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Figure 14. Kl sampling train.
Lag Time-The time interval from a step A. Suggested Performance Specifications
change in input concentration at the infor Atmospheric Analyzers for Hydrocarbons
strument inlet to the first corresponding Corrected for Methane:
change in the instrument output.
Time to 90 Percent Response - The time inRange (minimum) ------ 0.3 mg./m.3 (0-5 terval from a step change in the input con
centration at the instrument inlet to a 0-3 mg./m.3 (0-5 reading of 90 percent of the ultimate rep.p.m.) CH,
corded concentration. Output (minimum)----- 0-10 my. full Rise Time (90 percent)-The interval be
tween initial response time and time to 90 Minimum detectable sen
0.1 p.p.m. THC.
percent response after a step decrease in sitivity.
0.1 p.p.m. CH4.
the inlet concentration. Zero drift (maximum)-- Not to exceed Zero Drift—The change in instrument output
1 percent/24 over a stated time period, usually 24 hours, hours.
of unadjusted continuous operation, when Span drift (maximum)-- Not to exceed the input concentration is zero; usually
1 percent/24 expressed as percent full scale.
Span Drift-The change in instrument outPrecision (minimum)--- +0.5 percent.
put over a stated time period, usually 24 Operational period (mini- 3 days.
hours, of unadjusted continuous operation, mum).
when the input concentration is a stated Operating temperature 5-40° C.
upscale value; usually expressed as percent range (minimum). 10–100 percent. full scale. Operating humidity range
Precision–The degree of agreement between (minimum).
repeated measurements of the same conLinearity (maximum)--- 1 percent of full
centration. It is expressed as the average scale.
deviation of the single results from the B. Suggested Definitions of Performance
Operational Period—The period of time over Specifications: Range—The minimum and maximum meas
which the instrument can be expected to
operate unattended within specifications. urement limits. Output-Electrical signal which is propor
Noise-Spontaneous deviations from a mean tional to the measurement; intended for
output not caused by input concentration connection to readout or data processing changes. devices. Usually expressed as millivolts or Interference-An undesired positive or negamilliamps full scale at a given impedence. tive output caused by a substance other Full Scale—The maximum measuring limit than the one being measured. for a given range.
Interference Equivalent–The portion of inMinimum Detectable Sensitivity—The small
dicated input concentration due to the est amount of input concentration that can be detected as the concentration ap
presence of an interferent. proaches zero.
Operating Temperature Range—The range of Accuracy—The degree of agreement between
ambient temperatures over which the ina measured value and the true value; usu
strument will meet all performance specifi. ally expressed at + percent of full scale. cations.
Figure E1. Typical flow diagram. APPENDIX F_REFERENCE METHOD FOR THE dioxide concentrations of 140 mg./m.: (0.072
DETERMINATION OF NITROGEN DIOXIDE IN THE p.p.m.) and 200 mg./m.3 (0.108 p.p.m.), respecATMOSPHERE (24-HOUR SAMPLING METHOD) tively, based on an automated analysis of
samples collected from a standard test at1. Principle and Applicability.
mosphere. Precision would probably be dif1.1 Nitrogen dioxide is collected by bub
ferent when the analysis is performed bling air through a sodium hydroxide solu
manually. tion to form a stable solution of sodium
4.2 No accuracy data are available. nitrite. The nitrite ion produced during sam
4.3 Samples are stable for at least 6 weeks. pling is determined colorimetrically by react
5. Apparatus. ing the exposed absorbing reagent with
5.1 Sampling. See Figure F1. phosphoric acid, sulfanilamide, and N-1
5.1.1 Absorber. Polypropylene tubes 164 X naphthylethylenediamine dihydrochloride. 1.2 The method is applicable to collection
32 mm., equipped with polypropylene twoof 24-hour samples in the field and sub
port closures.* Rubber stoppers cause high sequent analysis in the laboratory.
and varying blank values and should not be 2. Range and Sensitivity.
used. A gas dispersion tube with a fritted 2.1 The range of the analysis is 0.04 to 1.5 end of porosity B (70–100 um. maximum pore ug. NO,/ml. With 50 ml. absorbing reagent diameter) is used. and a sampling rate of 200 ml./min. for 24 184.108.40.206 Measurement of Maximum Pore hours, the range of the method is 20–740 Diameter of Frit. Carefully clean the frit with ug./m.: (0.01-0.4 p.p.m.) nitrogen dioxide.
dichromate-concentrated sulfuric acid clean. 2.2 A concentration of 0.04 ug. NOz/ml.
ing solution and rinse well with distilled will produce an absorbance of 0.02 using
water. Insert through one hole of a two-hole 1-cm, cells.
rubber stopper and install in a test tube con3. Interferences.
taining sufficient distilled water to cover the 3.1 The interference of sulfur dioxide is fritted portion. Attach a vacuum source to eliminated by converting it to sulfuric acid the other hole of the rubber stopper and with hydrogen peroxide before analysis. (1) measure the vacuum required to draw the
4. Precision, Accuracy, aná Stability.
4.1 The relative standard deviations are *Available from Bel-Art Products, Pequan. 14.4 percent and 21.5 percent at nitrogen nock, N.J.
S=Surface tension of water in dynes/cm.
at the test temperature (73 at 18° C.,
72 at 25° C., and 71 at 31° C.). P=Measured vacuum, mm. Hg.
5.1.2 Probe. Teflon, polypropylene, or glass tube with a polypropylene or glass funnel at the end and a membrane filter to protect the frit. Replace filter after collecting five samples, or more often as indicated by visual observation of the loading.
5.1.3 Flow Control Device. Calibrated 27gauge hypodermic needle, three-eighths of an inch long to maintain a flow of approximately 0.2 liter/minute. The needle should be protected by a membrane filter. Change filter after collecting 10 samples.
