Application Note 010: Use of diffusive samplers with TD–GC analysis for monitoring VOCs in ambient air
This Application Note reviews indoor and outdoor air monitoring of volatile organic compounds (VOCs) using tube-type diffusive samplers and thermal desorption (TD)–GC analysis. Specific attention is paid to general sampling/analytical procedures, concentration/detection limits, applicable analyte ranges, minimising artefacts, quality assurance and method limitations.
Application Note 015: On-line process control of speciated organic chemicals in industrial gases at sub-ppb levels
This Application Note describes validation of an on-line thermal desorption–mass spectrometry (TD–MS) system for rapid measurement of sub-ppb levels of VOCs in industrial carbon dioxide. The combination of on-line TD with process MS allows the high-throughput, near-real-time measurement of trace-level VOCs, an approach that could be valuable for the the detection of hydrocarbon contaminants and volatile fermentation byproducts in streams of industrial gases.
Application Note 016: Round-the-clock, on-line and cryogen-free monitoring of hydrocarbons from acetylene to trimethylbenzene in ambient air
This Application Note describes a semi-continuous on-line thermal desorption system for monitoring of a complex mix of volatile and very volatile hydrocarbons (‘ozone precursors’) in air. The reliability and reproducibility of the system are examined, and based on signal-to-noise ratios, detection limits were found to be below 0.1 ppb. Finally, the system was tested by using it to sample forested semi-rural air subject to high levels of weekday traffic.
Application Note 028: Optimising analytical performance and extending the application range of thermal desorption for monitoring air indoors and inside vehicle cabins
This Application Note describes considerations relating to analyte retention efficiency, desorption efficiency, artefacts, band broadening and analyte/system stability during the development and validation of thermal desorption procedures. Examples of optimum method performance in terms of precision, linearity and sensitivity are presented.
Application Note 029: VOC air monitoring technology and its application to contaminated land
This Application Note summarises how the development of soil probe technology allows sorbent-tube-based sampling technology to be used to monitor volatile organic compounds in contaminated land. Examples include landfill sites and soil in the region of a chemical plant.
Application Note 033: Analysis of the interior atmosphere of a passenger car by TD–GC–MS
This Application Note describes the TD–GC–MS analysis of potentially harmful volatile organic compounds in the air of two new cars. The method allows a wide range of compounds can be screened, and permits comparison between different models, allowing information to be obtained about the source of individual components.
Application Note 037: Workplace air monitoring using pumped sampling onto sorbent tubes and analysis by TD–GC–MS
This Application Note demonstrates the sensitivity of thermal desorption (TD) and GC–MS analysis for the detection of volatile organic compounds (VOCs) in factory and fenceline air, using pumped sampling onto sorbent tubes.
Application Note 043: Quantitative monitoring of monoethylene glycol (MEG) by TD–GC
This Application Note demonstrates that thermal desorption (TD–GC) can be used to analyse a monoethylene glycol standard with excellent linearity, making it a suitable method for detecting vapour of this additive in natural gas.
Application Note 047: Rapid and reliable screening of landfill gas for priority and odorous compounds by TD–GC–MS
This Application Note describes the use of sorbent tubes to sample landfill gas, with analysis by thermal desorption (TD) and GC–MS detection. In particular, we describe the use of optimised sampling and analytical conditions for the detection of toxic and priority VOCs, and for effective water management. Combined with automated detection of target compounds using library-matching TargetView software, this approach offers the ability to greatly speed up the screening of complex landfill gas profiles.
Application Note 049: Diffusive (passive) monitoring and TD–GC analysis of hazardous air pollutants in industrial and urban locations
This Application Note describes the monitoring of benzene and other vapour-phase organic compounds in urban or industrial air using diffusive (passive) sampling onto sorbent tubes with subsequent analysis by thermal desorption (TD) with gas chromatography (GC). It summarises how this robust and cost-effective air monitoring technique should be applied to monitoring airborne VOCs around the perimeter of oil refineries and other industrial facilities. Topics covered include advice on sorbent selection, determination of uptake rates, deployment of samplers, method sensitivity and application/interpretation
Application Note 077: Using thermal desorption for industrial (stack) emissions testing
This Application Note covers selection of the appropriate organic vapour sampler for the analytes of interest in stack gas sampling, and optimisation of the subsequent sampling and thermal desorption (TD)–GC analytical process. Also discussed are the benefits of thermal desorption against solvent extraction.
Application Note 079: Air monitoring – The advantages and applications of canisters and tubes
This Application Note discusses the application areas of canister-based and sorbent-tube-based sampling for volatile organic compounds (VOCs), and the advantages and limitations of each approach.
Application Note 080: Evaluation of a ‘soil gas’ sorbent tube for improving the measurement of volatile and semi-volatile fuel vapours in contaminated land
This Application Note describes the development of a two-bed sorbent tube in conjunction with Markes’ Micro-Chamber/Thermal Extractor for the sampling of petroleum vapours collected from soil gas. Both lighter and heavier (polyaromatic, longer-chain) hydrocarbons were detected, and quantitative recovery is demonstrated for even the heaviest fuel components.
