Ammonia Backup Data Report (ID-188)

OSHA Method ID-188 Backup | Revised June 1990

The tables on this page are best viewed on a desktop, notebook, or tablet computer.

This backup report was revised June, 1990

Introduction

The general procedure for the air sample collection and analysis of ammonia is described in OSHA Method No. ID-188 (10.1). The validation of this method examines the use of a glass sampling tube containing 500 mg of carbon bead impregnated with sulfuric acid (CISA). Sampling tubes were made in-house and also obtained from Supelco Inc. (Bellefonte, PA). During the validation these commercial tubes became available and were used for experiments not completed. The in-house and commercially prepared tubes are identical except the tube manufactured by Supelco has a 250-mg backup section. The in-house tubes were prepared using the method of Bishop, Belkin and Gaffney (10.2) with a minor modification. A dilute sulfuric acid pre-wash of the carbon bead sorbent was performed when preparing the in-house tubes.

This method was evaluated when the OSHA Time Weighted Average (TWA) Permissible Exposure Limit (PEL) for ammonia was 50 ppm. As of this writing, the OSHA Final Rule Limit for exposure to ammonia is now a Short-Term Exposure Limit (STEL) of 35 ppm.

The method has been validated for TWA samples using sampling flow rates of about 0.10 liter per minute (L/min) and sampling times of 3 to 4 h. An evaluation of four types of ammonia detector tubes was carried out simultaneously with the method validation. The results of the detector tube study are reported in OSHA Product Evaluation No. 7 (10.3). A preliminary test was also conducted on ammonia dosimeter tubes obtained from Wilson Safety Products (Reading, PA). The testing of the dosimeter tubes was discontinued since these tubes could not measure concentrations above 50 ppm ammonia during the experiments.

The validation of OSHA Method No. ID-188 (10.1) consisted of the following experimental protocol:

  1. Analysis of spiked samples.
  2. Analysis of dynamically generated samples having concentrations of approximately 0.5, 1, and 2 times the TWA PEL. Test atmospheres were generated using 50% RH and 25°C.
  3. Collection efficiency and breakthrough studies of the CISA sampling tubes.
  4. Determination of the storage stability of ammonia collected with CISA tubes.
  5. Determination of any variation in results when sampling at high and low RH.
  6. Comparison of the ion chromatographic method with the ISE method for the determination of ammonia in workplace atmospheres.
  7. Determination of the qualitative and quantitative detection limits.
  8. Collection and analysis of ammonia samples employing Supelco tubes and comparison with tubes produced in-house.

A generation system, shown in Figure 1, was used for simultaneous testing of detector tubes and continual sampling devices. All generations of ammonia test atmospheres, and hence all experiments, with two exceptions, were performed using the apparatus shown in Figure 1. The analysis and detection limit studies did not use test atmospheres; these samples were spiked with solutions of ammonium sulfate.

Ammonia Gas Concentration

Ammonia in nitrogen (certified standard, 0.99% ammonia, Air Products Co., Long Beach, CA) was used as the contaminant source. The concentration of ammonia in the cylinder was verified by the following technique:

  1. The undiluted gas stream from the cylinder was sampled with a gas syringe and then injected into 0.1 N sulfuric acid contained in septum-capped vials.
  2. These samples were analyzed for ammonia with an Orion Model 9512 Ammonia Ion Specific Electrode (ISE) and an Orion Model EA940 IonAnalyzer (10.4). The results are shown below:

 Theoretical NH3     Found NH3 (µg)     Recovery %     SD     CV 
Spikes (µg):
60.5 56.8 93.9
60.5 59.8 99.8
60.5 54.2 89.6
60.5 50.2 83.0
6.70 0.073
Average 91.3

The ammonia aliquot results were compared to the manufacturer's stated concentration value. The average spiked sample recovery was 91.3% of the stated value and the CV was 0.073. The manufacturer's stated value was used for all calculations. The lower recoveries were considered to be due to variability in analysis and not due to a change in the stated cylinder concentration. The ISE method has displayed a significant amount of variability in results and slightly lower than expected recoveries. Internal quality control data and results of ISE samples generated during this evaluation are evidence of this variability and decreased recovery when using the ISE method.

Generation System Components

The ammonia gas was mixed, using a glass mixing chamber, with filtered, tempered air. A flow, temperature and humidity control system (Miller-Nelson Research Inc., Model HCS-301) was used to condition the diluent air for mixing. Moisture and other contaminants were removed from the diluent air by using a charcoal, molecular sieve and Drierite filtering system. A Teflon sampling manifold and connections were attached to the mixing chamber. Diluent air flow was determined using a dry test meter (Singer Co., Model No. DTM 115) before, during, and after each experiment. Ammonia flow rates were controlled by a mass flow controller (Tylan Model FC 260), and were measured before and after each experiment with a soap bubble flow-meter. During each experiment the flow rate was monitored using the readout (LED display) for the mass flow controller.

Sample Collection

Air samples were collected from the manifold using Du Pont Model P125 pumps (Du Pont Co. Wilmington, DE) calibrated at flow rates of about 0.1 L/min for all generation experiments. Specific sampling times are mentioned in the procedures for each experiment.

