Hydrogen Peroxide, Exercises of Chemistry

Download Hydrogen Peroxide and more Exercises Chemistry in PDF only on Docsity! 1 of 15 Hydrogen Peroxide Method number: 1019 Version: 1.0 Target concentration: 1.0 ppm (1.4 mg/m 3 ) OSHA PEL: 1.0 ppm (1.4 mg/m 3 ) ACGIH TLV: 1.0 ppm (1.4 mg/m 3 ) vapor or mist Procedure: Samples are collected by drawing workplace air through two 25-mm quartz filters, coated with titanium oxysulfate, using personal sampling pumps. Samples are extracted with 10 mL of 1 M H2SO4 and analyzed by spectrophotometry. Recommended sampling time and sampling rate: TWA: 240 min at 1 L/min (240 L) 120 min at 2 L/min (240 L) for vapor and mist short term: 15 min at 2 L/min (30 L) Reliable quantitation limit: TWA: 36.6 ppb (50.8 μg/m 3 ) short-term: 292 ppb (407 μg/m 3 ) Standard error of estimate at the target concentration: 5.8% Special requirements: Samples should be protected from light during shipping and storage. Other chemicals used in the area sampled should be reported to the laboratory and the potential impact on analysis should be considered. Status of method: Fully validated method. This method has been subjected to the established evaluation procedures of the Methods Development Team. January 2016 Michael Simmons Methods Development Team Industrial Hygiene Chemistry Division OSHA Salt Lake Technical Center Sandy UT 84070-6406 2 of 15 1. General Discussion For assistance with accessibility problems in using figures and illustrations presented in this method, please contact OSHA Salt Lake Technical Center (SLTC) at (801) 233-4900. These procedures were designed and tested for internal use by OSHA personnel. Mention of any company name or commercial product does not constitute endorsement by OSHA. 1.1 Background 1.1.1 History In 1977 OSHA issued Method VI-6 for the sampling and analysis of hydrogen peroxide. 1 When using Method VI-6 samples are collected with a midget fritted glass bubbler containing a titanium oxysulfate collection solution and analyzed by spectrophotometry. OSHA next issued ID-126-SG, with samples collected using a midget fritted glass bubbler containing a titanium oxysulfate collection solution and analyzed by differential pulse polarography. 2 In 2000, Christensen et al. demonstrated the use of glass fiber filters impregnated with titanium tetrachloride, with analysis by spectrophotometry, for the sampling of hydrogen peroxide. 3 Hecht et al. then modified the sampler using quartz filters soaked with a solution of titanium oxysulfate in sulfuric acid. 4 Quartz filters coated with titanium oxysulfate are now commercially available and are validated in this method as a replacement to the fritted glass bubbler method. 1.1.2 Toxic effects (This section is for information only and should not be taken as the basis of OSHA policy.) “Inhalation of high concentrations of the vapor or the mist of hydrogen peroxide has caused extreme irritation and inflammation of the nose and throat. Severe systemic poisoning has also caused headache, dizziness, vomiting, diarrhea, tremors, numbness, convulsions, pulmonary edema, unconsciousness and shock.” 5 1.1.3 Workplace exposure Hydrogen peroxide is used in “the bleaching or deodorizing of textiles, wood pulp, hair, fur, and foods; in the treatment of water and sewage; as a disinfectant; as a component of rocket fuels; and in the manufacture of many chemicals and chemical products.” 6 In 2000 the estimated U.S. production of hydrogen peroxide was 7 × 10 5 tons. 7 1 Hydrogen Peroxide (OSHA Method VI-6), 1977. United States Department of Labor, Occupational Safety and Health Administration Web site. http://www.osha.gov/dts/sltc/methods/inorganic/id006/hydrogen_peroxide.html (accessed May 2015). 2 Hydrogen Peroxide (OSHA Method ID-126-SG). United States Department of Labor, Occupational Safety and Health Administration Web site. http://www.osha.gov/dts/sltc/methods/partial/t-id126sg-pv-01-0201-m/t-id126sg-pv-01-0201-m.html (accessed May 2015). 3 Christensen, C. S.; Brødsgaard, S.; Mortensen, P.; Egmose, K.; Linde, S. A. Determination of hydrogen peroxide in workplace air: interferences and method validation. J. Environ. Monit., 2000, 2, pp 339-343. 