**STANDARD OPERATING PROCEDURES**

**THERMO ELECTRON CORPORATION**

**MODEL 43C-TLE TRACE LEVEL**

**SULFUR DIOXIDE INSTRUMENT**

**Version 2.1**

**April 26, 2005**

# 

![](media/image1.png){width="1.6583333333333334in"
height="1.6111111111111112in"}

**Section 1.1 Acknowledgments**

This Standard Operating Procedure (SOP) for Sulfur Dioxide -- Trace
Level is the product of EPA's Office of Air Quality, Planning and
Standards. The following individuals are acknowledged for their
contributions.

**Principal Author**

Solomon Ricks, OAQPS-EMAD, Research Triangle Park, NC 27711

**Reviewers**

Office of Air Quality, Planning and Standards

Joann Rice, Trace Gas Team Lead, OAQPS-EMAD, Research Triangle Park, NC
27711

Anna Kelly, OAQPS-EMAD, Research Triangle Park, NC 27711

Keith Kronmiller, Mantech, Inc. Research Triangle Park, NC 27711

**Comments and questions can be directed to:**

Solomon Ricks

EPA-OAQPS

Emission, Analysis and Monitoring Division

Mail Drop D339-02

Research Triangle Park, NC 27711

Email: <ricks.solomon@epa.gov>

Phone: (919)-541-5242

**Section 2.0 Table of Contents**

+------------------------------------------------------------+---------+
| Section                                                    | Page    |
+------------------------------------------------------------+---------+
| 1.0 Title Page                                             | 1       |
+------------------------------------------------------------+---------+
| 1.  Acknowledgements                                       | 2       |
+------------------------------------------------------------+---------+
| 2.0 Table of Contents                                      | 3       |
+------------------------------------------------------------+---------+
| 2.1 List of Tables and Figures                             | 4       |
+------------------------------------------------------------+---------+
| 3.0 Procedures                                             | 5       |
+------------------------------------------------------------+---------+
| 3.1 Scope and Applicability                                | 5       |
+------------------------------------------------------------+---------+
| 3.2 Summary of Method                                      | 5       |
+------------------------------------------------------------+---------+
| 3.3 Definitions                                            | 6       |
+------------------------------------------------------------+---------+
| 3.4 Health and Safety Warnings                             | 6       |
+------------------------------------------------------------+---------+
| 3.5 Cautions                                               | 6       |
+------------------------------------------------------------+---------+
| 3.6 Interferences                                          | 7       |
+------------------------------------------------------------+---------+
| 3.7 Personal Qualifications                                | 7       |
+------------------------------------------------------------+---------+
| 3.8 Equipment and Supplies                                 | 8       |
+------------------------------------------------------------+---------+
| 3.9 Procedure                                              | 9       |
+------------------------------------------------------------+---------+
| 3.9.1 Sample Collection                                    | 9       |
+------------------------------------------------------------+---------+
| 3.9.2 Sample Handling and Preservation                     | 9       |
+------------------------------------------------------------+---------+
| 3.9.3 Instrument Operation, Start up and Maintenance       | 9       |
+------------------------------------------------------------+---------+
| 3.9.3.1 Start up                                           | 9       |
+------------------------------------------------------------+---------+
| 3.9.3.2 Operation and Range Setting                        | 9       |
+------------------------------------------------------------+---------+
| 3.9.9.3 Diagnostic Checks/Manual Checks                    | 10      |
+------------------------------------------------------------+---------+
| 3.9.3.4 Preventive Maintenance                             | 11      |
+------------------------------------------------------------+---------+
| 3.9.3.5 Instrument Troubleshooting                         | 12      |
+------------------------------------------------------------+---------+
| 3.9.4 Calibration and Standardization                      | 12      |
+------------------------------------------------------------+---------+
| 3.9.4.1 Adjustment to Zero Air                             | 12      |
+------------------------------------------------------------+---------+
| 3.9.4.2 Adjustment to Calibration Gas                      | 12      |
+------------------------------------------------------------+---------+
| 3.10 Data Analysis and Calculations                        | 12      |
+------------------------------------------------------------+---------+
| 4.0 Quality Control and Quality Assurance                  | 12      |
+------------------------------------------------------------+---------+
| 4.1 Precision                                              | 13      |
+------------------------------------------------------------+---------+
| 4.2 Bias                                                   | 13      |
+------------------------------------------------------------+---------+
| 4.3 Representativeness                                     | 13      |
+------------------------------------------------------------+---------+
| 4.4 Completeness                                           | 13      |
+------------------------------------------------------------+---------+
| 4.5 Comparability                                          | 13      |
+------------------------------------------------------------+---------+
| 4.6 Method Detection Limit                                 | 14      |
+------------------------------------------------------------+---------+
| 5.0 References                                             | 15      |
+------------------------------------------------------------+---------+

