Analysis of thermally labile pesticides by on-column injection gas chromatography in fruit and vegetables

Abstract

Thermally labile pesticides (captafol, captan, dicofol, and folpet) are highly prone to suffer thermal degradation during sample introduction into a gas chromatograph (GC) to tetrahydrophthalimide (THPI), 4,4'-dichlorobenzophenone (DCBP), and phthalimide (PI), respectively, mainly produced in the glass liner of the injector. This undesired behavior leads to inaccurate qualitative and quantitative results. Direct on-column injection (OCI) technique is evaluated as an alternative to avoid or minimize compound alteration during the analysis. This configuration was studied and evaluated for the determination of this group of thermally troublesome pesticides. The OCI inlet was operated in "track oven" temperature and connected to a wide-bore deactivated guard column that is itself connected to a capillary GC analytical column. This technique has demonstrated to be useful for avoiding degradation generated in the hot inlet. Limitations observed for OCI in routine analysis were injection volume, guard column length, and maintenance issues. Analytical standards spiked in vegetable solutions were injected in OCI, not observing any thermal degradation rate. On the contrary, classical splitless injection (SLI) produced high degradation rates in all cases. This OCI approach was validated in citrate QuEChERS extracts of tomato, apple, and orange matrices for these four compounds and their corresponding transformation products (THPI, DCBP, and PI), evaluating recoveries, repeatability, linearity, and matrix effect. This set-up enabled the correct identification and quantitation for most compounds at LOQs of 0.010 mg/kg in fruit and vegetable samples. The OCI grants evident differentiation between metabolites naturally occurring in food and thermal degradation products created during the analysis. Graphical abstract ᅟ.

Determination of multiclass, semi-polar pesticide residues in fatty fish muscle tissue by gas and liquid chromatography mass spectrometry

“…This adsorbent, a primary and secondary amine, can interact with acidic compounds yielding low recoveries after the clean-up step. Folpet is widely reported as a troublesome compound for GC–MS analysis because of its thermal degradation [6]. Moreover, it is reported that chlorothalonil presents recovery problems in some matrices when extracted with acetonitrile.…”

Advancement of Phenoxypyridine as an Active Scaffold for Pesticides

“…At present, PPO-inhibiting herbicides mainly include diphenyl ethers, phenylpyrazoles, triazolinones, N -phenyl phthalimides, and diazoles [ 39 ]. Among these herbicides, diphenyl ethers (DPEs) [ 40 ] had been widely studied by researchers in the creation of novel pesticides due to their high efficiency, low toxicity, high selectivity, and simple synthesis process; Ye Fei’s team committed to the research and development of PPO inhibitors for a long time. Several series of compounds ( Figure 4 ) containing phenoxypyridine had been designed, studied for greenhouse herbicidal activity, PPO inhibitory activity, crop selectivity, and structure-activity relationships (SARs).…”

Design, Synthesis, and Herbicidal Activity of Novel Diphenyl Ether Derivatives Containing Fast Degrading Tetrahydrophthalimide

“…On the one hand, substructure splicing is a widely used method for inventing novel drugs. The use of substructure splicing or parallel synthesis to optimize specific structures has led to a number of potential lead compounds and achieved great success in discovering new drug candidates. − On the other hand, tetrahydrophthalimide herbicides have many advantages, such as strong selectivity and no phytotoxicity to crops. , In addition, N -phenyl-phthalimide herbicide as another type of PPO inhibitor also has advantages of short residual time, fast degradation rate, and no pollution to the environment. For example, Flumioxazin has a degradation half-life of only 10.6–32.1 days in the field site at 15 and 25 °C and its degradation pathway is mainly through the opening of the imide ring, followed by the cleavage of the amide bond to form the corresponding dicarboxylic acid and aniline .…”