The photochemical behaviour of five household pyrethroid insecticides and a synergist as studied by photo-solid-phase microextraction

Abstract

In the present study, solid-phase microextraction in photochemical studies was used to investigate UV light induced photodegradation of five pyrethroids (empenthrin, transfluthrin, allethrin, phenothrin and cyphenothrin) and a synergist (piperonyl butoxide), which are common ingredients of household insecticides. Gas chromatography coupled with mass spectrometry was used to separate and tentatively identify the parent compounds and their corresponding photoproducts generated in the same polydimethylsiloxane fibre. Kinetics curves were obtained and apparent first-order rate constants and half-lives were estimated. Twenty-six photoproducts were tentatively identified and photodegradation pathways for the compounds investigated were proposed. It is a matter of some concern that three of the photoproducts identified [(3-(2,2-dichlorovinyl)-2,2-dimethylcyclopropanecarboxylic acid, 3-phenoxybenzaldehyde and (3-phenoxyphenyl)methanol] have been reported to be endocrine disruptors. There is no record of previous studies of cyphenothrin and empenthrin photodegradation, and therefore the present study represents the first attempt to elucidate the photochemical behaviour of these compounds. Figure Photo-SPME for Pyrethroids.

Investigation of the photochemical behaviour of pyrethroids lacking the cyclopropane ring by photo‐solid‐phase microextraction and gas chromatography/mass spectrometry

“…Previous studies of the photodecomposition of pyrethroids indicate that decarboxylation is an important reaction pathway for their degradation 5, 6, 10. Several compounds tentatively identified as pyrethroid photoproducts may be generated by loss of CO 2 and subsequent loss of other moieties (FP 4, FLU 6‐8, FEN 7‐8 in Tables 3–5).…”

“…Several years ago, photo‐solid‐phase microextraction (photo‐SPME) was proposed as a support for phototransformation studies of organic compounds such as musks,2 polychlorinated biphenyls,3 and organochlorine4 and pyrethroid pesticides 5, 6. In photo‐SPME, the organic analytes are extracted and then directly photodegraded on the SPME fibre coating, so that the whole system (parent compounds and photoproducts) can be analyzed simultaneously, and this brings many advantages compared with classical photodegradation studies 7…”

Use of the HS-PTR-MS for online measurements of pyrethroids during indoor insecticide treatments

“…In contrast, the measurement frequency drops to one measurement per minute or less with the HS-PTR-MS, potentially for extended periods of measurement time (24 h or more). Moreover, no pretreatment of the sample is required, which involves potential risk of analyte loss, e.g., during transport, storage, extraction, and cleanup [46,54] or through photodecomposition [40,55]. Finally, the implementation and the use of the analytical device for experimental study are relatively easy once the initial parameters are adjusted.…”

Synthesis, insecticidal activities and resistance in Aedes albopictus and cytotoxicity of novel dihaloacetylated heterocyclic pyrethroids

“…Reagents and solvents not listed and not specified were purchased from commercial suppliers. [11][12][13][14][15][16][17][18][19][20][21][22][23][24] However, since the synthesized compound contains small amount of impurities and the area integral in the 1 H NMR spectrum is substantially less than 0.5, it is difficult to accurately determine the content thereof. Because the synthesized compounds are all novel compounds, and the exact purity of the compound cannot be determined by the HPLC absorption peak, only rough values of the initial purity determined by NMR are given in the following compound data.…”