Spectrophotometric Determination Of Phosphate Research Articles

Spectrophotometric determination of phosphate in presence of arsenate

A simple and sensitive spectrophotometric method has been optimized for the determination of phosphate in the presence of arsenate. This method is based on the formation of phosphomolybdate complex from phosphate and added molybdate ion in an acidic medium, followed by the reduction of the complex with hydrazine hydrate. The system obeys Lambert-Beer’s law in the concentration range 60-1080 ppb. The optimized volume of different reagents was 3.5 mL of 0.25% ammonium molybdate, 1.5 mL of 0.25 N sulfuric acids, and 1 mL of 0.5 M of hydrazine hydrate. The time required for the full-color development was 15 minutes at 30oC. The arsenate interference was successfully removed by using sodium thiosulphate and sodium metabisulfite below the arsenic concentration of 100 ppb. 0.2 mL of 1 M sodium metabisulfite and 1 mL of 0.1 M sodium thiosulphate were found to be the optimum volume for inhibiting arsenate interference below 100 ppb arsenate concentration.

Chemometrics-assisted cross injection analysis for simultaneous determination of phosphate and silicate

ABSTRACTThis work presents a novel method for simultaneous spectrophotometric determination of phosphate and silicate by using a cross injection analysis (CIA) coupled with the use of partial least squares (PLS) for data evaluation. The detection principle is based on the well-known ‘molybdenum blue’ method. The molybdate ions in the presence of stannous chloride in acidic medium give phosphomolybdenum blue and silicomolybdenum blue as products. In this work, all the liquids, including sample and reagents were simultaneously introduced into a CIA platform by using two peristaltic pumps for controlling the x-channel and y-channel flow which was automatically manipulated by using in-house control board. Crossflow provides sufficient mixing inside the platform prior detection of the absorption spectra of blue complexes in the wavelength of 400–900 nm. Since spectra of the blue colour product of phosphate and silicate are resemblant, these two analytes therefore reciprocally interfere with one another. This results in difficulty in simultaneous analysis of phosphate and silicate. In this work, PLS was utilised as assistor of CIA system for simultaneous analysis of phosphate and silicate using molybdenum blue reaction without using any modification of reagents and addition of selective masking agent. The calibration ranges are 0.1–6 mgP L−1 and 5–100 mgSi L−1 for phosphate and silicate, respectively. By using CIA coupled with PLS for data evaluation, the analysis of two analytes was achieved within 1.5 min with only single injection. The developed system was applied to natural water samples and the system was validated with the conventional methods. By statistical paired t-test, there was no evidence of significant difference at 95% confidence level (tstat = 2.28, tcritical = 2.31 and tstat = 0.62, tcritical = 2.31 for phosphate and silicate, respectively). This implied that the chemometrics-assisted CIA system was successfully developed for simultaneous spectrophotometric determination of phosphate and silicate.

Spectrophotometric determination of phosphate in matrices from sequential leaching of sediments

AbstractThe speciation of Phosphorus (P) in geologic materials can inform diverse investigations in such as aquatic biogeochemistry, soil sciences, and paleo‐oceanography. Here, we describe in detail a set of sequential extraction schemes to measure P concentrations from several operationally defined phases: pore water, exchangeable or loosely sorbed P, Fe‐bound P, P associated with biogenic apatite, P associated with authigenic apatite and carbonate forms, P associated with detrital apatite and inorganic forms, and organic P. The two benefits of the procedures we describe compared to prior methodological studies are: (1) fast, simple and inexpensive colorimetric methods have been developed for P determination in all the different matrices; and (2) the Fe‐bound phosphorus pool is separated into two fractions, allowing the P associated with most reactive Fe‐fraction to be distinguished from P bound to the remainder of the Fe‐oxides. Adaptations of these procedures to optimize the characterization of P pools in a range of material types are also outlined.

Leakage of inorganic compounds from artificially-aged radish (Raphanus sativus L.) and Chinese cabbage (Brassica rapa ssp. pekinensis) seeds and use of phosphate leakage from single seed as a tool for assessing viability

