WAC 296-62-07544
Appendix B -- Sampling strategy and
analytical methods for formaldehyde. (1) To protect the
health of employees, exposure measurements must be unbiased
and representative of employee exposure. The proper
measurement of employee exposure requires more than a token
commitment on the part of the employer. WISHA's mandatory
requirements establish a baseline; under the best of
circumstances all questions regarding employee exposure will
be answered. Many employers, however, will wish to conduct
more extensive monitoring before undertaking expensive
commitments, such as engineering controls, to assure that the
modifications are truly necessary. The following sampling
strategy, which was developed at NIOSH by Nelson A. Leidel,
Kenneth A. Busch, and Jeremiah R. Lynch and described in NIOSH
publication No. 77-173 (Occupational Exposure Sampling
Strategy Manual) will assist the employer in developing a
strategy for determining the exposure of his or her employees.
(2) There is no one correct way to determine employee
exposure. Obviously, measuring the exposure of every employee
exposed to formaldehyde will provide the most information on
any given day. Where few employees are exposed, this may be a
practical solution. For most employers, however, use of the
following strategy will give just as much information at less
cost.
(3) Exposure data collected on a single day will not
automatically guarantee the employer that his or her workplace
is always in compliance with the formaldehyde standard. This
does not imply, however, that it is impossible for an employer
to be sure that his or her worksite is in compliance with the
standard. Indeed, a properly designed sampling strategy
showing that all employees are exposed below the PELs, at
least with a ninety-five percent certainty, is compelling
evidence that the exposure limits are being achieved provided
that measurements are conducted using valid sampling strategy
and approved analytical methods.
(4) There are two PELs, the TWA concentration and the
STEL.
(a) Most employers will find that one of these two limits
is more critical in the control of their operations, and WISHA
expects that the employer will concentrate monitoring efforts
on the critical component.
(b) If the more difficult exposure is controlled, this
information, along with calculations to support the
assumptions, should be adequate to show that the other
exposure limit is also being achieved.
(5) Sampling strategy.
(a) Determination of the need for exposure measurements.
(b) The employer must determine whether employees may be
exposed to concentrations in excess of the action level. This
determination becomes the first step in an employee exposure
monitoring program that minimizes employer sampling burdens
while providing adequate employee protection.
(c) If employees may be exposed above the action level,
the employer must measure exposure. Otherwise, an objective
determination that employee exposure is low provides adequate
evidence that exposure potential has been examined.
(d) The employer should examine all available relevant
information, e.g., insurance company and trade association
data and information from suppliers or exposure data collected
from similar operations.
(e) The employer may also use previously-conducted
sampling including area monitoring. The employer must make a
determination relevant to each operation although this need
not be on a separate piece of paper.
(f) If the employer can demonstrate conclusively that no
employee is exposed above the action level or the STEL through
the use of objective data, the employer need proceed no
further on employee exposure monitoring until such time that
conditions have changed and the determination is no longer
valid.
(g) If the employer cannot determine that employee
exposure is less than the action level and the STEL, employee
exposure monitoring will have to be conducted.
(6) Workplace material survey.
(a) The primary purpose of a survey of raw material is to
determine if formaldehyde is being used in the work
environment and if so, the conditions under which formaldehyde
is being used.
(b) The first step is to tabulate all situations where
formaldehyde is used in a manner such that it may be released
into the workplace atmosphere or contaminate the skin. This
information should be available through analysis of company
records and information on the MSDSs available through
provisions of this standard and the hazard communication
standard.
(c) If there is an indication from materials handling
records and accompanying MSDSs that formaldehyde is being used
in the following types of processes or work operations, there
may be a potential for releasing formaldehyde into the
workplace atmosphere:
(i) Any operation that involves grinding, sanding,
sawing, cutting, crushing, screening, sieving, or any other
manipulation of material that generates formaldehyde-bearing
dust.
(ii) Any processes where there have been employee
complaints or symptoms indicative of exposure to formaldehyde.
