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Association of Fertilizer andPhosphate Chemists 1
Analysis of Phosphate inFertilizer Concentrates andBlends Utilizing aSimultaneous ICP-OES
Sanford Siegel Art EspinosaCF Industries, Inc. IMC Phosphate
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Current AnalyticalMethodology
Molybdovanadate complex basedColorimetric determinations
Single sample analysis or Automated
Advantages Widely accepted
Robust
Acceptable accuracy, precision, anddynamic analytical range
Disadvantages
Dedicated instrumentation to P
Maintenance intensive and sensitive
Multiple modules subject to failure
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Why ICP-OES?
ICP-OES has assumed a multitasking
role in the Q.C./ Q.A. lab Major element determination
Minor element determination
Trace element determination
Process Studies
Environmental/ Geological Studies
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Most Labs have at least one instrument
Cost has dropped over the past ten years
ICP-OES 1993 $120,000 2003 $80,000
AutoAnalyzer 2003 $40,000+
Operating costs are comparable:
Argon vs. Reagents and expendables
Why ICP-OES ? (continued)
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Association of Fertilizer andPhosphate Chemists 5
The Challenge
Unlike phosphate rock, phosphatefertilizer concentrates analyzed by ICPhave variability in analysis.
The Cause Easily ionized elements (EIEs) create
ionization interference in the plasma. The
observed effect is signal suppression. Major source of interference is Ca
Minor sources of interference are Mg, Na, K
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The Solution
Use all commonly accepted tools forprecision analysis:
Matrix matching
Internal standard
Robust Plasma Conditions (Brenner,Mermet)
Plus Lithium Nitrate as ionization buffer
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Matrix Matching
Creates a similar environment fordetermination
Background noise levels
Viscosity effects
Droplet size
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Internal Standard
Helps compensate for
variability due to:
Background noise levels Viscosity effects
Droplet size
Scandium, Yttrium, or Beryllium?
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Lithium Nitrateas ionization buffer
Levels out variability due to EIEs toallow precise determinations.
Lithium, Cesium, or Potassium?
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Participants in theMethod Validation
Cargill Nutrition Products
IMC Phosphate
CF Industries
J.R. Simplot PCS Aurora
Ottawa Lab (Carling) CFIA
State of Fl. Dept. of Agriculture
PerkinElmer Leeman Labs
Spectro Analytical
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Of the 10 Labs receiving samples
8 labs responded with results
2 labs failed to return analysis 1 lab was statistically out of control
based on submitted colorimetricdeterminations
Participants in theMethod Validation
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Samples Submitted forAnalysis to Participants
Diammonium Phosphate 18-46-0
Diammonium Phosphate 18-46-0
Monoammonium Phosphate 10-50-0
Fertilizer Blend A 8-16-24
Fertilizer Blend B 10-20-20
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All Participating Lab Results
Sample Collaborative
Average
S.D. ICAP
Average
S.D.
DAP A 45.81 0.23 45.84 0.14
DAP B 46.28 0.10 46.31 0.43
MAP 49.89 0.34 50.00 0.29
10-20-20 19.12 0.13 19.16 0.16
8-16-24 16.02 0.09 16.07 0.27
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Fertilizer LabsResults
(4 respondents)
Sample Collaborative
Average
S.D. TechniconAverage
S.D. ICAP
Average
S.D.
DAP A 45.81 0.23 45.81 0.39 45.83 0.12
DAP B 46.28 0.10 46.36 0.04 46.30 0.01
MAP 49.89 0.34 49.71 0.07 49.85 0.19
10-20-20 19.12 0.13 19.07 0.04 19.09 0.25
8-16-24 16.02 0.09 15.93 0.06 16.10 0.30
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Instrumentation Labs
Results(3 respondents)
Sample Collaborative
Average
S.D. ICAP
Average
S.D.
DAP A 45.81 0.23 46.19 0.50
DAP B 46.28 0.10 46.37 0.86
MAP 49.89 0.34 50.70 0.60
10-20-20 19.12 0.13 19.14 0.09
8-16-24 16.02 0.09 16.06 0.27
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Comparison of Central Tendency of LabResults on Fertilizer Concentrates withCollaborative Results
45.00
46.00
47.00
48.00
49.00
50.00
51.00
45.00
46.00
47.00
48.00
49.00
50.00
51.00
Collaborative Results
Lab
Results
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Comparison of Central Tendency of LabResults on Blended Fertilizers withCollaborative Results
15.50
16.00
16.50
17.00
17.50
18.00
18.50
19.00
19.50
15.50
16.00
16.50
17.00
17.50
18.00
18.50
19.00
19.50
collaborative results
lab
results
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Conclusions fromValidation Study
Lithium buffered ICP-OES is comparableto colorimetric analysis for
Central Tendency of results Precision of results
Major source of dispersion is lack ofexperience
Fertilizer lab versus Instrumentation lab
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Recommendation to participants,AFPC and AOAC
Review findings with participants
Survey participants for user suggestions onimproving the method
Submit findings to AFPC and AOAC
Recommend that the method be accepted forfertilizer concentrates and dry blends of N-P-Kfertilizers