PLEASE HELP!! THANKS IN ADVANCE! QUESTION: You are an environmental chemist for

Question

PLEASE HELP!! THANKS IN ADVANCE!

QUESTION: You are an environmental chemist for the United States of America’s Environmental Protection Agency (US EPA). It is just after the BP oil spill and your assignment is to assess the amount of Mercury that was released into the environment as a result of the spill. Please specify how you would identify Mercury in the environment (i.e. coastal area/marshes and water supplies)? Please be specific and state a rationale for why you have included a given piece of instrumentation.

EACH ANSWER SHOULD HAVE FOLLOWING PARTS:

1. Title: Please describe the procedure to be conducted (i.e. rough separation).

2. Description of Procedure :Please describe which the respective analytical procedure. Some questions that should be addressed are:

When answering please consider the following questions:

*What samples they want to analyze?

*What they are looking for (specifically) from each analysis?

*What analytical techniques are most appropriate?

*What detection limits can be achieved by each method?

3.Rationale for Procedure

*What would constitute a ‘normal ‘concentrations?

*Whether the sample is likely to be a mixture of components?

*If qualitative analysis is required? Why?

*If quantitative data is required? Why?

Explanation / Answer

Analysis of trace levels of Mercury using Cold Vapor Atomic Fluorescence Spectroscopy (CVAFS)

A CVAFS instrument mainly consists of two parts, one is a mercury (Hg) vapor generator and another is the Atomic Fluorescence detector. While handling solid samples, the sample is digested first to turn it into a solution. The solution reduced with stannous chloride to release the Hg vapour. The vapour is then excited by a UV light source at a wavelength of 253.7 nm. The Hg atoms in the sample absorb this wavelength and emit florescence which is then detected by a photomultiplier tube as a detector. The florescence intensity is propotional to the amount of Hg in the sample. Another procedure referred to as Amalgamation is often introduced to enhance the detectio limits of Hg. Here, the Hg vapor is collected by amalgamation on a gold trap which is then slowly heated to release Hg inorder to get a better signal-to-noise ratio. This allows detection of very trace levels of Hg in the range of parts per trillion (ppt).

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