简介:This is similar to the method in the Criteria Document [3] and P&CAM 259 [4] which has been collaboratively
tested [1]. This method is similar, except for sample collection, to S315 [5,6]. Method P&CAM 109 [7,8,简介:This is similar to the method in the Criteria Document [3] and P&CAM 259 [4] which has been collaboratively
tested [1]. This method is similar, except for sample collection, to S315 [5,6]. Method P&CAM 109 [7,8,9], which incorporates an
internal standard, has been dropped. XRD can distinguish the three silica polymorphs and silica interferences can be eliminated
by phosphoric acid treatment. IR (methods 7602 and 7603) can also quantify quartz, cristobalite and tridymite if amorphorous silica
and silicates are not present in large amounts. However sensitivity is reduced if multiple polymorphs are present and secondary
peaks must be used. Crystalline silica can also be determined by visible absorption spectrophotometry (e.g., Method 7601), but
polymorphs can not be distinguished. Visible absorption methods also have larger laboratory-to-laboratory variabilty than XRD and
IR methods and therefore are recommended for research use only [10].详细>