METHOD TO-1 Revision 1.0
April, 1984 METHOD FOR THE DETERMINATION OF VOLATILE ORGANIC COMPOUNDS IN AMBIENT AIR USING TENAX? ADSORPTION AND
GAS CHROMATOGRAPHY/MASS SPECTROMETRY (GC/MS)
1.Scope
1.1The document describes a generalized protocol for
collection and determination of certain volatile organic
compounds which can be captured on Tenax? GC (poly(2,6-
Diphenyl phenylene oxide)) and determined by thermal
desorption GC/MS techniques. Specific approaches using
these techniques are described in the literature (1-3).
1.2This protocol is designed to allow some flexibility in
order to accommodate procedures currently in use.
However, such flexibility also results in placement of
considerable responsibility with the user to document
that such procedures give acceptable results (i.e.,
documentation of method performance within each
laboratory situation is required). Types of
documentation required are described elsewhere in this
method.
1.3Compounds which can be determined by this method are
nonpolar organics having boiling points in the range of
approximately 80E - 200E C. However, not all compounds
falling into this category can be determined. Table 1
gives a listing of compounds for which the method has
been used. Other compounds may yield satisfactory
results but validation by the individual user is
required.
2.Applicable Documents
2.1ASTM Standards:
D1356Definitions of Terms Related to Atmospheric
Sampling and Analysis.
E355Recommended Practice for Gas Chromatography
Terms and Relationships.
2.2Other documents:
Existing procedures (1-3).
U. S. EPA Technical Assistance Document (4).
3.Summary of Protocol
3.1Ambient air is drawn through a cartridge containing -1-2
grams of Tenax and certain volatile organic compounds are
trapped on the resin while highly volatile organic
compounds and most inorganic atmospheric constituents
pass through the cartridge. The cartridge is then
transferred to the laboratory and analyzed.
3.2For analysis the cartridge is placed in a heated chamber
and purged with an inert gas. The inert gas transfers
the volatile organic compounds from the cartridge onto a
cold trap and subsequently onto the front of the GC
column which is held at low temperature (e.g., -70E C).
the GC column temperature is then increased (temperature
programmed) and the components eluting from the column
are identified and quantified by mass spectrometry.
Component identification is normally accomplished, using
a library search routine, on the basis of the GC
retention time and mass spectral characteristics. Less
sophisticated detectors (e.g., electron capture or flame
ionization) may be used for certain applications but
their suitability for a given application must be
verified by the user.
3.3Due to the complexity of ambient air samples only high
resolution (i.e., capillary) GC techniques are considered
to be acceptable in this protocol.
4.Significance
4.1Volatile organic compounds are emitted into the
atmosphere from a variety of sources including industrial
and commercial facilities, hazardous waste storage
facilities, etc. Many of these compounds are toxic;
hence knowledge of the levels of such materials in the
ambient atmosphere is required in order to determine
human health impacts.
4.2Conventional air monitoring methods (e.g., for workspace
monitoring) have relied on carbon adsorption approaches
with subsequent solvent desorption. Such techniques
allow subsequent injection of only a small portion,
typically 1-5% of the sample onto the GC system.
However, typical ambient air concentrations of these
compounds require a more sensitive approach. The thermal
desorption process, wherein the entire sample is
introduced into the analytical (GC/MS) system fulfills
this need for enhanced sensitivity.
5.Definitions
Definitions used in this document and any user prepared SOPs should be consistent with ASTM D1356(6). All abbreviations and symbols are defined with this document at the point of use.
6.Interferences
6.1Only compounds having a similar mass spectrum and GC
retention time compared to the compound of interest will
interface in the method. The most commonly encountered
interferences are structural isomers.
6.2Contamination of the Tenax cartridge with the compound(s)
of interest is a commonly encountered problem in the
method. The user must be extremely careful in the
preparation, storage, and handling of the cartridges
throughout the entire sampling and analysis process to
minimize this problem.
7.Apparatus
7.1Gas Chromatograph/Mass Spectrometry system - should be
capable of subambient temperature programming. Unit mass
resolution or better up to 800 amu. Capable of scanning
30-400 amu region every 0.5-1 second. Equipped with data
system for instrument control as well as data
acquisition, processing and storage.
7.2Thermal Desorption Unit - Designed to accommodate Tenax
cartridges in use. See Figure 2a or b.
7.3Sampling System - Capable of accurately and precisely
drawing an air flow of 10-500 ml/minute through the Tenax
cartridge. (See Figure 3a or b.)
7.4Vacuum oven - connected to water aspirator vacuum supply.
7.5Stopwatch.
7.6Pyrex disks - for drying Tenax.
7.7Glass jar - Capped with Teflon-lined screw cap. For
storage of purified Tenax.
7.8Powder funnel - for delivery of Tenax into cartridges.
7.9Culture tubes - to hold individual glass Tenax
cartridges.
7.10Friction top can (paint can) - to hold clean Tenax
cartridges.
7.11Filter holder - stainless steel or aluminum (to
accommodate 1 inch diameter filter). Other sizes may be used if desired. (optional)
7.12Thermometer - to record ambient temperature.
7.13Barometer (optional).
7.14Dilution bottle - Two-liter with septum cap for standards
preparation.
7.15Teflon stirbar - 1 inch long.
7.16Gas-tight glass syringes with stainless steel needles -
10-500 μ1 for standard injection onto GC/MS system.
7.17Liquid microliter syringes - 5.50 μL for injecting neat
liquid standards into dilution bottle.
7.18Oven - 60 + 5E C for equilibrating dilution flasks.
7.19Magnetic stirrer.
7.20Heating mantel.
7.21Variac
7.22Soxhlet extraction apparatus and glass thimbles - for
purifying Tenax.
7.23Infrared lamp - for drying Tenax.
7.24GC column - SE-30 or alternative coating, glass capillary
or fused silica.
7.25Psychrometer - to determine ambient relative humidity.
(optional)
8.Reagents and Materials
8.1Empty Tenax cartridges - glass or stainless steel (see
Figure 1a or b).
8.2Tenax 60/80 mesh (2,6-diphenylphenylene oxide polymer).
8.3Glasswool - silanized.
8.4Acetone - Pesticide quality or equivalent.
8.5Methanol - Pesticide quality or equivalent.
8.6Pentane - Pesticide quality or equivalent.
8.7Helium - Ultra pure, compressed gas. (99.9999%)
8.8Nitrogen - Ultra pure, compressed gas. (99.9999%)
8.9Liquid nitrogen.
8.10Polyester gloves - for handling glass Tenax cartridges.
8.11Glass Fiber Filter - one inch diameter, to fit in filter
holder. (optional)
8.12Perfluorotributylamine (FC-43).
8.13Chemical Standards - Neat compounds of interest. Highest
purity available.
8.14Granular activated charcoal - for preventing
contamination of Tenax cartridges during storage.
9.Cartridge Construction and Preparation
9.1Cartridge Design
9.1.1Several cartridge designs have been reported
in the literature (1-3). The most common (1)
is shown in Figure 1a. This design minimizes
contact of the sample with metal surfaces,
which can lead to decomposition in certain
cases. However, a disadvantage of this design
is the need to rigorously avoid contamination
of the outside portion of the cartridge since
the entire surface is subjected to the purge
gas stream during the desorption process.
Clean polyester gloves must be worn at all
times when handling such cartridges and
exposure of the open cartridge to ambient air
must be minimized.
9.1.2 A second common type of design (3) is shown in
Figure 1b. While this design uses a metal
(stainless steel) construction, it eliminates
the need to avoid direct contact with the
exterior surface since only the interior of
the cartridge is purged.
9.1.3The thermal desorption module and sampling
system must be selected to be compatible with
the particular cartridge design chosen.
Typical module designs are shown in Figure 2a
and b. These designs are suitable for the
cartridge designs shown in Figures 1a and b,
respectively.
9.2Tenax Purification
9.2.1Prior to use the Tenax resin is subjected to a
series of solvent extraction and thermal
treatment steps. The operation should be
conducted in an area where levels of volatile
organic compounds (other than the extraction
solvents used) are minimized.
9.2.2All glassware used in Tenax purification as
well as cartridge materials should be
thoroughly cleaned by water rinsing followed
by an acetone rinse and dried in an oven at
250E C.
9.2.3Bulk Tenax is placed in a glass extraction
thimble and held in place with a plug of clean
glasswool. The resin is then placed in the
soxhlet extraction apparatus and extracted
sequentially with methanol and then pentane
for 16-24 hours (each solvent) at
approximately 6 cycles/hour. Glasswool for
cartridge preparation should be cleaned in the
same manner as Tenax.
9.2.4The extracted Tenax is immediately placed in
an open glass dish and heated under an
infrared lamp for two hours in a hood. Care
must be exercised to avoid over heating of the
Tenax by the infrared lamp. The Tenax is then
placed in a vacuum oven (evacuated using a
water aspirator) without heating for one hour.
An inert gas (helium or nitrogen) purge of 2-3
ml/minute is used to aid in the removal of
solvent vapors. The oven temperature is then
increased to 110E C, maintaining inert gas flow
and held for one hour. The oven temperature
control is then shut off and the oven is
allowed to cool to room temperature. Prior to
opening the oven, the oven is slightly
pressurized with nitrogen to prevent
contamination with ambient air. The Tenax is
removed from the oven and sieved through a
40/60 mesh sieve (acetone rinsed and oven
dried) into a clean glass vessel. If the
Tenax is not to be used immediately for
cartridge preparation it should be stored in a
clean glass jar having a Teflon-lined screw
cap and placed in a desiccator.
9.3Cartridge Preparation and Pretreatment
9.3.1All cartridge materials are pre-cleaned as
described in Section 9.2.2. If the glass
cartridge design shown in Figure 1a is
employed all handling should be conducted
wearing polyester gloves.
