Development of a mathematical model for online microextraction by packed sorbent under equilibrium conditions and its application for polycyclic aromatic hydrocarbon determination in water by gas chromatography–mass spectrometry (original) (raw)
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Journal of Chromatography A, 2014
In this work, two different extraction procedures for the analysis of different polycyclic aromatic hydrocarbons (PAHs) in water by microextraction by packed sorbent (MEPS) have been compared in terms of sensitivity, reliability and time of analysis. The first method, called "draw-eject", consists of a sequence of cycles of aspirations and injections in the same vial; the second one, called "extract-discard", consists of a similar cycle sequence, but the aspired sample in this case is discarded into waste. The relevant partition equilibriums and extraction rates have been calculated by multivariate regression from the data obtained after MEPS gas chromatography-mass spectrometry (MEPS-GC-MS) analysis of 16 PAHs from water samples. Partitioning parameters for a priori prediction of solute sorption equilibrium, recoveries and preconcentration effects in aqueous and solvent systems have been calculated and compared for the two extraction procedures. Finally, real samples from sea, agricultural irrigation wells, streams and tap water were analyzed. Detection (S/N ≥ 3) and quantification (S/N ≥ 10) limits were calculated for the extraction processes. Under the experimental conditions used for the "draw-eject" procedure, these values were in the range 0.5-2 ng L −1 and 1.6-6.2 ng L −1 , while for the "extract-discard" procedure they ranged from 0.2 to 0.8 ng L −1 and from 0.8 to 2.0 ng L −1 , respectively.
Recent developments in sorbent based water samples treatments prior GC-MS analysis of polycyclic aromatic hydrocarbons
Polycyclic aromatic hydrocarbons (PAHs) are omnipresent contaminants of the environment, with evidenced harmful effects to human health. Especially endangered are waters, which may affect biota directly or by enabling transport through all environmental compartments. Therefore, constant monitoring of PAHs content in waters is of essential importance. Before most of the analysis, sample preparation is compulsory. Conventional extraction techniques are often time and reagents consuming and not following the rules of "green analytical chemistry". Thus, miniaturization of classic extraction methods is of high importance to reduce solvent volumes, waste, time of treatment and cost. Recent sample preparation techniques, such as solid phase extraction (SPE), microextraction by packed sorbent (MEPS), solid phase microextraction (SPME), stir bar sorptive extraction (SBSE), dispersive solid phase extraction (dSPE) and dispersive micro-solid phase extraction (D-µ-SPE) were proven as suitable for the extraction of polycyclic aromatic hydrocarbons (PAHs) from water samples and their determination by gas chromatography-mass spectrometry. These sample pretreatments are following "green chemistry" principles, offering the simplicity of operation, reducing costs and time of preparation, without compromising the general analytical parameters of the applied analytical method.
2021
A dispersive suspended microextraction (DSME) method coupled with gas chromatography-mass spectrometry (GC-MS) was developed and validated for the simultaneous determination of ten polycyclic aromatic hydrocarbons in real water samples. The optimization of the method was achieved with a 2 7-4 Plackett-Burman design, while the significant factors were optimized using a central composite design (CCD). The parameters that were studied included the sample volume, organic solvent volume, extraction time, restoration time and organic solvent. The optimum experimental conditions for the proposed method comprised 4.3 mL of the water sample, 93 L of toluene as the extraction solvent, a 104-s extraction time and a 10-min restoration time. The recoveries varied from 70 to 111%. Chrysene was the least recovered compound, while anthracene displayed the highest extraction efficiency. The analytical method (DSME) was shown to be linear (R 2 > 0.993) over the studied range of concentrations, exhibiting satisfactory precision (RSD% < 10.6%) and reaching limits of detection between 8 and 46 ng L −1 .
Journal of the Brazilian Chemical Society
In this study, the use of bracts as a natural sorbent in solid-phase microextraction was exploited for use in the determination of polycyclic aromatic hydrocarbons in water samples with separation/detection performed by gas chromatography-mass spectrometry. Fiber-to-fiber reproducibility was evaluated and the relative standard deviation (RSD) was lower than 14%. Optimizations were performed using both the proposed and DVB/Car/PDMS (divinylbenzene/ carboxen/polydimethylsiloxane) fibers. The optimum extraction conditions were 80 min of extraction at 50 °C with 12% (m/v) NaCl for the bract fiber, and 100 min of extraction at 80 °C for the commercial fiber. The limits of detection and quantification for the proposed fiber were, respectively, 0.003 and 0.01 µg L-1 for fluorene, phenanthrene, anthracene and pyrene, and 0.03 and 0.1 µg L-1 for acenaphthylene, benzo(a)anthracene and chrysene. The method using bract fiber provided relative recoveries ranging from 68 to 117%, intraday and interday precisions lower than 17 and 19%, respectively, and extraction efficiency similar to that of the DVB/Car/PDMS fiber.
Iranian Journal of Pharmaceutical Research : IJPR, 2016
Polycyclic aromatic hydrocarbons (PAHs) are classified as persistent and carcinogenic organic pollutants. PAHs contamination has been reported in water. Many of relevant regulatory bodies such as EU and EPA have regulated the limit levels for PAHs in drinking water. In this study, 13 priority polycyclic aromatic hydrocarbons (PAHs) were determined in tap water samples of Tehran and water for injection. Dispersive liquid-liquid microextraction procedure combined with gas chromatography-mass spectrometry was used for the extraction and determination of PAHs in the samples. Under the optimized conditions, the range of extraction recoveries and relative standard deviations (RSDs) of PAHs in water using internal standard (anthracene-d10) were in the range of 71-90% and 4-16%, respectively. Limit of detection for different PAHs were between 0.03 and 0.1 ngmL-1. The concentration of PAHs in all tap water as well as water for injection samples were lower than the limit of quantification of ...
