LGC AXIO Proficiency Testing | Emerging Pollutants of Environmental Concern | Volume 1 | Neonicotinoids
AXIO Proficiency Testing Insights into Testing Methods Although the concentrations of the Neonicotinoids in environmental materials are low, typically around 1-10 ng/L, in the AXIO Proficiency Testing AQUACHECK scheme, samples are provided at similar concentrations for the analysis of a range of pesticide residues, such as phenoxy herbicides, triazine herbicides, phenylurea herbicides, insecticides and fungicides. The results returned by participants for these samples typically results in a high proportion of satisfactory performance scores. The increasing use of direct injection methods for the analysis of pesticides at concentrations of environmental concern has typically resulted in a smaller spread of data, as measured by the robust standard deviation, due to the removal of sample preparation steps and a consequential reduction in the measurement uncertainty. This improvement in method performance as participants adopt this technology, has resulted in a subsequent increase in the proportion of results which receive a satisfactory performance score.
Analytical Methodology & Techniques Neonicotinoids, in common with many other insecticides, are detected by traditional methods such as gas chromatography coupled with different detectors and liquid chromatography-mass spectrometry (LC-MS, LC-MS/MS), which have been shown to have low detection limits and acceptable sensitivity and selectivity [4]. In the quantitative analysis of neonicotinoids, sample preparation is typically carried out in order to remove interfering species and increase the concentration of the analyte(s) in the test sample. Almost all of the common sample preparation methods (liquid-liquid extraction, solid phase micro-extraction, dispersive solid phase extraction) have been applied to the determination of neonicotinoids however the use of solid phase extraction (SPE) is one which has been extremely widely reported. After extraction, gas chromatography (GC) and liquid chromatography (LC) techniques are applied for the simultaneous measurement of the neonicotinoids and their important metabolites. Many of the analytical methods reported employ mass spectrometry detection, as this can offer better sensitivity for the compounds of interest. Where a simple matrix is being analysed, the use of LC-MS/MS for the final measurement, has enabled the simultaneous analysis of multiple neonicotinoids without any sample preparation [11]. Detection limits using GC and LC methods, have been reported within the range from 0.1 to 1 ng/l, although the limits of detection for some of the metabolites may be slightly higher [4].
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