Molybdenum Blue Complex Research Articles

Specific H+ level is crucial for accurate phosphate quantification using ascorbate as a reductant.

Owing to its essentiality for cellular metabolism, phosphate (PO43-) plays a pivotal role in ecosystem dynamics. Frequent testing of phosphate levels is necessary to monitor ecosystem health. Present investigations were aimed to identify the key factors that are essential for proper quantification of PO43-. Primarily, H+ levels played a critical role in the development of molybdenum blue complex by ammonium molybdate and PO43- with ascorbic acid as a reductant. Molybdenum blue complex formed in the presence of 8 to 12mmol of H+ in 3ml reaction mixture remained stable even after 72h. Of different concentrations of ammonium molybdate and ascorbic acid tested, best molybdenum blue complex was formed when their concentrations were 24.3 and 5.68μmol, respectively. More or less similar intensity of molybdenum blue complex (due to reduction of phosphomolybdic acid and not molybdic acid) was formed in the presence of H+ at levels ranging from 8 to 10mmol in 3ml reaction mixture. Our findings unequivocally demonstrated that (i) the reaction mixture containing 3% ammonium molybdate, 0.1% ascorbic acid and 5M H2SO4 in the ratio of 1:1:1 is ideal for PO43- quantification; (ii) antimony (Sb) significantly curbs the formation of molybdenum blue under these ideal conditions; (iii) this fine-tuned protocol for PO43- quantification could be extended without any problem for determining the level of PO43- both in plant as well as soil samples; and (iv) Azotobacter possesses potential to enhance levels of total PO43- in leaves and grains and soluble/active PO43- in rhizosphere soils of wheat.

A SIMPLE SPECTROPHOTOMETRIC METHOD FOR THE QUANTITATIVE ANALYSIS OF PHOSPHATE IN THE WATER SAMPLES

A simple spectrophotometric method was used to determine the phosphate content in the water sampels. The method is based on the formation of molybdenum blue complex from the reaction of orthophosphate and ammonium molybdate followed by reduction with ascorbic acid in the aqueous sulfuric acid medium. The color intensity of the molybdenum blue complex is proportionally to the phosphate content in the solution. The system obeys Lamber-Beer’s Law at the 890 nm in the concentration range of 0.1-1 mg P/L and the linier calibration graph was obtained with the slope, 0.6334, intercept, 0.0074 and correlation coefficient of 0.9988. This official method was also used for the quantitative analysis of phosphate in the water samples and the satisfactory result was obtained. The range of phosphate concentration in the water samples are 0.033 – 2.943 mg P/L.

A SIMPLE SPECTROPHOTOMETRIC METHOD FOR THE QUANTITATIVE ANALYSIS OF PHOSPHATE IN THE WATER SAMPLES

A simple spectrophotometric method was used to determine the phosphate content in the water sampels. The method is based on the formation of molybdenum blue complex from the reaction of orthophosphate and ammonium molybdate followed by reduction with ascorbic acid in the aqueous sulfuric acid medium. The color intensity of the molybdenum blue complex is proportionally to the phosphate content in the solution. The system obeys Lamber-Beer’s Law at the 890 nm in the concentration range of 0.1-1 mg P/L and the linier calibration graph was obtained with the slope, 0.6334, intercept, 0.0074 and correlation coefficient of 0.9988. This official method was also used for the quantitative analysis of phosphate in the water samples and the satisfactory result was obtained. The range of phosphate concentration in the water samples are 0.033 – 2.943 mg P/L.

Síntesis de monetita pura por reacción heterogénea ácido base.

Se estudiaron cinco variaciones del procedimiento de síntesis de monetita modificando la agitación, la velocidad de adición de ácido fosfórico, la homogenización y la temperatura de secado. Los productos se caracterizaron por difracción de rayos X (DRX), microscopía electrónica de barrido (SEM-EDS), relación Ca/P (por titulación de calcio con permanganato de potasio y valoración colorimétrica de fósforo por la formación del complejo azul de molibdeno) y espectroscopía infrarroja con transformada de Fourier (FTIR). Los resultados de DRX, espectroscopia infrarroja y la relación Ca/P señalan que el fosfato sintetizado corresponde a monetita pura. Se encontró que los factores de síntesis que más afectan las propiedades de composición, estructura cristalina, relación Ca/P y forma y tamaño de grano de los fosfatos sintetizados son la relación estequiométrica de los reactantes y la mecanoactivación de sólido con sobrenadante.