9.3.2The cartridge is packed by placing a 0.5-lcm
glasswool plug in the base of the cartridge
and then filling the cartridge to within
approximately 1 cm of the top. A 0.5-1cm
glasswool plug is placed in the top of the
cartridge.
9.3.3The cartridges are then thermally conditioned
by heating for four hours at 270E C under an
inert gas (helium) purge (100 - 200 ml/min).
9.3.4After the four hour heating period the
cartridges are allowed to cool. Cartridges of
the type shown in Figure 1a are immediately
placed (without cooling) in clean culture
tubes having Teflon-lined screw caps with a
glasswool cushion at both the top and the
bottom. Each tube should be shaken to ensure
that the cartridge is held firmly in place.
Cartridges of the type shown in Figure 1b are
allowed to cool to room temperature under
inert gas purge and are then closed with
stainless steel plugs.
V MAX '
V
b
xW
9.3.5The cartridges are labeled and placed in a
tightly sealed metal can (e.g., paint can or
similar friction top container). For
cartridges of the type shown in Figure 1a the
culture tube, not the cartridge, is labeled.
9.3.6Cartridges should be used for sampling within
2 weeks after preparation and analyzed within
two weeks after sampling. If possible the
cartridges should be stored at -20E C in a
clean freezer (i.e., no solvent extracts or
other sources of volatile organics contained
in the freezer).
10.Sampling
10.1Flow Rate and Total Volume Selection
10.1.1Each compound has a characteristic retention
volume (liters of air per gram of adsorbent)
which must not be exceeded. Since the
retention volume is a function of temperature,
and possibly other sampling variables, one
must include an adequate margin of safety to
ensure good collection efficiency. Some
considerations and guidance in this regard
areprovided in a recent report (5).
Approximate breakthrough volumes at 38E C
(100E F) in liters/gram of Tenax are provided
in Table 1. These retention volume data are
supplied only as rough guidance and are
subject to considerable variability, depending
on cartridge design as well as sampling
parameters and atmospheric conditions.
10.1.2To calculate the maximum total volume of air
which can be sampled use the following
equation:
where
V is the calculated maximum total volume in
MAX
liters.
V is the breakthrough volume for the least
b
retained compound of interest (Table 1)
in liters per gram of Tenax.
W is the weight of Tenax in the cartridge,
in grams.
Q MAX '
V
MAX
t
x1000 B'
Q
MAX
B r2
1.5 is a dimensionless safety factor to allow
for variability in atmospheric conditions.
This factor is appropriate for temperatures in
the range of 25-30E C. If higher temperatures
are encountered the factor should be increased
(i.e. maximum total volume decreased).
10.1.3To calculate maximum flow rate use the
following equation:
where
Q is the calculated maximum flow rate in
MAX
milliliters per minute.
t is the desired sampling time in minutes.
Times greater than 24 hours (1440
minutes) generally are unsuitable because
the flow rate required is too low to be
accurately maintained.
10.1.4The maximum flow rate Q should yield a
MAX
linear flow velocity of 50-500 cm/minute.
Calculate the linear velocity corresponding to
the maximum flow rate using the following
equation:
where
B is the calculated linear flow velocity in
centimeters per minute.
r is the internal radius of the cartridge
in centimeters.
If B is greater then 500 centimeters per
minute either the total sample flow rate (V)
MAX
should be reduced or the sample flow rate
(Q) should be reduced by increasing the
MAX
collection time. If B is less then 50
centimeters per minute the sampling rate (Q)
MAX
should be increased by reducing the sampling
time. The total sample value (V) cannot be
MAX
increased due to component breakthrough.
10.1.5The flow rate calculated as described above
defines the maximum flow rate allowed. In
general, one should collect additional samples
in parallel, for the same time period but at
lower flow rates. This practice yields a
measure of quality control and is further
discussed in the literature (5). In general,
flow rates 2 to 4 fold lower than the maximum
flow rate should be employed for the parallel
samples. In all cases a constant flow rate
should be achieved for each cartridge since
accurate integration of the analyte
concentration requires that the flow be
constant over the sampling period.
10.2Sample Collection
10.2.1Collection of an accurately known volume of
air is critical to the accuracy of the
results. For this reason the use of mass flow
controllers, rather than conventional needle
valves or orifices is highly recommended,
especially at low flow velocities (e.g., less
than 100 milliliters/minute). Figure 3a
illustrates a sampling system utilizing mass
flow controllers. This system readily allows
for collection of parallel samples. Figure 3b
shows a commercially available system based on
needle valve flow controllers.
10.2.2Prior to sample collection insure that the
sampling flow rate has been calibrated over a
range including the rate to be used for
sampling, with a "dummy" Tenax cartridge in
place. Generally calibration is accomplished
using a soap bubble flow meter or calibrated
wet test meter. The flow calibration device
is connected to the flow exit, assuming the
entire flow system is sealed. ASTM Method
D3686 describes an appropriate calibration
scheme, not requiring a sealed flow system
downstream of the pump.
10.2.3The flow rate should be checked before and
after each sample collection. If the sampling
interval exceeds four hours the flow rate
should be checked at an intermediate point
during sampling as well. In general, a
rotameter should be included, as shown in
Figure 3b, to allow observation of the
sampling flow rate without disrupting the
sampling process.
10.2.4To collect an air sample the cartridges are
removed from the sealed container just prior
to initiation of the collection process. If
glass cartridges (Figure 1a) are employed they
must be handled only with polyester gloves and
should not contact any other surfaces.
10.2.5 A particulate filter and holder are placed on
the inlet to the cartridges and the exit end
of the cartridge is connected to the sampling
apparatus. In many sampling situations the
use of a filter is not necessary if only the
total concentration of a component is desired.
Glass cartridges of the type shown in Figure
1a are connected using teflon ferrules and
Swagelok (stainless steel or teflon) fittings.
Start the pump and record the following
parameters on an appropriate data sheet
(Figure 4): data, sampling location, time,
ambient temperature, barometric pressure,
relative humidity, dry gas meter reading (if
applicable), flow rate, rotameter reading (if
applicable), cartridge number and dry gas
meter serial number.
10.2.6Allow the sampler to operate for the desired
time, periodically recording the variables
listed above. Check flow rate at the midpoint
of the sampling interval if longer than four
hours. At the end of the sampling period
record the parameters listed in 10.2.5 and
check the flow rate and record the value. If
the flows at the beginning and end of the
sampling period differ by more than 10% the
cartridge should be marked as suspect.
10.2.7Remove the cartridges (one at a time) and
place in the original container (use gloves
for glass cartridges). Seal the cartridges or
culture tubes in the friction-top can
containing a layer of charcoal and package for
immediate shipment to the laboratory for
analysis. Store cartridges at reduced
temperature (e.g., -20E C) before analysis if
possible to maximize storage stability.
Q A '
Q
1
%Q
2
%...Q
N
N
V
m
'
T×Q
A
V s 'V
m
×
P
A
760
×
298
273%t
A
10.2.8Calculate and record the average sample rate
for each cartridge according to the following
equation:
where
Q = Average flow rate in ml/minute.
A
Q, Q, ....Q = Flow rates determined at 12N
beginning, end, and intermediate points during
sampling.
N = Number of points averaged.
10.2.9Calculate and record the total volumetric flow
for each cartridge using the following
equation:
where
V =Total volume sampled in liters at
m
measured temperature and pressure.
T =Stop time.
2
T =Start time.
1
T =Sampling time = T = T, minutes
21
10.2.10The total volume (V) at standard conditions,
s
25E C and 760 mmHg, is calculated from the
following equation:
where
P = Average barometric pressure, mmHg
A
t = Average ambient temperature, E C.
A
11.GC/MS Analysis
11.1Instrument Set-up
11.1.1Considerable variation from one laboratory to
another is expected in terms of instrument
configuration. Therefore each laboratory must
be responsible for verifying that their
particular system yields satisfactory results.
Section 14 discusses specific performance
criteria which should be met.
11.1.2 A block diagram of the typical GC/MS system
required for analysis of Tenax cartridges is
depicted in Figure 5. The operation of such
devices is described in 11.2.4. The thermal
desorption module must be designed to
accommodate the particular cartridge
configuration. Exposure of the sample to
metal surfaces should be minimized and only
stainless steel, or nickel metal surfaces
should be employed. The volume of tubing and
fittings leading from the cartridge to the GC
column must be minimized and all areas must be
well-swept by helium carrier gas.
11.1.3The GC column inlet should be capable of being
cooled to -70E C and subsequently increased
rapidly to approximately 30E C. This can be
most readily accomplished using a GC equipped
with subambient cooling capability (liquid
nitrogen) although other approaches such as
manually cooling the inlet of the column in
liquid nitrogen may be acceptable.
11.1.4The specific GC column and temperature program
employed will be dependent on the specific
compounds of interest. Appropriate conditions
are described in the literature (1-3). In
general a nonpolar stationary phase (e.g., SE-
30, OV-1) temperature programmed from 30E C to
200E C at 8E/minute will be suitable. Fused
silica bonded phase columns are preferable to
glass columns since they are more rugged and
can be inserted directly into the MS ion
source, thereby eliminating the need for a
GC/MS transfer line.
11.1.5Capillary column dimensions of 0.3 mm ID and
50 meters long are generally appropriate
although shorter lengths may be sufficient in
many cases.
11.1.6Prior to instrument calibration or sample
analysis the GC/MS system is assembled as
shown in Figure 5. Helium purge flows
(through the cartridge) and carrier flow are
set at approximately 10 ml/minute and 1-2
ml/minute respectively. If applicable, the
injector sweep flow is set at 2-4 ml/minute.
11.1.7Once the column and other system components
are assembled and the various flows
established the column temperature is
increased to 250E C for approximately four
hours (or overnight if desired) to condition
the column.
11.1.8The MS and data system are set according to
the manufacturer's instructions. Electron
impact ionization (70eV) and an electron
multiplier gain of approximately 5 x 10 should
4
be employed. Once the entire GC/MS system has
been setup the system is calibrated as
described in Section 11.2. The user should
prepare a detailed standard operating
procedure (SOP) describing this process for
the particular instrument being used.
