Quantitative Phosphate Determinations

Ln(II) in LnFj Ln(II) were determined after samples dissolution in H PO in the presence of a titrated solution of NFI VO, which excess was titrated with the Fe(II) salt. It was found that dissolution of the materials based on CeF CeFj in H PO does not change the oxidation state of cerium, thus phosphate complexes of Ce(III, IV) can be used for quantitative spectrophotometric determination of cerium valence forms. The contents of Ln(II, III) in Ln S LnS may be counted from results of the determination of total sulfur (determined gravimetric ally in BaSO form) and sum of the reducers - S and Ln(II) (determined by iodometric method). 

Suitable conditions for the quantitative polarographic determination of technetium as pertechnetate are given by Miller et al. who propose a 0.1 M KCl solution of pH 10 or a phosphate buffer solution of pH 7. Since in pH 7 buffer the current is directly proportional to the concentration of technetium over the range of 0.1 to 1.1 ppm, this medium has been used for the determination of low concentrations of technetium in solutions of fission products by the standard addition technique. The half-wave potential of the used wave is —0.68 V vs. SCE. The reaction appears to be irreversible (Fig. 13). It has been found that neither rhenium, ruthenium nor other fission products interfere. However, tetraphenyl-arsonium chloride is reduced at a more positive potential than is pertechnetate therefore, (QH5) AsCl, if present, must be separated. 

For quantitative determination the corresponding spots and a blank area of same size are cut out. The cellulose is burned with concentrated nitric acid and the residue is used for phosphate determination according to Protocol 1.3.2, enzymatically by coupled optical test and in the case of P-labeling by counting radioactivity. 

The standard addition method is used for quantitation. After determination of the phosphates with P NMR (Figure 3-48) a calibration of the F NMR spectrum is not necessary. The amount of monofluorophosphate is known from the P NMR analysis. The fluoride content is determined from the integral areas of the fluoride and the monofluorophosphate signals in the F NMR spectrum. Differences in the response of both nuclei are determined by measurement of standardized solutions. 

Hawkins, R. A., and Miller, A. L., 1978, Loss of radioactive 2-deoxy-t/-glucose-6-phosphate from brains of conscious rats implications for quantitative autoradiographic determination of regional glucose utilization. Neuroscience 3 251-258. 

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. 

In the former, it gives precipitates with halides (except the fluoride), cyanides, thiocyanates, chromates(VI), phosphate(V), and most ions of organic acids. The silver salts of organic acids are obtained as white precipitates on adding silver nitrate to a neutral solution of the acid. These silver salts on ignition leave silver. When this reaction is carried out quantitatively, it provides a means of determining the basicity of the acid... 

A final requirement for a chemical kinetic method of analysis is that it must be possible to monitor the reaction s progress by following the change in concentration for one of the reactants or products as a function of time. Which species is used is not important thus, in a quantitative analysis the rate can be measured by monitoring the analyte, a reagent reacting with the analyte, or a product. For example, the concentration of phosphate can be determined by monitoring its reaction with Mo(VI) to form 12-molybdophosphoric acid (12-MPA). 

Sodium trimetaphosphate was used as an eluting agent for the removal of heavy metals such as Pb, Cd, Co, Cu, Fe, Ni, Zn and Cr from aqueous solutions. Distribution coefficients of these elements have been determined regarding five different concentrations of sodium trimeta phosphate (3T0 M 5T0 M 0.01 M 0.05 M 0.1 M) on this resin. By considering these distribution coefficients, the separation of heavy metals has been performed using a concentration gradient of 3T0 - 5T0 M sodium trimetaphosphate. Qualitative and quantitative determinations were realized by ICP-AES. 

Determination of uranium with cupferron Discussion. Cupferron does not react with uranium(VI), but uranium(IV) is quantitatively precipitated. These facts are utilised in the separation of iron, vanadium, titanium, and zirconium from uranium(VI). After precipitation of these elements in acid solution with cupferron, the uranium in the filtrate is reduced to uranium(IV) by means of a Jones reductor and then precipitated with cupferron (thus separating it from aluminium, chromium, manganese, zinc, and phosphate). Ignition of the uranium(IV) cupferron complex affords U308. 

