A new method for determination of iron (II) in α-Fe2O3 for a combustible gas sensor has been developed using a flow-injection analysis (FIA) system with spectrophotometric detection which is based on the reaction of iron (II) and 2, 4, 6-tris (2-pyridyl) -s-triazine. A α-Fe2O3 sample (0.1g) was decomposed with 1 ml of 46% hydrofluoric acid and 2m1 of 4.5M sulfuric acid containing 1 x10-3 M vanadium (V), and then 25m1 of 4w/v% boric acid was added to mask excess fluoride ion, followed by diluting the solution to 200m1 by water. In the FIA system, a sample solution injected into the carrier is mixed with a stream of 2, 4, 6-tris (2-pyridyl) -s-triazine and a masking agent (sodium pyrophosphate) for iron (III) at a confluence point, and then merged downstream with a buffer solution (sodium acetate-acetic acid) for spectrophotometric detection by complex formation. The results for the analysis of various α-Fe2O3 sensor showed good reproducibility. It has also proved that the FIA system allows rapid and simple analysis; only 2min. is required for analytical measurement after sample injection and no complicated procedure is involved.
