Effective and rugged analysis of glyphosate, glufosinate, and metabolites in Tenebrio molitor larva (mealworms) using liquid chromatography tandem mass spectrometry.

Tenebrio molitor larva (mealworms) has recently attracted attention as a protein source for food and feed. The larva is generally fed with wheat bran, which can be possibly contaminated with glyphosate. To establish food safe standards, a rugged and effective analytical method for glyphosate, aminomethylphosphonic acid, glufosinate, and their metabolites including 3-methylphosphinico-propionic acid, and N-acetyl glufosinate, in mealworms was optimized using liquid chromatography tandem mass spectrometry. An anionic polar pesticide column was used due to its high suitability for glyphosate. Acidified water and acetonitrile were used to extract the target compounds without contribution from various fatty and pigment interferences derived from brownish insects. Seven different clean-up procedures ((1) 50 mg C18 (2) 20 mg C18/Z-sep (3) PRiME hydrophilic-lipophilic balance (HLB) cartridge (4) 75 mg Z-sep, (5) 75 mg Z-sep+, (6) EMR-lipid cartridge, and (7) 50 mg ENVI-Carb) were compared. Due to its simplicity and cost-effectiveness, PRiME HLB was selected for clean-up. The recoveries of the target compounds were ranged from 86 to 96% with < 20% relative standard deviations. Therefore, this simple and effective method can be applied for the two pesticides and their metabolites in other edible insects or high-fat matrices.

Vapor phase toxicity of marjoram oil compounds and their related monoterpenoids to Blattella germanica (Orthoptera: Blattellidae).

The toxicity of marjoram, Origanum majorana L., oil, 41 monoterpenoids, and 2 sesquiterpenoids against adult females of the German cockroach, Blattella germanica L., was examined using direct contact and vapor phase toxicity bioassays and compared with those of deltamethrin, dichlorvos, permethrin, and propoxur, four commonly used insecticides. In a filter-paper contact toxicity bioassay, the adulticidal activities of pulegone (0.06 mg/cm2), (+/-)-camphor (0.07 mg/cm2), and verbenone (0.07 mg/cm2) were comparable to that of permethrin (0.05 mg/cm2) but more pronounced than that of propoxur (0.18 mg/cm2), as judged by the 24-h LC50 values. These compounds were less effective than either deltamethrin (0.013 mg/cm2) or dichlorvos (0.007 mg/cm2). The toxicity of marjoram oil, thymol, alpha-terpineol, (-)-alpha-thujone, linalool, 1,8-cineole, (-)-camphor, and (+)-carvone, ranging from 0.08 to 0.18 mg/cm2, was higher than that of propoxur. In vapor phase toxicity tests, verbenone (11.48 mg/L air) was the most toxic compound followed by (-)-alpha-thujone (18.43 mg/L of air), thymol (18.76 mg/L of air), alpha-terpineol (21.89 mg/L of air), (+/-)-camphor (24.59 mg/L of air), linalool (26.20 mg/L of air), and marjoram oil (38.28 mg/L of air) on the basis of the 24-h LC50 values. Dichlorvos (0.07 mg/L of air) was the most potent fumigant. Structure-activity relationships indicate that structural characteristics, such as degrees of saturation and types of functional groups rather than types of carbon skeleton, and hydrophobicity and vapor pressure parameters appear to play a role in determining the monoterpenoid toxicities to adult B. germanica. Marjoram oil and the monoterpenoids described merit further study as potential fumigants or leads for the control of B. germanica.