Problem 1
Make a list of good laboratory practices for the lab that accompanies this course, or another lab if this course does not have an associated laboratory. Explain the rationale for each item on your list.
Problem 2
Write directives outlining good measurement practices for (a) a buret, for (b) a pH meter, and for (c) a spectrophotometer.
Problem 4
The following data were obtained for the duplicate analysis of a 5.00 ppm \(\mathrm{NO}_{3}^{-}\) standard. \begin{tabular}{ccc} sample & \(X_{1}(\mathrm{ppm})\) & \(X_{2}(\mathrm{ppm})\) \\ \hline 1 & 5.02 & 4.90 \\ 2 & 5.10 & 5.18 \\ 3 & 5.07 & 4.95 \end{tabular} \begin{tabular}{ccc} sample & \(X_{1}(\mathrm{ppm})\) & \(X_{2}(\mathrm{ppm})\) \\ \hline 4 & 4.96 & 5.01 \\ 5 & 4.88 & 4.98 \\ 6 & 5.04 & 4.97 \end{tabular} Calculate the standard deviation for these duplicate samples. If the maximum limit for the relative standard deviation is \(1.5 \%,\) are these results acceptable?
Problem 5
Gonzalez and colleagues developed a voltammetric method for the determination of tert-butylhydroxyanisole (BHA) in chewing gum. Analysis of a commercial chewing gum gave a result of \(0.20 \mathrm{mg} / \mathrm{g} .\) To evaluate the accuracy of this results, the authors performed five spike recoveries, adding an amount of BHA equivalent to \(0.135 \mathrm{mg} / \mathrm{g}\) to each sample. The experimentally determined concentrations of BHA in these samples were reported as \(0.342,0.340,0.340,0.324,\) and \(0.322 \mathrm{mg} / \mathrm{g} .\) Determine the percent recovery for each sample and the mean percent recovery.
Problem 7
The following data were obtained for the repetitive analysis of a stable standard. \begin{tabular}{cccccc} sample & \(X_{i}(\mathrm{ppm})\) & sample & \(X_{i}(\mathrm{ppm})\) & sample & \(X_{i}(\mathrm{ppm})\) \\ \hline 1 & 35.1 & 10 & 35.0 & 18 & 36.4 \\ 2 & 33.2 & 11 & 31.4 & 19 & 32.1 \\ 3 & 33.7 & 12 & 35.6 & 20 & 38.2 \\ 4 & 35.9 & 13 & 30.2 & 21 & 33.1 \\ 5 & 33.5 & 14 & 32.7 & 22 & 34.9 \\ 6 & 34.5 & 15 & 31.1 & 23 & 36.2 \\ 7 & 34.4 & 16 & 34.8 & 24 & 34.0 \\ 8 & 34.3 & 17 & 34.3 & 25 & 33.8 \\ 9 & 31.8 & & & & \end{tabular} Construct a property control chart for these data and evaluate the state of statistical control.
