analysis of phosphate in fertilizer concentrates and blends

8/4/2019 Analysis of Phosphate in Fertilizer Concentrates and Blends

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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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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)


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)


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

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49.00

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45.00

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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

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15.50

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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

analysis of phosphate in fertilizer concentrates and blends

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