Organic Compounds In Aqueous Samples Research Articles

Coating evaluation of polydimethylsiloxane-aminopropylsiloxane for stir bar sorptive extraction

In stir bar sorptive extraction (SBSE), a coating is typically used to isolate and preconcentrate organic compounds in aqueous samples. Here, a translucent coating based on polydimethylsiloxane and aminopropyltriethoxysilane was prepared by a sol–gel method. Characterization tests showed that the coating was homogeneous, relatively polar, and both thermally (≤ 400°C) and chemically stable. Coated stir bars were evaluated in SBSE experiments. Benzene derivatives and furanic compounds were successfully extracted/preconcentrated from aqueous and organic solutions. Furanic compounds and benzene derivatives were moderately extracted from water, but they were sufficiently extracted from isooctane.

Stir Bar Sorption Extraction (SBSE) and Its Application for Analysis of Organic Compounds in Aqueous Samples: A Review

Sample preparation is one of the crucial steps in any chemical analysis because most samples are not ready to introduce directly into analytical instruments. This step is very important to eliminate interferences, isolate and preconcentration of analytes of interest from the matrix and makes them more suitable for separation and detection. The extraction of analytes from aqueous matrices can be traditional and nontraditional techniques. Miniaturized techniques are simple, solventless or solvent-reduced techniques allowing the extraction and concentration in a single step on a micro scale approach. Stir Bar Sorptive Extraction (SBSE) is a relatively new solventless sample preparation method for the extraction and concentration of organic compounds from aqueous matrices of environmental, food and biological samples. In SBSE, a stir bar coated with Polydimethylsiloxane (PDMS) phase is added to a vial containing the sample. The sample is then stirred until analytes partition equilibrium time reached with sorbent. The extracts can be introduced quantitatively into the analytical system by thermal or liquid desorption. The efficiency of extraction of SBSE in terms of the amount extracted and the equilibrium is affected by extraction time, stirring speed, temperature of the sample, pH, salting and sample volume. The most important limitation of SBSE is the only commercial availability of PDMS coating material exists at present. Besides, due to the non-polar character of PDMS, SBSE technique is mainly applied to extract non-polar and weakly polar compounds but failed in extraction of strongly polar compounds. Keywords : Stir Bar Sorptive Extraction, Polydimethylsiloxane, Sample Preparation, Organic Compounds DOI: 10.7176/CMR/13-1-01 Publication date: January 31 st 2021

Solid phase microextraction of organochlorine pesticides in water using MWCNTs-doped polypyrrole coated on steel fiber

The analysis of organochlorine pesticides (OCPs) residues has received an increasing attention in the last decades. Solid-phase microextration (SPME) is a convenient and fast analytical method, which has been widely used for the determination of volatile and semivolatile organic compounds in aqueous samples. The multiwalled carbon nanotubes/polypyrrole composite coating was used for the SPME of OCPs in water samples. The effects of various parameters on the efficiency of SPME process such as extraction time, extraction temperature, ionic strength, desorption time, and desorption temperature were studied. Under optimized conditions, the detection limits for the OCPs varied between 0.051 and 0.39 pg mL-1, the inter-day and intra-day relative standard deviations for various OCPs using a single fiber were 6.5-11.5% and 3.6-11.5, respectively. The linear ranges varied between 0.001 and 1 ng mL-1. The method was successfully applied to the analysis of ground water samples with the recoveries from 86 to 110%.

A field portable membrane introduction mass spectrometer with in-line standard infusion and sample heat exchanger for real-time monitoring of volatile organic compounds in aqueous samples

Abstract Maintaining a steady sample temperature when analyzing real-time samples in the field is crucial for Membrane Introduction Mass Spectrometry (MIMS). Diffusion through the membrane interface is temperature dependent, and sample temperature might vary depending on the sample source. In order to reduce this source of inaccuracy, an in-field and online continuous monitoring system based on (MIMS) coupled with a heat exchanger and in-line standard addition was developed for monitoring volatile organic compounds (VOC) in actual field samples. Parametric studies of the heat exchanger have been conducted in the laboratory. In order to maintain control on instrumental signal drift during continuous, long-term analysis periods, the system used continuous infusion of internal standard (tuloene-d8) into the sample stream and also provided the possibility to infuse, in the same way, an analyte for standard addition calibration. This set-up has been utilized in the field for analyzing both natural water sources and heavily polluted process water. The system was demonstrated to offer a rapid method for quantifying volatile hazardous pollutants in aqueous matrices with good time-resolution.