Sample Analysis

Samples, blanks and prepared standards were analyzed for ammonium ion by ion chromatography (10.1). Analyses and data reduction were performed using a Dionex Model 2010i Ion Chromatograph interfaced to a Hewlett-Packard 3357 Laboratory Automation System. An IBM AT Personal Computer with AutoIon 400 software was used during later analyses. All sample results were calculated using a concentration-response curve with peak areas used for signal measurement. Sample results were statistically examined for outliers and homogeneous variance. Possible outliers were determined using the American Society for Testing and Materials (ASTM) test for outliers (10.5). Homogeneity of the coefficients of variation was determined using the Bartlett's test (10.6).

  1. Analysis (Spiked Samples)


    Procedure: Twenty-one spiked samples (7 samples at each test level) were prepared and analyzed. The spiked concentrations correspond to approximately 0.5, 1 and 2 times the TWA PEL when using a 24-L air volume. Recoveries represent the desorption efficiency and also provide precision and accuracy data for the analytical portion of the method.

    • 1.1. Three sets of spiked samples were prepared using the following procedure:

    • 1.1.1. A concentrated solution of ammonium sulfate [(NH4)2SO4] was prepared by dissolving a weighed amount of (NH4)2SO4 ("Baker Analyzed" Reagent, ACS) in deionized water (DI H2O).

    • 1.1.2. Aliquots of this solution were injected into in-house prepared sorbent tubes using a calibrated micropipette.

    • 1.1.3. Sufficient (NH4)2SO4 solution was added so that the tubes in each set would contain an amount of ammonia expected after collection from atmospheres at approximately 0.5, 1, and 2 times the PEL, respectively.

    • 1.1.4. The spiked tubes were allowed to stand overnight at room temperature.

    • 1.2. The carbon beads were removed from each tube and desorbed with DI H2O and analyzed as mentioned in the method (10.1). The glass tube was also rinsed with DI H2O. Blanks were also prepared in the same fashion.

    • Results: The results are given in Table 1. All data were used except for one sample (2 x TWA PEL) which appeared contaminated with an unknown substance and gave baseline irregularities during analysis. All results passed the outlier and Bartlett's tests and were pooled. The analytical coefficient of variation (CV1) was 0.031 and recovery was 99.7%.

  2. Sampling and Analysis


    Procedure: Twenty-four samples were taken from the dynamic generation system mentioned in the Introduction. Sample results from the dynamic system provide the overall error and precision of the sampling and analytical method. Overall error (OE) should be within ±25% and is calculated using the following equation (10.7):

    Overall Error = ± [|mean bias| + 2CVT] x 100%

    • 2.1. Samples were collected from gas streams (50% RH and 25°C) containing ammonia at approximately 0.5, 1, and 2 times the TWA PEL.

    • 2.2. In-house prepared tubes containing beaded activated carbon with 5% (by weight) sulfuric acid as described in the method (10.1) and similar tubes prepared by Supelco were taken side-by-side.

    • 2.3. Two to four samples were collected during each generation experiment. Three to four samples were desired, but in several cases pump failure ended the determination.

    • 2.4. Collection rates were about 0.1 L/min. Collection times were 3 to 4 h.

    • 2.5. Samples were desorbed with 50 or 100 mL of DI H2O and analyzed.

    • Results: Sample results are listed in Table 2 and are only for the in-house tubes. Supelco tube results are similar. The in-house tube samples collected at 50% RH (Table 2) show good precision and accuracy. The total coefficient of variation (CVT) was 0.050 and the OE (total) was ±10.9%. Bias was less than 1%.

  3. Collection Efficiency and Breakthrough Studies

    • 3.1. Collection Efficiency:

      Procedure: Test atmospheres were generated and samples were taken to measure the sorbent collection efficiency at the upper concentration limit of the validation.

      • 3.1.1. A determination of the collection efficiency was performed using five Supelco tubes in which ammonia at 2 times the TWA PEL was collected. Two samples were collected at 30% and three samples at 80% RH. Samples were taken for approximately 200 min. The amounts of ammonia collected in the first and second sections of the tubes were determined.

      • 3.1.2. The collection efficiency was calculated by dividing the amount collected in the first section by the total amount of ammonia collected in the first and second sections.

      • Results: The results are given in Table 3. The collection efficiency was 100%. No ammonia was detected in the backup sections. The results indicate that the collection efficiency is excellent.

    • 3.2. Breakthrough:

      Procedure: Samples were generated at a concentration greater than the validation level to determine the extent of breakthrough from the first solid sorbent section into a second section.

      • 3.2.1. The possibility of breakthrough of ammonia during sampling was examined by collecting six samples at approximately 5 times the TWA PEL for 335 min, using Supelco tubes. Generation conditions were 50% RH and 25°C.

      • 3.2.2. The main sections were each desorbed in 250 mL of DI H2O. To facilitate detection of any breakthrough, the backup sections were each desorbed in 10 mL of DI H2O.

      • Results: The results given in Table 3 show the overall recovery was 94.6% and the CV was 0.032. Ammonia was not detected in the backup sections, indicating no evidence of breakthrough.

  4. Storage Stability of Ammonia Samples Collected on CISA

    Procedure: A long-term evaluation of sample media stability was done to assess any potential problems if delays in sample analyses occur.

