# Volatile Organic Compounds (Screening) (2549)

​VOLATILE ORGANIC COMPOUNDS (SCREENING)
FORMULA
see Table 1
MW: see Table 1
METHOD: 2549, Issue 1
CAS: see Table 1
EVALUATION: PARTIAL
OSHA : NIOSH: varies with compound ACGIH:
PROPERTIES:
2549
RTECS: see Table 1
Issue 1: 15 May 1996
See Table 1
SYNONYMS: VOCs; See individual compounds in Table 1
SAMPLING SAMPLER:
THERMAL DESORPTION TUBE (multi-bed sorbent tubes containing graphitized carbons and carbon molecular sieve sorbents [See Appendix])
FLOW RATE:
0.01 to 0.05 L/min
VOL-MIN: -MAX:
1L 6L
SHIPMENT:
MEASUREMENT TECHNIQUE:
THERMAL DESORPTION, GAS CHROMATOGRAPHY, MASS SPECTROMETRY
ANALYTE:
See Table 1
DESORPTION:
Thermal desorption
INJECTION VOLUME:
Defined by desorption split flows (See Appendix)
Ambient in storage containers
SAMPLE STABILITY:
Compound dependent (store @ -10 C)
BLANKS:
1 to 3 per set
TEMPERATURE-DESORPTION: 300 C for 10 min. -DETECTOR (MS): 280 C -COLUMN: 35 C for 4 min; 8 C/min to 150 C, 15 C/min to 300 C CARRIER GAS:
Helium
COLUMN:
30 meter DB-1, 0.25-mm ID, 1.0-µm film, or equivalent
CALIBRATION:
Identification based on mass spectra interpretation and computerized library searches.
RANGE:
not applicable
ESTIMATED LOD:
100 ng per tube or less
PRECISION ( r):
not applicable
ACCURACY
RANGE STUDIED:
not applicable
BIAS:
not applicable
OVERALL PRECISION ( ACCURACY:
rT
not applicable not applicable
APPLICABILITY:This method has been used for the characterization of environments containing mixtures of volatile organic compounds (See Table 1). The sampling has been conducted using multi-bed thermal desorption tubes. The analysis procedure has been able to identify a wide range of organic compounds, based on operator expertise and library searching. INTERFERENCES:Compounds which coelute on the chromatographic column may present an interference in the identification of each compound. By appropriate use of background subtraction, the mass spectrometrist may be able to obtain more representative spectra of each compound and provide a tentative identity (See Table 1). OTHER METHODS: Other methods have been published for the determination of specific compounds in air by thermal desorption/gas chromatography [1-3]. One of the primary differences in these methods is the sorbents used in the thermal desorption tubes.
NIOSH Manual of Analytical Methods (NMAM), Fourth Edition, 5/15/96 ​VOLATILE ORGANIC COMPOUNDS (SCREENING): METHOD 2549, Issue 1, dated 15 May 1996 - Page 2 of 8
REAGENTS:
EQUIPMENT:
1. Air, dry 2. Helium, high purity 3. Organic compounds of interest for mass spectra verification (See Table 1).* 4. Solvents for preparing spiking solutions: carbon disulfide (low benzene chromatographic grade), methanol, etc.(99+% purity)
1. Sampler: Thermal sampling tube, ¼” s.s. tube, multi-bed sorbents capable of trapping organic compounds in the C3-C16 range. Exact sampler configuration depends on thermal desorber system used. See Figure 1 for example. 2. Personal sampling pump, 0.01 to 0.05 L/min, with flexible tubing. 3. Shipping containers for thermal desorber sampling tubes. 4. Instrumentation: thermal desorption system, focusing capability, desorption temperature appropriate to sorbents in tube (~300 C), and interfaced directly to a GC-MS system. 5. Gas chromatograph with injector fitted with 1/4" column adapter, 1/4" Swagelok nuts and Teflon ferrules (or equivalent). 6. Syringes: 1-µL, 10-µL (liquid); 100-µL, 500-µL (gas tight) 7. Volumetric Flasks, 10-mL. 8. Gas bulb, 2 L
SPECIAL PRECAUTIONS: Some solvents are flammable and should be handled with caution in a fume hood. Precautions should be taken to avoid inhalation of the vapors from solvents as well. Skin contact should be avoided. SAMPLING: NOTE:
1. 2.