Evaluation of Polydimethylsiloxane-Phenylsiloxane as a Coating for Stir Bar Sorptive Extraction

Analytical pretreatment has become environmental-friendly because of material science assistance. In stir bar sorptive extraction (SBSE), a coating is typically used to isolate and preconcentrate organic compounds in aqueous samples. Here, a translucent coating based on polydimethylsiloxane and phenyltriethoxysilane was prepared by a sol-gel method. Characterization tests showed that the coating was homogeneous, relatively polar, and both thermally (< 400 °C) and chemically stable. Coated stir bars were evaluated in the SBSE experiments. Benzene derivatives were successfully extracted/preconcentrated from aqueous solutions and environmental waters. Furanic derivatives and antibiotics were moderately extracted from water, but they were extracted from isooctane.

Rapid and sensitive on-line monitoring 6 different kinds of volatile organic compounds in aqueous samples by spray inlet proton transfer reaction mass spectrometry (SI-PTR-MS)

Rapid and sensitive monitoring of volatile organic compounds (VOCs) in aqueous samples is very important to human health and environmental protection. In this study, an on-line spray inlet proton transfer reaction mass spectrometry (SI-PTR-MS) method was developed for the rapid and sensitive monitoring of 6 different kinds of VOCs, namely acetonitrile, acetaldehyde, ethanol, acetone, aether, and methylbenzene, in aqueous samples. The response time, limit of detection (LOD), and repeatability of the SI-PTR-MS system were evaluated. The response of the SI-PTR-MS was quite rapid with response times of 31–88 s. The LODs for all these VOCs were below 10 μg/L. The LOD of methylbenzene was 0.9 μg/L, much lower than the maximum contaminant level (MCL) in drinking water. The repeatability of this method was evaluated with 5 replicate determinations. The relative standard deviations (RSDs) were in the range of 0.8–3.1%, indicating good repeatability. To evaluate the matrix effects, the SI-PTR-MS system was employed for on-line monitoring of these 6 VOCs in different aqueous matrices, including lake water, tap water, and waste water. The relative recoveries were in the range of 94.6–106.0% for the lake water, 96.3–105.6% for the tap water, and 95.6–102.9% for the waste water. The results indicate that the SI-PTR-MS method has important application values in the rapid and sensitive monitoring of VOCs in these aqueous samples. In addition, the effect of salt concentration on the extracting efficiency was evaluated. The results showed that the LOD of the SI-PTR-MS could be further decreased by changing the salt concentration.

Fabrication of polyaniline-coated halloysite nanotubes by in situ chemical polymerization as a solid-phase microextraction coating for the analysis of volatile organic compounds in aqueous solutions.

We have synthesized an organic-inorganic polyaniline-halloysite nanotube composite by an in situ polymerization method. This nanocomposite is immobilized on a stainless-steel wire and can be used as a fiber coating for solid-phase microextraction. It was found that our new solid-phase microextraction fiber is an excellent adsorbent for the extraction of some volatile organic compounds in aqueous samples in combination with gas chromatography and mass spectrometry. The coating can be prepared easily, is mechanically stable, and exhibits relatively high thermal stability. It is capable of extracting phenolic compounds from water samples. Following thermal desorption, the phenols were quantified by gas chromatography with mass spectrometry. The effects of extraction temperature, extraction time, sample ionic strength, stirring rate, pH, desorption temperature and desorption time were studied. Under optimal conditions, the repeatability for one fiber (n = 5), expressed as the relative standard deviation, is between 6.2 and 9.1%. The detection limits range from 0.005 to 4 ng/mL. The method offers the advantage of being simple to use, with a shorter analysis time, lower cost of equipment and higher thermal stability of the fiber in comparison to conventional methods of analysis.