11.2Instrument Calibration
11.2.1Tuning and mass standardization of the MS
system is performed according to
manufacturer's instructions and relevant
information from the user prepared SOP.
Perfluorotributylamine should generally be
employed for this purpose. The material is
introduced directly into the ion source though
a molecular leak. The instrumental parameters
(e.g., lens voltages, resolution, etc.) should
be adjusted to give the relative ion
abundances shown in Table 2 as well as
acceptable resolution and peak shape. If
these approximate relative abundances cannot
be achieved, the ion source may require
cleaning according to manufacturer's
instructions. In the event that the user's
instrument cannot achieve these relative ion
abundances, but is otherwise operating
properly, the user may adopt another set of
relative abundances as performance criteria.
However, these alternate values must be
repeatable on a day-to-day basis.
11.2.2After the mass standardization and tuning
process has been completed and the appropriate
values entered into the data system the user
should then calibrate the entire system by
introducing known quantities of the standard
components of interest into the system. Three
alternate procedures may be employed for the
calibration process including 1) direct
syringe injection of dilute vapor phase
standards, prepared in a dilution bottle, onto
the GC column, 2) injection of dilute vapor
phase standards into a carrier gas stream
directed through the Tenax cartridge, and 3)
introduction of permeation or diffusion tube
standards onto a Tenax cartridge. The
standards preparation procedures for each of
these approaches are described in Section 13.
The following paragraphs describe the
instrument calibration process for each of
these approaches.
11.2.3If the instrument is to be calibrated by
direct injection of a gaseous standard, a
standard is prepared in a dilution bottle as
described in Section 13.1. The GC column is
cooled to -70E C (or, alternately, a portion of
the column inlet is manually cooled with
liquid nitrogen). The MS and data system is
set up for acquisition as described in the
relevant user SOP. The ionization filament
should be turned off during the initial 2-3
minutes of the run to allow oxygen and other
highly volatile components to elute. An
appropriate volume (less than 1 ml) of the
gaseous standard is injected onto the GC
system using an accurately calibrated gas
tight syringe. The system clock is started
and the column is maintained at -70E C (or
liquid nitrogen inlet cooling) for 2 minutes.
The column temperature is rapidly increased to
the desired initial temperature (e.g., 30E C).
The temperature program is started at a
consistent time (e.g., four minutes) after
injection. Simultaneously the ionization
filament is turned on and data acquisition is
initiated. After the last component of
interest has eluted acquisition is terminated
and the data is processed as described in
Section 11.2.5. The standard injection
process is repeated using different standard
volumes as desired.
11.2.4If the system is to be calibrated by analysis
of spiked Tenax cartridges a set of cartridges
is prepared as described in Sections 13.2 or
13.3. Prior to analysis the cartridges are
stored as described in Section 9.3. If glass
cartridges (Figure 1a) are employed care must
be taken to avoid direct contact, as described
earlier. The GC column is cooled to -70E C,
the collection loop is immersed in liquid
nitrogen and the desorption module is
maintained at 250E C. The inlet valve is
placed in the desorb mode and the standard
cartridge is placed in the desorption module,
making certain that no leakage or purge gas
occurs. The cartridge is purged for 10
minutes and then the inlet valve is placed in
the inject mode and the liquid nitrogen source
removed from the collection trap. The GC
column is maintained at -70E C for two minutes
and subsequent steps are as described in
11.2.3. After the process is complete the
cartridge is removed from the desorption
module and stored for subsequent use as
described in Section 9.3.
11.2.5Data processing for instrument calibration
involves determining retention times, and
integrated characteristic ion intensities for
each of the compounds of interest. In
addition, for at least one chromatographic
run, the individual mass spectra should be
inspected and compared to reference spectra to
ensure proper instrumental performance. Since
the steps involved in data processing are
highly instrument specific, the user should
prepare a SOP describing the process for
individual use. Overall performance criteria
for instrument calibration are provided in
Section 14. If these criteria are not
achieved the user should refine the
instrumental parameters and/or operating
procedures to meet these criteria.
11.3Sample Analysis
11.3.1The sample analysis process is identical to
that described in Section 11.2.4 for the
analysis of standard Tenax cartridges.
11.3.2Data processing for sample data generally
involves 1) qualitatively determining the
presence or absence of each component of
interest on the basis of a set of
characteristic ions and the retention time
using a reverse-search software routine, 2)
quantification of each identified component by
integrating the intensity of a characteristic
ion and comparing the value to that of the
calibration standard, and 3) tentative
identification of other components observed
using a forward (library) search software
routine. As for other user specific
processes, a SOP should be prepared describing
the specific operations for each individual
laboratory.
12.Calculations
12.1Calibration Response Factors
12.1.1Data from calibration standards is used to
calculate a response factor for each component
of interest. Ideally the process involves
analysis of at least three calibration levels
of each component during a given day and
determination of the response factor
(area/nanogram injected) from the linear least
squares fit of a plot of nanograms injected
versus area (for the characteristic ion). In
general quantities of component greater than
1000 nanograms should not be injected because
of column overloading and/or MS response
nonlinearity.
12.1.2In practice the daily routine may not always
allow analysis of three such calibration
standards. In this situation calibration data
from consecutive days may be pooled to yield a
response factor, provided that analysis of
replicate standards of the same concentration
are shown to agree within 20% on the
consecutive days. One standard concentration,
near the midpoint of the analytical range of
interest, should be chosen for injection every
day to determine day-to-day response
reproducibility.
Y'A%BX%CX2
Y A 'A%BX
A
%CX
A
C
A
'
X
A
S
12.1.3If substantial nonlinearity is present in the
calibration curve a nonlinear least squares
fit (e.g., quadratic) should be employed.
This process involves fitting the data to the
following equation:
where
Y = peak area
X = quantity of component, nanograms
A, B, and C are coefficients in the equation 12.2Analyte Concentrations
12.2.1Analyte quantities on a sample cartridge are
calculated from the following equation:
where
Y is the area of the analyte characteristic ion
A
for the sample cartridge.
X is the calculated quantity of analyte on the
A
sample cartridge, in nanograms.
A, B, and C are the coefficients calculated from
the calibration curve described in Section 12.1.3.
12.2.2If instrumental response is essentially linear
over the concentration range of interest a
linear equation (C=O in the equation above)
can be employed.
12.2.3Concentration of analyte in the original air
sample is calculated from the following
equation:
where
C is the calculated concentration of analyte in
A
nanograms per liter.
V and X are as previously defined in Section
S A
10.2.10 and 12.2.1, respectively.
W T '
W
I
V
I
×V
B
V T '
W
T
13.Standard Preparation
13.1Direct Injection
13.1.1This process involves preparation of a
dilution bottle containing the desired
concentrations of compounds of interest for
direct injection onto the GC/MS system.
13.1.2Fifteen three-millimeter diameter glass beads
and a one-inch Teflon stirbar are placed in a
clean two-liter glass septum capped bottle and
the exact volume is determined by weighing the
bottle before and after filling with deionized
water. The bottle is then rinsed with acetone
and dried at 200E C.
13.1.3The amount of each standard to be injected
into the vessel is calculated from the desired
injection quantity and volume using the
following equation:
where
W is the total quantity of analyte to be
T
injected into the bottle in milligrams
W is the desired weight of analyte to be
I
injected onto the GC/MS system or spiked
cartridge in nanograms
V is the desired GC/MS or cartridge injection
I
volume (should not exceed 500) in microliters.
V is total volume of dilution bottle determined
B
in 13.1.1, in liters.
13.1.4The volume of the neat standard to be injected
into the dilution bottle is determined using
the following equation:
where
V is the total volume of neat liquid to be
T
injected in microliters.
d is th
e density o
f the neat standard in grams
per milliliter.
13.1.6The bottle is placed in a 60E C oven for at
least 30 minutes prior to removal of a vapor
phase standard.
13.1.7To withdraw a standard for GC/MS injection the
bottle is removed from the oven and stirred
for 10-15 seconds. A suitable gas-tight
microber syringe, warmed to 60E C, is inserted
through the septum cap and pumped three times
slowly. The appropriate volume of sample
(approximately 25% larger than the desired
injection volume) is drawn into the syringe
and the volume is adjusted to the exact value
desired and then immediately injected over a
5-10 seconds period onto the GC/MS system as
described in Section 11.2.3.
13.2Preparation of Spiked Cartridges by Vapor Phase Injection
13.2.1This process involves preparation of a
dilution bottle containing the desired
concentrations of the compound(s) of interest
as described in 13.1 and injecting the desired
volume of vapor into a flowing inert gas
stream directed through a clean Tenax
cartridge.
13.2.2 A helium purge system is assembled wherein the
helium flow 20-30 mL/minute is passed through
a stainless steel Tee fitted with a septum
injector. The clean Tenax cartridge is
connected downstream of the tee using
appropriate Swagelok fittings. Once the
cartridge is placed in the flowing gas stream
the appropriate volume vapor standard, in the
dilution bottle, is injected through the
septum as described in 13.1.6. The syringe is
flushed several times by alternately filling
the syringe with carrier gas and displacing
the contents into the flow stream, without
removing the syringe from the septum. Carrier
flow is maintained through the cartridge for
approximately 5 minutes after injection.
13.3Preparation of Spiked Traps Using Permeation or Diffusion
Tubes
13.3.1 A flowing stream of inert gas containing known
amounts of each compound of interest is
generated according to ASTM Method D3609(6).