4 Hecht, G.; Héry, M.; Hubert, G.; Subra, I. Simultaneous Sampling of Peroxyacetic Acid and Hydrogen Peroxide in Workplace Atmospheres. Ann. occup Hyg., 2004, 8, pp 715-721. 5 American Conference of Governmental Industrial Hygienists, Inc. Documentation of the Threshold Limit Values and Biological Exposure Indices, 7th ed.; Cincinnati, OH, 2001; Vol. 2, pp. Hydrogen Peroxide – 1 through Hydrogen Peroxide – 2. 6 American Conference of Governmental Industrial Hygienists, Inc. Documentation of the Threshold Limit Values and Biological Exposure Indices, 7th ed.; Cincinnati, OH, 2001; Vol. 2, pp. Hydrogen Peroxide – 1 through Hydrogen Peroxide – 2. 7 Kirk-Othmer Encyclopedia of Chemical Technology, 4 th ed.; Kroschwitz, J. I., Ex. Ed.; John Wiley & Sons, Inc.: New York, 1993; Vol. 13, pp 981. 5 of 15 Analytical balance capable of weighing at least 0.01 mg. A Mettler Toledo XP205 DeltaRange analytical balance was used in this evaluation. 3.2 Reagents Hydrogen peroxide (H2O2), [CAS no. 7722-84-1], for ultratrace analysis. The hydrogen peroxide solution used in this evaluation was ≥30% TraceSELECT Ultra, for ultratrace analysis, purchased from Sigma Aldrich (product no. 16911, lot no. 05735JH). See Section 4.11 for more information. Titanium(IV) oxysulfate (TiOSO4), [CAS no. 13825-74-6]. The titanium(IV) oxysulfate used in this evaluation was ≥29% Ti (as TiO2) purchased from Sigma Aldrich (product no. 14023, lot no. SZBB2340). Sulfuric acid (H2SO4), [CAS no. 7664-93-9]. The sulfuric acid used in this evaluation was Baker Instra-Analyzed Reagent for trace metal analysis (95.0 – 98.0%) purchased from J.T. Baker. DI water, 18.0 MΩ-cm. TiOSO4/H2SO4 solution. Prepare by adding 3.5 g TiOSO4, 2.5 mL H2SO4, and 40 mL DI water to a 100 mL beaker. Cover beaker with watch glass, place on a hot plate and heat at about 90 °C, swirling occasionally, until solution becomes clear. Remove from hot plate and allow solution to cool to room temperature. Transfer to a 50-mL volumetric flask, rinsing beaker with several milliliters of DI water, and dilute to mark. Solution can be stored in an air-tight container for 6 months. Two molar H2SO4 solution. Prepare by adding 55 mL of H2SO4 to a 500-mL volumetric flask containing approximately 400 mL of DI water. Allow solution to cool to room temperature and dilute to mark. 3.3 Standard preparation Immediately before preparing working standards prepare a stock standard by injecting 50 μL of an approximately 30% H2O2 solution into a 10-mL volumetric flask and diluting to mark with DI water. Use the density and concentration of the 30% H2O2 solution provided by the manufacturer. For example: (50 μL × 1.11 mg/μL x 0.308) / 10.0 mL = 1.709 mg/mL of H2O2 [Density (1.11 mg/μL) and concentration (30.8%) as reported by the manufacturer of the solution used in validation of method.] Prepare working standards by injecting microliter amounts of the stock standard into a 10-mL volumetric containing 400 μL TiOSO4/H2SO4 solution and 5 mL of 2 M H2SO4. Dilute to the mark with water. For example, to prepare a target level standard of 333.3 µg/sample H2O2, inject 195 μL of the stock standard into a 10-mL volumetric flask containing 400 μL TiOSO4/H2SO4 solution and 5 mL of 2 M H2SO4 then dilute to the mark with water. Prepare new working standards weekly and store in air-tight containers when not in use. Transfer working standards to plastic disposable cuvettes and cap. Inspect the solution in each cuvette for air bubbles and gently tap cuvette if necessary to remove air bubbles. Bracket sample concentrations with standard concentrations. If sample concentration falls outside the range of prepared working standards dilute with 50:50 2 M H2SO4:DI water and reanalyze. 