Measurement precision and 1/f noise in analytical instruments

The recently promulgated uncertainty theory of instrumental analyses was used to minimize the relative standard deviation of measurements. Naphthalene, acenaphthene, pyrene and perylene in HPLC were used as illustrations. For a Gaussian model peak with a width (S.D., sigma) of fifteen data points, the optimum integration domain was about +/-6 data points (+/-0.4 sigma) around the peak centre on the HPLC baseline examined. Two commonly used integration modes were examined: horizontal zero line and oblique zero line. The precision was almost the same for both modes in the HPLC analysis. The signal shape at the limit of detection was also shown for the optimum integration domain. The error accompanying the use of the uncertainty theory was evaluated using a Monte Carlo simulation. The practical applicability and limitations of the theory are discussed.