Determination of Phthalate Esters in Bottled Water Samples

A technique of ultrasound-assisted low density solvent based dispersive liquid-liquid microextraction was developed for the determination of four phthalate esters, including dimethyl phthalate(DMP), diethyl phthalate(DEP), di-n-butyl phthalate(DnBP) and di(2-ethylhexyl) phthalate(DEHP) in bottled water samples. A low density solvent, toluene, was selected as extraction solvent. In the extraction process, a mixture of 15 μL of toluene(extraction solvent) and 100 μL of methanol(disperser solvent) was rapidly injected into 1.0 mL of water samples. A cloudy solution was formed after ultrasounded for 5 min, and then centrifuged at 5000 r/min for 5 min. The enriched analytes in the floating phase were determined by means of gas chromatograph. Under the optimum conditions, the enrichment factors were found to be in a range of 29-67, and the recoveries were ranged from 81.2% to 103.9%. The limits of the detection were in a range of 3.8-5.6 μg/L. The proposed method was applied to the extraction and determination of phthalate esters in bottled water samples, and the concentrations of phthalate esters found in the water samples were below the allowable levels.     

Extraction of phthalate esters from water and beverages using a graphene-based magnetic nanocomposite prior to their determination by HPLC

We have developed a highly sensitive microextraction method for the preconcentration of some phthalate esters such as diethyl phthalate, di-n-propylphthalate, di-n-butyl-phthalate, dicyclohexyl-phthalate, and diethyl-hexyl phthalate prior to their determination by HPLC. It is based on a magnetic graphene nanocomposite as an effective adsorbent. The effects of the amount of the extractant composite employed, extraction time, pH values, salt concentration and desorption conditions were investigated. Under the optimum conditions, the enrichment factors range from 1574 to 2880. Response is linear in the concentration range from 0.1 to 50?ng?mL^?1. The limits of detection (at S/N?=?3) were between 0.01 and 0.04?ng?mL^?1. The method was successfully applied to the determination of five phthalate esters in water and beverage samples.

GC-EI-MS内标法分析鱼肉中邻苯二甲酸酯

鱼肉样品以Florisil硅藻土层析柱净化后, 经气相色谱-电子轰击离子源-质谱法(GC-EI-MS)分析其中8种邻苯二甲酸酯(PAEs)含量: 邻苯二甲酸二乙酯(DEP)、邻苯二甲酸二丙酯(DPrP)、邻苯二甲酸二丁酯(DBP)、邻苯二甲酸丁基苄基酯(BBP)、邻苯二甲酸二戊酯(DPeP)、邻苯二甲酸二环己基酯(DCHP)、邻苯二甲酸二己酯(DHP)、邻苯二甲酸二(2-乙基己基)酯(DEHP). 比较了外标和内标法定量, 并确定苯甲酸苄基酯为内标物; 优化了提取剂、吸附剂和洗脱剂的种类, 以及洗脱体积等样品前处理方法; 尤其对分析空白的控制问题进行了详细讨论; 准确分析了5种鱼样品中此类物质含量. 该方法的线性范围为50.0～800 μg•L^－1, 相关系数(R)大于0.99986, 相对标准偏差(Relative standard deviation, RSD)均小于12.7%, 检测限(Limit of detection, LOD)低于3.66 μg•L^－1, 样品的加标回收率为74.0%～113%. 其线性范围、相关系数、准确度、精密度和LOD等指标均满足鱼肉中多种PAEs同时分析的要求.     

Determination of phthalate esters from environmental water samples by micro‐solid‐phase extraction using TiO2 nanotube arrays before high‐performance liquid chromatography

We describe a highly sensitive micro‐solid‐phase extraction method for the pre‐concentration of six phthalate esters utilizing a TiO₂ nanotube array coupled to high‐performance liquid chromatography with a variable‐wavelength ultraviolet visible detector. The selected phthalate esters included dimethyl phthalate, diethyl phthalate, dibutyl phthalate, butyl benzyl phthalate, bis(2‐ethylhexyl)phthalate and dioctyl phthalate. The factors that would affect the enrichment, such as desorption solvent, sample pH, salting‐out effect, extraction time and desorption time, were optimized. Under the optimum conditions, the linear range of the proposed method was 0.3–200 μg/L. The limits of detection were 0.04–0.2 μg/L (S/N = 3). The proposed method was successfully applied to the determination of six phthalate esters in water samples and satisfied spiked recoveries were achieved. These results indicated that the proposed method was appropriate for the determination of trace phthalate esters in environmental water samples.     

