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n-Amyl Acetate
Isoamyl Acetate
[126 KB PDF,
13 pages]
Related Information: Chemical Sampling -
n-Amyl Acetate,
Isoamyl Acetate
|
Method no.: |
PV2142 |
|
|
Control no.: |
T-PV2142-01-0502-CH |
|
|
Target Concentration:
OSHA PEL:
ACGIH TLV: |
100 ppm (525 mg/m3) (n-amyl acetate)
100 ppm (525 mg/m3) (isoamyl acetate)
100 ppm (525 mg/m3) (n-amyl acetate)
100 ppm (525 mg/m3) (isoamyl acetate)
50 ppm (TWA) 100 ppm (STEL) (all isomers of pentyl acetate) |
|
|
Procedure: |
Samples are collected by drawing workplace
air through glass sampling tubes containing coconut shell charcoal with
personal sampling pumps. Samples are extracted with a mixture of 99:1 carbon
disulfide:N,N-dimethylformamide and analyzed by GC using a flame ionization
detector (GC/FID). |
|
|
Recommended sampling time and sampling rate: |
240 min at 0.1 L/min (24 L) |
|
|
Reliable quantitation limit: |
10 ppb (55 µg/m3) n-amyl acetate
15 ppb (80µg/m3) isoamyl acetate |
|
|
Status of method: |
Partially validated method. This method has
been subjected to established evaluation procedures of the Methods
Development Team and is presented for information and trial use. |
|
|
February 2005 |
Mary Eide |
|
|
Chromatography Team
Industrial Hygiene Chemistry Division
OSHA Salt Lake Technical Center
Sandy UT 84070-6406
|
1. General Discussion
1.1 Background
1.1.1 History
Air samples collected using coconut shell charcoal tubes were received at OSHA
SLTC with requested analysis for n-amyl acetate and isoamyl acetate. These two
compounds are isomers and often occur together in the same workplace, under the
name of amyl acetate. The samples were analyzed following NIOSH methods S45
isoamyl acetate1 and S51 n-amyl acetate.2 There were concerns from OSHA industrial
hygienists that they could smell n-amyl acetate and isoamyl acetate in the
workplace, and yet the results reported from SLTC were below the PEL. The NIOSH
methods did not include humid air retention studies or storage stability
studies. This work was performed to determine if there was a problem with
retention on charcoal sampling tubes and/or with storage. After the storage and
retention studies were completed, NIOSH published a revised method that included
the additional studies, Method 1450 Esters 1.3 The breakthrough study using dry
air was 34.3 L (871 mg/m3 atmosphere) for n-amyl acetate and 32.3 L (874 mg/m3
atmosphere) for isoamyl acetate. The storage study was performed with a loading
of 140 µg on dry tubes with storage at 4 °C. Most workplaces have some humidity
in the air, and water may affect the collection and storage, so it was decided
to complete the work for this method. The retention and storage studies showed
good recoveries, so the low results on field samples versus the expectation of
high results were due to the strong odor of these compounds. The odor is of
bananas or pears, and the odor threshold is 0.051 ppm for n-amyl acetate and
0.0034 ppm for isoamyl acetate.
A special thanks to Gene Brownson who did most of the analyses on the tests
performed in this evaluation.
1.1.2 Toxic effects (This section is for information only and should not be taken as the basis of OSHA policy.)
n-Amyl acetate and isoamyl acetate are moderately toxic by intraperitoneal
administration and are contact irritants affecting the skin, eyes, and
respiratory system. Skin contact may cause dermatitis, higher exposure causes
necrosis.4,5 Eye contact with high concentrations may cause temporary impairment
of vision and/or transient eye inflammation and ulceration. Inhalation of high
concentrations can cause lung irritation, coughing, nausea, central nervous
depression resulting in headache and dizziness, slowing of reflexes, fatigue and
lack of coordination. Liver and kidney damage may result from massive exposures.6,7 Isoamyl acetate has been approved by
FDA for use as a food additive providing "they are used in the minimum quantity
required to produce their intended effect."8
1.1.3 Workplace exposure9,10
n-Amyl acetate and isoamyl acetate are used in cements and glues, paper
coatings, lacquers and paints, leather finishes, flavoring, perfume, nail
enamels, plastic wood, textile sizing and finishes, printing compounds, and
photographic film. They are used in extraction of penicillin, as a warning odor,
as a solvent for nitrocellulose and ethyl cellulose, and as a solvent for
phosphors in fluorescent lamps.
