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Testing Calcium Carbonate by X-Ray Fluoresence (XRF)

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.  XRF is an elemental analysis technique with unique capabilities including (1) highly accurate determinations for % level elements and (2) a broad elemental survey of the sample composition without standards.  The XRF method is simple, fast, and inexpensive compared to monograph methods.  You should consider it an additional test procedure for your raw material.

For more information:

Testing Calcium Carbonate

How does XRF work?

Comparison of XRF-SQX and ICPMS Metals Screen

 


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 1000-1100oC, then the residue is fused with lithium tetraborate 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.  See the additional links above.

For a quotation...

 Example Report

Sample:

Coral Calcium

     
         
 

Weight Percent

Detection Limit

   

CaO

27.95

     

Na2O

0.22

0.02

   

MgO

14.86

0.02

   

Al2O3

0.04

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

     
         
         
 

Quality Control Summary

   
         

Sample:

NIST SRM 1A

     
       

Acceptable

 

Certified Value

Observed

Difference

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

Al2O3

4.16

4.15

-0.00

0.11

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

   

Rigaku ZSX100e XRF

Rigaku ZSX100e XRF

 

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