2-METHOXYPHENOL 3-METHOXYPHENOL 4-METHOXYPHENOL
Method number: |
PV2039 |
|
Matrix: |
Air |
|
Target concentration: |
5 mg/m3 OSHA 1989 TWA PEL for 4-methoxyphenol
This has been vacated. |
|
Procedure: |
Samples are collected by drawing a known volume of air through an XAD-7 tube. Samples are desorbed with methanol and
analyzed by gas chromatography with a flame ionization detector (GC-FID). |
|
Air volume and sampling rate studied: |
20 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: March, 1992 Revised: March, 1994 |
Chemist: Mary E. Eide |
Organic Service Branch I
OSHA Salt Lake Technical Center
Salt Lake City, Utah
1. General Discussion
1.1. Background
1.1.1. History of procedure
The OSHA Technical Center has received many requests for a
sampling and analytical procedure for the isomers of methoxyphenol. OSHA promulgated an
exposure standard for 4-methoxyphenol in January, 1989, at a level of 5 mg/m3.
OSHA method 32 recommends collection of phenol and cresol on XAD-7 tubes and desorption
with methanol (Ref. 5.1.). This procedure was found to give good recoveries for the
methoxyphenol isomers, in desorption, retention, and storage studies.
1.1.2. Potential workplace exposure (Ref. 5.2. and 5.3.)
Methoxyphenols are used in the manufacture of antioxidants,
and pharmaceuticals. 2-Methoxyphenol is used as an expectorant, and in synthetic flavors.
4-Methoxyphenol is used to manufacture plasticizers, dyestuffs, stabilizer for chlorinated
hydrocarbons and ethyl cellulose, inhibitor for acrylic monomers and acrylonitriles, and
as an UV inhibitor.
1.1.3. Toxic Effects (This section is for information
purposes and should not be taken as the basis for OSHA policy.)(Ref. 5.2., 5.3., and 5.4.)
Methoxyphenols are eye, skin, and mucous membrane irritants. Ingestion produces burning in the mouth and throat, followed by
gastrointestinal distress, tremors, and collapse. 3-Methoxyphenol has also been reported
to cause menstrual cycle changes or disorders.
1.1.4. Physical properties
2-Methoxyphenol (Ref. 5.2):
Compound: |
![Structural Formula](https://webarchive.library.unt.edu/eot2008/20090512175723im_/http://www.osha.gov/dts/sltc/methods/partial/pv2039/methcom1.gif) |
Synonyms: |
Guaiacol; o-Methoxyphenol; Methyl catechol;
Anastil; 1-Hydroxy-2-methoxybenzene; Pyrocatechol methyl ether;
o-Hydroxyanisole; Pyroguaiac acid |
Molecular weight: |
124.15 |
Melting point: |
28°C |
Boiling point: |
205°C |
Flash point: |
82.2°C (180°F) (open cup) |
Odor: |
sweet phenolic |
Color: |
white to pale yellow crystals |
Molecular formula: |
C7H8O2 |
CAS: |
90-05-1 |
IMIS: |
M168 |
RTECS: |
56973; SL7525000 |
3-Methoxyphenol (Ref. 5.5):
Compound: |
![Structural Formula](https://webarchive.library.unt.edu/eot2008/20090512175723im_/http://www.osha.gov/dts/sltc/methods/partial/pv2039/methcom2.gif) |
Synonyms: |
Resorcinol monomethyl ether; m-Methoxyphenol; m-Hydroxyanisole |
Molecular weight: |
124.15 |
Density: |
1.131 |
Melting point: |
<-17°C |
Boiling point: |
244°C |
Flash point: |
82.2°C (180°F)(open cup) |
Odor: |
sweet phenolic |
Color: |
amber liquid |
Molecular formula: |
C7H8O2 |
CAS: |
150-19-6 |
IMIS: |
M169 |
RTECS: |
56972; SL7524000 |
4-Methoxyphenol (Ref. 5.3.):
Compound: |
![Structural Formula](https://webarchive.library.unt.edu/eot2008/20090512175723im_/http://www.osha.gov/dts/sltc/methods/partial/pv2039/methcom3.gif) |
Synonyms: |
r-Methoxyphenol; Hydroquinone monomethyl ether;
r-Hydroxyanisole |
Molecular weight: |
124.15 |
Melting point: |
52.5°C |
Boiling point: |
243°C |
Flash point: |
124°C (257°)(closed cup) |
Odor: |
sweet phenolic |
Color: |
white waxy solid |
Molecular formula: |
C7H8O2 |
CAS: |
150-76-5 |
IMIS: |
M329 |
RTECS: |
56974; SL7700000 |
1.2. Limit defining parameters
1.2.1. The detection limit of the analytical procedure for each isomer of methoxyphenol is 1 µg.
This is the smallest amount that could be detected under normal operating conditions.