1.1.4 Physical properties and other descriptive information
n-amyl acetate11,12
|
|
CAS number: |
628-63-7 |
synonyms: |
acetic acid, amyl ester; amyl acetic ester;
birnenoel; pear oil; pent-acetate; 1-pentanol acetate; pentyl acetate; n-pentyl
acetate; 1-pentyl acetate; primary amyl acetate |
IMIS13: |
0190 |
RTECS: |
AJ1925000 |
molecular weight: |
130.19 |
density (g/mL): |
0.879 20/20 °C |
melting point: |
-71 °C |
boiling point: |
148 °C |
appearance: |
clear liquid |
flash point: |
25 °C (77 °F) (closed cup) |
odor: |
pear- or banana-like |
molecular formula: |
C7H14O2 |
solubility: |
very slightly soluble in water, miscible in
alcohol and ether |
autoignition temperature: |
379 °C (714 °F) |
lower explosive limit: |
1.1% |
upper explosive limit: |
7.5% |
structural formula: |
|
isoamyl acetate14,15
|
|
CAS number: |
123-92-2 |
synonyms: |
acetic acid, isoamyl ester; acetic acid,
isopentyl ester; banana oil; isoamyl acetate; iso-amylacetate; isoamyl
alcohol, acetate; isopentyl acetate; isopentyl alcohol,
acetate;3-methyl-1-butanol acetate; 3-methylbutyl acetate; 3-methyl
1-butylacetate; 3-methylbutyl ethanoate; pear oil; pent-acetate |
IMIS:16 |
1530 |
RTECS: |
NS9800000 |
molecular weight: |
130.19 |
density (g/mL): |
0.870 20/20 °C |
melting point: |
-71 °C |
boiling point: |
142 °C |
lower explosive
limit: |
1.0%17 |
upper explosive
limit: |
7.5%18 |
appearance: |
clear liquid |
flash point: |
33 °C (92 °F) (closed cup); 38
°C (100 °F) (open cup); |
odor: |
banana- or pear like |
molecular formula: |
C7H14O2 |
solubility: |
slightly soluble in water (400
parts in water), miscible with alcohol, ether, ethyl acetate, amyl alcohol, |
structural
formula: |
|
This method was evaluated according to the OSHA SLTC
"Evaluation Guidelines for Air Sampling Methods Utilizing Chromatographic
Analysis"19. The Guidelines define analytical parameters, specify required
laboratory tests, statistical calculations and acceptance criteria. The
analyte air concentrations throughout this method are based on the
recommended sampling and analytical parameters. Air concentrations in ppm
are referenced to 25 °C and 101.3 kPa (760 mmHg).
1.2 Detection limit of the overall procedure (DLOP) and reliable quantitation limit (RQL)
The DLOP is measured as mass per sample and expressed as equivalent air
concentration, based on the recommended sampling parameters. Ten samplers were
spiked with equal descending increments of analyte, such that the highest
sampler loading was 9.64 µg of n-amyl acetate and 9.57 µg of isoamyl acetate.
This is the amount spiked on a sampler that would produce a peak at least 10
times the response for a sample blank. These spiked samplers were analyzed with
the recommended analytical parameters, and the data obtained used to calculate
the required parameters [standard error of estimate (SEE) and slope] for the
calculation of the DLOP. The slope was 700 and the SEE was 93.0 for n-amyl
acetate. The slope was 776 and the SEE was 149.5 for isoamyl acetate. The DLOP
was 0.40 µg for n-amyl acetate, and 0.57 µg for isoamyl acetate.
