1. General Discussion
1.1 Background
1.1.1 History
The current NIOSH method (Ref. 5.1) for monitoring airborne acetic anhydride
specifies collection with a midget bubbler containing alkaline hydroxylamine and
analysis by spectrophotometry. The bubbler is cumbersome and spectrophotometry
is nonspecific. Airborne acetic anhydride has also been collected on Porapak N
solid sorbent and analyzed by GC/FID (Ref. 5.2). However, the samples can not
be stored for more than 10 days without significant degradation, even with
freezing. A more convenient sampling method using glass beads coated with 1-2PP
has been reported (Ref. 5.3). The derivative, 1-acetyl-4-(2-pyridyl)piperazine
(AcPP), was analyzed by high performance thin layer chromatography. The
derivatization stabilizes the analyte and eliminates the interference from
acetic acid. It is recognized that ketene and acetyl chloride will also react
with 1-2PP to form AcPP, but neither chemical is used widely in industry (Ref.
5.4).
In this method, a glass fiber filter (GFF) impregnated with 1-2PP was selected
as the sampling medium and the derivative (AcPP) was analyzed by GC/NPD.
Analysis by HPLC/UV is also possible, but not as sensitive as GC/NPD. A flow
rate of 0.05 L/min was selected because capacity of the sampler was reduced at
higher flow rates. Samples are collected closed-face to minimize contamination.
The problem of the analyte concentrating in the center of the filter is
minimized by the use of an extra spacer in the cassette.
1.1.2 Toxic effects (This section is for information only and should not be
taken as the basis of OSHA policy.) (Ref. 5.5 and 5.6)
Acetic anhydride vapors may be irritating to the eyes, nose and throat.
Inhalation of vapors may cause severe irritation of the respiratory system. Due
to its irritating effects, a ceiling value of 5 ppm (20 mg/m3) is set for OSHA
PEL. Contact with the skin or eyes may cause burns. Ingestion may cause severe
burns of the mouth, throat, and stomach. Ingestion may also cause nausea and
vomiting.
1.1.3 Workplace exposure
Exposure to acetic anhydride may occur in the following operations: manufacture
of cellulose esters, fibers, plastics, lacquers, protective coating solutions,
photographic films, cigarette filters, magnetic tape, and thermoplastic molding
compositions; manufacture of pharmaceuticals and pharmaceutical intermediates;
use in organic synthesis as an acetylating agent, bleaching agent, and
dehydrating agent; synthesis of perfume chemicals, explosives, and weed killers;
use in acetylation of animal and vegetables oils; use as an acetylating agent
and dehydrating agent in textile dyeing, chemical treatment of paper, and
chemical analysis. (Ref. 5.7) Of these, by far the greatest single application
for acetic anhydride is in the manufacture of cellulose esters. It is estimated
that 95% of the total U.S. production is used for this purpose. (Ref. 5.8)
1.1.4 Physical properties and other descriptive information (Ref. 5.9. unless
noted otherwise)
chemical name: |
acetic anhydride |
CAS no.: |
108-24-7 |
synonyms: |
acetic acid, anhydride; acetic oxide; acetyl anhydride; acetyl ether; acetyl
oxide; ethanoic anhydrate |
formula: |
(CH3CO)2O |
mol wt: |
102.10 |
boiling point: |
139°C |
melting point: |
-73°C |
vapor pressure: |
0.67 kPa (5 mmHg) at 25°C (Ref. 5.10) |
flash point: |
49°C (closed cup) |
specific gravity: |
1.080 |
color: |
colorless |
odor: |
strong acetic odor |
|
|
Derivative: |
(Ref. 5.11.) |
chemical name: |
1-acetyl-4-(2-pyridyl)piperazine |
structural formula: |
Figure 1.1.4 |
mol wt: |
205.27 |
melting point: |
89.5-91.5°C |
solubility: |
soluble in methanol, acetonitrile, toluene, isopropanol, methylene chloride |
mass spectrum: |
Figure 1.1.4 |
The analyte air concentrations throughout this method are based on the
recommended sampling and analytical parameters. Air concentrations listed in ppm
are referenced to 25°C and 101 kPa (760 mmHg). The analyte concentrations are
listed as those of acetic anhydride even though the derivative is the actual
species analyzed.