針型濃縮デバイスを用いる水試料中の揮発性有機化合物の分析

針型濃縮デバイスを用いる水試料中の揮発性有機化合物の分析

Polybutylene terephthalate-nickel oxide nanocomposite as a fiber coating

A highly efficient polybutylene terephthalate (PBT)-based nanocomposite containing nickel oxide nanoparticles was synthesized by electrospinning technique and used as a fiber coating for solid phase microextraction. The influential morphological parameters and capability of the prepared nanocomposite including the NiO content, the coating time, the PBT concentration and applied voltage were considered for optimization. The applicability of the synthesized fiber coating was examined by headspace solid phase micro extraction and gas chromatography mass spectrometry detection of some volatile organic compounds in aqueous samples. Among the synthesized nanocomposites and pristine PBT nanofibers, the fiber coating with 14% of NiO nanoparticles doping level exhibited the highest extraction efficiency. In addition, important parameters influencing the extraction/desorption process were investigated and optimized. The detection limits were less than 5ngL−1 using the selected ion monitoring mode. The inter-day and intra-day precisions of the developed method under optimized conditions were below 11%. The method showed a linearity in the range of 10–1000ngL−1 with the correlation coefficient greater than 0.9987. The optimized method was applied to the sampling of some volatile organic compounds from real water samples. The developed method is convenient, rapid, simple, easy and inexpensive and offers high sensitivity and sufficient reproducibility.

Headspace GC–MS Analysis of Halogenated Volatile Organic Compounds in Aqueous Samples: An Experiment for General Chemistry Laboratory

Analysis of halogenated volatile organic compounds (HVOCs) by GC–MS demonstrates the use of instrumentation in the environmental analysis of pollutant molecules and enhances student understanding of stable isotopes in nature. In this experiment, students separated and identified several HVOCs that have been implicated as industrial groundwater contaminants and deduced the isotopic content by analyzing the molecular ion region of the mass spectra. The HVOCs were analyzed by direct sampling of the headspace vapor over a dilute aqueous solution, which is designed to simulate a contaminated groundwater sample. The rapid headspace sampling and analysis allowed completion of the experiment by many lab classes per week. The impact of the lab was assessed using online surveys before and after the lab that queried student perceptions of their understanding, skills, and attitudes toward science and chemistry. The surveys showed noticeable gains in understanding and skills; however, few changes in attitudes were seen among students, the majority of whom already seemed committed to science and engineering careers and majors.

A novel microbial BOD biosensor developed by the immobilization of P. Syringae in micro‐cellular polymers

AbstractBACKGROUND: A biochemical oxygen demand (BOD) sensor, based on an immobilized Pseudomonas syringae in highly porous micro‐cellular polymer (MCP) in combination with a dissolved oxygen electrode, has been developed for the analysis of biodegradable organic compounds in aqueous samples. Microorganisms were immobilized in a molded MCP disk and a wastewater sample was injected into the biocomposite disk by a flow injection system. Dissolved oxygen (DO) changes as a measure of soluble BOD was read with a DO probe placed into a flow cell carrying biocatalytically activated disk.RESULTS: Optimal response of the MCP BOD sensor was obtained at pH 6.8 and 25 °C with a typical response time of 3–5 min for a 2 mm thick molded polymeric disk. The sensor showed detection linearity over the range 5–100 mg L−1 BOD5 (r2 > 0.99) at a flow rate of 0.6 mL min−1. The repeatability and reproducibility of the sensor response were found to be 3.08% and 7.77%, respectively. BOD values produced with this biosensor for various municipal and industrial wastewaters correlated well with those determined by the conventional 5‐day BOD test.CONCLUSION: This new biosensor was different from present amperometric BOD biosensor configurations in which the biocatalyst (microbial/enzymatic) is placed between cellulose and Teflon membranes installed on a DO probe. The use of a molded MCP disk coniainng microbial activity offers better stability and lifetime for commercial use in environmental monitoring. Copyright © 2008 Society of Chemical Industry