6 of 15 3.4 Sample preparation Open cassette and carefully transfer the two 25-mm coated quartz filters into one clean 20-mL scintillation vial. Add 5 mL of 2 M H2SO4, 5 mL of DI water, and cap tightly. Place scintillation vials in a scintillation rack. Secure rack on a mechanical shaker and shake samples for 60 min. Filter 3 mL of sample, transfer filtrate to a plastic disposable cuvette and cap cuvette. Inspect the sample in cuvette for air bubbles and gently tap cuvette if necessary to remove air bubbles. Analyze as described in Section 3.5. 3.5 Analysis 3.5.1 Analytical conditions Spectrophotometer conditions measurement type: photometry data mode: Abs number of wavelengths: 1 wavelength: 410.0 nm slit width: 2 nm path length: 10.0 mm 3.5.2 A calibration curve can be constructed by plotting response of standards versus micrograms of analyte per sample. Bracket the samples with freshly prepared analytical standards over a range of concentrations. 0 0.2 0.4 0.6 0.8 1.0 1.2 1.4 0 50 100 150 200 250 300 350 400 450 500 550 600 650 700 Mass (g) per Sample A b s o rb a n c e a t 4 1 0 .0 n m Figure 3.5.2. Calibration curve for H2O2 (y = -2.66 × 10 -7 x 2 + 0.0023x – 0.0107). 3.6 Interferences Any compound with a response, or reacts with the titanium oxysulfate to produce a response, at 410 nm is a potential interferent. If any potential interferences were reported, they should be considered before samples are extracted. 7 of 15 E M VE M C  3.7 Calculations The amount of H2O2 per sample is obtained from the appropriate calibration curve in terms of micrograms per sample, uncorrected for extraction efficiency. This amount is then corrected by subtracting the total amount (if any) found on the blank. The air concentration is calculated using the following formulas. 4. Method Validation Where applicable, this method follows validation protocols drawing from the OSHA SLTC “Validation Guidelines for Air Sampling Methods Utilizing Chromatographic Analysis”10. These Guidelines detail required validation tests, show examples of statistical calculations, list validation acceptance criteria, and define analytical parameters. Air concentrations listed in ppm are referenced to 25 °C and 760 mmHg (101.3 kPa). 4.1 Detection limit of the analytical procedure (DLAP) The DLAP is measured as concentration of the analyte detected by the spectrophotometer. Ten analytical standards were prepared with approximately equal descending increments of analyte with the highest standard containing 1.98 µg/mL. This is the concentration that would produce a response approximately 10 times the reagent blank. These standards and the reagent blank were analyzed with the recommended analytical parameters. The data obtained were used to determine the required parameters (standard error of estimate and slope) for the calculation of the DLAP. Values of 0.0196 and 0.0016 were obtained for the slope and standard error of estimate respectively. The DLAP was calculated to be 0.24 µg/mL. 10 Eide, M.; Simmons, M.; Hendricks, W. Validation Guidelines for Air Sampling Methods Utilizing Chromatographic Analysis, 2010. United States Department of Labor, Occupational Safety & Health Administration Web site. http://www.osha.gov/dts/sltc/methods/chromguide/chromguide.pdf (accessed December 2013). r MM V M CV C  where CV is concentration by volume (ppm) VM is 24.46 (molar volume at NTP) CM is concentration by weight (mg/m 3 ) Mr is molecular weight of H2O2 (34.01 g/mol) where CM is concentration by weight (mg/m 3 ) M is micrograms per sample V is liters of air sampled EE is extraction efficiency in decimal form 10 of 15 A low humidity storage test for H2O2 was performed by sampling a dynamically generated controlled test atmosphere using the recommended sampling parameters. The concentration of H2O2 in the test atmosphere was the target concentration (1.06 ppm or 1.48 mg/m 3 ), and the relative humidity was 8.3% at 21 C. Nine storage samples were prepared. Three samples were analyzed on the day of generation. Six samples were protected from light exposure and stored at ambient temperature (about 21 C). At 7 day intervals three samples were selected and analyzed. Sample results are not corrected for extraction efficiency. A low humidity test, with samplers exposed to light during storage, was performed by sampling a dynamically generated