70 FOOD & DRINK TECHNOLOGY
Scientific demonstrates how a novel online sample preparation technique could be used as an alternative to the QuEChERS (a portmanteau word created from Quick, Easy, Cheap, Effective, Rugged and Safe) method for high throughput LC-MS/MS pesticide analysis in grapes, baby food and wheat flour.
European Regulation 396/2005 sets maximum residue levels of pesticides in different products of plant and animal origin. Tese regulations present a significant analytical challenge with respect to the low limits of quantification which are required for some specified food matrices such as baby food.
Many gas chromatography (GC) and high pressure liquid chromatography (HPLC) methods have been developed for multi-residue determination of pesticides and are in widespread use – employing a variety of sample preparation and clean-up techniques.
Streamlined approach In recent years the QuEChERS method has become widely adopted for handling fruit and vegetables. It is a streamlined approach which makes it easier and less expensive for analytical chemists to examine pesticide residues in food.
However, QuEChERS does require many manual sample
manipulation steps, making it labour-intensive when large numbers of samples have to be analysed.
It is therefore beneficial to consider options for automation of multi-residue methods, which can be cost-effective and can offer a high degree of reliability in recovery and repeatability.
While the preliminary stages of homogenisation and solvent extraction of food matrices inevitably require manual intervention, once a crude extract has been obtained, the procedure is fully automated thereafter.
Automated procedure Tis automated procedure is included in the method, which utilises turbulent flow chromatography with online liquid chromatography-mass spectrometry (LC-MS/MS).
Termo Scientific’s multi- residue pesticide method can be applied to fruits, cereals and composite baby foods at limits of detection (LODs) in the range of 0.8-10.3 µg/kg which are below respective European Union maximum residue limits (MRLs).
Te method has now been validated for a total of 48 pesticides from different classes, but this can be readily extended to a larger number of residues.
Sample concentration, clean-up and analytical separation are carried out in a single run using an online coupled turbulent flow chromatography – Termo Scientific’s Transcend TLX system powered by Termo Scientific TurboFlow technology. TurboFlow technology enables very effective separation of matrix and target compounds – resulting in relatively clean sample extracts.
Cost-effective According to Termo Scientific, using TurboFlow technology enables convenient, fast and cost-effective automated determination of selected pesticides, from polar to non- polar compound chemistry, in different matrix types.
Based on the short total run time and Transcend system with TurboFlow technology, a total of 100 samples per day can now be analysed under controlled sample preparation conditions.
Method performance characteristics were established by in-house validation for baby food, grapes and wheat flour matrices.
“Te method performance indicates it is suitable for routine use for regulatory purposes and can be readily extended to a larger and wider range of pesticide residues,” concludes the application note.
Screening for sulphonamides and Trifluralin A
s an antimicrobial agent, sulphonamides are used in global food production to treat/prevent infections. However, serious health concerns
exist over human consumption and the development of antibiotic resistance. As a result, many countries have banned or limited their use in animal production and set maximum residue limits (MRLs) for residues in food. Randox Food Diagnostics meat & seafood manager Joanne McKnight said, “Standard products on the market are based on generic antibodies designed
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to detect a range of sulphonamides. However that compromises the performance of each individual compound. Both our Biochip Array Technology and ELISA products are based on specific antibodies for each individual sulphonamide so this reduces reliance on cross-reactivity and increases accuracy. Feedback from customers to date has been very positive, as investing in quality screening reduces false positives, and dramatically cuts associated costs with superfluous confirmatory testing. The company has also developed an ELISA for
the herbicide Trifluralin. While the World Health Organisation has classified the herbicide as unlikely to present an acute hazard in normal use, Japan, for example, closely inspects shrimp imports from Vietnam for its presence. Japan has warned that any detection of Trifluralin and it would immediately impose a 100% inspection regime on shrimps. Randox developed its ELISA in response to this and limits of 0.17ppb can be achieved using a simple sample preparation. Forty samples can be prepared in less than three hours and assay time to results is 90 minutes.
“A lot of scientific effort has been spent to develop a rapid, reliable, cost effective analytical approach for measurement of adulteration of olive oils with other oils.”
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