**List of Tables**

  ------------------------------------------------------------ ----------
  Table Name and Number                                        Page

  3-1 Definition of Key Terms                                  6

  3-2 Diagnostic Checks                                        11

  3-3 Preventive Maintenance Schedule for the 43C-TLE          11

  4-1 Measurement Quality Assurance Objectives                 15
  ------------------------------------------------------------ ----------

**List of Figures**

  ------------------------------------------------------------ ----------
  Figure Name and Number                                       Page

  3-1 Model 43C-TLE Flow Diagram                               8

  A-1 Model 43C-TLE Quality Control and Maintenance Record     16

                                                               
  ------------------------------------------------------------ ----------

#### STANDARD OPERATING PROCEDURES

**THERMO ELECTRON CORPORATION**

**MODEL 43C-TLE TRACE LEVEL SULFUR DIOXIDE INSTRUMENT**

**3.0 PROCEDURES**

**3.1 Scope and Applicability**

Sulfur Dioxide (SO~2~) is a colorless, nonflammable gas that has a
strong suffocating odor. SO~2~ originates from fuel containing sulfur
(mainly coal and oil) burned at power plants and during metal smelting
and other industrial processes. High levels of SO~2~ can result in
temporary breathing impairment for asthmatic children and adults who are
active outdoors. Long-term exposure to high levels of SO~2~, in the
presence of high levels of particulate matter, may aggravate existing
cardiovascular disease and respiratory illness.

The Thermo Electron Corporation model 43C-TLE combines proven detection
technology and advanced diagnostics for the determination of trace
levels of SO~2~. This SOP will detail the operation, preventive
maintenance, cautions and health warnings.

The Detection Limit (DL) for a non-trace level SO~2~ analyzer is 10
parts per billion (ppb) *(Code of Federal Regulations,* Volume 40, Part
53.23c, or, in the shortened format used hereafter, 40 CFR 53.23c)^3^.
However, the 43C-TLE has an estimated DL of 100 parts per trillion
(ppt), which is accomplished by an increased detector sensitivity, as
well as increasing the length of the standard instrument's optics bench.
This document will discuss the Trace Level (TL) operating procedures in
detail.

**3.2 Summary of Method**

The Model 43C-TLE Trace Level operating principle is based on measuring
the emitted fluorescence of SO~2~ produced by the absorption of
ultraviolet (UV) light. Pulsating UV light is focused through a narrow
band-pass filter mirror allowing only light wavelengths of 190 to 230 nm
to pass into the fluorescent chamber. SO~2~ absorbs light in this region
without any quenching by air or most other molecules found in polluted
air. The SO~2~ molecules are excited by UV light and emit a
characteristic decay radiation. A second filter allows only this decay
radiation to contact a photomultiplier tube (PMT). Electronic signal
processing transfers the light energy impinging on the PMT into a
voltage which is directly analyzed. Specifically,

SO~2~ + hν~1~ → SO~2~\* → SO~2~ + hν~2~

where:

hν~1~ = incidence light,

hν~2~ = fluoresced light, and

SO~2~\* = SO~2~ in its excited state

The 43C-TLE instrument operates in the following fashion:

###  

### In sample mode, the sample is drawn into the analyzer through the SAMPLE bulkhead. The sample flows through a hydrocarbon "kicker," which operates on a selective permeation principle, allowing only hydrocarbon molecules to pass through the tube wall. The driving force for the hydrocarbon removal is the differential partial pressure across the wall. This differential pressure is produced within the instrument by passing the sample gas through a capillary tube to reduce its pressure and feeding it into the shell side of the hydrocarbon kicker. The SO~2~ molecules pass through the hydrocarbon "kicker" unaffected. 

### The sample flows into the fluorescence chamber, where pulsating UV light excites the SO~2~ molecules. The condensing lens focuses the pulsating UV light into the mirror assembly. The mirror assembly contains eight selective mirrors that reflect only the wavelengths which excite SO~2~ molecules. 

