Gerstel: Intelligent Automation for GC/MS and LC.MS

Thermal Desorption


Extractables and Leachables Analysis of IV Bag Systems using Direct Thermal Extraction of the Materials and Stir Bar Sorptive Extraction of Aqueous Solutions coupled with Thermal Desorption Gas-Chromatography with Unit Mass and High Resolution Mass Spectrometric Detection

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Keywords: Pharmaceutical, Packaging, IV bags, intravenous delivery systems, Extractables, Leachables, Single Quad Mass Spectrometry, Time-of-Flight Mass Spectrometry, Stir Bar Sorptive Extraction (SBSE), Thermal Desorption, Thermal Extraction, Gas Chromatography

ABSTRACT

IV bag components were analyzed for extractables using direct thermal desorption/thermal extraction combined with a unit mass resolution GC/MSD system. The results were compared to those obtained for leachables by stir bar sorptive extraction of an aqueous simulant stored in the exact same type of IV bag, again combined with GC/MS determination of the leached compounds. In addition, the high resolution GC/Time of Flight (TOF) mass spectrometer was used to verify or disprove some of the MSD findings.


Comparison of Standard Liquid Extraction and Direct Thermal Desorption GC/MS Techniques for the Analysis of Charcoal Filters used for Indoor Air Purification in a PCB Contaminated Building

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Keywords: Direct Thermal Desorption, Air Charcoal Filters, Air Filtration, PCBs in Air, Trace Analysis, Capillary GC-MS, Cooled Injection System CIS, PTV

ABSTRACT

Many buildings constructed from prefabricated elements are widely contaminated with PCB originated in e.g. elastic sealants which act as permanent sources for several years. Indoor air filtration is part of a restoration strategy for these buildings using activated carbon filter media [1]. The analysis of PCBs trapped on these filters is usually carried out using standard liquid extraction followed by GC/MS analysis of the extract. This standard technique will be compared to direct thermal desorption of the filter material in combination with cryo-focusing in the liner of a cooled injection system, followed by temperature programmed sample transfer to the analytical column. It will be shown that direct thermal desorption is a reliable and fast method for the determination of PCBs in air charcoal filters without requiring any sample pretreatment.


Direct Thermal Desorption GC/MS Analysis of Automotive Air Charcoal Filters

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Keywords: Direct Thermal Desorption, Air Charcoal Filters, Volatile Contaminants in Air, Capillary GC-MS, Cooled Injection System CIS, PTV

ABSTRACT

The analysis of volatile organic contaminants in air trapped on an automotive air charcoal filter is usually carried out using standard liquid extraction followed by GC/MS analysis of the extract. This standard technique will be compared to direct thermal desorption of the filter material in combination with cryo-focusing in the liner of a cooled injection system, followed by temperature programmed sample transfer to the analytical column. It will be shown that direct thermal desorption is a reliable and fast method for the determination of volatiles in automotive air charcoal filters without requiring any sample pretreatment


Breath Analysis in Patients with Metabolic Disorders: GC/MS Analysis with a Combined Thermal Desorption - Cooled Injection System CIS

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Keywords: Breath Analysis, Thermal Desorption, Cooled Injection System CIS, GC/MS, Metabolic Disorders

ABSTRACT

The combination of a new thermal desorption module with a cooled injection system (TDS-2,CIS-3, GERSTEL) now provides a powerful thermal desorption system for direct analysis of volatile trace compounds in gaseous, liquid and solid samples. As a cooled injection system is used for the cryofocusing of the desorbed volatiles the GC/MS system still can be used for the regular analysis of liquid samples. Breath samples were collected in a 1 liter tedlar bag and transferred onto a freshly conditioned thermal desorption tube filled with Tenax. Breath analysis were performed from patients with various metabolic disorders, smoking and non smoking healthy volunteers. A MS-library was used to identify 72 components.