1.2 Limit defining parameters
1.2.1 Detection limit of the analytical procedure
The detection limit of the analytical procedure is 11 pg on column (1.0 µL
injection of 0.076 µg/mL solution with 7:1 split). This is the amount of analyte
which gave a peak with height about 5 times the baseline noise. (Section 4.1)
1.2.2 Detection limit of the overall procedure
The detection limit of the overall procedure is 0.51 µg per sample (0.16 ppm,
0.68 mg/m3). This is the amount of analyte spiked on the sampling device which
allows recovery of an amount equivalent to the detection limit of the analytical
procedure. (Section 4.2)
1.2.3 Reliable quantitation limit
The reliable quantitation limit is 0.51 µg per sample (0.16 ppm, 0.68 mg/m3).
This is the smallest amount of analyte spiked on the sampling device which can
be quantitated within the requirements of a recovery of at least 75% and a
precision (±1.96 SD) of ±25% or better. (Section 4.3)
The reliable quantitation limit and detection limits reported in the method are
based upon optimization of the instrument for the smallest possible amount of
the analyte. When the target concentration of the analyte is exceptionally
higher than these limits, they may not be attainable at the routine operating
parameters.
1.2.4 Instrument response to the analyte
The instrument response over the concentration range of 0.5 to 2 times the
target concentration is linear. (Section 4.4)
1.2.5 Recovery
The recovery of AcPP from samples used in a 15-day storage test remained above
83% when the samples were stored at ambient temperature. (Section 4.5) The
recovery of an analyte from the collection medium during storage must be 75% or
greater.
1.2.6 Precision (analytical procedure only)
Nine analytical standards were prepared from three stock standards (individually
prepared) by making serial dilutions to represent 0.5, 1, and 2 times the target
concentration.
The pooled coefficient of variation obtained from duplicate injections of the
nine analytical standards is 0.034. (Section 4.6)
1.2.7 Precision (overall procedure)
The precision at the 95% confidence level for the ambient 15-day storage test is
±14.7%. (Section 4.7) This includes an additional ±5% for pump error. The
overall procedure must provide results at the target concentration that are ±25%
or better at the 95% confidence level.
1.2.8 Reproducibility
A draft copy of this procedure and six samples collected from a controlled test
atmosphere at the target concentration [80% RH, 23°C, 87.7 kPa (658 mmHg)] were
given to a chemist unassociated with this evaluation. The samples were stored in
a refrigerator at 0°C for 1 day before being analyzed. No individual sample
result deviated from its theoretical value by more than the precision reported
in Section 1.2.7. (Section 4.8)
1.3 Advantage
The acetic anhydride is derivatized in situ, eliminating the possibility of its
being hydrolyzed during storage.
1.4 Disadvantage
The method is subject to interference from ketene and acetyl chloride.
2. Sampling Procedure
2.1 Apparatus
2.1.1 A personal sampling pump that can be calibrated to within ±5% of the
recommended flow rate with the sampling device in line.
2.1.2 A four-piece polystyrene cassette containing two glass fiber filters each
impregnated with 2.5 mg of 1-2PP. Impregnated filters are prepared by applying
0.5 mL of a solution of 5.0 mg/mL 1-2PP in methylene chloride to each glass
fiber filter and allowing them to dry in a hood. Impregnated filters should be
stored in a closed jar at reduced temperature before assembly.
2.1.3 Assemble the cassette by placing the extra spacer in front of the first
filter. (Figure 2.3.1)
2.2 Reagents
No reagent is required for sampling.
2.3 Sampling technique
2.3.1 Remove the plugs from the top and bottom pieces. Attach the sampler to
the sampling pump with a piece of flexible tubing and place it in the worker's
breathing zone.
2.3.2 Replace the small plugs after sampling. Seal the sample end-to-end with
an official OSHA seal (Form 21).
