CARBITOL CARBITOL ACETATE
Method number: |
PV2013 |
|
Matrix: |
Air |
|
Target concentration: |
25 ppm (140 mg/m3) carbitol 25 ppm
(180 mg/m3) carbitol acetate |
|
Procedure: |
Samples are collected by drawing a known volume of air through a
charcoal tube. Samples are desorbed with 5:95 methanol:methylene
chloride and analyzed by gas chromatography with a flame ionization
detector (GC-FID). |
|
Air volume and sampling rate studied: |
10 liters at 0.2 Lpm. |
|
Status of method: |
Stopgap method. This method has been only partially evaluated
and is presented for information and trial use. |
|
Date: January, 1993 |
Chemist: Mary E.
Eide |
Organic Service Branch I OSHA Technical Center Salt
Lake City, Utah
1. General Discussion
1.1. Background
1.1.1. History of procedure
There have been many requests for sampling and analytical
procedures for carbitol and carbitol acetate. They have been
directed to follow OSHA method 79 for 2-ethoxyethanol
and 2-ethoxyethyl acetate, since carbitol and carbitol
acetate are related to this compound (Ref. 5.1.). In this method the
samples are collected on charcoal tubes and desorbed with 95:5
methylene chloride:methanol. This study was undertaken to gather the
data necessary to verify that this is the proper procedure.
Desorption of carbitol acetate was attempted using carbon disulfide
but the recovery was nonlinear ranging from 44.9% to 74.9% for
loadings 1.011 to 4.046 mg. These recoveries were low and a better
desorbing solvent was needed. The 95:5 methylene chloride:methanol
was tried and found to give desorptions of 96.1% for carbitol and
100% for carbitol acetate. Retention and storage studies showed good
recoveries for charcoal tubes.
1.1.2. Potential workplace exposure (Ref. 5.2.)
Carbitol is used in finger nail polish remover, for setting the
twist and conditioning yarns and cloth, in lecithin manufacturing,
in textile printing and soaps, in lacquers, in organic synthesis, as
a brake fluid diluent, and as a solvent for dyes, nitrocelluloses,
resins, mineral oil soap, mineral oil-sulfonated oil mixtures, and
nonaqueous stains for wood. Carbitol acetate is used in lacquers,
printing inks, coatings, and as a solvent for cellulose esters,
gums, and resins.
1.1.3. Toxic Effects (This section is for information purposes
and should not be taken as the basis for OSHA policy.)(Ref. 5.3.)
Carbitol and carbitol acetate are considered to be of low
toxicity by the FDA and have been approved for use in cosmetics.
Rabbits exposed on the skin to 500 mg/kg of carbitol and carbitol
acetate showed mild reactions. The LD50 orally for guinea pigs was
3.67 g/kg for carbitol and 3.93 g/kg for carbitol acetate.
1.1.4. Physical properties (Ref. 5.4.):
Carbitol
Compound: |
|
Synonyms: |
APV; Carbitol cellosolve; Carbitol solvent;
Diethylene glycol ethyl ether; Diglycol monoethyl ether;
Dioxitol; Dowanol; Dowanol DE; Ethoxy diglycol;
2-(2-ethoxyethoxy) ethanol; Ethyl carbitol; Ethyl digol;
Ethyl diethylene glycol; Ethylene diglycol monoethyl ether;
Poly-solv; Losungsmittel APV; Monoethyl ether of diethylene
glycol; Solvolsol |
Molecular weight: |
134.2 |
Density: |
0.9855 |
Boiling point: |
196° |
Flash point: |
96° (205°)(open cup) |
Odor: |
mildly sweet |
Color: |
clear liquid |
Molecular formula: |
C6H14O3 |
CAS: |
111-90-0 |
IMIS: |
D615 |
RTECS: |
34453; RR8750000 |
Carbitol acetate
Compound: |
|
Synonyms: |
2-(2-Ethoxyethoxy)ethanol acetate; Diethylene
glycol monoethyl ether acetate; Diglycolmonoethyl ether
acetate; Ektasolve DE acetate; Glycol ether DE acetate |
Molecular weight: |
176.24 |
Density: |
1.0114 |
Boiling point: |
219° |
Freezing point: |
-25° |
Flash point: |
110° (230°) (open cup) |
Odor: |
mildly sweet |
Color: |
clear liquid |
Molecular formula: |
C8H16O4 |
CAS: |
112-15-2 |
IMIS: |
C128 |
RTECS: |
34454; KK8925000 |
|
1.2. Limit defining parameters
1.2.1. The detection limit of the analytical procedure is 5 ng
carbitol and carbitol acetate, with a 1 µL injection volume. This is
the same as 5 µg/mL. This is the smallest amount which could be
detected under normal operating conditions.