Analysis of Plasticizers in Medical Products by GC/MS with a Combined Thermal Desorption/Cooled Injection System, CIS

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Keywords: Direct Thermal Desorption, GCMS, Plastizicer, Di-2-ethylhexylphthalate (DEHP), 4-Heptanone, 2-Heptanone, Cyclohexanone

ABSTRACT

The combination of a new thermal desorption module with a cooled injection system (TDS-2,CIS-3, GERSTEL) now provides a powerful thermal desorption system for direct analysis of volatile trace compounds in gaseous, liquid and solid samples. As a cooled injection system is used for the cryofocusing of the desorbed volatiles the GC/MS system still can be used for the regular analysis of liquid samples. Plasticizers can usually be analyzed by liquid extraction with alcohol/water, but special care has to be applied not to use contaminated solvents. Direct analysis of plastics by thermal desorption saves time and avoids cross contamination. Many containers for intravenous solutions are made with plasticized polyvinyl chloride, the common form of which is di-2-ethyl hexyl phthalate (DEHP). Extraction of DEHP into blood and plasma stored in such plastic containers can occur, and harmful effects of DEHP in the human body consequently have been suggested. We therefore analyzed 30 plastic tubing samples which are used for various invasive techniques in medicine.


Characterization of Biogenic Emissions by Online Thermal Desorption Gas Chromatography/Mass Spectrometry

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Keywords: Biogenic, Plant Stress, GC/MS

ABSTRACT

The novel GERSTEL Online TDS G was developed to allow fast, reliable and continuous analysis of airborne compounds. For the described application the total analysis time, including GC run time, is about 1 hour. Sampling is done in parallel with gas chromatographic analysis.


Comparison of the Sensitivity of Static Headspace GC, Solid Phase Microextraction, and Direct Thermal Extraction for Analysis of Volatiles in Solid Matrices

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Keywords: Headspace, Solid Phase Microextraction, SPME, Thermal Desorption, Herbs, Coffee, Tea, Polyethylene ABSTRACT

ABSTRACT

The analysis of volatiles in solids is a common analytical problem. Examples include volatile aroma compounds in foods and plant materials (coffee, tea, and herbs), residual fragrances from soaps and fabric softeners on textiles, and volatiles in polymer resins, films and plastic products. Several techniques are available that allow direct analysis of the volatiles in a variety of solid matrices with little or no sample preparation. Static headspace GC (HS-GC) is probably the most commonly applied technique for analysis of volatiles in solids. Direct thermal desorption (TDS), sometimes referred to as dynamic headspace analysis, and Solid Phase Microextraction (SPME) are alternative techniques that can now be automated. The relative sensitivity of these techniques, and the strengths and limitations of each when applied to a variety of solid matrices should be considered when choosing the most appropriate approach for a new analysis. Until now a direct comparison of these techniques for a variety of samples on equivalent instrumentation has been difficult to find. Samples from the classes mentioned above were analyzed using HS-GC, SPME and TDS sample introduction into the same HP 6890 GC instrument. Column and detector conditions were maintained the same for all sample introduction methods. Generally, sensitivity of static headspace sampling was 10-50x lower than SPME sampling. Direct Thermal Extraction was found to be 50-100x higher sensitivity than SPME sampling. Besides sensitivity, advantages and limitations of the three sample introduction techniques for dealing with various sample types (low vs. high boilers, wet samples) should be considered before choosing an analytical approach.


Analysis of Wet Samples by Direct Thermal Desorption GC

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Keywords: Thermal Desorption, Tenax TA™, Sample drying, Herbs, Peppers

ABSTRACT

The analysis of volatiles in solids is a common analytical problem. Examples include volatile aroma compounds in foods (coffee, tea, herbs), residual fragrances from soaps and fabric softeners on textiles, and volatiles in polymer resins, films and plastic products. When high sensitivity analysis is needed, many of these sample types can be analyzed by direct thermal desorption with cryotrapping before the GC column. A wide variety of sample types can contain significant levels of water. This poses significant challenges when doing direct thermal desorption and cryotrapping for analysis of volatiles, since water can accumulate and freeze in an inlet or at the head of a column. Introduction of significant levels of water into the GC column can degrade chromatographic performance and shorten column lifetime. There are several strategies that are useful to reduce the introduction of water into a GC when doing thermal desorption. These range from offline thermal extraction with trapping of volatiles on adsorbent beds to incorporating drying steps into the thermal desorption process itself. Estimating the amount of water that can be eliminated with each of these approaches is a challenge. Volatiles in solid samples containing up to 90% water were analyzed by direct thermal desorption incorporating different drying strategies. Off line thermal extraction utilizing Tenax TA™ adsorbent was the most effective approach for eliminating large amounts of water while effectively retaining low boiling analytes. Small amounts of water (tens of milligrams) can be eliminated from samples by using Tenax TA™ packed inlet liners cooled to 20-40°C. General guidelines for choosing appropriate steps for eliminating different levels of water are summarized.