(iii) Any liquid or spray process involving formaldehyde.
(iv) Any process that uses formaldehyde in preserved
tissue.
(v) Any process that involves the heating of a
formaldehyde-bearing resin.
Processes and work operations that use formaldehyde in
these manners will probably require further investigation at
the worksite to determine the extent of employee monitoring
that should be conducted.
(7) Workplace observations.
(a) To this point, the only intention has been to provide
an indication as to the existence of potentially exposed
employees. With this information, a visit to the workplace is
needed to observe work operations, to identify potential
health hazards, and to determine whether any employees may be
exposed to hazardous concentrations of formaldehyde.
(b) In many circumstances, sources of formaldehyde can be
identified through the sense of smell. However, this method
of detection should be used with caution because of olfactory
fatigue.
(c) Employee location in relation to source of
formaldehyde is important in determining if an employee may be
significantly exposed to formaldehyde. In most instances, the
closer a worker is to the source, the higher the probability
that a significant exposure will occur.
(d) Other characteristics should be considered. Certain
high temperature operations give rise to higher evaporation
rates. Locations of open doors and windows provide natural
ventilation that tend to dilute formaldehyde emissions. General room ventilation also provides a measure of control.
(8) Calculation of potential exposure concentrations.
(a) By knowing the ventilation rate in a workplace and
the quantity of formaldehyde generated, the employer may be
able to determine by calculation if the PELs might be
exceeded.
(b) To account for poor mixing of formaldehyde into the
entire room, locations of fans and proximity of employees to
the work operation, the employer must include a safety factor.
(c) If an employee is relatively close to a source,
particularly if he or she is located downwind, a safety factor
of one hundred may be necessary.
(d) For other situations, a factor of ten may be
acceptable. If the employer can demonstrate through such
calculations that employee exposure does not exceed the action
level or the STEL, the employer may use this information as
objective data to demonstrate compliance with the standard.
(9) Sampling strategy.
(a) Once the employer determines that there is a
possibility of substantial employee exposure to formaldehyde,
the employer is obligated to measure employee exposure.
(b) The next step is selection of a maximum risk
employee. When there are different processes where employees
may be exposed to formaldehyde, a maximum risk employee should
be selected for each work operation.
(c) Selection of the maximum risk employee requires
professional judgment. The best procedure for selecting the
maximum risk employee is to observe employees and select the
person closest to the source of formaldehyde. Employee
mobility may affect this selection; e.g., if the closest
employee is mobile in his tasks, he may not be the maximum
risk employee. Air movement patterns and differences in work
habits will also affect selection of the maximum risk
employee.
(d) When many employees perform essentially the same
task, a maximum risk employee cannot be selected. In this
circumstance, it is necessary to resort to random sampling of
the group of workers. The objective is to select a subgroup
of adequate size so that there is a high probability that the
random sample will contain at least one worker with high
exposure if one exists. The number of persons in the group
influences the number that need to be sampled to ensure that
at least one individual from the highest ten percent exposure
group is contained in the sample. For example, to have ninety
percent confidence in the results, if the group size is ten,
nine should be sampled; for fifty, only eighteen need to be
sampled.
(e) If measurement shows exposure to formaldehyde at or
above the action level or the STEL, the employer needs to
identify all other employees who may be exposed at or above
the action level or STEL and measure or otherwise accurately
characterize the exposure of these employees.
(f) Whether representative monitoring or random sampling
are conducted, the purpose remains the same to determine if
the exposure of any employee is above the action level. If
the exposure of the most exposed employee is less than the
action level and the STEL, regardless of how the employee is
identified, then it is reasonable to assume that measurements
of exposure of the other employees in that operation would be
below the action level and the STEL.
(10) Exposure measurements.
(a) There is no "best" measurement strategy for all
situations. Some elements to consider in developing a
strategy are:
(i) Availability and cost of sampling equipment;
(ii) Availability and cost of analytic facilities;
(iii) Availability and cost of personnel to take samples;
(iv) Location of employees and work operations;
(v) Intraday and interday variations in the process;
(vi) Precision and accuracy of sampling and analytic
methods; and
(vii) Number of samples needed.
