Organophosphorus compounds, vapor

Pyrethroids generally have low vapor pressures. Although empenthrin (20) volatilizes at room temperature without external energy and is 31 times more volatile than allethrin, its vapor pressure is only 1/88 that of dichlorvos, a volatile organophosphorus compound. As profluthrin (40) is 13 times more volatile than allethrin and volatilizes gradually for 6 months to 1 year at room temperature, it is suitable as an insecticide for the protection of clothes. The vapor pressure of profluthrin is 10 mPa/25°C, almost the same as that of glycerin. 

Microsensor Systems, Inc. (Fairfax, VA) offers SAW devices and coatings for organophosphorus compounds, aromatic hydrocarbons, water vapor, and others. A four-sensor array consisting of four 158 MHz dual-delay-line oscillators and a portable gas chromatograph with an SAW detector are also available. 

Fumigant action of some organophosphorus compounds was related to their vapor pressures and the water content of the soil. Phorate, disulfoton, and dimethoate were equally eflEective in soils in wet years, but only phorate and disulfoton were eflEective in dry years (326). Phorate and disulfoton provided much vapor action in dry years because of their high vapor pressures whereas dimethoate did not. 

One of the best-recognized quantitative patterns in mobility spectra is the relationship between protonated monomers and proton-bound dimers, common to several types of compounds, including esters, ketones, alcohols, amines, and organophosphorus compounds. As the vapor concentration of the analyte M is increased in an ion source, a protonated monomer peak first appears with a corresponding decrease in the reactant ion peak intensity. The reaction yields an energetically excited intermediate adduct ion or transition state ([MH+(H20) ] ) that may dissociate back to the reactants or may form product ions through other reaction pathways. Such reaction pathways involve a third body Z to stabilize the products, as shown in Equation 11.4 ... 

The use of a direct event for indication of analyte presence and concentration allow this detection technique to be used in real time. This, together with the broad nature of the detection protocols, makes the sensor system ideally suited for application as an early warning device. The surfaces can be used for repeated assays throughout their frmctional lifetimes and are exceptionally sensitive, with limits of detection for organophosphorus compounds below the current safe drinking water standards (75, 14, 17, 18, 44). In addition to detection of a variety of analytes in solution (70, 12-18), these enzyme based surfaces have been applied to the detection of GB vapor as well as gaseous carbon dioxide 16, 18). 

Ren, D., Gellman, A. TnitiaT steps in the surface chemistry of vapor phase lubrication by organophosphorus compounds. TriboL Lett. 6, 191-194 (1999). doi 10.1023/A 1019184312290... 

Boublik, T., Fried, V., Hala, E. (1984) The Vapor Pressure of Pure Substances, 2nd revised Edition, Elsevier, Amsterdam, The Netherlands. Bowman, B. T., Sans, W. W. (1983) Determination of octanol-water partitioning coefficient (KqW) of 61 organophosphorus and carbamate insecticides and their relationship to respective water solubility (S) values. J. Environ. Sci. Health B18, 667-683. Bradley, R. S., Cleasby, T. G. (1953) The vapour pressure and lattice energy of some aromatic ring compounds. J. Chem. Soc. 1953, 1690-1692. 

Other important GC detectors include the thermionic detector, the electrolytic conductivity or Hall detector, and the photoionization detector. The thermionic detector is similar in construction to the FID. With the thermionic detector, nitrogen- and phosphorus-containing compounds produce increased currents in a flame in which an alkali metal salt is vaporized. The thermionic detector is widely used for organophosphorus pesticides and pharmaceutical compounds. 

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