56 Environmental Laboratory - Focus on Pesticide Analysis
Dual-Column GC Analysis of Organochlorine Pesticides on SLB-5ms and SLB-35ms
57 Varieties — Pesticides in Bees That Is
Honey bees are an important component in sustaining life — helping to provide food for our plates and to pollinate plants. But in recent years there has been a decline in the in the bee population.
The phenomenon of deaths amongst many colonies of bees is known as Colony Collapse Disorder (CCD). With the importance of bees to our food supply and the global economy — researchers have been looking for clues to the cause of CCD. One team has applied the QuEChERS principle and developed a method to analyse bees for over 200 pesticides at once.
CCD is a complex phenomenon. Many groups have a view on the cause of the bee population’s decline. But in reality — we don’t know. One thing that many people agree on is that it is not down to one thing — with the two main culprits generally identifi ed as pesticides or disease causing parasites.
Figure 1. Organochlorine Pesticides on SLB-5ms.
The analysis of low levels of organochlorine pesticides by gas chromatography-electron capture detector (GC-ECD) is routinely performed by analysts in environmental laboratories. Methods require the analysis of each sample extract on two columns with differing selectivity to confi rm identifi cations.
An ECD is highly sensitive, capable of detecting analytes at picogram levels. Its highly sensitive nature, in combination with the low detection limit requirements of promulgated methods (for example, US EPA Method 608, 8081, and OLM04.2 PEST), make it necessary to use GC columns with low bleed. Additionally, the susceptibility of several analytes to degradation and adsorption make inertness another extremely important characteristic when choosing columns.
This application requires two columns for the analysis of samples. The fi rst, often referred to as the ‘primary’ column, is used to determine, by retention time comparison with a standard, if any target analytes could be present in the sample. If peaks are found within an analyte’s retention time window on the primary column, the presence of the analyte must be ‘confi rmed’ on a secondary or ‘confi rmation’ column with a different selectivity in order to be considered positive.
The SLBms column family, from Sigma Aldrich (USA), is designed for GC and GC-MS analysts who require low bleed, inert, durable, and consistent capillary GC columns. The SLB-5ms is virtually equivalent in polarity to a poly(5% diphenyl/95% dimethyl siloxane) polymer stationary phase. The SLB-5ms is virtually equivalent in polarity to a poly(35% diphenyl/65% dimethyl siloxane) polymer stationary phase. Together, these columns offer the orthogonal selectivity and stringent performance characteristics that are necessary to successfully perform the analysis of organochlorine pesticides using the dual-column approach previously described.
A low-level mixture of twenty organochlorine pesticides and two surrogate compounds, each analyte at 50 ppb, was prepared in hexane. This mixture was fi rst injected on the SLB-5ms column using conditions optimised to achieve maximise resolution. The mixture was then injected on the more polar SLB-35ms column using the same run conditions. The resulting chromatograms are shown in Figure 1 (SLB-5ms) and Figure 2 (SLB-35ms).
On both columns, peaks were easily integrated and baselines were exceptionally stable, with minimal rise observed, even when running to a fi nal oven temperature of 340ºC. The ability of both columns to be used at a high fi nal oven temperature allowed for elution of the last peak, decachlorobiphenyl, in less than 20 minutes. These run conditions were chosen to reduce analysis time, but a slower oven ramp rate can be used to increased resolution if desired.
Discussion
SLBms columns were developed for use in applications using a mass selective detector (MSD). Their extremely low bleed characteristics also make them useful for applications requiring the use of other highly sensitive detectors, such as an ECD.
The proprietary surface deactivation of SLBms columns provides the inertness necessary for the analysis of compounds susceptible to degradation and adsorption, such as organochlorine pesticides. For example, endrin and 4,4’-DDT are susceptible to degradation, and must be monitored. Both of these analytes exhibited good response on both columns.