Analytical Chemistry, 2000
The determination of distribution coefficients is important for prediction of the chemical pathways of organic compounds in the environment. Solid-phase microextraction (SPME) is a convenient and effective method to measure the distribution of chemicals in a two-phase system. In the present study, the SPME distribution coefficient (K spme) of 16 priority aromatic hydrocarbons (PAHs) was determined with 100-µm poly(dimethylsiloxane) (PDMS) and 85-µm polyacrylate (PA) fibers. The partition coefficients and LeBas molar volumes were used to describe the linearity of the log K spme values of PAHs. Also, the validation of the distribution coefficient was examined using different sample volumes. The extraction time was dependent on the types of PAHs, and 20 min to 60 h was needed to reach equilibrium. The determined log K spme values ranged from 3.02 to 5.69 and from 3.37 to 5.62 for 100-µm PDMS and 85-µm PA fibers, respectively. Higher K spme values of low-ring PAHs were observed using 85-µm PA fiber. Good linear relationships between log K ow and log K spme for PAHs from naphthalene to benzo-[a]pyrene and from naphthalene to chrysene for 100-µm PDMS and 85-µm PA fibers, respectively, were obtained. The correlation coefficients were 0.969 and 0.967, respectively. The linear relationship between log K spme and the LeBas molar volume was only up to benz[a]anthracene for 85-µm PA fiber and up to chrysene for 100µm PDMS fiber. Moreover, the effect of sample volume can be predicted using the partition coefficient theory and excellent agreement was obtained between the experimental and theoretical absorbed amounts of low-ring PAHs. This result shows that the determined log K spme is more accurate than the previous method for estimating analytes with log K ow < 6 as well as for predicting the partitioning behaviors between SPME fiber and water. The physicochemical data of xenobiotic compounds are usually used to predict their environmental fate and effects and that of compounds with similar physicochemical properties. Hydorphobicity is one of the most important parameters governing the distribution behavior of xenobiotics in the environment. The octanol-water partition coefficient (K ow) is widely accepted as the
Journal of Chromatography A, 2012
This study proposes a new optimization approach for the simultaneous determination of polycyclic aromatic hydrocarbons (PAHs) and benzene, toluene, ethylbenzene and xylene isomers (BTEX) from water samples using the solid-phase microextraction technique followed by gas chromatography-mass spectrometry (GC-MS) separation and detection. The objective of the study was to achieve compromise extraction conditions, suitable for all semi-volatile and volatile compounds, under which the amount extracted is maximized for all analytes. This was achieved by careful optimization of the fiber coating, salting-out effect, extraction time and temperature and extraction mode (headspace or direct immersion). With the optimized fiber coating -PDMS/DVB 65 m -the other selected factors were optimized using a response surface methodology through central composite designs. As expected, the optimized results for each class of analytes varied significantly, probably due to the differences in their volatility and the equilibrium constants for the analyte/fiber coating. In order to overcome this issue, a new optimization approach was proposed based on a combination of extraction modes and extraction temperatures in a single extraction procedure. The final optimized procedure was: 48 min of extraction in direct immersion mode with the sample maintained at 80 • C followed by a further 32 min of headspace extraction with the sample temperature kept at 10 • C. The proposed procedure was compared with conventional methods based on the use of a single extraction mode and temperature (80 min of headspace extraction at 60 • C or 80 min of direct immersion extraction at 50 • C). The newly proposed method was shown to be more attractive as it extracted higher amounts of both semi-volatile and volatile compounds in a single extraction procedure compared to the conventional approaches. The optimized method was validated and excellent results were obtained.
Annals of Chromatography and Separation Techniques, 2016
Various methods were developed and validated for the analysis of Polycyclic Aromatic Hydrocarbons (PAHs), in the environmental samples. However, their analysis in relevant concentrations in environmental samples can be a challenging task. The aim of this study was to estimate the performance of a modified standard procedure for the determination of polycyclic aromatic hydrocarbons in environmental water samples using liquid-liquid extraction as a preparation step followed by gas chromatography/mass spectrometry. Implementation of long term quality control procedures after validation of the analytical procedures enables acquisition of accurate and reliable results. Three year monitoring of the quality control samples (containing 10-40 ng/L of PAHs) showed that method main characteristics, such as accuracy, precision and measurement uncertainty have constant stability and with no statistically significant changes during this period.
Journal of Separation Science, 2012
This article introduces a simple, rapid, and reliable solid-phase microextraction (SPME) method coupled with GC-MS for the quantitative determination of 16 polycyclic aromatic hydrocarbons in water. In this study, the Taguchi experimental design was used to optimize extraction conditions of polycyclic aromatic hydrocarbons using SPME method to obtain highly enriched analytes. Consequently, quantitative determination of polycyclic aromatic hydrocarbons in water was achieved by GC-MS technique. The selected parameters affecting enrichment of polycyclic aromatic hydrocarbons were sample extraction time, stirring speed, temperature, ionic strength, and pH. The study revealed that optimal operating conditions were found to be 90-min extraction time, 1400 rpm stirring speed, and 60ЊC sample temperature. The effect of ionic strength and pH were shown to be insignificant. Optimized conditions were also reevaluated by placing the 16 polycyclic aromatic hydrocarbons into several subgroups based on their molecular weight. The extraction efficiency of polycyclic aromatic hydrocarbons with low molecular weight was shown to be a function of only the extracting temperature. Satisfactory results were obtained for linearity (0.983-0.999), detection limits (2.67-18.02 ng/L), accuracy (71.2-99.3%), and precision (4.3-13.5%). The optimum conditions reported by other design approaches were evaluated and generalized optimum conditions were suggested.