AOAC ERP Fertilizers - December 2017

AOAC Official Methods of Analysis SM (OMA)

AOAC EXPERT REVIEW PANEL FOR FERTILIZERS

VIA GOTOMEETING AND TELECONFERENCE

Phosphorus and Potassium Monday, December 4, 2017 10:00AM – 12:30PM EST Total Sulfur Tuesday, December 5, 2017 11:00AM – 1:30PM EST Slow and Controlled Release Wednesday, December 6, 2017 10:00AM – 12:00PM

AOAC OFFICIAL METHODS OF ANALYSIS SM (OMA) EXPERT REVIEW PANE L FOR MICROBIOLOGY FOR FERTILIZERS TABLE OF CONTENTS

I. ABOUT AOAC OF F ICAL METHODS OF ANALYSIS ™....................................................................................... 3 II. AGENDA – PHOSPHORUS AND POTASSIUM ........................................................................................................ 7 III. AGENDA – TOTAL SULFUR .................................................................................................................................. 9 IV. AGENDA – SLOW AND CONTROLLED RELEASE .................................................................................................... 11 V. AOAC INT ERNATIONAL VOLUNTEER CONFLICT OF INTEREST, STATEMENT OF POLICY ........................................ 13 VI. AOAC IN TERNATIONAL ANT I TRUST POLICY STATEMENT AND GUIDELINES .................................15 VII. AOAC IN TERNATIONAL POLICY ON THE USE OF THE ASSOC I ATION NAME, INITIALS, IDENTIFYING I NSIGNIA, LETTERHEAD, AND BUSINESS CARDS ................................................................................................. 19 VIII. MEETING AND METHOD REVIEW INFORMATION ...................................................................................... 23 IX. AOAC EXPERT REVIEW PANEL ORIENTA TI ON PRESENTATION ................................................................25 X. REV IE W OF METHODS FOR AOAC FIRST ACTION OFFICIAL METHODS STATUS: A. OMAMAN-24: DETERMINATION OF TOTAL SULFUR IN FERTILIZERS BY HIGH TEMPERATURE COMBUSTION

1) OMAMAN -24 A : Collaborative Study Manuscript(Revised) ................................ 67 2) OMAMAN-24 B: Summary of Comments from vote on February 3, 2017 ........... 73 3) OMAMAN-24 C: Article: Determination of Total Sulfur in Fertilizers by High Temperature Combustion: Single-Laboratory Validation..................................... 79 4) OMAMAN-24 D: AOAC Expert Review Panel Report (September, 2015)............. 85

XI. REV IE W OF METHODS FOR AOAC FINAL ACTION OFFICIAL METHODS STATUS:

A. AOAC OFFICIAL METHOD 2015.18 PHOSPHORUS AND POTASSIUM IN COMMERCIAL INORGANIC FERTILIZERS INDUCTIVELY COUPLED PLASMA–OPTICAL EMISSION SPECTROMETRY, FIRST ACTION 2015 1) OMA 2015.18 A: Method......................................................................................... 93 2) OMA 2015.18 B: Article: Determination of Phosphorus and Potassium in Commercial Inorganic Fertilizers by Inductively Coupled Plasma–Optical Emission Spectrometry: Single-Laboratory Validation, First Action 2015.18 ................................................. 101 3) OMA 2015.18 C: AOAC Expert Review Panel Report (September, 2015) .............. 85 B. AOAC OFFICIAL METHOD 2015.15 NITROGEN, PHOSPHORUS, AND POTASSIUM RELEASE RATES OF SLOW-AND CONTROLLED-RELEASE FERTILIZERS, FIRST ACTION 2015 1) OMA 2015.15 A: Method......................................................................................... 109 2) OMA 2015.15 B: Article: Determination of Nitrogen, Phosphorus, and Potassium Release Rates of Slow- and Controlled-Release Fertilizers: Single-Laboratory Validation, First Action 2015.15................................................................................................. 115 3) OMA 2015.18 C: AOAC Expert Review Panel Report (September, 2015) ............... 85

AOAC INTERNATIONAL ● 2275 RESEARCH BLVD, SUITE 300 ● ROCKVILLE, MARYLAND 20850 USA

EXPERT REVIEW PANEL (ERP) FOR FERTILIZERS – PHOSPOHORUS AND POTASSIUM MONDAY, DECEMBER 4, 2017 10:00 AM – 12:30 PM GoToMeeting / Teleconference

EXPERT REVIEW PANEL CHAIR: WILLIAM HALL, MOSAIC

I.

WELCOME AND INTRODUCTIONS Expert Review Panel Co-Chairs

II. REVIEW OF AOAC VOLUNTEER POLICIES & EXPERT REVIEW PANEL PROCESS OVERVIEW AND GUIDELINES Deborah McKenzie, Senior Director, Standards Development and Method Approval Processes, AOAC INTERNATIONAL and AOAC Research Institute

III. DISCUSS FINAL ACTION REQUIREMENTS FOR FIRST ACTION OFFICIAL METHODS (IF APPLICABLE )

ERP will discuss, review and track First Action methods for 2 years after adoption, review any additional information (i.e., additional collaborative study data, proficiency testing, and other feedback) and make recommendations to the Official Methods Board regarding Final Action status. A. AOAC Official Method 2015.18 Phosphorus and Potassium in Commercial Inorganic Fertilizers Inductively Coupled Plasma–Optical Emission Spectrometry, First Action 2015 Original Study Director: James Bartos of the Office of Indiana State Chemist, Purdue University 175 South University Street, West Lafayette, Indiana 47907

IV.