2.3.3. Submit at least one blank with each set of samples. Handle the blank the
same as the other samples except draw no air through it.
2.3.4 List any potential interferences on the sample data sheet.
2.4 Sampler capacity
The sampler capacity was evaluated with a test atmosphere (80% RH) at 1.7 times
the target concentration. Two samplers were placed in series. The upstream
sampler contained only the front filter. The back sampler was replaced with a
new sampler every 20 min to monitor the downstream air concentration. The 5%
breakthrough point, defined as the point where the downstream analyte
concentration is 5% of the upstream concentration, was reached at 180 min of
sampling at the recommended sampling rate. (Section 4.9)
2.5 Extraction efficiency and stability of extracted samples (Section 4.10)
2.5.1 The average extraction efficiency at the target concentration was 97.7%.
2.5.2 Extracted samples remain stable for at least 24 h when stored at room
temperature.
2.6 Recommended air volume and sampling rate
2.6.1 The recommended air volume is 0.75 L.
2.6.2 The recommended air sampling rate is 0.05 L/min.
2.7 Interferences (sampling)
Compounds that can react with 1-2PP, such as isocyanates, acid chlorides, and
other anhydrides, may interfere by consuming part of the derivatizing agent.
Acetyl chloride and ketene cause positive interferences.
2.8 Safety precautions (sampling)
Attach the sampling equipment to the worker in such a manner that it will not
interfere with work performance or safety. Follow all safety practices
applicable to the work area.
3. Analytical Procedure
3.1 Apparatus
3.1.1 A GC equipped with a nitrogen-phosphorus detector (NPD). A
Hewlett-Packard 5890 GC equipped with an NPD and a 7673A autosampler was used in
this evaluation.
3.1.2 A GC column capable of separating AcPP, benzalazine, and any
interferences. A 15 m SPB-5 (0.32-mm i.d., 1-µm film) column was used in this
evaluation.
3.1.3 An electronic integrator or other suitable means of measuring detector
response. A Hewlett-Packard 3357 laboratory data system was used in this
evaluation.
3.1.4 Scintillation vials, 20 mL.
3.1.5 Volumetric flasks and pipets.
3.2 Reagents
3.2.1 Acetic anhydride. Acetic anhydride, ACS reagent grade, was obtained from
Aldrich Chemical.
3.2.2 1-(2-Pyridyl)piperazine. 1-(2-Pyridyl)piperazine, 98%, was obtained from
Aldrich Chemical.
3.2.3 1-Acetyl-4-(2-pyridyl)piperazine (AcPP). Synthesized as in Section 4.12.
3.2.4 Benzalazine. Benzalazine from K & K was used in this evaluation.
3.2.5 Toluene. Toluene was obtained from American Burdick and Jackson.
3.2.6 2-Propanol. 2-Propanol, Optima, from Fisher was used.
3.2.7 Extraction solvent with internal standard. Dissolve 10 mg of benzalazine
in 1 L of toluene/2-propanol (50:50).
3.3 Standard preparation
3.3.1 Prepare stock standards by weighing 10-20 mg of AcPP (prepared as in
Section 4.12.) in 10-mL volumetric flasks and diluting to volume with the
extraction solvent. Apply a factor of 0.4973 to the weight of AcPP to convert it
to that of free acetic anhydride. For example, 10 mg of AcPP dissolved in 10 mL
will give a standard stock solution representing 0.4973 mg/mL or 497.3 µg/mL of
acetic anhydride.
(MW acetic anhydride) /( MW AcPP) = 102.09/205.27 = 0.4973
3.3.2 Prepare analytical standards by further diluting the stock standards with
the extraction solvent. An analytical standard of 3.0 µg/mL represents 1 times
the target concentration.
3.3.3 Prepare a sufficient number of standards to generate calibration curves.
Analytical standard concentrations must bracket sample concentrations.
3.4 Sample preparation
3.4.1 Transfer the front and the back filters into separate 20-mL scintillation
vials.
