Diesel Particulate Matter (as Elemental Carbon) (5040)
DIESEL PARTICULATE MATTER (as Elemental Carbon) C
AW: 12.01
METHOD: 5040: Issue 3
CAS: none
RTECS: none
EVALUATION: FULL
OSHA : no PEL NIOSH: no REL ACGIH: 20 :g/m as elemental carbon (proposed [1])
PROPERTIES:
5040
Issue 1: 15 May 1996 Issue 3: 15 March 2003 Issue :10 March 2016 nonvolatile solid
3
SYNONYMS (related terms): diesel particulate matter, diesel exhaust, diesel soot, diesel emissions
SAMPLING
MEASUREMENT
SAMPLER:
FILTER: quartz-fiber, 37-mm; sizeselective sampler may be required [2].
TECHNIQUE:
Thermal-optical analysis; flame ionization detector (FID)
FLOW RATE:
2 to 4 L/min (typical)
ANALYTE:
VOL-MIN: -MAX:
142 L @ 40 :g/m3 19 m3 (for filter load of ~ 90 :g/cm2 )
Elemental carbon (EC). Total carbon is determined, but an EC exposure marker was proposed. See [2] for details.
SHIPMENT:
Routine
FILTER PUNCH SIZE:
1.5 cm2 (or other [2])
SAMPLE STABILITY:
Stable
CALIBRATION:
Methane injection
BLANKS:
2 to 10 field blanks per set
RANGE:
1 to 105 :g per filter portion (See also [2].)
ACCURACY RANGE STUDIED:
23 to 240 :g/m3 (See also ref. [2].)
BIAS:
None (See also ref. [2].)
OVERALL PRECISION ( Ö r T ):
0.085 at 23 :g/m3 (See also ref. [2].)
ACCURACY:
± 16.7% at 23 :g/m3 (See also ref. [2].)
ESTIMATED LOD: 0.3 :g per filter portion PRECISION ( þ r ):
0.19 @ 1 :g C, 0.01 @ 10 to 72 :g C
APPLICABILITY: The working range is approximately 6 to 630 :g/m3 , with an LOD of ~ 2 :g/m3 for a 960-L air sample collected on a 37-mm filter with a 1.5 cm2 punch from the sample filter. If a lower LOD is desired, a larger sample volume and/or 25-mm filter may be used (e.g., a 1920-L sample on 25-mm filter gives an LOD of 0.4 :g/m3 ). The split between organic carbon (OC) and EC may be inaccurate if the sample transmittance is too low. The EC loading at which this occurs depends on laser intensity. In general, the OC-EC split may be inaccurate when EC loadings are above 20 :g/cm2 . High loadings can give low (and variable) EC results because the transmittance remains low and relatively constant until some of the EC is oxidized. The split should be reassigned (prior to EC peak) in such cases [3]. An upper EC limit of 800 :g/m3 (90 :g/cm2 ) can be determined.
INTERFERENCES: Total carbon (as OC and EC) is determined by the method, but EC was recommended as a measure of workplace exposure because OC interferences may be present [2, 3]. Cigarette smoke and carbonates ordinarily do not interfere in the EC determination. Less than 1% of the carbon in cigarette smoke is elemental. If heavy loadings of carbonate are anticipated, a size-selective sampler (impactor and/or cyclone) should be used [2]. For measurement of diesel-source EC in coal mines, a cyclone and impactor with a submicrometer cutpoint are required to minimize collection of coal dust. A cyclone and/or impactor may be necessary in other workplaces if EC-containing dusts are present.
OTHER METHODS: Other methods for determination of EC and OC have been employed, but these are not equivalent to the method described herein. Information on other methods is summarized elsewhere [2].
NIOSH Manual of Analytical Methods (NMAM), Fourth Edition ELEMENTAL CARBON (DIESEL PARTICULATE): METHOD 5040, Issue 3, dated 15 March 2003 - Page 2 of 5 REAGENTS:
EQUIPMENT:
1. A qu eo us so lu tio ns of re ag en t g ra de (99+ % ) sucrose, 0.1 to 3 mg C per m L solution. Ensure filter spike loading range brackets that of samples. 2. Ultra pure H 20, Type I, or equiva lent. 3. UHP helium (99.999%), scrubber also required for removal of oxygen. 4. Hydrogen, purified (99.995%), cylinder or hydrogen generator source. 5. Ultra Zero air (low hydrocarbon). 6. 10% oxygen in helium balance, both gases UHP, certified mix. 7. 5% m ethane in helium balance, both gases UHP, certified mix.
