A method for determining the volatility of active ingredients used in plant protection

Abstract

The paper describes a gravimetric method of determining the volatility (evaporation rate) of pesticides. The measuring apparatus may be set at any temperature between ∼15 and 80°C; the dry air flowing through the apparatus is regulated by valves between ‐0.2 1/h and 300 1/h. Figures available for vapour pressure reveal a mathematical relation between vapour pressure and evaporation rate. This can be used as a simple method of determining the vapour pressure of any substance at 20°C by determining the evaporation rate when the air current is flowing at 50 l/h. The effects of the temperature and the air flow rate on the evaporation rate are also analysed.

Methods for determining the vapour pressure of active ingredients used in crop protection. Part V: Thermogravimetry combined with solid phase microextraction (SPME)

“…7. Dependence of the SPME/GC peak area on the extraction time for fenpropimorph (1), extracted at room temperature with three di †erent Ðbres with the same coating thickness (100 lm PDMS).…”

A fit of the vapours

“…Of particular interest was a series of papers by Gückel et al who measured the volatilisation rates of pesticides at ambient pressure by isothermal thermogravimetry [16][17][18][19]. Their initial studies employed a thermostatically-housed balance purged with a pre-heated air stream from which they established a double logarithmic relationship between the rate of amount of substance lost per unit area (expressed as mol h À1 cm À2 ) and the material's vapour pressure [16].…”

“…[-dM/dt / mo l s -1 m -2 ] Relationship between molar volatilisation rate and vapour pressure for benzoic acid, benzophenone, phenanthrene and acetamide according to the method of Gückel et al[16][17][18] using data from Price and Hawkins[1].…”

Characterization of peroxide-based explosives by thermal analysis

“…Several studies mention thermal gravimetric analysis as a rapid and convenient method to characterize the vapor pressure curves and enthalpies of sublimation and vaporization of volatile materials. Guekel et al [2] measured the volatilization rates of pesticides at ambient pressure by isothermal thermogravimetry. Other groups have used the techniques to estimate the vapor pressure of pharmaceutical compounds.…”