    • 4.1. Supelco tube samples were collected from a gas stream adjusted to 50% RH, 25°C and an ammonia concentration of approximately 50 ppm.

    • 4.2. A collection time of about 3.5 h was used.

    • 4.3. Samples were capped and stored for various periods up to 29 days before preparation and analysis. Samples were stored in a desk drawer.

    • Results: The results given in Table 4 indicate a slight loss of ammonia (<10%) during approximately one month of storage. The slight decrease in recovery does not appear detrimental to the overall accuracy of the method. Samples can be stored for at least 29 days before analysis.

  5. Humidity Tests

    Procedure: Samples were collected at high (80%) and low (30%) RH using similar conditions mentioned in Section 2, where samples were collected at 50% RH. Supelco and in-house tubes were taken side-by-side. Sample recoveries for these three humidity levels were examined to determine any significant differences.

    Results: The low and high RH results are given in Table 5; the 50% RH results are shown in Table 2. Results listed are for in-house tubes only. Supelco tubes gave similar results. Sampling at different humidities displayed no apparent effect on recovery. An analysis of variance (F test) was performed on the data to determine any significant difference among or within the different humidity groups. Variance at each concentration level (0.5, 1, and 2 times the TWA PEL) was compared across the 3 humidity levels (25-30, 50, and 80% RH). The variance among and within the different concentration groups gave acceptable calculated F values with the exception of the data at the TWA PEL. At this concentration only three samples were collected at the low humidity level; these recoveries were lower than expected and appeared to be due to a dilution problem during ammonia generation. The reference method bubbler samples taken side-by-side also gave lower than expected results. The test at low RH was one of the first experiments conducted. This anomalous behavior was not observed for any of the other data.

    The recoveries across the 3 different humidity levels were also considered. No evidence of any significant constant increase or decrease in average recovery was apparent when generation data are compared at different humidity levels. Therefore, the data indicate no apparent humidity effect on recovery.

  6. Method Comparison

    Procedure: The CISA sampling and ion chromatography (IC) analytical method was compared to a reference method to determine if any significant disagreement existed between the two methods. The bubbler sampling and ISE analytical method (10.4) was chosen as the reference method. The comparison was conducted as described below:

    • 6.1. Side-by-side samples of CISA tubes (both commercial and in-house tubes) and bubblers containing 0.1 N sulfuric acid were collected at 25°C and 25-30%, 50%, and 80% RH. Du Pont Model P4000 pumps were used to collect bubbler samples. Bubbler collection rates were 1 L/min and collection times were 3 to 4 h. The bubbler solutions were analyzed using an Orion Model 9512 Ammonia ISE and an Orion Model EA940 IonAnalyzer (10.4).

    • 6.2. The CISA tubes were sampled and analyzed using the procedures described in the Introduction.

    • Results: The results are given in Table 6. Each CISA and bubbler sample value listed is an average value of two to four samples. Each comparison is for samples collected side-by-side. Statistical treatments are also given. Each sample comparison is based on the averages of the CISA and bubbler samples collected side-by-side. Linear regression comparisoncalculations are also given. The results of the two methods show the CISA sampling and corresponding IC analytical method has an overall positive bias of approximately 7% (slope = 1.07 ± 0.0387) when compared to the bubbler method. Complete listings of individual CISA and bubbler sample results are given in the Appendix.

  7. Analytical Detection Limits

    Procedure: The qualitative detection limit for the analysis of ammonia by IC was calculated using the Rank Sum Test (10.8). A modification or derivation of the International Union of Pure and Applied Chemistry (IUPAC) detection limit equation (10.9) was used to determine the quantitative detection limit. At the sensitivity level tested, blank readings and the standard deviation of the blank were equal to zero. The lack of a blank signal does not satisfy a strict interpretation of the IUPAC detection limit when using the equation shown in Table 7. The quantitative detection limit for this method is calculated using the standard deviation of a standard below the range of the expected detection limit as a substitute for the blank readings. The procedure used for sample preparation to determine detection limits is discussed below:

    • 7.1. Low concentration ammonia samples were prepared from an ammonium chloride solution (1,000 µg/mL as NH3). The sample concentrations were 0.05, 0.1, 0.2, and 0.5 µg/mL ammonia.

    • 7.2. All solutions were made in 0.005 N sulfuric acid. This is the concentration expected when a typical 500-mg section of acid-treated carbon beads from a sample tube is desorbed with 100 mL of DI H2O.

    • 7.3. A blank sample was prepared containing the same sulfuric acid concentration as the ammonia samples.

    • 7.4. Samples were analyzed by IC with a 50-µL sample loop and 30-microsiemens detector setting.

    • Results: The qualitative and quantitative detection limits (Table 7) are 0.20 and 0.50 µg NH3/mL solution, respectively. Using a 24-L air volume and a 50-mL sample volume, the qualitative limit is 0.60 ppm and the quantitative limit is 1.5 ppm ammonia in air. For a 7.5-L air sample, these limits are 1.9 and 4.8 ppm, respectively.

  8. Collection of Ammonia Samples - Supelco Tubes

    Procedure: Experiments were done with in-house sampling tubes and tubes prepared by Supelco. Side-by-side sampling at varied humidity and concentration levels was performed to compare both tubes. Recoveries were compared and a t-test was used to determine if any significant difference in results existed between the two tubes (10.10).

