Following are some suggested activities to assure technical competence in the use of AA for elemental analysis. This is the most rigorous of the competencies listed in this section. While most analyses using AA are single element, there are several instruments that offer sequential flame or simultaneous electrothermal analytical capabilities, and the technician assigned to such instruments must understand both the advantages and the limitations of multielement analysis. The former includes savings in time and cost, while the latter involves the use of compromise analytical conditions.

Disassemble, clean, and reassemble a nebulizer and mixing chamber for flame AAS; replace a graphite tube and end cones for electrothermal AAS.

A fundamental understanding of the AA instrumentation is only of value if the technican can apply that knowledge in maintaining and troubleshooting instrumentation. Since the atomic vapor cell (flame and furnace) are the most likely sources of trouble in an analysis, as well as requiring the most maintenance, it is only proper that the technician should be able to do rudimentary maintenance on these devices.

Identify and explain available methods for sample preparation for (a) biological, (b) botanical, (c) metals, (d) geological materials for analysis by AAS under conditions of ultratrace, trace, and high-level analyte concentrations.

Sample preparation is a fundamental part of the AA measurement process and cannot logically be separated from a discussion of AA. While sample preparation for AA will certainly overlap methods used for other solution spectrometric methods, the technician who understands AA but does not properly understand preparation methods will be of little value to their company. Even if the technician does not actually do the preparation, since instrument operation and sample preparation are separated in some company organizations, an understanding of preparation methods must be maintained since good AA results depend on a synergy of sample preparation and instrumental analysis.

This competency requires that the technician be familiar with the intricacies of sample preparation methods for specific analytes to be measured by atomic absorption. Considerations include analyte volatility in specific acid media, complete destruction of organic matrix, and dissolution of difficult metal and geological matrices. Methods of sample preparation will include acid dissolution by open and closed systems, including microwave; dry ashing; and fusion. The technician should know, or should know where to look to find out, which methods are compatible with the proposed AA method. For example, the preparation of geological samples using a lithium metaborate fusion would be useless when a furnace atomizer is employed, since the fusion flux rapidly attacks the furnace tube.

Use a variety of atomic absorption spectrometers to analyze known and unknown samples by applying the following procedures:            

• take appropriate samples
• prepare samples, controls and blanks     
• dilute samples      
• choose proper atomizer and atomization conditions      
• identify and perform different methods of calibration including calibration curve, bracketing, and standard addition      
• optimize instrumental parameters           
• determine the concentration of elemental components           
• repeat the analysis      
• calculate the results including appropriate statistics to express the uncertainty of measurement

This competency represents the first of the two most critical parts of the technician's duties. Excellence in this area means that the technician is able to carry out an analysis from sample to results using proper procedures and applying knowledge from previously listed competencies.

Troubleshoot an AAS instrument that is not performing optimally.

This competency reflects the second of the two most critical parts of the technician's duties. In part 07c, the technician performed normal, well-defined analytical operations. Now, the technician must deal with a poorly operating instrument, diagnosing the problems and developing solutions. Problems may include a misaligned burner slot, clogged nebulizer, improperly filled drain trap, misaligned lamp, improper lamp current, improper monochromator spectral bandpass, improper flame stoichiometry, and poorly adjusted nebulizer and impact bead, as well as other more insidious problems. The technician should be able to identify which instrument component(s) is causing the measurement problem and then solve the problem.