Table 1.2.1
Detection Limit of the Overall Procedure for
n-Amyl Acetate
|
mass per sample
(µg) |
area counts
(µV-s) |
|
0.00 |
0 |
0.96 |
715 |
1.93 |
1446 |
2.89 |
2260 |
3.85 |
2962 |
4.82 |
3505 |
5.78 |
4180 |
6.75 |
4788 |
7.71 |
5428 |
8.67 |
6086 |
9.64 |
6902 |
|
|
|
Figure 1.2.1 Plot of data to determine the DLOP/RQL of n-amyl acetate. (y
= 700x + 106) |
|
Table 1.2.2
Detection Limit of the Overall Procedure for
Isoamyl Acetate
|
mass per sample
(µg) |
area counts
(µV-s) |
|
0.00 |
0 |
0.96 |
810 |
1.91 |
1517 |
2.87 |
2446 |
3.83 |
3064 |
4.79 |
3636 |
5.74 |
4343 |
6.70 |
5001 |
7.66 |
5894 |
8.61 |
6723 |
9.57 |
7713 |
|
|
|
Figure 1.2.2 Plot of data to determine the DLOP/RQL of isoamyl acetate. (y
= 776x + 25.6) |
|
The RQL is considered the lower limit for precise quantitative measurements. It is determined from the
regression line parameters obtained for the calculation of the DLOP, providing 75% to 125% of the analyte is recovered. The RQL was 1.33
µg/sample (10 ppb, 55 µg/m3) for n-amyl acetate and 1.91 µg/sample (15 ppb, 80
µg/m3) for isoamyl acetate. Recovery at this
concentration was 99.6% for n-amyl acetate, and 100.5% for isoamyl acetate at this level. |
|
Figure 1.2.2
Chromatogram of the analytes at levels near the RQL amounts. [Key: (1)
isoamyl acetate, (2) interferant, and (3) n amyl acetate] |
2. Sampling Procedure
All safety practices that apply to the work area being sampled should be
followed. The sampling equipment should be attached to the worker in such a
manner that it will not interfere with work performance or safety.
2.1 Apparatus
Samples are collected using a personal sampling pump calibrated, with the
sampling device attached, to within ±5% of the recommended flow rate.
Samples are collected with 7-cm × 4-mm i.d. × 7-mm o.d. glass sampling tubes
packed with two sections (100/50 mg) of coconut shell charcoal. The sections
are held in place with foam plugs and with a glass wool plug at the front. For
this evaluation, commercially prepared sampling tubes were purchased from SKC,
Inc. (Catalog no. 226-01, lot 2000).
2.2 Reagents
None required
2.3 Technique
Immediately before sampling, break off the ends of the flame-sealed tube to
provide an opening approximately half the internal diameter of the tube. Wear
eye protection when breaking the tube. Use tube holders to minimize the hazard
of broken glass. All tubes should be from the same lot.
The smaller section of the adsorbent tube is used as a back-up and is
positioned nearest the sampling pump. Attach the tube holder to the sampling
pump so that the adsorbent tube is in an approximately vertical position with
the inlet facing down during sampling. Position the sampling pump, tube holder
and tubing so they do not impede work performance or safety.
Draw the air to be sampled directly into the inlet of the tube holder. The air
being sampled is not to be passed through any hose or tubing before entering
the sampling tube.
After sampling for the appropriate time, remove the adsorbent tube and seal it
with plastic end caps. Seal each sample end-to-end with an OSHA-21 form as soon
as possible.
Submit at least one blank sample with each set of samples. Handle the blank
sample in the same manner as the other samples except draw no air through it.
Record sample air volumes (liters), sampling time (minutes), and sampling rate
(L/min) for each sample, along with any potential interferences on the OSHA-91A
form.
Submit the samples to the laboratory for analysis as soon as possible after
sampling. If delay is unavoidable, store the samples at refrigerator
temperature. Ship any bulk samples separate from the air samples.
2.4 Extraction efficiency
The extraction efficiency was determined by liquid-spiking charcoal tubes with
the analyte at 0.1 to 2 times the target concentration. These samples were
stored overnight at ambient temperature, then extracted for 30 minutes using a
lab shaker, and analyzed. The mean extraction efficiency over the studied range
was 99.5% for n-amyl acetate and 99.4% for isoamyl acetate. An additional test
was performed with wet sampling medium by drawing 24 L of humid air (80%
relative humidity at 23°C) through sampling tubes before they were spiked at
1.0 times the target concentration. These samples were also stored overnight at
ambient temperature before analysis. The mean recovery from wet sampling medium
was 98.9% for n-amyl acetate and 99.0% for isoamyl acetate.