    Results: The results are shown in Table 8. Separate Supelco tube results are also shown in Table 8. The results indicate the two different sets of tubes compare well with each other in their ability to collect and retain ammonia. A t-test (10.10) showed no significant difference between recoveries for the two different sets of tubes.

    The backup sections of the Supelco tubes were also analyzed. All backup results were non-detected when the samples were analyzed shortly after desorption. A very small peak eluting at the same time as ammonia developed after solutions stood for 1 week.

  9. Conclusions

    The sample determinations shown in Tables 1 and 2 are well within NIOSH or OSHA accuracy and precision guidelines (10.6, 10.7). Collection efficiency, breakthrough, and storage stability are adequate. A humidity effect was not noted. The comparison of the bubbler with the IC method showed a positive linear regression slope of 1.07. This is to be expected since overall recoveries of the bubbler method were about 9% lower than expected (theoretical) and IC sample recoveries exhibited minimal bias. The sampling and analysis data for bubbler samples (three different RH and concentration levels) gave an overall recovery of 91.0% and a CV of 0.091. In general, the lowest recoveries for the bubbler samples were measured during preliminary experiments before improvements were made in the ISE procedure. Results for all samples taken and analyzed by IC or ISE are shown in the Appendix.

    Detection limits are adequate for 4-h exposure determinations. For STEL measurements, larger sample volumes will need to be taken over the 15-min sampling period. It is recommended to use 0.5 L/min for STEL assessments (total air volume = 7.5 L). although no STEL experiments were performed during this evaluation, a literature reference (10.2) experiment conducted at a sampling rate of 0.5 L/min for 12 min at a concentration of 25 ppm indicated no detectable breakthrough. The experimenters also indicated the theoretical capacity of the sampling tube is 8.5 mg ammonia.

    The method for collecting ammonia with CISA tubes and analysis by IC is a precise and accurate method for the determination of ammonia in workplace atmospheres.

  10. References

    • 10.1. Occupational Safety and Health Administration Technical Center: Ammonia in Workplace Atmospheres - Solid Sorbent by R.G. Adler (OSHA-SLTC Method No. ID-188). Salt Lake City, UT. Revised 1991.

    • 10.2. Bishop, R.W., F. Belkin and R. Gaffney: Evaluation of a New Ammonia Sampling and Analytical Procedure. Am. Ind. Hyg. Assoc. J. 47: 135-137 (1986).

    • 10.3. Occupational Safety and Health Administration Analytical Laboratory: Ammonia Detector Tubes (PE-7). Salt Lake City, UT. 1987.

    • 10.4. Occupational Safety and Health Administration Analytical Laboratory: OSHA Analytical Methods Manual (USDOL/OSHA-SLCAL Method No. ID-164). Cincinnati, OH: American Conference of Governmental Industrial Hygienists (Pub. No. ISBN: 0-936712-66-X), 1985.

    • 10.5. Mandel, J.: Accuracy and Precision, Evaluation and Interpretation of Analytical Results, The Treatment of Outliers. In Treatise On Analytical Chemistry, 2nd Ed., edited by I. M. Kolthoff and P. J. Elving. New York: John Wiley and Sons, 1978. pp. 282-285.

    • 10.6. National Institute for Occupational Safety and Health: Documentation of the NIOSH Validation Tests by D. Taylor, R. Kupel and J. Bryant (DHEW/NIOSH Pub. No. 77-185). Washington, D.C.: U.S. Government Printing Office, 1977. pp. 1-12.

    • 10.7. Occupational Safety and Health Administration Analytical Laboratory: Precision and Accuracy Data Protocol for Laboratory Validations. In OSHA Analytical Methods Manual. Cincinnati, OH: American Conference of Governmental Industrial Hygienists (Pub. No. ISBN: 0-936712-66-X), 1985.

    • 10.8. National Bureau of Standards: Experimental Statistics by M.G. Natrella (U.S. Dept. of Commerce/NBS Handbook 91). Washington, D.C.: U.S. Government Printing Office, 1966. Chapter 16, pp 8-14.

    • 10.9. Long, G.L. and J.D. Windfordner: Limit of Detection, A Closer Look at the IUPAC Definition. Anal. Chem. 55: 712a-724a (1983).

    • 10.10. Osol, Arthur, ed.: Remington's Pharmaceutical Sciences. Easton, PA: Mack Publishing Co., 1980. pp. 113-114.

