Phthalate Esters In Water Samples Research Articles

Development of an ionic liquid‐based dispersive liquid–liquid micro‐extraction method for the determination of phthalate esters in water samples

Ionic liquid-based dispersive liquid-liquid micro-extraction (IL-DLLME) was coupled with high-performance liquid chromatography-ultraviolet (HPLC-UV) for the determination of four phthalate esters, including butyl benzyl phthalate, di-n-butyl phthalate, dicyclohexyl phthalate and bis(2-ethylhexyl) phthalate in water samples. The mixture of ionic liquid (IL) and dispersive solvent was rapidly injected into 10 mL aqueous sample. Then, IL phase was separated by centrifugation and was determined by high-performance liquid chromatography-ultraviolet. The factors influencing the extraction efficiency, such as type and volume of IL, disperse solvent, extraction time, centrifuging time and ionic strength, were investigated and optimized. Under the optimized conditions, the extraction recoveries by the proposed ionic liquid-based dispersive liquid-liquid micro-extraction for the four phthalates ranged from 83.0 to 91.7%. The relative standard deviations were between 7.8 and 15%. The limits of quantification for four phthalates were between 10.6 and 28.5 μg/L. The proposed method was successfully applied for the analysis of PAEs in tap, lake and treated wastewater samples.

Determination of phthalate esters in water samples by ionic liquid cold-induced aggregation dispersive liquid–liquid microextraction coupled with high-performance liquid chromatography

A novel method, termed ionic liquid cold-induced aggregation dispersive liquid–liquid microextraction (IL-CIA-DLLME), combined with high-performance liquid chromatography (HPLC) was developed for the determination of three phthalate esters in water samples. Several important parameters influencing the IL-CIA-DLLME extraction efficiency, such as the type of extraction and disperser solvent, the volume of extraction and disperser solvent, temperature, extraction time and salt effect, were investigated. Under optimal extraction conditions, the enrichment factors and extraction recoveries ranged from 174 to 212 and 69.9 to 84.8%, respectively. Excellent linearity with coefficients of correlation from 0.9968 to 0.9994 was observed in the concentration range of 2–100 ng mL −1. The repeatability of the proposed method expressed as relative standard deviations ranged from 2.2 to 3.7% ( n = 5). Limits of detection were between 0.68 and 1.36 ng mL −1. Good relative recoveries for phthalate esters in tap, bottled mineral and river water samples were obtained in the ranges of 91.5–98.1%, 92.4–99.2% and 90.1–96.8%, respectively. Thus, the proposed method has excellent potential for the determination of phthalate esters in the environmental field.

Determination of phthalate esters in water samples using Nylon6 nanofibers mat-based solid-phase extraction coupled to liquid chromatography

A new method was developed for simultaneous determination of five phthalate esters by a combination of mat-based solid-phase extraction (SPE) with high-performance liquid chromatography. The mat is composed of Nylon6 nanofibers. Dimethyl phthalate (DMP), diethl phthalate (DEP), di-n-butyl phthalate (DBP), di-(2-ethylhexyl) phthalate (DEHP) and dioctyl phthalate (DOP) were successfully separated on a RP-C18 column. Under optimized conditions, the detection limits found for DMP, DEP, DBP, DEHP and DOP were 3, 2, 6, 10 and 33 pg mL−1, respectively. The method was applied to the analysis of various water samples. Spiked samples gave recoveries in the range from 86.9 to 101.9%, with relative standard deviations below 7.0%. A comparison of Nylon6 nanofibers mat as sorbents, and C18 cartridges and other kinds of SPE sorbents was carried out with respect to recovery, sensitivity, and reproducibility. The results indicated that the Nylon mat is a viable material for the enrichment and determination of phthalate esters in environmental water samples.