Table 2.4.1
Extraction Efficiency (%) of n-Amyl Acetate
|
level
|
sampler number
|
mean
|
x target
concn |
mg per
sample |
1 |
2 |
3 |
4 |
|
|
0.1 |
1.28 |
99.1 |
100.1 |
98.7 |
99.5 |
99.4 |
0.5 |
6.37 |
99.5 |
98.8 |
99.5 |
100.2 |
99.5 |
1.0 |
12.8 |
98.9 |
99.7 |
100.2 |
99.9 |
99.7 |
2.0 |
25.5 |
99.2 |
99.8 |
100.3 |
98.5 |
99.5 |
|
|
|
|
|
|
|
1.0 (wet) |
12.8 |
99.1 |
99.6 |
98.7 |
98.2 |
98.9 |
|
Table 2.4.2
Extraction Efficiency (%) of Isoamyl Acetate
|
level
|
sampler number
|
mean
|
x target
concn |
mg per
sample |
1 |
2 |
3 |
4 |
|
|
0.1 |
1.26 |
99.4 |
98.7 |
100.1 |
99.1 |
99.3 |
0.5 |
6.31 |
99.8 |
99.3 |
99.7 |
99.1 |
99.5 |
1.0 |
12.6 |
98.9 |
98.8 |
99.5 |
100.2 |
99.4 |
2.0 |
25.2 |
100.1 |
98.8 |
99.7 |
99.1 |
99.4 |
|
|
|
|
|
|
|
1.0 (wet) |
12.6 |
98.4 |
99.2 |
98.7 |
99.5 |
99.0 |
|
2.5 Retention efficiency
Six samplers were liquid-spiked with 25.5 mg (199.6 ppm) n-amyl acetate,
allowed to equilibrate for 6 h, then they had 24 L of humid air (80% relative
humidity at 23°C) pulled through them at 0.2 L/min. The samples were extracted
and analyzed. The mean recovery was 98.9%. There was an average of 2.9% found
on the back-up section of the tubes.
Table 2.5.1
Retention Efficiency (%) of n-Amyl Acetate at 0.2 L/min |
|
section
|
sample number
|
|
1 |
2 |
3 |
4 |
5 |
6 |
mean |
|
front of spiked
tube |
96.9 |
95.7 |
96.1 |
95.1 |
95.5 |
96.8 |
96.0 |
rear of spiked
tube |
2.5 |
2.2 |
3.0 |
3.5 |
2.8 |
3.1 |
2.9 |
total |
99.4 |
97.9 |
99.1 |
98.6 |
98.3 |
99.9 |
98.9 |
|
Because there was some n-amyl acetate found on the back-up portions of the tubes that were sampled at 0.2 L/min, a lower flow of 0.1 L/min
was tried on six more samplers. They were liquid-spiked with 25.5 mg (199.6 ppm) n-amyl acetate, allowed to equilibrate for 6 h, then they
had 24 L of humid air (80% relative humidity at 23°C) pulled through them at 0.1 L/min. The samples were extracted and analyzed. The mean
recovery was 99.2%. There was no analyte found on the back-up section of any of the tubes indicating this flow rate and air volume should
be used for sampling.
Table 2.5.2
Retention Efficiency (%) of n-Amyl Acetate at 0.1 L/min |
|
section
|
sample number
|
|
1 |
2 |
3 |
4 |
5 |
6 |
mean |
|
front of spiked
tube |
98.9 |
99.9 |
99.1 |
98.4 |
99.8 |
99.2 |
99.2 |
rear of spiked
tube |
0.0 |
0.0 |
0.0 |
0.0 |
0.0 |
0.0 |
0.0 |
total |
98.9 |
97.9 |
99.1 |
98.4 |
99.8 |
99.2 |
99.2 |
|
Six samplers were liquid-spiked with 25.2 mg (197.3 ppm) isoamyl acetate, allowed to equilibrate for 6 h, then they had 24 L of humid air
(80% relative humidity at 23°C) pulled through them at 0.2 L/min. The samples were extracted and analyzed. The mean recovery was 98.6%.
There was an average of 3.0% analyte found on the back-up section of the tubes.
Table 2.5.3
Retention Efficiency (%) of Isoamyl Acetate at 0.2 L/min |
|
section
|
sample number
|
|
1 |
2 |
3 |
4 |
5 |
6 |
mean |
|
front of spiked
tube |
95.4 |
94.9 |
95.1 |
96.4 |
95.5 |
96.1 |
95.6 |
rear of spiked
tube |
3.1 |
3.4 |
2.8 |
3.2 |
3.3 |
2.4 |
3.0 |
total |
98.5 |
98.3 |
97.9 |
99.6 |
98.8 |
98.5 |
98.6 |
|
Because there was some isoamyl acetate found on the back-up portions of the tubes that were sampled at 0.2 L/min,
a lower flow of 0.1 L/min was tried on six more samplers. Six samplers were liquid-spiked with 25.2 mg (198.3 ppm) isoamyl acetate,
allowed to equilibrate for 6 h, then they had 24 L of humid air (80% relative humidity at 23°C) pulled through them at 0.1 L/min.