Microwave‐assisted preparation of poly(ionic liquids)‐modified polystyrene magnetic nanospheres for phthalate esters extraction from beverages

The fabrication of novel poly(ionic liquids)‐modified polystyrene (PSt) magnetic nanospheres (PILs‐PMNPs) by a one‐pot miniemulsion copolymerization reaction was achieved through an efficient microwave‐assisted synthesis method. The morphology, structure, and magnetic behavior of the as‐prepared magnetic materials were characterized by using transmission electron microscopy, vibrating sample magnetometry, etc. The magnetic materials were utilized as sorbents for the extraction of phthalate esters (PAEs) from beverage samples followed by high‐performance ultrafast liquid chromatography analysis. Significant extraction parameters that could affect the extraction efficiencies were investigated particularly. Under optimum conditions, good linearity was obtained in the concentration range of 0.5–50 (dimethyl phthalate), 0.3–50 (diethyl phthalate), 0.2–50 (butyl benzyl phthalate), and 0.4–50 μg/L (di‐n‐butyl phthalate), with correlation coefficients R ² > 0.9989. Limits of detection were in the range 125–350 pg. The proposed method was successfully applied to determine PAEs from beverage samples with satisfactory recovery ranging from 77.8 to 102.1% and relative standard deviations ranging from 3.7 to 8.4%. Comparisons of extraction efficiency with PSt‐modified MNPs as sorbents were performed. The results demonstrated that PILs‐PMNPs possessed an excellent adsorption capability toward the trace PAE analytes.     

Micro-determination of total phthalate esters in biological samples by gas-liquid chromatography.

A method was investigated in which all of the phthalate esters in biological samples were determined as phthalic acid by gas-liquid chromatography. The method is based on the separation of phthalate esters from the sample with n-hexane, saponification of the esters with an alkaline ethanolic solution to give phthalic acid, purification of the acid by extraction with diethyl ether and column chromatography using silica gel, and conversion of the acid into bis(2,2,2-trifluoroethyl) phthalate with a 2,2,2-trifluoroethanol solution containing boron trifluoride. The derivative obtained is highly sensitive to an electron-capture detector, giving a sensitivity of 0.1 pg. Biological samples fortified with di(2-ethylhexyl) phthalate at levels of 5-100 ppb were analyzed, with recoveries of 70-100%.     

Determination of phthalate esters in soil by microemulsion electrokinetic chromatography coupled with accelerated solvent extraction

A novel method using microemulsion electrokinetic chromatography combining accelerated solvent extraction was developed for quantitative analysis of six phthalate esters (PAEs) including dimethyl phthalate, diethyl phthalate, dibutyl phthalate, benzyl butyl phthalate, bis(2-ethylhexyl) phthalate, as well as dioctyl phthalate. The effect of each individual component within the microemulsions, i.e. oil phase, surfactant and co-surfactant on resolution of the analytes was systematically studied. Baseline separation of six PAEs was achieved within 26?min by using the microemulsion buffer containing a 60?mmol/L borate buffer at pH 9.0, 0.5% v/v n-octane as oil droplets, 100?mmol/L sodium cholate as surfactant and 5.0% v/v 1-butanol as co-surfactant. The purposed accelerated solvent extraction-microemulsion electrokinetic chromatography method was successfully applied to the determination of trace amount of PAEs in soil samples collected from three different fields in areas of Fujian Province and the contents of dimethyl phthalate, diethyl phthalate, dibutyl phthalate, benzyl butyl phthalate, bis(2-ethylhexyl) phthalate and dioctyl phthalate were 0.63-0.68, 0.32-0.63, 2.53-3.96, 0-1.75, 7.32-11.7 and 0-3.46mg/kg, respectively. It was validated that the results were consistent with those obtained by GC-MS method.     

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.     

