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Union Carbide Instruction Manual for Model 3020 Gas Chromatograph for COCH.-T/1. White Plains, N.Y.

Instruction Manual for 350 F Analyzer, Tracor Inc., Austin, Tex.

6-in. PEN-RAY



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Figure D2. Ozone source.

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concentration at the instrument inlet to a

reading of 90 percent of the ultimate reA. Suggested Performance Specifications corded concentration. for Atmospheric Analyzers for Hydrocarbons Rise Time (90 percent)-The interval beCorrected for Methane:

tween initial response time and time to 90

percent response after a step decrease in Range (minimum)..

0.3 mg./m.: (0-5 p.p.m.) the inlet concentration.

Zero Drift-The change in instrument 0-3 mg./m.' (0-5 p.p.m.)

output over a stated time period, usually CH

24 hours, of unadjusted continuous operOutput (minimum)...... 0-10 mv. full scale. Minimum detectable sensitiv. 0.1 p.p.m. THC.

ation, when the input concentration is ity.

zero; usually expressed as percent full 0.1 p.p.m. CH.

scale. Zero drift (maximum).

Not to exceed 1 percent/24 Span Drift-The change in instrument hours.

output over a stated time period, usually Span drift (maximum)............ Not to exceed 1 percent/24

24 hours, of unadjusted continuous operhours.

ation, when the input concentration is a Precision (minimum) .......... ....... +0.5 percent. Operational period (minimum).. 3 days.

stated upscale value; usually expressed as

percent full scale. Operating temperature range 5-40° C. (minimum).

Precision–The degree of agreement beOperating humidity range 10-100 percent.

tween repeated measurements of the same (minimum).

concentration. It is expressed as the averLinearity (maximum).................. 1 percent of full scale.

age deviation of the single results from

the mean.

Operational Period—The period of time B. Suggested Definitions of Performance

over which the instrument can be expectSpecifications:

ed to operate unattended within specificaRange-The minimum and maximum mea tions. surement limits.

Noise--Spontaneous deviations from a mean Output-Electrical signal which is propor output not caused by input concentration

tional to the measurement; intended for changes. connection to readout or data processing Interference-An undesired positive or negdevices. Usually expressed as millivolts or ative output caused by a substance other milliamps full scale at a given impedence. than the one being measured. Full Scale-The maximum measuring limit Interference Equivalent–The portion of infor a given range.

dicated input concentration due to the Minimum Detectable Sensitivity-The presence of an interferent.

smallest amount of input concentration Operating Temperature Range-The range that can be detected as the concentration of ambient temperatures over which the approaches zero.

instrument will meet all performance Accuracy-The degree of agreement be specifications.

tween a measured value and the true Operating Humidity Range -The range of value; usually expressed at percent of ambient relative humidity over which the full scale.

instrument will meet all performance Lag Time-The time interval from a step specifications.

change in input concentration at the in- Linearity-The maximum deviation between strument inlet to the first corresponding an actual instrument reading and the change in the instrument output.

reading predicted by a straight line drawn Time to 90 Percent Response–The time in between upper and lower calibration

terval from a step change in the input points.


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Principle and Applicability

1. Atmospheric concentrations of nitrogen dioxide (NO) are measured indirectly by photometrically measuring the light intensity, at wavelengths greater than 600 nanometers, resulting from the chemiluminescent reaction of nitric oxide (NO) with ozone (0,). (1,2,3) NO, is first quantitatively reduced to NO(4,5,6) by means of a convert. er. NO, which commonly exists in ambient air together with NO2, passes through the converter unchanged causing a resultant total NO, concentration equal to NO+NO2. A sample of the input air is also measured without having passed through the convert. ed. This latter NO measurement is subtracted from the former measurement (NO+NO2) to yield the final NO, measurement. The NO and NO+NO, measurements may be made concurrently with dual systems, or cyclically with the same system provided the cycle time does not exceed 1 minute.

2. Sampling considerations.

2.1 Chemiluminescence NO/NO/NO, analyzers will respond to other nitrogen containing compounds, such as peroxyacetyl nitrate (PAN), which might be reduced to NO in the thermal converter. (7) Atmospheric concentrations of these potential interferences are generally low relative to NO. and valid NO, measurements may be obtained. In certain geographical areas, where the concentration of these potential interferences is known or suspected to be high relative to NO2, the use of an equivalent method for the measurement of NO, is recommended.

2.2 The use of integrating flasks on the sample inlet line of chemiluminescence NO/ NO, NO, analyzers is optional and left to couraged. The sample residence time between the sampling point and the analyzer should be kept to a minimum to avoid erroneous NO, measurements resulting from the reaction of ambient levels of NO and O, in the sampling system.