(b) Samples taken for determining compliance with the
STEL differ from those that measure the TWA concentration in
important ways. STEL samples are best taken in a nonrandom
fashion using all available knowledge relating to the area,
the individual, and the process to obtain samples during
periods of maximum expected concentrations. At least three
measurements on a shift are generally needed to spot gross
errors or mistakes; however, only the highest value represents
the STEL.
(c) If an operation remains constant throughout the
workshift, a much greater number of samples would need to be
taken over the thirty-two discrete nonoverlapping periods in
an 8-hour workshift to verify compliance with a STEL. If
employee exposure is truly uniform throughout the workshift,
however, an employer in compliance with the 1 ppm TWA would be
in compliance with the 2 ppm STEL, and this determination can
probably be made using objective data.
(11) Need to repeat the monitoring strategy.
(a) Interday and intraday fluctuations in employee
exposure are mostly influenced by the physical processes that
generate formaldehyde and the work habits of the employee. Hence, in-plant process variations influence the employer's
determination of whether or not additional controls need to be
imposed. Measurements that employee exposure is low on a day
that is not representative of worst conditions may not provide
sufficient information to determine whether or not additional
engineering controls should be installed to achieve the PELs.
(b) The person responsible for conducting sampling must
be aware of systematic changes which will negate the validity
of the sampling results. Systematic changes in formaldehyde
exposure concentration for an employee can occur due to:
(i) The employee changing patterns of movement in the
workplace;
(ii) Closing of plant doors and windows;
(iii) Changes in ventilation from season to season;
(iv) Decreases in ventilation efficiency or abrupt
failure of engineering control equipment; and
(v) Changes in the production process or work habits of
the employee.
(c) Any of these changes, if they may result in
additional exposure that reaches the next level of action
(i.e., 0.5 or 1.0 ppm as an 8-hour average or 2 ppm over
fifteen minutes) require the employer to perform additional
monitoring to reassess employee exposure.
(d) A number of methods are suitable for measuring
employee exposure to formaldehyde or for characterizing
emissions within the worksite. The preamble to this standard
describes some methods that have been widely used or subjected
to validation testing. A detailed analytical procedure
derived from the WISHA Method A.C.R.O. for acrolein and
formaldehyde is presented below for informational purposes.
(e) Inclusion of WISHA's method in this appendix in no
way implies that it is the only acceptable way to measure
employee exposure to formaldehyde. Other methods that are
free from significant interferences and that can determine
formaldehyde at the permissible exposure limits within ± 25
percent of the "true" value at the ninety-five percent
confidence level are also acceptable. Where applicable, the
method should also be capable of measuring formaldehyde at the
action level to ± 35 percent of the "true" value with a
ninety-five percent confidence level. WISHA encourages
employers to choose methods that will be best for their
individual needs. The employer must exercise caution,
however, in choosing an appropriate method since some
techniques suffer from interferences that are likely to be
present in workplaces of certain industry sectors where
formaldehyde is used.
(12) WISHA's analytical laboratory method.
A.C.R.O. (also use methods F.O.R.M. and F.O.R.M. 2 when
applicable).
(a) Matrix: Air.
(b) Target concentration: 1 ppm (1.2 mg/m3).
(c) Procedures: Air samples are collected by drawing
known volumes of air through sampling tubes containing XAD-2
adsorbent which have been coated with 2-(hydroxymethyl)
piperidine. The samples are desorbed with toluene and then
analyzed by gas chromatography using a nitrogen selective
detector.
(d) Recommended sampling rate and air volumes: 0.1 L/min
and 24 L.
(f) Standard error of estimate at the target
concentration: 7.3%.
(g) Status of the method: A sampling and analytical
method that has been subjected to the established evaluation
procedures of the organic methods evaluation branch.