大气固定污染源氟化物的测定离子选择电极法 HJ/T67-2001方法确认 1.目的 通过离子选择电极法测定吸收液中氟离子的浓度，分析方法检出限、回收率及精密度，判断本实验室的检测方法是否合格 2.适用范围 本标准适用于大气固定污染源有组织排放中氟化物的测定。不能测定碳氟化物，如氟利昂。 3. 职责 3.1 检测人员负责按操作规程操作，确保测量过程正常进行，消除各种可能影响试验 结果的意外因素，掌握检出限、方法回收率与精密度的计算方法。 3.2 复核人员负责检查原始记录、检出限、方法回收率及精密度的计算方法。 3.3技术负责人负责审核检测结果及检出限、方法回收率、精密度分析结果 4.分析方法 4.1 测量方法简述 4.1.2 样品的采集和保存 污染源中尘氟和气态氟共存时，采样烟尘采样方法进行等速采样，在采样管的出口串联三个装有75ml吸收液的大型冲击式吸收瓶，分别捕集尘氟和气态氟。 若污染源中只存在气态氟时，可采用烟气采样方法，在采集管出口串联两个装有50ml吸收液的多孔玻板吸收瓶，以0.5~2.0L/min的流速采集5~20min。 采样管与吸收瓶之间的连接管，选用聚四氟乙烯管，并应尽量短。 注：连接管液可使用聚乙烯塑料管和橡胶管。 采样点数目，采样点位设置及操作步骤，按GB/T 16157-1996《固定污染源排气中颗粒物的测定和气态污染物采样方法》有关规定进行。采样频次和时间，按GB 16297-1996 《大气污染物综合排放标准》有关规定进行。 采样结束后，将滤筒取出，编号后放入干燥洁净的器皿中，并按照采样要求，做好记录。吸收瓶中的样品全部转移至聚乙烯瓶中，并用少量水洗涤三次吸收瓶，洗涤液并入聚乙烯瓶中。编号做好记录。采样管与连接管先用50ml吸收液洗涤，再用400ml 水冲洗，全部并入聚乙烯瓶中，编号做好记录。样品常温下可保存一周。 4.1.3 分析步骤 取6个50ml聚乙烯烧杯，按表1配制标准系列，也可根据实际样品浓度配制，
环境空气中臭氧的测定（HJ 504-2009） —靛蓝二磺酸钠分光光度法 一、实验目的 1、掌握靛蓝二磺酸钠分光光度法测定环境空气中臭氧含量的原理和方法； 2、熟练掌握滴定操作； 3、熟练掌握采样仪器和分光光度计的操作。 二、实验前准备 1、试剂 （1）溴酸钾标准贮备溶液[c(1/6 KBrO3)=0.100 0 mol/L]准确称取1.391 8 g 溴化钾（优级纯，180℃烘 2 h），置烧杯中，加入少量水溶解，移入500ml 容量瓶中，用水稀释至标线。 （2）溴酸钾-溴化钾标准溶液[c(1/6 KBrO5)= 0.010 0 mol/L]吸取10.00 ml溴酸钾标准贮备溶液于100 ml 容量瓶中，加入1.0g溴化钾（KBr），用水稀释至标线。 （3）硫代硫酸钠标准贮备溶液[c(Na2S2O3)= 0.1000 mol/L]。（4）硫代硫酸钠标准工作溶液[c(Na2S2O3)= 0.00500 mol/L]临用前，取硫代硫酸钠标准贮备溶液用新煮沸并冷却到室温的水准确稀释 20 倍。 （5）硫酸溶液，1+6。 （6）淀粉指示剂溶液[ρ =2.0 g/L]称取0.20g可溶性淀粉，用少量水调成糊状，慢慢倒入100 ml 沸水,煮沸至溶液澄清。
（7）磷酸盐缓冲溶液，[c(KH2PO4-Na2HPO4)=0.050 mol/L]称取6.8 g磷酸二氢钾（KH2PO4）、7.1 g无水磷酸氢二钠（Na2HPO4），溶于水，稀释至1000 ml。 （8）靛蓝二磺酸钠（C16H8O8Na2S2）（简称 IDS），分析纯、化学纯或生化试剂。 （9）IDS 标准贮备溶液：称取0.25g靛蓝二磺酸钠溶于水，移入500 ml棕色容量瓶内，用水稀释至标线，摇匀，在室温暗处存放24 h后标定。此溶液在20℃以下暗处存放可稳定2周。 标定方法：准确吸取20.00 ml IDS 标准贮备溶液于250 ml碘量瓶中，加入20.00 ml溴酸钾-溴化钾溶液再加入50 ml水，盖好瓶塞，在 16℃±1℃生化培养箱（或水浴中放置至溶液温度与水浴温度平衡时[注1]，加入5.0 ml硫酸溶液，立即盖塞、混匀并开始计时，于 16℃±1℃暗处放置35 min±1.0 min后，加入1.0 g碘化钾，立即盖塞，轻轻摇匀至溶解，暗处放置5min，用硫代硫酸钠溶液滴定至棕色刚好褪去呈淡黄色，加入5ml淀粉指示剂溶液，继续滴定至蓝色消退，终点为亮黄色。记录所消耗的硫代硫酸钠标准工作溶液的体积[注2]。注1：达到平衡的时间与温差有关，可以预先用相同体积的水代替溶液，加入碘量瓶中，放入温度计观察达到平衡(HJ 504—2009)所需要的时间。 注2：平行滴定所消耗的硫代硫酸钠标准溶液体积不应大 0.10 ml。每毫升靛蓝二磺酸钠溶液相当于臭氧的质量浓度ρ（μg/ml）计算： ρ =(C?V?-C?V?/V)×12.00×1000
硫化氢的测定 (依据GB/T 14678-93) 1适用范围 本方法适用于恶臭污染源排气和环境空气中硫化氢、甲硫醇和二甲 二硫的测定。气相色谱仪的火焰光度检测器对四种成分的检出限为0.2×10-9—1.0×10-9g，当气体样品中四种成分浓度高于1.0mg/m3时，可取1-2ml气体样品直接注入气相色谱仪分析。对1L气体样品进行 浓缩，四种成分的方法检出限分别为0.2×10-9-1.0×10-9mg/m3。 2原理 本方法以经真空处理的1L采气瓶采集无组织排放源恶臭气体或环 境空气样品，以聚酯塑料袋采集排气筒内恶臭气体样品。硫化物含 量较高的气体样品可直接用注射器取样1-2ml，注入安装火焰光度检测器（FPD）的气相色谱仪分析。当直接进样体积中硫化物绝对量 低于仪器检出限时，则需以浓缩管在以液氧为致冷剂的低温条件下 对1L气体样品中的硫化物进行浓缩，浓缩后将浓缩管连入色谱仪分析系统并加热至100℃，使全部浓缩成分流经色谱柱分离，由FPD 对各种硫化物进行定量分析。在一定浓度范围内，各种硫化物含量 的对数与色谱峰高的对数成正比。 3试剂和材料 3.1试剂 3.1.1苯（C6H6）分析纯（有毒），经色谱检验无干扰峰。如有干 扰峰则需用全玻璃蒸馏器重新蒸馏。 3.1.2硫化氢（H2S）：纯度大于99.9%，实验室制备的硫化氢需进 行标定。 3.1.3甲硫醇（CH3SH）:分析纯 3.1.4甲硫醚[(CH3)2S]:分析纯 3.1.5二甲二硫[(CH3)2S2]:分析纯 3.1.6磷酸（H3SO4）:分析纯 3.1.7丙酮（CH3COCH3）:分析纯 3.1.8液态氮 3.2色谱仪载气和辅助气体 3.2.1载气：氮气，纯度99.99%，用装5A分子筛净化管净化。
环境空气氟化物测定复习试题 滤膜·离子选择电极法 一、填空题 1.中华人民共国国家标准GB15434-1995中规定氟化物是指空气中存在的、及。 答：气态氟化物；溶于盐酸溶液的颗粒态氟化物 2.采样时，在滤膜夹中装入两张浸渍滤膜，中间隔㎜，以 L/min流量，采气103以上。 答：磷酸氢二钾；2～3；100～120 3.样品测定时，将样品膜剪成，放入50mL 杯中，加入溶液20mL，在超声波清洗器中提取30min后，取出待溶液温度冷却至，再加入溶液、溶液及水，然后放置 h进行测定。答：小碎块；聚乙烯塑料；盐酸；室温；氢氧化钠；总离子强度调节缓冲（TISAB）；3～5 4.当测定体系中有、、存在时，产生的干扰可以采用加入总离子强度调节缓冲液来消除。 答：Si4＋；Fe3＋；Al3＋ 5.氟电极是一种传感器，是由或膜构成的。是膜的传导者，只有可以透过膜。 答：离子选择性，氟化镧单晶，掺了铕等的氟化镧单晶，氟离子，氟离子。 二、选择题 1.本方法可测定的氟化物最低限量为。 A、3μg； B、4μg； C、5μg； D、6μg 答：C 2.本方法测定氟化物所需配制试剂均应贮于中。 A、玻璃瓶； B、聚乙烯新塑料瓶； C、玻璃瓶或聚乙烯新塑料瓶； D、任何材质试剂瓶 答：B 三、判断题 1.采样后，样品膜贮存在干燥器中，必须在六星期内完成分析。（） 2.配制标准曲线时，测定从高浓度到低浓度逐个进行。（） 3.本方法测定氟化物，当采样体积为10m3时，最低检出浓度为0.5μg/m3。（）
