Development of a Diffusive Sampler for Vapor-Phase Hydrogen Peroxide (VHP)

Transcription

1 Development of a Diffusive Sampler for Vapor-Phase Hydrogen Peroxide (VHP) C.R. (Gus) Manning, PhD, CIH Assay Technology, Inc. Livermore, CA

2 Hydrogen Peroxide (VHP = Vapor Phase Hydrogen Peroxide) H 2 O 2 = HO-OH Consumer Pharmaceutical Antimicrobial Traditional Uses: Industrial Oxidizing Agent Aerospace Propellant (rocket fuel)

3 H 2 O 2 Safety Concerns (pre-2000) Traditional Uses of H 2 O 2 Used Low concentrations Well-contained Small number of exposed employees

4 H 2 O 2 Safety Concerns (post-2000) New Application! Medical Sterilizing Agent Sterilizing Agent with lower risk profile than Ethylene Oxide Glutaraldehyde Formaldehyde

5 Hydrogen Peroxide Common substance with unusual properties I I have a bottle in the bathroom. How bad can it be?

6 H 2 O 2 Safety Concerns (new) Medical Sterilization performed in 1000 s of hospitals, surgical centers, and medical mfg facilities Sterilization at high vapor levels (ca. 500 ppm) > 25,000 employees exposed REL = TLV = PEL = 1.0 ppm

7 Pre-Existing VHP Sampling Methods

8 Area Sampling Ion-Mobility Spectrometer Interference by methanol, bleach, SO 2 Cost = $50,000 Infra Red Spectrometry Interference by Water FTIR can avoid water interference Cost = $65,000 Honeywell TLD-1 1 (Chem Key) Paper tape reading device Colorimetric for H 2 O 2 Measures 0.1-3ppm Cost = $4,500

9 Personal Sampling in breathing zone OSHA ID-006 & ID126SG reaction TiOSO 4 + H 2 O 2 H 2 TiO 3 SO 4 yellow Air from Breathing Zone Sampling Pump Impinger Solution TiOSO 4 in dil. H 2 SO 4

10 OSHA ID-006 H 2 TiO 3 SO 4 - yellow solution absorption maximum at 410 nm analyze by UV Spectrophotometry H2O2 Calibration Curve Optical Absorbance y = x R 2 = H2O2 Found (microgram)

11 OSHA ID-125SG H 2 TiO 3 SO 4 - yellow solution highly oxidized species analyze by Pulse Polarography 10 Current (µamp) applied Volts vs SCE

12 Goals of Study Design Personal Monitoring Badge Cost-effective & convenient Generate VHP (vapor phase H 2 O 2 ) x PEL or higher PEL = 1 ppm Compare Badges versus Impingers Controlled Exposure Chamber

13 Development Approach Incorporate TiOSO 4 reagent in a solid phase Fiberglass Cellulose Silica Gel Incorporate solid phase into a Personal Monitoring Badge

14 Prototype H 2 O 2 Sampler Sampler Body (with snap cap) Sampling Grid (low SR) Sampling Grid (high SR) Spacer Wafer (treated with TiOSO4)

15 Optimal H 2 O 2 Sampler Side 1 of Sampler Body (with Sampling Grid) Collector Strip (treated with TiOSO4) Side 2 of Sampler Body (with Sampling Grid)

16 Badge and Impinger (Hydrogen Peroxide)

17 Generating H 2 O 2 Vapor for Testing (issues) Not available in gaseous form Available as a 3-50% 3 solution in water Strongly attracted to water

18 Hydrogen Peroxide Interactions H 2 O 2 b.p. 150 o C decomposition H 2 O + ½ O 2 b.p. 100 o C 50% H 2 O 2 Solution in water boils at 114 o C Heating

19 H 2 O 2 Generation Humidity Effects %RH 85%RH 50% RH 100% Efficiency H2O2 Concn (ppm) H2O2 Added (mg/min)

20 VHP Vapor Pressure is Limited at High Humidity Saturated VHP Concn % Relative Humidity

21 Vaporization Methods for Liquids Equilibration with Heated Liquid Air or N2 stream passes over heated liquid Liquid Injection through Heated Needle directly into test air stream Liquid Injection into Heated Chamber chamber located in test air stream

22 Test Air Passes Over Heated Liquid Test Air with Contaminant Concentration Test Air from Miler-Nelson Generator Liquid to be Vaporized (heated) Temp Sensor Heating Block Feedback - + Applied Voltage Highest Concentration Attainment (> 1,000 ppm) Liquid components separate by volatility (boiling point)

23 Heated Needle Vaporization Liquid to be Vaporized (metered from syringe pump) Applied Voltage Injection Needle Feedback Temp Sensor Resistance Wire (NiCr) Septum Test Air with Contaminant Concentration Test Air from Miler-Nelson Generator Vaporization Chamber Vaporizes 100% of liquid (does not separates components) Lowest Concentration Attainment (1-50 ppm)

24 Heated Chamber Vaporization Liquid to be Vaporized (metered from syringe pump) Injection Needle Test Air with Contaminant Concentration Septum Test Air from Miler-Nelson Generator Heating Mantle Vaporization Chamber (3-neck flask) Temp Sensor - + Applied Voltage Higher Concentration Attainment than Heated Syringe (to 500 ppm) Does not separate liquid components (if careful)

25 Accuracy of VHP Challenge Challenge Level vs Testing Time 250 VHP Challenge Level (ppm) Elapsed Time (hr)

26 Hydrogen Peroxide Evaluation of Personal Samplers

27 MNR Atmosphere Generator Concept of Side-by by-side Sampler Comparison Chemical Vapor Generator Air Intake ChemDisk ChemDisk Sampling Tube Sampling Tubes Sampling Pump ChemDisk Diffusive Samplers Exhaust Fan

28 Evaluating Air Samplers (schematic)

29 H 2 O 2 Analysis Analysis (low levels) OSHA ID 006 Impinger Sampling Rate = 1 L/min; Sampling Time = 40 min Optical Abs (410 nm) VHP Concn (ppm)

30 H 2 O 2 Analysis Personal Monitoring Badge Sampling Rate = 105 ml/min; Sampling Time = 4 hour Optical Abs (410 nm) VHP Concn (ppm)

31 Summary Vapor Phase Hydrogen Peroxide (VHP) was generated by injecting 50% aqueous H 2 O 2 solution into flowing system. Challenge Levels from ppm Flow Rates from L/min Low Levels of Vapor Phase Hydrogen Peroxide were monitored side-by by-side using OSHA ID 006 and a Personal Badge using similar chemistry. Operating range ppm

32 Conclusion Diffusive Samplers (Personal Monitoring Badges) based on TiOSO 4 chemistry perform similarly to the OSHA ID 006 method, but with increased convenience. Eliminate need for Glass Impingers Operating range ppm

33 Finis