(h) Date: March, 1985.
(13) General discussion.
(a) Background: The current WISHA method for collecting
acrolein vapor recommends the use of activated 13X molecular
sieves. The samples must be stored in an ice bath during and
after sampling and also they must be analyzed within
forty-eight hours of collection. The current WISHA method for
collecting formaldehyde vapor recommends the use of bubblers
containing ten percent methanol in water as the trapping
solution.
(b) This work was undertaken to resolve the sample
stability problems associated with acrolein and also to
eliminate the need to use bubblers to sample formaldehyde. A
goal of this work was to develop and/or to evaluate a common
sampling and analytical procedure for acrolein and
formaldehyde.
(c) NIOSH has developed independent methodologies for
acrolein and formaldehyde which recommend the use of
reagent-coated adsorbent tubes to collect the aldehydes as
stable derivatives. The formaldehyde sampling tubes contain
Chromosorb 102 adsorbent coated with N-benzylethanolamine
(BEA) which reacts with formaldehyde vapor to form a stable
oxazolidine compound. The acrolein sampling tubes contain
XAD-2 adsorbent coated with 2-(hydroxymethyl) piperidine
(2-HMP) which reacts with acrolein vapor to form a different,
stable oxazolidine derivative. Acrolein does not appear to
react with BEA to give a suitable reaction product. Therefore, the formaldehyde procedure cannot provide a common
method for both aldehydes. However, formaldehyde does react
with 2-HMP to form a very suitable reaction product. It is
the quantitative reaction of acrolein and formaldehyde with
2-HMP that provides the basis for this evaluation.
(d) This sampling and analytical procedure is very
similar to the method recommended by NIOSH for acrolein. Some
changes in the NIOSH methodology were necessary to permit the
simultaneous determination of both aldehydes and also to
accommodate WISHA laboratory equipment and analytical
techniques.
(14) Limit-defining parameters: The analyte air
concentrations reported in this method are based on the
recommended air volume for each analyte collected separately
and a desorption volume of 1 mL. The amounts are presented as
acrolein and/or formaldehyde, even though the derivatives are
the actual species analyzed.
(15) Detection limits of the analytical procedure: The
detection limit of the analytical procedure was 386 pg per
injection for formaldehyde. This was the amount of analyte
which gave a peak whose height was about five times the height
of the peak given by the residual formaldehyde derivative in a
typical blank front section of the recommended sampling tube.
(16) Detection limits of the overall procedure: The
detection limits of the overall procedure were 482 ng per
sample (16 ppb or 20 ug/m3 for formaldehyde). This was the
amount of analyte spiked on the sampling device which allowed
recoveries approximately equal to the detection limit of the
analytical procedure.
(17) Reliable quantitation limits:
(a) The reliable quantitation limit was 482 ng per sample
(16 ppb or 20 ug/m3) for formaldehyde. These were the
smallest amounts of analyte which could be quantitated within
the limits of a recovery of at least seventy-five percent and
a precision (± 1.96 SD) of ± 25% or better.
(b) The reliable quantitation limit and detection limits
reported in the method are based upon optimization of the
instrument for the smallest possible amount of analyte. When
the target concentration of an analyte is exceptionally higher
than these limits, they may not be attainable at the routine
operating parameters.
(18) Sensitivity: The sensitivity of the analytical
procedure over concentration ranges representing 0.4 to 2
times the target concentration, based on the recommended air
volumes, was seven thousand five hundred eighty-nine area
units per ug/mL for formaldehyde. This value was determined
from the slope of the calibration curve. The sensitivity may
vary with the particular instrument used in the analysis.
(19) Recovery: The recovery of formaldehyde from samples
used in an eighteen-day storage test remained above ninety-two
percent when the samples were stored at ambient temperature. These values were determined from regression lines which were
calculated from the storage data. The recovery of the analyte
from the collection device must be at least seventy-five
percent following storage.