The samples were extracted and analyzed. The mean recovery was 98.9%. There was no analyte found on the back-up section of any of
the tubes indicating this flow rate and air volume should be used for sampling.
Table 2.5.4
Retention Efficiency (%) of Isoamyl Acetate at 0.1 L/min |
|
section
|
sample number
|
|
1 |
2 |
3 |
4 |
5 |
6 |
mean |
|
front of spiked
tube |
99.2 |
99.9 |
98.3 |
97.9 |
99.4 |
98.8 |
98.9 |
rear of spiked
tube |
0.0 |
0.0 |
0.0 |
0.0 |
0.0 |
0.0 |
0.0 |
total |
99.2 |
99.9 |
98.3 |
97.9 |
99.4 |
98.8 |
98.9 |
|
2.6 Sample storage
Fifteen samplers were each spiked with 12.8 mg (100 ppm) of n-amyl acetate,
then they had 24 L at 0.1 L/min of humid air (80% relative humidity at 23°C)
drawn through them. Three samples were analyzed immediately, and the rest were
sealed. Six were stored at room temperature (23°C), while the other six were
stored at refrigerated temperature (4°C). Three samples stored at room
temperature and three samples stored at refrigerated temperature were analyzed
after 7 days and the remaining six after 14 days. The amounts recovered were
not corrected for extraction efficiency indicates good storage stability for
the time period studied. No analyte was found on the back-up section of any of
the sampling tubes.
Table 2.6.1
Storage Test for n-Amyl Acetate |
|
time (days) |
ambient storage
recovery (%) |
Refrigerated
storage
recovery (%) |
|
0 |
99.3 |
99.9 |
98.8 |
|
|
|
7 |
97.8 |
99.7 |
98.9 |
99.9 |
99.5 |
98.7 |
14 |
99.9 |
99.4 |
99.8 |
99.8 |
100.8 |
99.2 |
|
Fifteen samplers were each spiked with 12.6 mg (98.6 ppm) of isoamyl
acetate, then they had 24 L at 0.1 L/min of humid air (80% relative humidity at
23°C) drawn through them. Three samples were analyzed immediately, and the rest
were sealed. Six were stored at room temperature (23°C), while the other six
were stored at refrigerated temperature (4°C). Three samples stored at room
temperature and three samples stored at refrigerated temperature were analyzed
after 7 days and the remaining six after 14 days. The amounts recovered were
not corrected for extraction efficiency and indicate good storage stability for
the time period studied. There was no analyte found on the back-up section of
any of the sampling tubes.
Table 2.6.2
Storage Test for Isoamyl Acetate |
|
time (days) |
ambient storage
recovery (%) |
Refrigerated
storage
recovery (%) |
|
0 |
99.8 |
98.6 |
99.0 |
|
|
|
7 |
98.8 |
99.5 |
98.3 |
99.2 |
98.9 |
99.9 |
14 |
97.3 |
98.7 |
98.6 |
99.4 |
99.7 |
98.7 |
|
2.7 Recommended air volume and sampling rate
Based on the data collected in this evaluation, 24-L air samples should be
collected at a sampling rate of 0.1 L/min for 240 minutes.
3. Analytical Procedure
Adhere to the rules set down in your Chemical Hygiene Plan. Avoid skin
contact and inhalation of all chemicals and review all appropriate MSDSs.
3.1 Apparatus
A gas chromatograph equipped with an FID detector. For this evaluation, an
Agilent 6890 GC was used.
A GC column capable of separating n-amyl acetate and isoamyl acetate from the
extraction solvent, internal standard, and any potential interferences. A 60-m
× 0.32-mm i.d. capillary column, DB-Wax 0.5-µm df (J&W Scientific, Folsom, CA)
was used in this evaluation.
An electronic integrator or some other suitable means of measuring peak areas.
A Waters Millennium32 Data System and an Agilent 3396 integrator were used in
this evaluation.