ADJOURNMENT

*Agenda is subject to change. V1

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AOAC INTERNATIONAL ● 2275 RESEARCH BLVD, SUITE 300 ● ROCKVILLE, MARYLAND 20850 USA

EXPERT REVIEW PANEL (ERP) FOR FERTILIZERS – TOTAL SULFUR

TUESDAY, DECEMBER 5, 2017 11:00 AM – 1:30 PM GoToMeeting / Teleconference

EXPERT REVIEW PANEL CHAIR: WILLIAM HALL, MOSAIC

I.

WELCOME AND INTRODUCTIONS Expert Review Panel Co-Chairs

II. REVIEW OF AOAC VOLUNTEER POLICIES & EXPERT REVIEW PANEL PROCESS OVERVIEW AND GUIDELINES Deborah McKenzie, Senior Director, Standards Development and Method Approval Processes, AOAC INTERNATIONAL and AOAC Research Institute REVIEW OF METHODS For each method, the assigned ERP members will present a review of the proposed collaborative study manuscript, after which the ERP will discuss the method and render a decision on the status for each method. A. OMAMAN-24: Determination Of Total Sulfur Using High Temperature Combustion Original Study Director: Calum McCusker and Tyson Rowland, Elementar Americas, located at 520 Fellowship Road, Suite D-408, Mt. Laurel, New Jersey 08054

III.

IV. DISCUSS FINAL ACTION REQUIREMENTS FOR FIRST ACTION OFFICIAL METHODS (IF APPLICABLE )

ERP will discuss, review and track First Action methods for 2 years after adoption, review any additional information (i.e., additional collaborative study data, proficiency testing, and other feedback) and make recommendations to the Official Methods Board regarding Final Action status.

V.

ADJOURNMENT

*Agenda is subject to change. V1

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AOAC INTERNATIONAL ● 2275 RESEARCH BLVD, SUITE 300 ● ROCKVILLE, MARYLAND 20850 USA

EXPERT REVIEW PANEL (ERP) FOR FERTILIZERS – SLOW AND CONTROLLED RELEASE

WEDNESDAY, DECEMBER 6, 2017 10:00 AM – 12:00 PM GoToMeeting / Teleconference

EXPERT REVIEW PANEL CHAIR: WILLIAM HALL, MOSAIC

I.

WELCOME AND INTRODUCTIONS Expert Review Panel Co-Chairs

II. REVIEW OF AOAC VOLUNTEER POLICIES & EXPERT REVIEW PANEL PROCESS OVERVIEW AND GUIDELINES Deborah McKenzie, Senior Director, Standards Development and Method Approval Processes, AOAC INTERNATIONAL and AOAC Research Institute

III. DISCUSS FINAL ACTION REQUIREMENTS FOR FIRST ACTION OFFICIAL METHODS (IF APPLICABLE )

ERP will discuss, review and track First Action methods for 2 years after adoption, review any additional information (i.e., additional collaborative study data, proficiency testing, and other feedback) and make recommendations to the Official Methods Board regarding Final Action status. A. AOAC Official Method 2015.15 Nitrogen, Phosphorus, and PotassiumRelease Rates of Slow-and Controlled- Release Fertilizers, First Action 2015 Original Study Director: William Hall, Mosaic, 13830 Circa Crossing Drive, Lithia, Florida 33547

IV.

ADJOURNMENT

*Agenda is subject to change. V1

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Official Methods of Analysis SM (OMA) Expert Review Panel MEETING AND METHOD REVIEW GUIDANCE

The AOAC Research Institute administers AOAC INTERNATIONAL's premier methods program, the AOAC Official Methods of Analysis SM (OMA). The program evaluates chemistry, microbiology, and molecular biology methods. It also evaluates traditional benchtop methods, instrumental methods, and proprietary, commercial, and/or alternative methods and relies on gathering the experts to develop voluntary consensus standards, followed by collective expert judgment of methods using the adopted standards. The Official Methods of Analysis of AOAC INTERNATIONAL is deemed to be highly credible and defensible. All Expert Review Panel (ERP) members are vetted by the AOAC Official Methods Board (OMB) and serve at the pleasure of the President of AOAC INTERNATIONAL. In accordance to the AOAC Expert Review Panel Member and Chair Volunteer Role Description all Expert Review Panel members are expected to 1) serve with the highest integrity, 2) perform duties and method reviews, and 3) adhere to review timelines and deadlines.

To assist the ERP Chair and its members, please note the following in preparation for Expert Review Panel meetings and method reviews.

Pre-Meeting Requirements 1. Confirm availability and plan to be present to ensure a quorum of the ERP.

(Please refer to page 25, Quorum Guidelines, Expert Review Panel Information Packet ) 2. Ensure that your laptop, CPU or mobile device can access online web documentation. 3. Be prepared for the meeting by reviewing all relevant meeting materials and method documentation.

In-Person Meeting and Teleconference Conduct 1. Arrive on time.

2. Advise the Chair and ERP members of any potential Conflicts of Interest at the beginning of the meeting. 3. Participation is required from all members of the ERP. All members have been deemed experts in the specific subject matter areas. 4. The ERP Chair will moderate the meeting to ensure that decisions can be made in a timely manner. 5. Follow Robert’s Rules of Order for Motions. 6. Speak loud, clear, and concise so that all members may hear and understand your point of view. 7. Due to the openness of our meetings, it is imperative that all members communicate in a respectful manner and tone. 8. Refrain from disruptive behavior. Always allow one member to speak at a time. Please do not interrupt. 9. Please note that all methods reviewed and decisions made during the Expert Review Panel process are considered confidential and should not be discussed unless during an Expert Review Panel meeting to ensure transparency. Reviewing Methods Prior to the Expert Review Panel meeting, ERP members are required to conduct method reviews. All methods are reviewed under the following criteria, technical evaluation, general comments, editorial criteria, and recommendation status. These methods are being reviewed against their collaborative study protocols as provided in the supplemental documentation. Note: The method author(s) will be present during the Expert Review Panel session to answer any questions.