(20) Precision (analytical method only): The pooled
coefficient of variation obtained from replicate
determinations of analytical standards over the range of 0.4
to 2 times the target concentration was 0.0052 for
formaldehyde ((d)(C)(iii) of this subsection).
(21) Precision (overall procedure): The precision at the
ninety-five percent confidence level for the ambient
temperature storage tests was ±14.3% for formaldehyde. These
values each include an additional ±5% for sampling error. The
overall procedure must provide results at the target
concentrations that are ±25% at the ninety-five percent
confidence level.
(22) Reproducibility: Samples collected from controlled
test atmospheres and a draft copy of this procedure were given
to a chemist unassociated with this evaluation. The
formaldehyde samples were analyzed following fifteen days
storage. The average recovery was 96.3% and the standard
deviation was 1.7%.
(23) Advantages:
(a) The sampling and analytical procedures permit the
simultaneous determination of acrolein and formaldehyde.
(b) Samples are stable following storage at ambient
temperature for at least eighteen days.
(24) Disadvantages: None.
(25) Sampling procedure.
(a) Apparatus:
(i) Samples are collected by use of a personal sampling
pump that can be calibrated to within ±5% of the recommended
0.1 L/min sampling rate with the sampling tube in line.
(ii) Samples are collected with laboratory prepared
sampling tubes. The sampling tube is constructed of silane
treated glass and is about 8-cm long. The ID is 4 mm and the
OD is 6 mm. One end of the tube is tapered so that a glass
wool end plug will hold the contents of the tube in place
during sampling. The other end of the sampling tube is open
to its full 4-mm ID to facilitate packing of the tube. Both
ends of the tube are fire-polished for safety. The tube is
packed with a 75-mg backup section, located nearest the
tapered end and a 150-mg sampling section of pretreated XAD-2
adsorbent which has been coated with 2-HMP. The two sections
of coated adsorbent are separated and retained with small
plugs of silanized glass wool. Following packing, the
sampling tubes are sealed with two 7/32 inch OD plastic and
caps. Instructions for the pretreatment and the coating of
XAD-2 adsorbent are presented in (d) of this subsection.
(b) Sampling tubes, similar to those recommended in this
method, are marketed by Supelco, Inc. These tubes were not
available when this work was initiated; therefore, they were
not evaluated.
(26) Reagents: None required.
(27) Technique:
(a) Properly label the sampling tube before sampling and
then remove the plastic end caps.
(b) Attach the sampling tube to the pump using a section
of flexible plastic tubing such that the large, front section
of the sampling tube is exposed directly to the atmosphere. Do not place any tubing ahead of the sampling tube. The
sampling tube should be attached in the worker's breathing
zone in a vertical manner such that it does not impede work
performance.
(c) After sampling for the appropriate time, remove the
sampling tube from the pump and then seal the tube with
plastic end caps.
(d) Include at least one blank for each sampling set. The blank should be handled in the same manner as the samples
with the exception that air is not drawn through it.
(e) List any potential interferences on the sample data
sheet.
(28) Breakthrough:
(a) Breakthrough was defined as the relative amount of
analyte found on a backup sample in relation to the total
amount of analyte collected on the sampling train.
(b) For formaldehyde collected from test atmospheres
containing six times the PEL, the average five percent
breakthrough air volume was 41 L. The sampling rate was 0.1
L/min and the average mass of formaldehyde collected was 250
ug.
(29) Desorption efficiency: No desorption efficiency
corrections are necessary to compute air sample results
because analytical standards are prepared using coated
adsorbent. Desorption efficiencies were determined, however,
to investigate the recoveries of the analytes from the
sampling device. The average recovery over the range of 0.4
to 2 times the target concentration, based on the recommended
air volumes, was 96.2% for formaldehyde. Desorption
efficiencies were essentially constant over the ranges
studied.
(30) Recommended air volume and sampling rate:
(a) The recommended air volume for formaldehyde is 24 L.
(b) The recommended sampling rate is 0.1 L/min.