3.
4.
5. 6.
Prior to field use, clean all thermal desorption tubes thoroughly by heating at or above the intended tube desorption temperature for 1-2 hours with carrier gas flowing at a rate of at least 50 mL/min. Always store tubes with long-term storage caps attached, or in containers that prevent contamination. Identify each tube uniquely with a permanent number on either the tube or tube container. Under no circumstances should tape or labels be applied directly to the thermal desorption tubes. Calibrate each personal sampling pump with a representative sampler in line. Remove the caps of the sampler immediately before sampling. Attach sampler to personal sampling pump with flexible tubing. NOTE: With a multi-bed sorbent tube, it is extremely important to sample in the correct direction, from least to maximum strength sorbent. For general screening, sample at 0.01 to 0.05 L/min for a maximum sample volume of 6 L. Replace caps immediately after sampling. Keep field blanks capped at all times. Tubes can act as diffusive samplers if left uncapped in a contaminated environment. Collect a "humidity test" sample to determine if the thermal adsorption tubes have a high water background. NOTE: At higher sample volumes, additional analyte and water (from humidity) may be collected on the sampling tube. At sufficiently high levels of analyte or water in the sample, the mass spectrometer may malfunction during analysis resulting in loss of data for a given sample. Collect a "control" sample. For indoor air samples this could be either an outside sample at the same location or an indoor sample taken in a non-complaint area. Ship in sample storage containers at ambient temperature. Store at -10 C.
SAMPLE PREPARATION: 7.
Allow samples to equilibrate to room temperature prior to analysis. Remove each sampler from its storage container.
NIOSH Manual of Analytical Methods (NMAM), Fourth Edition, 5/15/96 ​VOLATILE ORGANIC COMPOUNDS (SCREENING): METHOD 2549, Issue 1, dated 15 May 1996 - Page 3 of 8
8. 9.
Analyze "humidity test" sampler first to determine if humidity was high during sampling (step 10). If high humidity, dry purge the tubes with purified helium at 50 to 100 mL/min for a maximum of 3 L at ambient temperature prior to analysis. . 10. Place the sampler into the thermal desorber. Desorb in reverse direction to sampling flow.
CALIBRATION AND QUALITY CONTROL: 11. Tune the mass spectrometer according to manufacturer’s directions to calibrate. 12. Make at least one blank run prior to analyzing any field samples to ensure that the TD-GC-MS system produces a clean chromatographic background. Also make a blank run after analysis of heavily concentrated samples to prevent any carryover in the system. If carryover is observed, make additional blank runs until the contamination is flushed from the thermal desorber system. 13. Maintain a log of thermal desorber tube use to record the number of times used and compounds found. If unexpected analytes are found in samples, the log can be checked to verify if the tube may have been exposed to these analytes during a previous sampling use. 14. Run spiked samples along with the screening samples to confirm the compounds of interest. To prepare spiked samples, use the procedure outlined in the Appendix . MEASUREMENT: 15. See Appendix for conditions. MS scan range should cover the ions of interest, typically from 20 to 300 atomic mass units (amu). Mass spectra can either be identified by library searching or by manual interpretation (see Table 1). In all cases, library matches should also be checked for accurate identification and verified with standard spikes if necessary. EVALUATION OF METHOD: The method has been used for a number of field screening evaluations to detect volatile organic compounds. Estimate of the limit of detection for the method is based on the analysis of spiked samples for a number of different types of organic compounds. For the compounds studied, reliable mass spectra were collected at a level of 100 ng per compound or less. In situations where high levels of humidity may be present on the sample, some of the polar volatile compounds may not be efficiently collected on the internal trap of the thermal desorber. In these situations, purging of the samples with 3 L of helium at 100 mL/min removed the excess water and did not appreciably affect the recovery of the analytes on the sample. REFERENCES: [1] [2]
[3] [4]
Health and Safety Executive [1992]. MDHS 72 - Volatile organic compounds in air. Methods for the determination of hazardous substances. HMSO: London: ISBN 0-11-885692-8. McCaffrey CA, MacLachlan J, Brookes BI [1994]. Adsorbent tube evaluation for the preconcentration of volatile organic compounds in air for analysis by gas chromatography-mass spectrometry. Analyst 119:897-902. Bianchi AP, Varney MS [1992]. Sampling and analysis of volatile organic compounds in estuarine air by gas chromatography and mass spectrometry. J. Chromatogr. 643:11-23. EPA [1984]. Environmental Protection Agency Air Toxics Method T01. Rev. 1.0 (April, 1984): Method for the determination of volatile organic compounds in ambient air using Tenax(R) adsorption and gas chromatography/mass spectrometry (GC/MS), Section 13.