3.4.2 Add 5.0 mL of the extraction solvent to each vial.
3.4.3 Cap the vials and shake them on a mechanical shaker for 1 h.
3.5 Analysis
3.5.1 GC conditions
column: |
SPB-5 (15 m, 0.32-mm i.d., 1-µm film) |
zone temperatures: |
column - |
170°C to 250°C at 10°C/min |
|
injector - |
200°C |
|
detector - |
250°C |
gas flows (mL/min): |
hydrogen (carrier) - |
3.0 |
|
nitrogen - |
27 |
|
air - |
95 |
|
hydrogen - |
3.8 |
injection volume: |
1 µL (with a 7:1 split) |
|
retention times (min): |
1-2PP - |
1.73 |
|
benzalazine - |
4.27 |
|
AcPP - |
4.64 |
chromatogram: |
Figure 3.5.1 |
|
3.5.2 Measure detector response using a suitable method such as electronic
integration.
3.5.3 Construct a calibration curve using an internal standard method by
plotting µg/mL versus ISTD-corrected response of standard injections. Bracket
the samples with analytical standards.
3.6 Interferences (analytical)
3.6.1 Any compound that responds on an NPD and has a similar retention time as
benzalazine or AcPP is a potential interference. Generally, chromatographic
conditions can be altered to separate an interference.
3.6.2 Ketene and acetyl chloride, being able to react with 1-2PP to form AcPP,
are interferences.
3.6.3 Retention time on a single column is not considered proof of chemical
identity. Analyte identity should be confirmed by GC/mass spectrometry if
possible. The mass spectrum of AcPP is shown in Figure 1.1.4.
3.7 Calculations
The analyte concentration for samples is obtained from the calibration curve in
terms of micrograms per milliliter uncorrected for extraction efficiency. The
concentrations are converted to µg per sample by multiplying with 5.0 mL
(extraction volume). The back filter is analyzed primarily to determine if there
was any breakthrough from the front filter during sampling. If a significant
amount of analyte is found on the back filter (e.g., greater than 25% of the
amount found on the front filter), this fact should be reported with sample
results. If any analyte is found on the back filter, it is added to the amount
found on the front filter. This total analyte amount is corrected by subtracting
the amount found in the blank. The air concentration is obtained by using the
following formula.
mg/m3 = |
(micrograms of analyte per sample) (liters of air sampled) (extraction efficiency) |
where extraction efficiency = 0.977
ppm = |
(mg/m3) (24.46) (102.09) |
where: |
24.46 =
molar volume (liters) at 101 kPa (760 mmHg) and 25°C
102.09 =
molecular weight of acetic anhydride |
3.8 Safety precautions (analytical)
Avoid skin contact and inhalation of all chemicals. Restrict the use of all
chemicals to a fume hood when possible. Wear safety glasses and a lab coat at
all times while in the lab area.
4 Backup Data
4.1 Detection limit of the analytical procedure
The detection limit of the analytical procedure is 11 pg on column (1.0 µL
injection of 0.076 µg/mL solution with 7:1 split). This is the amount of analyte
that will give a peak with height approximately 5 times the height of the
baseline noise. A chromatogram of the detection limit of the analytical
procedure is shown in Figure 4.1.
4.2 Detection limit of the overall procedure
The detection limit of the overall procedure is 0.51 µg per sample (0.16 ppm,
0.68 mg/m3). This is the amount of analyte spiked on the sampling device which
allows recovery of an amount equivalent to the detection limit of the analytical
procedure. Six 1-2PP-impregnated glass fiber filters were each liquid spiked
with 0.51 µg of acetic anhydride (6 µL of 85.5 µg/mL solution). The samples were
extracted 24 h later with 5.0 mL of the extraction solvent. The injection size
listed in the analytical procedure (1 µL) was used in the determination of the
detection limit of the overall procedure.
Table 4.2
Detection Limit of the Overall Procedure |
|
sample
number |
theoretical amount
(µg) |
amount recovered
(µg) |
|
1
2
3
4
5
6 |
0.513
0.513
0.513
0.513
0.513
0.513 |
0.577
0.535
0.578
0.546
0.587
0.500 |
|
4.3 Reliable quantitation limit
The reliable quantitation limit is also 0.51 µg per sample (0.16 ppm, 0.68
mg/m3). This was derived from the samples and data of Table 4.2. Because the
recovery was greater than 75% and the precision (1.96 SD) was less than 25%, the
detection limit of the overall procedure and reliable quantitation limit are the
same.