答：1.√ 2.× 3.√ 四、问答题 1.本方法测定环境空气中氟化物的原理是什么？ 答：己知体积的空气通过磷酸氢二钾浸渍的滤膜时，氟化物被固定或阻留在滤膜上，滤膜上的氟化物用盐酸溶液浸溶后，用氟离子选择电极法测定。 2.怎样制作磷酸氢二钾浸渍滤膜？ 答：将乙酸-硝酸纤维微孔滤膜放入磷酸氢二钾浸渍液中浸湿后，沥干，摊放在大张定性滤纸上，于40℃以下烘干，装入塑料盒中，密封好入干燥器中备用。 3.氟离子选择电极如何存放？ 答：电极用后应用水充分冲洗干净，并用滤纸吸去水分，放在空气中，或者放在稀的氟化物标准溶液中，如果短时间不再使用，应洗净，吸去水分，套上保护电极敏感部位的保护帽，电极使用前应充分冲洗，并去掉水分。 4.在用离子选择电极法测定氟化物时，影响实验的主要因素有哪些？ 答：（1）电极的斜率；（2）电极的稳定性、重现性和寿命；（3）电极的响应时间；（4）待测溶液的浓度；（5）pH值的影响；（6）温度的影响；（7）搅拌的影响。 五、计算题 1.请写出本方法测定氟化物的计算公式及式中符号含义。 答：C（Fμg/m3）= () 00 2 1 V 2W W W- + 式中：C——环境空气中氟化物质量浓度，μg/m3； W 1+W 2 ——两层滤膜样品的氟含量，μg； W ——空白滤膜平均氟含量，μg； V ——标准状态下的采样体积，m3。
国家环境监测网环境空气臭氧自动监测现场核查技术规定 （试行） 1适用范围 本规定规定了开展环境空气臭氧自动监测现场比对的方法和要求。 本规定适用于国家和地方各级环境监测站对辖区内环境空气臭氧自动监测质量进行现场核查。 2规范性引用文件 本规定内容引用了下列文件中的条款，凡是不注明日期的引用文件，其有效版本适用于本规定。 HJ 590 环境空气臭氧的测定紫外光度法 HJ 193-2005 环境空气质量自动监测技术规范 3术语和定义 下列术语和定义适用于本规定。 3.1 臭氧标准参考光度计，Standard Reference Photometer，SRP NIST与EPA于1981年合作开发的标准参考光度计，作为臭氧参考标准。 主要性能指标： 测量范围：0-1000 nmol/mol； 测量不确定度：±1 nmol/mol（0-100 nmol/mol）、±1%（100-1000 nmol/mol）。 3.2 臭氧传递标准 指经过臭氧标准参考光度计（SRP）量值传递（可经过一级或多级传递）后，可用来进行现场环境臭氧分析仪的比对和向现场的环境臭氧分析仪传递准确度的臭氧校准仪。 4方法原理 采用经量值溯源的臭氧传递标准，对正常工作状态的国家网环境空气自动监测子站的臭氧分析仪进行现场比对，以分析仪测定值与传递标准设定值的相对误差评价子站臭氧分析仪的准确度。
5试剂和材料 5.1 采样管线及接头，采样管线采用不与臭氧发生化学反应的聚四氟乙烯材料，接头包括三通、两通等常用接头。 5.2 臭氧传递标准运输箱，减少仪器运输过程中的物理震动、位移等。 6仪器和设备 6.1 臭氧传递标准 可根据比对实施者的实验室条件，选择下列传递标准之一用于现场比对用。 6.1.1 臭氧校准仪 经过臭氧标准参考光度计（SRP）直接校准过的臭氧校准仪。 6.1.2 多种气体校准仪 经过臭氧校准仪校准过的多种气体校准仪。与零气源连接后，能够产生稳定的接近系统上限浓度的臭氧（0.5 μmol/mol或1.0 μmol/mol），能够准确控制进入臭氧发生器的零空气的流量，至少可以对发生的初始臭氧浓度进行4级稀释。 6.2 空气压缩机 可以使用环境空气子站的空气压缩机，也可以使用比对实施者单独携带的空气压缩机，能稳定输出压力为20~30psi的气体。 6.3 零气发生装置 能产生符合分析校准程序要求的零空气。由核查实施者单独携带至现场，用于现场核查时向传递标准和分析仪通入零空气。 注：零空气质量的确认参见HJ 590附录A。 7现场比对 7.1 将臭氧传递标准运输至监测现场，连接好臭氧传递标准与臭氧分析仪之间的电线、气体管路和通讯线路。打开电源，开机预热至少2小时。 7.2打开空气压缩机和零气发生装置，调节压力使其稳定输出20~30psi的零空气。 7.3 在0~500 nmol/mol量程范围内，设置臭氧传递标准产生零点、精密度点（100 nmol/mol）、跨度点（400 nmol/mol）、日常监测浓度点的臭氧，依次通入臭氧分析仪30分钟，仪器自动记录分钟数据。 注：取子站最近一年臭氧小时值的平均值作为日常监测浓度点。
环境空气氟化物的测定滤膜采样氟离子选择电极法HJ480-2009 1适用范围 本标准规定了测定环境空气中氟化物的滤膜采集、氟离子选择电极法。 本标准适用于环境空气中氟化物的小时浓度和日平均浓度的测定。3当采样体积为6m3时，测定下限为 0.9μg/m。 2规范性引用文件 本标准内容引用了下列文件中的条款，凡是不注明日期的引用文件，其最新有效版本适用于本标准。 GB 7484水质氟化物的测定离子选择电极法 HJ/T 194环境空气质量手工监测技术规范 3术语和定义 下列术语和定义适用于本标准。 氟化物： 指空气中存在的气态氟化物及溶于盐酸溶液[c（HCl）= 0.25mol/L]的颗粒态氟化物。 4方法原理 已知体积的空气通过磷酸氢二钾浸渍的滤膜时，氟化物被固定或阻留在滤膜上，滤膜上的氟化物用盐酸溶液浸溶后，用氟离子选择电极法测定。 5试剂和材料
本标准所用试剂除非另有说明，分析时均使用符合国家标准的分析纯化学试剂，实验用水为新制备的去离子水或蒸馏水。 5.1盐酸溶液c（HCl）= 2.5mol/L： 取1000ml水，加入 20.8ml盐酸（优级纯，ρ= 1.18g/ml），搅拌均匀。 5.2氢氧化钠溶液c（NaOH）= 1.0mol/L： 称取 40.0g优级纯氢氧化钠，溶于水，冷却后稀释至1000ml。 5.3氢氧化钠c（NaOH）= 5.0mol/L： 称取 100.0g优级纯氢氧化钠，溶于水，冷却后稀释至500ml。 5.4磷酸氢二钾浸渍液： 称取 76.0g磷酸氢二钾溶于水，移入1000ml容量瓶中，用水定容至标线，摇匀。 5.5总离子强度调节缓冲溶液（TISAB） 5.5.1总离子强度调节缓冲溶液（TISAB Ⅰ）:
空气中臭氧的测定方法主要有靛蓝二磺酸钠分光光度法、紫外光度法和化学发光法。 G.1靛蓝二磺酸的分光光度法 G.1.1 相关标准和依据 本方法主要依据GB/T15437 《环境质量臭氧的测定靛蓝二磺酸的分光光度法》。 G.1.2 原理 空气中的臭氧，在磷酸盐缓冲溶液存在下，与吸收液中蓝色的靛蓝二磺酸钠等摩尔反应，褪色生成靛红二磺酸钠。在610nm处测定吸光度，根据蓝色减褪的程度定量空气中臭氧的浓度。 G.1.3 测定范围 当采样体积为30L时，最低检出浓度为0.01mg/m3。当采样体积为（5～30）L，时，本法测定空气中臭氧的浓度范围为0.030～1.200 mg/m3。 G.1.4 仪器 G.1.4.1 采样导管：用玻璃管或聚四氟乙烯管，内径约为3mm，尽量短些，最长不超过2m，配有朝下的空气入口。 G.1.4.2 多孔玻板吸收管：10mL。 G.1.4.3 空气采样器。 G.1.4.4 分光光度计。 G.1.4.5 恒温水浴或保温瓶。 G.1.4.6 水银温度计：精度为±5℃。 G.1.4.7 双球玻璃管：长10cm，两端内径为6mm，双球直径为15mm。 G.1.5 试剂 除非另有说明，分析时均使用符合国家标准的分析纯试剂和重蒸馏水或同等纯度的水。G.1.5.1 溴酸钾标准贮备溶液C（1/6KBrO3）=0.1000mol/L：称取1.3918g溴酸钾（优级纯，180℃烘2h ）溶解于水，移入500mL容量瓶中，用水稀释至标线。 G.1.5.2 溴酸钾—溴化钾标准溶液C（1/6KBrO3）=0.0100mol/L：吸取10.00mL溴酸钾标准贮备溶液于100mL 容量瓶中，加入1.0g溴化钾（KBr），用水稀释至标线。 G.1.5.3 硫代硫酸钠标准贮备溶液C（Na2S2O3）=0.1000mol/L。 G.1.5.4 硫代硫酸钠标准工作溶液C（Na2S2O3）=0.0050mol/L：临用前，准确量取硫代硫酸钠标准贮备溶液用水稀释20倍。 https://www.doczj.com/doc/4912510496.html, G.1.5.5 硫酸溶液：（1+6）（V/V）。 G.1.5.6 淀粉指示剂溶液，2.0g/L ：称取0.20g可溶性淀粉，用少量水调成糊状，慢慢倒入100mL沸水中，煮沸至溶液澄清。 G.1.5.7 磷酸盐缓冲溶液C（KH2PO4—Na2HPO4）=0.050mol/L：称取6.8g磷酸二氢钾（KH2PO4）和7.1g无水磷酸氢二钠（Na2HPO4），溶解于水，稀释至1000mL。 G.1.5.8 靛蓝二磺酸钠（C6H18O8S2Na2 简称IDS），分析纯。 G.1.5.9 IDS标准贮备溶液：称取0.25g靛蓝二磺酸钠（IDS），溶解于水，移入500mL棕色容量瓶中，用水稀释至标线，摇匀，24h后标定。此溶液于20℃以下暗处存放可稳定两周。标定方法：吸取20.00mL IDS标准贮备溶液于250mL碘量瓶中，加入20.00mL溴酸钾—溴化钾标准溶液，再加入50mL水，盖好瓶塞，放入16℃±1℃水浴或保温瓶中，至溶液温度与水温平衡时， 42 加入5.0mL（1+6）硫酸溶液，立即盖好瓶塞，混匀并开始计时，在16℃±1℃水浴中，于暗处放置35min±1min。加入1.0g碘化钾（KI）立即盖好瓶塞摇匀至完全溶解，在暗处放置5min
