Investigation into alternative sample preparation techniques for the determination of heavy metals in stationary source emission samples collected on quartz filters.

Sharon Goddard,Richard Brown

doi:10.3390/s141121676

Abstract

Monitoring stationary source emissions for heavy metals generally requires the use of quartz filters to collect samples because of the high temperature and high moisture sampling environment. The documentary standard method sample preparation technique in Europe, EN 14385, uses digestion in hydrofluoric acid and nitric acid (HF/HNO3) followed by complexing with boric acid (H3BO3) prior to analysis. However, the use of this method presents a number of problems, including significant instrumental drift during analysis caused by the matrix components, often leading to instrument breakdown and downtime for repairs, as well as posing significant health and safety risks. The aim of this work was to develop an alternative sample preparation technique for emissions samples on quartz filters. The alternative techniques considered were: (i) acid digestion in a fluoroboric acid (HBF4) and HNO3 mixture and (ii) acid extraction in an aqua regia (AR) mixture (HCl and HNO3). Assessment of the effectiveness of these options included determination of interferences and signal drift, as well as validating the different methods by measurement of matrix certified reference materials (CRMs), and comparing the results obtained from real test samples and sample blanks to determine limits of detection. The results showed that the HBF4/HNO3 mixture provides the most viable alternative to the documentary standard preparation technique.

Highlights

Over recent decades, the worldwide requirement for environmental monitoring of industrial pollutant emissions, including for heavy metals, has been increasing prompted by ever tighter legislation governing emissions
The results showed that the HBF4/HNO3 mixture provides the most viable alternative to the documentary standard preparation technique
Chloride was present in both proposed matrices: at residual levels in HBF4 and as a major component (HCl) in the aqua regia (AR) extraction matrix

Summary

Introduction

The worldwide requirement for environmental monitoring of industrial pollutant emissions, including for heavy metals, has been increasing prompted by ever tighter legislation governing emissions. Heavy metals are naturally occurring in the environment, but human activities such as mining, metal smelting and refining, and combustion of fossil fuels have significantly increased emissions, and population exposure. Studies by the World Health Organisation (WHO) have shown heavy metals to be harmful to human health [1], with long term exposure resulting in neurotoxic and carcinogenic effects. The majority of airborne metals emissions are bound to particulate matter (PM), which has been shown by epidemiological and toxicological studies to have various inflammatory, cytotoxic, mutagenic and carcinogenic effects on the lungs, dependent on the PM size fraction and composition [2]. Industrial pollution control in EU member states is currently governed by the European Industrial Airborne PM is considered a contributing factor in increasing the risk of heart ailments and heart attacks [3].

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Conclusion