Abstract

Workshop on thermal desorption & other miniaturized techniques - September, 23, 2019

 

DHS as flexible sample preparation tool for chemical analysis

Christophe Devos
Research Institute for Chromatography, Belgium

 

Dynamic Headspace Enrichment (DHS) has become a widely introduced sample enrichment technique. This headspace technique gives us high sensitivity together with excellent profiling capabilities over a broad volatility range. Aroma profiling by DHS is often performed within the food and cosmetic industry but also quantitative target compound analysis of impurities, off-flavor compounds and specific environmental parameters are covered by this technique. Since its introduction, the flexible Gerstel DHS system, fully automated by the MPS autosampler, made it possible to establish different DHS sampling modes which opened several new and automated sampling approaches and made us tackle a wide variety of complex sample matrices.

 
 

Exploring the advantages of automated sample preparation and high sensitivity GC-MS for SVOC and pesticide analysis in environmental waters

John Quick
ALS Global, United Kingdom

 

Recent advances in the sensitivity and selectivity of modern GC-MS instrumentation combined with the development of laboratory robotic systems have made it possible to miniaturise and automate traditional sample preparation methods without compromising compound limits of detection. This has the potential to deliver major efficiency and productivity gains for busy commercial laboratories. In particular the application of fully automated Dispersive Liquid/Liquid Microextraction (DLLME) shows great promise for the extraction of a very wide range of organic pollutants from aqueous matrices, combined with modern GC-MS instrumentation detection limits (LODs) in the low parts-per-trillion (ppt) range are possible from less than 10mls of sample.

 

Hydrocarbon Index : a fully miniaturized and automated technical

Michel Letort
Veolia Research & Innovation, France

 

By definition, Hydrocarbon Index by GC-FID, corresponds to all the compounds extractable by a solvent or a mixture of solvents whose boiling point is between 36 ° C and 69 ° C, not adsorbed by Florisil® and retention times are between n-decane (C10H22) and n-tetracontane (C40H82).

The substances defined above are mainly non-polar compounds, linear or branched aliphatics, alicyclics, aromatics and alkyl substituted aromatics. It applies from 0.05 mg / L for drinking water but also for treated wastewater from 0.2 mg / L.

This method echoes the ISO9377 standard. It remains long and tedious when it comes to routine analysis. It involves the use of a large quantity of solvent, an important test sample but above all a handling requiring many extraction steps.

We will present here an original philosophy of miniaturization and automation allowing to realize automatically the dozen steps of the manual methodology. The gain will be economic as well as productivity. The reduction by a factor of 200 of the quantities of solvent (hexan) makes it a "green method" and respect for the environment will be greatly increased.

 

Thermal desorption and GC×GC-HRTOFMS for the identification of odorous compounds in complex polymer matrices

Catherine Brasseur
Certech, Belgium

 

Quality of life is becoming a growing concern and consumer expectations have evolved. Higher demands are made in regard to the evaluation of volatile organic compounds (VOCs) emitted by materials and end products, as well as the impact of odorous compounds on the quality of indoor air, human health and environment. Gas chromatography coupled to mass spectrometry and olfactometry (GC-MS/O) is a methodology widely applied in the material industry allowing to establish correlation between the chemical nature and concentration of specific odorous compounds with the human perception of smell. However, some materials may produce very complex VOC profiles and make it difficult to identify odor active compounds. Comprehensive two-dimensional gas chromatography coupled to high resolution mass spectrometry (GC×GC-HRTOFMS) was identified as a powerful tool to characterize complex VOC profiles. The instrument is equipped with thermal desorption, a versatile technique for VOC analysis.

Practical examples will be presented to demonstrate the useful complementarity of this advanced technique for characterization of odour emissions, with the identification of unknown compounds, detection of odorous compounds at trace levels as well as the monitoring of VOCs profiles and possible modifications related to specific additivation for odour reduction.

 

Aroma Analysis of cocoa and chocolate

Isabelle Van Leuven
Barry Callebaut, Belgium

 

An introduction of the formation of the flavor from cocoa bean to chocolate will be given, followed by a brief description of the aroma chemistry of cocoa and chocolate. An overview of aroma analysis at Barry Callebaut will be presented. This will explain the use of GC-MS to provide molecular insight in the aroma of raw materials (such as cocoa beans, cocoa ingredients, dairy ingredients, vegetable fats, flavors), final products (such as chocolates) and in the aroma formation mechanism (fermentation, roasting, shelf life). Finally, some case studies of aroma analysis at Barry Callebaut will be discussed

 

Exploring different available extraction techniques to get aroma profiles of different kinds of cheese

Araceli Lagadec Marquez
Fromageries BEL, France

 

The Bel Group manufactures different types of cheeses with a wide variety of organoleptic and physicochemical characteristics. What's more different than a Leerdammer millstone, a portion of Kiri or a Boursin sandwich? In order to obtain an exhaustive analysis of the aroma compounds released by these cheeses, different headspace extraction techniques (HS-SPME, DHS, MVM, MVM-FE) will be detailed and compared through the results obtained. during a comparative study. Finally, some complementary lines of work to be done to study the relevance of extraction techniques will be proposed.

