Industry Sectors Traditionally, monographs call for assaying this chemical using an EDTA titration for calcium, and a number of other wet chemistry techniques for impurities. Testing calcium carbonate by X-Ray Fluorescence (XRF) is an excellent QC test method. Â XRF is an elemental analysis technique with unique capabilities including (1) highly accurate determinations for % lev el elements and (2) a broad elemental survey of the sample composition without standards. The XRF method is simple, fast, and inex pensive compared to monograph methods. You should consider it an additional test procedure for your raw material.
Quantitative XRF of CaCO3
We have developed a quantitative XRF analysis technique for the common % level components found in most calcium carbonate samples. The sample (~3 g) is calcined in a muffle furnace at 1000-1100 Cº, then the residue is fused with lithium tetrabor ate to form a clear glass bead .
The sample is then analyzed at fixed angles for selected elements. Quality Control includes the analysis of a NIST Standard Reference Material (SRM). A typical report is shown below.
The table below is an example report for a calcium carbonate derived from coral. The Loss on Ignition is a measure of both carbon dioxide and any other volatile component such as moisture or organic binders which have been added. The Mass Balance is a quality control parameter that indicates that the test has accounted for all components. This same test can be applied to calcium oxide and hydroxide samples.
In addition to these selected elements, the fused sample can be scanned for other, unsuspected impurities using an SQX procedure.
Sample: Coral Calcium
Rigaku ZSX100e XRF
| Material | Weight Percent | Detection Limit |
| CaO | 27.95 | |
| Na2O | 0.22 | 0.02 |
| MgO | 14.86 | 0.02 |
| SiO2 | 0.42 | 0.2 |
| P2O5 | 0.073 | 0.004 |
| K2O | ND | 0.04 |
| TiO2 | 0.005 | 0.004 |
| MnO | 0.005 | 0.004 |
| Fe2O3 | ND | 0.1 |
| SrO | 0.17 | 0.02 |
| SO3 | 0.22 |
0.02 |
Loss on Ignition = 55.79
Mass Balance = 99.80
Date Analyzed: 12-05-03
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Quality Control Summary
Sample: NIST SRM 1A
| Certified Value | Observed | Difference | Acceptable Difference | |
| CaO | 41.32 | 41.19 | -0.13 | 1.00 |
| Na2O | 0.39 | 0.39 | -0.00 | 0.08 |
| MgO | 2.19 | 2.11 | -0.08 | 0.30 |
| SiO2 | 14.11 | 13.79 | -0.32 | 0.40 |
| P2O5 | 0.15 | 0.15 | -0.00 | 0.01 |
| K2O | 0.71 | 0.69 | -0.02 | 0.03 |
| TiO2 | 0.16 | 0.16 | -0.00 | 0.01 |
| MnO | 0.038 | 0.04 | 0.00 | 0.005 |
| Fe2O3 | 1.63 | 1.66 | 0.03 | 0.04 |
| SrO | 0.12 | 0.12 | -0.00 | 0.01 |
| SO3 | 0.66 | 0.63 | -0.03 | 0.06 |
| Loss on Ignition | 34.55 | 34.53 | -0.02 | 0.50 |
| Mass Balance | 100.20 | 99.61 | -0.58 | 1.50 |
Date Analyzed: 12-05-03
