A1 COPPER IN WATER BY ELECTROTHERMAL AAS Last Revised: June 2014
1. PURPOSE This exercise introduces the basic principles of operation of an electrothermal AAS instrument. 2. REAGENTS & EQUIPMENT 2.1 Varian EAAS 2.2 1000 mg/L Cu 2.3 1% Aristar nitric acid (for rinsing) 2.4 0.1% Aristar nitric acid (for solution preparation) 3. PROCEDURE 3A. Prework 3.1 From the Copper standard conditions available for this exercise from the Practical Exercises webpage, find the following:  the amount of Cu that gives an absorbance of 0.2  temperature program for Cu 3.2
3.3
Determine the concentration of three suitable calibration standards. Work out an appropriate dilution scheme to prepare the standards from 1000 mg/L Cu. Check this with your teacher before proceeding. 3B. Standard and sample preparation 3.4 Rinse all glassware with the 1% nitric acid. 3.5 Prepare the standards. All solutions below 1 mg/L must be made up in the 0.1% Aristar nitric acid. 3.6 Obtain samples of tap water and Throsby creek water. 3C. Instrument setup 3.7 Observe the startup procedure. Record the steps involved. You will be expected to perform them in a later exercise using this instrument. 3.8 Assist in the programming of the software. The key parts are:  analytical method (calibration standards for this exercise)  autosampler volumes (10 uL of sample/standard and 10 uL of blank)  temperature program  autosampler positions 3.9 Half‐fill the plastic sample containers with the blank (0.1% nitric), standards and samples and place in the positions in the autosampler, as directed by your teacher. 3D. Measuring the solutions 3.10 Begin the run sequence as shown. 3.11 While it is running, calculate the expected absorbance for the bottom standard. 3.12 Check the absorbance of the bottom standard against your expected value. If it is more than 0.1 different to expected, alert your teacher. 3.13 If necessary, prepare and dilutions (0.1% nitric) to achieve suitable absorbances. CALCULATIONS 
check the replicate data for obviously bad values, and delete these 
calculate the average absorbance for each solution 
plot a calibration graph 
determine the concentration for each sample of suitable absorbance from the graph 
apply the dilution factor if needed to determine the level of copper in the tap and creek water 
calculate the average characteristic mass using each of the three standards 
compare this with the expected value DISCUSSION 
compare the tap water result to the Australian Drinking Water standard 
explain why standard addition was not necessary in this analysis 
describe the changes to the heating cycle if the analysis was copper in wine QUESTIONS 1.
Give THREE reasons why electrothermal atomisation gives greater sensitivity than flame atomisation. 2.
(a) Why is the glassware washed in nitric acid? (b) Why are the low concentration solutions made up in nitric acid? (c) Why is normal AR grade nitric acid not used? 3.
(a) What is the appropriate range of total liquid volume per analysis? (b) What is the problem with lower and higher total volumes? (c) Why is the total volume kept constant for all solutions? A1 p2 A1. COPPER IN WATER BY EAAS
RESULTS SHEET Standard preparation method Absorbances Conditions Abs. Blank Std 1 Std 2 Std 3 Tap water Dilution (if needed) Creek water Dilution (if needed)