2. Steel is a construction material widely used for its durability under environmental conditions and its structural rigidity. This material has a main composition of iron, carbon (in variable proportions) and other metals (eg, Mn, Co, Cr, Ni among others) in different proportions. The typical analysis method for the determination of manganese consists of taking a sample of 1,0000 g of steel, oxidizing it through acid digestion with HMnO4 (permanganic acid) and subsequently diluting it in a 500 mL flask up to the volume mark, in order to measure its absorbance at a wavelength of 540 nm. In a routine analysis, three calibration curves were prepared using three different reference materials, and the following was observed: a) If the calibration curve is constructed from KMnO4 standard solutions, it turns out to be a straight line that passes through the origin. b) If the calibration curve is prepared from a steel standard sample containing various amounts of Cr, V, Mo and Mn, a straight line also results, but it does not pass through the origin. In reference to the previous information, investigate and answer the following: i) What is the most probable cause or origin why there is a significant difference between the intercept calculated for both methods? ii) Do you consider that there will be a significant difference between the analytical sensitivity, selectivity or detection and quantification limits for both cases? iii) What calibration method could be used to correct these differences, if present?
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