PhosphaSense: A fully integrated, portable lab-on-a-disc device for phosphate determination in water

A portable, compact, centrifugal microfluidic system for the in situ quantitation of phosphate in water is reported. The device uses the ascorbic acid method, a colourimetric absorbance based assay, for phosphate determination. The integrated system consists of two components; the disposable centrifugal microfluidic disc and the complementary system. The microfluidic disc is designed to have similar dimensions to that of a compact disc, with a slightly thicker composition. Capillary active micro-channels are integrated internally, through which small and precise volumes of fluids can flow. Upon loading of the disc with a water sample and chemical reagents, the fluids can be moved through the disc using centrifugal force. This is created by rotation of the disc by the motor in the complementary system. The loaded fluids are then mixed due to rapid expansion and contraction as they are forced through the microfluidic channels and significantly larger reservoirs. Once mixing has occurred, this force will then drive the fluid into the optical detection zone. The low-cost optical detection system incorporated into the complementary system consists of an LED-photodiode transducing pair that measures the absorbance of light by the molybdenum blue complex formed at 880nm. The total mass of 2kg and dimensions of 20cm×18cm×14cm make this system portable and convenient for analysis at the sampling site. The limit of detection (LOD) and limit of quantitation (LOQ) of this device were 5 and 14μgL−1 PO4-P, respectively. The linear range of 14–800μgL−1 and sensitivity of 0.003AULμg−1 make it suitable for analysing water bodies with low levels of phosphate.

Quantification of Total and Soluble Inorganic Phosphate

A simple, rapid, and sensitive colorimetric microassay for inorganic phosphate (Pi) relies upon the absorption at 660 nm of a molybdenum blue complex that forms upon reduction of an ammonium molybdate-Pi complex in acid. The method for determination of total Pi uses plant tissues that have been ashed at 500 °C, whereas quantification of soluble Pi is performed with tissues extracted under mild acid conditions (which preserves acid-labile phosphate ester bonds)., 对于无机磷酸盐（Pi）的简单，快速和灵敏的比色微量测定依赖于在酸中通过钼酸铵-Pi络合物还原后形成的钼蓝络合物在660nm处的吸收。 测定总Pi的方法使用在500℃下灰化的植物组织，而可溶性P 1的定量是在温和酸条件下（其保留酸不稳定的磷酸酯键）提取的组织进行。

Dispersive micro-solid phase extraction of ortho-phosphate ions onto magnetite nanoparticles and determination as its molybdenum blue complex

A direct microextraction method, employing dispersive micro-solid phase extraction (μ-SPE) of ortho-phosphate (o-PO43−) anions onto ferromagnetic nanoparticles (MNPs) is described in this work for the first time. The method exploits the complexation of phosphate ions on the surface of positively charged magnetite nanoparticles through the formation of an inner sphere complex, which are separated from the bulk aqueous phase with the application of an adscititious magnetic field. Phosphates are eluted with sodium bicarbonate and determined spectrophotometrically as their phosphomolybdenum blue complex. The method is generally free from common interferences, likely to affect the measurement of phosphate, since it alleviates their presence already from the extraction step, thus they are absent during detection. The detection limits are as low as 0.01μM with very satisfactory precision ranging from 3.68% (intra-day) to 8.5% (inter-day) and accuracy between 91.5% and 104.8%.

An optimised micro-titer plate method for characterisation of endogenous rye phytase under industrial rye bread making conditions

A modified rapid method for the determination of phytase activity has been developed by measurements of molybdenum blue complex using micro-titer plate reader. This method requires only a small amount of extract, and it is possible to make more replicates at the same time and thus a better sampling and a higher capacity compared to measurements on spectrophotometer, which is traditionally used for those measurements. The extraction time was reduced by 36% compared to standard method and the extinction coefficient for molybdenum blue complex was determined instead of using P-standard solutions. To demonstrate the new method it was applied to the determination of the activity of phytase at a range of pH values and temperatures relevant to the rye bread making process. The activity of rye phytase was 320 nkatal g−1 grains (pH 5.5, 37 °C). The temperature optimum was 45–55 °C and the pH optimum 6.0. The study revealed that the rye phytase is very pH-sensitive and quite stable at different temperatures during the whole bread-making process. The enzyme activity of the endogenous rye phytase is optimal for a total degradation of phytic acid during rye bread making and thus the full bioavailability of phytate-bound minerals.