  11. Table 1
    Analysis - Spiked NH3 Samples
        (OSHA-TWA PEL)*
    µg NH3
    Taken    		 µg NH3
    Found    		   F/T   n   Mean   Std Dev   CV   AE
    (0.5 x TWA PEL)
    348.0 341.0 0.9799
    348.0 361.0 1.0374
    348.0 342.0 0.9828
    348.0 326.0 0.9368
    348.0 338.0 0.9713
    348.0 339.0 0.9741
    348.0 358.0 1.0287
    7 0.987 0.035 0.035 8.3
    (1 x TWA PEL)
    818.0 841.0 1.0281
    818.0 855.0 1.0452
    818.0 825.0 1.0086
    818.0 828.0 1.0122
    818.0 830.0 1.0147
    818.0 848.0 1.0367
    818.0 872.0 1.0660
    7 1.030 0.021 0.020 7.1
    (2 x TWA PEL)
    1636.0 1540.0 0.9413
    1636.0 1610.0 0.9841
    1636.0 1543.0 0.9432
    1636.0 1674.0 1.0232
    1636.0 1609.0 0.9835
    1636.0 1536.0 0.9389
    6** 0.969 0.034 0.035 10.1
    F/T = Found/Taken
    AE = Analytical Error (± %)
    Bias = -0.003
    CV1 (pooled) = 0.031
    Analytical Error (Total) = ±6.5%
    *   Levels are approximate.
    ** Seven samples were taken; however, one sample was omitted due to baseline irregularities occurring during analysis.
  12. Table 2
    Sampling and Analysis
    (50% RH and 25°C)
        (OSHA-TWA PEL)
    ppm NH3
    Taken    		 ppm NH3
    Found    		   F/T   n   Mean   Std Dev   CV   OE
    (0.5 x TWA PEL)
    34.2 35.1 1.0263
    34.2 36.1 1.0556
    34.2 39.6 1.1579
    30.7 29.8 0.9707
    30.7 29.5 0.9609
    5 1.034 0.079 0.077 18.8
    (1 x TWA PEL)
    45.4 49.2 1.0837
    45.4 46.9 1.0330
    45.4 47.4 1.0441
    50.3 47.0 0.9344
    50.3 47.6 0.9463
    50.3 48.2 0.9583
    50.1 51.2 1.0220
    50.1 50.3 1.0040
    50.1 872.0 1.0180
    9 1.005 0.049 0.049 10.3
    (2 x TWA PEL)
    100.7 94.9 0.9424
    100.7 94.5 0.9384
    100.7 91.9 0.9126
    100.7 97.6 0.9756
    98.5 96.1 0.9835
    98.5 97.8 0.9929
    98.5 93.5 0.9841
    101.8 98.5 0.9676
    101.8 95.9 0.9420
    101.8 1609.0 0.9835
    10 0.957 0.025 0.026 9.4
    F/T = Found/Taken
    OE = Analytical Error (± %)
    Bias = -0.009
    CV2 (pooled) = 0.048
    Overall Error) = ±10.5%
    CVT (pooled) = 0.050
    Overall Error (Total) = ±10.5%
  13. Table 3
    Collection Efficiency and BreakthroughCollection Efficiency - Supelco Tubes50 % RH and 25°C
    Sample ppm Collection ppm Ammonia Found Collection
    No. Ammonia RH (%) Time (min) 1st Sec. 2nd Sec. Eff. (%)
    1 99.5 30 190 87.8 ND 100
    2 99.5 30 190 91.6 ND 100
    3 101.3 80 215 103.4 ND 100
    4 101.3 80 215 105.5 ND 100
    5 101.3 80 215 102.8 ND 100
    Samples were collected at approximately 0.1 L/min flow rate.ND = None detected.        Detection limit = 1.5 ppm NH3
    Breakthrough - Supelco Tubes50 % RH and 25°C
    --------------------------NH3 Found------------------------- NH3 Taken
    µg Air Vol (L) ppm ppm % Recovery
    5189 29.52 252 258
    5012 29.83 241 258
    5218 29.27 256 258
    4968 29.61 241 258
    4802 28.79 239 258
    5426 32.94 236 258
    n = 6 94.6
    mean = 244
    Std Dev = 7.94
    CV = 0.032
    Samples were collected at about 0.1 L/min for 335 min at approximately 5 x TWA PEL. No ammonia was detected in the backup sections.
  14. Table 4
    Storage Stability Test - 1 x TWA PEL, 50 % RH, 25°C
       ---------------------------------------Found---------------------------------------    Taken
    Storage Day µg Air Vol (L) ppm NH3 ppm NH3 % Recovery
    Day 1 705.3 18.70 54.1 53.3
    606.7 16.83 52.4 53.3
    705.3 18.70 54.1 53.3
    n 3
    mean 53.1 100
                                 Std Dev 0.907
    CV 0.017
    Day 5* 672.2 19.26 50.1 53.3
    620.8 16.54 53.9 53.3
    n 2
    mean 52.0 98
    Std Dev 2.69
    CV 0.052
    Day 9 614.0 17.64 50.0 53.3
    609.6 17.50 50.0 53.3
    555.2 17.04 46.8 53.3
    n 3
    mean 48.9 92
    Std Dev 1.85
    CV 0.038
    Day 15 664.4 18.37 51.9 53.3
    609.6 18.29 47.8 53.3
    661.0 19.05 49.8 53.3
    n 3
    mean 49.8 93
    Std Dev 2.05
    CV 0.041
    Day 29 570.4 17.03 48.1 50.1
    536.4 15.98 48.2 50.1
    546.3 16.62 47.2 50.1
    n 3
    mean 47.8 95
    Std Dev 0.551
    CV 0.012
    * One result was deleted due to pump failure.All samples were collected using Supelco tubes. Some of the sampling tubes used had been stored 11 months prior to use. Storage times reported are from the day of collection to the day of analytical preparation.
  15. Table 5
    NH3-IC Humidity Study25-30% RH and 25°C
    (OSHA-TWA PEL)
    ppm NH3
    Taken    		 ppm NH3
    Found
    F/T
    n
    Mean
    Std Dev
    CV
    OE
    (0.5 x TWA PEL)
    34 28.7 0.8441
    34 29.4 0.8647
    34 29.6 0.8706
    34.3 34.0 0.9913
    34.3 31.9 0.9300
    34.3 31.3 0.9125
    24.3 24.4 1.0041
    24.3 23.5 0.9671
    24.3 23.1 0.9506
    9 0.926 0.057 0.062 19.8
    (1 x TWA PEL)
    55.0 44.8 0.8145
    55.0 43.0 0.7818
    55.0 46.5 0.8455
    3 0.814 0.032 0.039 26.4
    (2 x TWA PEL)
    99.6 90.0 0.9036
    99.6 95.0 0.9538
    99.6 94.6 0.9498
    99.6 101.8 1.0231
    99.6 101.4 1.0191
    99.6 100.4 1.0090
    6 0.976 0.048 0.049 12.2
    F/T = Found/Taken
    OE = Overall Error (± %)
    Bias = -0.076
    CV2 (pooled) = 0.055
    Overall Error (Total) = ±18.7%