Inorganic compounds, Ca, Mg, P, Na, K, B, Mo, Mn, Cu, Fe and Zn, in the seed leachate of artificiallyaged (AA) seeds from three cultivars of radish (Raphanus sativus L.) and Chinese cabbage (Brassica rapa ssp. pekinensis) seeds were measured and compared to those of non-aged (NA) seeds, and a technique to detect phosphate leakage from the leachate from single seeds was developed as a tool for assessing viability. K leached out in much greater quantities than other elements in both NA and AA seeds, followed by P, Na, Ca, Mg, and B in the AA seeds. The Mn and Cu were not detected in any cultivars, while Mo and Fe in Chinese cabbage seeds and Zn in radish seeds were only present in trace amounts of leachate from AA seeds. In general, K, P, Na, Ca, Mg, and B leakage occurred in large amounts from AA seeds relative to NA seeds, though there were different ratios of AA to NA seeds. Evaluation of the ratio of AA to NA seeds of inorganic compound leakage revealed that P was greatest, followed by Mg, K, Na and Ca. A spectrophotometric determination of phosphate from single seed leachate was developed using multi-plate reader. This technique is simple, fast, nondestructive and inexpensive, and applicable to many individual seeds at one time. The relationships between percent germination and absorbance (630 nm) of the single seed leachate with phosphate leakage from Chinese cabbage and radish seeds that had been artificially aged to give various viability levels appeared to have very high negative correlations. In conclusion, phosphate detection from single seed leakage could provide a valuable and practical tool for assessing seed viability.

Spectrophotometric Determination of Phosphate in Sugarcane Juice, Fertilizer, Detergent and Water Samples by Molybdenum Blue Method

A simple and sensitive spectrophotometric method has been developed for the determination of phosphate in mg per liter (parts per million) concentration range in sugarcane juice, water, fertilizer and detergent samples. The amount of phosphate is determined by molybdenum blue phosphorus method in conjugation with UV-visible spectrophotometer. This method is based on the formation of phosphomolybdate complex with the added molybdate followed by the reduction of the complex with hydrazine hydrate in aqueous sulphuric acid medium. The system obeys Lambert-Beer’s law at 840 nm in the concentration range 0.1-11 ppm. The colour intensity of the reduced phosphomolybdate solution is found to be proportional to the amount of phosphate present in sugarcane juice, water, fertilizer and detergent samples. The reaction conditions as well as the various experimental parameters affecting the development and stability of the coloured complex were carefully investigated and optimized for the quantitative determination of phosphate present in various samples. The optimized concentrations of various reagents used are 0.20N sulphuric acid, 0.02M hydrazine hydrate and 0.20% ammonium molybdate. The effect of time on the formation of phosphomolybdenum blue complex and addition of the order of the reagents was also studied. Scientific World, Vol. 11, No. 11, July 2013, page 58-62DOI: http://dx.doi.org/10.3126/sw.v11i11.9139

An Automated Multi-Pumping Pulsed Flow System with Spectrophotometric Detection for the Determination of Phosphate in Natural Waters

In this work, an automated multipumping pulsed flow system was implemented for the determination of phosphate in natural waters. The developed flow approach was based on the spectrophotometric determination of phosphate by using the vanadomolybdate reaction. The exploitation of a very simple manifold configuration relying on the utilization of just two active components, in this case two solenoid actuated micropumps that were accountable for sample and reagent insertion and commutation, reaction zone formation, and solutions propelling, provided a great operational and optimization simplicity, low reagent consumption, and waste minimization. Linear calibration plots for phosphate concentrations of up to 20 mg L−1 (R2 = 0.999, n = 6) were obtained, with a detection limit of 0.2 mg L−1. The sampling rate was about 60 samples per hour. The system was applied to the monitoring of phosphate in local streams at specific sampling stations.

Spectrophotometric Determination of Orthophosphate Based on Pulsating Variable Optical Path Length and Self-Calibration Technique

Spectrophotometric Determination of Orthophosphate Based on Pulsating Variable Optical Path Length and Self-Calibration Technique

Spectrophotometric determination of orthophosphate ions for conducting indicator investigations in stratal waters

The methodologies for determining orthophosphate ions by spectrophotometry and flow-injection analysis for 1995–2011 in different features are briefly described in the paper. The method of the spectrophotometric determination of orthophosphate in the form of molybdophosphoric heteropolyacid via reduced ascorbic acid in the presence of potassium antimonyl tartrate has been modified. The method allows analysts to determine 0.1–1.0 mg/L of orthophosphate ions in natural waters and has been tested by analyzing a model solution similar to the subterraneous waters of the Arigol licensed area. The advantages of the developed method, compared to the certified method, consist of the possibility of the express assessment and lower consumption of chemical reagents. The method is suitable for indicator investigations in geophysics.

Development of a flow method for the determination of phosphate in estuarine and freshwaters—Comparison of flow cells in spectrophotometric sequential injection analysis

A sequential injection system with dual analytical line was developed and applied in the comparison of two different detection systems viz; a conventional spectrophotometer with a commercial flow cell, and a multi-reflective flow cell coupled with a photometric detector under the same experimental conditions. The study was based on the spectrophotometric determination of phosphate using the molybdenum-blue chemistry. The two alternative flow cells were compared in terms of their response to variation of sample salinity, susceptibility to interferences and to refractive index changes. The developed method was applied to the determination of phosphate in natural waters (estuarine, river, well and ground waters). The achieved detection limit (0.007 μM PO 4 3−) is consistent with the requirement of the target water samples, and a wide quantification range (0.024–9.5 μM) was achieved using both detection systems.