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Version 1 – OMA ERP Meeting Conduct

Official Methods of Analysis SM (OMA) Expert Review Panel MEETING AND METHOD REVIEW GUIDANCE

Reviewing Methods (Cont’d)

Reviewers shall conduct in-depth review of method and any supporting information. In-depth reviews are completed electronically via the method review form. The method review form must be completed and submitted by the deadline date as provided. All reviews will be discussed during the Expert Review Panel meeting. Any ERP member can make the motion to adopt or not to adopt the method. If the method is adopted for AOAC First Action status, Expert Review Panel members must track and present feedback on assigned First Action Official Methods . Recommend additional feedback or information for Final Action consideratio n. Here are some questions to consider during your review based on your scientific judgment: 1. Does the method sufficiently follow the collaborative study protocol? 2. Is the method scientifically sound and can be followed? 3. What are the strengths and weaknesses of the method? 4. How do the weaknesses weigh in your recommendation for the method? 5. Will the method serve the community that will use the method? 6. What additional information may be needed to further support the method? 7. Can this method be considered for AOAC First Action OMA status? Reaching Consensus during Expert Review Panel Meeting 1. Make your Motion. 2. Allow another member to Second the Motion. 3. The Chair will state the motion and offer the ERP an option to discuss the motion. 4. The Chair will call a vote once deliberations are complete. 5. Methods must be adopted by unanimous decision of ERP on first ballot, if not unanimous, negative votes must delineate scientific reasons. Negative voter(s) can be overridden by 2/3 of voting ERP members after due consideration. 6. All other motions will require 2/3 majority for vote to carry.

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Version 1 – OMA ERP Meeting Conduct

AOAC Official Method 2016. xx

Determination of Total Sulfur in Fertilizers by High Temperature Combustion

Proposed First Action 2015

(Applicable for measuring total sulfur concentration in solid and liquid inorganic fertilizers in the range of 1 – 100% with an LOD and LOQ of 47 and 106 µg S, respectively. [to be determined by MLV] )

Caution: Elemental analysis using combustion includes the risk of burn as some instrument components operate hot. Even after switching off the instrument, some components stay hot for long periods of time. Serious burns can occur if working inappropriately inside the instrument. Follow manufacturer specific operating instructions for safest handling.

See Table 1 for interlaboratory study results that support the acceptance of this method.

Table 1. Interlaboratory study results for total sulfur in fertilizer and pure chemical standards.

No. of Labs a(b)

Recovery c (%)

Material

Expected S (%)

Mean (%)

RSD r

(%)

RSD R

(%)

HorRat

2011-­‐05 2011-­‐08 2011-­‐06 2011-­‐01 2011-­‐07

1.56 6.39

x (y)

0.01

95.0

1.0

1.5

0.5

11.95 13.22

7.76

(NH 4

)SO 4

24 90

S 12-­‐508 Cysteine

26.72

Sulpomag 12-­‐1773

22 26

(NH 4

) 2

SO 3

12-­‐591

K 2 18 a(b) a = number of labs retained after eliminating outliers, (b) = number of labs removed as outliers c c = when applicable SO 4 KY12289

A. Principle

This procedure involves conversion of sulfur (S) species from fertilizers and chemical standards into SO 2 through combustion at a temperature >1100°C followed by measurement with thermal conductivity detection (TCD) or infrared (IR) detection reported as weight/weight percentage (w/w %). In the case of thermal conductivity detection and where simultaneous measurements of additional elements, such as carbon (C), hydrogen (H), or nitrogen (N), are performed an intermediate SO 2 separation by thermal adsorption/desorption is necessary. In accordance, this method allows simultaneous conformation to AOAC Method 993.13, Nitrogen in Fertilizers by Combustion , when using thermal conductivity detection. (1)

B. Apparatus and Materials

Total sulfur measurements can be performed via two variable apparatus types depending on detection method of choice.

(a) Apparatus A: Combustion followed by thermal conductivity detection —

1

For Apparatus A type instruments, shown in Figure 1, sulfur as SO 2 is determined by TCD with helium or argon carrier gas allowing for multi-­‐element analysis. With this setup the test portion should be introduced into the combustion zone in a way such that atmospheric contamination is removed. Oxygen is added over the test portion at a temperature >1100°C converting all elements to their fully oxidized gaseous specie. A catalyst, such as tungsten (IV) oxide (WO 3 ), inside the combustion tube is used to aid oxidation. Following combustion, gases pass through a reducing environment and halogen scrubber in order that NO x species be converted to N 2 and removal of halogen contaminants, respectively. Other resulting combustion gas components CO 2 , H 2 O, and SO 2 are scrubbed or adsorbed on analyte-­‐specific thermal adsorption/desorption columns. N 2 is not adsorbed and flows directly to the thermal conductivity detector. Each CO 2 , H 2 O, and SO 2 are desorbed sequentially following the previous elements complete measurement by the TCD allowing for clear separation of the analyte species. Scrubbing materials may be used to remove each CO 2 and/or H 2 O if determination of either C and/or H is undesired. Software processing will convert the SO 2 peak signal into a w/w percentage.

Figure 1. Typical multi-­‐element measuring combustion system using adsorption/desorption separations and TCD. . (b) Apparatus B: Combustion followed by infrared detection — is determined by a sulfur-­‐specific IR detector with oxygen carrier gas. The test portion is introduced into the combustion zone where oxygen in combination with a temperature >1100°C converts S " SO 2 . A catalyst, such as tungsten (IV) oxide (WO 3 ), inside the combustion tube is used to aid oxidation. The gas stream is dried before entering the detector. With this apparatus type, variable amounts of CO 2 , NO x and/or halogen combustion products may influence the results of SO 2 measurement by the IR detector. Software processing will convert the SO 2 peak signal into a w/w percentage. For best results using this apparatus type follow special instructions in Section D. For Apparatus B type instruments, shown in Figure 2, sulfur as SO 2

Figure 2. Typical sulfur only measuring combustion analyzer using SO 2

-­‐specific IR detection.

