Mercury in samples of gas mixtures – a review of mercury sampling and determination methods

The determination of the composition of gas mixtures, especially those analytes which exist, for example, as contaminants for the main components of the gas mixture, very often requires the concentration of the analyte so that it can be quantified. The analysis of gaseous environmental samples, including air and air samples at workplaces, is difficult, which results from: the need to work with samples with an extensive matrix and heterogeneous distribution of pollutants, the stability of the analyte and the presence of interfering substances (interferents) in the sample. On the other hand, the analysis of trace components of gaseous fuels is difficult due to the need to collect a suitably concentrated sample so that these components can be quantified. This article provides an overview and analysis of the methods used for the collection and determination of mercury in gas mixtures. Currently, there are standardized mercury collection and determination methodologies dedicated to matrices such as air, workplace air, waste gases or natural gas. These are both manual and fully automated methods. Most of the methods described in the literature on the subject consist of two stages, i.e. the stage of collecting a sample for a solid or liquid sorbent and the stage of desorption and determination of the mercury content in the collected sample using methods dedicated to the analysis of this element. The most frequently used methods for collecting mercury samples in gas mixtures are: the gold amalgamation method and the sorption methods on powder sorbents (such as activated carbon, hopcalite, impregnated silica gel), glass fibers, impregnated cellulose filters and liquid sorbents (such as e.g. acids). The methods of sample desorption are varied and depend on the material on which the analyte has been absorbed and the selected mercury determination method. Three methods are mainly used to analyze samples for mercury content, i.e. the cold vapor atomic absorption spectrometry method (CV-AAS), the cold vapor fluorescence atomic spectrometry method (CV-AFS) and the inductively coupled plasma mass spectrometry method (ICP-MS). However, it should be kept in mind that although the methods available and used for the analysis of mercury content in gas are standardized, they are not resistant to the presence of hydrocarbons and hydrogen sulphide in the tested samples. These are the compounds that are most often mentioned as substances interfering in the determination of mercury in gases using the above-mentioned methods