X-RAY FLUORESCENCE: INSTRUMENTAL & MATRIX FACTORS X2 Last Revised: August 2014
1. PURPOSE This exercise examines instrumental and matrix factors in X‐ray fluorescence spectroscopy. 2. REAGENTS & EQUIPMENT 2.1 Mixed oxide sample (contains equal amounts of oxides of Si, Ca, Ti, Fe, Cu & As) 2.2 Copper‐containing materials of known composition: a. copper foil (one piece cut to fit the sample holder, plus small pieces) b. copper turnings c. copper powder d. copper sulphate pentahydrate (large crystals) e. 20c coin 3. PROCEDURE You are required to analyse a suitable sample (or set of samples) and instrument settings (or range of settings) to answer the following questions. All runs to be done using Manual Control with a measure time of 20 seconds. 3.1 How do the instrumental settings – voltage, current and filter – affect the spectrum? Sample Mixed oxide Run Voltage (kV) Current (uA) Filter 1 30 100 none 2 30 10 none 3 10 10 none 4 30 10 5 30 10 Both the peak intensities and spectrum appearance are important here, so print or screen capture each spectrum. Choose a suitable combination of voltage, current and filter to analyse a range of copper‐containing samples, which will be used to answer Q3.2‐3.5. Voltage Current Filter Record the Cu K intensity only (peak top minus background). 3.2 How does sample size affect the peak intensity? Samples: 
a piece of copper foil that is the full size of the sample holder 
enough small pieces of copper foil to cover the sample cup surface a single small piece (approx. 5 x 5 mm) located in the centre of the sample cup 
3.3 Does sample position affect intensity? Samples: 
the same small piece of copper foil located at the edge of the sample holder (in a plastic cup) 3.4 Does the physical form of the sample affect the spectrum? Samples: 
copper turnings 
copper powder 
copper sulphate (large crystals) 
copper sulphate (ground by mortar & pestle) 3.5 How different is analyte response in different matrices? Samples: 
20c coin 
mixed oxide (if you didn’t record the Cu peak intensity in 3.1 under these conditions) 4. REPORT Calculations 
calculate the %Cu in CuSO4.5H2O and the mixed oxide 
calculate the intensity/%Cu ratio for: - copper powder - CuSO4 powder - mixed oxide - 20c coin (see AIT15 for %Cu) X2 p2 Discussion 
for each of the variations in 3.1‐5, describe and explain the effect on the spectrum: - voltage (3.1 runs 1 & 3) - current (3.1 runs 1 & 2) - filter (3.1 runs 2, 4 & 5) - size (results 1‐3) - position (3 & 4) - physical form: pure copper (1, 5 & 6) & copper sulphate (7 & 8) - matrix (using intensity:%Cu ratios): powder (6, 8 & 10) & metal (1 & 9) 
explain how you would deal with the variations observed in 3.2‐3.5 Questions 1. Based on your results, what would be the best instrument settings (voltage, current, filter) for a sample of iron ore, which is known to contain some silica? 3. Give TWO advantages of XRF compared to ICP emission for the analysis of alloying elements in steel. 4. Explain why XRF would be an ideal technique for checking for the presence of lead in roadside fallout. X2 p3 X2. X‐RAY FLUORESCENCE RESULTS SHEET Sample Variation Cu K Intensity Result Full size 1 Small pieces 2 Single piece ‐ centre 3 Single piece ‐ edge 4 Copper turnings 5 Copper powder 6 Crystals 7 Powder 8 20c coin 9 Mixed oxide 10 Copper foil CuSO4