The analysis of phosphates and phosphonates is a considerably complex task due to the great variety of possible molecular structures. Phosphorus-containing anionics are nearly always available as mixtures dependent on the kind of synthesis carried out. For analytical separation the total amount of phosphorus in the molecule has to be ascertained. Thus, the organic and inorganic phosphorus is transformed to orthophosphoric acid by oxidation. The fusion of the substance is performed by the addition of 2 ml of concentrated sulfuric acid to — 100 mg of the substance. The black residue is then oxidized by a mixture of nitric acid and perchloric acid. The resulting orthophosphate can be determined at 8000 K by atom emission spectroscopy. The thermally excited phosphorus atoms emit a characteristic line at a wavelength of 178.23 nm. The extensity of the radiation is used for quantitative determination of the phosphorus content. 

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. 

Unfortunately, in most of the previous examples, the extent of the asymmetry-induction was determined by chiroptical measurements (ORD, CD) that gave qualitative and not quantitative information. The NMR chiral shift efficiency of TRISPHAT 8 and other hexacoordinated phosphate anions was therefore considered as an excellent analytical tool to provide accurate measurement of the induced selectivity by NMR spectroscopy. 

Many dehydrogenase enzymes catalyze oxidation/reduction reactions with the aid of nicotinamide cofactors. The electrochemical oxidation of nicotinamide adeniiw dinucleotide, NADH, has been studied in depthThe direct oxidation of NADH has been used to determine concentration of ethanol i s-isv, i62) lactate 157,160,162,163) pyTuvate 1 ), glucose-6-phosphate lactate dehydrogenase 159,161) alanine The direct oxidation often entails such complications as electrode surface pretreatment, interferences due to electrode operation at very positive potentials, and electrode fouling due to adsorption. Subsequent reaction of the NADH with peroxidase allows quantitation via the well established Clark electrode. 

Kellum [115] has described a class-selective oxidation chemistry procedure for the quantitative determination of secondary antioxidants in extracts of PE and PP with great precision (better than 1 %). Diorgano sulfides and tertiary phosphites can be quantitatively oxidised with /-chloropcroxybenzoic acid to the corresponding sulfones and phosphates with no interference from other stabilisers or additives. Hindered phenols, benzophenones, triazoles, fatty acid amides, and stearate... 

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. 

Concentration and MWD of F-PHEA After Absorption. F-PHEA was determined in perfusate samples by quantitative GPC relative to a freshly prepared F-PHEA standard run on the same day. Either a mixed-bed column (12 x 300 mm Sephacryl S-200 Sephadex G-25 SF 3 1, Pharmacia LKB) or a Separon HEMA-Bio 40 column (8 x 250 mm 10 pm particle size, Tessek A/S, Aarhus, Denmark) was used with a 20 pL injection volume. A mobile phase of pH 7.4 phosphate buffered saline (0.05 M phosphate, 0.15 M NaCl) was supplied (Model LC-7A Bio Liquid Chromatograph, Shimadzu Corporation, Kyoto, Japan) at 0.5 or 1 mL/min. Fluorescent detection was employed (Model RF-535 Fluorescence HPLC Monitor,... 

Russell and Rabenstein [43] described a speciation and quantitation method for underivatized and derivatized penicillamine, and its disulfide, by capillary electrophoresis. Penicillamine and penicillamine disulfide were determined by capillary electrophoresis on a capillary (24 cm x 25 pm i.d. or 50 cm x 50 pm i.d. for underivatized thiols) with detection at 357 nm (200 nm for underivatized thiols). The run buffer solution was 0.1 M phosphate (pH 2.3). Detection limits were 20-90 pM without derivatization, and 5-50 pM after derivatization. Calibration graphs were linear from 1 pM to 5 mM thiols. 

