Spectrophotometric analysis phosphate

Description of Method. The FIA determination of phosphate is an adaptation of a standard spectrophotometric analysis for phosphate. In the presence of add, phosphate reacts with molybdate to form a yellow-colored complex in which molybdenum is present as Mo(VI). 

The simultaneous analysis of orthophosphate, glycerol phosphates, and inositol phosphates has been achieved by spectrophotometric analysis of the molybdovanadate complexes. Also, a sensitive and selective chemiluminescent molecular emission method for the estimation of phosphorus and sulphur is described, which is based on passing solutions into a cool, reducing, nitrogen-hydrogen diffusion flame. For organic compounds it was usually necessary to prepare test solutions by an oxygen-flask combustion technique. 

The analysis of disopyramide phosphate may be performed by UV spectrophotometric analysis employing 0.1 N sulfuric acid in absolute methanol as solvent. 

This study on the immobilization of glucose oxidase and the characterization of its activity has demonstrated that a bioactive interface material may be prepared from derivatized plasma polymerized films. UV/Visible spectrophotometric analysis indicated that washed GOx-PPNVP/PEUU (2.4 cm2) had activity approximately equivalent to that of 13.4 nM GOx in 50 mM sodium acetate with a specific activity of 32.0 U/mg at pH 5.1 and room temperature. A sandwich-type thin-layer electrochemical cell was also used to qualitatively demonstrate the activity of 13.4 nM glucose oxidase under the same conditions. A quantitatively low specific activity value of 4.34 U/mg was obtained for the same enzyme solution by monitoring the hydrogen peroxide oxidation current using cyclic voltammetry. Incorporation of GOx-PPNVP/PEUU into the thin-layer allowed for the detection of immobilized enzyme activity in 0.2 M sodium phosphate (pH 5.2) at room temperature. 

Appropriate control experiments were carried out, when both modified and unreacted collagen membrane was immersed in buffer solution (0.02M phosphate buffer, pH 7.0) and stored at 4°C for twenty four hours. Spectrophotometric analysis of the buffer media showed no absorbance from impurities and/or carrier protein at 280nm. Thus, the decrease in absorbance at 280 nm was a direct measure of the binding or sorption of enzyme to the collagen matrix. 

Direct spectrophotometry is not often used for the analysis of sulfIsoxazole because other sulfonamides tend to interfere. However, in the absence of any interferences, the max at 253 nm in pH 7.5 phosphate buffer may be used for direct spectrophotometric analysis. 

Chemists in Korea demonstrated a clever, rational approach to designing a reagent for the spectrophotometric analysis of phosphate. A ligand containing six N atoms and one O atom that could bind two ions was selected. The distance between ions is just right for the metal ion indicator pyrocatechol violet to bind, as shown at the left below. Pyrocatechol violet is blue when bound to metal and yellow when free. 

Absorption spectrophotometric analysis procedures have been developed for a number of environmental species. For water contaminants alone, these include procedures for the determination of arsenic, boron, bromide ion, cyanide, fluoride, nitrate, phenols, phosphate, selenium, sUica, sulfide, surfactants, and tannin and lignin. A typical such procedure is the spectrophotometric determination of phenol in water by the reaction with 4-aminoantipyrene... 

Oxidation of oligopeptides was followed in real time using spectrophotometric analysis. Oxidation was initiated by adding about 150 units of enzyme solution to a "blanked" cuvette containing 1 mL of substrate peptide (0.075 mM) dissolved in 0.1 M phosphate buffer, pH 7. Reaction mixtures were then scanned over the 190-600 nm range, and spectra were recorded at timed intervals. Air was bubbled through the reaction mixtures between scans or at 5 min intervals. 

Stabilisers are usually determined by a time-consuming extraction from the polymer, followed by an IR or UV spectrophotometric measurement on the extract. Most stabilisers are complex aromatic compounds which exhibit intense UV absorption and therefore should show luminescence in many cases. The fluorescence emission spectra of Irgafos 168 and its phosphate degradation product, recorded in hexane at an excitation wavelength of 270 nm, are not spectrally distinct. However, the fluorescence quantum yield of the phosphate greatly exceeds that of the phosphite and this difference may enable quantitation of the phosphate concentration [150]. The application of emission spectroscopy to additive analysis was illustrated for Nonox Cl (/V./V -di-/i-naphthyl-p-phcnylene-diamine) [149] with fluorescence ex/em peaks at 392/490 nm and phosphorescence ex/em at 382/516 nm. Parker and Barnes [151] have reported the use of fluorescence for the determination of V-phenyl-l-naphthylamine and N-phenyl-2-naphthylamine in extracted vulcanised rubber. While pine tar and other additives in the rubber seriously interfered with the absorption spectrophotometric method this was not the case with the fluoromet-ric method. 

Abou-Ouf et al. [16] described a spectrophotometric method for the determination of primaquine phosphate in pharmaceutical preparation. Two color reactions for the analysis of primaquine phosphate dosage form, which are based on 2,6-dichlor-oquinone chlorimide and l,2-naphthoquinone-4-sulfonate, were described. The reactions depend on the presence of active centers in the primaquine molecule. These are the hydrogen atoms at position 5 of the quinoline nucleus and the primary amino group of the side chain. The method was applied to tablets of primaquine phosphate and a combination of primaquine phosphate and amodiaquine hydrochloride. 

