Keywords: Direct Thermal Desorption, Volatiles in Soil, PCB´s and PAH´s, Trace Analysis, Capillary GC/MS, Cooled Injection System CIS, PTV
Thermal desorption is a well known technique for the analysis of volatile organic contaminants in air and normally employs adsorption on porous polymers. This operation principle can also be adapted for the direct thermal desorption of volatiles within a wide boiling range directly from soil samples. In this paper the potential of a newly developed thermal desorption system for direct desorption and analysis of volatiles from soil samples is discussed and demonstrated. It will be shown that the combination of thermal desorption with an intermediate cryofocusing step in the inlet liner of a cooled injection system (CIS/PTV) is a reliable and fast method for the determination of volatiles even with such high boiling points associated with PAHs and PCBs
Keywords: Stir Bar Sorptive Extraction - SBSE, GERSTEL Twister, Environmental Analyses
For the analysis of organic compounds in aqueous environmental matrices several sample preparation methods are used. Volatile organic compounds can be analyzed using (static) headspace, purge and trap or liquid-liquid extraction. Semi-volatiles are analyzed after liquid-liquid extraction or solid phase extraction (SPE). During the past years, miniaturization has become a dominant trend in analytical chemistry. Typical examples of miniaturization in sample preparation techniques are micro liquid-liquid extraction (in-vial extraction), ambient static headspace and disk cartridge SPE. In combination with state-of-the-art analytical instrumentation, this resulted in faster analysis, higher sample throughput, lower solvent consumption, less manpower in sample preparation while maintaining or even improving sensitivity.
Keywords: PAH, SPME, Stir Bar Sorptive Extraction, SBSE, GERSTEL Twister, Thermal desorption, GC-MS, PCB
Two extraction techniques that avoid solvent consumption and cut down the sample preparation to a minimum - Solid Phase MicroExtraction (SPME) and Stir Bar Sorptive Extraction (SBSE) – were compared on the basis of their reproducibility and sensitivity for 16 US EPA PAH compounds.
Keywords: Soil Analysis, EPA SW-846, Method 8270, Stir Bar Sorptive Extraction, SBSE, SVOC, Accelerated Solvent Extraction, ASE
The analysis of contaminated soil and sludge samples for semi-volatile organic compounds (SVOC) has traditionally been performed using gas chromatography/mass spectrometry (GC/MS) (EPA SW-846, Method 8270). This method relies on the extraction of contaminants from the samples utilizing a variety of organic and chlorinated solvents. This study shows the effective use of a Dionex Accelerated Solvent Extractor 200 (ASE) along with Stir Bar Sorptive Extraction (SBSE) with methanol replacing the undesirable chlorinated solvents.
Keywords: Stir Bar Sorptive Extraction, SBSE, Twister, PAHs
In this study we describe the possibility of automation of the SBSE desorption step with direct transfer of the liquid extract to HPLC by use of the GERSTEL- MultiPurpose autosampler MPS (Twister Back-Extraction). For this purpose the MPS was equipped with a temperature programmable agitator and a special software. Using this procedure, after extraction of water samples by SBSE, the only manual step is the removal of stir bars from the sample vial and transfer to 250 μL glass inserts placed inside 2 mL autosampler vials. The MPS then adds the ACN/water mixture to the stir bar, transports the vial to the agitator, where it is agitated at a defined temperature during the preset desorption time and finally withdraws an aliquot of the extract, which is injected into the HPLC.
Keywords: Membrane Extraction, Triazines, VOCs, Large Volume Injection, LVI
Typically membrane-assisted solvent extraction (MASE) is carried out off-line in a vial, from which the organic extract is transferred to a sample vial followed by large-volume injection (LVI). In this study the extraction device for the membrane-assisted solvent extraction was modified for use with a conventional 20 mL headspace vial. For this purpose a tube of nonporous polypropylene membrane was sealed at one end to produce a membrane pouch, which could be inserted into the vial with the aid of a stainless steel adapter. 15 mL of the aqueous sample and 500 μL of solvent was used for the extraction procedure. A GERSTEL MultiPurpose autosampler (MPS) was used to place the solvent in the membrane pouch, followed by extraction in a heated agitator. After extraction, the MPS performed LVI directly from the extraction vial.
Keywords: Membrane Extraction, Waste Water
A procedure to analyze several semi-polar, nitrogen-containing compounds in untreated industrial waste water by means of membrane extraction is described. The selected analytes cover a broad range of volatility and can be extracted with either chlororform or diisopropyl ether. Recoveries are 40 – 110% for test solutions containing approximately 250 μg/L.
Keywords: Dual Stir Bar Sorptive Extraction (Dual SBSE), Thermal Desorption, Fast GC/MS, Low Thermal Mass Column Heater, LTM, Pesticide Multiresidues, Aqueous Samples
A method for fast screening of pesticide multi-residues in aqueous samples using dual stir bar sorptive extraction (dual SBSE) - thermal desorption (TD) - fast GC/MS has been developed. Recovery of 82 pesticides – organochlorine, carbamate, organophosphorous, pyrethroid and others – for the SBSE. The method showed good linearity (r2 > 0.9900) and high sensitivity (limit of detection:< 10 ng/L) for most of the target pesticides. The method was applied to the determination of pesticides at ng/L levels in river water and brewed green tea.
