Spectrophotometric Determination of Low Levels of the Orthophosphate Anion as Molybdenum Blue using Sodium Thiosulphate Reducing agent

Abstract

A simple spectrophotometric method for the determination of low levels of the orthophosphate (PO43-) in environmental water systems is reported. The method is based the formation of the phosphomolybdate from the condensation of molybdate and orthophosphate in aqueous acid medium followed by reduction with sodium thiosulphate to form phosphomolybdenum blue. The system obeys Beer’s law at 880 nm (λmax) in the 0.005–0.06 mg P mL-1 phosphate concentration range. Molar absorptivity, Sandell’s sensitivity and correlation coefficient values for the determination were 57526 L mol-1 cm-1, 0.2835 μg cm-2 and 0.9948 respectively. The limit of detection was 2.213 x 10-3 mg P mL-1. The results of PO43- determination in water samples obtained using the spectrophotometric method developed in this study, compare favourably with those generated using the Murphy and Riley method which is commonly used for this analysis. Therefore, the study ably demonstrates the suitability of the present spectrophotometric method for analysis of the orthophosphate in environmental water samples.

Verifikasi Metode Pengujian Kadar Ortofosfat (PO43-) Dalam Air Sungai Menggunakan Asam Askorbat Berdasarkan SNI 06-6989.31-2005

“…Senyawa kompleks biru molibden yang terbentuk kemudian diukur menggunakan spektrofotometer pada panjang gelombang 880 nm. Panjang gelombang ini digunakan karena pada senyawa kompleks biru molibden diketahui memiliki absorbansi tertinggi dan dipilih sebagai λmax (Nalumansi et al, 2020).…”

Spectrophotometric Determination of Phosphates in Detergent Samples Available in Tansen, Palpa

“…The phosphate concentration in the detergent sample is directly proportional to the intensity of blue colour developed, which can be measured spectrophotometrically at the wavelength of maximum absorbance; Max (Adelowo & Agele, 2016). Different types of reducing agents have been reported in literature like sodium sulphide (Agbazue et al, 2015), thiourea (Shyla et al, 2011), sodium thiosulphate (Nalumansi et al, 2020), hydrazine hydrate (Pradhan &Pokhrel, 2013), and so on. This research aims to assess the amount of phosphate in detergent samples of local and foreign brands and observe if there is a significant difference between them.…”