### As the excited SO~2~ molecules decay to lower energy states they emit UV light that is proportional to the SO~2~ concentration. The band pass filter allows only the wavelengths emitted by the excited SO~2~ molecules to reach the PMT. The PMT detects the UV light emission from the decaying SO~2~ molecules. The photo detector, located at the back of the fluorescence chamber, continuously monitors the pulsating UV light source and is connected to a circuit that compensates for fluctuations in the UV light. 

### The sample then flows through a flow sensor, a capillary, and the shell side of the hydrocarbon "kicker." The model 43C-TLE trace level outputs the SO~2~ concentration to the front panel display and the analog or digital outputs. 

**3.3 Definitions**

Here are some key terms for this method.

**Table 3-1, Definitions of Key Terms**

  ----------------------- -----------------------------------------------
  [Term]{.underline}      Definition

  DAS                     Data acquisition system. Used for automatic
                          collection and recording of Sulfur Dioxide
                          concentrations.

  Interferences           Physical or chemical entities that cause Sulfur
                          Dioxide measurements to be higher (positive) or
                          lower (negative) than they would be without the
                          entity. (See Section 3.6).
  ----------------------- -----------------------------------------------

**3.4 Health and Safety Warnings**

[To prevent personal injury, please heed these warnings concerning the
43C-TLE.]{.underline}

1.  Always use a third ground wire on all instruments.

2.  Always unplug the analyzer when servicing or replacing parts.

3.  If it is mandatory to work inside an analyzer while it is in
    operation, use extreme caution to avoid contact with high voltages.
    The analyzer has a 110 volt Volts Alternating Current (VAC) power
    supply. Refer to the manufacturer\'s instruction manual and know the
    precise locations of the VAC components before working on the
    instrument.

4.  Avoid electrical contact with jewelry. Remove rings, watches,
    bracelets, and necklaces to prevent electrical bums.

**3.5 Safety Precautions**

[To avoid damaging internal components of the 43C-TLE, the following
precautions should be taken:]{.underline}

1.  Wear an anti-static wrist strap that is properly connected to earth
    ground (note that when the analyzer is unplugged, the chassis is not
    at earth ground);

2.  If an anti-static wrist strap is not available, be sure to touch a
    grounded metal object before touching any internal components;

3.  Handle all printed circuit boards by the edge;

4.  Carefully observe the instructions in each procedure specified in
    Chapter 7 of the manual;

5.  Normally, if Teflon™ filters are used in the sample train, cleaning
    the optical bench will not be required. However, in the event that
    the bench is cleaned, be careful to avoid damaging the interior of
    the sample chamber. Use extreme caution when cleaning or servicing
    the sample chamber(s). In addition the mirrors are very fragile;
    avoid dropping the instrument. This may damage, misalign or crack
    the mirrors and cause expensive repairs;

6.  Keep the interior of the analyzer clean;

7.  Inspect the system regularly for structural integrity;

8.  To prevent major problems with leaks, make sure that all sampling
    lines are reconnected after required checks and before leaving the
    site;

9.  Inspect tubing for cracks and leaks;

10. It is recommended that the analyzer be leak checked after
    replacement of any pneumatic parts;

11. If cylinders are used in tandem with Mass Flow Control (MFC)
    calibrators, use and transport is a major concern. Gas cylinders can
    sometimes contain pressures as high as 2000 pounds per square inch
    (psi). Handling of cylinders must be done in a safe manner. If a
    cylinder is accidentally dropped and valve breaks off, the cylinder
    can become explosive or a projectile;

12. Transportation of cylinders is regulated by the Department of
    Transportation (DOT). It is strongly recommended that all agencies
    contact the DOT or Highway Patrol to learn the most recent
    regulations concerning transport of cylinders;

13. It is possible (and practical) to blend other compounds with SO~2~.
    If this is the case, it is recommended that MSDS for all compounds
    be made available to all staff that use and handle the cylinders or
    permeation tubes; and

14. Shipping of cylinders is governed by the DOT. Contact the DOT or
    your local courier about the proper procedures and materials needed
    to ship high-pressure cylinders.