1.2.2. The overall detection limit for each isomer of methoxyphenol is 0.05
mg/m3. (All ppm amounts in this study are based on a 20 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. Reanalysis 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
none known
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. XAD-7 tubes containing 15/50 mesh XAD-7 with a 100
mg adsorbing section with a 50 mg backup section separated by a silanized glass wool plug,
with a silanized glass wool plug before and after the adsorbing sections. The ends are
flame sealed and the glass tube containing the adsorbent is 8 cm long, with a 8 mm 0.D.
and 6 mm I.D., SKC tubes or equivalent.
2.2. Sampling technique
2.2.1. Open the ends of the XAD-7 tube immediately before sampling.
2.2.2. Connect the XAD-7 tube to the sampling pump with flexible tubing.
2.2.3. Place the tubes 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 XAD-7 tube.
2.2.5. Seal the XAD-7 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 container from other samples.
2.3. Desorption efficiency
Six tubes were spiked at each loading of 10 µg (0.5mg/m3),
50 µg (2.5 mg/m3), and 100 µg (5.0 mg/m3) for each methoxyphenol,
approximately. 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 for 30 minutes with occasional shaking, and analyzed by GC-FID. The overall
average was 99.7% for 2-methoxyphenol, 99.9% for 3-methoxyphenol, and 99.1% for
4-methoxyphenol.(Tables 1, 2, and 3)
Table 1
2-Methoxyphenol Desorption Efficiency
|
Tube# |
|
% Recovered |
|
|
10.1 µg |
50.5 µg |
101 µg |
|
1 |
100 |
99.5 |
102 |
2 |
101 |
98.7 |
101 |
3 |
102 |
102 |
99.1 |
4 |
97.5 |
95.9 |
99.8 |
5 |
102 |
100 |
99.8 |
6 |
101 |
96.4 |
97.6 |
average |
101 |
98.8 |
99.9 |
overall average |
99.7 |
|
standard deviation |
± 1.92 |
|
|
Table 2
3-Methoxyphenol Desorption Efficiency
|
Tube# |
|
% Recovered |
|
|
11.0 µg |
55.0 µg |
110 µg |
|
1 |
100 |
97.6 |
101 |
2 |
98.6 |
97.9 |
101 |
3 |
97.4 |
98.7 |
100 |
4 |
103 |
98.4 |
102 |
5 |
102 |
101 |
102 |
6 |
99.2 |
96.9 |
101 |
average |
100 |
98.4 |
101 |
overall average |
99.9 |
|
standard deviation |
± 1.85 |
|
|
Table 3
4-Methoxyphenol Desorption Efficiency
|
Tube# |
|
% Recovered |
|
|
10.2 µg |
51.0 µg |
102 µg |
|
1 |
98.6 |
97.9 |
99.4 |
2 |
96.3 |
97.8 |
99.6 |
3 |
98.7 |
97.0 |
99.3 |
4 |
102 |
98.0 |
101 |
5 |
99.9 |
102 |
99.4 |
6 |
101 |
97.4 |
98.5 |
average |
99.4 |
98.4 |
99.5 |
overall average |
99.1 |
|
standard deviation |
± 1.63 |
|
|
2.4. Retention efficiency
Six tubes were spiked with 101 µg (5.05 mg/m3)
2-methoxyphenol, 110 µg (5.50 mg/m3) 3-methoxyphenol, and 102 µg (5.10 mg/m3)
4-methoxyphenol, allowed to equilibrate overnight, and then 20 liters humid air (91% RH)
were pulled through them. They were opened, desorbed, and analyzed by GC-FID. The
retention efficiency averaged 99.8% for 2-methoxyphenol, 99.5% for 3-methoxyphenol, and
99.1% for 4-methoxyphenol. There was little or no methoxyphenol found on the backup
portions of the tubes. (Tables 4, 5, and 6)
Table 4
2-Methoxyphenol Retention Efficiency
(101 µg spiked)
|
Tube # |
% Recovered |
% Recovered |
Total |
|
'A' |
'B' |
|
|
1 |
98.9 |
0.7 |
99.6 |
2 |
98.1 |
0.0 |
98.1 |
3 |
100 |
0.0 |
100 |
4 |
99.1 |
0.0 |
99.1 |
5 |
102 |
0.0 |
102 |
6 |
100 |
0.0 |
100 |
|
average |
99.8 |
|
Table 5
3-Methoxyphenol Retention Efficiency
