Question 7.9: A river is suspected to be polluted with toxic organic waste...
A river is suspected to be polluted with toxic organic waste that may be having adverse effects on the nearby population. This hypothesis is verified by collecting 200 samples of water at different depths along the river for analysis. The method used has a limit of detection of 0.7 ppm and a limit of quantification of 2.1 ppm. The effects of the organic waste are felt at concentrations above 3 ppm. The concentration of waste obtained with the chosen method is 2.7 ppm.
(a) Complete the following table.
(b) Can the socio-economic problem addressed be correctly solved?
(c) Does the analytical method require any corrective actions?
| Socio-economic problem | |
| Analytical problem | |
| Object | |
| Sample/aliquot | |
| Analyte(s) | |
| Limit of detection (C_{LOD}) | |
| Limit of quantification (C_{LOQ}) | |
| Legal limit (C_{LL}) | |
| Result (C_{obtained}) |
(a)
| Socio-economic problem | Checking whether the river is contaminated with toxic organic waste |
| Analytical problem | Detecting and determining organic compounds with potentially detrimental effects on the population |
| Object | The river |
| Sample/aliquot | Water from the river as collected at a variable depth at different points along its course |
| Analyte(s) | Toxic organic compounds |
| Limit of detection (C_{LOD}) | 0.7 ppm |
| Limit of quantification (C_{LOQ}) | 2.1 ppm |
| Legal limit (C_{LL}) | 3 ppm |
| Result (C_{obtained}) | (2.7 – 0.1) ppm |
(b)
Yes. The socio-economic problem can be solved because the analytical process allows the presence of toxic organic compounds to be confirmed and their concentration, which is close to the legally accepted limit, determined.
(c)
No corrective actions are needed because the limits of detection (C_{LOD}) and quantification (C_{LOQ}) are valid for detecting and quantifying the analytes—both are lower than the legal limit (C_{LL}).