Fiber-packed needle for dynamic extraction of aromatic compounds

A fiber-packed needle was developed as a novel extraction device for gas-chromatographic analysis of trace organic compounds in aqueous samples. In the extraction device, a bundle of the polymer-coated filaments as the sorbent material was longitudinally packed into a specially designed needle. The extraction was made by pumping the aqueous sample solution into the needle extraction device, and the subsequent desorption process was carried out with a flow of desorption solvent through the needle in a heated gas chromatograph injector. The needle device showed an excellent thermal stability for repeated use without any deterioration of extraction performance, and no carryover effect was observed after the optimization of the desorption conditions. Additionally, the extraction efficiency of the fiber-packed needle could be enhanced by optimizing the number of packed filaments. The selectivity for various compounds could be also tuned using an appropriate combination of the fibrous medium and the coating polymer. The relative standard deviation for run to run was from 3.88 to 4.55% (n = 5), and that for needle to needle was 7.21% (n = 3), clearly suggesting a good repeatability of the needle extraction technique developed. Upon successful optimization of the extraction conditions, a rapid extraction of trace organic compounds from an aqueous sample matrix was successfully demonstrated, where each extraction process was completed within 10 min.

Analysis of semi-volatile organic compounds in aqueous samples by microwave-assisted headspace solid-phase microextraction coupled with gas chromatography–electron capture detection

The pretreatment technique of microwave-assisted headspace solid-phase microextraction (MA-HS-SPME) has been developed and studied for the extraction of semi-volatile organic compounds (SVOCs) in aqueous samples prior to chromatographic analysis. The optimum conditions for obtaining extraction efficiency, such as the extraction time, extraction temperature, addition of salts, and the ratio of sample to headspace volume parameters were investigated. Experimental results indicated that the proposed MA-HS-SPME technique attained the best extraction efficiency under the optimized conditions, i.e., irradiation of extraction solution (20 mL aqueous sample in 40 mL headspace vial with no addition of salt) under 30 W microwave power for 30 min at 70 °C. The detection was linear at 1–250 ng/L with correlation coefficient exceeding 0.997. The detection limits obtained were between 0.2–10.7 ng/L, repeatability range from 2 to 15%. Real water samples collected from known sites in southern Taiwan were analyzed using the optimized conditions.

Simple and Rapid Determination of Golf Course Pesticides by In-Tube Solid-Phase Microextraction Coupled with Liquid Chromatography

A simple and rapid method for the simultaneous determination of seven golf course pesticides in aqueous samples was developed by using in-tube solid-phase microextraction (in-tube SPME) coupled with liquid chromatography. In-tube SPME, in which the analytes were extracted from the sample directly into an open capillary column, is an extraction technique for organic compounds in aqueous samples. Although an open tubular capillary column with a thick film of polymer was used for the conventional in-tube SPME, we used a porous-layer open-tabular (PLOT) column in which there was a porous layer on the inner wall and has a larger surface area. A microsyringe pump equipped with a gastight syringe was employed to sequentially pump the sample solution through the capillary. The detection limits were from 0.9 to 4.1 ng ml-1. The calibration curves were linear in the range from 1 to 50 ng ml-1. We took a survey of seven golf course pesticides in several water samples by using the developed method.

Analysis of Phthalate Contamination in Infusion Solutions by Automated On-Line In-Tube Solid-Phase Microextraction Coupled with High-Performance Liquid Chromatography