    80% RH and 25°C
    (OSHA-TWA PEL)
    ppm NH3
    Taken    		 ppm NH3
    Found
    F/T
    n
    Mean
    Std Dev
    CV
    OE
    (0.5 x TWA PEL)
    29.2 27.3 0.9349
    29.2 28.6 0.9795
    29.2 29.0 0.9932
    29.2 22.1 0.9132
    29.2 22.2 0.9174
    29.2 22.3 0.9215
    6 0.943 0.943 0.036 13.0
    (1 x TWA PEL)
    50.2 48.4 0.9641
    50.2 47.0 0.9363
    50.2 49.1 0.9781
    48.1 41.6 0.8649
    48.1 45.6 0.9480
    48.1 40.9 0.8503
    6 0.924 0.053 0.058 19.2
    (1 x TWA PEL)
    101.3 105.8 1.0444
    101.3 98.0 0.9674
    101.3 102.6 1.0128
    3 1.008 0.039 0.038 8.5
    F/T = Found/Taken
    OE = Overall Error (± %)
    Bias = -0.052
    CV2 (pooled) = 0.047
    Overall Error (Total) = ±14.5%
  16. Table 6
    Comparison of Sampling and Analytical Methods
    RH    IC Found (ppm)    ISE Found (ppm)    RR
    25-30%   
    29.2 29.7 0.983
    32.4 28.6 1.133
    23.7 22.9 1.035
    44.8 44.4 1.009
    93.2 88.9 1.048
    101.2 94.4 1.072
    50 %
    36.9 29.1 1.268
    29.7 29.2 1.017
    47.8 44.9 1.065
    47.6 42.5 1.120
    50.9 53.3 0.955
    94.7 88.7 1.068
    95.8 79.3 1.208
    98.2 99.7 0.985
    80%
    28.3 25.3 1.119
    22.2 23.0 0.965
    48.1 46.4 1.037
    42.7 46.2 0.924
    102.1 92.1 1.109
    RR = Relative Recovery = IC Found/ISE FoundEach comparison listed is the average value for all CISA and bubbler samples collected side-by-side for a given experiment.IC samples were collected using CISA tubes and analyzed by ion chromatography.ISE samples were collected using bubblers containing 0.1 N H2SO4 and analyzed by ISE.
    Linear Regression Comparison (all analyses)
          Correlation Coefficient (r) = 0.9890
          Slope (b) = 1.0698
          Intercept (a) = -0.5028
          Std Dev of Slope (Sb) = 0.0387
  17. Table 7
    Determination of Qualitative Detection Limit
    µg/mL NH3
    		     Integrated Area/1000
    BLANK 0, 0, 0, 0, 0, 0
    0.050 0, 0, 0, 0, 0, 0
    0.100 0, 0, 1.202, 1.238, 1.015, 1.314
    0.200 2.314, 2.571, 2.739, 3.033, 2.897, 2.886
    0.500 6.403, 6.934, 7.515, 7.306, 7.975, 8.667
    Rank Sum
    a = 0.01 (two-tailed test)
    n1 = 6 (no. of 0.200 µg/mL determinations)
    n2 = 6 (no. of blank determinations)
    n = n1 + n2 = 12
    R = 69 (sum of ranks for 0.200 µg/mL)
    Rn = n1(n + 1) - R = 9
    R(table) = 23

    Therefore, Rn is not equal to or greater than R(table), and both sample populations are significantly different.Qualitative detection limit = 0.20 µg ammonia per mL, or 10.0 µg in a 50-mL sample volume. This corresponds to a 0.60 ppm ammonia for a 24-L air volume.
  18. TDetermination of Quantitative Detection Limit
    -----------------Ammonia (as NH3) (µg/mL)-----------------

