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10 ml centrifuge tube, cooled to 0°C and then treated with 200 µl of the Gringard reagent (2 M solution
of butylmagnesium chloride in tetrahydrofuran). The reaction was allowed to proceed for 10 minutes,
and then the excess Gringard reagent was decomposed by the addition of 300 µl of M HCl. The mixture
was then centrifuged and the organic layer separated and 2-20 µl portions were used for GC/MS
analysis. An example of the results obtained are shown in Figure 6.9. The concentration of
methylmercury was about 5.4 ng/g of sediment and it is seen that the signal to noise ratio was still fairly
high. The authors claimed that the detection limit for methylmercury in sediments, using the procedure
described, was about 0.1 ng/g. This Figure was based on a sample size of 0.5 g, an injection volume of
20 µl and a signal to noise ratio over that of the blank of 3.
Snell et al. [10} developed an alternative method for determining traces of mercury in natural gas
concentrates analysis using GC/AS. The interface comprised a combustion tube and an amalgamation
unit to trap the mercury compounds situated between the gas chromatograph and the MIP atomic
emission spectrometer. A diagram of the interface is shown in Figure 6.10
Figure 6.10
The Amalgamation Trap for Measuring
Mercury in Natural Gas Condensates (ref. 10)