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Varroa mites are parasites that can attack honey bees leading to the death of the colony. The mites attach to a bee’s body and suck their blood — this can lead to the bees being susceptible to viruses and diseases that can quickly spread through the colony weakening it and eventually leading to its death. Many scientists believe the parasite contributes to the cause of CCD — but for others, pesticides, used for plant protection and mite eradication, are believed to be the root cause of CCD.
Several studies have shown a link between pesticides and deaths in bees. As a result, the European Union has taken the decision to ban neonicotinoid pesticides — a relatively new pesticide that has also been linked to declines in the UK butterfl y population.
But there are around 200 different pesticides in use around Europe, with many different chemical properties and functional groups. As they are used, any interactions between the pesticides generates new combinations that could affect bees — and other insects.
To try and discover more about the links between pesticides and CCD, a team from the National Veterinary Research Institute in Poland have developed a method for determining 200 pesticides and their metabolites in bee samples. The research, published in the Journal of Chromatography A [
https://ilmt.co/PL/npkv], aimed to develop and validate an analytical method useful for determining pesticides and their residues in samples from bee poisonings — and in the samples they looked at the team found 57 different pesticides.
Determining pesticides and pesticide residues in bees involves what the team describe as a diffi cult sample matrix. To help make the sample preparation as straightforward as possible the team used the QuEChERS method. QuEChERS was originally developed for the determination of pesticides in foodstuffs, but can be used for other samples as discussed in the article, The Applications of QuEChERS Beyond Fruits and Vegetables.
The work will help us to protect our bees — essential if you like honey with your porridge.
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Start-to-Finish Workfl ows Designed to Increase Productivity for Pesticide Residue Testing
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The Thermo Scientifi c (USA) Pesticide Explorer Collection is a set of LC-MS solutions specifi cally tailored to fi t the needs of laboratories performing routine quantitation, targeted screening and non-targeted analysis of pesticide residues in food matrices.
The Thermo Scientifi c Pesticide Explorer Collection is a set of LC-MS solutions specifi cally tailored to fi t the needs of laboratories performing routine quantitation, targeted screening and non-targeted analysis of pesticide residues in food matrices. Each solution contains all of the components needed to simplify the routine monitoring of pesticides, including a pre-confi gured and -tested set of consumables, hardware, software and built-in instrument and data processing methods.
Four pre-confi gured factory-tested solutions are available in the Pesticide Explorer Collection to meet standard and high-resolution screening and quantitation needs. Each confi guration includes a liquid chromatography and mass spectrometry system, the Thermo Scientifi c QuEChERS sample extraction kit, HPLC columns, and proven multi-class pesticide residue analysis data acquisition and processing methods using the Thermo Scientifi c TraceFinder software. The software also allows laboratories to generate quantitative and qualitative reports for easy review and regulatory reporting.
For routine, targeted testing of pesticides, Thermo Scientifi c Pesticide Explorer Collection Standard Quantitation and Premier Quantitation packages include triple quadrupole mass spectrometers and validated workfl ows for quick and easy set-up and execution. For basic quantitation and robust performance, the Standard Quantitation option includes the Thermo Scientifi c TSQ Endura triple quadrupole MS, while the Premier Quantitation package offers higher sensitivity quantitation and performance provided by the Thermo Scientifi c TSQ Quantiva triple quadrupole MS.
For laboratories offering specialised analytical services requiring HRAM sensitivity, the Orbitrap HRAM Quantitation and Orbitrap HRAM Screening and Quantitation packages include the Thermo Scientifi c Q Exactive Focus MS, which enables scientists to generate data for highly sensitive and selective quantitation as well as for in-depth screening. These packages also include a built-in HRAM Spectral Library and Compound Database designed specifi cally for food safety and environmental analyses using HRAM instruments.
The Orbitrap HRAM Screening and Quantitation package is a complete solution for unknown screening and identifi cation, and also includes Thermo Scientifi c SIEVE software for differential analysis and Thermo Scientifi c Compound Discoverer software for identifi cation of the degradents and metabolites of known target compounds.
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