High through-put groundwater arsenic speciation analysis using an automated flow analyzer

The occurrence of geogenic arsenic (As) in groundwater is a global public health concern. However, there remain large gaps in groundwater As data, making it difficult to identify non-compliant domestic wells, partly due to lack of low-cost methods capable of rapid As analysis. Therefore, the development of high through-put and reliable on-site determination methods for inorganic As is essential. Herein, a portable automated analyzer was developed for the determination of arsenite (As(III)), arsenate (As(V)) and phosphate in As contaminated groundwater based on a previously adapted method for molybdenum blue spectrophotometry. After the optimization of the chemical reactions and flow manifold, the system demonstrated a high sample through-put (4.8/h for As(III), As(V) and phosphate analysis), allowing this system to screen 125 samples in 24 h. Other advantages include low operational costs (0.3 CNY per sample), appropriate sensitivity for contaminated groundwater (detection limits of 4.7 µg/L, 8.3 µg/L and 5.4 µg/L for As(III), As(V) and phosphate, respectively), good linearity (R² > 0.9996 at As concentrations up to 1600 µg/L) and high precision (relative standard deviations of 3.5% and 2.8% for As(III) and As(V), respectively). The portable system was successfully used for As speciation analysis in 5 groundwater samples collected from multi-level wells at Yinchuan Plain, northwestern China, with total As concentrations ranging from 75.7 to 295.0 µg/L, independently assessing As speciation, providing a promising novel method for the rapid on-site screening of As in tens of millions of domestic wells worldwide.