**3.6 Interferences**

The most common source of interference is from other gases that
fluoresce in a similar fashion to SO~2~ when exposed to UV light. The
most significant of these is a class of hydrocarbons called polynuclear
aromatic hydrocarbons (PAH); of which naphthalene is a prominent
example. Xylene is another hydrocarbon that can cause interference.
These hydrocarbons are removed via the hydrocarbon "kicker" (see section
3.2 for explanation on the hydrocarbon "kicker").

Nitrogen oxide (NO) fluoresces in a spectral range close to SO~2~.
Interference from NO is addressed by the presence of the band pass
filter, which allows only the wavelengths emitted by the excited SO
molecules to reach the PMT.

**3.7 Personnel Qualifications**

The person(s) chosen to operate the Thermo 43C-TLE should have a minimum
of qualifications. The understanding of basic chemistry and electronics
are a must. The understanding of digital circuitry is helpful, but not
required. Also, courses in data processing and validation are also
welcome.

**3.8 Equipment and Supplies**

**Monitoring Apparatus:** The design of the 43C-TLE combines proven
detection technology with advanced diagnostics for greater flexibility
and reliability. A diagram of the 43C-TLE instrument is described in
Figure 3-1. The three main components are:

-   *[Pneumatic System:]{.underline}* Consists of sample inlet line,
    particulate filter, reaction chamber, flowmeter, and pump, all used
    to bring ambient air samples to the analyzer inlet.

-   *[Analytical System]{.underline}*: This portion of the instrument
    consists of the UV lamp, mirrors, photo-detector and band pass
    filter.

-   *[Electronic Hardware:]{.underline}* The part of the analyzer that
    generally requires little or no maintenance. If the 43C-TLE is
    operated above the manufacturer\'s recommended temperature limit,
    however, individual integrated chips can fail and cause problems
    with data storage or retrieval.

Other apparatus and equipment includes the following.

**Instrument Shelter:** A shelter is required to protect the analyzer
from precipitation and adverse weather conditions, maintain operating
temperature within the analyzer\'s temperature range requirements, and
provide security and electrical power. The recommended shelter
temperature range is 20-30^o^C.

**Spare Parts and Incidental Supplies:** See the 43C-TLE manual, Chapter
5, for a list of recommended spare parts.

**Calibration System**: A system that creates concentrations of SO~2~ of
known quality is necessary for establishing traceability. This is
described in detail in the Environics Series 9100 Computerized Ambient
Monitoring Calibration System SOP. Please reference this document.

**DAS**: A data acquisition system is necessary for storage of ambient
and ancillary data collected by the 43C-TLE. This is detailed in the
"Data Acquisition and Management SOP."

![](media/image2.png){width="4.875in" height="3.1770833333333335in"}

**Figure 3-1 Model 43C-TLE Flow Diagram**

**Wiring, Tubing and Fittings***:* Teflon™, stainless steel, and
borosilicate glass are inert materials that should be used exclusively
throughout the intake system. Stainless steel tubing should be avoided
because it is expensive, hard to clean, and can develop micro-cracks
that are difficult to detect. Teflon™ tubing is the best choice for the
connection between the intake manifold and the 43C-TLE inlet. Examine
and discard if particulate matter collects in the tubing. All fittings
and ferrules should be made of Teflon™ or stainless steel. Connection
wiring to the DAS should shielded two strand wire or RS-232 cables for
digital connections.

**Reagents and Standard:** The 43C-TLE does not require any reagents
since the instrument uses photometry to analyze for sulfur dioxide. All
standards for the SO~2~ method can be obtained in compressed cylinders
and must be NIST traceable. Please see the Environics Series 9100
Computerized Ambient Monitoring Calibration System SOP.

**3.9 Procedure**

**3.9.1 Sample Collection:** Sampling for trace level SO~2~ is performed
by drawing ambient air through a sample manifold directly into the
analyzer continuously via a vacuum pump. All inlet materials must be
constructed from Teflon™, or borosilicate glass. The siting criteria for
SO~2~ Trace Level instruments in detailed in 40 CFR 58, appendix A^4^ .

**3.9.2 Sample Handling and Preservation:** SO~2~ samples receive no
special preparation prior to analysis. Therefore this SOP does not need
a section on Sample Handling and Preservation.