Keywords: Atmospheric nanoparticles, Thermal Extraction, TE, Comprehensive two-dimensional gas chromatography (GC x GC), High resolution time-of-flight mass spectrometry, HRTOF-MS
A method for characterization of airborne particles including the nanoparticles fraction with a diameter of 29-58 nm in roadside atmosphere is described. The method consists of thermal extraction (TE) and comprehensive two-dimensional gas chromatography (GC x GC) with novel detection capabilities, including high resolution time-of-flight mass spectrometry (HRTOF-MS), and simultaneous selective and mass spectrometric detection with a nitrogen phosphorous detector (NPD) and a quadrupole mass spectrometer (qMS).
Keywords: Low Thermal Mass, LTM, Fast GC-ECD, SPE, PCB, Waste Oil
A fast SPE-GC-ECD method for the analysis of PCBs in waste oil was developed. A complete profile was obtained following SPE with a 12 minute GC run-time using a low thermal mass column heater (LTM). Full automation of the sample preparation and analysis (except sample weigh-in) enables a daily throughput of 100 samples. A wide range of concentrations can be determined using a dedicated column and Electron Capture Detection (ECD).
Keywords: Dynamic Headspace, Gas Chromatography, Replaceable Traps
In this study we describe the use of an automated dynamic headspace sampler for determination of volatiles in aqueous samples. This sampler uses a two-needle design to flush the headspace of standard headspace vials onto replaceable adsorbent traps that can be thermostatted to optimize analyte recovery and control interference from water vapor. Following analyte transfer, the adsorbent traps can be automatically dry purged to further eliminate water before introduction into the integrated thermal desorber. This design enables automated optimization of trapping conditions including choice of adsorbent, and has the potential for automated internal standard addition and automated calibration. To illustrate the versatility of the DHS system, examples of the determination of trace levels of volatile organic compounds (VOCs) in aqueous samples are shown. Detection limits and linearity are discussed in the following.
Keywords: Sequential Stir Bar Sorptive Extraction, Sequential SBSE, Thermal Desorption, GC/MS, Organic Pollutants, Water Analysis
A novel stir bar sorptive extraction (SBSE) procedure - "Sequential SBSE" was developed. Compared to conventional SBSE, sequential SBSE provides more uniform enrichment over the entire polarity/volatility range for organic pollutants at ultra-trace levels in water. Sequential SBSE consists of a SBSE performed sequentially on a 5-mL sample first without modifier using one stir bar, then on the same sample after addition of 30 % NaCl using a second stir bar. The method showed good linearity (r2 > 0.9900) and high sensitivity (limit of detection: < 10 ng/L) for most of the model compounds even with the scan mode in the MS. The method was successfully applied to screening of pesticides at ng/L level in river water samples.
Keywords: 2-Methyl Isoborneol, Geosmin, Haloanisole, Drinking Water, Dynamic Headspace, Selectable 1D/2D, GC/MS, Olfactometry
A method for the determination of trace amounts of off-flavor compounds such as 2-methyl isoborneol (MIB), geosmin and 2,4,6-trichloroanisole (TCA) in drinking water is described based on dynamic headspace coupled to selectable one dimensional or two-dimensional gas chromatography - mass spectrometry with simultaneous olfactory detection(DHS-1D/2D-GC-O/MS).
Keywords: Automated Evaporation, mVap, SPE, DPX
Having to reach ever lower limits of detection is a daily challange in modern laboratories. In order to succeed in obtaining sufficiently sensitive analysis methods, sample preparation techniques such as Solid Phase Extraction (SPE) or Liquid-Liquid Extraction are often used as concentration steps. The concentration factor achieved in these cases depends on the amount of solvent used for analyte elution from the SPE cartridge or for liquid extraction. Following the extraction step, further concentration of analytes can be achieved by reducing the amount of solvent left in the extract. This is typically achieved by evaporation. Such a concentration step can contribute significantly to improved limits of detection for the overall analytical method. For the evaporative concentration step, commercially available rotary evaporators as well as custom solutions are widely used. These are mainly stand-alone systems for manual operation. The GERSTEL MultiPosition Evaporation Station (mVAP) in combination with the GERSTEL MultiPurpose Sampler (MPS) now offers fully automated concentration of sample extracts. The system enables complete automation of all sample preparation steps including introduction to an a LC or GC system. The evaporation is controlled by controlling the applied vacuum leading to reproducible results independent of the solvent used. The user can also benefit from a real increase in laboratory efficiency, since batches of samples can be processed automatically overnight. In this Application Note we demonstrate the performance of the mVAP and compare the results with those obtained using a commercially available evaporation system based on nitrogen flow.
Keywords: Thermal Desorption, Air Analysis, VOC, JHAP
System performance of the GERSTEL TDS in conjunction with an Agilent GC/MSD system was tested using a 43 component gas calibration mixture which was developed for the Japanese Hazardous Air Pollutants (JHAP) monitoring method. A five point calibration curve was obtained for each compound (2-20 ppb@1L) with an average correlation coefficient of 0.996. Twelve replicate analyses of the mixture, where each component was present at 20 ppb@1L, gave an average percent relative standard deviation (%RSD) of 4.6.