(110 µg spiked)
|
Tube # |
% Recovered |
% Recovered |
Total |
|
'A' |
'B' |
|
|
1 |
99.7 |
0.0 |
99.7 |
2 |
100 |
0.0 |
100 |
3 |
99.0 |
0.0 |
99.0 |
4 |
97.4 |
0.0 |
97.4 |
5 |
101 |
0.0 |
101 |
6 |
99.6 |
0.0 |
99.6 |
|
average |
99.5 |
|
Table 6
4-Methoxyphenol Retention Efficiency
(102 µg spiked)
|
Tube # |
% Recovered |
% Recovered |
Total |
|
'A' |
'B' |
|
|
1 |
98.1 |
0.0 |
98.1 |
2 |
98.2 |
0.0 |
98.2 |
3 |
101 |
0.0 |
101 |
4 |
98.3 |
0.0 |
98.3 |
5 |
100 |
0.0 |
100 |
6 |
98.8 |
0.0 |
98.8 |
|
average |
99.1 |
|
2.5. Storage
Six tubes were spiked with 101 µg (5.05 mg/m3)
2-methoxyphenol, 110 µg (5.50 mg/m3) 3-methoxyphenol, and 102 µg (5.10 mg/m3)
4-methoxyphenol. They were stored at room temperature until opened and analyzed. The
recoveries averaged 101% for 2-methoxyphenol, 100% for 3-methoxyphenol, and 99.7% for
4-methoxyphenol for the 14 days stored. (Tables 7, 8, and 9)
Table 7
2-Methoxyphenol Storage Study
(101 µg spiked)
|
Day |
% Recovered |
|
7 |
102 |
7 |
100 |
7 |
100 |
14 |
103 |
14 |
99.8 |
14 |
99.2 |
average |
101 |
|
Table 8
3-Methoxyphenol Storage Study
(110 µg spiked)
|
Day |
% Recovered |
|
7 |
101 |
7 |
99.2 |
7 |
99.8 |
14 |
102 |
14 |
100 |
14 |
100 |
average |
100 |
|
Table 9
4-Methoxyphenol Storage Study
(102 µg spiked)
|
Day |
% Recovered |
|
7 |
100 |
7 |
98.8 |
7 |
99.2 |
14 |
101 |
14 |
99.5 |
14 |
99.7 |
average |
99.7 |
|
2.6. Precision
The precision was calculated using the area counts from six
injections of each standard at concentrations of approximately 10, 50, 100, and 200 µg/mL
of each methoxyphenol in the desorbing solution. The pooled coefficient of variation was
0.0226 for 2-methoxyphenol, 0.0180 for 3-methoxyphenol, and 0.0147 for
4-methoxyphenol.(Tables 10, 11, and 12)
Table 10
Precision Study 2-Methoxyphenol
|
Injection |
|
Number |
10.1µg/mL |
50.5µg/mL |
101µg/mL |
202µg/mL |
|
1 |
1605 |
8858 |
19242 |
40786 |
2 |
1691 |
8829 |
19596 |
40180 |
3 |
1567 |
8796 |
19406 |
39842 |
4 |
1543 |
8712 |
18530 |
40642 |
5 |
1553 |
8646 |
19569 |
40656 |
6 |
1609 |
8581 |
18602 |
39863 |
Average |
1595 |
8737 |
19158 |
40328 |
Standard |
|
Deviation |
±54.3 |
109 |
476 |
422 |
CV |
0.0340 |
0.0125 |
0.0248 |
0.0105 |
Pooled CV |
0.0226 |
|
|
Table 11
Precision Study 3-Methoxyphenol
|
Injection |
|
Number |
11.0µg/mL |
55.0µg/mL |
110µg/mL |
220µg/mL |
|
1 |
2011 |
9931 |
20670 |
42296 |
2 |
2024 |
9590 |
20444 |
42539 |
3 |
1933 |
9993 |
20071 |
42241 |
4 |
1873 |
9735 |
20468 |
42104 |
5 |
1966 |
9675 |
20586 |
42341 |
6 |
1968 |
9548 |
20126 |
42090 |
Average |
1963 |
9745 |
20394 |
42269 |
Standard |
|
Deviation |
±54.9 |
181 |
244 |
167 |
CV |
0.0280 |
0.0186 |
0.0120 |
0.00395 |
Pooled CV |
0.0180 |
|
|
Table 12
Precision Study 4-Methoxyphenol
|
Injection |
|
Number |
10.2µg/mL |
51.0µg/mL |
102µg/mL |
204µg/mL |
|
1 |
1982 |
10178 |
21314 |
42133 |
2 |
2032 |
10059 |
20806 |
43044 |
3 |
1983 |
10270 |
21214 |
42404 |
4 |
1968 |
10307 |
20503 |
42328 |
5 |
2043 |
10153 |
20814 |
42527 |
6 |
2061 |
10470 |
20609 |
42806 |
Average |
2012 |
10240 |
20877 |
42540 |
Standard |
|
Deviation |
±38.6 |
143 |
324 |
333 |
CV |
0.0192 |
0.0140 |
0.0155 |
0.00783 |
Pooled CV |
0.0147 |
|
|
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 20 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 HP 5890 gas chromatograph was used in this study.
