Colorimetric

Less expensive alternative for certain matrices – most prone to interferences. Least common method.

Federal Agency

Methods

 

Comments
NIOSH 7601 This is the revised format of method NIOSH P&CAM 106. This method is an elemental analysis; silicon is analyzed and reported out as silicon dioxide (SiO2). Can analyze individually quartz or cristobalite or tridymite, but cannot distinguish the different polymorphs of silica. Calls for use of NIST-traceable Standard Reference Material (SRM) or Min-U-Sil 5 (Pennsylvania Glass Sand Co., Berkley Springs, WV). Technique requires great skill to remove all silicon-containing interferences (such as silicates) without significant loss of crystalline silica. Silicates can be removed using a phosphoric acid cleanup procedure. Silicon carbide and many silicate interferences cannot be removed by the acid treatment.

 

NIOSH P&CAM 106 Does not specify use of  Standard Reference Material. Obsolete. Replaced by NIOSH 7601.

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