Volatile Organic Compounds from Adhesives and their Contribution to Indoor Air Problems

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Keywords: Indoor Air Pollution, Thermal Desorption, Adhesives, Floor Coverings, Emissions, Bromophenol

ABSTRACT

Carpets for office use in most cases are applied with water-based adhesives. During the last decade the complaints about odors and emission of volatile organic compounds from these fitted carpets have increased dramatically, causing a major problem for indoor air quality. In a series of investigations it has been established that in many cases the adhesives used were the primary cause of complaints. This is initially surprising, since usually solvent free water-based dispersion adhesives were used. This paper describes the analytical approach of analyzing a broad variety of volatile compounds within a wide boiling point range with thermal desorption GC/MS.


Flavor Profiling of Different Olive Oils with Rancidity-Monitoring by Thermal Extraction GC/MS

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Keywords: Olive Oil, Flavor, Off-Flavor, Rancidity, Thermal Desorption

ABSTRACT

Flavor is an important quality criterion for virgin olive oils. The identification of the compounds causing the flavor or off-flavor therefore is the key for quality control. Their analysis in olive oils usually requires more or less cumbersome sample preparation like liquid/liquid extraction, solid phase extraction or distillation techniques, often with the drawback of organic solvent use. Headspace and purge & trap methods do not use organic solvents, but their analyte range is restricted to the volatiles and therefore characterizes more the compounds contributing to aroma/smell of a sample,not the flavor/taste. Direct thermal extraction of olive oil in an inert atmosphere under controlled temperature conditions can be used to easily analyze the volatile and semi-volatile compounds contributing to flavor. 10 μL of olive oil is injected into an empty glass tube and inserted into a thermal desorption unit (TDS). The TDS was ramped to 80°C with high desorption flow, allowing the analytes to be transferred into a PTV-liner and trapped at sub-ambient temperatures (-150°C), while retaining the oil-matrix in the TDS tube. After completion of sample transfer, the PTV was ramped to 280°C, releasing the extracted compounds into a GC/MS system for subsequent analysis at very high sensitivity.


Quantitative Determination of Trace Analytes in Solid Materials by Thermal Extraction GC

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Keywords: Thermal Extraction, Polyethylene, Hydrocarbons, PET, limonene, Calibration, IDEMA

ABSTRACT

Examples of optimized conditions for quantitation of residual hydrocarbons in polymeric packaging film and residual flavor components in recycled PET are shown. Techniques and equipment necessary for reliable calibration are also described.


Elimination of Non-Volatile Sample Matrix Components After GC Injection using a Thermal Desorber and Microvial Inserts

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Keywords: Microvial, QuEChERS, Pesticide Residue, Motor Oil, Thermal Desorption, GRO, GC/MS

ABSTRACT

In this study we describe direct liquid injection techniques compatible with “dirty” samples containing non-volatile components. Using a glass liner that can be removed and replaced after the injection can eliminate interference from accumulated sample matrix components. Liners are designed to accommodate larger than normal liquid injection volumes to provide improved detection limits. Furthermore, the entire process including the liner exchange can be automated. To illustrate the utility of the technique, challenging liquid sample types such as samples prepared by the QuEChERS method for pesticide analysis and contaminated motor oils were repeatedly introduced into the GC. Chromatographic performance using the new sample introduction technique is compared to conventional injections into a hot inlet.


Characterization of Organic Compounds in Atmospheric Nanoparticles by Thermal Extraction - Comprehensive Two-Dimensional Gas Chromatography (GC x GC) in Combination with Selective Detection, Mass Spectrometry and Accurate Mass Detection

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attachment Characterization of Organic Compounds in Atmospheric Nanoparticles by Thermal Extraction

Characterization of Organic Compounds in Atmospheric Nanoparticles by Thermal Extraction - Comprehensive Two-Dimensional Gas Chromatography (GC x GC) in Combination with Selective Detection, Mass Spectrometry and Accurate Mass Detection

Keywords: Atmospheric nanoparticles, Thermal Extraction, TE, Comprehensive two-dimensional gas chromatography (GC x GC), High resolution time-of-flight mass spectrometry, HRTOF-MS

ABSTRACT

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).


