title: Application of the microwave acid digestion technique to the pyrophosphoric acid method for quantitative analysis of free silica in dust.
abstract: 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.
authors.affiliation: National Institute of Industrial Health, Kawasaki, Japan.
authors.forename: Y
authors.initials: Y
authors.lastname: Shinohara
mesh_terms: D004391:Dust / Q000032:analysis*; D008872:Microwaves; D010756:Phosphoric Acids; D015203:Reproducibility of Results; D012822:Silicon Dioxide / Q000032:analysis*
chemical_list: D004391:Dust; D010756:Phosphoric Acids; D012822:Silicon Dioxide