Effects of Dissolved Calcium and Phosphorous on Osteoblast Responses

The dissolution behavior of hydroxyapatite (HA) and its effect on the initial cellular response is of both fundamental and clinical importance. In this study, plasma-sprayed HA coatings were characterized by X-ray diffraction and Fourier transform infrared spectroscopy (FTIR). Calcium (Ca) and inorganic phosphorous (Pi) ions released from plasma-sprayed HA coatings within 3 weeks were measured by flame atomic absorption and colorimetrically molybdenum blue complex, respectively. To investigate the effect of dissolution of HA coatings on osteoblast response, additional Ca and Pi were added into the cell culture media to simulate the dissolution concentrations. Human embryonic palatal mesenchyme cells, an osteoblast precursor cell line, were used to evaluate the biological responses to enhanced Ca and Pi media over 2 weeks. Osteoblast differentiation and mineralization were measured by alkaline phosphatase-specific assay and 1,25 (OH)2 vitamin D3 stimulated osteocalcin production. The coatings exhibited an HA-type structure. FTIR indicated the possible presence of carbonates on the coatings. A dissolution study indicated a continual increase in Ca and Pi over time. In the cell culture study, enhanced osteoblast differentiation occurred in the presence of additional Ca concentration in the cell culture media. However, additional Pi concentration in the cell culture media was suggested to slow down osteoblast differentiation and mineralization.

Determination of Total Phosphorus in Biological Samples by Flow Injection Analysis with Spectrophotometric Detection

Abstract Flow injection analysis with spectrophotometric detection has been developed for the determination of phosphorus in biological samples. Potassium peroxodisulfate was used as an oxidizing reagent with aid of a platinum wire as the catalyst, and organophosphorous compounds were converted to orthophosphate which reacted with ammonium molybdate in the presence of ascorbic acid to form the molybdenum blue complex. The absorbance of the complex was detected at 880 nm.

Determination of phosphate and silicate in lead-acid electrolyte using molybdenum blue

Simple and reliable methods are described for the routine determination of phosphate and silicate content of the lead-acid cell electrolyte, based on the well-known molybdenum blue complex. The molybdate complexes are formed in the same acid electrolyte and a solution of iron(II) and fluoride ions is used as reductant for the silicomolybdic acid, while the phosphomolybdic acid is reduced by an ascorbic acid-potassium antimonyltartrate solution. Absorbance is respectively read at 828 (Si) and 882 nm (P). Solutions are quite stable and permit determinations down to 5 μg liter −1 with errors less than ±4%. The addition of citrate/tartrate removes phosphate interference of silicate determination, at least at the ratios found in the lead-acid cell electrolyte. Silicate, however, does not interfere with phosphate determination. The effect caused by several other ions has been determined.

Rapid determination of dissolved silica in natural waters

A method is described for the simple and rapid determination of soluble silica in natural waters, based on the well-known molybdenum blue complex. Soluble silica reacts with an excess of ammonium molybdate at pH 1.5–2 to form silicomolybdate. Citrate/tartrate addition reduces phosphate and arsenate interference, if present. An acid solution if iron(II) and fluoride ions is used as reductant. Absorbance is read at 828 nm. The solution is stable at least 2 hr. Traces of silica are determinable down to 10 μg SiO 2 liter −1 with an error of ± 3%. The analysis time is about 10 min. The effect caused by several other ions has been determined.

Spectrophotometric microgram determination of copper in organic compounds by wet or oxygen flask combustion

Spectrophotometric Microgram Determination of Copper in Organic Compounds by Wet or Oxygen Flask Combustion A spectrophotometric method for the microgram (2–30 ppm) determination of copper in organic compounds after wet digestion or oxygen flask combustion has been developed. The copper content is determined through the formation of the molybdenum blue complex, which is formed by the addition of 1 ml of each of 1% KCN, 1% phosphomolybdic acid and 1M HCl solutions, in the order mentioned. The absorbance is measured at 725 nm. A series of 10 compounds with 10–40% copper gave highly satisfactory results. The total average error is ±0.05% and the overall standard deviation value is 0.220. The method described is rapid, simple and accurate; the reagents required are cheap and readily available.