controlled test atmosphere using the recommended sampling parameters. The concentration of H2O2 in the test atmosphere was the target concentration (1.07 ppm or 1.49 mg/m 3 ), and the relative humidity was 9.0% at 21 C. Nine storage samples were prepared. Three samples were analyzed on the day of generation. Six samples were stored on a lab bench at ambient temperature (about 21 C) with no protection from light exposure. At 7 day intervals three samples were selected and analyzed. Sample results are not corrected for extraction efficiency. A low humidity test, with samplers exposed to light during storage, was performed by sampling a dynamically generated controlled test atmosphere using the recommended sampling parameters. The concentration of H2O2 in the test atmosphere was the target concentration (1.05 ppm or 1.46 mg/m 3 ), and the relative humidity was 9.6% at 21 C. Nine storage samples were prepared. Three samples were analyzed on the day of generation. Six samples were stored in a drawer at ambient temperature (about 21 C) but were not covered. At 7 day intervals three samples were selected and analyzed. Sample results are not corrected for extraction efficiency. As shown above there is a reduction in recoveries when samples are exposed to light during storage, but when carefully protected the samples are stable. Based on these results it is recommended that samples be wrapped in aluminum foil after sampling. Sampling at low humidity did not affect storage stability. 4.5 Precision (overall procedure) The precision of the overall procedure at the 95% confidence level is obtained by multiplying the overall standard error of estimate by 1.96 (the z-statistic from the standard normal distribution at the 95% confidence level). Ninety-five percent confidence intervals are drawn about the regression lines in the storage stability figure shown in Section 4.4. The precision of the overall procedure at the 95% confidence level for the 18-day storage test (at the target concentration) is 11.4%. It was obtained from the overall standard error of estimate (5.84%) of the data shown in Figure 4.4.1. It contains an additional 5% for sampling pump error. Table 4.4.2 Low Humidity Ambient Storage Test for H2O2 with Samples Protected from Light time (days) storage recovery (%) 0 7 14 102.2 99.7 102.1 103.9 100.0 102.8 102.6 100.8 100.7 Table 4.4.3 Low Humidity Ambient Storage Test for H2O2 with Samples Exposed to Light (Bench Top Storage) time (days) storage recovery (%) 0 7 14 104.5 96.3 94.9 105.1 95.6 95.4 104.6 95.2 94.1 Table 4.4.4 Low Humidity Ambient Storage Test for H2O2 with Samples Exposed to Light (Drawer Storage) time (days) storage recovery (%) 0 7 14 103.0 98.4 94.8 104.8 99.1 94.7 103.8 98.4 93.9 11 of 15 The recovery of H2O2 from samples used in an 18-day storage test remained above 99.2% when stored at 21 C and protected from light exposure. 4.6 Reproducibility Six samples were prepared by sampling a dynamically generated controlled test atmosphere similar to that used in the collection of the storage samples. The concentration of H2O2 in the test atmosphere was the target concentration (0.996 ppm or 1.38 mg/m 3 ), and the relative humidity was 79% at 22 °C. The samples were submitted to the OSHA Salt Lake Technical Center for analysis. The samples were analyzed after being stored for 30 days at 21 °C. No sample result for H2O2 had a deviation greater than the precision of the overall procedure determined in Section 4.5. 