In this experiment, the method of standard additions is demonstrated as an analytical tool. The method is a procedure for the quantitative analysis of a species without the generation of a typical calibration curve. Standard Addition analysis is accomplished by measuring spectroscopic intensity before and after the addition of precise aliquots of a known standard solution of the analyte.
This experiment studies non-fluorescent species by reacting them in such a way as to form a fluorescent complex. This approach is commonly used in the investigation of metal ions. Aluminum ions (Al3+) will be determined by forming a complex with 8-hydroxyquinoline (8HQ). The Al3+ is precipitated by 8HQ from aqueous solution and then is extracted into chloroform; the fluorescence of the chloroform solution is measured and related to the concentration of the original Al3+ solution. Sensitivity in the part-per-million (ppm or μg/mL) range is expected for this experiment.
The reaction is
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The amount of aluminum in each sample during this experiment is calculated as follows:
| Blank | 0 | ||
| Unk + 0 mL STD | VUNK(CUNK) = 25 mL(CUNK) | ||
| Unk + 1 mL STD | VUNK(CUNK) + VSTD(CSTD) = 25 mL(CUNK) + 1 mL(1 μg/mL) | ||
| Unk + 2 mL STD | VUNK(CUNK) + VSTD(CSTD) = 25 mL(CUNK) + 2 mL(1 μg/mL) | ||
| Unk + 3 mL STD | VUNK(CUNK) + VSTD(CSTD) = 25 mL(CUNK) + 3 mL(1 μg/mL) | ||
| Unk + 4 mL STD | VUNK(CUNK) + VSTD(CSTD) = 25 mL(CUNK) + 4 mL(1 μg/mL) | ||