Chromatographic determination of phthalic acid esters as an indicator of adulterated cognacs and cognac spirits

Based on the study performed, a conclusion was drawn that a system of procedures should be introduced into the practice of arbitration laboratories in order to identify the authenticity of cognacs and cognac spirits. These procedures were exemplified in the identification of diethyl phthalate in cognacs. Factors responsible for the falsely positive detection of diethyl phthalate in cognacs and cognac spirits were revealed. A substance that has a retention time equal to that of diethyl phthalate was identified as monoethyl succinate. As an example, recommendations were given for revealing adulterated cognac samples upon the detection of phthalic acid esters in them (including diethyl phthalate, which is a marker of denaturation). Sources of the contamination of test samples with diethyl phthalate were identified; an algorithm was developed for distinguishing between diethyl phthalate as an impurity component and diethyl phthalate added to an alcohol as a denaturation marker.     

Factors affecting the accuracy of the determination of diethyl phthalate in vodka, ethanol, and samples of illegal alcoholic products

Samples of illegally produced strong alcoholic beverages from the cities of Kyzyl and Stavropol were studied using gas chromatography and gas chromatography-mass spectrometry. It was found that all of the samples were prepared from high-purity food or hydrolysis ethanol (characteristic impurity compounds that are the markers of synthetic alcohol were absent), which met the requirements of GOST (State Standard) R 51698-2000. In the samples of illegal alcohol (from Kyzyl), diethyl phthalate (850–1284 mg/L) and, in one sample, ethylene glycol (380 mg/L, accidental contaminant) were found. The occurrence of diethyl phthalate indicated that vodka (aqueous alcohol mixture) was prepared from commercial denatured alcohol. An analysis of regulatory documents and published data allowed us to draw the following conclusions: (1) diethyl phthalate does not meet the requirements imposed on denaturing additives, and it is used as a denaturing agent only in Russia; (2) the test samples of illegal alcohol do not differ from food ethanol solutions of analogous strength in terms of acute toxicity parameters; and (3) surrogate alcohols in illicit trade are not the main reason for high mortality from alcohol intoxication in the test region (Kyzyl and the Tyva Republic).     

Magnetic cobalt-nitrogen-doped carbon microspheres for the preconcentration of phthalate esters from beverage and milk samples

The authors describe the preparation of magnetic cobalt/nitrogen-doped carbon microspheres (Co-N/Cs) by combining a hydrothermal procedure with a carbonization process. The textures of the Co-N/Cs were investigated by powder X-ray diffraction, scanning electron microscopy, high-resolution transmission electron microscopy, nitrogen adsorption-desorption isotherms and vibration sample magnetometry. The Co-N/Cs possess a high surface area and strong magnetism. This results in good adsorption capability and enables magnetic separation. The Co-N/Cs are shown to be an effective magnetic solid-phase extraction adsorbent for the enrichment of various phthalate esters (diethyl phthalate, diallyl phthalate and diisobutyl phthalate) from sport beverages and milk samples prior to their determination by HPLC. The limits of detection (at an S/N ratio of 3) are between 0.1–0.2 and 0.08–0.3 ng mL^?1 for sport beverages and milk samples, respectively. The recoveries when extracting all the spiked samples varied from 80.3% to 116.2%.

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Graphical abstract Magnetic cobalt/nitrogen-doped carbon microspheres (Co-N/Cs) were prepared and used as an effective magnetic solid phase extraction adsorbent for the enrichment of phthalate esters from beverages and milk samples.

     

Direct quantitative analysis of phthalate esters as micro-contaminants in cleanroom air and wafer surfaces by auto-thermal desorption--gas chromatography--mass spectrometry

This study established an analytical method for the trace analyses of two phthalate esters, including diethyl phthalate (DEP) and di-n-butyl phthalate (DBP), known as the major constituents of cleanroom micro-contamination detrimental to the reliability of semiconductor devices. Using thermal desorption coupled with a GC-MS system, standard tubes were prepared by delivering liquid standards pre-vaporized by a quasi-vaporizer into Tenax GR tubes for calibration. This method was capable of achieving detection limits of 0.05 microg m(-3) for 0.1 m3 air samples and 0.03 ng cm(-2) for 150-mm wafer surface density. Actual samples collected from a semiconductor cleanroom showed that the concentration of DBP in a polypropylene wafer box (0.45 microg m(-3)) was nearly four times higher than that in the cleanroom environment (0.12 microg m(-3)). The surface contamination of DBP was 0.67 ng cm(-2) for a wafer stored in the wafer box for 24 h. Furthermore, among the three types of heat-resistant O-ring materials tested, Kalrez was found to be particularly suitable for high-temperature processes in semiconductor cleanrooms due to their low emissions of organic vapors. This analytical procedure should serve as an effective monitoring method for the organic micro-contamination in cleanroom environments.     