(c) Analytical balance — resolution to 0.01 mg (d) Test portions containers — typically tin foil (e) Hand pellet press — for pelletizing powder materials (f) Capsule sealing press — for making a gas-­‐tight cold seal on tin capsule holding liquid materials

2

C. Reagents

(a) Helium or Argon — minimum 99.995% purity (b) Oxygen — minimum 99.995% purity (c) Tungsten (VI) oxide (WO 3

) granulate — supplied by the instrument manufacturer ) powder — supplied by the instrument manufacturer

(d) Tungsten (VI) oxide (WO 3

(e) Copper wires — supplied by the instrument manufacturer (f) Corundum balls (inert) — supplied by the instrument manufacturer (g) Quartz wool (inert) — supplied by the instrument manufacturer (h) Silver wool — supplied by the instrument manufacturer (i) Sicapent® with indicator — supplied by the instrument manufacturer

D. Calibration Curve and Daily Factor

Check calibration on the instrument (B(a)) , (B(b)) , daily and perform as needed according to the manufacturer’s recommendation. For Apparatus A instruments (B(a)) , it is recommended that a n onhygroscopic pure chemical standard be used for calibrating the instrument, such as sulfanilamide (≥99%) or phenylalanine (≥99%). Use a minimum of five calibration points to generate the calibration curve and cover the absolute sulfur range encompassing that of expected S concentration in unknowns. Any drift in the calibration curve can be observed and corrected for by daily use of an alternative n onhygroscopic pure chemical standard of known S concentration. Follow manufacturer’s instructions for setting up and calculating drift corrections. If the drift correction or daily factor exceeds 0.9 or 1.1, perform necessary maintenance and ensure reagents in the combustion or reduction tubes are not depleted. Apparatus B type instruments (B(b)) pose several matrix and sensitivity analytical challenges, especially when S determination for a wide range of fertilizer products or an unknown source is required. Burn rates, scrubber types, and the need for accelerants is a function of the fertilizer type resulting in dramatically different scan shapes and peak areas for different products. Unknown and calibration materials must be matrix 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 potassium-­‐magnesium 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 is the separation of unknowns into low and high S concentrations as low concentrations require a longer cell length that could be overwhelmed by high S concentrations. Failure to do so may result in excessive carryover. In cases where S concentrations and matrix types are known, they should be presorted and run to best match the calibration material and concentration range. In cases where the S source is unknown, it is necessary to make a test scan and compare to scans from various fertilizer sources to determine the best calibration material and concentration. Liquid Fertilizers — Collect liquid ammonium thiosulfate fertilizers using AOAC Method 969.01, or other recognized procedure. A c c u r a t e l y w e i g h test portions containing a sulfur amount within the calibration range (typically 20 – 100 mg) into a tared tin capsule or ceramic crucible (B(d)) , already containing tungsten (IV) oxide powder (C(d)) to be used as combustion aid. For tin capsules, cold weld with a capsule sealing press (B(f)) , and accurately weigh the test portion to the nearest 0.01 mg. Do not include the WO 3 powder in the final weight. Insert weight into the operating software. Optionally, the test portion can be weighed into a tin foil containing WO3 and dried at 60 °C for 2 hours. After which, the foil can be pelletized, (B(e)), to be run as a solid. Solid Fertilizers — Solid elemental S fertilizers should be collected using AOAC Method 929.01, or other recognized procedure. Prepare an analytical sample of sufficiently small particle size to ensure sufficient representation at the expected test portion mass. Accurately weigh test portions containing a sulfur amount within the calibraton range (typically 20 – 100 mg) into a tared tin foil cup or ceramic crucible (B(d)) , to the nearest 0.01 mg. Additionally, add WO 3 powder (C(d)) Special Consideration for Apparatus B Instruments — E. Preparation of Test Samples (Analytical Samples)

3

creating an approximate 10:1 ratio of combustion aid to test portion. If using tin foil, pelletize the foil cup using an appropriate sealing device (B(e)) , .

F. Determination

(a) Ensure that the instrument is powered on, leak free and the parameters are set according to the manufacturer’s instructions. This includes furnace temperatures, flows and pressures. (b) Ensure that reagents (C(a)), (C(b)), (C(d)), (C(e),) (C(f), (C(g)) , (C(h)), (C(i)) are not spent and still of functional use. (c) Run blanks and check the calibration according to Section D. Use the daily factor or recalibrate if necessary. (d) Prepare and weigh the test portion according to Section E. (e) Load the test portions onto the instrument and run the apparatus according to manufacturer’s instructions.

G. Calculations

Element concentration (content, w/w %) is given by the instrument software. Absolute element content can be computed according to the following equation if needed: = × 100 where: A = absolute element content in mg, W = sample weight in mg, and C = element concentration in percentage.

H. Appendix (Nonmandatory Information)

Ruggedness trial —

A ruggedness trial with eight determinations was used to explore the effects of the seven most important factors as described in the AOAC requirements for single laboratory validations: no blank measurement, improper addition of WO 3 , incorrect oxygen dosing, not wrapping test portion in tin, improper combustion temperature, high and low sample weights, and broken oxygen dosing device. (1) Each factor was assigned with reasonable high and low values. The effect of each factor was determined by the difference in S content when a factor was changed from high to low levels. Factors with extreme differences between high and low levels were noted. Magruder 2012-­‐10 was the only matrix used in the trial. This material was selected as the most recent material available at the time of the trial. Source of S in Magruder 2012-­‐10 is ammonium sulfate with an expected S value of 5.48%. The squared differences of each parameter were determined according to the Youden and Steiner Statistical Manual of the AOAC and listed based on their value (Table 2).

