Lipophilic pesticides

A new synthetic carbanaceous resin (Rohm and Haas) (12) has been found to be very effective for holding up non polar interferences from fats and oils while allowing many lipophilic pesticides to be quantitatively eluted. This was adapted to automated elution and was found out to also be recyclable. Acetonitrile is used for eluting the pesticides and chloroform is used for recycling the column by displacing the adsorbed interferences. 

Another example of a relevant toxin effect is evidence that chronic, systemic inhibition of complex I by the lipophilic pesticide rotenone causes highly selective degeneration of nigrostriatal DA neurons that can produce hypokinesia and rigidity, as well as accumulation of fibrillar cytoplasmic inclusions that contain ubiquitin and a-synuclein (75). These findings lend additional support to the view that environmental toxic factors may contribute to risk of PD. 

According to our experiments, the solubility of vegetable oil in raw QuEChERS extracts is -4 mg/mL (-40 mg in 10 mb). In the presence of water, the solubility is slightly lower ( 2 mg/mL). Due to this low solubility, excess lipids form an additional layer into which highly lipophilic pesticides tend to parhhon. The parhtioning rate depends on the peshcide s Hpophilicity, the lipid/acetonitrile raho as well as on the presence or absence of water, which obviously modifies the polarity of the acetonitrile phase, making it less receptive for lipophilic compounds. 

The sample weights suggested in Table I constitute a compromise between the recoveries of the lipophilic pesticides, the limits of detection, and the subsampling variability. For the commodity groups A-E, the sample weights given in the table ensure HCB-recoveries > 70%. For the commodity groups F-H,... 

Figure 4. Recoveries of lipophilic pesticides at various oil amounts in presence or absence of water.

In the case of fatty foods, the analysis is commonly aimed at lipophilic pesticides, such as organochlo-rines (OC), that accumulate in lipidic tissues and may be persistent, posing a great risk to both consumers and the environment. 

Compounds less polar than pesticides that separate from pesticides in a rmre polar layer to a less polar one e.g., removal of lipids from acetonitrile extracts by LLP with hexane (loss of lipophilic pesticides) Ionic compounds from neutral pesticides or neutral compounds from ionic pesticides by pH adjustment in the aqueous layer... 

Microporous membrane liquid-liquid extraction of lipophilic pesticides in biological fluids combines the size exclusion properties of the membrane, reducing lipid coextraction, with the stirring capabilities of the sample phase together with the permanent pumping of the organic phase. 

Matrix solid-phase dispersion (MSPD) is an SPE variant where samples are ground and mixed with a support. In the initial application, samples were placed in a disposable column previously packed with Florisil, which trapped the fat from the sample and allowed the compounds of interest to be eluted. This has successfully been applied to the determination of lipophilic pesticides from both fatty and non-fatty matrixes. Recently, an orthogonal technique, dispersive solid-phase extraction, for the isolation and analysis of a variety of pesticides on numerous food matrixes has been introduced. The technique is called QuEChERS, which stands for quick, easy, cheap, effective, rugged, and safe. The technique offers advantages in time and solvent usage since it uses approximately 10 ml of solvent per sample when compared to the potentially hundreds of milliliters of solvent used for more standard extraction and isolation protocols. It uses a combination of MgS04 and primary secondary amine (PSA) sorbent not only to remove water and non-target compounds, but also isolate the compounds of interest. 

Microparticles. Size matters release rates depend on surface area, ie, a function of the square of the radius of a spherical particle, and thus larger particles release for longer and are able to manipulate the external availability of the pesticide. Small microparticles are therefore limited in their scope for controlling release but can be used in traditional spraying of dispersions onto soils and crops as well as for seed dressing. Suspension concentrate formulations of matrix microparticles have been developed based on various rosins, phenoUc resins, waxes, and bitumens. These have focused on lipophilic pesticides such as trifluralin and chlorpyrifos and reductions in volatility have been demonstrated (43). 

The amounts of pesticides passing from raw materials into fruit juices depend on the distribution of residues between the solid (skin or flesh) and liquid fruit portions. Moderately to highly lipophilic pesticides, such as parathion, captan, folpet or synthetic pyrethroids, usually pass to the raw juices only to a very limited extent. A further decrease of their contents may occur during operations such as clarification or ultrafiltration. The risk of infiltration of residues into the human food chain, however, exists when the solid waste with higher concentrations of pesticides is used as an animal feed. 

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