METHOD WRITTEN BY: Ardith A. Grote and Eugene R. Kennedy, Ph.D., NIOSH, DPSE
NIOSH Manual of Analytical Methods (NMAM), Fourth Edition, 5/15/96 ​VOLATILE ORGANIC COMPOUNDS (SCREENING): METHOD 2549, Issue 1, dated 15 May 1996 - Page 4 of 8
TABLE 1. COMMON VOLATILE ORGANIC COMPOUNDS WITH MASS SPECTRAL DATA Compound /Synonyms
CAS# RTECS
Empirical Formula
MWa
BPb ( C)
VPc @ 25 C mm Hg kPa
Characteristic Ions, m/z
80.1
95.2
78*
Aromatic Hydrocarbons Benzene /benzol
71-43-2 CY1400000
C6H6
78.11
Xylene /dimethyl benzene
1330-20-7 ZE2100000
C8H10
106.7
12.7
91, 106*, 105
o-xylene
144.4
6.7
0.9
m-xylene
139.1
8.4
1.1
p-xylene
138.4
8.8
1.2
Toluene /toluol
108-88-3 XS5250000
C7H8
92.14
110.6
28.4
3.8
91, 92*
Aliphatic Hydrocarbons n-Pentane
109-66-0 RZ9450000
C5H12
72.15
36.1
512.5
68.3
43, 72*, 57
n-Hexane /hexyl-hydride
110-54-3 MN9275000
C6H14
86.18
68.7
151.3
20.2
57, 43, 86*, 41
n-Heptane
142-82-5 MI7700000
C7H16
100.21
98.4
45.8
6.1
43, 71, 57, 100*,41
n-Octane
111-65-9 RG8400000
C8H18
114.23
125.7
14.0
1.9
43, 85, 114*, 57
n-Decane /decyl hydride
124-18-5 HD6500000
C10H22
142.29
174
1.4
0.2
43, 57, 71, 41, 142*
Acetone /2-propanone
67-64-1 AL3150000
C3H6O
58.08
56
266
35.5
43, 58*
2-Butanone /methyl ethyl ketone
78-93-3 EL6475000
C4H8O
72.11
79.6
100
13
43, 72*
Methyl isobutyl ketone /MIBK, hexone
108-10-1 SA9275000
C6H12O
100.16
117
15
2
43, 100*, 58
Cyclohexanone /cyclohexyl ketone
108-94-1 GW1050000
C6H10O
98.15
155
2
0.3
55, 42, 98*, 69
Methanol /methyl alcohol
67-56-1 PC1400000
CH3OH
32.04
64.5
115
15.3
31, 29, 32*
Ethanol /ethyl alcohol
64-17-5 KQ6300000
C2H5OH
46.07
78.5
42
5.6
31, 45, 46*
Isopropanol /1-methyl ethanol
67-63-0 NT8050000
C3H7OH
60.09
82.5
33
4.4
45, 59, 43
Butanol /butyl alcohol
71-36-3 EO1400000
C4H9OH
74.12
117
4.2
0.56
56, 31, 41, 43
Ketones
Alcohols
NIOSH Manual of Analytical Methods (NMAM), Fourth Edition, 5/15/96 ​VOLATILE ORGANIC COMPOUNDS (SCREENING): METHOD 2549, Issue 1, dated 15 May 1996 - Page 5 of 8 CAS# RTECS
Empirical Formula
MWa
BPb ( C)
VPc @ 25 C
Butyl cellosolve /2-butoxyethanol
111-76-2 KJ8575000
C6H14 O2
118.17
171
0.8
0.11
57, 41, 45, 75, 87
Diethylene glycol ethyl ether /Carbitol
111-90-0 KK8750000
C6H14O3
134.17
202
0.08
0.01
45, 59, 72, 73, 75, 104
Phenol /hydroxybenzene
108-95-2 SJ3325000
C6H5OH
94.11
182
47
0.35
94*, 65, 66, 39
Cresol
1319-77-3 GO5950000
C7H7OH
108.14
2-methylphenol
95-48-7
190.9
1.9
0.25
3-methylphenol
108-39-4
202.2
1.0
0.15
4-methylphenol
106-44-5
201.9
0.8
0.11
Compound /Synonyms
mm Hg kPa
Characteristic Ions, m/z
Glycol Ethers
