a) An analytical chemist is determining the level of fuel contamination in ground water samples from a remediated gas station site where new condos are proposed to be constructed. An external calibration curve of peak area (units: mVs) for the analysis of toluene (ng mL-1) from the ground water samples by GC-FID yields a linear response with the equation: y = (764201450)x + (562115) i. What is the toluene concentration in ng mL-1 for a sample analyzed four times with a peak area of 15708(650) mVs? Can you approximate the uncertainty in the concentration? ii. What is the calibration sensitivity of this method? iii. What is the analytical sensitivity for the analyzed sample? iv. What is the relative standard deviation of the signal in the sample? v. If the analyst measures 20 replicates of a reagent blank, which yields a toluene peak area of 56075 mVs, what is the method limit of detection in ng mL-1? b) Describe an example of a type of analytical error corrected for in the analysis of a sample by using: i. A reagent blank ii. An internal standard