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New method for determination of total sulfur using high temperature combustion
Tyson RowlandElementar Americas Product Manager
Fertilizer Methods Forum February 2016
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Current method
AOAC Method 980.02
• Gravimetric technique using barium to precipitate sulfate and carbon disulfide to solubilize the elemental S
• Drawbacks: this can be labor intensive and require the handling of hazardous materials
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Proposal – Make a method for HTC
High temperature combustion
• Fast – single element analysis under 5 minutes
• Less chemicals and in most cases not hazardous materials
• Improve safety
• Multi-element analysis!
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Basic operating principle
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CH3(CH2)xCH3+ O2
+ contaminants
CO2 + H2O + NOx +SO2
Schematic 1: Infrared Detection
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Advantage: Sensitive (as low as a under 10 mg/kg)
Disadvantage: Matrix dependent
Schematic 2: Thermal Conductivity Detection
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Advantage: Multi-element analysis for simultaneous N analysis (run in conjunction with AOAC 993.13)
Disadvantage: Sensitivity (as low at 100 mg/kg, 0.01%), time (CNS)
Sample data
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H2O
N2
CO2
SO2
• Powerful, clear peak focusing and separation
• Area underneath peak corresponds to element content
Single-lab validation study
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Point of Study“Combustion analyzers without absorption/desorption chromatography were investigated by
the Office of the Indiana State Chemist (OISC) as an alternative to the gravimetric method. Matrix and concentration sensitivities posed several analytical challenges, especially when S determination for a wide range of fertilizer products or an unknown source was required. Burn rates, scrubber types, and the need for accelerants was a function of the fertilizer type. As a result, different scan shapes and areas were generated for different products, and the most accurate data were obtained when sample and calibration sources matched. For example, a pure ammonium sulfate [(NH4)2SO4] fertilizer source has a quick burn that requires no accelerant, whereas a blended fertilizer product containing potassium-magnesium sulfate (K2MgO8S2) and potassium chloride (KCl) is a slow burn that may require an accelerant and a halogen scrubber. Another requirement was the separation of samples into low and high S concentrations because low concentration required a longer cell length that could be overwhelmed by high concentration samples resulting in carryover for the subsequent samples. As a result, samples were presorted into categories based upon S source, S concentration, and matrix to best match the calibration material and concentration range. If the S source was unknown, the sample was pretested and the scan compared to scans from various fertilizer sources to determine the best calibration material and concentration. For a company or laboratory that knows the source and history of the product, presorting of samples presents no problem but can be a challenge for a laboratory testing largely unknown samples.
The objective of this work was to investigate an automated, matrix-independent method using less hazardous reagents than the current regulatory procedure that allows equally simple. determination in single species and complex blended fertilizer products.”
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SLV Overview
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Instrument: vario MACRO cube
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Sample preparation (solids)
sample formertin boats and tin foil cups
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Sample preparation (liquids)
capsule press
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Sample preparation (liquids)
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Sample preparation (liquids)
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Sample preparation (crucibles)
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Sample preparation (auto-loader)
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Recent Data – Liquid Fertilizers
Name Area [N] Area [S] % N % S Name Area [N] Area [S] % N % S
Sample 1 35289 25063 11.882 26.811 Sample 3 99 10504 0.044 11.158
Sample 1 36909 26239 11.897 26.853 Sample 3 108 10533 0.046 11.172
Sample 1 34296 24640 11.836 27.023 Sample 3 121 10541 0.051 11.127
Sample 1 40842 29128 11.915 26.95 Sample 3 111 10546 0.047 11.086
Sample 1 36939 26530 11.784 26.869 Sample 3 111 10585 0.047 11.194
Sample 1 37605 26904 11.889 26.999 Sample 3 102 10561 0.044 11.111
Avg. 11.867 26.918 Avg. 0.047 11.141
Dev. 0.049 0.086 Dev. 0.003 0.040
Sample 2 117 18286 0.046 18.001 Sample 4 69 9047 0.035 10.048
Sample 2 119 17423 0.049 18.044 Sample 4 75 9570 0.035 9.938
Sample 2 127 18340 0.049 17.918 Sample 4 77 9909 0.034 9.829
Sample 2 132 19171 0.048 18.023 Sample 4 88 10921 0.035 10.156
Sample 2 121 17215 0.05 17.925 Sample 4 90 12868 0.03 9.939
Sample 2 157 18498 0.057 17.971 Sample 4 74 9482 0.035 9.96
Avg. 0.050 17.980 Avg. 0.034 9.978
Dev. 0.004 0.052 Dev. 0.002 0.112
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Recent Data – Liquid Fertilizers
Sample C% N% S% Comb. S% TKI
Sample 1 0.10 11.87 26.92 26.36
Sample 2 0.07 0.05 17.98 17.00
Sample 3 0.07 0.034 11.14 10.65
Sample 4 0.07 0.034 9.98 9.33
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Recent Data – Liquid Fertilizers
C
N
S
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Recent Data – Liquid Fertilizers
C
N
S
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Method Status
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Method OrganizationMaterial Expected S (%) No. of Labsa(b) Mean (%) Recoveryc (%) RSDr (%) RSDR (%)
HorRat
2011‐05 1.56 x (y) 0.01 95.0 1.0 1.5 0.52011‐08 6.392011‐06 11.952011‐01 13.222011‐07 7.76(NH4)SO4 24S 12‐508 90Cysteine 26.72Sulpomag 12‐1773 22(NH4)2SO3 12‐591 26K2SO4 KY12289 18a(b) a = number of labs retained after eliminating outliers, (b) = number of labs removed as outliersc c = when applicable
1. Principle2. Apparatus and Materials
a) Apparatus A: By TCDb) Apparatus B: By IR
3. Reagents4. Calibration Curve and Daily Factor5. Preparation of Test Samples (Analytical Samples)6. Determination7. Calculation8. Appendix
Next: Multi-lab validation study
• Currently we have enough labs who have offered to participate in upcoming ILS.
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Teresa GrantNorth Carolina Dept. of Agriculture & CoFood and Drug Protection Division
Paulo PagliariAsst ProfessorSoil Water ClimateUniversity of Minnesota/SWROC
Keith WegnerColorado Dept of Agriculture***collaborator and stakeholderContact about Leco analyzer
Larry CihacekSoil ScienceNorth Dakota State University
Jason KongOhio Dept. of Agriculture***stakeholder only
Job FugiceIFDC
Jian ZhangNevada Dept of Agriculture
Frank SikoraUniversity of Kentucky
Calum McCuskerElementar Americas
Bill HallMosaic Fertilizer LLC
Brenda KeaveyWest Virginia Department of AgricultureRegulatory and Environmental Affairs Division***needs to borrow analyzer***collaborator and stakeholder
Jack SchmanskyScotts Company****possible sponsor***collaborator and stakeholder
Sabine KrauseElementar Analysensysteme
Craig SpearsInspectorate3904 Corporex Park Dr.Tampa, FL 33619
Thank you!
Dr. Nancy ThiexAOAC International
Bill HallMosiac
Dr. Michael Hojjatie
Tessenderlo Kerely
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