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Development of a Chemical Stain for Identifying Arsenic-Treated Wood

Development of a Chemical Stain for Identifying Arsenic-Treated Wood. Amy Omae August 18, 2005 Medley, FL. Background. Identification methods for arsenic-treated wood Visual method Augmentation methods XRF, LIBS, AA analysis Arsenic test kits Arsine gas Wipe

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Development of a Chemical Stain for Identifying Arsenic-Treated Wood

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  1. Development of a Chemical Stain for Identifying Arsenic-Treated Wood Amy Omae August 18, 2005 Medley, FL

  2. Background • Identification methods for arsenic-treated wood • Visual method • Augmentation methods • XRF, LIBS, AA analysis • Arsenic test kits • Arsine gas • Wipe • Copper specific stains (PAN indicator) • Alternative treated wood (ACQ, CBA, CC, CDDC) INACCURATE EXPENSIVE HAZARDOUS DAYS OR WEEKS IDENTIFIES COPPER NOT ARSENIC

  3. Background • Similarity of phosphate and arsenate • Colorimetric identification methods • Ascorbic acid • Unable to prevent phosphate interference • Vanadomolybdophosphoric acid • Unable to achieve a noticeable color • Stannous chloride… Phosphate Arsenate

  4. Stannous Chloride Stain • Standard Methods, 1995 • Intended for the detection of phosphate, PO43- • Colorimetric reaction  BLUE PO43- +12(NH4)2MoO4 +24H+(NH4)3PO4•12MoO3 +21NH4+ +12H2O (NH4)3PO4•12MoO3 + Sn2+  (molybdenum blue) + Sn4+ • Interference: Arsenate, AsO43- Phosphate Arsenate

  5. Stannous Chloride Stain • Modifications • Reducing sensitivity to phosphate 1) Ammonium Molybdate 2) Stannous Chloride

  6. Stannous Chloride Stain • Modifications • Reducing sensitivity to phosphate 1) Ammonium Molybdate 2) Stannous Chloride Combined Reagent

  7. Stannous Chloride Stain Reagents Combined Reagents Separated Phosphate Arsenate

  8. Dissolution Method • 20-mL sample vial • 10 mL distilled water • 9 drops combined reagent • 8 parts ammonium molybdate • 1 part stannous chloride • 0.5 g sample (shredded wood or sawdust) • Reaction time: 30-45 minutes • Maximum intensity: ~5 hours

  9. Dissolution Method (4.0 kg/m3) Untreated CC CDDC CBA ACQ Borate CCA • ACZA-treated wood • Ammoniacal Copper Zinc Arsenate • Western U.S. • Maximum intensity: ~2 hours

  10. 4.0 kg/m3 CCA 1h 8m 0s 53m 30s 39m 15s 31m 40s 2h 30m 0s 22m 30s 5h 30m 0s 15m 0s 0m 0s Medium Blue (0.221–0.399) Blue (0.400–1.149) Light Blue (0.071–0.220) Intense Blue (>1.150) Faint Blue (0.025–0.070) None Untreated λ = 690 nm Dissolution Method

  11. Dissolution Method • Field test • Recycled wood

  12. Dissolution Method • Shelf life (6 months; ends August 26, 2005) • Reagents must be stored separately

  13. Other Application Methods • Whole wood application Interference with Untreated Wood

  14. Other Application Methods • Ash • Masking color of ash • Wipes • Simulate human hand • Analyze wipe with dissolution method stannous chloride stain • New wood  Effective; similar reaction time • Weathered wood  Effective; reaction time ~4 hours UNTREATED 4.0 kg/m3 CCA 40 kg/m3 CCA

  15. Future Objectives • Additional field testing on playgrounds • MDL for phosphate and arsenate • Adjust pH to reduce reaction time • Prepare consumer instructions • Submit technical report to:

  16.  Thank you!  Questions?

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