Effective Monitoring of Antimony in Water

Antimony, a metalloid with significant toxicity, has become a growing concern in water quality management due to elevated concentrations in certain mining, smelting, and industrial discharge areas. Reliable monitoring of antimony is essential for safeguarding drinking water sources and aquatic ecosystems. 

An effective monitoring strategy should integrate proper sampling protocols, laboratory techniques, field screening tools, and online instrumentation, all underpinned by rigorous quality assurance.

Sample Collection and Preservation

The first step is correct sampling and preservation. For total antimony, unfiltered samples are acidified and digested; for dissolved antimony, samples are filtered through 0.45 μm membranes before acidification. Preservation typically uses nitric acid to adjust pH below 2, which prevents adsorption onto container walls and stabilises the species. Samples should be analysed as soon as possible, as prolonged storage may alter antimony speciation despite acidification.

Laboratory-Based Analytical Methods

High‑precision laboratory analysis remains the cornerstone of antimony monitoring. Three principal techniques are widely adopted.

Hydride generation atomic fluorescence spectrometry (HG‑AFS) is the standard method in many countries. After digestion, antimony is reduced to stibine (SbH₃) by a strong reductant such as potassium borohydride. The hydride is swept into an atomiser, where it generates atomic fluorescence upon excitation by a hollow cathode lamp. This method offers exceptional sensitivity with detection limits down to 0.02 µg/L, making it suitable for both clean surface waters and effluents. Its selectivity is high, though arsenic and selenium can interfere and are usually masked with appropriate reagents.

Graphite furnace atomic absorption spectrometry (GFAAS) is another widely used option. A small volume of digested sample is injected into a graphite tube, heated stepwise to dry, char, and atomise. The absorbance of antimony atoms is measured at a characteristic wavelength. With a typical detection limit of about 1.4 µg/L, GFAAS is robust and less susceptible to matrix interferences than flame methods; matrix modifiers can further enhance performance.

Inductively coupled plasma mass spectrometry (ICP‑MS) offers the advantages of multi‑element capability and ultra‑low detection limits, often in the sub‑µg/L range. It is ideal for comprehensive screening, though it requires higher capital investment and skilled operation. For most routine monitoring, HG‑AFS and GFAAS provide cost‑effective and reliable results.