Ruggedness trial results showed no appreciable effect from the deviations of the method as noted, although caution should be taken to determine a blank measurement and use the proper 10:1 ratio of combustion aid to sample weight.

Table 2. Ruggedness trial method deviations and squared differences Parameter

Squared difference

No blank measurement

0.08

4

WO 3

addition of 8:1 and 12:1

0.06 0.03

Wrong method oxygen dosing Wrong test portion wrap, not tin Combustion tube 1100°C or 1170°C Test portion weight 20 or 60 mg Broken oxygen dosing device

0.003 0.002 0.002

0.00001

Quality Control —

(a) Perform blank determination before daily operation and any time a reagent or carrier gas tank is replaced. (b) Perform drift correction using a suitable standard before each day’s analyses. (c) Include at least one reference material with each batch of 30 test portions. Results should be within limits specified for reference material. Reference materials can include a fine chemical of known S content such as sulfanilamide, a Magruder check sample, or a National Institute of Standards and Technology reference material. (d) Perform replicate analyses on at least 10% of the test portions, or every test portion if homogeneity is difficult to achieve. Replicate results should be within 10–15% of the mean value of the replicates.

I.

References

(1) Bernius et al., JAOAC, 97 (2014) p. 731-­‐735. DOI: http://dx.doi.org/10.5740/jaoacint.13-­‐385.

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AOAC RESEARCH INSTITUTE AOAC OFFICIAL METHODS OF ANALYSIS (OMA) OMAMAN-24: DETERMINATION OF TOTAL SULFUR IN FERTILIZERS BY HIGH TEMPERATURE COMBUSTION

BACKGROUND In September 2015, the AOAC Expert Review Panel for Fertilizer Methods, Total Sulfur met to review the manuscript entitled, Determination of Total Sulfur in Fertilizers by High Temperature Combustion as submitted by Elementar Americas. The ERP passed the following motions: 1. Motion by Phillips; Second by Wegner, to move OMAMAN‐24 to AOAC First Action Official Methods status. Passed unanimously. 2. Motion by Phillips; Second by Wegner, to edit the method prior to First Action publication to accommodate sample preparation, instrument conditions, safety, and to allow for other instrument manufacturers. Passed unanimously. In February 2016, the method authors of Elementar Americas submitted their final revised manuscript with the incorporated ERP pre-publication requirements to AOAC. AOAC forwarded the manuscript and AOAC forwarded the revised manuscript to the ERP for review to determine that the ERP pre-publication criteria were met. In March 2016, the following comments resulted from this electronic review by the ERP: 1. Table 1 is out-of-place. The First Action method recommendation is based upon the SLV study and as such there is no collaborative/interlaboratory data available yet. This would be appropriate at the next stage after the collaborative study has been completed, but should be deleted at this point. That said, based upon my next comment, a modified version of Table 1 would be appropriate if previous Elementar data from the SLV study could be compared with new Apparatus B/Figure 2 instrument data from another source(s). 2. The ERP expressed concerns that the method was primarily tailored to one manufacturer. Apparatus B and Figure 2 does adequately address the fact that another common approach/technology exists, but there are also concerns expressed regarding its performance. If data could be generated from one competent lab that uses the Apparatus B/Figure 2, then this comparative data would go a long way to satisfy anyone’s concern about the method being developed for only one instrument manufacturer. 3. This may be beyond the scope of simply determining whether the authors addressed the concerns raised by the ERP, but extra work will be required to place the document in First Action format. For example, sections B and C will require the manufacturer, model or part number, and corporate headquarters and the word “or equivalent.” Also, more information on Preparation of Test Samples (i.e. Prepare an analytical sample of sufficiently small particle size to ensure sufficient representation… is too vague; how to prepare the sample and particle size range is recommended). Reconciling the difference between %S in the sample and mg S in the sample to weigh may need to be added to the calculations and/or in a Table. In May - August 2016: Held teleconferences with ERP chair and the specific ERP member(s) with the above comments to work out details of what would be needed. Additionally, the ERP chair corresponded with the method authors

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AOAC RESEARCH INSTITUTE AOAC OFFICIAL METHODS OF ANALYSIS (OMA) OMAMAN-24: DETERMINATION OF TOTAL SULFUR IN FERTILIZERS BY HIGH TEMPERATURE COMBUSTION

regarding the manuscript comments and coordinated distribution of samples to the instrument manufacturers so as to collect data based on the above comments. In September 2016: The method authors along with instrument manufacturers attended the ERP session and presented on how the method works with the new instruments and some initial data collection. The manuscript and method revisions were not submitted at that time. In January 2017: Revised method submitted by Elementar Americas. It includes references to interlaboratory studies; however, this work is not yet complete. RECOMMENDATION: Reflective of the unanimously passed motion moved by the ERP in September, 2015 to edit the method prior to First Action publication to accommodate sample preparation, instrument conditions, safety, and to allow for other instrument manufacturers : ERP members will need to confirm whether OMAMAN-24, which was moved to First Action Official Methods status in 2015, is now ready for publication in the Official Methods of Analysis of AOAC INTERNATIONAL. Please review the attached document and make your recommendation. If this method has satisfied the requirements of the Expert Review Panel as noted above, please indicate by selecting one of the following options below by copying and pasting in your reply email: • I AGREE that the method as revised, Total Sulfur in Fertilizers by High Temperature Combustion , is now ready for publication in the Official Methods of Analysis of AOAC INTERNATIONAL. • I DISAGREE that the method as revised, Total Sulfur in Fertilizers by High Temperature Combustion , is now ready for publication in the Official Methods of Analysis of AOAC INTERNATIONAL. If you select, “I Disagree”, please indicate what part of the motion has not been fulfilled based on your review of the revised method.