**3.9.3 Instrument Operation , Startup and Maintenance**

This section discusses startup, operation and maintenance of the
43C-TLE. The 43C-TLE has a digital front panel screen with pushbuttons
below. This allows the user to check functions, switch operating
parameters, and adjust zero and span. Recommend at start-up of
instrument and after a warm-up period for the instrument, run through
the menu items and record the current settings. **It is extremely
important that the user familiarize themselves with the menus available.
Inadvertently changing parameters within the analyzer can damage the
instrument and possibly invalidate data as well. Please reference the
Thermo 43C-TLE owner's manual and read it carefully before adjusting any
parameters that are set by the factory.**

**3.9.3.1 Start up**

1.  Before the instrument is operated, inspect the instrument for any
    damage. If damage is observed to the shipping box or the instrument,
    contact your shipping personnel.

2.  Carefully remove the cover and check for internal damage. Please see
    Chapter 2 of the 43C-TLE manual.

3.  Check that all connectors and printed circuit boards are firmly
    attached.

4.  Once you have removed any packing material and performed your
    inspection, replace the cover.

5.  Connect the sample line to the **SAMPLE** bulkhead on the rear panel
    of the instrument. See Chapter 2 of the 43C-TLE manual.

6.  Connect the **EXHAUST** bulkhead to a suitable vent.

7.  Connect a suitable recording device to the rear panel terminals.
    Please see EPA SOP on "Data Management" for details.

8.  Plug the instrument into a grounded power strip that has surge
    protection. It is also advisable to purchase an Uninterrupted Power
    Supply (UPS). An UPS will protect the 43C-TLE from power surges and
    keep the unit operating until an operator can shut it down.

9.  Press the power rocker switch to "ON."

**3.9.3.2 Operation and Range Setting**

1.  The exhaust fan will start and the Power-Up and Self-Test screens
    will be displayed. These screens are displayed each time the
    instrument is turned on, and will continue to be displayed till the
    instrument has completed its warm up and self-checks. You should
    allow 30 minutes for the instrument to stabilize.

2.  After the warm-up period the Run screen, the normal operating
    screen, is displayed. This screen is where the SO2 concentration is
    displayed.

3.  From the Run screen, the Main Menu, which contains a list of
    submenus, can be displayed by pressing the **MENU** pushbutton. If
    the instrument is in **REMOTE** mode, press **ENTER** and select
    **LOCAL** mode in order to be able to change parameters.

4.  Instrument parameters and features are divided into the submenus
    according to their function. Use the **UP/DOWN ARROW** pushbuttons
    to move the cursor to each submenu. **Note:** When the Main Menu is
    entered directly from the Run screen, the **LEFT ARROW** pushbutton
    may be used to jump to the most recently displayed submenu screen.

5.  To set the range for the instrument, press the **DOWN ARROW**
    pushbutton till the cursor is on "Range." Press the **ENTER**
    pushbutton to display the Range Menu.

6.  In the upper right corner of the display, the word SINGLE, DUAL, or
    AUTO is displayed to indicate the active mode. For a detailed
    explanation about the SINGLE, DUAL, or AUTORANGE mode, see Chapter 3
    (page 3-7) of the manual. This SOP addresses setting the range for a
    single range.

7.  Press the **ENTER** pushbutton for the Gas Units screen. Use the
    **DOWN ARROW** pushbutton to select "PPB" and press **ENTER**. Press
    **MENU** to return to the Range Menu.

8.  Use the **DOWN ARROW** pushbutton to display the Range screen and
    press **ENTER**.

9.  Use the **UP/DOWN ARROW** pushbuttons to scroll through the preset
    ranges. Select "100.0" and press **ENTER**. Press **MENU** to return
    to the Range Menu.

10. Press **RUN** to return to the Run screen.

11. To set the correct time and date on the instrument, press **MENU**
    to return to the Main Menu. Press the **DOWN ARROW** pushbutton till
    the cursor is on Instrument Controls. Press **ENTER** to display the
    Instrument Controls screen.

12. Use the **UP/DOWN ARROW** pushbuttons to scroll through the choices.
    Select "Time" and press **ENTER**.

13. Use the **UP/DOWN ARROW** pushbuttons to increase/decrease the hours
    and minutes; use the **LEFT/RIGHT ARROW** pushbuttons to move the
    cursor left and right. Set the appropriate time and press **ENTER**.
    Press **MENU** to return to the Instrument Controls screen.

