Phosphorus extraction procedure

Methyl parathion was determined in dog and human serum using a benzene extraction procedure followed by GC/FID detection (Braeckman et al. 1980, 1983 DePotter et al. 1978). An alkali flame FID (nitrogen-phosphorus) detector increased the specificity of FID for the organophosphorus pesticides. The detection limit was in the low ppb (pg/L). In a comparison of rat blood and brain tissue samples analyzed by both GC/FPD and GC/FID, Gabica et al. (1971) found that GC/FPD provided better specificity. The minimum detectable level for both techniques was 3.0 ppb, but GC/FPD was more selective. The EPA-recommended method for analysis of low levels (<0.1 ppm) of methyl parathion in tissue, blood, and urine is GC/FPD for phosphorus (EPA 1980d). Methyl parathion is not thermally stable above 120 °C (Keith and Walters 1985). 

Scheckel, K. G., Impellittteri, C. A., Ryan, J. A. McEvoy, T. 2003. Assessment of a sequential extraction procedure for perturbed lead-contaminated samples with and without phosphorus amendments. Environmental Science Technology, 37, 1892-1898. 

Extraction procedures have also been developed for the determination of the anionic species in soils of elements such as sulfur which are important as binding sites for metals as well as for its own mobility and availability (Cordos et al., 1995). The important biosignificant element selenium has similarly received attention (Blaylock and James 1993 Seby et al., 1997) and procedures for the speciation of phosphorus have been developed (Vaz et al., 1992 Chapman et al., 1997). 

Phosphorus extracted from sediment by NaOH has been related to non-occluded, surface-exchangeable, bioavailable forms (22). Hydrochloric acid extraction yields occluded phosphorus incorporated in hydrous metal oxides, carbonate and phosphate minerals of sediment. Hydroxylamine reagent specifically removes hydrous manganese oxides, while amorphous hydrous oxides of iron and aluminijm are removed by the oxalate reagent. Total available sediment phosphorus analyses includes sediment organic phosphorus components in addition to the inorganic portion determined by the selective extraction procedures. 

Dissolved metals other than calcium have a minor effect on the distribution of phosphorus between the water column and sediment in this fluvial system. The two principal metals of potential interest, iron and aluminum, are present in Genesee River water almost entirely in the particulate phase ( ). Dissolved concentrations of these metals are below the detection limit (less than 50 ug/1). Iron and aluminum minimum detectable dissolved concentrations were used to estimate the saturation levels of the corresponding phosphate minerals. These calculations suggest that both iron and aluminum phosphate minerals are substantially below saturation levels. The solid surfaces exhibited by iron and aluminum hydrous oxides (as particulate material in the water column) undoubtedly serve as sites for phosphorus adsorption and incorporation in the fluvial system. Data presented for the oxalate extraction procedure in Table III demonstrate the importance of phosphorus binding by hydrous metal oxides. 

In the lower reaches of the Genesee River, the results of the extractions suggest that substances other than hydrous oxides are phosphorus sinks. This is evident where the amount of sediment phosphorus extracted by hydrochloric acid steadily increases down river, while the oxalate extractable phosphorus remains relatively constant. Schwertmann (2 ) emphasized that the results of such procedures are best considered as a measure of the relative amount of a phase or, more generally, a measure of an element s reactivity in a sediment under carefully controlled conditions. Laboratory experiments (Figure 8) show that phosphorus uptake by calcium carbonate, under simulated natural conditions, proceeds slowly. The large hydrochloric acid extractable component observed at Rochester may arise from slow uptake and subsequent mineralization of dissolved inorganic phosphorus by carbonate minerals. 

Several chemical reactions, including calcium carbonate and hydroxyapatite precipitation, have been studied to determine their relationship to observed water column and sediment phosphorus contents in hard water regions of New York State. Three separate techniques have been used to Identify reactions important in the distribution of phosphorus between the water column and sediments 1) sediment sample analysis employing a variety of selective extraction procedures 2) chemical equilibrium calculations to determine ion activity products for mineral phases involved in phosphorus transport and 3) seeded calcium carbonate crystallization measurements in the presence and absence of phosphate ion. 

The dry-ashing plus acid digestion of tea leaves (Section 1.1) and the available phosphorus extraction (Section 1.3) are contrasting procedures in regard to the acceptable precision of the determination. In one the sample is weighed to 0.1 mg ( 0.02%), whereas in the other the 5 cm3 scoop used for measuring soil, may introduce a variation of 0.2 g ( 4%). You may like to think about this. Is the sample measuring procedure appropriate for the purpose of the analysis in each case ... 