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AOAC RESEARCH INSTITUTE AOAC OFFICIAL METHODS OF ANALYSIS (OMA) OMAMAN-24: DETERMINATION OF TOTAL SULFUR IN FERTILIZERS BY HIGH TEMPERATURE COMBUSTION

SUMMARY OF RESPONSES FROM ERP: ER 1

I AGREE that the method as revised, Total Sulfur in Fertilizers by High Temperature Combustion , is now ready for publication in the Official Methods of Analysis of AOAC INTERNATIONAL. I AGREE that the method as revised, Total Sulfur in Fertilizers by High Temperature Combustion , is now ready for publication in the Official Methods of Analysis of AOAC INTERNATIONAL. ER 3 According to Magruder data presented at the annual AAFPCO summer meeting in Pittsburg in 2016, Sulfur analysis by combustion showed slightly better RSD within Lab than gravimetric and Microwave. However, at this point I will disagree with moving the OMAMAN‐24 to first action pending the following: 1. Because one of the stated strength of the method is the simultaneity of analysis with nitrogen it would be prudent to present nitrogen data generated simultaneous with the sulfur data. 2. Information on sample throughput would also be of help 1. Table 1 is out-of-place. The First Action method recommendation is based upon the SLV study and as such there is no collaborative/interlaboratory data available yet. This would be appropriate at the next stage after the collaborative study has been completed, but should be deleted at this point. That said, based upon my next comment, a modified version of Table 1 would be appropriate if previous Elementar data from the SLV study could be compared with new Apparatus B/Figure 2 instrument data from another source(s). 2. The ERP expressed concerns that the method was primarily tailored to one manufacturer. Apparatus B and Figure 2 does adequately address the fact that another common approach/technology exists, but there are also concerns expressed regarding its performance. If data could be generated from one competent lab that uses the Apparatus B/Figure 2, then this comparative data would go a long way to satisfy anyone’s concern about the method being developed for only one instrument manufacturer. 3. This may be beyond the scope of simply determining whether the authors addressed the concerns raised by the ERP, but extra work will be required to place the document in First Action format. For example, sections B and C will require the manufacturer, model or part number, and corporate headquarters and the word “or equivalent.” Also, more information on Preparation of Test Samples (i.e. Prepare an analytical sample of sufficiently small particle size to ensure sufficient representation… is too vague; how to prepare the sample and particle size range is recommended). Reconciling the difference between %S in the sample and mg S in the sample to weigh may need to be added to the calculations and/or in a Table. ER 2 ER 4

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AOAC RESEARCH INSTITUTE AOAC OFFICIAL METHODS OF ANALYSIS (OMA) OMAMAN-24: DETERMINATION OF TOTAL SULFUR IN FERTILIZERS BY HIGH TEMPERATURE COMBUSTION

ER 5

• I AGREE that the method as revised, Total Sulfur in Fertilizers by High Temperature Combustion , is now ready for publication in the Official Methods of Analysis of AOAC INTERNATIONAL.

ER 6 ER 7

AWAITING RESPONSE AWAITING RESPONSE

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AOAC RESEARCH INSTITUTE AOAC OFFICIAL METHODS OF ANALYSIS (OMA) OMAMAN-24: DETERMINATION OF TOTAL SULFUR IN FERTILIZERS BY HIGH TEMPERATURE COMBUSTION

Reviewers

ER 1 ER 2 ER 3 ER 4 ER 5 ER 6 ER 7

Keith Wegner Salvatore Parisi Solomon Kariuki James Bartos

William Hall Heidi Phillips

Elizabeth Guertal

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OMAMAN-24 A /Single Laboratory Validation Expert Review Panel for Fertilizers September 2015

B ernius et al .: J ournal of AOAC I nternational V ol . 97, N o . 3, 2014  731

SPECIAL GUEST EDITOR SECTION

Determination of Total Sulfur in Fertilizers by High Temperature Combustion: Single-Laboratory Validation J ean B ernius elementar Americas, Mt. Laurel, NJ 08054 S abine K raus Elementar Analysensysteme GmbH, Hanau, Germany S andra H ughes elementar Americas, Mt. Laurel, NJ 08054 D ominik M argraf Elementar Analysensysteme GmbH, Hanau, Germany J ames B artos and N atalie N ewlon Office of Indiana State Chemist, Purdue University, 175 S. University St, West Lafayette, IN 47907-2063 H ans -P eter S ieper Elementar Analysensysteme GmbH, Hanau, Germany

a gravimetric technique using barium to precipitate the sulfate and carbon disulfide to solubilize the elemental S. This method is labor-intensive and requires handling of hazardous materials. As an alternative technique, combustion elemental analysis is automated and is a safe technique for S determination. The required instrumentation is already in use for nitrogen (N) determination in fertilizer, AOAC Method 993.13  (3), and is familiar to laboratories making these determinations. 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 potassium-magnesium 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 S

