Application of the microwave acid digestion technique to the pyrophosphoric acid method for quantitative analysis of free silica in dust.
An accurate and simple procedure for determining the quantity of free silica in respirable dust samples by the pyrophosphoric acid method was achieved by employing a closed vessel dissolution technique using microwave heating. Dissolution conditions were optimized by using quartz particles less than 10 microns in diameter as representative respirable-size free silica and potassium feldspar (K-feldspar) of the same size as the matrix. The technique enabled dissolution of 100 mg of K-feldspar by pyrophosphoric acid in 3 min. Quartz recovery was 97% under these conditions. The technique was also tested on mixtures of quartz and K-feldspar in various ratios with reproducible and accurate results. These data satisfy the requirements for analysis of small amounts of respirable dust samples in work environments.
Shinohara
Y
Y
National Institute of Industrial Health, Kawasaki, Japan.
D004391:Dust / Q000032:analysis*; D008872:Microwaves; D010756:Phosphoric Acids; D015203:Reproducibility of Results; D012822:Silicon Dioxide / Q000032:analysis*
D004391:Dust; D010756:Phosphoric Acids; D012822:Silicon Dioxide