     

GC×GC-TOFMS for in vitro and ex vivo characterization of lung inflammation mechanisms

Jean-François Focant
Liège University, Belgium

 

Most of lung diseases involve a certain level of inflammation. The characterization of the ongoing inflammation processes is crucial to define proper medication. The inflammation processes are associated with oxidative stress, which yields to the conversion of chemical from the membranes (as polyunsaturated fatty acids) into volatile compounds secreted by the lungs.

This report will focus on the investigation of both bronchoalveolar lavage fluid (BALF) samples and A549 epithelial cells, originally isolated from human alveoli and further stressed by oxidative agents, for a study on lung inflammation mechanisms. In both studies, volatile organic compounds (VOCs) were sampled by means of thermal desorption (TD) solid-phase microextraction (SPME, and dynamic headspace (DHS) and analyzed by GC×GC- TOFMS.

Analytical workflows were optimized using central composite design models. On the processing side, different models were designed to compare the volatile profile in different inflammatory conditions. Univariate and multivariate feature selection approaches were used to identify specific inflammatory markers.

     

New features and benefits of automated sample preparation based on Robotic Technology

Tatiana Cucu
Research Institute for Chromatography, Belgium

 

Conventional analytical methods are time consuming, involve high consumption of reagents and samples, high costs per analysis, increased waste generation but also very important a considerable increase in human error. Nowadays, sample preparation is still considered as a major bottleneck in the analytical workflow. Therefore, miniaturization and automation of analytical methods becomes a necessity in research, industrial and routine control laboratories especially when many identical tests have to be carried out as reliable as possible. Considering the availability of very sensitive MS systems such as triple quadrupole, time-of-flight or Orbitrap analyzers, miniaturized sample preparation seems moreover feasible.

In this presentation, examples of automated methods based on the new generation Gerstel Robotic Technology will be discussed and illustrated with applications in life science, food, flavour and fragrance and environmental science. These include trace analysis of priority pollutants in water, quality control of fat and oil samples by fatty acid methyl ester and intact lipid (triglyceride) analysis and determination of important markers in biological samples (serum, urine etc). For these examples, it will be demonstrated that robust fully automated sample preparation methods can be developed if a critical balance is respected between sample amount, method sensitivity, and sample throughput. In several cases, miniaturization and automation can even result in important analytical improvements not possible to achieve using conventional methods.

     


Workshop SBSE - September, 24, 2019

 

Two decades of Stir Bar Sorptive Extraction: a retrospective and outlook

Frank David and Pat Sandra
Research Institute for Chromatography, Belgium

 

In this presentation a brief overview will be given of the 20-year history of stir bar sorptive extraction (SBSE). Main appreciated features of SBSE are the solventless extraction, predictable extraction efficiencies, very high sensitivities when combined with thermal desorption (TD) - GC-MS, and excellent repeatability and reproducibility for determinations of solutes with a log P larger than 3 [1]. For more polar solutes, matrix and solute modifications have been applied to enhance recovery. Over the years, also other coating materials have been evaluated and/or developed for extraction of more polar compounds. Only a limited number, however, are operating in the sorptive or partitioning mode while only few of them have favorable thermal characteristics to be used in TD-GC-MS applications. Alternatively, other methods applying PDMS stir bars were recently developed to extend SBSE to more polar solutes: solvent assisted SBSE (SA-SBSE) and ice concentration linked with extractive stirrer (ICECLES). The potential of these techniques will be discussed and the future perspectives of SBSE will be outlined. 