Analysis of Aroma Compounds in Edible Oils by Direct Thermal Desorption GC/MS using Slitted Microvials

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Keywords: Aroma Analysis, Off-flavor, Edible Oil, Direct Thermal Desorption, Thermal Extraction, Microvial, GC/MS

ABSTRACT

This application note describes the direct thermal desorption of desirable and undesirable aroma compounds from edible oils. The oil sample is placed in a microvial from where it is directly heated using a GERSTEL Thermal Desorption Unit (TDU). Volatile compounds are transferred to the GC/MS system while leaving non-volatile oil matrix behind, preventing contamination of the GC inlet and column. Different microvial designs were evaluated and those with a slit positioned 1 cm from the bottom of the microvial were found to provide the best analyte transfer.


Volatile Organic Compounds in Air

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Keywords: Thermal Desorption, Air Analysis, VOC, JHAP

ABSTRACT

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.


The Use of Different PTV Inlet Liner Types for Trapping Alkanes, Aromatics and Oxygenated Compounds During Thermal Desorption

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Keywords: Thermal Desorption, PTV, Inlet liner, Sample Introduction

ABSTRACT

PTV inlets are often used for cryo-focussing and trapping of analytes for large volume, headspace, and thermal desorption applications. Selecting and optimizing trapping conditions for thermal desorption applications can be challenging, since often a wide variety of analytes spanning a broad boiling point range are present in each sample. For efficient, high fl ow thermal desorption systems such as the GERSTEL TDS, a variety of inlet liner configurations with different trapping characteristics are available. This study was conducted to qualify the best type of liner for the determination of alkanes, aromatics and oxygenated compounds by thermal desorption GC. Inlet liners packed with materials of different trapping strengths ranging from glass wool to adsorbents (Carbotrap™ or Tenax TA™) to special purpose multi-bed liners were used to cryo-focus test mixtures of alkanes, aromatics and oxygenates thermally desorbed from air sampling adsorbent tubes. The parameters trapping temperature and desorption fl ow were optimized for the best trapping efficiency. Guidelines are given for choosing appropriate trapping conditions for these analyte classes.


Design, Performance, and Applicability of a Newly Developed Sample Introduction System for Use with Stir Bar Sorptive Extraction (SBSE)

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Keywords: Stir Bar Sorptive Extraction, SBSE, Twister, Thermal Desorption

ABSTRACT

The use of stir bar sorptive extraction (SBSE) as a technique to extract volatiles and semi-volatiles from polar, especially aqueous matrices, has gained more and more acceptance in several application areas. Thermal desorption, analogous to SPME, has been found to be the most suitable technique to transfer the extracted analytes into an analytical system and make them accessible for gas chromatographic analysis. PDMS coated stir bars („Twister“) have much more stationary phase and consequently bigger outer dimensions compared to SPME fibers. They do not fit into standard injection ports for thermal desorption as SPME fibers do, therefore usually a thermal desorption unit is used for this purpose. This type of unit is intentionally designed to desorb previously trapped analytes from porous polymer-packed sample tubes, or for thermal extraction of volatiles from solids. It works perfectly for Twister desorption, but may simply be somewhat oversized if this is the only purpose.This paper describes the design, performance and applicability of a new desorption unit especially designed for use with “GERSTEL Twister”. This unit is compatible with existing GC models and can be automated using a modified regular autosampler.


Air Sampling of Fragrance Compounds using the Automated GERSTEL Gas Sampling System (GSS)

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Keywords: Air sampling, thermal desorption, gas chromatography, mass spectrometry

ABSTRACT

Air fresheners contained in spray cans are commonly used in households to mask unpleasant odors. Many types of fragrances are commercially available. The fragrance can be a complex mix of many components. The effectiveness of the freshener to mask the off odors over time can be directly related to the concentration of the fragrance components in the air. Therefore, an important aspect in product development is to monitor the airborne concentration of the fragrance components.