4.7 Sampler capacity Sampler capacity was tested by sampling a dynamically generated controlled test atmosphere containing H2O2 at two times the target concentration (2.03 ppm or 2.83 mg/m 3 ) and 80% relative humidity at 22°C. The samples were collected at 1 L/min. A second sampler was placed in a sampling train behind the first sampler. The percentage of the amount found on the second sampler in relation to the concentration of the test atmosphere was defined as breakthrough. There was no significant (˂5%) breakthrough observed after 538 min of testing. This is equivalent to an air volume of 538 L. The recommended air volume for sampling at 1 L/min is 240 L. Sampler capacity was also tested by sampling a dynamically generated controlled test atmosphere containing H2O2 at two times the target concentration (2.11 ppm or 2.94 mg/m 3 ) and 81% relative humidity at 21°C. The samples were collected at 2 L/min. A second sampler was placed in a sampling train behind the first sampler. There was no significant (˂5%) breakthrough observed after 330 min of testing. This is equivalent to an air volume of 660 L. The recommended air volume for sampling at 2 L/min is 240 L. 4.8 Extraction efficiency and stability of extracted samples The extraction efficiency is affected by the extraction solution, the sampling medium, and the technique used to extract the samples. Other reagents and techniques than described in this method can be used provided they are tested as specified in the validation guidelines. 12 Extraction efficiency The extraction efficiency was determined by liquid-spiking four samplers at each concentration level with H2O2. These samples were stored overnight at ambient temperature and then analyzed. The overall mean extraction efficiency, over the working range of 0.1 to 2 times the target concentration, was 99.3%. The extraction efficiency at the RQL was 99.8%. The presence of water had no significant effect on extraction efficiency. The extraction efficiencies 12 Eide, M.; Simmons, M.; Hendricks, W. Validation Guidelines for Air Sampling Methods Utilizing Chromatographic Analysis, 2010. United States Department of Labor, Occupational Safety & Health Administration Web site. http://www.osha.gov/dts/sltc/methods/chromguide/chromguide.pdf (accessed December 2013). Table 4.6 Reproducibility Data for H2O2 theoretical (μg/sample) recovered (μg/sample) recovery (%) deviation (%) 339 325 322 326 335 326 311 302 296 304 316 307 91.7 92.9 91.9 93.3 94.3 94.2 -8.3 -7.1 -8.1 -6.7 -5.7 -5.8 12 of 15 for the RQL and the wet samplers are not included in the overall mean. Wet media were prepared by sampling humid air (80% relative humidity at 21 °C) for 240 min at 1 L/min. The data obtained are shown in Table 4.8.1. Table 4.8.1 Extraction Efficiency of H2O2 level sample number × target concn µg per sample 1 2 3 4 mean 0.1 34.2 101.3 103.9 101.4 100.0 101.6 0.25 85.5 99.5 98.4 102.1 100.5 100.1 0.5 170.9 97.9 97.9 98.4 98.9 98.3 1.0 341.9 98.0 98.3 98.0 98.8 98.3 1.5 512.8 99.3 98.8 98.4 99.4 99.0 2.0 683.8 97.5 98.6 97.3 99.2 98.2 RQL 12.3 101.8 101.8 99.1 96.4 99.8 1.0 (wet) 341.9 98.5 97.9 98.3 98.3 98.3 Stability of extracted samples The stability of extracted samples was investigated by reanalyzing dry target concentration samples at 1 and again at 7 days after the initial analysis. These samples were stored in capped cuvettes at ambient temperature and fresh analytical standards were prepared and used each day. Results are presented as percent of the original analysis. Table 4.8.2 Stability of Digested Samples at Target Concentration recovery (%) storage (days) 1 2 3 4 mean 1 101.3 101.0 101.2 101.2 101.2 7 103.9 106.6 103.6 104.7 104.7 4.9 Sampling interferences Retention Retention was tested by sampling a dynamically generated controlled test atmosphere containing two times the target concentration (2.00 ppm or 2.78 mg/m 3 ) of H2O2 at 80% relative humidity and 22 C. The test atmosphere was sampled with six samplers at 1 L/min for 60 min. Sampling was discontinued and the samplers were separated into two sets of 3 samplers each. The generation system was flushed with contaminant-free air. Contaminant-free air is laboratory conditioned air at known relative humidity and temperature but without any added chemicals except water. One set of samplers was set aside (first set). Sampling was resumed with the second set of three samples and contaminant-free air at 80% relative humidity and 22C at 1 L/min for 180 min. All six samplers were analyzed and the data obtained are shown in Table 4.9. Table 4.9.1 Retention of H2O2 recovery (%) set 1 2 3 mean first 108.0 102.7 102.9 104.5 second 102.0 101.9 103.0 102.3 second/first 97.9