Aas Lab Report

Laura Paez

Lab 4: AAS; Creating a Standard Curve Two Different Ways

Chemistry 4440

Harshani Rathnaweera

September 22, 2014

ABSTRACT

In this experiment the Varian 220 AAS instrument was used as an introduction to understanding the Atomic Absorption Spectroscopy (AAS) instrument and how it works. The experiment consisted of making standard solutions that contained manganese (Mn) and 5% concentrated nitric acid (HNO3) and measuring them for absorptions in order to use that with a calibration plot and find the concentrations of two unknowns. Two unknowns were also measured along with a CAL ZERO used as the blank. The standards were diluted to fit within the Mn linear range of 2 to 30 ppm in atomic absorption spectroscopy. These four standards,

This lab also tested basic chemistry techniques and calculations. The experiment consisted of making standard solutions that contained manganese (Mn) and 5% concentrated nitric acid (HNO3) that were measured for absorption to find their concentrations. Two unknowns were also measured and later their concentrations were calculated as well. The metal element of interest, in this case Mn, is measured in atomic absorption as how much light at a specific wavelength is absorbed when it goes through the atoms in the sample. The AAS instrument is highly sensitive, it can read parts per million (ppm) concentration but also parts per trillion (ppt) concentrations. It also has high selectivity since it only measures for one specific element at a time. This is because other elements usually have different wavelengths of absorption, which means that they probably will not be absorbed at the chosen wavelength of the analyte being measured.

Instrumental Theory and

Specifically, what would you do if your unknown sample is out of the linear range of your calibration curve (Varian's software uses the label: UNCAL or OVER)? If the unknown sample was out of the linear range of calibration, a dilution of the unknown sample would have to be prepared. Depending on how high out the range the sample reading was, the dilution would have to be made. After this the unknown would have to be measured again to see if the dilution of the sample made it fit in the linear range or not. If once again the sample was outside the linear range of calibration, then another dilution would have to be performed. The sample, then once again would have to be measured to make sure that the dilution worked and the sample is within the linear range.

4. Using your instrumental textbook, describe and explain the following two different techniques for determining and correcting chemical interferences.

Spiking

Spiking is simply adding a known amount of the analyte is added to an aliquot of the desired analyte. This is done to see if the instrument has any non-spectral interferences. So if the amount of analyte that was added can be measured close to the known and expected result, it means that there are no non-spectral