1.2.2. The overall detection limit is 0.09 ppm carbitol and 0.07
ppm carbitol acetate based on a 10 liter air volume. (All ppm
amounts in this study are based on a 10 L air volume.)
1.3. Advantages
1.3.1. The sampling procedure is convenient.
1.3.2. The analytical method is reproducible and sensitive.
1.3.3. Re-analysis of samples is possible.
1.3.4. It may be possible to analyze other compounds at the same
time.
1.3.5. Interferences may be avoided by proper selection of column
and GC parameters.
1.4. Disadvantages
Methylene chloride is very volatile. A fan blowing on the
instrument may be advisable to obtain replicate injections, when using
an autosampler.
2. Sampling procedure
2.1. Apparatus
2.1.1. A calibrated personal sampling pump, the flow of which
can be determined within ±5% at the recommended flow.
2.1.2. Charcoal tubes, lot 120, containing 100 mg adsorbing
section with a 50 mg backup section separated by a 2 mm portion of
urethane foam, with a silanized glass wool plug before the adsorbing
section and a 3 mm plug of urethane foam at the back of the backup
section. The ends are flame sealed and the glass tube containing the
adsorbent is 7 cm long, with a 6 mm O.D. and 4 mm I.D., SKC tubes or
equivalent.
2.2. Sampling technique
2.2.1. The ends of the charcoal tube are opened immediately
before sampling.
2.2.2. Connect the charcoal tube to the sampling pump with
flexible tubing.
2.2.3. Tubes should be placed in a vertical position to minimize
channeling, with the smaller section towards the pump.
2.2.4. Air being sampled should not pass through any hose or
tubing before entering the charcoal tube.
2.2.5. Seal the charcoal tube with plastic caps immediately after
sampling. Seal each sample lengthwise with OSHA Form-21 sealing
tape.
2.2.6. With each batch of samples, submit at least one blank tube
from the same lot used for samples. This tube should be subjected to
exactly the same handling as the samples (break ends, seal, &
transport) except that no air is drawn through it.
2.2.7. Transport the samples (and corresponding paperwork) to the
lab for analysis.
2.2.8. Bulks submitted for analysis must be shipped in a separate
mailing container from other samples.
2.3. Desorption efficiency
Six tubes were spiked with 0.138 mg (2.51 ppm), 0.69 mg (12.6 ppm),
1.38 mg (25.1 ppm), and 2.76 mg (50.3 ppm) carbitol, and 0.182 mg
(2.52 ppm), 0.910 mg (12.6 ppm), 1.82 mg (25.2 ppm), and 3.64 mg (50.5
ppm) carbitol acetate. They were allowed to equilibrate overnight at
room temperature. They were opened, each section placed into a
separate 2 mL vial, desorbed with 1 mL of the desorbing solution,
desorbed for 30 minutes with occasional shaking, and were analyzed by
gas chromatography with a flame ionization detector. The overall
average for carbitol was 96.1% recovered (Table 1). The overall
average for carbitol acetate was 100% recovered (Table 2).
