An analytical chemist was using atomic absorption spectroscopy (AAS) to determine the manganese concentration in a sample - HSC - SSCE Chemistry - Question 4 - 2022 - Paper 1

To determine the manganese concentration in the sample using atomic absorption spectroscopy (AAS), it is necessary to ensure that the AAS lamp emits light at the wavelengths that correspond to the absorbance lines of manganese.

From the provided absorbance diagram, manganese shows significant absorbance at specific wavelengths typically closer to 380 nm. The lamp that should be selected is one that emits light at or near these wavelengths to ensure optimal absorption by manganese in the sample.

Upon analyzing the emission spectra of the four AAS lamps:

• Lamp A has emission lines at wavelengths that do not match those of manganeses' absorbance peaks effectively.
• Lamp B similarly fails to cover the absorbance region sufficiently.
• Lamp C notably shows emission lines that coincide with the absorbance lines for manganese.
• Lamp D contains emission lines that do not align with manganese's absorbance effectively.

Thus, the most suitable choice is Lamp C, which has emission lines within the required range to accurately determine the manganese concentration.