Rao et al. [45] determined primaquine phosphate, in pharmaceutical dosage forms, by using a colorimetric method. Powdered tablets containing the equivalent of 100 mg of primaquine phosphate were heated with 25 mL of water for 10 min, the solution was cooled and filtered, and 10 mL portion of the filtrate was diluted 10-fold with water. A 5-mL portion of this solution was mixed with 5 mL of pH 5 buffer solution, 1 mL of 0.08%. amidopyrine solution in aqueous 95% alcohol and 2 mL of aqueous 0.1% sodium periodate. After 10 min, 0.5 mL of aqueous sodium metabisulfite solution was added and the absorbance was measured at 580 nm. Beer s law was obeyed between 4 and 43 pg/mL of primaquine phosphate. Recoveries were quantitative. 

Valproic acid has been determined in human serum using capillary electrophoresis and indirect laser induced fluorescence detection [26], The extract is injected at 75 mbar for 0.05 min onto a capillary column (74.4 cm x 50 pm i.d., effective length 56.2 cm). The optimized buffer 2.5 mM borate/phosphate of pH 8.4 with 6 pL fluorescein to generate the background signal. Separation was carried out at 30 kV and indirect fluorescence detection was achieved at 488/529 nm. A linear calibration was found in the range 4.5 144 pg/mL (0 = 0.9947) and detection and quantitation limits were 0.9 and 3.0 pg/mL. Polonski et al. [27] described a capillary isotache-phoresis method for sodium valproate in blood. The sample was injected into a column of an EKI 02 instrument for separation. The instrument incorporated a conductimetric detector. The mobile phase was 0.01 M histidine containing 0.1% methylhydroxycellulose at pH 5.5. The detection limit was 2 pg/mL. 

Competitive immunoassays may also be used to determine small chemical substances [10, 11]. An electrochemical immunosensor based on a competitive immunoassay for the small molecule estradiol has recently been reported [11]. A schematic diagram of this immunoassay is depicted in Fig. 5.3. In this system, anti-mouse IgG was physisorbed onto the surface of an SPCE. This was used to bind monoclonal mouse anti-estradiol antibody. The antibody coated SPCE was then exposed to a standard solution of estradiol (E2), followed by a solution of AP-labeled estradiol (AP-E2). The E2 and AP-E2 competed for a limited number of antigen binding sites of the immobilized anti-estradiol antibody. Quantitative analysis was based on differential pulse voltammetry of 1-naphthol, which is produced from the enzymatic hydrolysis of the enzyme substrate 1-naphthyl phosphate by AP-E2. The analytical range of this sensor was between 25 and 500pg ml. 1 of E2. 

Holzbecker and Ryan [825] determined these elements in seawater by neutron activation analysis after coprecipitation with lead phosphate. Lead phosphate gives no intense activities on irradiation, so it is a suitable matrix for trace metal determinations by neutron activation analysis. Precipitation of lead phosphate also brings down quantitatively the insoluble phosphates of silver (I), cadmium (II), chromium (III), copper (II), manganese (II), thorium (IV), uranium (VI), and zirconium (IV). Detection limits for each of these are given, and thorium and uranium determinations are described in detail. Gamma activity from 204Pb makes a useful internal standard to correct for geometry differences between samples, which for the lowest detection limits are counted close to the detector. 

Because the preceding chromogenic assay rely on choline quantitation, the hydrolysis of substrates with headgroups other than choline cannot be followed. To circumvent this problem, another useful protocol was devised whereby the phosphorylated headgroup produced by the PLCBc hydrolysis is treated with APase, and the inorganic phosphate (Pi) that is thus generated is quantitated by the formation of a blue complex with ammonium molybdate/ascorbic acid 5 nmol of phosphate may be easily detected. This assay, which may also be performed in a 96-well format, has been utilized to determine the kinetic parameters for the hydrolysis of a number of substrates by PLCBc [37,38]. 

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