Determination of the composition of sand and aluminosilicates using borate fusion for XRF analysis

Sand is mostly used as a raw material in the production of many industrial products such as glass and cement, while aluminosilicates are used in the building, refractory and catalyst industry. It is important to know the exact compound concentrations of these materials so they remain within the tolerances over time and ensure the constant quality of final products. By knowing the exact concentration of raw materials to use for the creation of final products, you avoid waste and save costs.

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Introduction

Sand is mostly used as a raw material in the production of many industrial products such as glass and cement, while aluminosilicates are used in the building, refractory and catalyst industry. It is important to know the exact compound concentrations of these materials so they remain within the tolerances over time and ensure the constant quality of final products. By knowing the exact concentration of raw materials to use for the creation of final products, you avoid waste and save costs.

The purpose of this project is to prove that sample preparation by borate fusion is the best technique to achieve the highest levels of precision and accuracy for this application. In order to do so, two Claisse® instruments were used (LeDoser™ and LeNeo® instruments) together with Claisse consumables (borate flux).

Challenge
Obtain very accurate and precise results for major elements in sand and aluminosilicate matrices.

Benefits
• Easy and fast sample preparation for XRF analysis   
• Precise and accurate results   
• High efficiency   
• Constant quality of final products   
• Financial gain.

Apparatus and Instrumental Conditions

A Fisher Scientific™ Isotemp™ programmable muffle furnace was used to ignite the samples. The sand and aluminosilicate samples were ignited for 1 hour at 950oC in a Pt/Au crucible.

An automatic Claisse LeDoser instrument was used to perform the weighing step with high precision prior to fusion. Its ratio mode allows a fast and accurate weighing to obtain the exact sample-to-flux ratio required by the user. Glass disks that are made according to a very precise sample-to-flux ratio provide highly repeatable sample preparation conditions, thus better analytical results.

An automatic Claisse LeNeo fusion instrument was used to create 40 mm lithium borate glass disks. Its resistance-based electric system, excellent insulation properties and preset fusion programs allow a uniform heating, thus providing repeatable fusion conditions as well as a perfect retention of volatile elements.

A PANalytical 4 kW MagiX PRO sequential WDXRF spectrometer with a 37 mm collimator mask was used to analyse the glass disks. 

Calibration Strategy and Selection of Control Sample

Four (4) CRMs were used for the calibration of the XRF application; three (3) from NIST (SRM 76a, SRM 78a and SRM 1413) and one (1) from the BAS (BCS 313/1). The calibration was made with two (2) replicates of each CRM. Table 1 demonstrates the concentration ranges covered in this method. It also gives the certified concentration (dry basis) of the control sample used to evaluate precision and accuracy. 

Table 1: Application Concentration Ranges and Control Sample Composition
CompoundsConcentration range (%)Control sample (%)
(BCS 348) (dry#)
SiO218.00-100.051.1
Al2O30.000-72.0031.6
Fe2O30.000-1.801.04
Na2O0.000-1.800.34
K2O0.000-4.002.23
CaO0.000-0.8000.17
MgO0.000-0.7500.3
TiO20.000-3.501.08
P2O50.000-1.500.071

#Certified Basis

Results

Nine (9) compounds were analysed as they were of importance in the sample type. The precision of the method is shown for CRMs BCS 313/1 and NIST 78a in Table 2. Each CRM was fused in five (5) replicates glass disks. The results are given in concentrations. We selected these samples since they cover the whole calibration range for Al2O3 and SiO2 (low and high concentrations).

Table 2: Precision of the Fusion Method with XRF Analysis
CompoundsBCS 313/1 (standard)NIST SRM 78a (standard)
Concentration (%)SD (%)Concentration (%)SD (%)
SiO299.780.0619.40.01
Al2O30.0360.00271.70.02
Fe2O30.0120.001
1.20.001
Na2O0.0030.001
0.0780.002
K2O0.005
0.0011.220.002
CaO0.0060.0010.110.001
MgO0.00130.0010.70.002
TiO20.0170.0013.22
0.003
P2O5NANA1.30.004

Table 3 shows accuracy and precision of the method for the control sample. The accuracy result is compared to the certified value for CRM BCS 348. Accuracy was obtained by subtracting the average value of five (5) glass disks from the certified value.

Table 3: Accuracy of the Fusion Method with XRF Analysis
SiO2Al2O3Fe2O3Na2OK2OCaOMgOTiO2P2O5
Glass disk(%)(%)(%)(%)(%)(%)(%)(%)(%)
BCS 348-151.1331.561.0430.3402.2310.168
0.3101.0870.073
BCS 348-251.1331.581.0430.3422.2310.1650.306
1.0810.072
BCS 348-351.0731.531.0440.3442.2230.1650.3051.0780.073
BCS 348-4
51.1431.561.0420.3412.2300.1650.304
1.0780.075
 348-551.0631.541.0420.3432.229
0.1650.3081.0830.074
Average (%)
51.1031.551.0430.3422.228
0.1650.307
1.0810.074
SD (%)0.040.020.0010.0020.0030.0010.0020.0040.001
RSD0.07%0.06%0.10%0.50%0.15%0.72%0.80%0.35%1.37%
*BCS 34851.131.61.040.342.230.170.31.080.071
Accuracy (%)0.00-0.050.0030.002-0.002-0.0050.0070.0010.003

*Certified Values

Conclusion

The project was successful. Table 2 and 3 indicate that sample preparation by borate fusion followed by XRF analysis is an effective method to analyse sand and aluminosilicate samples on a wide range of compositions. Overall, the method showed excellent precision and accuracy for the nine (9) compounds analysed. This project demonstrates that the use of LeDoser and LeNeo instruments greatly helps to properly prepare sand and aluminosilicate samples for the analysis with a XRF spectrometer.

Since it is fast, easy and efficient, borate fusion is an excellent alternative to other sample preparation techniques in the laboratory. Discover Claisse wide range of high-quality products and services that will save you money, time and effort in the preparation of your samples!

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