(31) Interferences:
(a) Any collected substance that is capable of reacting
with 2-HMP and thereby depleting the derivatizing agent is a
potential interference. Chemicals which contain a carbonyl
group, such as acetone, may be capable of reacting with 2-HMP.
(b) There are no other known interferences to the
sampling method.
(32) Safety precautions:
(a) Attach the sampling equipment to the worker in such a
manner that it will not interfere with work performance or
safety.
(b) Follow all safety practices that apply to the work
area being sampled.
(33) Analytical procedure.
(a) Apparatus:
(i) A gas chromatograph (GC), equipped with a nitrogen
selective detector. A Hewlett-Packard model 5840A GC fitted
with a nitrogen phosphorus flame ionization detector (NPD) was
used for this evaluation. Injections were performed using a
Hewlett-Packard model 7671A automatic sampler.
(ii) A GC column capable of resolving the analytes from
any interference. A 6 ft x 1/4 in OD (2mm ID) glass GC column
containing 10% UCON 50-HB-5100+ 2% KOH on 80/100 mesh
Chromosorb W-AW was used for the evaluation. Injections were
performed on-column.
(iii) Vials, glass 2-mL with Teflon-lined caps.
(iv) Volumetric flasks, pipets, and syringes for
preparing standards, making dilutions, and performing
injections.
(b) Reagents:
(i) Toluene and dimethylformamide. Burdick and Jackson
solvents were used in this evaluation.
(ii) Helium, hydrogen, and air, GC grade.
(iii) Formaldehyde, thirty-seven percent by weight, in
water. Aldrich Chemical, ACS Reagent Grade formaldehyde was
used in this evaluation.
(iv) Amberlite XAD-2 adsorbent coated with
2-(hydroxymethyl) piperidine (2-HMP), 10% by weight ((d) of
this subsection).
(v) Desorbing solution with internal standard. This
solution was prepared by adding 20 uL of dimethylformamide to
100 mL of toluene.
(c) Standard preparation:
(i) Formaldehyde: Prepare stock standards by diluting
known volumes of thirty-seven percent formaldehyde solution
with methanol. A procedure to determine the formaldehyde
content of these standards is presented in (d) of this
subsection. A standard containing 7.7 mg/mL formaldehyde was
prepared by diluting 1 mL of the thirty-seven percent reagent
to 50 mL with methanol.
(ii) It is recommended that analytical standards be
prepared about sixteen hours before the air samples are to be
analyzed in order to ensure the complete reaction of the
analytes with 2-HMP. However, rate studies have shown the
reaction to be greater than ninety-five percent complete after
four hours. Therefore, one or two standards can be analyzed
after this reduced time if sample results are outside the
concentration range of the prepared standards.
(iii) Place 150-mg portions of coated XAD-2 adsorbent,
from the same lot number as used to collect the air samples,
into each of several glass 2-mL vials. Seal each vial with a
Teflon-lined cap.
(iv) Prepare fresh analytical standards each day by
injecting appropriate amounts of the diluted analyte directly
onto 150-mg portions of coated adsorbent. It is permissible
to inject both acrolein and formaldehyde on the same adsorbent
portion. Allow the standards to stand at room temperature. A
standard, approximately the target levels, was prepared by
injecting 11 uL of the acrolein and 12 uL of the formaldehyde
stock standards onto a single coated XAD-2 adsorbent portion.
(v) Prepare a sufficient number of standards to generate
the calibration curves. Analytical standard concentrations
should bracket sample concentrations. Thus, if samples are
not in the concentration range of the prepared standards,
additional standards must be prepared to determine detector
response.
(vi) Desorb the standards in the same manner as the
samples following the sixteen-hour reaction time.
(d) Sample preparation:
(i) Transfer the 150-mg section of the sampling tube to a
2-mL vial. Place the 75-mg section in a separate vial. If
the glass wool plugs contain a significant number of adsorbent
beads, place them with the appropriate sampling tube section. Discard the glass wool plugs if they do not contain a
significant number of adsorbent beads.