1. Sam pler: Quartz-fiber filter, precleaned (in low temperature asher 2 to 3 h, or muffle furnace for 1 to 2 h at ~ 800 °C), 37-mm , in a 3-piece cassette with filter support (stainless steel screen, cellulose pad, or a second quartz filter). Altern ative sam plers m ay be requ ired in dusty environments. See ref. [2] for details. NOT E 1: High purity, high efficiency, binderfree quartz-fiber filters must be used (e.g., Pall Gelman Sciences Pallflex Tissue qua rtz 250 0Q AT -UP . Precleaned filters are available from several laboratories. Filters also can be p urchas ed a nd c leaned in-hou se. Filte rs should be cleaned in a m uffle furnace operated at 800-900 oC for 12 ho urs. Che ck (ana lyze) filters to ens ure rem oval of OC conta m inants. A shorter cleaning period may be effective. O C res ults im m ediate ly after clean ing sh ould be below 0.1 µg/cm 2. OC vap ors readily adsorb onto clean filters. Even when stored in closed containers, OC loadings may range from 0.5 µg/cm 2 after several weeks. NOT E 2: Cellulose supports give higher O C blanks than screen s an d qu artz filters. Bottom quartz filters can be used to correc t for adsorbed vap or; see ref. [2]. 2. Personal sampling pump with flexible tubing. 3. Th erm al-optical analyzer; se e ref. [2]. 4. Metal punch for removal of 1.5 cm 2 rectangular portion of filter. NOTE: A sm aller portion (e.g., taken with cork borer) may be used, but the area must be large enough to accomm odate the entire laser beam (i.e., be am should pass through the sample, not around it). The area of the portion must be accurately k nown , and the sam ple must be carefully positioned (the filter transmittance will decrease dram atic ally when the sam ple is properly aligned). A filter portion $0.5 cm 2 with diameter or width # 1 cm is recomm ended. 5. Syringe, 10-:L. 6. Alum inum foil. 7. Needle (for lifting filter punch portion). 8. Forceps 9. Volumetric flasks, Class A. 10. Analytical balance.
NIOSH Manual of Analytical Methods (NMAM), Fourth Edition ELEMENTAL CARBON (DIESEL PARTICULATE): METHOD 5040, Issue 3, dated 15 March 2003 - Page 3 of 5
SPECIAL PRECAUTIONS: Hydrogen is a flammable gas. Users must be familiar with the proper use of flammable and nonflammable gases, cylinders, and regulators. According to the instrument manufacturer, the instrument is a Class I Laser Product. This designation means there is no laser radiation exposure during normal operation. Weakly scattered laser light is visible during operation, but does not pose a hazard to the user. The internal laser source is a Class IIIb product, which poses a possible hazard to the eye if viewed directly or from a mirror-like surface (i.e., specular reflections). Class IIIb lasers normally do not produce a hazardous diffuse reflection. Repairs to the optical system, and other repairs requiring removal of the instrument housing, should be performed only by a qualified service technician.
SAMPLING: 1. Calibrate each personal sampling pump with a representative sampler in line. NOTE: Both open- an d closed-faced cassettes have been used. Both configurations generally give even deposits. At higher flow rates (e.g., 4 L/m in), small spots occasionally have been observed in the center of the filters when closed-faced cassettes are used. This material likely consisted of impacted diesel agglomerates and/or non-diesel particulate matter. EC results for multiple portions of the filters were in good agreement, so the spots had little analytical impact. Other samplers also can be used (see ref. [2]) provided an even deposit of diesel particulate results. An even deposit is necessary because the sample portion analyzed must be representative of the entire deposit. If the deposit is not homogeneous, the entire sample must be analyzed. An impactor/cyclone may be needed in some cases. [2] 2. Attach sampler outlet to personal sampling pump with flexible tubing. 3. Sample at an accurately known flow rate. Typical rates are 2-4 L/min (note: Lower flows (e.g., 1 L/min) have been used in mines to prevent overloading). 4. After sampling, replace top piece of cassette, if removed, and pack securely for shipment to laboratory. NOTE: Diesel particulate samples from occupational settings generally do not require refrigerated shipment unless there is potential for exposure to elevated temperatures (that is, well above collection temperature). Filter samples normally are stable under laboratory conditions. Some OC loss may occur over time if samples contain O C from other sources (for example, cigarette smoke). Sorption of O C vapor after sample collection has not occurred, even with samples having high (e.g ., 80% ) EC content.