Table 4.3
Reliable Quantitation Limit
(based on samples and data of Table 4.2)
|
% recovery |
statistics |
|
112.5 |
|
104.3 |
= |
108.0% |
112.7 |
SD = |
6.5% |
106.4 |
Precision = |
±(1.96)(6.5%) |
114.4 |
= |
±12.7% |
97.5 |
|
|
4.4 Instrument response
The instrument response (ISTD corrected) to AcPP over the range of 0.5 to 2
times the target concentration is linear with a slope of 1.055. The responses to
AcPP were determined by duplicate injections of nine analytical standards
prepared from three stock standards (individually prepared). Because the
concentrations of these standards were slightly different, the ratios of
response to µg/mL were compared. The data are summarized in Table 4.4. and
presented graphically in Figure 4.4.
Table 4.4
ISTD-corrected Instrument Response to AcPP
|
0.5× target
µg/mL
response
ratio1 |
1× target
µg/mL
response
ratio |
2× target
µg/mL
response
ratio |
|
1.552
1.552
1.452
1.452
1.432
1.432 |
1.295
1.269
1.260
1.192
1.134
1.131 |
0.8344
0.8177
0.8678
0.8209
0.7919
0.7898 |
3.103
3.103
2.904
2.904
2.865
2.865 |
2.835
2.811
2.669
2.651
2.446
2.464 |
0.9136
0.9059
0.9191
0.9129
0.8538
0.8600 |
6.207
6.207
5.809
5.809
5.729
5.729 |
6.363
6.207
5.846
5.863
5.485
5.377 |
1.0251
1.0000
1.0064
1.0093
0.9574
0.9386 |
|
1ratio nbsp;= response / (µg/mL) |
|
|
|
|
|
4.5 Storage data
Thirty-six samples were generated by sampling a test atmosphere (one times the
target concentration, 80% RH) at 0.05 L/min for 15 min. Six samples were
analyzed immediately after the generation. Fifteen samples were stored in a
refrigerator (0°C) and the other fifteen were stored in the dark at ambient
temperature (20-25°C). Every few days over a 15-day period, three samples were
selected from each of the two sets and analyzed. The results are listed Table
4.5. and presented graphically in Figures 4.5.1 and 4.5.2.
Table 4.5
Storage Test
|
storage time
(days) |
% recovery
(ambient) |
% recovery
(refrigerated) |
|
0
0
5
11
12
14
15 |
102.6
94.6
103.6
93.9
80.9
85.6
72.7 |
95.5
102.6
98.6
88.6
85.7
88.4
76.7 |
103.2
101.6
93.9
98.4
83.2
88.2
90.8 |
102.6
94.6
118.0
98.0
83.8
89.6
89.7 |
95.5
102.6
98.9
102.6
85.0
89.6
84.9 |
103.2
101.6
90.4
101.1
102.3
90.3
92.5 |
|
4.6 Precision (analytical method only)
The precision of the analytical procedure is 0.034. The precision of the
analytical procedure is defined as the pooled coefficient of variation
determined from duplicate injections of nine analytical standards representing
0.5, 1, and 2 times the target concentration (Section 4.4).
Table 4.6
Precision of the Analytical Method
(based on the data of Table 4.4.)