 
 

Fragrance analysis by using selectable 1D2D-SBSE-GCMS technique

Ng Khim Hui
Firmenich, Singapore

 

A selectable one-dimensional (1D) or two-dimensional (2D) gas chromatography-mass spectrometry (GC-MS) system coupled with flame ionization detector (FID) and olfactory detection port (ODP) is employed in fragrance analysis of consumer products and fine fragrances. A split/splitless (SSL) injector and a programmable temperature vaporization (PTV) injector are connected via a 2-way splitter of capillary flow technology (CFT) in this selectable 1D/2D GC-MS/FID/ODP system to facilitate liquid sample injections and thermal desorption (TD) for stir bar sorptive extraction (SBSE) technique, respectively. The dual-linked injectors set-up enable the use of two different injector ports (one at a time) in single sequence run without having to relocate the 1D capillary column from one inlet to another. Target analytes were separated in 1D GC-MS/FID/ODP and followed by further separation of co-elution mixture from 1D in 2D GC-MS/FID/ODP in single injection without any instrumental reconfiguration. Coupling with SBSE, the technique has dramatically enhanced the separation of perfume mixture, as well as improved the detection of high odor impact perfume ingredients which commonly used at trace level.

 

Plant-climate interaction effects on the tea metabolome

Albert Robbat
Tufts University, USA

 

Well-known are the effects of heatwaves, droughts, and cold weather on crop yield.  In contrast, little is known about how plant-climate interactions affect crop quality, which is defined by the sensory and health beneficial properties of plant materials. To learn how changes in climate affect quality, we need detailed information on how the total metabolome changes due to these stressors. Toward this end, we used Twisters to sample tea leaves in the field and infusions in the lab. The initial database was produced using automated sequential, 2-dimensional, gas chromatography/mass spectrometry (GC-GC/MS). Annotation of the database was the result of subsequent analyses of GC/MS data using the Ion Analytics spectral deconvolution and library-building data analysis software.

We detected more than 750 metabolites in teas harvested from Yunnan and Fujian, China, and from South Carolina, US, before (spring), during, and after (summer) heavy rains (monsoons, hurricanes) and the seasonal and elevational changes in temperature. We found striking differences in composition and concentration for example, of the 350 compounds detected in a sample, about two-thirds increased or decreased in concentration by more than 100%. Approximately 25% of them changed concentration by more than 1000%. When comparing pre- vs. post-monsoon teas or low vs. high elevation teas, at least 50 unique compounds were detected in each sample. These dramatic changes in both composition and concentration affected more than 200 metabolites that possess organoleptic and/or nutritional properties. Findings will be presented describing the targeted/untargeted methodology and how our results led to new products in which seasonal changes in the plant makes tea undrinkable.

 

Recent developments using ICECLES for ultra-trace and comprehensive analysis

Brian Logue
South Dakota University, USA

 

The ability to determine compounds at “ultratrace” concentrations (e.g., drinking water contaminants) and the ability to comprehensively evaluate the makeup of materials (e.g., food/flavor analysis) are critically important, but currently challenging. ICE Concentration Linked with Extractive Stir bar (ICECLES) was introduced in 2016 as a significant step towards addressing these difficult analyses. To date, ICECLES has been applied to ultratrace analysis of nitrosoamines in drinking water, comprehensive flavor analysis of green tea, trace analysis of pesticides, ultratrace analysis of disease markers in biological matrices, and comprehensive analysis for product quality testing. We have also combined ICECLES with headspace SBSE for comprehensive food flavor/aroma analysis. ICECLES has produced pg/L limits of detection and up to 1000-fold signal increases compared to SBSE. The performance of ICECLES in each of these applications will be reviewed.

 

Implementing Green into analytical daily work

Bastien Raccary
The Green Analytical Project

 

Introduced in the early 90’s, Green Analytical Chemistry (GAC) has been declined from the 12 principles of Green Chemistry. Considerable work has been carried out to miniaturize, automate, limit solvent and electrical/gas consumption around sample preparation techniques and analytical instruments in laboratories. Nowadays, SBSE (Stir Bar Sorptive Extraction) tools is among the most described extraction technique and offer numerous advantages: robustness, easy to handle, low solvent use and favorized in situ extractions. Alternatively, many papers have described tools to help analytical scientists to evaluate their ecological impact (NEMI, Analytical Eco Scale, HPLC-EAT or more recently GAPI. If tools exist and are well described, there is a large gap between everyday practices in laboratories and environment-friendly practices. Environmental impact is rarely included in the analytical development process and choice of the sample preparation/analytical method is preferably oriented on low-cost/easy to implement existing solutions. Furthermore, if tools to calculate environmental impact are well described, they are not easy to handle, even for an experienced user and do not lead to a complete and objective life cycle analysis. Criteria remain insufficiently exploited and metrics may sometimes seem questionable, even arbitrary. This presentation will be focused on practical examples to illustrate divergent points in analytical development process when considered from an environmental point.