SAMPLE PREPARATION: 5. Place sample filter on a freshly cleaned aluminum foil surface. Isopropyl alcohol or acetone can be used to clean the foil. Allow residual solvent to vaporize from the surface prior to use. Punch out a representative portion of the filter. Take care not to disturb deposited material and avoid hand contact with sample. A needle inserted at an angle is useful for removal of the filter portion from the punch body. Newer instruments have an externally mounted bracket to support the quartz sample holder while the previous sample is removed and a new one is loaded. Through a hole in the side of the standard punch, a needle can be used to push the filter portion from the punch onto the sample holder. Alternative approaches also can be used, depending on the user’s preference, as long as contamination is avoided.
CALIBRATION AND QUALITY CONTRO L: 6. Analyze at least one replicate sample. For sets of up to 50 samples, replicate 10% of the samples. For sets over 50 samples, replicate 5% of the samples. If a filter deposit appears uneven (this should not be the case if the cassette is sealed properly), take a second portion (step 5) for analysis to check evenness of deposition. NOTE: Precision of replicate analyses of a filter is usually better than 5% (1 to 3% is typical).
NIOSH Manual of Analytical Methods (NMAM), Fourth Edition ELEMENTAL CARBON (DIESEL PARTICULATE): METHOD 5040, Issue 3, dated 15 March 2003 - Page 4 of 5 7. Analyze three quality control blind spikes and three analyst spikes to ensure that instrument calibration is in control. Prepare spike as follows: a. W ith 10-:L (or other) syringe, apply an aliquot of OC standard solution directly to filter portion taken (step 5) from a precleaned filter. For best results, the precleaned filter punch should be cleaned aga in in the s am ple oven p rior to applica tion of the aliquot. NOTE: W ith sm all aliquots (e.g., # 10 :L), disperse standard solution over one end of filter portion to ensure standard is in laser beam. To prevent possible solution loss to surface, hold the portion off the surface. Larger volumes can easily penetrate to the underside of the filter portion. b. Allow wate r to eva pora te and an alyze spikes with sa m ples and blank s (steps 9 and 10 ). NOTE: A pronounced decrease in filter transmittance during the first temperature step of the analysis indicates water loss. Allow portions to dry longer if this occurs. Spiked punches also can be dried in the oven, if desired. For quick drying, the ‘clean oven’ comm and on the menu can be selected and canceled after about 4 seconds. The time allowed may depend on instrument, but oven temperatures should be below 100 °C to avoid boiling the solution. This approach is con venient and prevents p otential adsorption of organic vapors in laboratory air. 8. De term ine instrum ent blank (results of ana lysis with fre shly clea ned filter portion ) for each sam ple se t.
MEASUREMENT: 9. Adjust analyzer settings according to manufacturer's recomm endations (see instrument operation manual and background information in ref. [2]). Place sample portion into sample oven. NOTE: F orm s of carbon that are difficult to oxidize (e.g., graphite) may require a longer period and higher temperature during the oxidative mode to ensu re tha t all EC is removed (the EC peak should never m erge with the calibra tion pe ak). Adju st time and tem pera ture a cco rdingly. A m axim um tem pera ture a bove 94 0 °C sho uld no t be required. 10. Determine EC (and OC ) m ass , :g. Analyzer results are reported in units :g/cm 2 of C. The reported values are normally based on a sample portion of about 1.5 cm 2, which is the area of the standard punch provided by the manufacturer. If the portion area used differs from the value entered in the ocecpar.txt file, m ultiply the result by 1.5 (or value in ocecpar.txt file) and divide the product by the actual area analyze d to obtain the are a-correcte d re sult (i.e., reported re sult x 1.5/po rtion area = correcte d re sult in
- g/cm 2). This is m ost easily done in the data spreadsheet. Alternatively, the correct results will be obtained
with the data c alculation pro gram if the portion area is entered in the param ete r file (oc ecpar.txt), but th is approac h is cum bersom e when punche s of different areas are used because correct results will not be obta ined for all pu nch sizes.