Application Note 081: Innovative cryogen-free ambient air monitoring in compliance with US EPA Method TO-15
This Application Note describes the GC–MS analysis of humidified canister ‘air toxics’ samples at various relative humidities, using cryogen-free systems for thermal desorption preconcentration. Detection of 65 target compounds ranging in volatility from propene to naphthalene is demonstrated with excellent peak shape and performance well within the criteria set out in US EPA Method TO-15, including method detection limits as low as 4 pptv.
Application Note 086: Monitoring ‘air toxics’ in ambient air using sorbent tubes by automated, cryogen-free thermal desorption in accordance with US EPA Method TO-17
This Application Note demonstrates the fundamental sensitivity of Markes’ ULTRA-UNITY system for the analysis of TO-17 ‘air toxics’ ranging in volatility from methyl chloride to hexachlorobutadiene. Also highlighted is the ability of Markes’ ClearView background-compensation software to improve signal-to-noise ratios and enhance spectral purity for trace-level compounds.
Application Note 087: Monitoring trace greenhouse gases in air using cryogen-free TD–GC–MS
This Application Note shows how Markes’ thermal desorption (TD) technology for analysing ‘air toxics’ can also be applied to the detection of the most challenging ultra-volatile greenhouse gases, including tetrafluoromethane, hexafluoroethane, sulfur hexafluoride and nitrous oxide. Detection limits below 1 ppt are demonstrated for sulfur hexafluoride and hexafluoroethane, with excellent peak shape and linearity also being obtained.
Application Note 097: Analysis of polycyclic aromatic hydrocarbons from vehicle exhaust using TD–GC–MS
This Application Note describes how thermal desorption (TD), in conjunction with GC–MS, can be used to detect polycyclic aromatic hydrocarbons in vehicle exhaust.
Application Note 106: Continuous on-line monitoring of hazardous air pollutants by TD–GC–FID
This Application Note shows how the TT24-7™ Series 2 thermal desorber can be used for the continuous on-line detection of hazardous air pollutants, and how the time profiles and concentration data obtained can be of value for source apportionment.
Application Note 114: Passive monitoring of benzene and other hazardous air pollutants at refinery perimeters in accordance with US EPA Method 325
This Application Note describes a stepwise approach to complying with US EPA Method 325 for monitoring volatile organic compounds (VOCs) at refinery perimeters. A range of equipment from Markes International is outlined that allows fully method-compliant deployment of tube-based passive samplers, sample analysis and tube cleaning. All these stages are underpinned by a radio-frequency identification tagging system to ensure a robust chain of custody from field to lab.
Application Note 115: Simple and reliable quantitation of ppt-level PAHs in air by TD–GC–MS
This Application Note describes the performance of a sorbent tube and optimised analytical protocol dedicated to the detection of ppt-level polycyclic aromatic hydrocarbons (PAHs) in ambient air. Using active (pumped) sampling with analysis by thermal desorption–gas chromatography (TD–GC), this innovative approach completely avoids the labour-intensive solvent-extraction protocol employed in many standardised methods. The optimised analytical method also offers increased sensitivity due to increased extraction efficiency, absence of a dilution stage, and efficient transfer of compounds to the GC.
Application Note 119: Highly efficient monitoring of VOCs in stack emissions using sorbent tubes analysed by TD–GC–MS in accordance with European standard method CEN/TS 13649
This Application Note demonstrates that Markes International’s automated thermal desorption systems offer excellent results for monitoring volatile organic compounds (VOCs) in stationary source emissions in accordance with the updated version of the European standard method CEN/TS 13649 released in 2014. The value of repeat analysis for method development and result verification is also demonstrated.
Application Note 128: Extending the analysis of ozone precursors – Continuous, unattended, cryogen-free on-line monitoring of PAMS hydrocarbons and polar VOCs in ambient air by TD–GC–MS
This Application Note describes validation of a cryogen-free thermal desorption (TD)–GC–MS system for on-line monitoring of an extended range of very volatile species in ambient air, which includes ‘ozone precursors’ (as specified by the US PAMS program), polar compounds and monoterpenes. In addition to analysis of a 61-component standard mix and a real air sample, we demonstrate low method detection limits using the new trap-based Kori-xr system for eliminating water from the air stream.
Application Note 129: Extending the analysis of ozone precursors – Continuous, unattended, cryogen-free on-line monitoring of PAMS hydrocarbons and polar VOCs in ambient air by dual-column TD–GC–FID
This Application Note describes validation of a cryogen-free thermal desorption (TD) system with dual-column GC–FID detection for on-line monitoring of an extended range of very volatile species in ambient air, which includes ‘ozone precursors’ (as specified by the US PAMS program), polar compounds and monoterpenes. Using the new Kori-xr system for analyte focusing and water removal, we demonstrate excellent chromatographic performance, linearities and reproducibilities for a 59-component standard mix, and apply this method to a real air sample.