Glass vials with poly(tetrafluoroethylene)-lined caps. For this evaluation 2-mL
vials were used.
A dispenser capable of delivering 1.0 mL of extraction solvent to prepare
standards and samples. If a dispenser is not available, a 1.0-mL volumetric
pipet may be used.
Volumetric flasks – 10-mL and other convenient sizes for preparing standards.
Calibrated 10-µL or 25-µL syringe for preparing standards. A Hamilton 25-µL
syringe was used for this evaluation.
A shaker or rotator to agitate samples during extraction. An Eberbach
mechanical shaker was used in this evaluation.
3.2 Reagents
n-Amyl acetate, reagent grade. Acros 99% (lot A011333301) was used in this
evaluation.
Isoamyl acetate, reagent grade. Aldrich 99% (lot MS00852AR) was used in this
evaluation.
Carbon disulfide, reagent grade. EM Science Omni-Solv 99.99% (lot 43279343) was
used in this evaluation.
N,N-Dimethylformamide (DMF), anhydrous reagent grade. Aldrich 99% (lot 11703TR)
was used in this evaluation.
p-Cymene, reagent grade. Aldrich 99% (lot 11703TR) was used in this evaluation.
The extraction solvent solution was carbon disulfide:N,N-dimethylformamide
(99:1) with 0.25µL/mL of p-cymene as internal standard.
3.3 Standard preparation
Prepare standards by spiking microliter quantities of n-amyl acetate and
isoamyl acetate from a microliter syringe into 2-mL vials, each containing 1 mL
of the extraction solution. For example, 14 µL of n-amyl acetate in 1-mL
extraction solvent is equivalent to 12.3 mg/mL and 14µL of isoamyl acetate in
1-mL extraction solvent is equivalent to 12.2 mg/mL. Standards at lower
concentrations were prepared using microliter injections into volumetric flasks
containing the extraction solvent, or pipet dilutions of analytical standards
using volumetric flasks and the extraction solvent. For this evaluation,
standards in the range of 0.001 to 25.5 mg/mL for n-amyl acetate and 0.001 to
25.2 mg/mL for isoamyl acetate were used. An additional standard from a second
source should be prepared to check the calibration.
Bracket sample concentrations with standard concentrations. If, upon analysis,
sample concentrations fall outside the range of prepared standards, prepare and
analyze additional standards to confirm instrument response, or dilute high
samples with extraction solvent and reanalyze the diluted samples.
3.4 Sample preparation
Remove the plastic end caps from the sample tubes and carefully transfer each
adsorbent section to separate 2-mL vials. Discard the glass tube, urethane foam
plug and glass wool plug.
Add 1.0 mL of extraction solvent to each vial using the same dispenser as used
for preparation of standards.
Immediately seal the vials with poly(tetrafluoroethylene)-lined caps, and shake
the vials on a shaker for 30 minutes.
3.5 Analysis
Analytical conditions.
GC conditions
|
|
Temperatures:
|
|
column: |
initial 50 °C, hold 1 min, ramp
at 5 °C/min to 150 °C, hold 5 min |
injector: |
200°C |
detector: |
250°C
|
run time: |
26 min |
column gas flow: |
1.2 mL/min (hydrogen) |
injection size: |
1.0 µL (10:1 split) |
column: |
60-m × 0.32 mm i.d. capillary
DB-Wax (df = 0.5 µm)
|
FID conditions
|
|
hydrogen flow: |
30 mL/min |
air flow: |
400 mL/min |
nitrogen makeup flow: |
25 mL/min
|
retention times: |
5.6 min (CS2); 8.1 min (benzene
contaminant in CS2); 11.6 min (isoamyl acetate); 12.9 min (n-amyl acetate);
15.7 min (p-cymene): 17.4 min (DMF) |
|
Figure 3.5.1 A chromatogram of 12.6
mg/mL isoamyl acetate and 12.8 mg/mL n-amyl acetate in 99:1 CS2:DMF with
0.25 µl/mL p-cymene as internal standard. [Key: (1) CS2; (2) isoamyl
acetate; (3) n-amyl acetate; (4) p-cymene; and (5) DMF] |
Peak areas are measured with an integrator or other
suitable means.
