Selective extraction of polychlorinated biphenyls from dairy products using steam distillation–solvent extraction at normal pressure

On-Line Coupling of Simultaneous Distillation-Extraction Using the Likens-Nickerson Apparatus with Gas Chromatography

Simultaneous distillation-extraction (SDE) using the Likens-Nickerson apparatus is a convenient technique used to isolate volatile organic compounds (VOCs) from complex liquid matrices. The technique combines steam distillation with solvent extraction. While analytical extractions are normally followed by off-line separation/detection, it is advantageous to couple extractions on-line with separation and detection systems that are employed in the same analytical workflow. Here, we have coupled the Likens-Nickerson apparatus on-line with a gas chromatograph hyphenated with a mass spectrometer. For that purpose, we have devised an automated liquid transfer setup comprising a peristaltic pump, control unit, customized transfer vial with a drain port, and an autosampler arm to deliver liquid extract aliquots at defined time points. The on-line SDE-GC/MS system enables one to record real-time extraction profiles. These profiles reveal extraction kinetics of various VOCs present in the extracted samples. The data sets were fitted with the first order kinetic equation to obtain numeric values characterizing the extraction process (rate constants ranging from 0.21 to 0.01 min^-1 for the ethyl esters from C₆ to C₁₉). A comparison of on-line and off-line results reveals that the on-line system is more dependable, while the off-line analysis leads to artifacts. To demonstrate the operation of the on-line SDE-GC/MS system, we performed analyses of selected real samples (beer). The real-time data sets revealed extraction kinetics for VOCs present in these samples. The devised extraction-analysis system allows the analysts to make an evidence-based decision on the extraction time for different groups of analytes in order to maximize extraction yield and minimize analyte losses.

Efficient remediation of crude oil-contaminated soil using a solvent/surfactant system

Crude oil contaminated soil has been widely recognized to constitute a major environmental issue due its adverse effects on human health and ecological safety. The main objective of this study is to explore the possibility of using an ex situ solvent/surfactant washing technique for the remediation of crude oil-contaminated soil. Three organic solvents (methanol, acetone, and toluene) and one surfactant (AES-D-OA) were employed to form three kinds of solvent/surfactant systems, and utilized to evaluate the desorption performance of crude oil from soil. Natural soil, crude oil-contaminated soil, and after-remediation soil were characterized by SEM, EDX, FT-IR, and contact angle. The ability of solvent/surfactant systems to remove crude oil from soil was determined as a function of solvent polarity, mass ratio of solvent to surfactant, temperature, and ionic strength. The removal of crude oil by the toluene/AES-D-OA system was found to be more effective than the other systems. At a high toluene ratio, more than 97% of crude oil could be removed from contaminated soil. Crude oil removal efficiency was also found to increase with rising temperature or increasing ionic strength appropriately. Experimental results suggested that, compared to conventional surfactant-aided remediation, the combined utilization of surfactant and solvent achieved superior results for crude oil removal because of their similar compositions and structures in terms of aromaticity and polarity.

Efficient remediation of crude oil-contaminated soil using a solvent/surfactant system

Crude oil contaminated soil has been widely recognized to constitute a major environmental issue due its adverse effects on human health and ecological safety. The main objective of this study is to explore the possibility of using an ex situ solvent/surfactant washing technique for the remediation of crude oil-contaminated soil. Three organic solvents (methanol, acetone, and toluene) and one surfactant (AES-D-OA) were employed to form three kinds of solvent/surfactant systems, and utilized to evaluate the desorption performance of crude oil from soil. Natural soil, crude oil-contaminated soil, and after-remediation soil were characterized by SEM, EDX, FT-IR, and contact angle. The ability of solvent/surfactant systems to remove crude oil from soil was determined as a function of solvent polarity, mass ratio of solvent to surfactant, temperature, and ionic strength. The removal of crude oil by the toluene/AES-D-OA system was found to be more effective than the other systems. At a high toluene ratio, more than 97% of crude oil could be removed from contaminated soil. Crude oil removal efficiency was also found to increase with rising temperature or increasing ionic strength appropriately. Experimental results suggested that, compared to conventional surfactant-aided remediation, the combined utilization of surfactant and solvent achieved superior results for crude oil removal because of their similar compositions and structures in terms of aromaticity and polarity.

Water CAs and EDX analysis of (a) natural soil, (b) crude oil-contaminated soil, and (c) after-remediation soil.

Simultaneous distillation-extraction of high-value volatile compounds from Cistus ladanifer L

The present paper describes a procedure to isolate volatiles from rock-rose (Cistus ladanifer L.) using simultaneous distillation-extraction (SDE). High-value volatile compounds (HVVC) were selected and the influence of the extraction conditions investigated. The effect of the solvent nature and extraction time on SDE efficiency was studied. The best performance was achieved with pentane in 1 h operation. The extraction efficiencies ranged from 65% to 85% and the repeatability varied between 4% and 6% (as a CV%). The C. ladanifer SDE extracts were analysed by headspace solid phase microextraction (HS-SPME) followed by gas chromatography with flame ionization detection (GC-FID). The HS-SPME sampling conditions such as fiber coating, temperature, ionic strength and exposure time were optimized. The best results were achieved with an 85 microm polyacrylate fiber for a 60 min headspace extraction at 40 degrees C with 20% (w/v) of NaCl. For optimized conditions the recovery was in average higher than 90% for all compounds and the intermediate precision ranged from 4 to 9% (as CV %). The volatiles alpha-pinene (22.2 mg g(-1) of extract), 2,2,6-trimethylcyclohexanone (6.1 mg g(-1) of extract), borneol (3.0 mg g(-1) of extract) and bornyl acetate (3.9 mg g(-1) of extract) were identified in the SDE extracts obtained from the fresh plant material.

