Determination of extractable phosphorus

Brah and Bishnoi [74] have studied the effect of temperature and soil phosphorus status on the determination of extractable phosphorus by Olsen s method [71]. 

Tecator Ltd., Sweden. (1984) Application Note AN 73/84. Determination of Extractable Phosphorus in Soil by Flow Inspection Analysis. 

Methods based on flow-injection analyses have been described for the determination of extractable [62, 64-66] and available [67] phosphorus in soils. 

Phosphorus was determined in the extracts by the spectrophotometric method of Murphy and Riley [63] and Stickland and Parsons [96]. In Table 12.10 results are shown obtained upon applying the procedure to the determination of total phosphorus in solutions of calcium phosphoglyceric acid. 

J. Buanuama, M. Miro, E.H. Hansen, J. Shiowatana, On-line dynamic fractionation and automatic determination of inorganic phosphorus in environmental solid substrates exploiting sequential injection microcolumn extraction and flow injection analysis, Anal. Chim. Acta 570 (2006) 224. 

Non-specific Determination of Organic Phosphorus in Waters and Extracts... 

Another example is a fully computerized MSFIA system for the spectrophotometric determination of available phosphorus in soil extracts. The molybdenum blue method is chosen for the colorimetric determination, using ascorbic acid as reducing agent, antimony to accelerate the reduction to the blue complex and applying the Egner-Riehm method to extract phosphorus from soil samples. It presents a hnear calibration curve between 0.75 and 15 mg/1. A determination frequency of 15/h may be achieved, with good repeatability for 12 consecutive injections of soil extracts (RSD <1.7%). Results obtained from 12 soil samples were statistically comparable to those attained by the usual batch method [102]. 

Enhanced sensitivity in the determination of reactive phosphorus in seawater has been achieved by extracting PMB from volumes of up to 1000 L onto a synthetic acrylic cation exchange medium (Acrilan) using a 2 L volume of the resin fibers. Filterable unreactive phosphorus was adsorbed to Fe(III) hydroxide coated acryhc fibers in a similar manner [168]. While the extraction efficiency of this technique was >95%, it appears not to have been exploited to gain maximum sensitivity. 

Total phospholipids are quantitated by determination of the phosphorus content of lipid extracts from which non-lipid phosphorus has been removed by purification procedures. For this purpose chloroform-methanol extracts subjected to diffusion purification (Folch et al. 1951, Sperry 1955) are suitable. Lipid phosphorus is determined in aliquots of these extracts after digestion. Most procedures for determination of phosphorus are based on the method of Fiske and Subbarow (1925) which utilizes conversion of phosphate to phosphomolybdate and its subsequent reduction to molybdic blue. Modifications of this method were reviewed by Lindberg andERNSTER (1956). Avery convenient phosphorus assay was described by Bartlett (1959). Total phospholipids are calculated by multiplication of the lipid phosphorus values with 25. These values are only approximations since phosphorus does not represent exactly 4% of each phospholipid molecule. 

De la Torre, R. et al. 1998. Quantitative determination of tricyclic antidepressnts and their metabolites in plasma by solid phase extraction (bond-elut TCA) and separation by capillary gas chromatography with nitrogen-phosphorus detection. Ther Drug Monit. 20 340. 

Smirnova et al. [5] have described a simple non-enzymatic method of quantitative determination of adenosine triphosphate in activated sludge from aeration tanks. Extraction of the nucleotides in boiling distilled water was followed by removal of the protein impurities by acidification. Barium salts of di- and triphosphates of the nucleotides were precipitated and the precipitate was washed and dissolved in acid to convert the barium salts to sodium salts. The quantity of adenosine triphosphate was determined quantitatively by inorganic phosphorus in the liquid over the precipitate before and after acid hydrolysis, and by ultraviolet absorption spectra. The method was tested in activated sludge from operational sewage works. There was good agreement between the adenosine triphosphate content determined spectrophotometrically and by phosphorus, despite the presence of small quantities of secondary impurities. 

Aspila et al. [60] have described a semi-automated method for the determination of inorganic, organic and total phosphorus in river and lake sediments. Total phosphorus is extracted from sediments with 1M hydrochloric acid after ignition at a high temperature (550°C) (method 1) or by digestion with sulphuric acid-potassium persulphate at 135°C in a sealed PTFE-lined Parr bomb (method 2). 