An internal standard (ISTD) calibration method is used. A calibration curve can
be constructed by plotting internal standard corrected response of standard
injections versus micrograms of analyte per sample. Bracket the samples with
freshly prepared analytical standards over the range of concentrations.
|
|
Figure 3.5.2 Calibration curve of
n-amyl acetate. (y = 3.05E5x – 6720) |
Figure 3.5.3 Calibration curve of
isoamyl acetate.
(y = 3.09E5x – 2.57E4) |
3.6 Interferences (analytical)
Any compound that produces a GC response and has a similar retention time as the
analyte is a potential interference. If any potential interferences were
reported, they should be considered before samples are extracted. Generally,
chromatographic conditions can be altered to separate an interference from the
analyte.
When necessary, the identity or purity of an analyte peak may be confirmed by
additional analytical data. The mass spectra in Figures 3.6.1 and 3.6.2 were
obtained from the NIST spectral library.
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Figure 3.6.1 Mass spectrum ofn-amyl acetate. |
Figure 3.6.2 Mass spectrum of isoamyl acetate. |
3.7 Calculations
The amount of analyte per sampler is obtained from the appropriate
calibration curve in terms of micrograms per sample, uncorrected for extraction
efficiency. This total amount is then corrected by subtracting the total amount
(if any) found on the blank. The air concentration is calculated using the
following formulas.
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where: |
CM is concentration by weight |
M is micrograms per sample |
V is liters of air sampled |
EE is extraction efficiency, in
decimal form |
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where: |
CV is concentration by volume (ppm) |
VM is 24.46 (molar volume at NTP) |
CM is concentration by weight |
Mr is molecular weight = 130.19 |
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4. Recommendations for Further Study
A sampler capacity test should be performed with a test atmosphere to better
determine sampler capacity.
References
1. NIOSH Manual of Analytical Methods, 2nd ed.; Cincinatti, OH, Vol. 2,
Method S45
2. NIOSH Manual of Analytical Methods, 2nd ed.; Cincinatti, OH, Vol. 2,
Method S51.
3. NIOSH Method 1450 Esters 1, www.cdc.gov/niosh, (accessed 5/15/03).
4. Lewis, R., Ed., Sax’s Dangerous Properties of Industrial Materials, Tenth
ed.; John Wiley & Sons Inc.: New York, 2000, Vol. 3, p 249.
5. Lewis, R., Ed., Sax’s Dangerous Properties of Industrial Materials, Tenth
ed.; John Wiley & Sons Inc.: New York, 2000, Vol. 3, p 2119.
6. Material Safety Data Sheet: n-Amyl acetate, Chemwatch, Victoria,
Australia, (accessed 2/17/03).
7. Material Safety Data Sheet: Isoamyl acetate, Chemwatch, Victoria,
Australia, (accessed 2/17/03).
8. Title 21, Part 172, Section 172.515, Synthetic Flavorings Substances and
Adjuvants, www.fda.gov, (accessed 3/17/03).
9. Lewis, R., Ed., Hawley’s Condensed Chemical Dictionary, 14th ed., John
Wiley & Sons Inc., New York, 2001, p 73.
10. Lewis, R., Ed., Hawley’s Condensed Chemical Dictionary, 14th ed., John
Wiley & Sons Inc., New York, 2001, p 649.
11. Material Safety Data Sheet: n-Amyl acetate, Chemwatch, Victoria,
Australia, (accessed 2/17/03).
12. Lewis, R., Ed., Sax’s Dangerous Properties of Industrial Materials,
Tenth ed., Vol. 3, John Wiley & Sons Inc., New York, 2000, p 249.
13. OSHA Chemical sampling Information, www.osha.gov (accessed 12/17/03).
14. Material Safety Data Sheet: Isoamyl acetate, Chemwatch, Victoria,
Australia, (accessed 2/17/03).
15. O’Neil, M., Ed., The Merck Index, 13th ed., Merck & Co., Inc.,
Whitehouse Station, NJ, 2001, p 919.
16. OSHA
Chemical sampling Information, www.osha.gov (accessed 12/17/03).
17. Isoamyl acetate, NIOSH Pocket Guide to Chemical Hazards, www.cdc.gov/niosh
(accessed 12/17/03).
18. Isoamyl acetate, NIOSH Pocket Guide to Chemical Hazards, www.cdc.gov/niosh
(accessed 12/17/03).
19. Evaluation Guidelines For Air Sampling Methods Utilizing Chromatographic
Analysis; www.osha.gov, (accessed 11/15/03).
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