For personal use only in study and research; not for commercial use 臭氧浓度检测方法大致可分为“化学分析法”、“物理分析法”、“物理化学分析法”三类。 1.化学检测法 1.化学检测法 1.1 碘量法 碘量法是最常用的臭氧测定方法，我国和许多国家均把此法作为测定气体臭氧的标准方法，我国建设部发布的《臭氧发生器臭氧浓度、产量、电耗的测量》标准CJ/T 3028.2 — 94 中即规定使用碘量法。其原理为强氧化剂臭氧（O 3 ）与碘化钾（KI ）水溶液反应生成游离碘（I 2 ）。臭氧还原为氧气。反应式为：O 3 + 2KI + H 2 O → O 2 + I 2 + 2KOH 游离碘显色，依在水中浓度由低至高呈浅黄至深红色。 利用硫代硫酸钠（NaS 2 O 3 ）标准液滴定，游离碘变为碘化钠（NaI ），反应终点为完全褪色止。反应式为： I 2 + 2Na 2 S 2 O 3 → 2NaI + NaS 4 O 6 两反应式建立起O 3 反应量与NaS 2 O 3 消耗量的定量关系为1molO 3 ：2mol NaS 2 O 3 ，则臭氧浓度 C O3 计算式为： C O3 =40x3x1000/1000 （mg/L ） 式中： C O3 ——臭氧浓度，mg/L ； A Na ——硫代硫酸钠标准液用量，ml ； B ——硫代硫酸钠标准液浓度，mol/L ； V 0 ——臭氧化气体取样体积，ml 。 操作程序及方法参照标准CJ/T3028.2 — 94 。 测定标准型发生器浓度很方便。臭氧化气体积用流量计计数，NaS 2 O 3 浓度一般配制为0.100mol/L ，测定精度可达± 1% 。 测定空气中臭氧浓度时，应用在气采样器抽气定量。为保证测定精度，NaS 2 O 3 配为0.10mol/L 。 测定水溶臭氧浓度亦可用此公式计算，只是V 0 代表采水量，取1000ml 。NaS 2 O 3 浓度为0.10mol/L 。 碘量法优点为显色直观。不需要贵重仪器。缺点是易受其氧化剂如NO 、CI 2 等物质的干扰，在重要检测时应减除其它氧化物质的影响。 1.2 比色法 比色法是根据臭氧与不同化学试剂的显色或脱色反应程度来确定臭氧浓度的方法。按比色手段分为人工色样比色与光度计色 . 此法多用于检测水溶解臭氧浓度 . 国内检测瓶装水臭氧溶解浓度有使用碘化钾、邻联甲胺等比色液的。其方式是利用检测样品显色液管相比较，确定测样臭氧溶解度值（0.05~0.08mg/L ）, 要求精确的，则利用分光光度计检测。 国外利用此法做成仪器，配制标准工具与药品作为现场抽检使用，很方便。如美国HACH 公司、日本荏原公司的DPD （二己基对苯二胺）比色盘，范围为0.05~2mg/L 。美国HACH 公司微型比色仪，利用靛蓝染料脱色反应。在600nm 波长比色，0.05~0.75nm/L 浓度数字显示，精度± 0.01nm/L 。受其它氧化剂干扰少。 1.3 检测管 将臭氧氧化可变化试剂浸渍在载体上，作为反应剂封装在标准内径的玻璃管内做成测管，使用时将检测管两端切断，把抽气器接到检测管出气端吸取定量臭氧气体，臭氧浓度与检测管内反应剂柱变色长度成正比，通过刻度值读取浓度值。 德国、日本和我国都生产臭氧检测管，浓度范围分为高（1000ppm ）、中（10ppm ）、低（3ppm ）
环境空气氟化物采样器满足新国标HJ955-2018《环境空气氟化物的测定滤膜采样/氟离子选择电极法》 1产品概述 TC-120（F）空气氟化物采样器（以下简称采样器）是适用于采集大气中重金属颗粒(TSP)和氟化物样品的必备采样器。该仪器采用传感器、新材料等领域的高新技术，质量可靠、性能稳定、使用寿命长。 2适用范围 采用滤膜称重法捕集环境大气中的重金属颗粒（TSP）以及空气中的氟化物。可供环保、卫生、劳动、安监、军事、科研、教育等部门用于气态物质和气溶胶的常规及应急监测。 3采用标准 HJ955-2018《环境空气氟化物的测定滤膜采样/氟离子选择电极法》 HJ/T374-2007《总悬浮颗粒物采样器技术要求及检测方法》 JJG943-2011《总悬浮颗粒物采样器》 4技术特点 无刷高负压采样泵，50L/min流量下，可以克服20kPa阻力；
电子流量计，恒流采样； 具有实时时钟，可设置定时采样，间隔多次采样； 氟化物采样头采用铝合金材质，抗静电吸附； 自动测量温度、气压，自动计算标况采样体积； 体积小、重量轻，携带方便； 大尺寸中文点阵式液晶屏，自动调节对比度，可在零下30度正常工作； 掉电保护功能，来电自动采样； 可选配TSP/PM10/PM2.5采样头用于空气重金属采样； 5工作原理 5.1氟化物采样 氟化物及重金属采样器是指能够采集空气动力学当量直径<100μm颗粒物的采样器。其基本原理是：使一定体积的空气恒速通过已知质量的滤膜时，悬浮于空气中的颗粒物被阻留在滤膜上，根据滤膜增加的质量和通过滤膜的空气体积，确定空气中总悬浮颗粒物的质量浓度，并可用于测定颗粒物中的金属、无机盐及有机污染物等成分。 6技术参数 表1技术参数 主要参数参数范围分辨率准确度 采样流量(10～100)L/min0.1L/min优于±2.5% 流量稳定性优于±2.0% 流量重复性优于±2.0% 采样时间1min～99h59min1min不超过±0.2% 计前压力(-20～0)kPa0.01kPa优于±2.5% 环境大气压(70～130)kPa0.01kPa优于±2.5% 定时开机24小时制
臭氧浓度测定方法： A.碘量滴定法： A-1测定原理 利用碘化钾与臭氧反应而析出游离碘,，以硫代硫酸钠标准溶液进行滴定，然后计算出臭氧量，其反应式为： O2+2KI+H2O -> I2+2KOH+O2↑ I2+2Na2S2O2 ->2NaI+Na2S4O4 A-2 测定方法 将1%碘化钾（KI）水溶液盛于吸收瓶中，再将吸收瓶连接在由老化试验箱至取样真空泵之间，吸取一定容积的含臭氧空气后，移入滴定瓶中，并加入0.4%体积（为吸收液体积的百分数）的1N硫酸（或10%之乙酸）进行酸化，然后以0.001N的（硫代硫酸钠）标准液滴定，至溶液呈黄色时，加入2滴1%淀粉液指示剂，继续滴定至溶液蓝色刚消失即为终点 A-3 臭氧浓度的计算 据上述化学反应式，在标准状况下，1克当量硫代硫酸钠（Na2S2O2）的臭气体积当量为11.2，故臭氧量U（单位：L）为： U=(11.2/1000)*N*B 通过碘化钾（KI）吸收液的含臭氧空气量V0（单位：L）在标准状态下为： V0=(27.3/760)*((p*V)/T) 由此可得到臭氧浓度（O2）的计算式为： （O2）=U/ V0=3118000*(N*B*T)/(p*V) 式中： （O2）=试验的臭氧浓度，pphm N =硫化硫酸钠标准溶液的当量浓度 B =硫代硫酸钠标准溶液的消耗量，ml T =试验温度，K（273+试验温度o C） P =吸收瓶中的气压（P大气压-P真空度），mmHg柱 V =通过吸收液的含臭氧空气的总量，L B.紫外线吸收法： 原理为臭氧对波长λ=254nm紫外光具有最大吸收系数，在此波长下紫外光通过臭氧层 会产生衰减，符合兰波特-比尔（Lambert--Beer）定律：I=Io-KLC :Io-无臭氧存在时入射 光强度；I-光束穿透臭氧后的光强度；L-臭氧样品池光程长度；C-臭氧浓度；K-臭氧对光 波长吸收系数。 根据该公式，在K、L值已知条件下，通过检测I/Io值即可测出臭氧浓度C值来。 紫外吸收法已被美国等国家作为臭氧分析的标准方法。 可连续在线检测，数字显示并可记录打印。优点为检测精度高，稳定性好，其它氧化剂干 扰小。缺点为价格较高。 标准件追溯至美国，本公司使用之检测仪追溯至美国NIST实验室。
江苏省百斯特检测技术有限公司作业指导书大气固定污染源氟化物的测定 JCZY—102 编制人 校核人 批准人 批准日期