3.1.2. GC column capable of separating the analyte and an
internal standard from any interferences. The column used in this study was a 30 meter
DB-225 capillary column, 0.25 µ d.f., 0.32 mm I.D. An alternate column is a 60 meter DB-1
capillary column, 1.0 µ d.f., 0.32 mm I.D.
3.1.3. An electronic integrator or some other suitable method of measuring peak areas.
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. 2-Methoxyphenol, Reagent grade
3.2.3. 3-Methoxyphenol, Reagent grade
3.2.4. 4-Methoxyphenol, Reagent grade
3.2.5. Methanol, HPLC grade
3.2.6. Dimethyl formamide, Reagent grade
3.2.7. Desorbing solution is methanol with 1 µL/mL dimethyl formamide used as 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, and the front glass wool was
included in the vial with the front section.
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 each isomer of methoxyphenol.
3.4.2. At least two separate stock standards should be
made. Dilutions of the stock standards are prepared covering the concentrations in the
samples. The analytical standards used in this study ranged from 1 to 110 µg/mL of each
isomer of methoxyphenol in the desorbing solution.
3.5. Analysis
3.5.1.Gas chromatograph conditions for DB-225 capillary column.
Flow rates (mL/min) |
Temperature (°C) |
Nitrogen(makeup) |
:30 |
Injector |
:240 |
Hydrogen (carrier) |
:1.5 |
Detector |
:240 |
Air |
:450 |
Column |
:100°-1 min |
Hydrogen(detector) |
:30 |
|
5°C/min-140°C |
Injection size |
:1 µL |
|
Elution time |
:4.554, 11.455, and 12.175 min |
Chromatogram |
:(See Figure 1) |
3.5.2. Gas chromatograph conditions for DB-1capillary column.
Flow rates (mL/min) |
Temperature (°C) |
Nitrogen(makeup) |
:30 |
Injector |
:240 |
Hydrogen (carrier) |
:1.5 |
Detector |
:240 |
Air |
:450 |
Column |
:80°-0 min |
Hydrogen(detector) |
:30 |
|
10°C/min-160°C |
Injection size |
:1 µL |
|
Elution time |
:12.180, 15.328, and 15.768 min |
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. A curve with area counts versus concentration is
calculated from the calibration standards.
3.7.2. The area counts for the samples are plotted with the
calibration curve to obtain the concentration of methoxyphenol in solution.
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 |
(µg) (L) |
× |
(mg) (1000 µg) |
× |
(1000 L) (m3) |
= mg/m3 of analyte |
3.7.4. The above equations can be consolidated to form the
following formula. To calculate the mg/m3 of analyte in the sample based on a
20 liter air sample:
(µg/mL)(DV) (20 L)(DE) |
× |
(mg) (1000 µg) |
× |
(1000 L) (m3) |
= mg/m3 of analyte |
µg/mL | = | concentration of analyte in sample or standard |
DV | = | Desorption volume |
20 L | = | 20 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 chemicals.
3.8.3. Wear safety glasses, gloves and a lab coat at all times.
4. Recommendations for further study
Collection study should be performed.
Figure 1. An analytical standard of 101 µg/mL 2-methoxyphenol, 110 µg/mL 3-methoxyphenol, and 102 µg/mL
4-methoxyphenol in methanol with 1 µL/mL dimethyl formamide internal standard, analyzed using a DB-225 capillary column.
Figure 2. An analytical standard of 101 µg/mL
2-methoxyphenol,110 µg/mL 3-methoxyphenol, and 102 µg/mL 4-methoxyphenol in methanol
with 1 µL/mL dimethyl formamide internal standard, analyzed using a DB-1 capillary column.
5. References
5.1. Cummins, K., Method 32, "Phenol and Cresol",
Organic Methods Evaluation Branch, OSHA Salt Lake Technical Center, 1986.
5.2. Windholz, M., "The Merck Index", Eleventh
Edition, Merck & Co., Rahway N.J., 1989, p. 715.
5.3. Sax, N., Lewis, R., "Hawley's Condensed Chemical
Dictionary", Eleventh Edition, Van Nostrand Reinhold Co., New York, 1987, p. 620.
5.4. "Documentation of the Threshold Limit Values and
Biological Exposure Indices", Fifth Edition, American Conference of Governmental
Industrial Hygienists Inc., Cincinnati, OH, 1986, p. 367.
5.5. Weast, R.C., "Handbook of Chemistry and
Physics", 67th Edition, CRC Press Inc., Boca Raton FL, 1986, p.C244.
|