A modified spectrophotometric determination of orthophosphate with reagent-immobilized poly(vinyl alcohol) films

A simple and rapid method for the determination of orthophosphate was developed in this study. The method is based on a reagent-immobilized poly(vinyl alcohol) (PVA) film which is prepared by temporary immobilization of sensitive reagents on the glass slide. The preparation conditions of the film were investigated in detail. Under the optimum conditions, the absorbance is linearly proportional to the concentration of phosphorus from 0.65 to 8.1 μmol L−1 and the limit of detection is 0.5 μmol L−1 of phosphorus. The relative standard deviation is 2.9% (n = 10). The proposed method has been effectively used for the determination of orthophosphate in various water samples.

Spectrophotometric determination of phosphate and silicate by sequential injection using molybdenum blue chemistry

This paper presents a spectrophotometric sequential injection (SI) determination of phosphate and silicate in environmental samples and cell cultivation medium using the molybdenum blue reaction. The interference of silicate in the determination of phosphate was eliminated by using a reagent composed of 5 mmol l −1 ammonium molybdate in 0.2 mol l −1 nitric acid, containing 0.25% (w/v) oxalic acid to avoid the formation of molybdosilicic acid. The interference of phosphate in the determination of silicate was avoided adding a 10% (w/v) oxalic acid solution to the reaction zone where the molybdophosphoric and molybdosilicic acids were previously formed, in order to destroy the molybdophosphoric acid. To perform this task in the single line SI system, obtaining a total sample and reagent zones penetration, it was used as a combination of sandwiching the sample zone between reagent zones and flow reversal through an auxiliary reaction coil. The method has a phosphate sampling frequency of 75 h −1, with a linear dynamic range between 0.2 and 7 mg l −1 and a detection limit of 0.1 mg l −1 PO 4 3=P. For silicate, the sampling frequency is 40 h −1 with a linear dynamic range between 5 and 50 mg l −1 and a limit of detection of 1 mg l −1 SiO 3 2=Si.

Simultaneous Spectrophotometric Determination of Phosphate and Silicate by a Stopped-Flow Sequential Injection Method

A sequential injection analysis method for the simultaneous spectrophotometric determination of phosphate and silicate has been developed. The method is based on the different reaction rates of the heteropolymolybdate formation reactions. Concentrations within the range 0.026—0.485 mmol P l−1 and 0.125—2.848 mmol Si l−1 have been determined at a frequency of 30 samples per hour. An R.S.D. of 2.1% was obtained for 0.162 mmol P l−1 and of 1.1% for 1.424 mmol Si l−1. The method was found to be suitable for the determination of phosphate and silicate in wastewater.

Spectrophotometric determination of phosphate in waters of Egypt

The proposed method is used for determination of trace amounts of phosphate in water samples especially of Dakahlia Governorate. The recommended procedure is based on the formation of molydophosphoric acid which upon, selective reduction with the reducing agent oxalyldihydrazide produces a blue color due to the molybdenum blue. The intensity of the blue color is proportional to the amount of phosphate initially incorporated in the heteropoly acid. The resulting blue complex could be determined in the range of 2.25 to 22.46 μg P with molar absorptivity of 33418 L−1 mol−1 cm−1 at 880 nm. The reduction of phosphomolybdate complex by oxalyldihydrazide is chosen in the work and the result is compared with those obtained with the reducing agent potassium antimonyl tartrate, the reduction methods are frequently recommended for manual analysis of waters and wastes for P.

Spectrophotometric determination of phosphate with alizarin red sulphonate

Spectrophotometric determination of phosphate with alizarin red sulphonate

Spectrophotometric determination of phosphate with alizarin red sulphonate

The formation of complexes between orthophosphate and alizarin red sulphonate (ARS) has been ascertained. One or two kinds of complexes are formed in solution according to the pH of the medium with PO 3− 4:ARS ratios of 1:3 and 1:2 at pH 6.6 and 8.3 with formation constants of 2.97 × 10 20 and 1.3 × 10 9 at λ max 478 and 520 nm, respectively. The development of the 1:3 complex was utilized for the determination of orthophosphate with a working concentration range of 0.03–6.00 μg ml −1 phosphorus (ϵ = 1.14 × 10 4 l mol −1 cm −1 at 478 nm). The interference of some anions and cations was investigated. Structures of the isolated solid complexes are suggested based on elemental analysis and infrared spectrophotometric measurements. A procedure for the determination of different forms of phosphorus has been elaborated and applied to differentiate between non-organic and organically bound phosphorus in re-used water effluents.

