Page:NIOSH Manual of Analytical Methods - 5525.pdf/1

 ISOCYANATES, TOTAL (MAP) Formula: R-NCO

MW: Appendix C

METHOD: 5525, Issue 1

5525

CAS: Table 1

EVALUATION: PARTIAL PROPERTIES:

OSHA: Table 1 NIOSH: Table 1 ACGIH: Table 1

RTECS: Table 1 Issue 1: 15 March 2003

Table 1

NAMES & SYNONYMS: Table 2 SAMPLING SAMPLER:

FILTER (glass fiber, impregnated); or IMPINGER; or IMPINGER + FILTER (see Table 3)

FLOW RATE: 1 to 2 L/min VOL-MIN: -MAX:

1 L @ 5 ppb 500 L

SHIPMENT:

Cold; impinger solution: vial with PTFE-lined cap; filter: wide-mouth jar with PTFE-lined cap, containing 5.0 mL MAP extraction solution

SAMPLE STABILITY:

REAGENT STABILITY:

Extracted filters: store cold and process as soon as possible; prepared samples: at least 3 months at -10° C (freezer) in the dark

MAP on filters: 6 months at -10° C (freezer) in dark; MAP solutions: irreversible precipitation occurs within a few weeks in 2 mg/mL solutions

BLANKS:

Minimum of 3 field controls, 3 field blanks per set

BULKS:

Necessary for oligomer analysis

MEASUREMENT TECHNIQUE:

HPLC, UV/FLUORESCENCE DETECTION

ANALYTE:

MAP derivatives of isocyanates

SAMPLE PREP:

Impinger samples: solid-phase extraction (SPE); filter samples: acetylate with acetic anhydride

INJECTION VOLUME:

30 µL

MOBILE PHASE: 65:35 (v/v) acetonitrile:triethylammonium phosphate/formate (100 mM in both), pH gradient 6.0 to 1.6, 1.5 mL/min. POST-COLUMN SOLUTION:

65:35 (v/v) acetonitrile- 4.4 N phosphoric acid, 0.7 mL/min.

COLUMN:

Reversed phase InertsilT M C 8, 150 x 4.6 mm, 5-µm, titanium frits in a constant temperature column oven set at 30o C.

DETECTORS:

UV @ 253 nm; fluorescence (xenon lampex: 368 nm, em: 409 nm; or deuterium lampex: 254 nm, em: 409 nm).

CALIBRATION:

MAP derivatives of monomeric isocyanates, with FL or UV for monomer; mandatory use of UV peak area for oligomer.

RANGE:

0.5 nmole NCO per species to 300 nmole total NCO per sample (e.g., 0.04 to 25 µg HDI per sample).

ACCURACY RANGE STUDIED:

Not studied

BIAS:

Not determined

OVERALL PRECISION ( Ö r T ):

Not determined

ESTIMATED LOD: 0.2 nmole NCO per species per sample (0.2 nmole NCO equals 0.017 µg HDI per sample).

ACCURACY:

Not determined

PRECISION ( þ r ):

Filters: HDI 0.05; 2,4-TDI 0.06; MDI 0.06 Impingers: not determined.

APPLICABILITY: The useful air concentration range for this method is approx. 1.4 to 840 :g/m3 NCO total isocyanate group for a 15-L air sample. This is equivalent to 0.4 ppb to 250 ppb for a diisocyanate. The method determines the air concentration of monomeric and oligomeric isocyanates. The applicability of the method depends on the correct choice of sampler for a given environment [1,2]. INTERFERENCES: Any non-isocyanate compound that reacts with MAP. Any compound that elutes at or after the monomer retention time and absorbs at 253 nm may potentially interfere with isocyanate quantification by UV. Interfering compounds that do not fluoresce using 368 nm excitation and 409 nm emission but give an interfering UV signal can be separated by altering the pH gradient. OTHER METHODS: NIOSH Method 5522 [3] is for monomer and total isocyanate. NIOSH Method 5521 [4] is for monomer and aliphatic oligomeric isocyanate. A chapter in the NIOSH Manual of Analytical Methods, a related journal article, and the references therein describe other methods and method selection criteria [1,2].

NIOSH Manual of Analytical Methods (NMAM), Fourth Edition