|
× target conc. |
0.5× |
1× |
2× |
|
mean |
0.8204 |
0.8942 |
0.9895 |
SD |
0.0290 |
0.0293 |
0.0337 |
CV
|
0.0353
|
0.0328
|
0.0341
|
CV
|
= 0.034 |
|
|
|
|
4.7 Precision (overall procedure)
The precision of the overall procedure is determined from the storage data. The
determination of the standard error of estimate (SEE) for a regression line
plotted through the graphed storage data allows the inclusion of storage time as
one of the factors affecting overall precision. The SEE is similar to the
standard deviation except it is a measure of dispersion of data about a
regression line instead of about a mean. It is determined with the following
equation:
SEE = |
[ |
S
(Yobs - Yest)2
n-k |
] |
1/2
|
where
n =
total no. of data points
k =
2 for linear regression
k =
3 for quadratic regression
Yobs =
observed % recovery at a given time
Yest =
estimated % recovery form the regression line at the same given time
An additional ±5% for pump error is added to the SEE by the addition of
variances. The precision at the 95% confidence level is obtained by multiplying
the SEE (with pump error included) by 1.96 (the z-statistic from the standard
normal distribution at the 95% confidence level). The 95% confidence intervals
are drawn about their respective regression lines in the storage graphs as shown
in Figure 4.5.2. The data for Figure 4.5.2. was used to determine the SEE of
±7.51% and the precision of the overall procedure at the 95% confidence level of
14.7%.
4.8 Reproducibility data
Six samples, collected from a controlled test atmosphere [80% RH, 20-25°C, 87.7
kPa (658 mmHg)] at the target concentration, were given to a chemist
unassociated with this evaluation. The samples were stored for 1 day at about
0°C before being analyzed. The results are presented in Table 4.8. No sample
result had a percent deviation greater than the precision of the overall
procedure, which was ±14.7%.
Table 4.8
Reproducibility Data
|
sample no. |
µg found |
µg expected |
% found |
% deviation |
|
1
2
3
4
5
6 |
12.41
12.07
12.04
11.30
11.81
12.22 |
11.24
11.10
11.27
11.32
11.43
11.17 |
110.4
108.7
106.8
99.8
103.3
109.4 |
+10.4
+8.7
+6.8
-0.2
+3.3
+9.4 |
|
4.9 Sampler capacity
Sampler capacity was tested by sampling a test atmosphere of 33.4 mg/m3 acetic
anhydride at ambient temperature and 80% relative humidity. Two samplers, each
containing only the front filter, were placed in series and the back sampler was
replaced with a new one every 20 minutes to monitor the downstream air
concentration. The sampling rate was 0.0507 L/min. The data are presented in Figure 4.9. The 5% breakthrough point, defined as the point where the downstream analyte concentration reaches 5% of the upstream concentration, was 180 min.
Table 4.9
Breakthrough Data at 1.7 × Target Concentration
|
time1
(min) |
breakthrough
(%) |
time1
(min) |
breakthrough
(%) |
|
10
30
50
70
90
110
130
150 |
1.0
3.1
1.0
0.6
1.4
1.1
0.8
2.1 |
170
190
210
230
250
270
290
|
4.6
6.3
8.0
10.4
13.3
15.2
18.7
|
|
1midpoint of each sampling period
4.10 Extraction efficiency and stability of extracted samples
4.10.1 Extraction efficiency
The extraction efficiency for AcPP was determined by liquid-spiking
1-2PP-impregnated GFF's with acetic anhydride at the target concentration (15.75
µg). These samples were stored at ambient temperature overnight and then
extracted and analyzed. The average extraction efficiency was 97.7%.
Table 4.10.1
Extraction Efficiency
|
sample no. |
µg spiked |
µg recovered |
% recovered |
|
1
2
3
4
5
6
|
15.75
15.75
15.75
15.75
15.75
15.75
|
15.42
15.42
15.59
14.61
15.46
15.79
|
97.9
97.9
99.0
92.8
98.2
100.3
97.7 |
|
4.10.2 Stability of extracted samples
The stability of extracted samples was investigated by reanalyzing the extracted
samples with fresh standards about 24 h after the original analysis. The samples
had been recapped and stored at room temperature. The average of the reanalyzed
samples relative to the average of the original analysis was 99.8%.
Table 4.10.2
Stability of Extracted Samples
|
original
result (%) |
reanalyzed
result (%) |
reanlalyzed relative
to original (%) |
|
97.9
97.9
99.0
92.8
98.2
100.3 |
97.3
100.5
100.0
91.4
100.6
94.9 |
99.4
102.6
101.0
98.5
102.4
94.6 |
|
4.11 Chromatograms
A chromatogram at the detection limit of the analytical procedure is shown in
Figure 4.1 and a chromatogram at the target concentration is shown in Figure 3.5.1.