Ruban, V., Ldpez-Sanchez, J. F., Pardo, P., Rauret, G., Muntau, H., and Quevauviller, Ph. (1999). Selection and evaluation of sequential extraction procedures for the determination of phosphorus forms in lake sediment. J. Environ. Monit. 1, 51-56. 

Sequential extraction or chemical fractionation techniques have been widely used in the characterization of various phosphorus fractions in soils and sediments, with an emphasis on the more bioavailable or plant-available inorganic forms (Condron et al., 2005). Early extraction procedures (Chang and Jackson, 1957 Williams et al., 1976b) focused on inorganic phosphorus associated with iron, aluminium and calcium, using various acid, base or salt extraction steps. Organic phosphorus was considered to be the residual or refractory phosphorus-containing fraction that remained after all other extractions had been performed. 

Solid phase extraction procedures are now commonplace as a means of sample cleanup and preconcentration in chromatography. Espinosa et al. (1999) used strong anion exchange (SAX) solid phase cartridges to concentrate and isolate phosphorus-... 

Solution NMR uses extracts of soils and environmental samples. As with any extraction procedure for soil organic phosphorus, there is always the risk of hydrolysis (Turner et aL, 2003b). There is little agreement on the most suitable extractant, but those in use include sodium hydroxide (Newman and Tate, 1980 Hawkes et aL, 1984), Bu NOH (Emsley and Niazi, 1983), the cation exchange resin Chelex in water (Adams and Byrne, 1989 Condron et aL, 1996), sodium hydroxide plus Chelex (Gressel et aL, 1996), sodium hydroxide plus sodium fluoride (Sumann et aL, 1998), and sodium hydroxide plus EDTA (Cade-... 

Bowman, R.A. (1989) A sequential extraction procedure with concentrated sulfuric acid and dilute base for soil organic phosphorus. Soil Science Society of America Journal 53, 352-366. 

Some elements may require special extraction procedures, e.g.. Phosphorus (Pardo et al., 1999) Sulphur (Fiedler et al., 1999) Arsenic(Yehl Tyson, 1997) SOica (Ragueneau Treguer, 1994) Mercury (QuevauviUo-et al., 1996). 

However, extraction of organic phosphorus from sediments and soils should be carried out in a manner that, as far as possible, avoids hydrolysis or oxidation to orthophosphate, and this is often incompatible with the procedures used for inorganic phosphorus extraction. Some authors have suggested that strongly acidic and basic conditions are intrinsically unsuitable for extraction because of the likely hydrolytic breakdown that they cause, and have suggested instead that chelating extractants such as NTA or ethylenediamine tetraacetic acid (EDTA) at near-neutral pH should be used as an alternative (Table 2). 

The quality characteristics of the oil produced by the enzyme-assisted aqueous extraction process is comparable to that of conventional extraction procedures except in its phosphorus content (Table 12.5). The enzymatic process yields oil with less phosphorus which requires no or limited degumming. The crude oil from this process can be physically refined without further treatment (Laiho et al., 1991). Despite this improved quality of the crude oil which is an apparent cost saving in subsequent downstream processing, the enzymatic process has not been commercially exploited due to problems with yields. Considerable degree of emulsification occurs during the process. Approximately 18-25% of the available oil in the seed remains unrecovered in a standard operation. The discovery that the versatile protein, oleosin, binds approximately 20% of the oil in oil-bearing seeds (Tzen et al., 1990) has implicated this protein in the low yields associated with this process. Thus, the recoveries could be improved by the use of proteases. It has, however, been observed that successful application of proteases to improve oil recovery produces excessively bitter meals, repressing the potential utilization of the meal as feed or food. 

Entenman and Chaikoff (28) could find little difference between the choline contents of alcohol-ether extracts of plasma when choline reineck-ate was precipitated from solutions at pH 7-8 or from strongly acid solutions (29)—indicating the absence of other nitrogenous compounds that form insoluble reineckates. A difference was observed, however, when the choline content of liver phospholipids was analyzed by the two methods. Taurog, Entenman, and Chaikoff (88) also compared the choline phosphorus ratio of human plasma purified by the colloidal-iron procedure of Folch and Van Slyke (33) with the ratio obtained by their direct extraction procedure. The choline rpho horus ratio by direct extraction was 0.98, and when purified with colloidal iron was 0.96. 

Several modifications of procedures based on halophosphonium ion have been developed. Triphenylphosphine and imidazole in combination with iodine or bromine gives good conversion of alcohols to iodides or bromides.22 An even more reactive system consists of chlorodiphenylphosphine, imidazole, and the halogen,23 and has the further advantage that the resulting phosphorus by-product diphenylphosphinic acid, can be extracted with base during product workup. 

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