# Cresol (All Isomers) and Phenol (2546)

​CRESOL (all isomers) and PHENOL
CH3C6H4OH C6H5OH
MW: 108.14 94.11
METHOD: 2546, Issue 1
CAS: 1319-77-3 108-95-2
2546
RTECS: GO5950000 SJ3325000
EVALUATION: PARTIAL
OSHA : Table 1 NIOSH: ACGIH:
Issue 1: 15 August 1994
PROPERTIES: Table 1
SYNONYMS: o-cresol: 2-methylphenol; CAS #95-48-7; m-cresol: 3-methylphenol; CAS #108-39-4; p-cresol: 4-methylphenol; CAS
phenol: carbolic acid; hydroxybenzene SAMPLING SAMPLER:
SOLID SORBENT TUBE (XAD-7, 100 mg/50 mg)
FLOW RATE:
0.01 to 0.1 L/min
VOL-MIN: -MAX:
1 L @ 5 ppm 24 L
SHIPMENT:
routine
MEASUREMENT TECHNIQUE:
GAS CHROMATOGRAPHY, FID
ANALYTE:
cresol isomers/phenol
DESORPTION:
2 mL methanol; sonicate
INJECTION VOLUME:
1 µL (split 20:1)
SAMPLE STABILITY:
at least 1 week @ 25 °C [1]
TEMPERATURE-INJECTION: -DETECTOR: -COLUMN:
BLANKS:
2 to 10 field blanks per set
CARRIER GAS:
He, 1 mL/min
COLUMN:
Stabilwax DA fused silica capillary, 30 m, 0.32-mm ID, 0.25-mm film or equivalent
CALIBRATION:
standard solutions of analytes in methanol 20 to 800 µg per sample
ACCURACY
250 °C 300 °C 160 - 225 °C (3 °C/min)
RANGE STUDIED:
not studied
RANGE:
BIAS:
not determined
ESTIMATED LOD: 1 to 3 µg per sample
ˆ rT): not determined OVERALL PRECISION (S ACCURACY:
PRECISION (Sr):
0.028 [1]
not determined
APPLICABILITY: The working range is 0.25 to 15 ppm (1 to 60 mg/m 3) for cresols and phenol in a 20-L air sample.
INTERFERENCES: None identified. A DB-wax fused silica capillary column is an alternate column.
OTHER METHODS: This method uses a sampler similar to that of OSHA 32 [1] and replaces methods 2001 (Cresols) [2] and 3502 (Phenol) [3]. Analysis of the sample extracts can also be done by HPLC/UV [1,4].
NIOSH Manual of Analytical Methods (NMAM), Fourth Edition, 8/15/94 ​CRESOL (all isomers) and PHENOL: METHOD 2546, Issue 1, dated 15 August 1994 - Page 2 of 4 EQUIPMENT:
REAGENTS: 1. 2. 3.
4.
5. 6. 7.
Methanol, chromatographic quality. n-Hexane. Cresol (all isomers).* Dissolve 2 g o-cresol (solid), 3 g p-cresol (solid) in 4 g (4.13 mL) of m-cresol and mix. Calibration stock solution, 10.4 mg/mL. Dilute 104 mg cresol isomer mixture (1.0 mL at 20 °C) to 10 mL with n-hexane. Hydrogen, prepurified. Nitrogen, purified. Air, filtered.
See SPECIAL PRECAUTIONS.
1. Sampler: glass tube, 11 cm long, 6-mm OD, 4- mm ID;two sections of 20/40 mesh XAD-7 separated by a 2-mm portion of silanized glass wool (front = 100 mg, back = 50 mg). 2. Personal sampling pump, 0.01 to 0.1 L/min, with flexible connecting tubing. 3. Gas chromatograph, FID, integrator and column (page 2001-1). 4. Vials, glass, 2-mL, PTFE-lined crimp caps. 5. Syringe, 10-µL, readable to 0.1 µL. 6. Pipet, 1.0-mL, with pipet bulb. 7. Volumetric flasks, 10-mL. 8. Ultrasonic bath.
SPECIAL PRECAUTIONS: Cresol and phenol cause severe burns [5]. They are toxic if absorbed through skin, inhaled or ingested. All work with them should be performed in a hood.
SAMPLING: 1. 2. 3. 4.
Calibrate each personal sampling pump with a representative sampler in line. Break the ends of the sampler immediately before sampling. Attach sampler to personal sampling pump with flexible tubing. Sample at an accurately known flow rate between 0.01 and 0.1 L/min for a total sample size of 5 to 24 L. Cap the samplers with plastic (not rubber) caps and pack securely for shipment.
SAMPLE PREPARATION: 5. 6. 7.
