New method for determination of total sulfur using high temperature combustion

Transcription

1 New method for determination of total sulfur using high temperature combustion Tyson Rowland Elementar Americas Product Manager Fertilizer Methods Forum February 2016

2 Current method AOAC Method 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

3 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!

4 Basic operating principle CH 3 (CH 2 ) x CH 3 + O 2 + contaminants CO 2 + H 2 O + NO x +SO 2

5 Schematic 1: Infrared Detection Advantage: Sensitive (as low as a under 10 mg/kg) Disadvantage: Matrix dependent

6 Schematic 2: Thermal Conductivity Detection Advantage: Multi-element analysis for simultaneous N analysis (run in conjunction with AOAC ) Disadvantage: Sensitivity (as low at 100 mg/kg, 0.01%), time (CNS)

7 Sample data CO 2 H 2 O Powerful, clear peak focusing and separation Area underneath peak corresponds to element content N 2 SO 2

8 Single-lab validation study

9 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 [(NH 4 ) 2 SO 4 ] fertilizer source has a quick burn that requires no accelerant, whereas a blended fertilizer product containing potassiummagnesium sulfate (K 2 MgO 8 S 2 ) 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.

10 SLV Overview

11 Instrument: vario MACRO cube

12 Sample preparation (solids) sample former tin boats and tin foil cups

13 Sample preparation (liquids) capsule press

14 Sample preparation (liquids)

15 Sample preparation (liquids)

16 Sample preparation (crucibles)

17 Sample preparation (auto-loader)

18 Recent Data Liquid Fertilizers Name Area [N] Area [S] % N % S Name Area [N] Area [S] % N % S Sample Sample Sample Sample Sample Sample Sample Sample Sample Sample Sample Sample Avg Avg Dev Dev Sample Sample Sample Sample Sample Sample Sample Sample Sample Sample Sample Sample Avg Avg Dev Dev

19 Recent Data Liquid Fertilizers Sample C% N% S% Comb. S% TKI Sample Sample Sample Sample

20 Recent Data Liquid Fertilizers N S C

21 Recent Data Liquid Fertilizers N S C

22 Method Status

23 Method Organization Material Expected S (%) No. of Labs a(b) Mean (%) Recovery c (%) RSD r (%) RSD R (%) Hor Rat x (y) (NH 4 )SO 4 24 S Cysteine Sulpomag (NH 4 ) 2 SO K 2 SO 4 KY a(b) a = number of labs retained after eliminating outliers, (b) = number of labs removed as outliers c c= when applicable 1. Principle 2. Apparatus and Materials a) Apparatus A: By TCD b) Apparatus B: By IR 3. Reagents 4. Calibration Curve and Daily Factor 5. Preparation of Test Samples (Analytical Samples) 6. Determination 7. Calculation 8. Appendix

24 Next: Multi-lab validation study Currently we have enough labs who have offered to participate in upcoming ILS. Teresa Grant North Carolina Dept. of Agriculture & Co Food and Drug Protection Division Larry Cihacek Soil Science North Dakota State University Jian Zhang Nevada Dept of Agriculture Bill Hall Mosaic Fertilizer LLC Sabine Krause Elementar Analysensysteme Paulo Pagliari Asst Professor Soil Water Climate University of Minnesota/SWROC Jason Kong Ohio Dept. of Agriculture ***stakeholder only Frank Sikora University of Kentucky Brenda Keavey West Virginia Department of Agriculture Regulatory and Environmental Affairs Division ***needs to borrow analyzer ***collaborator and stakeholder Craig Spears Inspectorate 3904 Corporex Park Dr. Tampa, FL Keith Wegner Colorado Dept of Agriculture ***collaborator and stakeholder Contact about Leco analyzer Job Fugice IFDC Calum McCusker Elementar Americas Jack Schmansky Scotts Company ****possible sponsor ***collaborator and stakeholder

25 Thank you! Dr. Nancy Thiex AOAC International Bill Hall Mosiac Dr. Michael Hojjatie Tessenderlo Kerely