r. pakzad

Macrocyclic lactones include two groups of common pesticides with a wide anti-parasitic spectrum, which are used to control immature nematodes and arthropods. Due to the potential adverse effects of the residues of these compounds in agricultural products, the aim of this study was to provide a reliable method for the simultaneous analysis of the pesticides in bell peppers as representative of high water content commodity groups using liquid chromatography tandem mass spectrometry.

Sample preparation was based on EN 15662 method with minor modifications using acetonitrile extraction in a buffer solution and PSA and GCB adsorbents. To overcome the matrix effect, calibration curves were plotted based on the matrix match approach in presence of the internal standard. Validation of the method included linearity, accuracy and precision studies, as well as calculation of the limits of detection and quantitation.

Results showed that the method was linear in the range of 10–150 ng ml-1 with a correlation coefficient greater than 0.995. In addition, extraction recovery was 75.6–128% and precision of method based on RSD% was 2.8–22.8%. Detection limit of the method (except for Avermectin B1b and Moxidectin) was 3 ng g-1 and the limit of quantification (except for the two pesticides) was 10 ng g-1.

Results showed that the present method included the necessary validity for analyzing the addressed pesticides of macrocyclic lactones.

Calculation of Cronbach's Alpha which measures the internal reliability of a tool is easy, but misuse and misconception are widely observed. Common misunderstandings of the Cronbach's Alpha include inability to differentiate between being one-dimensional and consistency, and between raw and standardized alpha. Violations of the assumptions of alpha could also cause an increase or decrease in the calculated alpha. In this paper, we showed that a very large but confusing alpha coefficient could be obtained, particularly when the one-dimensional theory is violated. Also, the use of standard error measurement as an index of the reliability has been presented. Finally, the generalizability of alpha coefficient is also discussed.