Western Phosphate Rock - NIST 694 - ColdBlock Technologies

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

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METHODOLOGY

Chiller temperature was set to 5 ̊C
0.5g of each sample was weighed and placed into a ColdBlock Digestion vessel
20ml Aqua Regia & 3mL Tetrafluoroboric acid (HBF4) was added
Sample was digested at 100% power for 5 minutes then power was reduced to 70% and digestion continued for 20 minutes
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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APPLICATION NOTE