大气固定污染源 氟化物的测定作业指导书 1 引用标准 国家环境保护总局标准 HJ/T67-2001 《固定污染源氟化物的测定 离子选择电极法》 2 适用范围 本方法适用于烟气中氟化物的测定。 本方法检出限：当采样体积为150L 时，为6×10-2mg/m3，测定的范围：1～1000mg/m3。 3 原理 使用滤筒、氢氧化钠溶液采集尘氟及气态氟，加硝酸溶液处理后制备成样品溶液，用氟离子电极测定。氟离子电极在含氟离子的溶液中，当溶液的总离子强度为定值而且足够大时，其电极电位与溶液中氟离子活度的对数成直线关系，通过绘制标准曲线，从测得的电位值得到氟离子的含量。 4 试剂和材料 4.1超细玻璃纤维滤筒或合成纤维滤筒。 4.2吸收液 氢氧化钠溶液C （NaOH ）=0.3mol/L ；将12g 氢氧化钠溶于水,并稀释至1000mL 。 4.3 0.1％溴甲酚绿指示剂 称取100mg 溴甲酚绿于研钵中，加少量（1+4）乙醇，研细，用（1+4）乙醇配成100mL 溶液。 4.4盐酸溶液 C （HCl ）=1.0mol/L:取84.0mL 盐酸用水稀释至1000m 。 4.5盐酸溶液 C （HCl ）=0.25mol/L:取21.0mL 盐酸用水稀释至1000mL 。 4.6氢氧化钠溶液C （NaOH ）=1.0mol/L ：将40g 氢氧化钠溶于水并稀释至1000mL 。 4.7总离子强度缓冲溶液（TISAB ） 称取59.0g 柠檬酸钠（Na3C6H5O7·2H2O ），20.0g 硝酸钾，置于1000mL 烧杯中，加300mL 水溶解，加溴甲酚绿指示剂1.0mL ，用浓盐酸溶液及氢氧化钠溶液调节至溶液刚转变为蓝绿色为止，pH 为 5.5（也可在酸度计上，用酸、碱溶液调节至pH5.5），移入1000mL 容量瓶，用水稀释至标线，摇匀。 4.8氟化钠标准贮备溶液 称取0.2210g 氟化钠（优级纯，经110℃烘干2h ），溶解于水，移入100mL 容量瓶中，用水稀释至标线，摇匀，保存聚乙烯塑料瓶中。此溶液每毫升含1000ug 氟。 4.9氟化钠标准溶液 临用时将氟化钠标准贮备溶液用水稀释成 2.5ug/mL 、 5.0ug/mL 、10.0ug/mL 、25.0ug/mL 、50.0ug/mL 、100.0ug/mL 的氟的标准溶液。 5 实验步骤 5.1采样 当烟气中共存尘氟和气态氟时，采样方法进行等速采样。在加热式滤筒采样管的出口，串联三个装有75mL 吸收液的多孔玻板吸收瓶，分别捕集尘氟和气态氟。 当烟气中不含尘氟或只测定气态氟时，可采用烟气采样方法，在采样管出口串联两个装有50mL 吸收液的多孔玻板吸收瓶，以0.5～2L/min 的流量采样5～20min 。 采样管与吸收瓶之间的连接管，选用聚四氟乙烯管，并应尽量短。 5.2分析 校准曲线的绘制 作业指导书 第 2 页 共 3页 第 0次修改 江苏省百斯特检测技术有限公司 大气固定污染源氟化物的测定
环境空气中臭氧的测定(HJ 504-2009 ) —靛蓝二磺酸钠分光光度法 一、实验目的 1、掌握靛蓝二磺酸钠分光光度法测定环境空气中臭氧含量的原 理和方法； 2、熟练掌握滴定操作； 3、熟练掌握采样仪器和分光光度计的操作。 二、实验前准备 1、试剂 (1)溴酸钾标准贮备 溶液［c(1/6 KBr03)=0.100 0 mol/L］准确称取 1.391 8 g溴化钾(优级纯，180C烘2 h ),置烧杯中，加入少量水溶解，移入 500ml容量瓶中，用水稀释至标线。 (2)溴酸钾-溴化钾标准溶液［c(1/6 KBrO5)= 0.010 0 mol/L］吸取 10.00 ml溴酸钾标准贮备溶液于100 ml容量瓶中，加入1.0g溴化钾(KBr),用 水稀释至标线。 (3)硫代硫酸钠标准贮备溶液［c(Na2S2O3)= 0.1000 mol/L］。 (4)硫代硫酸钠标准工作溶液［c(Na2S2O3)= 0.00500 mol/L］临用前，取硫代硫酸钠标准贮备溶液用新煮沸并冷却到室温的水准确稀释 20 倍。 (5)硫酸溶液，1+6。 (6)淀粉指示剂溶液［p =2.0 g/L］称取0.20g可溶性淀粉，用少量
水调成糊状，慢慢倒入100 ml沸水,煮沸至溶液澄清。 （7）磷酸盐缓冲溶液，［c（KH2PO4-Na2HPO4）=O.O50riol/L］称取 6.8 g 磷酸二氢钾（KH2PO）7.1 g无水磷酸氢二钠（Na2HPC）溶于水，稀释至1000 ml。 （8）靛蓝二磺酸钠（C16H8O8Na2S2（简称IDS），分析纯、化学纯或生化试剂。 （9） IDS标准贮备溶液：称取0.25g靛蓝二磺酸钠溶于水，移入500 ml棕色容量瓶，用水稀释至标线，摇匀，在室温暗处存放 24 h后标定。此溶液在20C以下暗处存放可稳定2周。 标定方法：准确吸取 20.00 ml IDS 标准贮备溶液于250 ml碘量瓶中，加入20.00 ml溴酸钾-溴化钾溶液再加入50 ml水，盖好瓶塞，在16 C 士 1 C生化培养箱（或水浴中放置至溶液温度与水浴温度平衡时［注1］，加入5.0 ml 硫酸溶液，立即盖塞、混匀并开始计时，于16 C 士 1C暗处放置35 min 士1.0 min后，加入1.0 g碘化钾，立即盖塞，轻轻摇匀至溶解，暗处放置 5 min，用硫代硫酸钠溶液滴定至棕色刚好褪去呈淡黄色，加入5 ml淀粉指示剂溶液，继续滴定至蓝色消退，终点为亮黄色。记录所消耗的硫代硫酸钠标准工作溶液的体积［注2］。注1:达到平衡的时间与温差有关，可以预先用相同体积的水代替溶液，加入碘量瓶中，放入温度计观察达到平衡（HJ 504—2009）所需要的时间。 注2:平行滴定所消耗的硫代硫酸钠标准溶液体积不应大0.10 ml。 每毫升靛蓝二磺酸钠溶液相当于臭氧的质量浓度P(血/ml)计算：
公共场所空气中臭氧检验方法 1 原理 空气中的臭氧使吸收液中蓝色的靛蓝二磺酸钠褪色，生成靛红二磺酸钠。根据颜色减弱的程度比色定量。 2 试剂 本法中所用试剂除特别说明外均为分析纯，实验用水为重蒸水。重蒸水的制备方法：在第一次蒸馏水中加高锰酸钾至淡红色，再用氢氧化钡碱化后，进行重蒸馏。 2.1吸收液靛蓝二磺酸钠溶液,量取25ml靛蓝二磺酸钠贮备液,用磷酸盐缓冲液稀释至1L棕色容量瓶中,冰箱内贮放可使用一月。 2.2淀粉指示剂（2.0g/L）临用现配。 2.3硫代硫酸钠标准溶液C（Na 2S 2 O 3 ）=0.1000mol/L。 2.4溴酸钾标准溶液C（1/6KBrO 3 ）=0.1000mol/L，准确称取1.3918g（优级纯，经180烘2h）溶于水，稀释至500ml。 2.5溴酸钾-溴化钾标准溶液C（1//6KBrO 3 ）=0.0100mol/L，吸取10.00ml 0.1000mol/L溴酸钾标准溶液于100ml容量瓶中,加1.0g溴化钾,用水稀释至刻度。 2.6硫酸溶液（1+6）。 2.7磷酸盐缓冲溶液（pH6.8）称6.80g磷酸二氢钾(KH 2PO 4 )、7.10g无水磷酸氢 二钠(Na 2HPO 4 )溶于水，稀释至1L。 2.8靛蓝二磺酸钠（简称IDS）。 2.9靛蓝二磺酸钠贮备液 称取0.25gIDS溶于水，稀释在500ml棕色容量瓶内，在室温暗处存放24h后标定。标定后的溶液冰箱内可稳定一月。 标定方法：准确吸取20.00mlIDS贮备液于250ml碘量瓶中，加入20.00ml溴化钾-溴酸钾溶液，再加入50ml水。在（19.0±0.5）℃水浴中放置至溶液温度与水浴温度平衡时，加入5.0ml硫酸溶液，立即盖塞混匀并开始计时，水浴中暗处放置30min。加入1.0g碘化钾，立即盖塞轻轻摇匀至溶解，暗处放置5min，用硫代硫酸钠溶液滴定至棕色刚好褪去呈淡黄色，加入5ml淀粉指示剂，继续滴定
环境空气检测作业指导书 中铁西北科学研究院有限公司 工程检测试验中心 二〇一五年
目录 一、环境空气氮氧化物的测定 (1) 二、空气质量恶臭的测定 (9) 三、环境空气二氧化硫的测定 (14) 四、环境空气二硫化碳的测定 (22) 五、环境空气一氧化碳的测定 (25) 六、环境空气总悬浮物颗粒的测定 (27) 七、环境空气PM10和PM2.5的测定 (32) 八、硫化氢的测定 (37) 九、环境空气氟化物的测定 (43) 十、环境空气和废气氨的测定纳氏试剂分光光度法 (48) 十一、环境空气氨的测定次氯酸钠-水杨酸分光光度法 (54) 十二、固定污染源废气苯可溶物的测定 (59) 十三、废气铬酸雾的测定 (64) 十四、硫酸雾的测定 (67)