14. Select "Date" and press **ENTER**.

15. Use the **UP/DOWN ARROW** pushbuttons to increase/decrease the
    month, day, and year; use the **LEFT/RIGHT ARROW** pushbuttons to
    move the cursor left and right. Set the appropriate date and press
    **ENTER**. Press **RUN** to return to the Run screen.

16. The instrument is now set with the appropriate time, date, full
    scale range and units.

17. It is recommended that you allow the 43C-TLE 24 hours before you
    attempt function checks or calibration.

18. If your DAS does not have RS-232 capabilities, then proceed to the
    next section, Diagnostic Checks/Manual Checks. If you have connected
    the 43C-TLE to a computer or DAS, review the Diagnostic Check from
    your computer screen.

**3.9.3.3 Diagnostic Checks/Manual Checks**

To determine whether the 43C-TLE is working properly, the field
operators should perform the Diagnostic Checks every time they visit the
monitoring station. It is good practice for the operator to check these
Diagnostic Checks either by the computer or manually. Below are
instructions on how to perform this manually. Please note that the
43C-TLE has set upper and lower ranges for some of these Diagnostic
checks. Please reference the owner's manual for these ranges.

1.  To display the Diagnostics menu, from the Run screen press the
    **MENU** pushbutton to display the Main Menu. Use the **UP/DOWN
    ARROW** pushbuttons to move the cursor to "Diagnostics." Press
    **ENTER** for the Diagnostics screen.

2.  Use the **UP/DOWN ARROW** pushbuttons to toggle through the function
    check tree. The following table illustrates the functions that
    should be recorded. Please see Chapter 3 (page 3-34) 43C-TLE manual
    for more details. A maintenance check sheet is attached in Appendix
    A of this SOP.

3.  On the Program Number screen, the version numbers of the program
    installed are displayed. Prior to contacting the factory with any
    questions regarding the instrument, note the program numbers.

## Table 3-2 Diagnostic Checks

  --------------- -------------------------------------------------------
  Check           Explanation

  Voltages        The current DC power supply and PMT power supply
                  voltages

  Temperatures    The current internal instrument and chamber
                  temperatures

  Pressure        The current chamber pressure

  Flow            The current sample flow rate

  Lamp intensity  The current UV lamp intensity

  Optical Span    A quick way of checking the optics and electronics for
  Test            span drift

  Test Analog     Enable analog outputs to be set to zero and full scale
  Outputs         to adjust analog outputs to agree with the front panel
                  display
  --------------- -------------------------------------------------------

Once the Diagnostic checks have been established and recorded for the
43C-TLE, it is time to calibrate the instrument. Please refer to section
3.9.4 of this SOP.

**3.9.3.4 Preventive Maintenance**

Preventive maintenance should **prevent** down-time and data loss. Table
3.3 lists the preventive maintenance items that are listed in the model
43C-TLE manual, Chapter 5. The maintenance procedures described in
Chapter 5 of the manual should be performed every six months.

**Table 3-3 Preventive Maintenance Schedule for the 43C-TLE**

**Item** **Schedule**

Visual inspection and cleaning Bi-annually

Sample particulate filter inspection Weekly

Verify Test Function Weekly

Perform Level I calibration Daily

Capillary inspection and replacement Bi-annually

Perform flow check Bi-annually

Fan filter inspection and cleaning Bi-annually

Lamp voltage check Bi-annually

**3.9.3.5 Instrument Troubleshooting**

The 43C-TLE manual has an excellent troubleshooting guide in Chapter 6.

**3.9.4 Calibration and Standardization**

The calibration of the 43C-TLE is performed by comparing the output of
the instrument against standardized gases of known quality. Generation
of these gases is detailed in the Environics Series 9100 Computerized
Ambient Monitoring Calibration System SOP. This section will detail how
to adjust the 43C-TLE to the standardized gases. Once the calibration
has been performed, compare the response of your DAS to the calculated
"source" value. If this is outside of +/-10%, then adjust the instrument
response as detailed in the next sections.

**3.9.4.1 Adjustment to Zero Air**

Before running the zero air through the 43C-TLE, ensure that the zero
air is free from contaminants. One way to determine if the zero air is
free from contaminants is through the use of multiple zero air sources,
and determining which source produces the lowest response^5^. Appendix D
of the 43C-TLE manual provides suggestions for generating trace-quality
zero air.

