Addressing Pesticide Residue

“It was no longer cost effective to create a specific targeted analysis technique each time a new substance crossed our desks or was given a lower MRL,” Brown adds.

Instead, the company decided to look to new approaches. The idea was that a comprehensive technique would allow the company to benefit from a single, “generic” approach to achieving very low detection levels.

Key acronymn letters include: Q(quick), E(easy), C(cheap), E(effective), R(rugged) and S(safe). Taking advantage of the selectivity provided by the relatively new triple quadrupole mass spectroscopy (GC and LC) instrument and the recent development of the QuEChERS extraction technique, Law Labs developed a multi-class, multi-residue procedure for the routine monitoring of pesticides at or below U.K./EU maximum residue levels.

Minimizing Interference

To improve efficiencies and streamline the process, they turned to a new detection solution, a triple quadrupole MS system from Varian, Inc. (Palo Alto, Calif.) “The Varian system we’re using now minimizes potential interference from co-extractants.” Brown says. This allows for less stringent sample clean up and reduces the need for extra confirmation of residue identity. Law Labs uses both triple quad systems to determine a wider range of compound types. And for compounds that run on both types of systems, they are able to obtain additional confirmation of identity and quantification.

During the selection process for new analysis systems, the company tested instruments from each of the five leading manufacturers by spiking samples with a range of outdated and newly approved pesticides and performing a series of detection runs. Law Labs selected the Varian, Inc. system based on consistent performance, ruggedness and price and because Varian was the only company that had developed and offered a triple quad GC as well as an LC system. Law Labs needed the versatility offered by both the GC and LC methods with MS/MS but wanted the commonality found in a single supplier system.

In addition to benefiting from the improved instrumental capability, Law Labs employs the QuEChERS method for extraction developed by the USDA Wyndmoor Research Centre. Brown explained that Law Labs are the first in the UK to routinely use the technique.

“We were looking for an extraction which would save time and still be capable of extracting the widest possible range of compound types – QuEChERS is already widely used in Germany and the U.S.,” he adds.

With this method, the company has achieved significantly higher outputs while using 90 percent less solvent than with traditional methods. The pesticide residue determination is then performed using both the GC and LC with MS/MS calibrated with Matrix Matched Multiple Pesticide Standards at 4 levels.

Law Labs has validated the technique for around 160 compounds. Even pesticide classes like carbamates, macrocyclic lactones, morpholines and benzimidazoles that were traditionally difficult to analyze, can now be detected with a single extract.

Especially in Europe where the public continues to view GMO foods and pesticide residue as very significant issues, the large retail chains are choosy about their fruit and vegetable suppliers and the analysis process used to determine MRLs. Ideally the retailers are looking to turn this data into a competitive advantage but are also acutely aware of the damage adverse residue findings can have on their reputation and brand identity.

Companies like Law Labs have their work cut out for them. As consumers become more knowledgeable, detection limits in many countries are lowered further, and the WTO becomes more involved with the flourishing near-borderless market for produce.

“We are used to receiving weird and wonderful things from unusual locations,” Brown says. “One of our customers sends us dragon fruit from Vietnam, physalis from Columbia and native figs from Saudi Arabia. This customer also re-exports these same products through a distribution center in Belgium to Holland and Sweden. For good reason, we take our role in the supply chain very seriously and need to employ the most up to date and sophisticated instrumentation and methodologies available.”