Phenolics
108*, 107, 77, 79
Chlorinated Hydrocarbons Methylene chloride /dichloromethane
75-09-2 PA8050000
CH2Cl2
84.94
40
349
47
86*, 84, 49, 51
1,1,1-Trichloroethane /methyl chloroform
71-55-6 KJ2975000
CCl3CH3
133.42
75
100
13.5
97, 99, 117, 119
Perchloroethylene /hexachloroethane
127-18-4 KX3850000
CCl3CCl3
236.74
187 (subl)
0.2
<0.1
164*, 166, 168, 129, 131, 133, 94, 96
C6H4Cl2
147.0
o-,pDichlorobenzenes
146*, 148, 111, 113, 75
/1,2-dichlorobenzene
95-50-1 CZ4500000
172-9
1.2
0.2
/1,4dichlorobenzene
106-46-7 CZ4550000
173.7
1.7
0.2
1,1,2-Trichloro-1,2,2trifluoroethane /Freon 113
76-13-1 KJ4000000
CCl2FCClF2
187.38
47.6
384
38
d-Limonene
5989-27-5 OS8100000
C10H16
136.23
176
1.2
68, 67, 93, 121, 136*
Turpentine (Pinenes)
8006-64-2
C10H16
136.23
156 to 170
4@ 20
93, 121, 136*, 91
101, 103, 151, 153, 85, 87
Terpenes
-pinene
80-56-8
156
-pinene
127-91-3
165
Aldehydes Hexanal /caproaldehyde
66-25-1 MN7175000
C6H12O
100.16
131
10
NIOSH Manual of Analytical Methods (NMAM), Fourth Edition, 5/15/96
1.3
44, 56, 72, 82, 41 ​VOLATILE ORGANIC COMPOUNDS (SCREENING): METHOD 2549, Issue 1, dated 15 May 1996 - Page 6 of 8 Compound /Synonyms
CAS# RTECS
Empirical Formula
MWa
BPb ( C)
VPc @ 25 C
Benzaldehyde /benzoic aldehyde
100-52-7 CU4375000
C7H12O
106.12
179
1.0
0.1
77, 105, 106*, 51
Nonanal /pelargonic aldehyde
124-19-6 RA5700000
C9H18O
142.24
93
23
3
43, 44, 57, 98, 114
Ethyl acetate /acetic ether
141-78-6 AH5425000
C4H8O2
88.1
77
73
9.7
43, 88*, 61, 70, 73, 45
Butyl acetate /acetic acid butyl ester
123-86-4 AF7350000
C6H12O2
116.16
126
10
1.3
43, 56, 73, 61
Amyl acetate /banana oil
628-63-7 AJ1925000
C7H14O2
130.18
149
4
0.5
43, 70, 55, 61
556-67-2 GZ4397000
C8H24O4Si4
296.62
175
mm Hg kPa
Characteristic Ions, m/z
Acetates
Other Octamethylcyclotetrasiloxane
281, 282, 283
a
Molecular Weight Boiling Point c Vapor Pressure
b
APPENDIX Multi-bed sorbent tubes: Other sorbent combinations and instrumentation/conditions shown to be equivalent may be substituted for those listed below. In particular, if the compounds of interest are known, specific sorbents and conditions can be chosen that work best for that particular compound(s). The tubes that have been used in NIOSH studies with the Perkin Elmer ATD system are ¼” stainless steel tubes, and are shown in the diagram below:
NIOSH Manual of Analytical Methods (NMAM), Fourth Edition, 5/15/96 ​VOLATILE ORGANIC COMPOUNDS (SCREENING): METHOD 2549, Issue 1, dated 15 May 1996 - Page 7 of 8
Figure 1 Carbopack™ and Carboxen™ adsorbents are available from Supelco, Inc.
