Quantitative Analysis of Phosphate in Laundry Detergents for Environmental Impact Assessment Using the Molybdenum Blue Method

Abstract

Phosphates are commonly used in laundry detergents as water softening agents, but their excessive discharge into aquatic environments has been linked to eutrophication and the deterioration of water quality. Despite international efforts to regulate phosphate use, phosphate-based detergents remain prevalent in regions like Malaysia, where regulatory oversight is limited. This study aimed to quantify phosphate concentrations in selected commercial liquid laundry detergents available in the Malaysian market and evaluate their potential environmental impact using the molybdenum blue method. Five detergent brands (A to E) were analyzed following a 1:500 dilution protocol. Phosphate levels were determined based on a calibration curve constructed from standard solutions (0–5 mg/L as PO₄³⁻), with absorbance measured at 650 nm. The method showed excellent linearity (R² = 0.9885) and good precision, with relative standard deviations (RSD) below 10% for both standard and sample measurements. Phosphate concentrations in the detergent samples ranged from 0.411 mg/L to 1.390 mg/L, with Brand E showing the highest level. When translated to estimated phosphate discharge per laundry cycle, values ranged from 20.6 mg to 69.5 mg per 50-liter wash—well below the European Union’s threshold of 500 mg per standard dose. However, the cumulative environmental impact of frequent detergent use, particularly from products with higher phosphate content, remains a concern. These findings highlight the need for increased awareness, stronger regulatory measures, and reformulation of detergent products to minimize phosphate pollution in aquatic ecosystems.