    Sample No.    		      0.100
      PA    		      0.200
      PA    		      0.500
      PA
    1 0 2.314 6.403
    2 0 2.571 6.934
    3 1.202 2.739 7.515
    4 1.238 3.033 7.306
    5 1.015 2.897 7.975
    6 1.314 2.886 8.667

    n 6 6 6
    Mean 0.795 2.740 7.467
    Std Dev 0.623 0.261 0.793
    CV2 0.784 0.095 0.106
    PA = Integrated Peak Area (NH3)/1000
  19. IUPAC Method
    Using the equation: Cld = k(sd)/m
  20. Where:
    Cld = the smallest detectable concentration an analytical instrument can determine at a given confidence level.
    k = 10, thus giving 99.99% confidence that any detectable signal will be greater than or equal to an average blank or low standard reading plus ten times the standard deviation.
    sd = standard deviation of blank or low standard readings.
    m = analytical sensitivity or slope as calculated by linear regression.
  21. Minimum detectable signal:
    Cld = 10(0.623)/0.01238
    Cld = 378 ppb = 0.50 µg/mL
    The quantitative detection limit = 0.50 µg ammonia per mL, or 25 µg in a 50-mL sample volume. This corresponds to a 1.5 ppm ammonia concentration for a 24-L air volume.
  22. Table 8
    Side-by-Side Comparison of Supelco Tubes and In-house Carbon Bead Tubes

    Level
        
    RH
            		 ppm NH3 Found,
    Lab Prep
            		 ppm NH3 Found,
    Supelco
    0.5 x TWA PEL 25 24.4 23.4
    23.5 24.1
    23.1 23.4
    Mean 23.7 23.6
    Std Dev 0.666 0.404
    CV2 0.028 0.017
    ppm taken 24.3 24.3
    % recovered 97.5 97.1
    0.5 x TWA PEL 80 22.1 19.9
    22.2 20.6
    22.3 20.2
    Mean 22.2 20.2
    Std Dev 0.100 0.351
    CV2 0.005 0.017
    ppm taken 24.2 24.2
    % recovered 91.7 83.5
    1 x TWA PEL 30 44.8 48.4
    43.0 47.6
    46.5 48.8
    Mean 44.8 48.3
    Std Dev 1.750 0.611
    CV2 0.039 0.013
    ppm taken 55.0 55.0
    % recovered 81.5 87.8
    1 x TWA PEL 50 51.2 48.1
    50.3 48.2
    51.0 47.2
    Mean 50.9 47.8
    Std Dev 0.473 0.551
    CV2 0.009 0.012
    ppm taken 50.1 50.1
    % recovered 101.6 95.4
    2 x TWA PEL 30 101.8 87.8
    101.4 91.6
    100.4
    Mean 101.2 89.7
    Std Dev 0.721 2.69
    CV2 0.007 0.030
    ppm taken 99.5 99.5
    % recovered 101.7 90.1
    2 x TWA PEL 80 105.8 103.4
    98.0 105.5
    102.6 102.8
    Mean 102.1 103.9
    Std Dev 3.92 1.418
    CV2 0.038 0.014
    ppm taken 101.3 101.3
    % recovered 100.8 102.6
  23. t-test comparison:A student t-test calculation was carried out comparing the individual Supelco tube recoveries with the individual in-house tube recoveries. These samples were taken side-by-side.
             tcalc = 1.129 df = 33                                    

    tTable = 2.750 (p < 0.01) df = 30 (2-tailed)
    tTable = 2.704 (p < 0.01) df = 40 (2-tailed)
    The calculated value for t was less than the Table values. Therefore, the Supelco and in-house tube results are likely from the same population, and compare well with each other.
  24. NH3-Supelco TubesAll RH Levels
    (OSHA-TWA PEL)
    ppm NH3
    Taken    		 ppm NH3
    Found
    F/T
    n
    Mean
    Std Dev
    CV
    OE
    (0.5 x TWA PEL)
    24.3 23.4 0.9630
    24.3 24.1 0.9918
    24.3 23.4 0.9630
    24.2 19.9 0.8223
    24.2 20.6 0.8512
    24.2 20.2 0.8347
    6 0.904 0.076 0.084 26.4
    (1 x TWA PEL)
    55.0 48.4 0.8800
    55.0 47.6 0.8655
    55.0 48.8 0.8873
    50.1 48.1 0.9601
    50.1 48.2 0.9621
    50.1 47.2 0.9421
    6 0.916 0.043 0.047 17.9
    (2 x TWA PEL)
    99.5 87.8 0.8824
    99.5 91.6 0.9206
    101.3 103.4 1.0207
    101.3 105.5 1.0415
    101.3 102.8 1.0148
    5 0.976 0.070 0.072 16.8
    F/T = Found/Taken
    OE = Overall Error (± %)
    Bias = -0.070
    CV2 (pooled) = 0.069
    Overall Error (Total) = ±20.9%

  25. Dynamic Generation System for Production of Ammonia Atmospheres

    Flow Chart - First Tier | From left [Lab Air]→ [Air Purifier]→ | From Right [Lab Water ]→ [Ion Exchange column]→ | Central box to 2nd tier [Flow-Temp-Humidity Control System] | Second Tier | [NH3 Source- Mass Flow Controller]→ Central box to 3rd Tier [Mixing Chamber] | 3rd Tier Central box to Tier 4 [Active Sampling Manifold]→ | 4th Tier [Dry Gas Meter]→ [Exhaust] {Title - Figure 1}