Effects of acidity and molybdate concentration on the kinetics of the formation of the phosphoantimonylmolybdenum blue complex

The effects of variation of acidity and molybdate concentration on the spectrophotometric determination of phosphate by the method of Murphy and Riley were studied. The [H +]:[Mo] ratio was found to be a crucial parameter which not only influences the form of the final reduced complex, but also plays a key role in controlling the reaction kinetics. Normal colour formation of the reduced phosphoantimonylmolybdenum blue complex was only observed with a ratio between 60 and 80; the reaction was faster at low acidities. Silicate is a possible source of interference at high temperatures, but the formation of the silicoantimonylmolybdenum blue complex was found to be much slower than that of the corresponding phosphorus species.

Spectrophotometric Determination of Phosphate in Natural Water after Flotation as an Ion Pair of Molybdophosphate with Rhodamine B

A sensitive and accurate spectrophotometric method is described for the determination of phosphate in natural water using Rhodamine B. The ion pair of molybdophosphate with Rhodamine B is floated at the phase boundary between an ethyl ether phase and an aqueous phase: the aqueous phase comprises 1.0 mol dm-3 nitric acid, 33 mmol dm-3 sodium molybdate and 20 μmol dm-3 Rhodamine B. The small amount of excess Rhodamine B extracted into ethyl ether is removed by washing the organic phase with 25 cm3 water. The floated ion pair is dissolved by adding methanol into the ethyl ether phase after discarding the aqueous phase. The calibration curve for phosphate is linear up to 1.0 μg of phosphorus with the correlation coefficient of 0.999. The apparent molar absorptivity of phosphate was 4.1×105 dm3 mol-1 cm-1 at 555 nm; the relative standard deviation was 2.0% for 1.0 μg of phosphorus (10 determinations). Arsenate causes positive error, while no ions commonly existing in natural water, except large amounts of silicate ions, interfere with the determination of phosphate. The proposed method was applied to the determination of phosphate-phosphorus in some samples of natural water; satisfactory results were obtained.

The Spectrophotometric Determination of Phosphate Following the Collection of Ion Pair of Molybdophosphate with Bis[2-(5-chloro-2-pyridylazo)-5-diethylaminophenolato]cobalt(III) on an Organic Solvent-Soluble Membrane Filter

Abstract A rapid and sensitive method of determining phosphate was described. The ion pair of molybdophosphate with bis[2-(5-chloro-2-pyridylazo)-5-diethylaminophenolato]cobalt(III) (Co-5-Cl-PADAP) formed in 0.075 mol dm−3 sulfuric acid, 0.225 mmol dm−3 ammonium molybdate, and 25 μmol dm−3 Co-5-Cl-PADAP was collected on an organic solvent-soluble membrane filter made of cellulose nitrate. The membrane filter with the ion pair was then dissolved into N,N-dimethylformamide, and the absorbance of the solution was measured for the determination of phosphate. The calibration curve was linear up to 0.4 μg as phosphorus, with the correlation coefficient of 0.999, and the apparent molar absorption coefficient of phosphate was 2.9×105 dm3 mol−1 cm−1. The relative standard deviation was 1.7% for 0.4 μg of phosphorus. Although dodecyl sulfate existing in an amount ten times that of phosphorus caused a positive error, no ions commonly existing in natural waters interfere with the determination of phosphate. The proposed method was applied to the determination of μg dm−3 levels of phosphate-phosphorus in natural waters, and satisfactory results were obtained.

Extraction - Spectrophotometric Determination of Phosphate Using N-Phenylbenzohydroxamic Acid

Abstract A simple solvent extraction and spectrophotometric method for the determination of micro amount of phosphate (PO4) is described. Phosphate is selectively separated from associated elements by reacting it with calcium and extracting excess calcium with N-phenylbenzohydroxamic acid (PBHA) at pH 11.3. The excess calcium was determined in ultra-violet and visible region and hence the phosphate content was calculated. The Beer's law is obeyed in the range 0.5 − 10.0 ppm at 340 nm and 0.25 - 8.0 ppm at 560 nm of phosphate for a fixed amount of calcium (20.0 ppm). These results are also compared with those obtained by atomic absorption spectrophotometry. The method has been applied for the determination of phosphate in pharmaceutical and other samples.

The Spectrophotometric Determination of Phosphate and Arsenate by Selective Extraction with Mixed Solvents

Abstract A spectrophotometric method for the simultaneous determination of phosphate and arsenate by selective solvent extraction was examined. First, molybdophosphate was extracted with 1-butanol–chloroform in the presence of molybdoarsenate, and then the molybdoarsenate in the aqueous phase was extracted with MIBK, followed by reduction directly in the organic phase to Molybdenum Blue.