Place the front sorbent section (together with the front glass wool plug) and back sorbent sections of the sampler tube in separate vials. Discard the other plugs. Add 2.0 mL methanol to each vial. Attach crimp cap to each vial. Ultrasonicate 30 min.
CALIBRATION AND QUALITY CONTROL: 8.
9.
Calibrate daily with at least six working standards over the range 1 to 800 µg cresol and phenol per sample. a. Add known amounts of calibration stock solution to methanol in 10-mL volumetric flasks and dilute to the mark. b. Analyze together with samples and blanks (steps 11 and 12). c. Prepare calibration graph (total peak area vs. µg analyte). Determine desorption efficiency (DE) at least once per year for each lot of sorbent used for sampling in the calibration range. Prepare three tubes at each of five concentrations plus three media blanks. a. Remove and discard back sorbent section of a media blank sampler. b. Inject a known amount of calibration stock solution directly onto front sorbent section with a microliter syringe. c. Cap the tube. Allow to stand overnight. d. Desorb (steps 5 through 7) and analyze together with working standards (steps 11 and 12). e. Prepare a graph of DE vs. µg analyte recovered. NIOSH Manual of Analytical Methods (NMAM), Fourth Edition, 8/15/94 ​CRESOL (all isomers) and PHENOL: METHOD 2546, Issue 1, dated 15 August 1994 - Page 3 of 4 10.
Analyze three quality control blind spikes and three analyst spikes to insure that the calibration graph and DE graph are in control.
MEASUREMENT: 11.
12.
Set gas chromatograph according to manufacturer's recommendations and to conditions given on page 2000-1. Inject 1-µL sample aliquot manually using solvent flush technique or with autosampler. NOTE: If peak area is above the linear range of the working standards, dilute with methanol, reanalyze, and apply the appropriate dilution factor in calculations. Measure total peak area of the two analyte peaks.
CALCULATIONS: 13.
14.
Determine the mass, µg (corrected for DE) of cresols and phenol found in the sample front (W f) and back (W b) sorbent sections, and in the average media blank front (B f) and back (B b) sorbent sections. NOTE: If W b > W f/10, report breakthrough and possible sample loss. Calculate concentration, C, of cresols in the air volume sampled, V (L):
EVALUATION OF METHOD: This is a modification of OSHA Method 32 (Phenol and Cresol) which uses the same sampling procedure [1]. Phenol and all cresol isomers were easily resolved by capillary GC using a split injection ratio of 20:1. The desorption efficiency (DE) results for all analytes were > 0.90. Analytes were stable for 30 days when refrigerated.
REFERENCES: [1] Phenol and Cresol, Occupational Safety and Health Administration, OSHA Method 32, OSHA Analytical Laboratory, 1981. [2] NIOSH Manual of Analytical Methods, 3rd ed., Vol. 2, Method 3502, U.S. Dept. of Health, Education, and Welfare, Publication #84-100 (NIOSH), 1984. [3] Ibid, Method 2001. [4] DataChem Laboratories Report, Seq. #7478-L (NIOSH, unpublished, May 8, 1992). [5] NIOSH/OSHA, Occupational Health Guidelines for Chemical Hazards, USDHHS (NIOSH), Publ. 81123 (1981). [6] Pendergrass, S.M., An Improved Method for the Sampling and Analysis of Phenol and o-, m-, and p-Cresol by Capillary GC/FID, Amer. Ind. Hyg. Assoc. J. (accepted for publication, 1994). [7] Gessner, H., Ed., Condensed Chemical Dictionary, 10th ed., Van Nostrand Reinhold, 1981.
METHOD REVISED BY: Stephanie M. Pendergrass, NIOSH/DPSE.
NIOSH Manual of Analytical Methods (NMAM), Fourth Edition, 8/15/94 ​CRESOL (all isomers) and PHENOL: METHOD 2546, Issue 1, dated 15 August 1994 - Page 4 of 4 TABLE 1. PHYSICAL PROPERTIES [6].
Compound
BP (°C) MP (°C) Density @ 20 °C
Vapor Presssure 25 °C (Pa) (mm Hg)
NIOSH REL*
o-cresol
190.95
30.9
1.047 g/mL
33
0.25
2.3 ppm
m-cresol
202.2
12.0
1.034
20
0.15
2.3 ppm
p-cresol
201.9
35.3
1.034
15
0.11
2.3 ppm
phenol
182.0
41.0
1.071 (25 °C)
47
0.35
5 ppm; C 15.6 ppm/15 min (skin)
1 ppm = 4.42 mg/m 3 @ NTP for the cresols; 1 ppm = 3.85 mg/m 3 @ NTP for phenol.
NIOSH Manual of Analytical Methods (NMAM), Fourth Edition, 8/15/94