In order to adjust the output of the 43C-TLE to zero air, perform the
following:

1.  Allow the instrument to sample zero air from a manifold that is at
    near atmospheric pressure for a minimum of 15 minutes.

2.  From the Main Menu select the Calibration menu; select the
    "Calibrate Zero" screen.

3.  Press **ENTER** to set the SO~2~ reading to zero.

4.  Press **MENU** to return to the Calibration menu.

5.  Press **RUN** to return to the Run screen.

**3.9.4.2 Adjustment to Calibration Gas**

It is desirable, but not essential, to calibrate the 43C-TLE at low
SO~2~ levels (typically, less than 20 ppb). However, fluorescence SO~2~
analyzers have been shown to be inherently linear over a wide dynamic
range. If low concentration SO~2~ calibration cylinders (less than 50
ppm) are used, there is the potential for contamination by back
diffusion from a poorly purged regulator. Contamination with even a
small amount of moisture from back diffusion can cause the SO~2~
concentration to become unstable; the lower the cylinder concentration,
the more susceptible it is to any contamination from "abuse" in the
field^5^. The best way to ensure low concentration cylinders are not
contaminated by back diffusion is to make sure whenever the cylinder
valve is open, there is gas flow out of the cylinder.

Appendix D of the 43C-TLE manual offers additional discussion on trace
level calibration issues.

In order to adjust the output of the 43C-TLE to NIST traceable
calibration gas, perform the following:

1.  Switch the calibration unit to generate a known concentration of
    SO~2~. Allow the instrument to sample calibration gas from a
    manifold that is at near atmospheric pressure for a minimum of 15
    minutes.

2.  From the Main Menu select the Calibration menu; select the
    "Calibrate SO~2~" screen.

3.  On the bottom line, there will be individual digits with which the
    span value can be set. In order to change the concentration, use the
    **UP/DOWN ARROW** pushbuttons to increase/decrease each digit; use
    the **LEFT/RIGHT ARROW** pushbuttons to move the cursor left and
    right.

4.  Press **ENTER** to calibrate the SO~2~ reading to the SO~2~
    calibration gas.

5.  This operation changes the calculation equation and adjusts the
    SO~2~ span coefficient of the instrument.

6.  Press **MENU** to return to the Calibration menu.

7.  Press **RUN** to return to the Run screen.

    **3.10 Data Analysis and Calculations**

    Data analysis for this analyzer is detailed in the "Data Acquisition
    and Management SOP."

**4.0 QUALITY CONTROL AND QUALITY ASSURANCE**

The following section has brief definitions of the QA/QC indicators.
Table 4-1 has the Measurement Quality Objectives (MQOs) of the Thermo
43C-TLE. Please note that this section details primarily with the QA
indicators. Quality Control for continuous electronic instruments, such
as the 43C-TLE consists of performing the diagnostic checks, maintenance
and calibrations. These procedures are detailed in sections 3.9.3 and
3.9.4: Instrument Operation, Startup and Maintenance and Calibration and
Standardization. Appendix A has an example of a Quality Control and
Maintenance Record developed by the EPA for this instrument.

**4.1 Precision**

Precision is defined as the measure of agreement among individual
measurements of the same property taken under the same conditions. For
SO~2~, this refers to testing the SO~2~ analyzer in the field at
concentrations between 0.0003 and 0.005 ppm. The test must be performed,
at a minimum, once every two weeks. Calculations for Precision can be
found in Reference item 3.

**4.2 Bias**

Bias is defined as the degree of agreement between a measured value and
the true, expected, or accepted value. Quantitative comparisons are made
between the measured value and the true, standard value during audits.
Generally, three upscale points and a zero point are compared. Two audit
types commonly used for SO~2~, direct comparison and blind, are
discussed below. The SOP should discuss plans for each type of audit.

-   **Direct Comparison Audits:** An independent audit system is brought
    to the monitoring location and produces gas concentrations that are
    assayed by the monitoring station\'s SO~2~ analyzer. In most cases,
    a person outside of the agency or part of an independent QA group
    within the agency performs the audit. The responses of the on-site
    analyzer are then compared against the calculated concentration from
    the independent audit system and a linear regression is generated

-   **Blind Audits:** In blind audits (also called performance
    evaluation audits); agency staff are sent an audit device, such as
    the National Performance Evaluation Program (NPEP). The agency staff
    does not know the SO~2~ concentrations produced by the audit
    equipment. Responses of the on-site analyzer are then compared
    against those of the generator and a linear regression is
    calculated.

