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Microwave Calibration

Microwave Calibration. Brenda R. Cleveland Plant/Waste/Solution/Media Section NCDA&CS Agronomic Division. Presentation Today Microwave Calibration. Procedure But first . . . PWSM Section. Legislature enacted the service in 1974 Analyze about 30,000 up to 35,000 samples annually

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Microwave Calibration

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  1. Microwave Calibration Brenda R. Cleveland Plant/Waste/Solution/Media Section NCDA&CS Agronomic Division

  2. Presentation TodayMicrowave Calibration • Procedure • But first . . . NCDA&CS Agronomic Division

  3. PWSM Section • Legislature enacted the service in 1974 • Analyze about 30,000 up to 35,000 samples annually • 18,000 waste • 9-10,000 plant (this year >11,300) • 2-3,000 solution and • 2-300 media NCDA&CS Agronomic Division

  4. PWSM Section • Analyses (N, P, K, Ca, Mg, S, Fe, Mn, Zn, Cu, B, Na) • Fees • Routine $5 • Research $12 • Out-of-State (2005) $25 • Plus fees for additional tests • NO3-N/NH4-N, heavy metals, CCE ($10 each) • Petiole NO3-N, Mo, Cl ($2 each) NCDA&CS Agronomic Division

  5. PWSM Section • Six full-time laboratory staff plus 2-3 additional staff during busy season • Chemistry Lab Supervisor (Mark Buchanan) • Chemist I (Jan Queen) • 3 Chemistry Technician III (Ying Kritalugs, Donta Baker and Kyle Crump) • 3 Research Technicians (Karla Barefoot, Ma Kpa, Brenda Woodall) NCDA&CS Agronomic Division

  6. PWSM Section • One Agronomist (Dr. Michelle McGinnis) • One Processing Assistant (Darlene Carpenter) • One Section Chief (Brenda Cleveland) NCDA&CS Agronomic Division

  7. Microwave Procedure for ICP Analysis • Add 10 ml of nitric acid to each sample; • 0.5 g plant/solid waste or 5 ml liquid waste • Space samples evenly in microwave • Digest for 30 minutes at 210 watts • Flush sides of the flasks with hydrogen peroxide • Digest for 4 minutes more at 390 watts Actual time varies depending upon the # of samples NCDA&CS Agronomic Division

  8. Quality Control • To verify that the samples have been cooked at the correct power? (210 then 390 watts) • calibrate • adjust • NIST sample NCDA&CS Agronomic Division

  9. Calibrate • Calibration is the process of adjusting the output or indication on a measure-ment instrument to agree with value of the applied standard, within a specified accuracy • Assures that microwave power is accurate and samples are digested according to the SOP NCDA&CS Agronomic Division

  10. Calibration • Monthly calibration of all microwaves • Followed by analysis of a NIST sample to verify that our procedure from start to finish NCDA&CS Agronomic Division

  11. Calibration - Preliminary • Microwave is warmed • Remove turntable • Cook 1000 ml of water in a beaker at full power (100%) for 5 minutes • Use room temperature DI water NCDA&CS Agronomic Division

  12. Calibration - Second • Watts determined at four locations • front right • front left • back right and • back left NCDA&CS Agronomic Division

  13. Determine Power for 210 Watts • Measure initial temp of 1000 ml DI water • Place beaker in the front left section of cavity • Cook 2 minutes at 210 watts • 36% power • Remove and stir then measure final temp • Repeat steps 1-4: • front right, left rear and right rear NCDA&CS Agronomic Division

  14. Calculate the watts for each of these locations and runs T [final]-T [initial] * 35 Calculate the average If the average does ≠ 210 watts OR If the watts of any of the locations is very different from the others Repeat the steps Watts Calculation NCDA&CS Agronomic Division

  15. Determine Power for 390 Watts • Same steps • 49% power • And calculations NCDA&CS Agronomic Division

  16. Quality Control • To verify that the samples have been cooked at the correct power? (210 then 390 watts) • calibrate • adjust • NIST sample NCDA&CS Agronomic Division

  17. That’s It • Any Questions • Thanks NCDA&CS Agronomic Division

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