This study describes the use of the Field Portable GERSTEL Gas Sampling System (GSS28) for the collection of fragrance compounds in air. The GSS28 is a 28 position sampling system designed to perform active i.e. pumped sampling of air onto sorbent tubes. The sampler can collect multiple samples on a pre-programmed schedule or on demand from the user interface.

Air fresheners were released into the air and dispersed across a room and air samples were collected using the GSS28. The sorbent tubes were subsequently analyzed by thermal desorption GC/MS. Several fragrance components contained in the dispersed products were monitored and quantified over time. The study also included validation of an air sampling method for the compounds.


Automated Online Desorption and Analysis of DNPH Derivatives of Airborne Aldehydes and Ketones

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Keywords: Sample Preparation, Lab Automation, Air Sampling, Environmental Analysis, Material Emissions

ABSTRACT

The analysis of airborne aldehydes and ketones first involves collection of the analytes by passing air through a cartridge containing 2,4-dinitrophenylhydrazine (DNPH). As the air passes through the cartridge, the analytes react with the DNPH to form hydrazones which are immobilized on the cartridge. The cartridges are then eluted with solvent and the DNPH derivatives determined using HPLC with UV detection.

The GERSTEL MultiPurpose Sampler (MPS) can be configured with a special tray to hold DNPH cartridges, enabling efficient automation of the entire process of desorbing the analytes and injecting the eluate into the LCUV system. Automating the desorption of these cartridges can significantly improve both accuracy and reproducibility. In addition, the risk of operator error is reduced. The MAESTRO software PrepAhead function enables desorption of a cartridge during the chromatographic separation of the previously injected sample. This means that the next sample is always prepared and ready to be injected as soon as the HPLC system has completed the previous analysis, ensuring maximum sample throughput.


Extractables and Leachables Analysis of IV Bag Systems using Direct Thermal Extraction of the Materials and Stir Bar Sorptive Extraction of Aqueous Solutions coupled with Thermal Desorption Gas-Chromatography with Unit Mass and High Resolution Mass Spectrometric Detection featured


Direct Thermal Analysis of Solids - A Fast Method for the Determination of Halogenated Phenols and Anisols in Cork

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Keywords: Direct Thermal Desorption, Volatiles in Solids, Off- Flavours, Trace Analysis, Capillary GC/MS, CIS, PTV

ABSTRACT

Off-flavors in solid samples often cause analytical problems due to the necessity of sample pretreatment steps such as time consuming extractions followed by re-concentration of the resulting extracts and the danger of producing artifacts related to these methods. In this paper the potential of a direct thermal desorption of the solid sample in combination with an intermediate cryo-focusing step in the inlet-liner of a cooled injection system (CIS/PTV) followed by temperature programmed sample transfer to the analytical column, is discussed and demonstrated. It will be shown that a reliable and fast method for the analysis of halogenated compounds in solid materials can be established without any sample pretreatment.


Design, Performance and Applicability of a Multi-Functional Thermal Desorption System for Trace Analysis in Capillary GC

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Keywords: Direct Thermal Desorption, Volatiles in Solids and Liquids, Trace Analysis, Capillary GC/MS, PTV, CIS

ABSTRACT

Thermal desorption is a well known technique for the analysis of volatile organic contaminants in air normally adsorbed on porous polymers and has been previously discussed [1]. This operation principle can also be adapted for the direct thermal desorption of volatiles in solid samples. In this paper the potential of a newly developed thermal desorption system for direct desorption and analysis of volatiles from liquid and solid 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 within a wide boiling range.

[1] R. Bremer, A. Hoffmann and J.A. Rijks, Proceed. of the 14th Interntional Symposium on Capillary Chromatography, Baltimore, MD USA (1992), P. Sandra and M.L. Lee (ed.), 206-213. [2] I. Blankenhorn, D


Trace Analysis of PAH's and PCB's in Soil through On-Line Direct Thermal Desorption

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Keywords: Direct Thermal Desorption, Volatiles in Soil, PCB´s and PAH´s, Trace Analysis, Capillary GC/MS, Cooled Injection System CIS, PTV

ABSTRACT

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