Fluorophotometric Determination of Phosphate after Collection on a Membrane Filter as Ion Pair of Molybdophosphate with Rhodamine 6G

Abstract

A highly sensitive, rapid and facile method of fluorophotometry is described for the determination of phosphate using the ion pair formation of molybdophosphate with Rhodamine 6G. This ion pair is collected on a membrane filter made of cellulose nitrate when the sample solution is adjusted to 0.35 mol dm-3 in sulfuric acid, 1.9 mmol dm-3 in ammonium molybdate and 3.1 µmol dm-3 in Rhodamine 6G, and it is filtered through the membrane filter under suction. The membrane filter together with the ion pair is dissolved into Methyl Cellosolve. The fluorescence intensity of this solution is measured at 555 nm with the excitation at 535 nm. The calibration curve of phosphate is linear from 5 to 100 ng of phosphorus, with the correlation coefficient of 0.999; the relative standard deviation was 1.6% for 100 ng of phosphorus (n=12). Although arsenic(V) causes positive error, no ions, including silicate, commonly existing in natural water interfere with the determination of phosphate. The proposed method was applied to the determination of phosphate-phosphorus in water samples and satisfactory results were obtained.

Energy‐Dispersive X‐Ray Fluorescence Spectrometric Determination of Phosphate in Water Samples via a 12‐Molybdophosphate–Crystal Violet Complex

“…Numerous modifications have been proposed to improve sensitivity and selectivity of these methods. One of the alterations is based on ion association reaction between a heteropolyacid (HPA) and a cationic dye, such as Rhodamine B , Rhodamine 6G , or malachite green . However, most of these procedures are time‐consuming and require complicated sample preparation or large volumes of organic solvents and reagents.…”

Preconcentration of phosphate ion onto ion-imprinted polymer

“…The concentration of phosphate in environmental water usually ranges from ten to several tens ng mL −1 [2]. Several alternative methods have also been developed for measuring low concentration of phosphate in a matrix, including ion exchange chromatography [3,4], gas chromatography with the phosphine generation system [5,6], amperometric detection [7], fluorometry [8,9] and enzymatic reaction [10,11], molybdenum blue methods [12] and flow injection [13].…”

“…The solvent extraction [9,17] and solid phase extraction with an ion associate complex [8] have used and several reagents have been reported, such as Malachite Green [18], Crystal violet [19], Rhodamine 6G [8,9,17] and Rhodamine B [20] for the preconcentration of phosphate. Some carriers have used in solid phase extraction, such as an organic soluble membrane filter [8].…”

Collection of Iron(III) from Homogeneous Aqueous Solutions on Membrane Filters Using Chromazurol B with Triton X-100

“…Recently, a new technique was developed for collecting a metal complex or an ion pair as a precipitate on a membrane filter from an aqueous solution by filtration under suction. [1][2][3][4][5][6][7][8][9][10][11] If the direct collection of a metal complex or an ion pair from a homogeneous aqueous solution can be conducted by membrane filtration, this technique can be applied to a rapid and convenient separation method of the major component 12 and a simple concentration method of the minor constituent as a pretreatment method for its determination.The reagents used for separating the major component as a metal complex are not always suitable for determining the trace element in analyzing the impurity of metallic materials. It is preferred that they cause no interference in the determination of the impurity, and can at least be easily removed by a simple operation.…”