Determination of selected polycyclic aromatic hydrocarbons and oxygenated polycyclic aromatic hydrocarbons in aerosol samples by high-performance liquid chromatography and liquid chromatography?tandem mass spectrometry

Fine and ultrafine particles are probably responsible for numerous health effects, but it is still unclear whether and to what extent the particle itself or organic compounds adsorbed or condensed on the particle are responsible for the effects observed. One important class of particle-bound substances are the polycyclic aromatic hydrocarbons (PAH) and their oxygenated derivatives. To improve the tools used for chemical characterization of particulate matter analytical methods for the determination of PAH and oxygenated PAH in aerosol samples of different origin have been developed and optimized. PAH on high-volume filters and on soot aerosols were analyzed by using accelerated solvent extraction for extraction and high-performance liquid chromatography with fluorescence detection for separation and quantification. Total PAH concentrations were in the range 0.3-9.3 ng m(-3). For analysis of selected oxygenated PAH on high-volume filters a liquid chromatography-tandem mass spectrometric method was developed and optimized. Preliminary investigations showed that oxygenated PAH at pg m(-3) concentrations can be determined.

Remediation of contaminated soil by a solvent/surfactant system

This study investigates a new approach using a solvent/surfactant-aided soil-washing process to improve the performance of conventional surfactant-aided soil remediation. Three surfactants (Brij 35, Tween 80, and SDS) and three organic solvents (acetone, triethylamine, and squalane) were used to evaluate the desorption performances of 4,4'-dichlorobiphenyl (DCB) out of three soils with different sorption characteristics. The performance improvement is likely due to better dissolution of the hydrophobic contaminants from the soil assisted by the solvent, and the formation of solvent-incorporated surfactant micelles, which increases both the size (i.e. capacity) and affinity of micelles for more effective contaminant extraction. The foc of soils were found to be important in determining the performance of a solvent/surfactant-aided soil-washing process. Judging from the experimental data and as verified by the two constants in the proposed soil-washing model, as the organic solvent is coexisting with the surfactant micelles, both the marginal soil-washing performance (right after the use of a very small amount of solvent compared to that of none) and the final soil-washing capacity are increased compared to those of a pure surfactant-aided washing process.

Microwave-assisted steam distillation for simple determination of polychlorinated biphenyls and organochlorine pesticides in sediments

A novel sample extraction technique for polychlorinated biphenyls (PCBs) and organochlorine pesticides (OCPs) analysis using microwave-heating device is developed. In this study, microwave-assisted extraction (MAE) and steam distillation techniques were combined. Desorption of the anatytes from solid matrixes was accelerated with water vapor which was generated by microwave irradiation. A sample holder in a commercial microwave extraction cell kept the sample from direct contact with the organic solvent for analytes trapping during the treatment process. Therefore, relatively clean extracts were obtained with small amount of solvents. Without any cleanup steps, the obtained extract could be analyzed with gas chromatograph/mass spectrometers (GC/MS). Six PCB congeners (PCB15, 28, 70, 101, 180, 194, 209) and three OCPs (gamma-HCH, 4,4'-DDE, 4,4'-DDD) in two marine sediment samples (a sediment collected from a bay of Kyusyu Island, Japan, and a certified reference material NIST SRM1944) were analyzed by using this microwave-assisted steam distillation (MASD) technique and another extraction method (exhaustive steam distillation, MAE, and Soxhlet extraction); and comparisons of the results are shown in this report. Although recovery yields of highly chlorinated biphenyls (PCB180, 194, 209) and relatively polar OCPs (gamma-HCH, 4,4'-DDD) were low (30-60%) compared with other analytes (PCB15, 28, 70, 101, 4,4'-DDE; recovery, 80-100%), use of isotope labeled internal standards for the MASD technique gave comparable results with the values obtained by other extraction methods and the certified values in the samples.

High extraction efficiency for POPs in real contaminated soil samples using accelerated solvent extraction

Systematic investigations were performed to study the dependence of the extraction efficiency of persistent organic pollutants (POPs), including chlorobenzenes, HCH isomers, DDX, PCB congeners, and PAHs, on the accelerated solvent extraction (ASE) operating variables solvent and temperature. Mixed soil samples from two locations with considerable differences in soil properties and contamination in the Leipzig-Halle region (Germany) were used. The objective was to optimize ASE for the extraction of POPs from real soil samples and to improve on the results achieved with Soxhlet extraction (SOX). Solvents with differing polarities were tested. Quadruple and triple determinations were performed on the two soils, respectively, between 20 and 180 degrees C in 20 degrees C steps. All the results were compared with those obtained by SOX, as well as, in some cases during preliminary studies, by ultrasonic extraction (USE). In ASE, the optimum conditions proved to be two extraction steps at 80 and 140 degrees C (average RSD 10.7%) with three static cycles (extraction time 35 min) using toluene as solvent and at a pressure of 15 MPa. Owing to the superior analyte/matrix separation by ASE, in many cases for real soil samples analytical values better by up to 1 order of magnitude or even more were obtained compared to SOX results.