Organic Solvent-Free and Simple Method for Determining Cyromazine and Its Metabolite, Melamine, in Cow’s Milk

This paper described an organic solvent-free, rapid, simple, and space-saving method of sample preparation followed by HPLC coupled photo-diode array (PDA) detector for simultaneous quantification of cyromazine (CYR) and its decy-cropropylated metabolite, melamine (MEL), in milk. The HPLC-PDA was performed on an Inertsil? HILIC column with an isocratic aqueous mobile phase. Analytes were extracted from the sample using water, and purified by Mono-Spin?-C18, a centrifugal monolithic silica spin mini-columns, and quantified within 20 min. The method, performed under 100% aqueous conditions, obtained average recoveries for CYR and MEL in the range of 93.2% - 99.1% with relative standard deviations ≤ 2.8%. The quantitation limits were 8.5 ng/mL for CYR and 10 ng/mL for MEL, respectively. No organic solvents were used at any stage of the analysis.

Temporal-spatial analysis of cyromazine in cowpea using liquid chromatography–mass spectrometry coupled with mass spectrometry imaging

Background:Cowpea(Vigna unguiculata L.Walp.)is an economically important crop.It is nutritious and popular with consumers.However,it has been listed as one of the agricultural products of critical concern about safety in China and cyromazine is the major risk factor.Objectives:This study analyzed the dissipation and permeation kinetics of cyromazine residue in cowpea,to offer a scientific basis for the rational use of pesticide and ensure the safety of agricultural products.Materials and methods:The dissipation and residue level of the systemic insecticide cyromazine on cowpea under field and stored conditions were investigated.Subsequently,the spatial distribution of cyromazine was studied using mass spectrometry imaging to visualize the dynamic processes of permeation and migration in the tissues post pesticide application.Results:The dissipation processing of cyromazine in cowpea was shown to follow the first-order kinetics and half-life was 7.76 d in the field.In cowpea,the permeation and migration rate of cyromazine was faster than that in kidney beans and accumulation was mainly in the pulp.It is not safe to apply cyromazine to cowpeas with reference to the application method on kidney beans.Conclusions:These findings present vital data for the determination of risks linked with cowpea consumption and pesticide intake.

Chemiluminescent Determination of Cyromazine in Milk Samples Using Copper（III） Chelate-Triton X-100 by Flow Injection Analysis

Cyromazine（CYR） was determined in milk samples using copper（HI） chelate-Triton X-100 chemiluminescence（CL） system associated with flow-injection（FI） in KOH medium. The relative CL intensity for CYR concentration was linear over the range of 5×10^-4-10μg/mL（R2=0.9990, n=11） with injection rate of 160 h-1 and the relative standard deviation（RSD, n=4） of 1.2%-2.6%. The limit of detection（LOD） for signal-to-noise ratio of 3 was 1.5×10^4μg/mL. The influences of key chemical and physical parameters, some major fresh water ions at their maximum admissible concentrations and a number of pesticides were examined as potential interferences. The concentrations of CYR in spiked milk samples were successfully determined by the proposed method and the results were in good agreement with that of the previously reported HPLC method, having recovery range of （92% a=4%）-（106% a：2%）. The possible CL reaction mechanism for copper（m） chelate-Triton X-100-CYR was also briefly discussed.

Abamectin resistance in strains of vegetable leafminer, Liriomyza sativae （Diptera： Agromyzidae） is linked to elevated glutathione S-transferase activity

Abamectin resistance was selected in the vegetable leafminer, Liriomyza sativae （Blanchard） （Diptera： Agromyzidae） under laboratory conditions, and cross- resistance patterns and possible resistance mechanisms in the abamectin-resistant strains （AL-R, AF-R） were investigated. Compared with the susceptible strain （SS）, strain AL-R displayed 39-fold resistance to abamectin after 20 selection cycles during 25 generations, and strain AF-R exhibited 59-fold resistance to abamectin after 16 selection cycles during 22 generations. No cross-resistance to cyromazine was found in both abamectin-resistant strains. However, we failed to select for cyromazine resistance in L. sativae under laboratory conditions by conducting 17 selection cycles during 22 generations. However, moderate levels of cross-resistance to abamectin （6-9 fold） were observed in strains which received cyromazine treatments. Biochemical analysis showed that glutathione S-transferase （GST） activity in both abamectin-resistant strains （AL-R, AF-R） was significantly higher than in the susceptible strain （SS）, suggesting metabolically driven resistance to abamectinin L. sativae. Recommendations of mixtures or rotation of cyromazine and abamectin should be considered carefully, as consecutive cyromazine treatments may select for low-level cross-resistance to abamectin.