Olsen et al. [62] have described a method for the determination of pH8.5 sodium bicarbonate extractable phosphorus in soils. The concentration of the blue complex produced by the reduction, with ascorbic acid, of the phosphomolybdate formed when acid ammonium molybdate reacts with phosphate is measured spectrophotometrically at 880 nm [63]. 

In the method for extractable phosphorus [62, 64-66] the phosphorus is extracted from the soil at 20 1°C with sodium bicarbonate solution at pH8.5. After filtration and release of carbon dioxide the extracts are introduced into a flow-injection system for the determination of phosphate. Phosphate is determined by reaction with vanadomolybdate and the yellow colour evaluated at 410nm. Between 20 and lOOOmg kg-1 phosphorus in soil has been determined using this method. 

In a further method [67] for the determination of ammonium lactate extractable (i.e. available) phosphorus in soils, the sample 5g is extracted with 100ml acidic ammonium lactate and then phosphate determined by flow-injection analysis using the stannous chloride method [68]. 

Addison and Ackman [69] have described a direct determination of elementary yellow phosphorus in mud in which the phosphorus is extracted with benzene or isooctane. Gas chromatographic separation is achieved on a 2mx3mm column packed with 3% OV-1 or SE-30 on Chromosorb W maintained at 100 or 120°C respectively. The carrier gas was helium (80ml m 1). A flame photometric detector with a 526nm filter at 200°C was employed. Down to lpg of phosphorus could be determined. 

Dobolyi and Bidlo [76] have described methods for the determination of phosphorus in lake sediments. Shulka et al. [75] investigated the interference by arsenic in the perchloric acid digestion procedure of Murphy and Riley [85] for the determination of phosphorus in sediments. Arsenite concentrations up to 20pg did not interfere but arsenate interfered. Between 1 and 45 pg arsenic g"1 was extracted from a lake sediment and in all cases the error in the determination of phosphorus due to the presence of arsenic was less than 1%. 

For the determination of nitrogen- and phosphorus-containing pesticides in water by extraction with dichloromethane and detection by GC-NPD... 

Ghen X-H, Franke J-P, Wijsbeek J, de Zeeuw RA. 1994. Determination of basic drugs extracted from biological matrices by means of solid-phase extraction and wide-bore capillary gas chromatography with nitrogen-phosphorus detection. 

Martinez MA, Sanchez de la Torre C, Almarza E. 2002. Simultaneous determination of viloxazine, venlafaxine, imipra-mine, desipramine, sertraline, and amoxapine in whole blood comparison of two extraction/cleanup procedures for capillary gas chromatography with nitrogen-phosphorus detection. J Anal Toxicol 26 296. 

The second reason for acid-digestion is the determination of the total soil elemental content of, e.g. potassium, phosphorus or trace elements. This is seldom done for potassium in normal soil samples, mainly because the total K in soils is of no value as an index to the availability of K to plants, nor is it always of value in tracing the movement or accumulation of applied fertilizer K (Pratt, 1965). The unreactive soil phosphorus is obtained by subtracting the naturally leached reactive phosphorus from the total phosphorus, and a method for determining the latter by extraction with sulphuric acid and potassium persulphate is cited by Turner and FHaygarth (2000). They analysed... 

Fig. 5.3. Manifold for the automated determination of phosphorus in soil extracts.

Procedure. Carry out the extraction and then determine phosphorus as in Method 5.9a, except that working standard solutions should be made up in the Mehlich 1 extractant. Determine potassium and magnesium as in Method 5.10, except that standards are made up in Mehlich 1 extractant. Determine calcium as in Method 5.2, except that standards are made up in Mehlich 1 extractant. The composition of composts is so variable that appropriate dilutions of extracts may be required, and calculations adjusted accordingly. 

Method 6.2a. Determination of water-soiubie phosphorus (extraction)... 

Procedure (extraction). Transfer 2.5 g air-dry soil, 2 mm mesh size, into a 250 ml polypropylene screw-cap centrifuge bottle/tube and add 100 ml acetic acid - 8-hydroxyquinoline reagent. Cap the tube and shake overnight (17 h) on a reciprocating shaker, at approximately 275 strokes of 25 mm length per minute at a constant temperature (20°C). Centrifuge for 15 min at 2800 rpm and remove an aliquot for the determination of acid extractable inorganic phosphorus (a). 

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