Laboratory Exercise Demonstrating Systematic Error in Instrumental Analyses: Aberrant Atomic Absorption Spectroscopy of Cadmium

Presenter Information

Derek Whitaker, Minnesota State University, Mankato

Location

CSU 253/4/5

Start Date

4-4-2011 11:00 AM

End Date

4-4-2011 12:30 PM

Student's Major

Chemistry and Geology

Student's College

Science, Engineering and Technology

Mentor's Name

Trenton Vorlicek

Mentor's Department

Chemistry and Geology

Mentor's College

Science, Engineering and Technology

Description

Commercial stock solutions are routinely used to prepare calibration standards for atomic absorption spectroscopy (AAS). Unfortunately, these solutions contain high concentrations of acid (e.g., 2-6 % HNO3) which may cause interferences in the AAS signal. Using calibration standards prepared from commercial stock solutions, 200 µM Cd (as Cd(NO3)2·4H20) test solutions were consistently quantified by air-acetylene flame AAS to contain ~135 µM Cd. Three sets of calibration standards, ranging from 0.5 to 1.5 ppm Cd, were prepared from two commercial 1000 ppm Cd solutions and a 1000 ppm Cd solution made from 3CdSO4·8H20. The 3CdSO4·8H20 standards produced a calibration curve with linear slope ~33% lower than the slopes of both sets of commercial standards. Using these results as a framework, a laboratory exercise appropriate for an Instrumental Analysis course is prepared. Students will design and perform experiments to identify and eliminate the systematic error in Cd AAS analyses.