LC Determination of Phthalate Esters in Water Samples Using Continuous-Flow Microextraction

A novel method, continuous-flow microextraction (CFME) combined with liquid chromatography (LC) with variable-wavelength detector (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. Experimental parameters including extraction solvent, solvent drop volume, flow rate of sample solution, extraction time and ionic strength, which affected the extraction efficiency, were studied and optimized. Under the optimum extraction conditions, the method yields a linear calibration curve in the concentration range of 10–10,000 ng mL -1 for target analytes. The enrichment factors of this method for DMP, DEP and DnBP reached at 27, 44 and 20, respectively, and the detection limits were 2, 1 and 5n g mL -1 , respectively. Good repeatability of extraction was obtained with relative standard deviations below 8.6%. The results demonstrated that CFME followed by LC-VWD is a simple and reliable technique for the determination of phthalate esters in water samples.

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 CCl 4. 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.

Development of dispersive liquid–liquid microextraction combined with gas chromatography–mass spectrometry as a simple, rapid and highly sensitive method for the determination of phthalate esters in water samples

A simple, rapid and efficient method, the dispersive liquid–liquid microextraction (DLLME) in conjunction with gas chromatography–mass spectrometry (GC–MS), has been developed for the extraction and determination of phthalate esters (dimethyl phthalate, diallyl phthalate, di- n-butyl phthalate, benzyl butyl phthalate, dicyclohexyl phthalate and di-2-ethylhexyl phthalate) in water samples. Factors relevant to the microextraction efficiency, such as the kind of extraction, the disperser solvent and their volume, the salt effect and the extraction time were investigated and optimized. Under the optimized extraction conditions (extraction solvent: chlorobenzene, volume, 9.5 μL; disperser solvent: acetone, volume, 0.50 mL, without salt addition and extraction time below 5 s), the figures of merit of the proposed method were evaluated. The values of the detection limit of the method were in the range of 0.002–0.008 μg L −1, while the RSD% value for the analysis of 1 μg L −1 of the analytes was below 6.8% ( n = 4). A good linearity (0.9962 ≥ r 2 ≥ 0.9901) and a broad linear range (0.02–100 μg L −1) were obtained. The method exhibited enrichment factors and recoveries, ranging from 681 to 889 and 68.1 to 88.9%, respectively, at room temperature (25 ± 1 °C). Finally, the proposed method was successfully utilized for the preconcentration and determination of the phthalate esters in different real water samples and satisfactory results were obtained.

Preparation and characterization of octyl and octadecyl-modified mesoporous SBA-15 silica molecular sieves for adsorption of dimethyl phthalate and diethyl phthalate

Octyl (C 8) or octadecyl (C 18)-modified mesoporous SBA-15 silica molecular sieves have been prepared by adding SBA-15 silica molecular sieves to octyltrimethoxysilane or octadecyltrimethoxysilane in toluene at 100 °C, and characterized by Fourier transform infrared (FTIR) spectroscopy, powder X-ray diffraction (XRD), nitrogen adsorption–desorption measurements, scanning electron microscopy (SEM) and transmission electron microscopy (TEM). FTIR spectra shows the presence of methylene (–CH 2–) and methyl (–CH 3) bands on the modified SBA-15. Powder XRD data indicate the structure of modified SBA-15 with octyl or octadecyl groups still remains two-dimensional hexagonal mesostructrure. Brunauer–Emmett–Teller (BET) surface area analysis presents that surface area of octyl- and octadeyl-SBA-15 changed from 647 to 449 and 321 m 2 g −1, respectively, and SEM images show the decreased size of modified SBA-15 particles. TEM images of modified materials with alkyl groups show the structures remain the same as the parent SBA-15 silica. We also have studied the adsorption capacity of the materials to phthalate esters (dimethyl and diethyl phthalate) by dynamic adsorption experiments on high performance liquid chromatography (HPLC). It is found that the modified materials can increase the adsorption of phthalate esters compared to SBA-15 particles, and the adsorption capacity increased with the increased length of alkyl chain on SBA-15. The maximum dynamic adsorption capacity for diethyl phthalate was 3.9 (C 8-SBA-15) or 4.3 (C 18-SBA-15) times higher than that of SBA-15 particles, respectively. The results indicate that alkyl SBA-15 particles could be used for enrichment of phthalate esters in water samples before the further analysis.

