CARBITOL
CARBITOL ACETATE

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.