一、环境空气氮氧化物的测定 一、执行标准 环境空气氮氧化物(一氧化氮和二氧化氮)的测定盐酸萘乙二胺分光光度法HJ 479-2009。 二、适用范围 1、本标准适用于环境空气中氮氧化物、二氧化氮、一氧化氮的测定。 2、本标准的方法检出限为0.36μg/10ml 吸收液。当吸收液总体积为10ml，采样体积为24L时，空气中氮氧化物的检出限为0.015mg/m3。当吸收液总体积为 50ml，采样体积288L 时，空气中氮氧化物的检出限为0.006mg/m3，本标准测定环境空气中氮氧化物的测定范围为 0.024 mg/m3~2.0mg/m3。 三、干扰及消除 1、空气中二氧化硫浓度为氮氧化物浓度 30 倍时，对二氧化氮的测定产生负干扰。 2、空气中过氧乙酰硝酸酯（PAN）对二氧化氮的测定产生正干扰。 3、空气中臭氧浓度超过 0.25mg/m3时，对二氧化氮的测定产生负干扰。采样时在采样瓶入口端串接一段(15～20)cm 长的硅橡胶管，可排除干扰。 四、测定原理 空气中的二氧化氮被串联的第一支吸收瓶中的吸收液吸收并反应生成粉红色偶氮染料。空气中的一氧化氮不与吸收液反应，通过氧化管时被酸性高锰酸钾溶液氧化为二氧化氮，被串联的第二支吸收瓶中的吸收液吸收并反应生成粉红色偶氮染料。生成的偶氮染料在波长 540nm 处的吸光度与二氧化氮的含量成正比。分别测定第一支和第二支吸收瓶中样品的吸光度，计算两支吸收瓶内二氧化氮和一氧化氮的质量浓度，二者之和即为氮氧化物的质量浓度（以二氧化氮计）。 五、仪器设备 1、常用的实验室仪器。 2、分光光度计。 3、空气采样器：流量范围 0.1L/min～1.0L/min。采样流量为 0.4L/min 时，
空气中臭氧的检验方法 1原理 空气中的臭氧使吸收液中蓝色的靛蓝二磺酸钠褪色，生成靛红二磺酸钠。根据颜色减弱的程度比色定量。 2试剂 本法中所用试剂除特别说明外均为分析纯，实验用水为重蒸水。重蒸水的制备方法：在第一次蒸馏水中加高锰酸钾至淡红色，再用氢氧化钡碱化后，进行重蒸馏。 2．1吸收液靛蓝二磺酸钠溶液，量取25ml靛蓝二磺酸钠贮备液，用磷酸盐缓冲液稀释至1L 棕色容量瓶中，冰箱内贮放可使用一月。 2．2淀粉指示剂（2．0g/L）临用现配。 2．3硫代硫酸钠标准溶液C（Na2S2O3）＝0．1000mol/L。 2．4溴酸钾标准溶液C（1/6KBrO3）＝0．1000mol/L，准确称取1．3918g（优级纯，经180°烘2h）溶于水，稀释至500mL。 2．5溴酸钾一溴化钾标准溶液C（1/6KBrO3）－0．0100mol/L，吸取10．00ml 0．1000mol/L 溴酸钾标准溶液于100ml容量瓶中，加入1．0g溴化钾，用水稀释至刻度。 2．6硫酸溶液（1＋6）。 2．7磷酸盐缓冲溶液（pH6．8）称6．80g磷酸二氢钾（KH2PO4）、7．10g无水磷酸氢二钠（Na2HPO4）溶于水，稀释至1L。 2．8靛蓝二磺酸钠（简称IDS）。 2．9靛蓝二磺酸钠贮备液 称取0．25gIDS溶于水，稀释在500ml棕色容量瓶内，在室温暗处存放24h后标定。标定后的溶液冰箱内可稳定一月。 标定方法：准确吸取20．00mlIDS贮备液于250ml碘量瓶中，加入20．00ml溴化钾－溴酸钾溶液，再加入50mL水。在（19．0±0．5）℃水浴中放置至溶液温度与水浴温度平衡时，加入5．0ml 硫酸溶液，立即盖塞混匀并开始计时，水浴中暗处放置30min。加入1．0g碘化钾，立即盖塞轻轻摇匀至溶解，暗处放置5min，用硫代硫酸钠溶液滴定至棕色刚好褪去呈淡黄色，加入5ml淀粉指示剂，继续滴定至蓝色消褪，终点为亮黄色。平行滴定所消耗硫代硫酸钠标准溶液体积不应大于0．05ml。靛蓝二磺酸钠溶液相当于臭氧的质量浓度C（μgO3/ml）由下式表示：
中华人民共和国国家环境保护标准 HJ 590-2010 代替 GB/T 15438－1995 环境空气 臭氧的测定 紫外光度法 Ambient air―Determination of ozone ―Ultraviolet photometric method 本电子版为发布稿。请以中国环境科学出版社出版的正式标准文本为准。 2010-10-21发布 2011-01-01实施 环 境 保 护 部 发布
目 次 前言 (Ⅱ) 1适用范围 (1) 2术语和定义 (1) 3方法原理 (1) 4干扰及消除 (2) 5试剂和材料 (2) 6仪器和设备 (2) 7分析步骤 (5) 8结果计算 (6) 9精密度和准确度 (7) 10质量保证与质量控制 (7) 附录A（规范性附录）多点臭氧校准仪的一级校准 (8) 附录B（规范性附录）环境空气中一氧化氮干扰的校正 (10) 附录C（资料性附录）某些化合物对紫外吸收臭氧测定仪的干扰 (11) 附录D（资料性附录）典型的紫外臭氧分析仪性能参数 (12)
前 言 为贯彻《中华人民共和国环境保护法》和《中华人民共和国大气污染防治法》，保护环境，保障人体健康，规范环境空气中臭氧的监测方法，制定本标准。 本标准规定了测定环境空气中臭氧的紫外光度法。 本标准是对《环境空气臭氧的测定紫外分光光度法》（GB/T 15438-1995）的修订。 本标准首次发布于1995年，原标准起草单位为鞍山市环境监测中心站，本次为第一次修订。修订的主要内容有： ──修订了空气中臭氧测定的适用范围及其参考条件。 ──修订了“干扰及其消除”条款。 ──明确规定了公式 ln(I/I0)= -a C d 中各项代表的物理意义。增加了臭氧浓度的计算公式。 ──增加了术语和定义条款。 ──增加了质量保证和质量控制条款。 ──补充完善了检测的技术条件和注意事项。 ──增加了对零空气质量的要求和确认步骤。 ──增加了附录B、附录C和附录D。 本标准的附录A和附录B为规范性附录，附录C和附录D为资料性附录。 自本标准实施之日起，原国家环境保护局1995年3月25日批准、发布的国家环境保护标准《环境空气臭氧的测定紫外分光光度法》(GB/T 15438-1995)废止。 本标准由环境保护部科技标准司组织修订。 本标准主要起草单位：沈阳市环境监测中心站。 本标准环境保护部2010年10月21日批准。 本标准自2011年1月1日起实施。 本标准由环境保护部解释。
大气中氟化氢和氟化物的测定方法 氟化氢为无色有刺激性的气体，分子量20.01；相对密度0.69(对空气)；熔点－83.1℃；沸点19.5℃。氟化氢易溶于水即成氢氟酸，在潮湿空气中形成雾。氟化氢和多种金属作用生成氢气。无水氟化氢及40%氢氟酸在空气中发生烟雾，其蒸气具有强烈的腐蚀性。 气态的氟在空气中除大部分是氟化氢，少量的氟化硅(SiF 4 )外，还可能以氟 化碳(CF 4)存在。含氟粉尘主要是冰晶石(Na 3 AlF 6 )、萤石(CaF 2 )、氟化铝(AlF 3 ) 和氟化钠(NaF)以及各种氟化磷灰石〔3Ca 3(PO 4 ) 2 ·Ca(Cl，F) 2 〕等。氟化物污 染主要来源于铝厂、磷肥厂和冰晶石厂、电解铝、用硫酸处理萤石以及制造氟化物和应用氢氟酸时均污染空气。 氟及其化合物的气体和粉尘属高毒类。主要由呼吸道吸入。氟化氢和氢氟酸的大面积灼伤可引起氟骨病。人在氟化氢400～430mg/m3浓度下可引起急性中毒致死。100mg/m3能耐受1min。50mg/m3感觉皮肤刺痛，粘膜刺激。26mg/m3能耐受数分钟。嗅觉阈为0.03mg/m3。长期吸入低浓度的氟及其化合物的气体和粉尘，能够影响各组织和器官的正常生理功能，如牙酸蚀症、牙龈出血、干燥性鼻炎、鼻衄、嗅觉减退及咽喉炎、慢性支气管炎等，甚至引起慢性氟中毒(氟骨症)。此时尿氟可能增高，但与氟对机体损害的程度无平行关系。空气中的氟化物不但对人体和动物有损害，同样对某些植物的生长也有明显损害，甚至在其浓度很低的情况下(含氟浓度低至2μg/m3)就可使水仙菖属植物叶子受损害。因此，人们利用氟对某些植物的敏感程度可进行环境监测。大气中的氟化物可低至10-9(体积分数)浓度范围；也可以高到10-6(V/V)浓度范围。为此，对这样宽的测量范围就需要几种不同的测定方法，只有在采样和分析方法上选择适当，才能完成测试任务。早期的方法是利用氟离子在锆或钍与茜素生成的络合物上进行反应来测量，但其灵敏度很难适宜于低至 10-9(体积分数)浓度范围。利用氟试剂(3－胺甲基茜素－N，N－二乙酸)以及高价镧或铈盐反应所产生蓝色铬合物进行比色定量，其方法灵敏度虽有所提高，但干扰因素多，测定范围窄，仅适用体系简单的样品，如干扰物过多时，仍需进行灰化、蒸馏等预处理。利用氟离子选择性电极法[2]测F-，具有快速、灵敏、适用范围宽、方法简便、准确、特异性好等优点，它可省去灰化、蒸馏等繁琐处理步骤。目前广泛应用的是离子选择电极法和氟试剂比色法。滤膜采样－离子选择电极法已推荐为我国居住区大气中氟化物卫生检验标准方法(国家标准报批稿)[1]〔1〕。 一、滤膜采样－离子选择电极法[1,2] (一)原理 空气中气态及颗粒态氟化物通过两层串联的滤膜，第一层为加热干燥滤膜，阻留颗粒物质，第二层浸渍氢氧化钠溶液的滤膜，用以采集气态氟。收集在滤膜上的氟化物，溶解在缓冲液中制成样品溶液，以氟离子选择电极测量电位值，其电位与氟离子活度的对数成线性关系。通过一次标准加入法计算样液中的氟离子含量。 (二)仪器 (1)滤料采样夹及采样装置结构见图9－1。