Working environment and sample handling

In situ analyses are rarely available for marine trace element measurements. Therefore, once a sample has been collected, a number of operations have to be carried out almost immediately including subsampling, filtration, if required, and storage or pre-concentration. Because of the extremely low levels at which trace elements occur in most ocean waters (Table 12-1), these procedures must be carried out with as much care and attention against contamination as during subsequent analysis steps. Many of the systematic errors that have 

It is beyond the scope of this section to describe the lay-out of clean laboratory facilities in detail see the excellent reviews by Whyte (1991) and Liebennan (1992). TTie basic concept behind the operation of such rooms is that they are under positive pressure and that the air is first drawn through one or two pre-filters, and then forced through a high efficiency particle air (HEPA) filter which removes typically 99.97 % of particles S 0.3 nm in diameter. 

Standards for the major classes of clean room vary from one country to another. The US FS209D standard probably is the most common one. Usually it is defined in terms of the number of particles of a specified diameter in a certain volume of air. A designed class 100 

Unidirectional flow hood in conventional laboratory Laboratory coat, polyethylene gloves i.e., body parts extending into the hood must be covered by non-contaminating clothing 

Class 100 000 Minimal specialized clothing smocks, street shoe covets, head covers 

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