CALCULATIONS: 11. Mu ltiply the repo rted (o r area-corrected ) EC resu lt (:g/cm 2 ) by filter deposit area, cm 2, (typically 8.5 cm 2 for a 3 7-m m filter) to ca lculate total m ass , :g, of EC on each filter samp le (W EC). Do the same for the blanks an d calculate the m ass foun d in the average field blank (W b). The m ass of OC is calculated similarly, but the mean O C field blank m ay underestimate the amount of OC contributed by adsorbed vapor. A quartz filter placed beneath the sample filter can provide a better estimate of the adsorbed OC . [2] 12. Calculate the EC concen tration (C EC) in the air volume sam pled, V (L):
NIOSH Manual of Analytical Methods (NMAM), Fourth Edition ELEMENTAL CARBON (DIESEL PARTICULATE): METHOD 5040, Issue 3, dated 15 March 2003 - Page 5 of 5 EVALUATION OF METHOD: Deta ils on the evaluation of this method are provided in a chapter of this NMAM Supplement. [2] The chapter includes a summ ary of interlaboratory comparison work conducted since the initial publication of the method. Background information and guidance on m ethod use, including sam pling requiremen ts, also are provided. In general industry, 37-mm cassettes are no rm ally suitable for air s am pling, but there are ex cep tions. A cyclone in series with an impactor having a submicrometer cutpoint must be used in coal mines, and the Mine Safety and Health Administration (MSHA) has recomm ended use of a cyclone-impactor sampler in metal and nonmetal m ines. [5 ] The im pacto r is c om m ercially available [6]. A size-selective sampler (either impactor and/or cyclone) also may be required in other dusty environments [2], particularly if the dust is carbonaceous. If a sample contains carbonate, the carbonate carbon (CC) will be quantified as OC. A carbonate-subtracted result can be obta ined through acidificatio n of the sam ple portion or through separate integration of the carbon ate peak [2] (note: Trona and other compounds containing sodium can etch the quartz oven wall at elevated temperatures. Avoid spillage of these materials in the sample oven.) These procedures are described in a Chap ter of th is Supplem ent. [2] The thermal-optical method is applicable to nonvolatile carbon species (i.e., particulate OC, CC and EC). The method is not appropriate for volatile or semivolatiles, which require sorben ts for efficient collection.
REFERENCES: [1] AC GIH [2001]. Cincinnati, O H: Am erican C onference of Environm ental Industrial Hygienists. Diesel Exhaust (Particulate and Particulate Adsorbed Com ponents), Draft TLV-TW A Docum ent, 2001. NOTE: Recently, diesel exhaust has been taken off the ACGIH Notice of Intended Changes list. See referenc e [2]. [2] NIOSH [2003]. Manual of Analytical Methods (NMAM). O’Connor PF, Schlecht, PC, Monitoring of Diesel Particulate Exh aus t in the W ork place, Chap ter Q, Third Su pplem ent to NM AM , 4 th Edition, NIOSH, Cinc innati, OH . DH HS (NIO SH ) Publication No. 2003-15 4. [3] Birch, ME, C ary, RA [1996]. Elemental Carbon-based Method for Monitoring Occupational Exposures to Pa rticulate D iesel Exhaust A erosol Sci T echnol 25:221-241. [4] Birch, ME [1998]. Analysis of carb ona ceo us a eros ols: interlaboratory com parison, A nalyst, 123:851-857. [5] Mine Safety and Health Adm inistration (MSH A) [20 01]. D epa rtm ent o f Labor, 30 CFR Part 57, Diesel Particulate Matter Exposure of Underground Metal and Nonm etal Miners; Final Rule, Federal Register Vol. 66, No. 13, January 19. [6] SK C, E ight Sixty Three V alley View Road, E ighty Fo ur, PA 153 30.
METHOD WRITTEN BY: M. Eileen Birch, Ph.D., NIOSH/DART
NIOSH Manual of Analytical Methods (NMAM), Fourth Edition