Classical wet techniques

The ready hydrolysis of COFj makes it especially amenable to wet analytical methods. Techniques for the measurement of fluoride in aqueous solution are well documented in standard texts [e.g. 990a], and will not be covered here. 

One method which specifically treats the determination of COF in air involves aspiration through water in a glass absorber, followed by treatment of the dissolved silicate (formed from attack of HF on the glass) with molybdate [1603]. 

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It is also desirable that the certified values be confirmed by both a classical wet technique and an instrumental technique, all of which are traceable to National Institute of Standards and Technology (NIST) reference materials. It is also important to fully understand the uncertainty or error associated with a certified value, so that you know how it impacts the data you report. Figure 15.2 is a certificate for a 1000 mg/L erbium certified reference standard used in ICP-MS, showing valnes for over 30 trace metal contaminants. Make sure that all your calibration standards come with similar certification, so yon have the confidence that yonr reported data can be scrutinized to the highest standards. 

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