GC/MS. This is a highly sensitive and universal detecting system that most people encounter at airports, where it is used to detect substances in luggage or on passengers. Able to detect trace elements down to ppm and ppb, which appear as chromatographic peaks on a chromatogram, GC/MS is frequently used to detect a wide variety of analytes within a single sample matrix, such as pesticide residues in food. GC/MS can also be used to help identify unknown pesticide elements by comparing their relative retention time data to that of a standard, such as chlorpyrifos that is typically used as the standard for common chlorinated hydrocarbon and organophosphate pesticides.
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LC/TOF-MS. A newer, more sensitive, and faster technology for pesticide analysis is liquid chromatography/time-of-flight mass spectroscopy, or LC/TOF-MS. Basically, the system determines an ion’s mass-to-charge ratio by measuring the time it takes for an ion to reach a detector that is set at a predetermined distance. That time measures the ion’s velocity and is used to determine its weight, or mass-to-charge ratio, which in turn helps to identify the specific ion. Since LC/TOF-MS collects full spectrum information on samples, the mass spectrometer can examine the data for non-targeted (or unknowns) as well as targeted information that is stored in a spectra database. Using a standard sample preparation procedure like QuEChERS (Quick, Easy, Cheap, Effective, Rugged, and Safe), a LC/TOF mass spectrometer like the PerkinElmer AxION 2 TOF provides lab scientists with the ability to rapidly detect hundreds of commonly regulated pesticides in food at or below the regulatory limit of 10 ppb in concentration. These instruments can also quickly and automatically highlight those residual amounts of pesticides that are above the regulatory limit. LC/TOF technology is an example of how to detect residual amounts of neonicotoid pesticides in honey, which are now the most commonly used insecticide class in the world and are currently under investigation as a possible cause for bee colony collapse disorder.
LC/MS/MS. Liquid chromatography coupled to triple quadrupole mass spectrometry (LC/MS/MS), or triple quadrupole system, is becoming the method of choice for the detection of multiple residual pesticides in food, nutraceuticals, and botanicals. LC/MS/MS systems have a unique detection mode called multiple reaction monitoring, which allows the first quadruple in the system to select the parent ion mass of the analyte before sending them to collision cell for fragmentation. Following this the second quadrupole is able to select daughter ion from those parent ions and send them to the detector for detection. The unique parent/daughter ions combination provides high specificity, selectivity, and sensitivity. Using systems such as the PerkinElmer Altus UPLC system coupled to a QSight 220 triple-quad mass spectrometer can allow lab scientists to identify and simultaneously quantify the trace residue of multiple pesticides in fruit faster than other GC technologies.
In addition, portable GC systems are available when the lab is needed onsite. For example, the 32-pound Torion T-9 GC/MS by PerkinElmer can provide rapid screening of chemicals in food safety applications.
When it comes to flexibility, speed, and accuracy in testing for residual pesticides in food to meet global regulatory requirements there is a wealth of chromatographic options to help make the next family dinner be as pesticide free as possible.
Qin is product manager for food solutions at PerkinElmer. Reach him at email@example.com.