Use of an Efficient Measurement Uncertainty Approach To Compare Room Temperature and Cryogenic Sample Processing in the Analysis of Chemical Contaminants in Foods

Abstract

In this study, analytical results were compared when using different approaches to bulk food sample comminution, consisting of a vertical chopper (Blixer) at room temperature and dry ice cryogenic conditions, followed by further subsample processing (20 g) using liquid nitrogen cryogenic conditions (cryomill). Analysis of the 43 targeted spiked and incurred contaminants in a food mixture consisting of equal parts orange, apple, kale, salmon, and croaker involved quick, easy, cheap, effective, rugged, and safe (QuEChERS) with automated mini-column solid-phase extraction (known as ITSP) cleanup, followed by low-pressure gas chromatography-tandem mass spectrometry (LPGC-MS/MS). Different ambient Blixer test portion sizes of 20, 10, 5, 2, and 1 g were assessed, and for cryogenic Blixer conditions, a 0.5 g test portion was also tested. In the case of the cryomill, test portions were 2, 1, and 0.5 g and all subsamples in all cases entailed five replicates. Determined concentrations and precisions (CV) of the analytes were compared to assess possible differences in systematic and random forms of error. A quality control spike was made before each step in the procedures to isolate that individual step in the uncertainty measurements using the error propagation sum of squares approach. Results indicated that the uncertainty of the sample preparation and LPGC-MS/MS analysis steps were 2-7 and 11% CV, respectively, while uncertainties of sample processing ranged from 6% CV for the cryomill to 12% CV for the ambient Blixer conditions. The common use of internal standards reduced overall method uncertainty from 12-15 to 7-10% CV. For the analytes, matrix, conditions, and tools used in this study, the minimal test sample weight that gave satisfactory recoveries and precision was found to be 1 g in all cases.

Assessment of Test Portion Sizes after Sample Comminution with Liquid Nitrogen in an Improved High-Throughput Method for Analysis of Pesticide Residues in Fruits and Vegetables

“…The cleanup was performed just-in-time for injection in parallel as the previous cleaned-up sample was being analyzed via LPGC-MS/MS as described previously. 4,5,[24][25][26] Preparation of calibration standards.…”

“…As described in Materials and Methods and previously, 4,5 the RSDs of the results were used to calculate the isolated CV components in the method(s) to estimate measurement uncertainties with and without use of an int. std.…”

“…Recently, a series of articles have been published in an attempt to change that oversight among analytical chemists in the pesticide residue analysis community. [1][2][3][4][5][6][7][8][9][10] Regulatory purposes require that bulk commodities typically >1 kg be collected and processed to yield pesticide determinations that accurately correspond to the original sample lot (e.g. shipment or warehouse).…”

Miniaturization of an extraction protocol for the monitoring of pesticides and polar transformation products in biotic matrices

“…As masses of MI samples are very low, the effect of miniaturization was first investigated on fish, and then applied and validated on MIs. Special attention was paid to the validation phase in order to guarantee the reliability and accuracy of the method as it is well known that decreasing the reduction of the sample mass increases the variability of the measurement (Han et al, 2018;Lehotay et al, 2018).…”

Influences of sample homogenization time and standing time before extraction on the determination of incurred pesticide residue levels in grapes

“…[1][2][3][4][5][6] It is also necessary to prepare an adequate sample homogenate with fine particles to reduce the uncertainty induced by errors in weighing the extract portions analyzed and to ensure sufficient extraction efficiency for pesticide residues in the samples. [6][7][8][9][10] It is necessary to weigh extract portions from a sample homogenate without a bias in content between the peel and pulp portions of fruits, because the majority of pesticide residues from foliage ap-plication with short pre-harvest intervals are present in the peels of fruits such as melons. 11) Similarly, it is necessary to prepare a sample homogenate without a bias in content between the outer and inner leaves of wrapped leafy vegetables such as cabbage, because the majority of pesticide residues from foliage application are present in the outer leaves.…”