Detection of Phthalate Esters in Environmental Water Samples-Comparison of Nylon6 Nanofibers Mat-based Solid Phase Extraction and Other Conventional Extraction Methods

In this article, a new method for simultaneous determination of six phthalate esters was developed by a combination of electrospun nylon6 nanofibers mat‐based solid phase extraction with high performance liquid chromatography‐ultraviolet detector (HPLC‐UV). The six phthalate esters were dimethyl phthalate (DMP), diethyl phthalate (DEP), butyl benzyl phthalate (BBP), di‐n‐butyl phthalate (DBP), di‐(2‐ethylhexyl) phthalate (DEHP) and dioctyl phthalate (DOP). Under optimized conditions, all target analytes in 50 mL environmental water samples could be completely extracted by 2.5 mg nylon6 nanofibers mat and eluted by 100 µL solvent. Compared with C18 cartridges solid phase extraction, C18 disks solid phase extraction and national standard method (China), nylon6 nanofibers mat‐based solid phase extraction was advantageous in aspects of simple and fast operation, low consumption of extraction materials and organic solvents. The four methods were applied to analysis of environment water samples. All the results indicated that the determination values of target compounds with the proposed method were consistent with C18 cartridges and C18 disks solid phase extraction method, and the new method was better than the national standard method in aspects of recovery, LOD and precision. Therefore, nylon6 nanofibers mat has great potential as a novel material for solid phase extraction.     

Application of dispersive liquid-liquid microextraction and high-performance liquid chromatography for the determination of three phthalate esters in water samples

A novel method, dispersive liquid-liquid microextraction (DLLME) coupled with high-performance liquid chromatography-variable wavelength detector (HPLC-VWD), has been developed for the determination of three phthalate esters (dimethyl phthalate (DMP), diethyl phthalate (DEP), and di-n-butyl phthalate (DnBP)) in water samples. A mixture of extraction solvent (41 μL carbon tetrachloride) and dispersive solvent (0.75 mL acetonitrile) were rapidly injected into 5.0 mL aqueous sample for the formation of cloudy solution, the analytes in the sample were extracted into the fine droplets of CCl₄. After extraction, phase separation was performed by centrifugation and the enriched analytes in the sedimented phase were determined by HPLC-VWD. Some important parameters, such as the kind and volume of extraction solvent and dispersive solvent, extraction time and salt effect were investigated and optimized. Under the optimum extraction condition, the method yields a linear calibration curve in the concentration range from 5 to 5000 ng mL⁻¹ for target analytes. The enrichment factors for DMP, DEP and DnBP were 45, 92 and 196, respectively, and the limits of detection were 1.8, 0.88 and 0.64 ng mL⁻¹, respectively. The relative standard deviations (R.S.D.) for the extraction of 10 ng mL⁻¹ of phthalate esters were in the range of 4.3-5.9% (n = 7). Lake water, tap water and bottled mineral water samples were successfully analyzed using the proposed method.     

Utilization of homogeneous liquid–liquid extraction followed by HPLC-UV as a sensitive method for the extraction and determination of phthalate esters in environmental water samples

A simple and sensitive method for the extraction of four phthalate esters including dimethyl phthalate (DMP), diethyl phthalate (DEP), benzyl butyl phthalate (BBP) and di-n-butyl phthalate (DBP) as well as their determination in water samples was developed using homogeneous liquid–liquid extraction (HLLE) and HPLC-UV. The extraction method is based on the phase separation phenomenon by the salt addition to the ternary solvent system. The extraction parameters such as type and volume of extracting and consolute solvent, concentration of salt, pH of sample and extraction time were optimized. Under the optimal conditions (extraction solvent: 100?µL CHCl₃; consolute solvent: 2.0?mL methanol; NaCl 15% (w/v) and pH of sample: 6.5) extraction recovery was in the range of 92–102%. Linearity was observed in the range of 0.5–300?µg?L^?1 for DEP and 0.6–300?µg?L^?1 for DMP, BBP and DBP. Correlation coefficients (r ²), limits of detection (LODs) and relative standard deviations (RSDs) were in the ranges of 0.9976–0.9993, 0.18–0.25 and 1.5–4.8%, respectively. The method was successfully applied for the preconcentration and determination of these phthalate esters in the several environmental water samples.