Contamination of infusion solutions with phthalates was analyzed, and its origin was determined. Phthalates were determined by on-line in-tube solid-phase microextraction coupled with high-performance liquid chromatography (in-tube SPME-HPLC) with UV detection. In-tube SPME is an extraction technique for organic compounds in aqueous samples, in which analytes are extracted from the sample directly into an open tubular capillary by repeated draw/eject cycles of sample solution. The infusion solutions were used without any pretreatment, and the phthalates in these solutions were automatically analyzed by the on-line in-tube SPME-HPLC system. The limits of detection of phthalates in the infusion solutions were 1-10 ng/mL. With a few exceptions, the recoveries of phthalates added to the infusion solutions were above 80%. Di-n-butyl phthalate (DBP) was detected at a concentration of 7-60 ng/mL in most infusion solutions in plastic containers but was not detected in those in glass bottles. On the other hand, no other phthalates were detected in infusion solutions in either plastic or glass containers. Large amounts of DBP were detected in the adhesive used to affix the paper labels to the plastic bottles and bags, but not in the plastic containers themselves. Furthermore, DBP was shown to be readily eluted from the adhesive into water and alcohol and easily pass through the plastic. These results indicated that the source of the DBP was the adhesive used to affix the paper labels, and DBP contaminated the infusion solutions by passing through the plastic. The in-tube SPME-HPLC method is simple and rapid and provides a useful tool for the screening and determination of phthalate contamination in infusion solutions.

Short-term BOD (BOD st) as a parameter for on-line monitoring of biological treatment process : Part I. A novel design of BOD biosensor for easy renewal of bio-receptor

A novel design of a biochemical oxygen demand (BOD) biosensor has been developed for on-line monitoring of easily biodegradable organic compounds in aqueous samples. The biological recognition element of the sensor could be easily renewed by injecting new bacterial paste without disassembling the sensor system. The sensor measurements were carried out in the initial-rate mode using a flow injection (FI) system, resulting in 60 s for one sample analysis followed by a recovery time less than 10 min. The sensor performance achieved showed a wide detection linearity over the range of 5–700 mg BOD 5·l −1 and a generally good agreement between the BOD values estimated by the biosensor and the conventional 5-day test. Furthermore, the precision test was in the control range (i.e. repeatability ≤ |±7.5%|, reproducibility ≤ |±7.3%|). The sensor could be used over 1 week in continuous test, however, the best performance was found within the first 24 h where standard deviation of the sensor response was ±2.4%. The design of the sensor allows easy and fast renewal of the cells used as sensing elements. Replacement of biological recognition element and calibration of the sensor responses can be performed in a rather simple procedure on a daily regular basis. By using a mixed culture as the bio-receptor, one gets a sensor that reacts to a wide range of substrates. The new sensor construction will thus allow fast and convenient replacement of the bio-receptor and on-line assay of a broad range of substrates. This makes the sensor being an interesting and promising candidate for on-line monitoring of biological treatment process.

Automated high-capacity sorption probe for extraction of organic compounds in aqueous samples followed by gas chromatographic analysis

An automated high-capacity sorption device for GC analysis of ultra trace components has been developed. The scope of the presented technique was to combine the simplicity of solid-phase microextraction (SPME) with the high extraction efficiency of the stir bar sorptive extraction technology. Sorptive extractions of water samples were performed using polydimethylsiloxane (PDMS) rubber tubing (120 μl) mounted onto a glass rod. The sampling procedure was carried out by a robotic autoinjector. Since the setup is fully automated, unattended and precise time-controlled extraction of samples is possible and makes quantitation with non-equilibrium extractions feasible. The sorption probes are easy to exchange, which facilitates off-line/in-field sampling. The system was evaluated with a test mixture of 44 environmentally hazardous compounds. Detection limits were found to be in the sub-ppt region. The performance of the system was demonstrated with the analysis of polycyclic aromatic hydrocarbons in urban snow.

Miniaturized and automated sample pretreatment for determination of PCBs in environmental aqueous samples using an on-line microporous membrane liquid-liquid extraction-gas chromatography system.

