Silicon determination in Portland cement by fluoride generation, using flame atomic absorption spectrometry

A new method for the determination of silicon in Portland cement, based on the generation of volatile species without sample pre-treatment, is proposed. The method reduces operational complexity and time without loss of precision and with similar accuracy as the current methods. It employs microwave-assisted (domestic microwave oven) digestion to produce volatile silicon fluorides by reaction of the sample with a fluorinated salt (CaF2) in the presence Of H2SO4 (98% w/w) using a Teflon(R) (PFA) reactor. The volatile fluorides are flushed out by a dry nitrogen stream and collected in 0.3 mol l(-1) NaOH solution where they dissolve. Silicon is determined in this solution by flame atomic absorption spectrometry (FAAS). The recoveries are between 98 and 102%, and the precision is better than 2.5% relative standard deviation (R.S.D). (C) 2001 Elsevier Science B.V. All rights reserved.