Guest edited as a special report from the AOAC Agricultural Community on “Collaborations in New and Improved Methods of Analysis for Plant Food Materials” by Nancy Thiex. Corresponding author’s e-mail: j_bernius@elementar-inc.com DOI: 10.5740/jaoacint.13-385 of low S diesel fuel. Changing agronomic practices such as no or low tilling and early planting also contribute to S deficiency (1). Increased use of S-containing fertilizers has driven demand for more S determinations, including sulfate and elemental S in blended fertilizers (Hall, B., Mosaic Fertilizer, 2013, personal communication). The current AOAC Method 980.02  (2) for S in fertilizer is A single-laboratory validation study was conducted for the determination of total sulfur (S) in a variety of common, inorganic fertilizers by combustion. The procedure involves conversion of S species into SO 2 through combustion at 1150°C, absorption then desorption from a purge and trap column, followed by measurement by a thermal conductivity detector. Eleven different validation materials were selected for study, which included four commercial fertilizer products, five fertilizers from the Magruder Check Sample Program, one reagent grade product, and one certified organic reference material. S content ranged between 1.47 and 91% as sulfate, thiosulfate, and elemental and organically bound S. Determinations of check samples were performed on 3 different days with four replicates/day. Determinations for non- Magruder samples were performed on 2 different days. Recoveries ranged from 94.3 to 125.9%. ABS SL absolute SD among runs ranged from 0.038 to 0.487%. Based on the accuracy and precision demonstrated here, it is recommended that this method be collaboratively studied for the determination of total S in fertilizers. S ulfur (S) deficiency in corn and other crops is becoming more prevalent. Less S is being deposited into the soil due to reductions in power plant emissions and increased use

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Copyright: © 2014 AOAC INTERNATIONAL. This is an open-access article, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.

OMAMAN-24 A /Single Laboratory Validation Expert Review Panel for Fertilizers September 2015

732  B ernius et al . : J ournal of AOAC I nternational V ol . 97, N o . 3, 2014

( i )  Sulfanilamide .—Sigma-Aldrich (St. Louis, MO) as sample additive.

Table 1. Operating conditions Combustion furnance temp., ° C

1150

Reduction furnace temp., ° C

850

Test Sample Preparation

Oxygen pressure, bar

2.0–2.2

( a )  Source of materials .—For method validation experiments, S-containing materials were obtained from commercial sources, the Magruder Check Sample Program, and previously analyzed fertilizer samples provided by the OISC and Kentucky Division of Regulatory Services (Lexington, KY). The materials were chosen to represent a range of S concentrations and matrixes that make up 90% of fertilizer tonnage worldwide (Hall, B., Mosaic Fertilizer, personal communication, 2013). The concentration of the validation materials ranged from 1.47 to 91% S and included sulfate, thiosulfate, and blended elemental S and sulfate- containing fertilizers. To obtain materials for Magruder Check Sample Program go to www.magruderchecksample.org. ( b )  Sampling and sample preparation .—The liquid ammonium thiosulfate sample was collected using AOAC Method 969.01  (4). A field inspector collected approximately 500 mL sample from a tap point on a liquid bulk storage tank. After shaking the plastic field container well, approximately 50 mLwas poured into a clean 100 mL glass jar that served as the laboratory test portion. The remaining sample was retained for result confirmation or dispute resolution. The solid elemental S sample was collected using AOAC Method 929.01  (5). Multiple cores were taken from a bulk sample resulting in approximately a 2.3 kg subsample. The subsample was reduced further with a Carpco (Jacksonville, FL) SS16-25 gated riffler. Approximately 200 g sample was finely ground using a Retsch (Newtown, PA) ZM200 grinder and a 1 mm screen and then poured into a clean 100 mL glass jar. The glass jar was rotated multiple times to ensure sample uniformity before testing. An unground portion was retained for result confirmation or dispute resolution. All samples were stored at room temperature in restricted access, locked storage. The Magruder samples were used as prepared by the Check Sample Program supplier. All of these samples were stored at room temperature in sealed plastic pouches.

Helium pressure, mbar

1200–1250

Method for oxygen dosing

Sulf1, Sulf2, blank according to instrument software

determination in single species and complex blended fertilizer products.

Experimental

Principle The sample is wrapped in tin foil and dropped into the analyzer through a blank-free helium-purged ball valve. Oxygen is jet injected over the sample at 1150°C. Separation of combustion gases is performed using a thermal desorption purge and trap chromatographic method. Combustion gas components CO 2 , H 2 O, and SO 2 are adsorbed on three specific columns. N is not adsorbed and flows directly to the thermal conductivity detector (TCD). Based on the detector reading, gas components are released sequentially from their individual adsorption/desorption columns. Time of analysis for C, N, and S is 8 min/sample. S analysis is not available as a single analyte. ( a )  Analytical balance .—Resolution to 0.01 mg (Mettler- Toledo, Columbus, OH). ( b )  vario MACRO cube analyzer .—Elementar Analysensysteme GmbH (Hanau, Germany). ( c )  Tin foil and tin capsule sample containers .—Elementar Analysensysteme GmbH. ( d )  Sample hand press for powdered samples .—Elementar Analysensysteme GmbH. ( e )  Sample sealing press for liquid samples.— Elementar Analysensysteme GmbH. ) granulate .—Supplied by the instrument manufacturer (Elementar Analysensysteme GmbH). ( d )  Copper wires .—Supplied by the instrument manufacturer (Elementar Analysensysteme GmbH). ( e )  Corundum balls .—Supplied by the instrument manufacturer (Elementar Analysensysteme GmbH). ( f )  Quartz wool .—Supplied by the instrument manufacturer (Elementar Analysensysteme GmbH). ( g )  Silver wool .—Supplied by the instrument manufacturer (Elementar Analysensysteme GmbH). ( h )  Sicapent ® with indicator .—Supplied by the instrument manufacturer (Elementar Analysensysteme GmbH). Apparatus Reagents ( a )  Helium .—99.995% purity (Praxair, Danbury, CT). ( b )  Oxygen .—99.995% purity (Praxair). ( c )  Tungsten (VI) oxide (WO 3

Calibration Standard AOAC Research Institute Expert Review Panel Use Only Factory calibration of the combustion analyzer was tested daily using 99% purity sulfanilamide. Drift correction was applied by the instrument software. Operating Procedure

