Rapid Determination of Talc Powder in Flour by FT-IRS

FT-IRS with attenuated total reflection (ATR) was applied to the rapid determination of talc powder illicitly mixed into flour. Medium IR detector was used in the analysis. By referring the standard IR spectra and considering the absorption interference of flour, 2 of the 3 IR absorption peaks of talc powder, i.e., the peaks at 3 674.96 cm-1 and 668.16 cm-1, were selected as the characteristic absorption peaks to determine whether talc powder was present or not in the sample. It was shown that when the content (w%) of talc powder in flour was lower than 0.5% or 0.2%, no absorption was found in the spectra at the 2 wavebands respectively. Value of 1% (w%) was taken as the detection limit. In addition, magnitude of absorption intensity at both the wavebands was increased with the increase of amounts of talc powder present, hence the content of talc powder in samples of flour could be estimated. Working conditions of the instrument were as follows: ① scanning range: 4 000-650 cm-1; ② resolution: 8 cm-1;③ number of time of scanning signal accumulation: 32 and ④ pressure constant of ATR: 100.