Table 1 Carbitol Desorption Efficiency
|
|
% Recovered |
Tube# |
0.138mg |
0.690mg |
1.38mg |
2.76mg |
|
1 |
93.7 |
97.4 |
97.4 |
97.3 |
2 |
94.0 |
96.4 |
98.0 |
97.1 |
3 |
94.1 |
95.6 |
97.4 |
96.5 |
4 |
93.8 |
95.8 |
97.4 |
96.9 |
5 |
94.2 |
94.6 |
97.9 |
97.0 |
6 |
93.7 |
95.0 |
97.5 |
96.8 |
|
average |
93.9 |
95.8 |
97.6 |
96.9 |
|
overall average |
96.1 |
standard deviation |
± 1.52 |
|
Table 2 Carbitol acetate Desorption Study
|
|
% Recovered |
Tube# |
0.182mg |
0.910mg |
1.82mg |
3.64mg |
|
1 |
99.5 |
100 |
101 |
101 |
2 |
99.8 |
100 |
100 |
101 |
3 |
98.5 |
100 |
100 |
100 |
4 |
99.2 |
100 |
101 |
101 |
5 |
98.2 |
101 |
101 |
100 |
6 |
98.1 |
100 |
101 |
100 |
|
Average |
98.9 |
100 |
101 |
101 |
|
Overall average |
100 |
Standard deviation |
± 0.885 |
|
2.4. Retention efficiency
Six tubes were spiked with 2.76 mg (50.3 ppm) carbitol and 3.64 mg
(50.5 ppm) carbitol acetate, allowed to equilibrate overnight, and had
10 liters humid air (91% RH) pulled through them at 0.2 Lpm. They were
opened, desorbed, and analyzed by GC-FID. There was no carbitol or
carbitol acetate found on the backup portions of the tubes. The values
for carbitol were corrected for desorption efficiency. The retention
efficiency averaged 98.4% for carbitol and 101% for carbitol
acetate.(Table 3)
Table 3 Retention Efficiency
|
|
% Recovered |
Tube |
Carbitol |
|
Carbitol acetate |
# |
'A' |
'B' |
Total |
|
'A' |
'B' |
Total |
|
1 |
98.2 |
0.0 |
98.2 |
|
102 |
0.0 |
102 |
2 |
98.3 |
0.0 |
98.3 |
|
100 |
0.0 |
100 |
3 |
99.2 |
0.0 |
99.2 |
|
100 |
0.0 |
100 |
4 |
98.4 |
0.0 |
98.4 |
|
100 |
0.0 |
100 |
5 |
97.5 |
0.0 |
97.5 |
|
101 |
0.0 |
101 |
6 |
98.9 |
0.0 |
98.8 |
|
101 |
0.0 |
101 |
|
average 98.4 |
average 101 |
|
2.5. Storage
Tubes were spiked with 1.38 mg (25.1 ppm) carbitol and 1.82 mg
(25.2 ppm) carbitol acetate, and stored at room temperature until
opened and analyzed. The recoveries for carbitol were corrected for
desorption efficiency. The recoveries averaged 98.8% for carbitol and
98.0% for carbitol acetate over the 14 days stored.(Table 4)
Table 4 Storage Study
|
|
% Recovered |
Day |
Carbitol |
Carbitol acetate |
|
7 |
100 |
98.0 |
7 |
95.7 |
99.9 |
7 |
99.3 |
98.6 |
14 |
98.5 |
95.6 |
14 |
98.2 |
96.3 |
14 |
101 |
99.5 |
|
average |
98.8 |
98.0 |
|
2.6. Precision
The precision was calculated using the area counts from six
injections of each standard at concentrations of 0.138, 0.690, 1.38,
and 2.76 mg/mL carbitol; and 0.182, 0.910, 1.82, and 3.64 mg/mL
carbitol acetate in the desorbing solution. The pooled coefficient of
variation was 0.00349 for carbitol and 0.00369 for carbitol
acetate.(Tables 5 and 6)
Table 5 Carbitol Precision Study
|
Injection |
Number |
0.l38mg/mL |
0.690mg/mL |
1.38mg/mL |
2.76mg/mL |
|
1 |
26886 |
122733 |
249185 |
493394 |
2 |
26869 |
123008 |
248652 |
498230 |
3 |
26832 |
122859 |
245787 |
494524 |
4 |
26847 |
123003 |
246254 |
497276 |
5 |
26859 |
122850 |
246099 |
496050 |
6 |
26884 |
122959 |
246506 |
495515 |
|
Average |
26863 |
122902 |
247081 |
495832 |
|
Standard |
Deviation |
± 21.2 |
± 108 |
± 1452 |
± 1769 |
|
CV |
0.000789 |
0.000879 |
0.00588 |
0.00357 |
|
Pooled CV |
0.00349 |
|
Table 6 Carbitol acetate Precision Study
|
Injection |
Number |
0.l82mg/mL |
0.9l0mg/mL |
1.82mg/mL |
3.64mg/mL |
|
1 |
35941 |
173819 |
356698 |
705803 |
2 |
36111 |
173402 |
357304 |
707101 |
3 |
36454 |
174829 |
357788 |
706641 |
4 |
36301 |
174738 |
357078 |
707308 |
5 |
36141 |
174710 |
357560 |
706848 |
6 |
36521 |
174072 |
355886 |
709041 |
|
Average |
36245 |
174262 |
355886 |
707124 |
|
Standard |
Deviation |
± 221 |
± 587 |
± 685 |
± 1074 |
|
CV |
0.00610 |
0.00337 |
0.00192 |
0.00152 |
|
Pooled CV |
0.00369 |
|
where:
A(1), A(2),A(3),A(4) = # of injections at each level CVl,
CV2, CV3, CV4 = Coefficients at each level
2.7. Air volume and sampling rate studied
2.7.1. The air volume studied is 10 liters.
2.7.2. The sampling rate studied is 0.2 liters per minute.
2.8. Interferences
Suspected interferences should be listed on sample data sheets.
2.9. Safety precautions
2.9.1. Sampling equipment should be placed on an employee in a
manner that does not interfere with work performance or safety.
2.9.2. Safety glasses should be worn at all times.
2.9.3. Follow all safety practices that apply to the workplace
being sampled.
3. Analytical method
3.1. Apparatus
3.1.1. Gas chromatograph equipped with a flame ionization
detector. A Hewlett Packard 5890 Gas chromatograph was used in this
study.
3.1.2. An electronic integrator or some other suitable method of
measuring peak areas.
3.1.3. GC column capable of separating the analyte and an
internal standard from any interferences. The column used in this
study was a 15 meter DB-WAX capillary column 0.32 mm I.D. with a
0.25 p film thickness. An alternate column is a 60 meter DB-WAX
capillary column 0.32 mm I.D. with a 1.0µ film thickness.
3.1.4. Two milliliter vials with Teflon-lined caps.
3.1.5. A 10 µL syringe or other convenient size for sample
injection.
3.1.6. Pipets for dispensing the desorbing solution. The Glenco 1
mL dispenser was used in this method.
3.1.7. Volumetric flasks - 5 mL and other convenient sizes for
preparing standards.
3.2 Reagents
3.2.1. Purified GC grade nitrogen, hydrogen, and air.
3.2.2. Carbitol, Reagent grade
3.2.3. Carbitol acetate, Reagent grade
3.2.4. Methanol, HPLC grade
3.2.5. Methylene chloride, HPLC grade
3.2.6. n-Hexanol, Reagent grade, used as an internal standard
3.2.7. The desorbing solution is 5:95 methanol:methylene chloride
with 0.25 µL/mL n-hexanol internal standard.
3.3. Sample preparation
3.3.1. Sample tubes are opened and the front and back section of
each tube are placed in separate 2 mL vials.
3.3.2. Each section is desorbed with 1 mL of the desorbing
solution.
3.3.3. The vials are sealed immediately and allowed to desorb for
30 minutes with occasional shaking.
3.4. Standard preparation
3.4.1. Standards are prepared by diluting a known quantity of
carbitol and carbitol acetate with the desorbing solution.
3.4.2. At least two separate standards should be made.
3.4.3. A third analytical standard should be prepared at a higher
concentration to check the earity of the detection. For this study
two standards at 1 µL/mL (0.986 mg/mL carbitol and 1.011 mg/mL
carbitol acetate) and one standard at 4 µL/mL (3.942 mg/mL carbitol
and 4.046 mg/mL carbitol acetate) were used.
3.5. Analysis
3.5.1. Gas chromatograph conditions.
Flow rates (mL/min.) |
Temperature (°) |
Nitrogen(make-up): |
30 |
Injector: |
180 |
Hydrogen(carrier): |
2 |
Detector: |
220 |
Hydrogen(detector): |
60 |
Column: |
60-110° |
Air: |
410 |
|
@10°/min |
|
Injection size: |
1 µL |
Chromatogram: |
see Figure 1 |
3.5.2. Gas chromatograph conditions for the 60 meter DB-WAX
capillary column.