5.1.4 Air Pump. Capable of maintaining a flow of 0.2 liter/minute through the absorber, and a vacuum of 0.7 atmosphere.
5.1.5 Calibration Equipment. Glass flowmeter for measuring airflows up to approximately 275 ml./min. within +2 percent, stopwatch, and precision wet test meter (1 liter/revolution).
5.2.1 Volumetric Flasks. 50, 100, 200, 250, 500, 1,000 ml.
5.2.2 Graduated Cylinder. 1,000 ml.
5.2.3 Pipets, 1, 2, 5, 10, 15 ml. volumetric; 2 ml., graduated in 1/10 ml. intervals.
5.2.4 Test Tube.
5.2.5. Spectrophotometer or Colorimeter. Capable of measuring absorbance at 540 nm. Bandwidth is not critical.
6.1.1 Absorbing Reagent. Dissolve 4.0 g. sodium hydroxide in distilled water and dilute to 1,000 ml.
6.2.1 Sulfanilamide. Dissolve 20 g. sulfanilamide in 700 ml. distilled water. Add, with mixing, 50 ml. concentrated phosphoric acid (85 percent) and dilute to 1,000 ml. This solution is stable for a month if refrigerated.
6.2.2 NEDA Solution. Dissolve 0.5 g. N-1naphthylethylenediamine dihydrochloride in 500 ml. of distilled water. This solution is stable for a month if refrigerated and protected from light.
6.2.3 Hydrogen peroxide. Dilute 0.2 ml. 30 percent hydrogen peroxide to 250 ml. with distilled water. This solution may be used for a month if protected from light.
6.2.4 Standard Nitrite Solution. Dissolve sufficient desiccated sodium nitrite (NaNO2, assay of 97 percent or greater) and dilute with distilled water to 1,000 ml. so that a solution containing 1,000 ug. NO,/ml. is obtained. The amount of NaNO2 to use is calculated as follows:
G=Amount of NaNO,, g.
NO, into NaNO,.
7.1 Sampling. Assemble the sampling train as shown in Figure F1. Add 50 ml. absorbing reagent to the absorber. Disconnect funnel, insert calibrated flowmeter, and measure flow before sampling. If flow rate before sampling is less than 85 percent of needle calibration, check for leak or change filters as necessary. Remove flowmeter and replace funnel. Sample for 24 hours from midnight to midnight and measure flow at end of sampling period.
7.2 Analysis. Replace any water lost by evaporation during sampling. Pipet 10 ml. of the collected sample into a test tube. Add 1.0 ml. hydrogen peroxide solution, 10.0 ml. sulfanilamide solution, and 1.4 ml. NEDA solution with thorough mixing after the addition of each reagent. Prepare a blank in the same manner using 10 ml. absorbing reagent. After a 10-minute color-development interval, measure the absorbance at 540 nm. against the blank. Read ug. NO,/ml. from standard curve (Section 8.2).
8. Calibration and Efficiencies.
8.1.1 Calibration of Flowmeter. Using a wet test meter and a stopwatch, determine the rates of air flow (ml./min.) through the flowmeter at several ball positions. Plot ball positions versus flow rates.
8.1.2 Calibration of Hypodermic Needle. Connect the calibrated flowmeter, the needle to be calibrated, and the source of vacuum in such a way that the direction of airflow through the needle is the same as in the sampling train. Read the position of the ball and determine flow rate in ml./min. from the calibration chart prepared in 8.1.1. Reject all needles not having flow rates of 190 to 210 ml./min. before sampling.
8.2 Calibration Curve. Dilute 5.0 ml. of the 1,000 ug. NO,/ml. solution to 200 ml. with absorbing reagent. This solution contains 25 ug. NO,/ml. Pipet 1, 2, 5, and 15 ml. of the 25 ug. NO,/ml. solution into 50-, 50-, 100-, and 250-ml. volumetric flasks and dilute to the mark with absorbing reagent. The solutions contain 0.50, 1.00, 1.25, and 1.50 ug. NO,/ml., respectively. Run standards as instructed in 7.2. Plot absorbance vs. ug NO,/ml.
8.3 Efficiencies. An overall average efficiency of 35 per cent was obtained from test atmospheres having nitrogen dioxide concentrations of 140 ug./m.3 and 200 ug./m.3 by automated analysis.(2)
V=Volume of air sampled, m.3 0.35=Efficiency.
9.2.1 If desired, concentration of nitrogen dioxide may be calculated as p.p.m. NO,.
p.p.m.= (ug. NO,/m.3) X 5.32 x 10-4 10. References. (1) Jacobs, M. B., and Hochheiser, S., "Con
tinuous Sampling and Ultramicrodetermination of Nitrogen Dioxide in
Air”, Anal. Chem., 30 426 (1958).
J. B., and Thompson, R. J., "Studies in
50=Volume of absorbing reagent used in
PART 51—REQUIREMENTS FOR PREP- Subpart B—Plan Content and Requirements
ARATION, ADOPTION, AND SUB-
51.10 General requirements.
51.11 Legal authority. PLANS
51.12 Control strategy: General. Subpart A-General Provisions
51.13 Control strategy: Sulfur oxides and Sec.
particulate matter. 51.1 Definitions.
51.14 Control strategy: Carbon monoxide, 51.2 Stipulations.
hydrocarbons, photochemical oxi51.3 Classification of regions.
dants and nitrogen dioxide. · 51.4 Public hearings.
51.15 Compliance schedules. 51.5 Submittal of plans; preliminary re- 51.16 Prevention of air pollution emerview of plans.
gency episodes. 51.6 Revisions.
51.17 Air quality surveillance. 51.7 Reports.
51.18 Review of new sources and modifica51.8 Approval of plans.