Alkyl phosphates, determination

Alkyl benzene sulphate, determination of 439 Alkyl phosphates, determination of 292, 293... 

A recent method to screen the urine for alkyl phosphates as an indicator of exposure to organophosphate insecticides shows that the method can be used to determine environmental exposure to a specific organophosphate pesticide. The method was found to be sensitive, identifying low levels of exposure to insecticides in the environment by quantitation of urinary phosphates (Davies and Peterson 1997). The test is limited in that it is only useful for assessing recent exposure, due to the short half-life of the organophosphate pesticides. 

This technique has been used for the determination of polychlorobiphenyls, polychlorodibenzo-p-dioxins, polychlorodibenzofurans, alkyl phosphates, chlorinated insecticides, organophosphorus insecticides, triazine herbicides. Dacthal insecticide, insecticide/herbicide mixtures, mixtures of organic compounds and organotin compounds in soils, and polyaromatic compounds, polychlorobiphenyls, chlorinated insecticides and organotin compounds in non-saline sediments and anionic surfactants in sludges. 

The above flame retardants, HMPN and TMP, along with another commercially available alkyl phosphate, triethyl phosphate (TEP), were systematically characterized by Xu et al. To quantify the flammability of the electrolytes so that the effectiveness of these flame retardants could be compared on a more reliable basis, these authors modified a standard test UL 94 HB, intended for solid polymer samples, and measured the self-extinguishing time (SET) instead of the universally used flame propagation rate. Compared with the UL 94 HB, this new quantity is more appropriate for the evaluation of the electrolytes of low flammability, since the electrolytes that are determined to be retarded or nonflammable by this method all showed zero flame propa-... 

Observations were made of lipid-protein phases in which the structure is determined mainly by the protein. Raman spectroscopy is a useful method for structure analysis of such phases. The structures described above were analyzed successfully by an x-ray diffraction technique. Lipid-protein complexes, however, are often amorphous, and alternative methods to study their structures are therefore needed. It was demonstrated that Raman spectroscopy can be used to obtain structural information about lipid-protein interaction (16, 17). It is thus possible to determine the conformation as well as the type of environment of the lipid molecules. With the protein, interpretation is more complicated. It is usually possible to determine whether the complex has the same protein conformation as the component used in the preparation, or, if a change occurs, it may be possible to correlate it with denaturation of the pure protein. For complexes formed by long-chain alkyl phosphates and insu-... 

The structure of diphosphallenic radical cations, generated from the allene ArP=C=PAr by electrochemical oxidation, has been examined using EPR spectroscopy. Ab initio calculations including correlation effects at the MP2 and MCSCF levels have determined that two rotamers exist compatible with Jahn-Teller distortion of the allene.146 Anodically generated radical cations of alkyl phosphites [(RO P] and silylphosphites [(RO)2POSiMe3] reacted with alkenes by initial attack at the C=C bond followed by electron transfer, deprotonation, and elimination of an alkyl or trimethylsilyl cation to form identical alkyl phosphate adducts.147 The electron ionization-induced McLafferty rearrangement of n-hexylphosphine afford the a-distonic radical cation CTEPH, the distinct reactivity of which suggests there is no... 

Since a variety of pesticides were used, the alkyl phosphates present in urine could not be related to a particular pesticide application. The method identified and quantitatively determined the alkyl phosphates derived from the organophosphates the men were applying. Values in unexposed workers varied from. 02 to. 24 ppm, and from. 02 to 2.4 ppm in unexposed workers. 

The Department has developed methods for monitoring the exposure of workers exposed to organophosphate and carbamate pesticides. These methods utilize the determination of plasma and red blood cell cholinesterase activities and urinary alkyl phosphates. Studies are reported vrti ich show that these methods have proven useful in evaluating the safety effectiveness of closed-transfer systems and in determining reentry times for field workers. 

Exposure to organophosphate pesticides is often measured by determination of alkyl phosphate or phenol metabolites in the urine. Determination of blood cholinesterase activity can be a valuable indicator of exposure if pre-exposure cholinesterase activity is known (3, 5). Since normal cholinesterase levels... 

The most commonly used analytical methods for the quantification of the six alkyl phosphates are based on their purification from acidified samples via liquid-liquid extraction. This is followed by their conversion to volatile derivatives which can be detected using GC-MS or GC-FPD. In Table 9.4 some analytical procedures for the determination of the above substances in biological samples are listed. 

Barr et al. and Bravo et al. used a different technique for sample preparation and determination of alkyl phosphates in urine the urine was spiked with internal standard and then concentrated to dryness via azeotrope codistillation with acetonitrile. The residue was dissolved in acetonitrile, derivatized and then analyzed using GC-MS. Both studies reported satisfactory validation data with coefficients of variation of <20%. 

Moate et al. and Kupfermann et al. presented analytical methods involving SPE for the extraction of alkyl phosphates from urine. Moate et alf used SPE for sample cleanup followed by azeotrope distillation and then derivatization of the analytes. Determination of the analytes was achieved using GC-FPD. In contrast, Kupfermann et alf purified the derivatized extract of urine samples from a case of OP poisoning on silica SPE columns followed by quantitative analysis by GC-MS. The LODs ranged from 3 to biiginL. ... 