Flow rates (mL/min.) |
Temperature (°) |
Nitrogen(make-up): |
30 |
Injector: |
180 |
Hydrogen(carrier): |
2 |
Detector: |
220 |
Hydrogen(detector): |
60 |
Column: |
100-180° |
Air: |
410 |
|
Injection size: |
1 µL |
Chromatogram: |
see Figure 2 |
3.5.3. Peak areas are measured by an integrator or other suitable
means.
3.6. Interferences (analytical)
3.6.1. Any compound having the general retention time of the
analyte or the internal standard used is an interference. Possible
interferences should be listed on the sample data sheet. GC
parameters should be adjusted if necessary so these interferences
will pose no problems.
3.6.2. Retention time data on a single column is not considered
proof of chemical identity. Samples over the target concentration
should be confirmed by GC/Mass Spec or other suitable means.
3.7. Calculations
3.7.1. The instrument is calibrated with a standard of 0.986
mg/mL (1 µL/mL) carbitol and 1.011 mg/mL carbitol acetate in the
desorbing solution. The linearity of the calibration is checked with
a standard of 3.942 mg/mL (4 pL/mL) carbitol and 4.046 mg/mL (4
pL/mL) carbitol acetate in the desorbing solution.
3.7.2. If the calibration is non-linear, two more standards must
be analyzed so a calibration curve can be plotted and sample values
obtained.
3.7.3. To calculate the concentration of analyte in the air
sample the following formulas are used:
(µg/m)(desorption volume)
(desorption efficiency) |
= mass of analyte in
sample |
(mass of analyte in sample)
molecular weight |
= number of moles of
analyte |
(number of moles of analyte) |
(molar volume at 25°C &
760mm) |
= |
volume the analyte will occupy
at 25°C & 760mm |
(volume analyte
occupies)(106)
(air volume) |
= ppm |
* All units must cancel.
3.7.4. The above equations can be consolidated to form the
following formula, used to calculate the ppm of analyte in the
sample based on a 10 liter air sample:
(µg/mL)(DV)(24.45)(106)
(100 L)(DE)(MW) |
× |
(g)
(1000 mg) |
× |
(mg)
(1000 µg) |
= ppm |
µg/mL |
= |
concentration of analyte in sample or standard |
24.45 |
= |
Molar volume (liters/mole) at 25 ° and 760 mm Hg. |
Mw |
= |
Molecular weight (g/mole) |
DV |
= |
Desorption volume |
10 L |
= |
10 liter air sample |
DE |
= |
Desorption efficiency |
3.7.5. This calculation is done for each section of the sampling
tube and the results added together.
3.8. Safety precautions
3.8.1. All handling of solvents should be done in a hood.
3.8.2. Avoid skin contact with all solvents.
3.8.3. Wear safety glasses at all times.
4. Recommendations for further study
Collection studies need to be performed.
Figure 1.
An analytical standard of 1 µL/mL carbitol and carbitol acetate in
the desorbing solvent of 5:95 methanol:methylene chloride with 0.25
µL/mL n-hexanol internal standard, analyzed with a 15 meter DB-WAX
capillary column.
Figure 2.
An analytical standard of 1 uL/mL carbitol and carbitol acetate in
the desorbing solvent of 5:95 methanol:methylene chloride with 0.25
µL/mL n-hexanol internal standard, analyzed with a 60 meter DB-WAX
capillary column.
5. References
5.1. Elskamp, C., Method 79, "2-Methoxyethanol,
2-methoxyethyl acetate, 2-ethoxyethanol, and
2-ethoxyethyl acetate", Organic Methods Evaluation
Branch, OSHA Analytical Laboratory, 1990.
5.2. Sax, N., Lewis, R., "Hawley's Condensed Chemical Dictionary",
Eleventh Edition, Van Nostrand Reinhold Co., New York, 1987, p. 391.
5.3. Sweet, D., "Registry of Toxic Effects of Chemical Substances",
1985-86 Edition, U.S. Department of Health and Human Services, Public
Health Service, Center for Disease Control, NIOSH, 1987, Vol. 3, p.
2280-l.
5.4. Windholz, M., "The Merck Index", Eleventh Edition, Merck &
Co., Rahway N.J., 1989, p. 272.
|