Appliction of high-performance liquid chromatography-flow injection analysis for the determination of polyphosphoric acids in phosphorus smokes

A flow injection analysis system for the determination of inorganic phosphate has been coupled to a high-performance liquid chromatography for use as a specific post-column detector for linear and cyclic condensed phosphoric acids. The condensed phosphates are separated by anion exchange (4 and 8% cross-linked resins), hydrolyzed to orthophosphoric acid, and condensed with molybdic acid to form a molybdenum blue complex which is detected in a flow through absorption cell. The system has been used to analyze the aerosol formed from the combustion of red and white phosphorus. Phosphates up to the P 18 polymer have been detected. The phosphorus species formed depend upon specific combustion conditions. The age of the aerosol at which a sample is collected for analysis has been found to have a pronounced effect on composition.

Rapid photometric determination of phosphorus in iron ores and related materials as phosphomolybdenum-blue

A rapid, simple and accurate method for determining phosphorus photometrically in iron ores and related materials, obviating the use of perchloric acid, is described. The sample is fused with sodium peroxide in a zirconium crucible and the melt dissolved in hydrochloric acid. The molybdenum-blue complex is developed by the addition of ammonium molybdate and hydrazine sulphate and the absorbance is measured at 725 nm. The range of the method is from 0.005 to 1.0% P. A batch of 6 samples can be analysed in about 2 hr.

ChemInform Abstract: AN IMPROVED ION‐EXCHANGER COLORIMETRY FOR THE DETERMINATION OF A TRACE AMOUNT OF PHOSPHATE

AbstractDie hochempfindliche und selektive Methode basiert auf der Konzentrierung des Phosphats als Molybdänblau‐Komplex an koaguliertem Material (hergestellt aus fein verteilten Anionen‐ und Kationenaustauschern), Sammlung des gemischten Harzes an einem Filterpapier und anschließende Messung der Extinktion des Komplexes an der resultierenden Dünnschicht der Harzphase.

An Improved Ion-exchanger Colorimetry for the Determination of a Trace Amount of Phosphate

Abstract A highly sensitive and selective method has been developed for the determination of a trace amount of phosphate. It is based on the concentration of phosphate as the familiar molybdenum blue complex on the coagulated material prepared from finely divided anion and cation exchangers, collection of the mixed resin on a filter paper, and the subsequent measurement of the absorbance of the complex on the resulting thin layer of resin phase. The calibration curve shows a good proportionality in the concentration range of 1 to 6 μg P1−1. The absorbance corresponding to 1 μg P1−1 is 0.095. The method is successfully applied to the determination of phosphate in a tap water and a river water.

Accurate spectrophotometric method for the determination of silica in rocks, minerals and related materials

Two main spectrophotometric methods have been used to determine silica: those using the yellow molybdosilicic acids and those using the molybdenum blue complex. Conditions for the production of a stable molybdenum blue complex have been re-investigated. Using suitable conditions, and a modern spectrophotometer with high reproducibility, a rapid and accurate method for the determination of silica has been developed. An important feature of the procedure is the inclusion of an “activation” stage for the silicic acid before complex formation.The method has been applied to a variety of international standards and gives accurate results with a coefficient of variation of 0.5% at the 50% silica level.

Collaborative Study of a Colorimetric Method for Determining Arsenic Residues in Red Meat and Poultry

Abstract A colorimetric method is described for the determination of arsenic residues, which uses the molybdenum blue complex for a Spectrophotometric readout. The method was studied by 9 collaborators, each analyzing 6 groups of 4 samples. Average recoveries for 0.28–2.41 ppm arsenic were 87.6–109.3%; standard deviations ranged from 0.037 to 0.225. The method has been adopted as official first action.

Automated determination of silicate and carbonates in detergents

AbstractThe analysis of silicate and carbonate builders in detergents is time consuming by standard gravimetric procedures (1,2). By modifying established Technicon AutoAnalyzer methods, rapid and simple methods of analyzing these detergent builders have been achieved. Standard AutoAnalyzer modules, arranged for colorimetric analysis, are used, and 10–15 samples per hour can be handled. In the silicate analysis, an aqueous solution of the sample is reacted with ammonium molybdate in an acid medium to form silicomolybdic acid. This acid is partially reduced by ascrobic acid forming the pentavalent molybdenum blue complex. The carbonate method is based upon the evolution of carbon dioxide gas, which is reacted with a buffered phenolpthalein solution. The color intensity of the system is inversely proportional to the carbon dioxide concentration. When a blend of carbonate and bicarbonate is present in the sample, analysis before and after heating is required.