(ii) Add 1 mL of desorbing solution to each vial.
(iii) Seal the vials with Teflon-lined caps and then
allow them to desorb for one hour. Shake the vials by hand
with vigorous force several times during the desorption time.
(iv) Save the used sampling tubes to be cleaned and
recycled.
(e) Analysis:
(f) GC conditions.
(34) Column temperature:
(a) Bi-level temperature program.
(i) First level: 100°C to 140°C at 4°C/min following
completion of the first level.
(ii) Second level: 140°C to 180°C at 20°C/min following
completion of the first level.
(b) Isothermal period: Hold column at 180°C until the
recorder pen returns to baseline (usually about twenty-five
minutes after injection).
(c) Injector temperature: 180°C.
(d) Helium flow rate: 30 mL/min (detector response will
be reduced if nitrogen is substituted for helium carrier gas).
(e) Injection volume: 51 0.8 uL.
(f) GC column: Six-ft x 1/4-in OD (2 mm ID) glass GC
column containing 10% UCON 50-HB-5100NZG651+512% KOH on 80/100
Chromosorb W-AW.
(g) NPD conditions:
(i) Hydrogen flow rate: 3 mL/min.
(ii) Air flow rate: 50 mL/min.
(h) Detector temperature: 275 5151C.
(i) Use a suitable method, such as electronic
integration, to measure detector response.
(ii) Use an internal standard method to prepare the
calibration curve with several standard solutions of different
concentrations. Prepare the calibration curve daily. Program
the integrator to report results in ug/mL.
(iii) Bracket sample concentrations with standards.
(iv) Interferences (analytical).
(A) Any compound with the same general retention time as
the analytes and which also gives a detector response is a
potential interference. Possible interferences should be
reported to the laboratory with submitted samples by the
industrial hygienist.
(B) GC parameters (temperature, column, etc.), may be
changed to circumvent interferences.
(C) A useful means of structure designation is GC/MS. It
is recommended this procedure be used to confirm samples
whenever possible.
(D) The coated adsorbent usually contains a very small
amount of residual formaldehyde derivative.
(i) Calculations:
(i) Results are obtained by use of calibration curves. Calibration curves are prepared by plotting detector response
against concentration for each standard. The best line
through the data points is determined by curve fitting.
(ii) The concentration, in ug/mL, for a particular sample
is determined by comparing its detector response to the
calibration curve. If either of the analytes is found on the
backup section, it is added to the amount found on the front
section. Blank corrections should be performed before adding
the results together.
(iii) The acrolein and/or formaldehyde air concentration
can be expressed using the following equation:
Mg/m3=(A)(B)/C.
where A=ug/mL from 3.7.2, B=desorption volume, and C=L of
air sampled.
No desorption efficiency corrections are required.
(iv) The following equation can be used to convert
results in mg/m51351 to ppm.
ppm=(mg/m3)(24.45)/MW
where mg/m3=result from 3.7.3, 24.45=molar volume of an
ideal gas at 760 mm Hg and 25 5151C, MW=molecular weight
(Formaldehyde=30.0).
(j) Backup data. Backup data on detection limits,
reliable quantitation limits, sensitivity and precision of the
analytical method, breakthrough, desorption efficiency,
storage, reproducibility, and generation of test atmospheres
are available in OSHA Method 52, developed by the Organics
Methods Evaluation Branch, OSHA Analytical Laboratory, Salt
Lake City, Utah.
(k) Procedure to coat XAD-2 adsorbent with 2-HMP:
(i) Apparatus: Soxhlet extraction apparatus, rotary
evaporation apparatus, vacuum dessicator, 1-L vacuum flask,
1-L round-bottomed evaporative flask, 1-L Erlenmeyer flask,
250-mL Buchner funnel with a coarse fritted disc, etc.
(ii) Reagents:
(A) Methanol, isooctane, and toluene.
(B) (Hydroxymethyl) piperidine.