    Figure 1

  26. Appendix
    NH3-IC (All Data) Results
    (OSHA-TWA PEL)
    ppm NH3
    Taken    		 ppm NH3
    Found
    F/T
    n
    Mean
    Std Dev
    CV
    OE
    (0.5 x TWA PEL)
    34.0 28.7 0.8441
    34.0 29.4 0.8647
    34.0 29.6 0.8706
    34.3 34.0 0.9913
    34.3 31.9 0.9300
    34.3 31.3 0.9125
    24.3 24.4 1.0041
    24.3 23.5 0.9671
    24.3 23.1 0.9506
    34.2 35.1 1.0263
    34.2 36.1 1.0556
    34.2 39.6 1.1579
    30.7 29.8 0.9707
    30.7 29.5 0.9609
    29.2 27.3 0.9349
    29.2 28.6 0.9795
    29.2 29.0 0.9932
    24.2 22.1 0.9132
    24.2 22.2 0.9174
    24.2 22.3 0.9215
    20 0.958 0.071 0.075 19.1
    (1 x TWA PEL)
    55.0 44.8 0.8145
    55.0 43.0 0.7818
    55.0 46.5 0.8455
    45.4 49.2 1.0837
    45.4 46.9 1.0330
    45.4 47.4 1.0441
    50.3 47.0 0.9344
    50.3 47.6 0.9463
    50.3 48.2 0.9583
    50.1 51.2 1.0220
    50.1 50.3 1.0040
    50.1 51.0 1.0180
    50.2 48.4 0.9641
    50.2 47.0 0.9363
    50.2 49.1 0.9781
    48.1 41.6 0.8649
    48.1 45.6 0.9480
    48.1 40.9 0.8503
    18 0.946 0.085 0.090 23.3
    (2 x TWA PEL)
    99.6 90.0 0.9036
    99.6 95.0 0.9538
    99.6 94.6 0.9498
    99.5 101.8 1.0231
    99.5 101.4 1.0090
    99.5 100.4 0.9424
    100.7 94.9 0.9384
    100.7 94.5 0.9126
    100.7 91.9 0.9692
    100.7 97.6 0.9756
    98.5 96.1 0.9929
    98.5 97.8 0.9492
    98.5 93.5 0.9676
    101.8 98.5 0.9420
    101.8 95.9 0.9843
    101.8 100.2 1.0444
    101.3 105.8 0.9674
    101.3 98.0 1.0128
    101.3 102.6
    19 0.971 0.038 0.039 10.7
    F/T = Found/Taken
    OE = Overall Error (± %)
    Bias = -0.041
    CV2 (pooled) = 0.071
    Overall Error (Total) = ±18.3%
  27. NH3-ISE (All Data) Results
    (OSHA-TWA PEL)
    ppm NH3
    Taken    		 ppm NH3
    Found
    F/T
    n
    Mean
    Std Dev
    CV
    OE
    (0.5 x TWA PEL)
    34.0 29.0 0.8529
    34.0 30.4 0.8941
    34.3 29.0 0.8455
    34.3 27.4 0.7988
    34.3 29.3 0.8542
    24.3 22.6 0.9300
    24.3 23.0 0.9465
    24.3 22.8 0.9383
    24.3 23.3 0.9588
    34.2 29.4 0.8596
    34.2 29.4 0.8596
    34.2 28.4 0.8304
    30.7 30.3 0.9870
    30.7 28.9 0.9414
    30.7 28.4 0.9251
    29.2 24.6 0.8425
    29.2 25.3 0.8664
    29.2 26.2 0.8973
    24.2 23.2 0.9587
    24.2 23.5 0.9711
    24.2 22.2 0.9174
    24.2 22.3 0.9587
    22 0.902 0.054 0.059 21.7
    (1 x TWA PEL)
    55.0 42.7 0.7764
    55.0 46.3 0.8418
    55.0 45.5 0.8273
    55.0 43.1 0.7836
    45.4 43.9 0.9670
    45.4 51.5 1.1344
    45.4 42.2 0.9295
    45.4 42.0 0.9251
    50.3 42.4 0.8429
    50.3 42.5 0.8449
    50.1 48.2 0.9621
    50.1 53.1 1.0599
    50.1 58.6 1.1697
    50.2 41.8 0.8327
    50.2 48.2 0.9602
    50.2 49.1 0.9781
    48.1 47.6 0.9896
    48.1 44.7 0.9293
    18 0.931 0.112 0.120 31.0
    (2 x TWA PEL)
    99.6 82.1 0.8243
    99.6 96.9 0.9729
    99.6 87.7 0.8805
    99.5 93.6 0.9407
    99.5 92.6 0.9307
    99.5 97.0 0.9749
    100.7 86.6 0.8600
    100.7 90.9 0.9027
    98.5 84.0 0.8528
    98.5 65.5 0.6650
    98.5 88.3 0.8964
    101.8 98.3 0.9656
    101.8 101.2 0.9941
    101.3 97.0 0.9576
    101.3 86.9 0.8578
    101.3 92.3 0.9112
    16 0.899 0.080 0.089 28.0
    F/T = Found/Taken
    OE = Overall Error (± %)
    Bias = -0.090
    CV2 (pooled) = 0.091
    Overall Error (Total) = ±27.2%