Explore resources, experiments, and teaching materials shared by the analytical sciences community.
The overall variance in an analysis, s2, is the sum of the variances arising from the method, (smeth)2, and the variance due to sampling, (ssamp)2. s2 = (smeth)2 + (ssamp)2 The blue curve in […]
When a manufacturer lists a chemical as ACS Reagent Grade, they must demonstrate that it conforms to specifications set by the American Chemical Society (ACS). For example, the ACS specifications for NaBr […]
The data set available here contains masses for 100 circulating U. S. pennies. All pennies in these data sets were minted between 1962 and 1981, a period during which a penny’s composition […]
The effect of a inert salt on a reaction’s equilibrium position is shown by the solutions in these two beakers. The beaker on the left contains equal volumes of 1.0 mM FeCl3 […]
Scale showing the pH value for representative solutions. Milk of Magnesia is a saturated solution of Mg(OH)2.
The figure below shows how the masses of Ca2+ and CaCO3 change as a function of time during the precipitation of CaCO3. The dashed line indicates when the reaction reaches equilibrium. Prior […]
The three plots below show the residual error in the signal, Sstd, as a function of the concentration of analyte, Cstd for an unweighted straight-line regression model. The red line in each […]
The figure here illustrates the basis of a linear regression analysis. The points in blue are the experimental data and the points in red are the predicted values from the regression equation. […]
One approach for preparing standard additions is to spike equal volumes of the sample with different volumes of a standard and diluting each to the same final volume. An alternative form of […]
Sometimes the solution matrix in which the analyte resides affects the relationship between the signal and the analyte’s concentration, as shown below. We call this a matrix effect. When matrix effects are […]
When using a single-point standardization, we must assume that there is a linear relationship between the signal and the analyte’s concentration. When this is not true, which often is the case at […]
The figure below shows the probability of type 1 and type 2 errors for the IUPAC detection limit. (a) The normal distribution curve for the method blank, with a signal for the […]
