Page:NIOSH Manual of Analytical Methods - 2018.pdf/3

 ALIPHATIC ALDEHYD ES: METHO D 2018, Issue 1, dated 15 March 2003 - page 3 of 10

SPECIAL PRECAUTIONS: Acetaldehyde is a severe eye irritant, lachrymator, mutagen, confirmed animal carcinogen, human cancer suspect agent and possible sensitizer [9]. Contact of acetaldehyde with air may cause the formation of explosive peroxides, and contact of the peroxides with heat or flam e m ay cause fires or exp losion s. Fire and exp losion m ay result from con tact of ace taldeh yde with strong oxidizers. Acetaldehyde is an extreme fire hazard; flash point = -37.8 oC (closed cup). Allow excess acetaldehyde in the glass ampule to evaporate in a fume hood. Propionaldehyde, valeraldehyde, and isovaleraldehyde are eye and skin irritants. Evidence for the potential carcinogenicity of propionaldehyde and valeraldehyde is inconclusive [9]. These three aldehydes are incompatible with strong oxidizers and are dangerous fire hazards (flash points = 17.8 oC, 12.2 oC and -1 oC, respectively). Bottles of these aldehydes should be flushed with nitrogen after use. Work with all aldehydes in a fume hood. The DNPH reagent [11] and aliphatic aldehydes are light sensitive [10]. Also, DNPH is a suspect carcinogen. Acetonitrile is toxic and is a fire hazard (flash point = 12.8 oC). SAMPLING: 1. Calibrate each pe rsona l sam pling pum p with a represe ntative sam pler in line. If desirable, attach a representative ozone scrubber to the inlet of the sam pler. How ever this method has not been evaluated with an ozone scrubber in line. 2. Open sam pler packet and remove end caps. 3. Attach sampler to the sampling pump with flexible tubing. Th e W ate rs sam pler is bi-directional and can be c onn ecte d at either en d. NOTE: If sampling is to be performed in intense sunlight, protection of the DNPH -coated silica gel bed in the sampler from intense light would be suggeste d in ord er to prevent possible photodecomposition of the DNPH reagent [11] and the aldehyde derivatives. If desirable, wrap a portion of the sampler with aluminum foil or black electrical tape. 4. Sam ple 1 to 15 L of air at 0.1 to 1.5 L/min. 5. Plac e en d ca ps o nto the sa m pler and s eal sa m pler in an en velop e. Pro tect sam ples from hea t. 6. Ship samples cold (0 to 5 oC). Ship blanks in a sep arate container.

SAMPLE PREPARATION: 7. a. Elute the aldehyde derivatives from the cartridge samplers with 10-m L qu an tities of a ce ton itrile. Collect effluent (ca. 9.5 mL) from each sampler in a separate 10-mL volumetric flask. b. Add acetonitrile to the 10-mL m ark of the volumetric flask for each sample. NOTE: Carbonyl content of acetonitrile can be determined by passing 10 mL of the solvent through a cartridge of DNPH-coated silica gel and analyzing by HPLC. Contents of aldehydes of interest should be below the respective LODs.

CALIBRATION AND QUALITY CONTRO L: 8. Ca librate daily with at leas t six wo rking standa rds over the ra nge of interest. a. Calculate the concentrations of the aldehyde-DNPH derivatives in the calibration stock solutions (about 1000 µg/mL). Calculate the equivalent concentrations of the free aldehydes in solution by multiplying the derivative concentrations by 0.197, 0.244, 0.324, and 0.324 (molecular weights of acetaldehyde, propionaldehyde, valeraldehyde and isovaleraldehyde divided by the molecular weights of the correspo nding aldehyde-DN PH d erivatives, respectively). b. Prepare a series of dilutions (working standards) from 0.01 to 10 or 20 µg/mL (ranges of equivalent concentrations of free aldehydes from values be low the detection lim its to values c orrespo nding to upper lim its of the analytical range). The working stand ards (standard solutions) are stable for more than a month when stored at 5 oC in the dark in airtight containers; however, it is suggested that fresh wo rking sta ndards be pre pared weekly. c. Trans fer 3-m L aliquots of working standa rds to 4-m L vials and analyze (steps 11, 13 and 14). d. Prepare calibration graphs, peak areas or heights vs. µg free aldehydes per sample.

NIOSH Manual of Analytical Methods (NMAM), Fourth Edition