Phosphorus spectrophotometric determination

A reaction of mixed molybdenum polyoxometalates (POMs) with cyanine dye has been used for highly selective and sensitive spectrophotometric determination of phosphorus(V) and arsenic(V). Color of the solution is considerably changed by reaction of Keggin POMs with styrene cyanine dyes. Derivatives of l,3,3-threemethyl-3//-indol - astrazone violet (AV 3R), astrazone rose, astrazone yellow, astrazone red were investigated. 

Phosphorus and Silicon in Waters, Effluents and Sludges [e.g. Phosphorus in Waters, Effluents and Sludges by Spectrophotometry-phosphomolybdenum blue method. Phosphorus in Waters and Acidic Digests by Spectrophotometry-phosphovanadomolybdate method. Ion Chromatographic Methods for the Determination of Phosphorus Compound, Pretreatment Methods for Phosphorus Determinations, Determination of silicon by Spectrophotometric Determination of Molybdate Reactive Silicon-1 -amino-2-naphthol-4, sulphonic acid (ANSA) or Metol reduction methods or ascorbic acid reduction method. Pretreatment Methods to Convert Other Eorms of Silicon to Soluble Molybdate Reactive Silicon, Determination of Phosphorus and Silicon Emission Spectrophotometry], 1992... 

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. 

Simmons, W. R. and Robertson, J. H. (1950). Spectrophotometric determination of phosphorus in organic phosphates. Analyt. Chem. 22, 1177. 

R. M. Pollman, Atomic absorption spectrophotometric determination of calcium and magnesium and colorimetric determination of phosphorus in cheese collaborative study, J. Assoc. Off. Anal. Chem., 74 (1991), 27 -31. 

If higher sensitivities are desired then the ammonium phosphomolybdate product may be reduced with stannous chloride or ascorbic acid in order to give soluble molybdenum blue [24]. Spectrophotometric determination of the blue absorbance at 885 nm gives a detection limit of 0.003 mg/L phosphate, stated as phosphorus (3 ppb in freshwater) or 0.0092 mg/L as expressed phosphate [24]. 

The total content of the elemental phosphorus in soils can be extracted and determined by perchloric acid digestion followed by spectrophotometric determination. 

Treated wood was divided into 5 layers from the top to the bottom symmetrically. The contents of nitrogen and phosphorus of each layer were measured by Kelder s method and spectrophotometric determination. Thermogravimetric analysis (TG) and differential thermal analysis (DTA) were performed over the temperature range room temperature- 600 T in an air of lOOml/min., using a heating rate of 10 °C/min. 

C. Pasquini, W.A. Oliveira, Monosegmented system for continuous-flow analysis. Spectrophotometric determination of chromium(VI), ammonia, and phosphorus, Anal. Chem. 57 (1985) 2575. 

B.F. Reis, E.A.G. Zagatto, A.O. Jacintho, F.J. Krug, H. Bergamin-Filho, Merging zones in flow injection analysis. Part 4. Simultaneous spectrophotometric determination of total nitrogen and phosphorus in plant material, Anal. Chim. Acta 119 (1980) 305. 

For seawater analysis, it is possible to pump the sample directly from the sea to a shipboard analyser. The sample can then be de-gassed in-line and handled in a shipboard flow system. This possibility, and the main practical, physico-chemical and interpretative aspects, were discussed in relation to the in situ spectrophotometric determination of seawater pH [9]. The attractive features and applications of shipboard flow injection spectrophotometric determinations are discussed elsewhere [10,11]. A compact, shipboard flow analysis system incorporating a LTV photoreactor has also been reported for the determination of total phosphorus in estuarine and marine waters [12]. Another way to sample seawater is to use a towed torpedo-shaped "fish," deployed off the crane arm of a hydrographic winch at a distance of 5 m from the ship, connected to a deck mounted pump by appropriate tubing. Filtration can be incorporated in-line and the filtered sample collected or pumped directly to the flow analyser [13]. This approach (Fig. 8.1) minimises contamination and preconditions the sample, as demonstrated in the chemiluminometric determination of iron(II) in surface seawater. 

For simultaneous determinations and /or speciation, different separation/ concentration steps can be implemented in the same manifold, as in, e.g., the determination of nitrogen, phosphorus and potassium in fertilisers [314]. The sample was inserted and passed successively through a dialysis unit and a gas diffusion unit to a flow cell for the spectrophotometric determination of phosphate. The dialysed potassium ions and the diffused gaseous ammonia were collected in specific streams and determined by flame photometry and potentiometry, respectively. 

C.C. Oliveira, E.A.G. Zagatto, A.N. Araujo, J.L.F.C. Lima, Sample preparation in sequential injection analysis. Spectrophotometric determination of total phosphorus in food samples, Anal. Chim. Acta 371 (1998) 57. 

I.D. McKelvie, B.T. Hart, T.J. Cardwell, R.W. Cattrall, Spectrophotometric determination of dissolved organic phosphorus in natural waters using in-line photooxidation and flow injection, Analyst 114 (1989) 1459. 

S. Motomizu, M. Oshima, Spectrophotometric determination of phosphorus as orthophosphate based on solvent extraction of the ion associate of molybdophosphate with Malachite Green using flow-injection, Analyst 112 (1987) 295. 

Spectrophotometric determination as a molybdophosphate complex (phosphorus molybdenum blue)... 

The analysis of phosphorus in waters has historically been based on the photometric measurement of 12-phosphomolybdate or the phosphomolybdenum blue species, which are produced when phosphomolybdate is reduced. The majority of manual and automated methods of phosphate determination are based on the spectrophotometric determination of phosphorus as phosphomolybdenum blue, i.e.. 

Detection with iodine vapour before quantitative determination has been used frequently, e.g. analysis of lipid esters in conjunction with gas chromatographic determination [187] or with colorimetric determination after conversion to ferric hydroxamate complexes [731] to detect analgesic drugs [215] (cf.Fig. 79) and steroids [217, 437] with subsequent spectrophotometric determination in the visible or UV regions to detect phospholipids, where phosphorus determination followed [6, 79, 637]. 

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]. 

MPFS system for the spectrophotometric determination of dissolved orthophosphate and dissolved organic phosphorus in wastewater samples. MP solenoid micropump RC reaction coil. 

McKelvie, I.D. et al., Spectrophotometric determination of dissolved organic phosphorus in natural waters using in-line photo-oxidation and flow injection. Analyst 114, 1459, 1989. Aminot, A. and Kerouel, R., An automated photo-oxidation method for the determination of dissolved organic phosphorus in marine and fresh water. Marine Chemistry 76, 113, 2001. Solorzano, L. and Strickland, J.D., Polyphosphate in seawater. Limnology and Oceanography 13, 515,1968. 

Aoyagi, M., Yasumasa, Y., and Nishida, A., Rapid spectrophotometric determination of total phosphorus in industrial wastewaters by flow injection analysis including a capillary reactor, Analytica Chimica Acta 214, 229, 1988. 

Phosphorus from organophosphorus compounds, which are combusted to give mainly orthophosphate, can be absorbed by either sulphuric acid or nitric acid and readily determined spectrophotometrically either by the molybdenum blue method or as the phosphovanadomolybdate (Section 17.39). 

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. 

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