The elements C , H, N, and S bound in the sample burn to form CO 2 , H 2 O, N 2 , NO X , SO 2 , and SO 3 . Halogen bound in the sample reacts to form volatile halogen compounds within the combustion tube. WO 3 granulate delivers additional oxygen to prevent the formation of nonvolatile sulfates and to bind alkali and alkaline earth elements. The carrier gas flow transfers the gaseous combustion products into the reduction tube, where copper contact completely reduces NO X to N 2 . SO 3 is reduced to SO 2 . Volatile halogen compounds are bound on silver wool. H 2 O contained in the reaction gas mixture is bound in an absorption tube filled with Sicapent. N 2 gas bypasses the adsorption/desorption columns and passes directly to the TCD. When the N 2 peak comes down to baseline,

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the adsorption column is heated to CO 2

and

then SO 2

desorption

material. Reference materials can include a fine chemical of known S content such as sulfanilamide, a Magruder check sample, or a National Institute of Standards and Technology reference material. ( d ) Perform replicate analysis on at least 10% of the samples, or every sample if homogeneity is difficult to achieve. Replicate results should be within 10–15% of the mean value of the replicates. This method was validated in a single laboratory by a single analyst. Validation experiments were conducted using 11 materials including five from the Magruder Fertilizer Check Sample Program, four previously analyzed fertilizer samples from the OISC and Kentucky Division of Regulatory Services, and two commercial S-containing materials. For the Magruder samples, the grand average of results, after outlier removal, obtained for each analyte/method combination on a check sample material was considered a consensus value. The consensus values were used in the absence of reference materials to validate the method. Participating laboratories submitted their results to the Association of American Plant Food Control Officials Magruder Program, and the grand average (minus outliers) for each analyte/method combination was publicly posted. Label values for ammonium sulfate U.S. Pharmacopeia grade and O-acetyl-l-serine cysteine were used. Previously determined S concentrations were used for ammonium thiosulfate 12-1591, sulpomag 12-1773, and elemental S 12-0508 as determined by the OISC. Previously determined S concentration was used for potassium sulfate 12289 as determined by the Kentucky Division of Regulatory Services (Table 2). ( a )  Linearity and range.— The instrument was calibrated according to the manufacturer’s instruction utilizing a total of 32 different sulfanilamide (purity ≥99%) and phenylalanine (purity ≥99%) samples of known weight. The calibration covered 19.73–11190.62 µg absolute element content for S. For a 30 mg sample, this correlates to 660 ppm to 37.3% S. The calibration functions for S content are best described on the basis of fourth- order polynomial functions. SD of the method for S was 11.73 µg. ( b )  Accuracy.— Matrix effects were investigated using three sulfanilic acid samples with an average sample weight of 30 mg. A recovery of >99% was achieved. The accuracy of the method was determined by comparing results to the accepted published values of the check samples, previously analyzed samples, and label values. The accepted value of the check sample (usually called the grand average) was calculated from results submitted to the respective check sample program managers from the dozens of laboratories participating, using statistical packages established by the Magruder Program. The difference between the grand average or previously reported results and the results obtained by the proposed method was reported as both a recovery and a bias, where a negative value indicates the method average is lower than the grand average and a positive number indicates the method average is higher than the grand average. Recovery and bias were calculated for each validation material as compared to the published available S grand averages (Table 3). (c )  Precision.— Each Magruder check sample validation material was analyzed on 3 different days with four replicates/ day. Other materials were analyzed on 2 different days with Validation of the Method

and H 2

O adsorption columns are bypassed

temperatures. The CO 2

via two valves. An absorption tube removes traces of H 2 is desorbed and enters the detector with the carrier gas. A fan cools the adsorption column, making it ready for the next analysis. The software reports C, N, and S but since C is not of interest, analysts can disregard C results. N results may be of interest. The N method conforms to AOAC Method 993.13 (3). Caution : During operation, the furnaces, the valve area, and the quartz glass bridge inside the instrument reach very high temperatures (in excess of 1000°C). Even after switching off the instrument, these components stay hot for long periods of time. Serious burns can occur if working inappropriately inside the instrument. ( a ) Weigh 26–50 mg samples into tin foil cones or tin capsules. Add between 260 and 500 mg WO 3 combustion aid for a 10:1 ratio of aid to sample. Seal with appropriate sealing device. ( b ) Turn on the vario MACRO cube analyzer. Conduct a leak check. Ensure combustion, reduction, and drying tubes do not need replacement. When furnace temperatures are up to required values, analysis may begin. ( c ) Load carousel with start-up samples: three blanks, three run in or conditioning samples using sulfanilamide, and three standard samples using 15 mg sulfanilamide. Include a sulfanilamide standard sample after every 10 samples and as the last sample in the batch to check for drift in the calibration. ( d ) Analyze standards and samples while monitoring instrument conditions for proper gas flows, restrictions, leaks, and consumable reagent life. O from the gas stream. SO 2 Calibration is performed by analyzing samples of nonhygroscopic fine chemicals with known concentrations (standard samples) in which the measured peak areas are correlated with the corresponding absolute element content. In a standard sample, the following parameters are known: element concentration (content, %) and weight. Absolute element content is computed according to the following equation: A = WC/100 where A= absolute element content in mg, W = sample weight in mg, and C = element concentration in percentage. ( a ) Blank determination should be performed before daily operation and any time a reagent or carrier gas tank is replaced. ( b ) Drift correction using 15 mg sulfanilamide standard should be performed before each day’s analyses. If the drift correction or daily factor exceeds 0.9 or 1.1, maintenance must be performed to check for leaks or that reagents in the combustion or reduction tubes are not spent. ( c ) Include one reference material with each batch of 30 samples. Results should be within limits specified for reference Quality Control Operating Conditions See Table 1. Calculations

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