14. An estimate of the uncertainty for the concentration of an unknown sample can be determined based on the uncertainty in the calibration data set and the unknown sample analysis. The uncertainty (Sx) value is unitless when using the internal standard method of calibration. The uncertainty needs to be expressed in terms of the concentration units used for the standards (i.e. ppm). Calculated the uncertainty value in terms of concentration (Sc) for the diluted AND undiluted sample based on the following information. Uncertainty (Sx; unitless) based on the calibration data set and the unknown sample. Sx = 0.0152 Sample preparation: A whiskey sample is prepared for analysis by GC-FID using the internal standard method of calibration. A 20 mL sample is transferred using a volumetric pipet to a 50 mL volumetric flask. A volume of stock solution of the internal standard is added to the sample flask. The flask is diluted to volume. Concentration of the internal standard in the diluted unknown = 500 ppm. A. Sc(dilute) = 8 ppm, Sc(undilute) = 20 ppm B. Sc(dilute) = 7 ppm, Sc(undilute) = 19 ppm C. Sc(dilute) = 7.75 ppm, Sc(undilute) = 19.31 ppm D. Sc(dilute) = 8 ppm, Sc(undilute) = 30 ppm