2.3 The use of particulate filters on the sample inlet line of chemiluminescence NO/ NO,/NO, analyzers is optional and left to the discretion of the user or the manufacturer. Use of the filter should depend on the analyzer's susceptibility to interference, malfunction, or damage due to particulates. Users are cautioned that particulate matter concentrated on a filter may cause errone

us NO, measurements and therefore filters hould be changed frequently.

3. An analyzer based on this principle will e considered a reference method only if it as been designated as a reference method i accordance with Part 53 of this chapter. 'alibration

1. Alternative A-Gas phase titration GPT) of an NO standard with Oz.

Major equipment required: Stable O, genrator. Chemiluminescence NO/NO/NO, nalyzer with strip chart recorder(s). NO oncentration standard.

1.1 Principle. This calibration technique s based upon the rapid gas phase reaction etween NO and O, to produce stoichiomeric quantities of NO, in accordance with he following equation: (8) NO+O: NO2+O2

(1) The quantitative nature of this reaction is uch that when the NO concentration is inown, the concentration of NO, can be de ermined. Ozone is added to excess NO in a lynamic calibration system, and the NO Channel of the chemiluminescence NO/ VO, NO, analyzer is used as an indicator of hanges in NO concentration. Upon the adlition of Os, the decrease in NO concentraion observed on the calibrated NO channel s equivalent to the concentration of NO, produced. The amount of NO, generated may be varied by adding variable amounts of O, from a stable uncalibrated O, generitor. (9)

1.2 Apparatus. Figure 1. a schematic of a Lypical GPT apparatus, shows the suggested configuration of the components listed below. All connections between components in the calibration system downstream from the O, generator should be of glass, Teflon", or other non-reactive material.

1.2.1 Air flow controllers. Devices capable of maintaining constant air flows within +2% of the required flowrate.

1.2.2 NO flow controller. A device capable of maintaining constant NO flows within +2% of the required flowrate. Component parts in contact with the NO should be of a non-reactive material.

1.2.3 Air flowmeters. Calibrated flowmeters capable of measuring and monitoring air flowrates with an accuracy of 12% of the measured flowrate.

1.2.4 NO flowmeter. A calibrated flowmeter capable of measuring and monitoring NO flowrates with an accuracy of +2% of the measured flowrate. (Rotameters have been reported to operate unreliably when measuring low NO flows and are not recommended.)

1.2.5 Pressure regulator for standard NO cylinder. This regulator must have a non reactive diaphragm and internal parts and a suitable delivery pressure.

1.2.6 Ozone generator. The generator must be capable of generating sufficient and stable levels of O, for reaction with NO to generate NO, concentrations in the range required. Ozone generators of the electric discharge type may produce NO and NO, and are not recommended.

1.2.7 Valve. A valve may be used as shown in Figure 1 to divert the NO flow when zero air is required at the manifold. The valve should be constructed of glass, Teflon', or other nonreactive material.

1.2.8 Reaction chamber. A chamber, constructed of glass, Teflon', or other nonreactive material, for the quantitative reaction of O, with excess NO. The chamber should be of sufficient volume (VRC) such that the residence time (tr) meets the requirements specified in 1.4. For practical reasons, tr should be less than 2 minutes.

1.2.9 Mixing chamber. A chamber constructed of glass, Teflon", or other nonreactive material and designed to provide thorough mixing of reaction products and diluent air. The residence time is not critical when the dynamic parameter specification given in 1.4 is met.

1.2.10 Output manifold. The output manifold should be constructed of glass, Teflon", or other non-reactive material and should be of sufficient diameter to insure an insignificant pressure drop at the analyzer connection. The system must have a vent designed to insure atmospheric pressure at the manifold and to prevent ambient air from entering the manifold.

1.3 Reagents.

1.3.1 NO concentration standard. Cylinder containing 50 to 100 ppm NO in N, with less than 1 ppm NO2. The cylinder must be traceable to a National Bureau of Standards NO in N, Standard Reference Material (SRM 1683 or SRM 1684) or NO, Standard Reference Material (SRM 1629). Procedures for certifying the NO cylinder (working standard) against an NBS traceable NO or NO, standard and for determining the amount of NO, impurity are given in reference 13. The cylinder should be recertified on a regular basis as determined by the local quality control program.

1.3.2 Zero air. Air, free of contaminants which will cause a detectable response on the NO/NO,/NO, analyzer or which might react with either NO, Oz, or NO, in the gas phase titration. A procedure for generating zero air is given in reference 13.

1.4 Dynamic parameter specification.

1.4.1 The O, generator air flowrate (F.) and NO flowrate (Fxo) (see Figure 1) must be adjusted such that the following relationship holds:

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