Solid-phase extraction of several phthalate esters from environmental water samples on a column packed with polytetrafluoroethylene turnings.

A method for the determination of several phthalate esters in water samples using solid-phase extraction coupled to high-performance liquid chromatography was developed. A polytetrafluoroethylene turnings packed column was used as a SPE adsorbent material. The analytes were sorbed on polytetrafluoroethylene turnings, from which they were eluted by a small amount of acetonitrile, followed by a RP-HPLC-UV analysis. Detection limits (3sigma) of 4.7, 3.1, 3.6, 4.3, and 5.8 ng mL(-1) for di-n-butyl-phthalate, di-cyclohexyl-phthalate, di-n-octyl-phthalate, di-n-nonyl-phthalate and di-iso-decyl-phthalate, respectively, were achieved. Acceptable recovery results (92.1-127.5%) were obtained on five phthalate esters spiked samples.

Hollow-fibre liquid-phase microextraction of phthalate esters from water

A simple and efficient liquid-phase microextraction (LPME) technique using a hollow-fibre membrane, in conjunction with gas chromatography–mass spectrometry has been developed for the extraction and analysis of six phthalate esters in water samples. Parameters such as extraction solvent, agitation of the sample, salt addition and extraction time were controlled and optimised. The developed protocol was found to yield a linear calibration curve in the concentration range from 0.02 to 10 μg l −1 for most target analytes and the limits of detection were in the low μg l −1 level, ranging between 0.005 and 0.1 μg l −1. The repeatability of the method varied between 4% and 11%. Under the present experimental conditions, the performance of the method was found comparable to that of solid-phase microextraction (SPME). The advantage of the proposed method over SPME was that it eliminated carry-over of analytes between runs. The applicability of the developed hollow-fibre LPME method and SPME was demonstrated for real water samples. The ability of both microextraction methods to concentrate many organic analytes was demonstrated as both methods allowed the confirmation of the presence of an extra contaminant (ethyl p-ethoxybenzoate) in bottled mineral water samples.

Application of Time-Resolved Luminescence Methodology to the Determination of Phthalate Esters

The usefulness of terbium-sensitized luminescence for the determination of total phthalate esters in water samples is studied. A simple and fast method is described for this purpose, which could be used for screening purposes. After alkaline hydrolysis of phthalate esters, a luminescent chelate between terbium(III) and phthalate is formed. Luminescence measurements are obtained at λ ex 240 nm and λ em 545 nm by using the time-resolved mode of the instrument. Linear calibration graphs were obtained in the range 0.15–72 µM for dimethyl-, diethyl- and dibutylphthalate esters, and in the range 0.21–18 µM for bis(2-ethylhexyl)phthalate ester. The relative standard deviation was lower than 1.5%. The method was applied to the determination of total phthalates in drinking, well and river water samples. Solid-phase microextraction was used to avoid the loss of sensitivity in the analysis of water samples by dilution. Analytical recoveries ranged from 91.5 to 102.0%.

Determination of phthalate esters in water samples by solid-phase microextraction and gas chromatography with mass spectrometric detection

Solid-phase microextraction (SPME) with an 85 μm polyacrylate fiber, coupled to gas chromatography–mass spectrometry was used to determine six phthalate esters and bis(2-ethylhexyl) adipate in water samples. The variables affecting the SPME absorption process were optimized and the method developed was applied to analyze both tap and commercial mineral water samples as well as water from the Ebro river and fishing and industrial ports. For real samples, the linear range in full scan acquisition mode was between 0.02 and 10 μg l −1 for most compounds, and the limits of detection of the method were between 0.006 and 0.17 μg l −1. Commercial water samples contained in recipients which were made from different materials were analyzed, and the influence of the material of the recipients on the concentration of phthalates was evaluated.