Table 9.4 Analytical procedures for the determination of alkyl phosphates in biological samples... 

In addition to the determination of the unmetabolized compounds to confirm exposure, the quantification of their metabolites, e.g. alkyl phosphate metabohtes or other characteristic metabolites, is a possibility. The most commonly used analytical methods for the... 

Bradway DE, Shafik TM. Malathion exposure studies. Determination of mono- and dicarboxyhc acids and alkyl phosphates in urine. J Agric Food Chem 1977 25 1342-4. 

Shafik MT, Bradway D, Enos HF. A cleanup procedure for the determination of low levels of alkyl phosphates, thiophosphates, and dithiophosphates in rat and human urine. J Agric Food Chem 1971 19 885-9. 

Both, alkyl phosphates and alkyl ether phosphates are made by treating the fatty alcohol or alcohol ethoxylates with a phosphorylating agent, usually phosphorous pentoxide, P4OJQ. The reaction yields a mixture of monoesters and diesters of phosphoric acid, with the ratio of the two esters being determined by the ratio of the reactants and the amount of water present in the reaction mixture. The physico-chemical properties of the alkyl phosphate surfactants depend on the ratio of the esters. Phosphate surfactants are used in the metal-working industry, due to their anticorrosive properties. 

Ionized calcium and total calcium measurements are both performed with PVC-type electrodes. Membranes based on lipophilic alkyl phosphates with phosphonate plasticizers have only marginal selectivity over magnesium but have been used in the past to determine ionized calcium (i.e., free calcium) in undiluted blood samples (M8). Interference from protons at low pHs prevents such membranes from being employed for total calcium determinations on samples diluted with acid. Use of ionophore ETH 1001 (see Fig. 2) overcomes any concerns about selectivity, whether from magnesium or pH, and is now the neutral carrier system most often utilized within analyzers to detect ionized or total calcium. 

St. John, L. E.. and Lisk. D. J. (1968). Rsipid and sensitive determination of otganophosphorous insecticides by alkali thennionic gas chromatography of their alkyl phosphate hydrolytic products. 7 Agr/r. F(md Chem. 16,408-410. 

The detection of pesticide metabolites in the urine of workers indicates prior exposure. However, it is difficult to relate this level of urinary metabolite to the actual worker exposure, and it is equally difficult to Interpret the toxicological significance of the level. A preliminary study conducted in rats exposed dermally to 100, 200 and 400 ug of azinphos-methyl showed a significant linear correlation between the dermal dosage and the urinary alkyl phosphate metabolite levels (19). Further studies are being conducted in other species to determine whether a similar type of relationship occurs and to develop a standard curve in which urinary metabolite levels could be utilized to estimate the amount of dermal exposure. 

Alkyl phthalate Alkyl adipates Alkyl azealates Alkyl citrates Alkyl sebacates Alkyl glycollates Alkyl phosphates Tetrahydrofuran extraction, GLC (inclndes determination of alcohol degradation products) [32]... 

Bradway, D. E., and Shafik, T. M. Malathion Exposure Studies. Determination of Mono- and Dicarboxylic Acids and Alkyl Phosphates in Urine... 

Determination of Mono- and Di-carboxylic Acids and Alkyl Phosphates in Urine... 

Human Exposure to Organophosphorus Pesticides. Modified Procedure for the Gas Chromatographic Determination of Alkyl Phosphate Metabolites in Urine... 

Tlie organic medium may also contain plasticizers that act to lower the glass transition temperature of the binder polymer. Such plasticizers help to assure good lamination to ceramic substrates and enhance the developability of xmexposed areas of the composition. The use of such materials should be minimized to reduce the amount of organic materials, which must be removed when the composition is fired. The choice of plasticizers is, of course, determined primarily by the polymer that must be modified. Among the plasticizers that have been used in various binder systems are diethyl phthalate, dibutyl phthalate, alkyl phosphates, polyalkylene glycols, hydroxy ethylated alkyl phenol, triethyleneglycol diacetate, and polyester plasticizers. Dibutyl phthalate is frequently used in acrylic polymer systems because it can be used effectively in relatively small concentrations. 

The substituents on the phosphorus in these polymers have significant effects upon the chemical shifts of the P resonance of the polymers. The P resonances of the chlorophosphate polymers are observed 4 ppm upfield of those of the coresponding phosphonite polymers. Those of the alkyl phosphate polymers are observed 9 ppm downfield of those of the corresponding phosphonate polymers and those of the aminophosphate polymers are observed 2 ppm upfield of those of the corresponding phos-phonate polymers. The fact that the chemical shifts of the resonances are relatively independent of the nature of the alkylene group means that the chemical shifts of the Ip uMR resonances can be used to accurately determine the type of substituent that is bonded to the phosphorus in these polymers. 

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