Early colorimetric methods for arsenic analysis used the reaction of arsine gas with either mercuric bromide captured on filter paper to produce a yellow-brown stain (Gutzeit method) or with silver diethyl dithiocarbamate (SDDC) to produce a red dye. The SDDC method is still widely used in developing countries. The molybdate blue spectrophotometric method that is widely used for phosphate determination can be used for As(V), but the correction for P interference is difficult. Methods based on atomic absorption spectrometry (AAS) linked to hydride generation (HG) or a graphite furnace (GF) have become widely used. Other sensitive and specihc arsenic detectors (e.g., AFS, ICP-MS, and ICP-AES) are becoming increasingly available. HG-AES, in particular, is now widely used for routine arsenic determinations because of its sensitivity, reliability, and relatively low capital cost. 

By use of releasing agents Considering the reaction M-X-i-R = R- Xh-M, it becomes evident that an excess of the releasing agent (R) will lead to an enhanced concentration of the required gaseous metal atoms (M) which will be of special significance if the product R-X is a stable compormd. Hence in the determination of calcium in presence of phosphate the addition of excess of strontium chloride to the test solution will lead to the formation of strontium phosphate and the calcium can then be determined in an acetylene-air flame without any interference due to phosphate. Also addition of EDTA to a calcium solution before analysis may increase the sensitivity of the subsequent flame spectrophotometric determination which may be due to the formation of an EDTA complex of calcium which is readily dissociated in the flame. 

This innovation generally involves modifications to the operation of the sampler and random access reagent selection, and can be implemented in both segmented and unsegmented flow analysers. For unsegmented flow analysis, the spectrophotometric determination of zinc and phosphate in soil extracts [368] is a good example. Zinc was determined only when phosphate was present at concentrations above a threshold level. The number of determinations required was reduced by 30%. Analogously, an expert flow system was proposed for the turbidimetric determination of chloride and sulphate in natural waters [369]. Both methods were implemented in the same manifold, and the need for sulphate determination was dependent on the chloride concentration determined. 

L. C. Davis and G. A. Radke, Chemically Coupled Spectrophotometric Assays Based on Flow Injection Analysis. Determination of Nitrogenase by Assays for Creatinine, Ammonia, Hydrazine, Phosphate and Dithionite. Anal. Biochem., 140 (1984) 434. 

Fluorometric and spectrophotometric studies of filipin-cholesterol interaction showed that the stoichiometry of the interaction was 1 1 [150] or 1 1.5 [146,147]. UV spectrophotometry changes have been used to monitor the stoichiometry of the interaction between filipin and free or liposome-bound cholesterol. Analysis of aqueous dispersions suggested that the stoichiometry was 1 1 [171]. Lecithin, dicetyl phosphate-cholesterol liposomes only produced maximal spectral changes of filipin when the sterol polyene ratio was 1 1 [172]. Filipin released trapped ion markers from sterol—phospholipid liposomes. The rate of release was dependent upon cholesterol content of the liposome membrane (maximum at sterol phospholipid ratio of 1 1) and upon the molar fllipin sterol ratio (maximum at fllipin sterol ratio of 1 1). 

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.. 

Thomsen, J., Johnson, K.S., and Petty, R.L., Determination of reactive silicate in seawater by flow injection analysis. Marine Science Institute of Analytical Chemistry (1983), 55(14), 2378-2382. Mas-Torres, F., Munoz, A., Estela, J.M., and Cerda, V., Simultaneous spectrophotometric determination of phosphate and silicate by a stopped-flow sequential injection method. International Journal of Environmental Analytical Chemistry (2000), 77(3), 185-202. 

It appears that new separation techniques have not yet been applied to biotin analysis, and only one example was found in the literature. Capillary zone electrophoresis separation of biotin and multivitamin mixtures was achieved on a 600 X 0.05 mm fused silica capillary under 30 kV using 20 mM phosphate buffer pH 8.0 as eluent (122). Although the separation was good, the sensitivity was limited by the spectrophotometric detection. 

The same FIA system is employed by Arruda and coworkers to determine MSG in food samples [21]. As a difference, the GIAD enzyme is obtained from pumpkin [Cucurbita maxima), and the enzymatic reactor is prepared in a completely different way. As the preparation of enzymatic reactors based on enzyme extracts is known to be a laborious procedure, the authors propose to prepare the reactor with a naturally immobilized enzyme. For this purpose, a polyethylene column is filled with 200 mg of square pieces of the outer layer of Cm. maxima. A piece of the fruit is first cut and rinsed with distilled water. Then the outer layer is cut in square pieces with 2-mm sides and 1-mm thick and washed with phosphate buffer solution. This column is incorporated into the FIA system. The obtained linear range with the optimized FIA system is 10-100 mmol L and the analytical frequency is 40 h h The method is applied to the analysis of real samples (meat softener, meat soup, and spices), and the results are compared with those obtained applying the conventional spectrophotometric method to the same samples. The implemented procedure has a comparable precision to the conventional method (deviation values lower than 5%). This enzymatic reactor can be used for 21 days (200 determinations) without significant changes. 

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