A new, fast, and automated sample pretreatment technique for determination of lipophilic organic compounds in aqueous samples has been developed and applied to the determination of polychlorinated biphenyls (PCBs) in environmental river water. It is based on miniaturized microporous membrane liquid-liquid extraction coupled on-line to gas chromatography (GC) with electron capture detection. The heart of the system that simultaneously connects the sample pretreatment step to the final GC analysis has been named the extracting syringe (ESy). The ESy carries a miniaturized membrane extraction card attached to an electrically and mechanically designed installment and is mounted directly over a GC injector for fully automated injection of the extract. A method was developed to extract 10 PCB congeners from 1-mL water samples (after addition of 40% acetonitrile) with an extraction time of 10 min. The optimized methodology showed good linearity (in the dynamic concentration range of 5 ng L(-)(1)-1 microg L(-)(1)), enrichment factors of 33-40 times, repeatable extractions (RSD 2-5%, n = 4), and low detection limits (2-3 ng L(-)(1)). Acetonitrile had to be added to the samples in order to overcome the influence of PCB adsorption on the repeatability of extraction and enrichment and to minimize the overall memory effect (OME). OME and carryover depended not only on the concentration of the organic solvent added to the sample and that used in the washing procedure but also on whether the extracting card was changed or not. When an optimized washing procedure was applied, the OME was approximately 0.2% at high concentrations (i.e., 1 microg L(-)(1)). When each extraction took place in a new extraction card, no OME was detected. Additionally, no significant adsorption onto glass surfaces or a matrix effect on extraction was noticed. The main features of this methodology are good extraction repeatability, low detection limits at short extraction time, and the unsurpassed characteristic of no detectable OME in the entire system when each sample is processed in a new card. The total consumption of organic (nonchlorinated) solvents is less than 5 mL per sample.

Construction and validation of an automated spray-and-trap gas chromatograph for the determination of volatile organic compounds in aqueous samples

An automated spray-and-trap (ST) chromatographic system was constructed for fast and efficient extraction of volatile organic compounds (VOCs) in aqueous samples with the capability to be deployed in the field for unattended continuous monitoring of surface or ground water. This system was built upon a commercial gas chromatograph with full automation capability using self-developed hardware and software. For sample analysis, fine droplets of the aqueous solution were generated in the extraction chamber by pressure expansion of a clean air stream through a spray nozzle. A portion of the VOCs distributed into the gas phase was retained by a multi-sorbent micro-trap kept at ambient temperature. Flash heating of the sorbent trap desorbed the enriched VOCs onto the gas chromatography (GC) with flame ionization detection (FID) for hydrocarbons or electron-capture detection (ECD) for halocarbons. In order to validate the performance of the ST method, it was compared with a more conventional method, i.e., a purge-and-trap (PT), by analyzing a serious of standard solutions containing benzene, toluene, ethylene, and o-, m-xylenes. Using a purge-and-trap method as a reference for complete extraction, the ST method showed less sensitivity. Extraction recoveries are in consistent with Henry’s law constants. To test response time the ST–GC–ECD was periodically switched between tap and underground waters. Negligible carry-over of halogenated species and reproducibility better than 2% relative standard deviation (R.S.D.) can be achieved regardless of large concentration difference between the two sources, thus demonstrating applicability of the ST system for on-site monitoring.

Determination of daidzein and genistein in soybean foods by automated on-line in-tube solid-phase microextraction coupled to high-performance liquid chromatography

An automated on-line method for the determination of the isoflavones, daidzein and genistein, was developed using in-tube solid-phase microextraction coupled to high-performance liquid chromatography (in-tube SPME–HPLC). In-tube SPME is a new extraction technique for organic compounds in aqueous samples, in which analytes are extracted from the sample directly into an open tubular capillary by repeated draw/eject cycles of sample solution. Daidzein, genistein and their glucosides tested in this study were clearly separated within 8 min by HPLC using an XDB-C 8 column with diode array detection. In order to optimize the extraction of these compounds, several in-tube SPME parameters were examined. The glucosides daidzin and genistin were analyzed as aglycones after hydrolysis because the glucosides were not concentrated by in-tube SPME. The optimum extraction conditions for daidzein and genistein were obtained with 20 draw/eject cycles of 40 μl of sample using a Supel-Q porous layer open tubular capillary column. The extracted compounds were easily desorbed from the capillary by mobile phase flow, and carryover was not observed. Using the in-tube SPME–HPLC method, the calibration curves of these compounds were linear in the range 5–200 ng/ml, with a correlation coefficient above 0.9999 ( n=18), and the detection limits ( S/ N=3) were 0.4–0.5 ng/ml. This method was successfully applied to the analysis of soybean foods without interference peaks. The recoveries of aglycones and glucosides spiked into food samples were above 97%.