Application Note 133: Going beyond the requirements of US EPA Method TO-15: Innovative cryogen-free ambient air monitoring of trace-level air toxics at high humidity
This Application Note describes the GC–MS analysis of trace-level ‘air toxics’ in humidified canister air, using Markes’ ground-breaking cryogen-free Dry-Focus3 pre-concentration technology. We show that this system is able to detect 65 target compounds ranging from propene to naphthalene, with method detection limits as low as 0.7 pptv in SIM mode, making it compliant both with standard TO-15 methods, and with ‘trace TO-15’ methods stipulating lower detection limits.
Application Note 136: The performance of thermal desorption for the quantitative analysis of long-chain hydrocarbons
This study investigates the ability of Markes’ thermal desorption (TD) systems to monitor semi-volatile organic compounds (SVOCs), using a wide range of n-alkanes (n-C16 to n-C44) as a model. We demonstrate how modern TD
technology delivers robust and repeatable results for compounds across this wide boiling range and can therefore be used to enhance GC–MS analysis of trace SVOCs in air and other matrices. We also show how highly repeatable re-collection of TD samples is a convenient approach to validating analyte recovery in accordance with standard methods.
Application Note 137: Quantitative determination of semi-volatile polychlorinated biphenyls (PCBs) using TD–GC–MS
This study describes the performance features that enable Markes’ thermal desorption (TD) systems to be used for the GC–MS analysis of trace-level polychlorinated biphenyls (PCBs) in air. We discuss the advantages of TD compared to conventional air monitoring methods for semi-volatiles, and show how Markes’ innovative sample re-collection functionality facilitates method development by validating quantitative recovery of these challenging analytes all the way through the TD system. Other key results include high sensitivity (with limits of detection ranging from 0.022–0.054 ng, in line with independent studies), excellent linearities (mean R2 0.997), and high analytical precision (all RSDs below 2.5%).
Application Note 138: A robust TD–GC–MS method for the determination of trace-level phthalate esters in air – Method validation and field study
This study describes the performance of Markes’ thermal desorption (TD) systems for the GC–MS analysis of trace-level phthalates in air. We discuss the advantages of thermal desorption compared to conventional air monitoring methods for semi-volatiles, and show how Markes’ innovative sample re-collection functionality facilitates TD method development by validating quantitative recovery of these challenging analytes all the way through the TD system. We also show excellent analytical precision, with RSDs <5% for all compounds, and discuss an independent field investigation of phthalate levels in urban air in Belgium, which reported very high linearities (R2 =0.998), and limits of detection <0.23 ng/m3.
Application Note 139: High-performance analysis of polycyclic aromatic hydrocarbons (PAHs) by TD–GC–MS: Method validation and case-study
This study investigates the performance of Markes’ thermal desorption (TD) systems for the analysis of polycyclic aromatic hydrocarbons (PAHs) in air. We describe how sample re-collection can be used to conveniently check and validate recovery of high-boiling analytes through Markes’ TD system, therefore enhancing confidence in this fully automated and high-sensitivity alternative to conventional solvent-extraction methods. Other key results were area RSDs <4.3% (well within the 30% limit specified in US EPA Method TO-13A), and carryover values below 1.5%. We also summarise results from an independent investigation of urban air in Belgium, which showed excellent linearities (R2 >0.998), and limits of detection <0.54 ng/m3.
Application Note 140: Quantitative analysis of airborne semi-volatile flame retardants using sorbent tube sampling with TD–GC–MS
This study introduces the results of research into the performance of sorbent-tube sampling and Markes’ thermal desorption (TD) systems for the analysis of two classes of flame retardants of current concern – polybrominated diphenyl ethers (PBDEs) and organophosphates (OPs). Key indicators of method performance for these challenging semi-volatile compounds are reproducibilities <10.3%, carryovers <3.2%, linearities >0.998 and LODs <0.171 ng/m3, with a field study demonstrating the detection of OPs in indoor air at low ng/m3 levels.
Application Note 145: Extending whole-air monitoring: Simultaneous cryogen-free analysis of PAMS ozone precursors and TO-15 air toxics from canisters in accordance with new Chinese air-monitoring regulations
This application note describes cryogen-free sampling and analysis of the 108 analytes of a combined list of PAMS ozone precursors and TO-15 air toxics in high-humidity environments, in compliance with the detection limit and data-quality requirements of Chinese EPA Method HJ 759 and the Chinese Environmental Air Volatile Organic Compound Monitoring Program. The use of Markes’ ground-breaking Dry-Focus3 pre-concentration and water management technology results in excellent chromatographic peak shape at 100% humidity, whilst maintaining sample-to-sample cycle times below 60 minutes. The use of robust, field-proven dual-column/Deans switch technology in the GC oven allows FID analysis of highly volatile C2 hydrocarbons, with the remaining analytes detected using a single-quadrupole mass spectrometer operating in full-scan mode.