**4.3 Representativeness**

Representativeness refers to whether the data collected accurately
reflect the conditions being measured. It is the data quality indicator
most difficult to quantify. Unless the samples are truly representative,
the other indicators are meaningless. Since the NCORE Level I and II
siting criteria are urban and regional, the trace level SO~2~ criteria
are the same. Please reference the National Monitoring Strategy^5^ for a
discussion of NCORE Level II SO~2~ monitoring scale.

**4.4 Completeness**

Completeness is defined as the amount of data collected compared to a
pre-specified target amount. For SO~2~, EPA requires a minimum
completeness of 75% (40 CFR 50, App.H.3). Typical completeness with the
43C-TLE values can approach 90-93%.

**4.5 Comparability**

Comparability is defined as the process of collecting data under
conditions that are consistent with those used for other data sets of
the same pollutant. The 43C-TLE meets the MQOs for a trace level SO~2~
instrument. Please see Table 4-1.

**4.6 Method Detection Limit**

The method detection limit (MDL) or detectability refers to the lowest
concentration of a substance that can be determined by a given
procedure. The 43C-TLE must be able to detect a minimum value of 300 ppt
of SO~2~.

Table 4-1 Measurement Quality Assurance Objectives

  -------------------- --------------- --------------------- --------------- ---------------
  **Requirement**      **Frequency**   **Acceptance          **Reference**   **Information
                                       Criteria**                            or Action**

  Bias                 NCORE, once per To be determined.     40 CFR Pt.58    To be
                       year                                                  determined.

  Precision            1 every 2 weeks Concentration: 0.0003 40 CFR Pt.58    To be
                                       -0.005 ppm,           Appendix A      determined.
                                       Coefficient of                        
                                       Variance: To be                       
                                       determined.                           

  Completeness         Quarterly,      NCORE, 75%            National        If under 75%,
                       Annually                              Monitoring      institute
                                                             Strategy.       Quality Control
                                                                             Measures

  Representativeness   N/A             Neighborhood, Urban   40 CFR 58       N/A
                                       or Regional Scale                     

  Comparability        N/A             Must be a Trace Level National        N/A
                                       instrument. See       Monitoring      
                                       Sections 3.1 and 3.2  Strategy.       
                                       of this document.                     

  Method Detection     N/A             300 ppt               National        Testing is
  Limit                                                      Monitoring      performed at
                                                             Strategy        the factory.
  -------------------- --------------- --------------------- --------------- ---------------

**5.0 REFERENCES**

1.  Code of Federal Regulations, Title 40, Part 53.23c

> 2\. Code of Federal Regulation, Title 40, Part 58, Appendix A
>
> 3\. The National Air Monitoring Strategy, Final Draft, 4/29/04,
> <http://www.epa.gov/ttn/amtic/monstratdoc.html>
>
> 4\. Instruction Manual, Model 43C Trace Level SO~2~ Analyzer
>
> 5\. Trace SO~2~ Monitoring Guidance for the MANE-VU Regional Aerosol
> Intensive Network (RAIN) program, Draft (dated March 7, 2005).
>
> **Appendix A**Number range CHAPTER

Environmental Protection Agency

Monthly Quality Control and Maintenance Records

Thermo 43C-TLE SO~2~ Analyzer

Site Name/Location
[\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_]{.underline}

Technician\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_

Month/Year\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_

Serial Number Range\_\_\_\_\_\_\_\_\_\_\_\_\_\_

  --------------- ------------- -------------- -------------- ---------------
  **Parameter**   **Date**      **Date**       **Date**       **Acceptance
                                                              Criteria**

  DC Voltage                                                  

  PMT Voltage                                                 

  Internal Temp                                               

  Chamber Temp                                                

  Chamber                                                     
  Pressure                                                    

  Sample Flow                                                 

  UV Lamp                                                     
  Intensity                                                   

                                                              

  Other Tests                                                 

  Optical Span                                                
  Test                                                        
  --------------- ------------- -------------- -------------- ---------------

  ------------ ----------------------------------------------------------
  **Date**     **Comments and Notes**

               

               

               

               
  ------------ ----------------------------------------------------------

**Figure A-1 Thermo 43C-TLE Quality Control and Maintenance Record**