Preparation of spiked samples: Spiked tubes can be prepared from either liquid or gas bulb standards. Liquid standards: Prepare stock solutions by adding known amounts of analytes to 10-mL volumetric flasks containing high purity solvent (carbon disulfide, methanol, toluene). Solvents are chosen based on solubility for the analytes of interest and ability to be separated from the analytes when chromatographed. Highly volatile compounds should be dissolved in a less volatile solvent. For most compounds, carbon disulfide is a good general purpose solvent, although this will interfere with early eluting compounds. Gas bulb standards: Inject known amounts of organic analytes of interest into a gas bulb of known volume filled with clean air [4]. Prior to closing the bulb, place a magnetic stirrer and several glass beads are placed in the bulb to assist in agitation after introduction of the analytes. After injection of all of the analytes of interest into the bulb, warm the bulb to 50 C and place it on a magnetic stirring plate and stir for several minutes to ensure complete vaporization of the analytes. After the bulb has been stirred and cooled to room temperature, remove aliquots from the bulb with a gas syringe and inject into a sample tube as described below. Tube spiking: Fit a GC injector with a ¼" column adapter. Maintain the injector at 120 C to assist in vaporization of the injected sample. Attach cleaned thermal desorption tubes to injector with ¼” Swagelok nuts and Teflon ferrules, and adjust helium flow though the injector to 50 mL/min. Attach the sampling tube so that flow direction is the same as for sampling. Take an aliquot of standard solution (gas standards 100 to 500 µL; liquid standards, 0.1 to 2 µL) and inject into the GC injector. Allow to equilibrate for 10 minutes. Remove tube and analyze by thermal desorption using the same conditions as for field samples. Instrumentation:Actual media, instrumentation, and conditions used for general screening of unknown environments are as follows: Perkin-Elmer ATD 400 (automated thermal desorption system) interfaced directly to a Hewlett-Packard 5980 gas chromatograph/HP5970 mass selective detector and data system.
NIOSH Manual of Analytical Methods (NMAM), Fourth Edition, 5/15/96 ​VOLATILE ORGANIC COMPOUNDS (SCREENING): METHOD 2549, Issue 1, dated 15 May 1996 - Page 8 of 8
ATD conditions: Tube desorption temperature: 300 C Tube desorption time: 10 min. Valve/transfer line temperatures: 150 C Focusing trap: Carbopack B/Carboxen 1000, 60/80 mesh, held at 27 C during tube desorption Focusing trap desorption temperature: 300 C Desorption flow: 50-60 mL/min. Inlet split: off Outlet split: 20 mL/min. Helium: 10 PSI GC conditions: DB-1 fused silica capillary column, 30 meter, 1-µm film thickness, 0.25-mm I.D. Temperature program: Initial 35 C for 4 minutes, ramp to 100 C at 8 /min., then ramp to 300 C at 15 /min, hold 1-5 minutes. Run time: 27 min. MSD conditions: Transfer line: 280 C Scan 20-300 amus, EI mode EMV: set at tuning value Solvent delay: 0 min. for field samples; if a solvent-spiked tube is analyzed, a solvent delay may be necessary to prevent MS shutdown caused by excessive pressure.
NIOSH Manual of Analytical Methods (NMAM), Fourth Edition, 5/15/96