4.12 Synthesis of AcPP
4.12.1 Reagents
1-(2-Pyridyl)piperazine, 98%, from Aldrich
Acetic anhydride, reagent grade, from Aldrich
Toluene, from American Burdick and Jackson
Isooctane, Optima, from Fisher Scientific
Anhydrous sodium carbonate, reagent, from Mallinckrodt
Activated charcoal, from SKC
4.12.2 Apparatus
Erlenmeyer flasks
Filtering flask
Fritted-glass filtering funnel
4.12.3 Procedure
Add a solution of 1.63 g of 1-2PP in 25 mL of toluene to a solution of 1.02 g
acetic anhydride in 25 mL of toluene. Stir the mixture for 10 min. Add 2 g of
sodium carbonate (to remove the by-product acetic acid) and let stand at room
temperature overnight. Filter the solution and decolorize with activated
charcoal if desired. Evaporate the toluene to about 25 mL. Slowly add isooctane
until the solution turns cloudy. Add a few drops of toluene to make the solution
clear again. Remove from the hot plate and let stand at room temperature.
Collect the resulting crystals by filtration. Recrystallize from
toluene/isooctane; m.p. 89.5-91.5°C; quantitative yield.
Figure 1.1.4 Molecular structure and mass spectrum of
1-acetyl-4-(2-pyridyl)piperazine. The mass spectrum was obtained with a Perkin-Elmer ion trap detector. |
Figure 2.3.1 A drawing of a sample cassette. |
Figure 3.5.1 Chromatogram at target concentration. 1 = benzalazine, 2 AcPP. |
Figure 4.1 Detection limit of the analytical procedure. 1 = benzalazine, 2 =
AcPP. |
Figure 4.4 Calibration curve for AcPP. |
Figure 4.5.1 Storage test at reduced temperature. |
Figure 4.5.2 Storage test at ambient temperature. |
Figure 4.9 Breakthrough curve for acetic anhydride. |
5. References
5.1 Method No. 3506 in "NIOSH Manual of Analytical Methods," 3rd edition, 1985
Supplement, U.S. Department of Health and Human Services, Center for Disease
Control, NIOSH; Cincinnati, OH, 1986.
5.2 Qazi, A.H. and Vincent, W.J., "Sampling and Analysis of Acetic Anhydride in
Air," Am. Ind. Hyg. Assoc. J., 40(9): 803-808 (1979).
5.3 Langhorst, M.L., "Monitoring Airborne Reactive Chemicals by Derivatization
and High Performance Thin Layer Chromatography - Anhydrides, Acid Halides,
Isocyanates," Am. Ind. Hyg. Assoc. J., 46(5): 236-243 (1985).
5.4 Standen, A., Ed., "Kirk-Othmer Encyclopedia of Chemical Technology," 3rd
edition, Volume 1, p. 163. Interscience Publishers, New York, N.Y., 1984.
5.5 J.T. Baker Material Safety Data Sheets (MSDS).
5.6 "Air Contaminants - Permissible Exposure Limits," Code of Federal
Regulations, Title 29; 1910.1000, U.S. Department of Labor, OSHA; Washington,
D.C., 1989, DOL (OSHA) Publ. No. OSHA 3112.
5.7 "NIOSH/OSHA Occupational Health Guidelines for Chemical Hazards," U.S.
Department of Health and Human Services, Government Printing Office, DHHS(NIOSH)
Publication No. 81-123.
5.8 Reference 5.4. Volume 1, p. 158.
5.9 Sweet, D.V., Ed., "Registry of Toxic Effects of Chemical Substances,"
1985-86 edition, U.S. Department of Health and Human Services, Government
Printing Office, DHHS(NIOSH) Publication No. 87-114.
5.10 Weast, R.C., Ed., "Handbook of Chemistry and Physics," 67th edition, Boca
Raton, Florida, CRC Press, 1986.
5.11 Author's personal observations.
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