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APPLICATION NOTE

Western Phosphate Rock – NIST 694

SUMMARY

The application note summarizes the digestion of NIST 694, a Western Phosphate Rock Certified Reference Material using ColdBlock Digestion CB15S Technology.

Instrument:

ColdBlock CB15S sample digester technology, chiller, ICP-OES

Published:September 2022
Digestion Time:25 Minutes
Acid Used:Aqua Regia & Tetrafluoroboric Acid
Average ColdBlock Recovery vs. CRM:
  • 107% Calcium
  • 101% Phosphorus
  • 103% Aluminum

METHODOLOGY

  1. Chiller temperature was set to 5 ̊C
  2. 0.5g of each sample was weighed and placed into a ColdBlock Digestion vessel
  3. 20ml Aqua Regia & 3mL Tetrafluoroboric acid (HBF4) was added
  4. Sample was digested at 100% power for 5 minutes then power was reduced to 70% and digestion continued for 20 minutes
  5. Sample was cooled and bulked to 50mL using 2% HNO3 v/v

DISCUSSION

  • After 25 minutes the sample was brown, and a minor amount of solid material remains
  • The use of Hydrofluoric acid was investigated and resulted in full recovery of Consequently, the formation of insoluble Calcium Fluoride (CaF2) impacted recoveries of Calcium & Aluminum.
  • To address the insoluble CaF2, HBF4 was used to fully recover all the Calcium and Aluminum, but negatively impacted Silicon recoveries

NIST 694 is a Western Phosphate Rock -standard reference material by the National Institute of Standards & Technology. It is intended for use in validating analytical methods.

Results

NIST 694 – Western Phosphate Rock

 

Method:

 

0.5g

20mL Aqua Regia + 3mL HBF4. Digest at 100% for 5 minutes then reduce power to 70% and digest again for 20 minutes.

Constituent

Certified Value of Constituents wt.%

Element

Reference Value (ppm)

ColdBlock Average (ppm)

Stdev

%RSD

%

Recovery

Al2O3

1.8

Al

9525

9856

217.6

2%

103%

CaO

43.6

Ca

311609

332687

5759.5

2%

107%

CdO

0.015

Cd

131

145

1.3

1%

110%

Cr2O3*

0.11

Cr

684

794

14.3

2%

116%

Fe2O3

0.79

Fe

5525

5434

268.6

5%

98%

K2O

0.51

K

4234

4479

372.6

8%

106%

MgO

0.33

Mg

1991

2339

127.6

5%

117%

MnO

0.0116

Mn

90

97

2.5

3%

108%

Na2O

0.86

Na

6380

6636

651.6

10%

104%

P2O5

30.2

P

131799

133460

2790.4

2%

101%

V2O5

0.31

V

1737

1681

52.2

3%

97%

ZnO*

0.19

Zn

1526

1705

95

6%

112%

SiO2

11.2

Si

52360

13872

916.4

7%

26%

Click here to download the Application Note in PDF format.

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4551 Zimmerman Ave
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info@coldblock.ca.