 

Validation of a method for the analysis of 110 organic pollutants in surface water by stir bar sorptive extraction

Oltan Canli
Tübitak, Turkey

 

A multi-residue method for the analysis of semi-volatile organic pollutants in surface water at ppt-ppq levels in compliance with the Turkish Regulation on the Management of Surface Water Quality (most of them is the same with the EU Water Framework Directive (WFD)) has been developed and validated by Stir Bar Sorptive Extraction (SBSE) and thermal desorption coupled with gas chromatography-triple quadrupole mass spectrometry. The method includes various families of compounds included in the WFD, such as polychlorinated biphenyls, polycyclic aromatics hydrocarbons, polybrominated diphenyl ethers, phenols, phthalates and pesticides etc. The method is also applicable to the analysis of similar contaminants that are not in this list. Extraction conditions were optimised in order to analyse simultaneously analytes with different polarities and octanol-water partition coefficients. The quantification limits (LOQs) obtained ranged from 0.12 to 50 ng L-1 and complies with the requirement for analytical methods to be used in the analysis of the compounds included in the directive. Several quality parameters as linearity, trueness and precision were studied with good results, and also uncertainty was estimated.  Precision (in terms of RSD) was lower than 40%, recoveries ranged between 60 and 120%, and determination coefficients were higher than 0.990 for all analytes. Different parameters affecting the SBSE procedure were optimized.

 

SBSE applied to microbreweries and traditional african beers

Mathew Muzi Nindi
University of South Africa, South Africa

 

Beer is one of highly sort out beverages in the world which consists of essential ingredients such as barley, water, hop and yeast.  Hops are responsible for the bitterness characteristic of beer and contributes to the overall favour.  Hop aroma and flavour in beer originates from volatile organic compounds (VOC) present in the essential oil.  The hop derived compounds in beer are very complex involving several chemical groups such as alcohols, esters, aldehydes, ketones, acid, terpenoids, phenols and sulphur compounds.  The VOCs in beer contribute significantly to its flavour, quality and consumer preference. Gas chromatography-mass spectrometry is the most suitable technique to assessing VOCs. Headspace-solid phase microextraction (HS-SPME) is the most commonly used extraction technique.

In this study the use of stir-bar sorptive extraction (SBSE) and solid-phase microextraction (SPME) was used as extraction methods for the hop derived compounds in the traditional African beers. The extracted compounds were followed by quantification by gas chromatography mass spectrometry (GC-MS) and/or GCxGC-HRT-MS.  Several parameters of the two extraction methods were compared.

 

A validated SBSE-GC-MS/MS method for ultra-trace analysis of priority pollutants in surface water in the context of the EU water framework directive with additional focus on suspended matter

Oliver Lerch & and Jasmin Zboron
Gerstel GmBH, Germany

 

AIn recent years many challenges arose in the field of water analysis. In addition to screening and identification of unknown or emerging contaminants, ultra-sensitive target analysis is needed in order to meet the requirements specified in legislation e.g. the European Water Framework Directive (2013/39/EU, EU-WFD).

In our lecture we will present water analysis based on EU-WFD guidelines employing stir bar sorptive extraction (SBSE). Analyte enrichment is performed by stirring the sample with a polydimethylsiloxane (PDMS) coated glass stir bar. The extracted analytes are completely transferred onto a GC-MS/MS by thermal desorption making this technique highly sensitive.

The developed target analysis method fulfills requirements of the EU-WFD. Around 100 GC- and Twister-compatible compounds that are relevant in the field of surface water analysis are included, e.g. organochlorine pesticides, triazines, PAHs, PCBs and PBDEs. The method was comprehensively validated and the quantitation of particle adsorbed analytes was given particular focus. Even though the method is based on only 100 mL sample volume, most of the compounds showed limits of quantification (LOQ) in the double or triple digit pg/L range.

     

Evaluation of different sorptive sampling techniques to study VOCs emitted by the human body

Beate Gruber
Research Institute for Chromatography, Belgium

 

Volatile profiling of compounds involved in biochemical processes and emitted by the human body, has been increasingly exploited in various areas such as forensics, clinical diagnostic and human biomonitoring. Particularly, analysis of skin emanations and exhaled breath represents a promising non-invasive approach to investigate endogenous as well as exogenous substances. Since VOCs are present at trace levels in bodily fluids, pre-concentration prior to analysis is required. Therefore, various sorptive extraction approaches have been evaluated for the sampling of human emitted VOCs and the subsequent analysis by thermal desorption coupled with gas chromatography – mass spectrometry. Taking into account the impacts of different sampling conditions, the sorptive extraction devices were tested in a targeted study using reference substances, and by non-invasive sampling of VOCs emanating from the human body.

     

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