(C) Amberlite XAD-2 nonionic polymeric adsorbent, twenty
to sixty mesh, Aldrich Chemical XAD-2 was used in this
evaluation.
(l) Procedure: Weigh 125 g of crude XAD-2 adsorbent into
a 1-L Erlenmeyer flask. Add about 200 mL of water to the
flask and then swirl the mixture to wash the adsorbent. Discard any adsorbent that floats to the top of the water and
then filter the mixture using a fritted Buchner funnel. Air
dry the adsorbent for two minutes. Transfer the adsorbent
back to the Erlenmeyer flask and then add about 200 mL of
methanol to the flask. Swirl and then filter the mixture as
before. Transfer the washed adsorbent back to the Erlenmeyer
flask and then add about 200 mL of methanol to the flask. Swirl and then filter the mixture as before. Transfer the
washed adsorbent to a 1-L round-bottomed evaporative flask,
add 13 g of 2-HMP and then 200 mL of methanol, swirl the
mixture and then allow it to stand for one hour. Remove the
methanol at about 40°C and reduced pressure using a rotary
evaporation apparatus. Transfer the coated adsorbent to a
suitable container and store it in a vacuum desiccator at room
temperature overnight. Transfer the coated adsorbent to a
Soxhlet extractor and then extract the material with toluene
for about twenty-four hours. Discard the contaminated
toluene, add methanol in its place and then continue the
Soxhlet extraction for an additional four hours. Transfer the
adsorbent to a weighted 1-L round-bottom evaporative flask and
remove the methanol using the rotary evaporation apparatus. Determine the weight of the adsorbent and then add an amount
of 2-HMP, which is ten percent by weight of the adsorbent. Add 200 mL of methanol and then swirl the mixture. Allow the
mixture to stand for one hour. Remove the methanol by rotary
evaporation. Transfer the coated adsorbent to a suitable
container and store it in a vacuum dessicator until all traces
of solvents are gone. Typically, this will take two to three
days. The coated adsorbent should be protected from
contamination. XAD-2 adsorbent treated in this manner will
probably not contain residual acrolein derivative. However,
this adsorbent will often contain residual formaldehyde
derivative levels of about 0.1 ug per 150 mg of adsorbent. If
the blank values for a batch of coated adsorbent are too high,
then the batch should be returned to the Soxhlet extractor,
extracted with toluene again and then recoated. This process
can be repeated until the desired blank levels are attained.
The coated adsorbent is now ready to be packed into
sampling tubes. The sampling tubes should be stored in a
sealed container to prevent contamination. Sampling tubes
should be stored in the dark at room temperature. The
sampling tubes should be segregated by coated adsorbent lot
number. A sufficient amount of each lot number of coated
adsorbent should be retained to prepare analytical standards
for use with air samples from that lot number.
(m) A procedure to determine formaldehyde by acid
titration:
(i) Standardize the 0.1 N HC1 solution using sodium
carbonate and methyl orange indicator.
(ii) Place 50 mL of 0.1 M sodium sulfite and three drops
of thymophthalein indicator into a 250-mL Erlenmeyer flask. Titrate the contents of the flask to a colorless endpoint with
0.1 N HC1 (usually one or two drops is sufficient). Transfer
10 mL of the formaldehyde/methanol solution ((b)(iii)(A) of
this subsection) into the same flask and titrate the mixture
with 0.1 N HC1, again, to a colorless endpoint. The
formaldehyde concentration of the standard may be calculated
by the following equation:
Formaldehyde, mg/mL =
acid titer x acid normality x 30.0
mL of Sample
(iii) This method is based on the quantitative liberation
of sodium hydroxide when formaldehyde reacts with sodium
sulfite to form the formaldehyde-bisulfite addition product. The volume of sample may be varied depending on the
formaldehyde content but the solution to be titrated must
contain excess sodium sulfite. Formaldehyde solutions
containing substantial amounts of acid or base must be
neutralized before analysis.