National Institute for Occupational Safety and Health

Name: NIOSH Manual of Analytical Methods — Isocyanates, Total (MAP) (5525)
Author: National Institute for Occupational Safety and Health

NIOSH Manual of Analytical Methods… (1994)

Summary

“NIOSH Manual of Analytical Methods — Isocyanates, Total (MAP) (5525)”, published in 1994, is a work by National Institute for Occupational Safety and Health. It explores elements such as isocyanate, filter and impinger.

Quotes from NIOSH Manual of Analytical Methods… (National Institute for Occupational Safety and Health)

National Institute for Occupational Safety and Health, NIOSH Manual of Analytical Methods… (1994)

“ Frequently, numerous isocyanate species elute as an envelope of poorly res olved peaks. In this case, rather than attempting to integrate peaks individually, the entire chromatogram is integrated over the area o f interest. Because the fluorescence baseline is not disturbed by the gradient and the fluorescence detector is selective for MAP-derivatized compounds, the sample fluorescence chromatogram can be very useful for determ ining when to begin and end integration of peaks in the UV chromatogram. ”

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National Institute for Occupational Safety and Health, NIOSH Manual of Analytical Methods… (1994)

“ Artifacts derived from MAP are present in the chromatogram of MAP-coated filter sam ples. Although the levels are low, these impurities dictate the method LOD when they coelute with an analyte. The level of artifacts observed is not correlated well with storage time. Room temperature storage results in greate r artifact levels than sto rage in the freezer. MAP is known to be light sensitive. ”

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National Institute for Occupational Safety and Health, NIOSH Manual of Analytical Methods… (1994)

“ Strong acids are toxic and corrosive. Triethylamine is toxic and corrosive.
SAMPLING: NOT E 1: Use sampling conditions listed below for the sampler selected: glass fiber filter (1) ; impinger (2) ; impinger followed by glass fiber filter (3) . See Table 3 for examples of exposure scenarios and which sampler to choose. Refer to the chapter on isocyanates [1] for more detailed informa tion on how to choos e the appropriate sam pler. NOT E 2: Field controls are made by sampling in an area near the analyte sampling location but where one would not expect to find analyte. ”

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Source: Wikisource

National Institute for Occupational Safety and Health, NIOSH Manual of Analytical Methods… (1994)

“ The FL/UV ratio may change somewhat at low levels. The sample peak should give a FL/UV response ratio within 15% of the ratio for the standard peak of comparable size. 17. Oligom er m easurem ent (total isocyanate) : Isoc yanate species for which pure analytical standards are not available, such as oligomeric isocyanates, must be measured by using the UV are a of the sam ple peak (s) and the slope of the linear portion of the calibration curve generated by analyzing monom er standards. ”

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Source: Wikisource

National Institute for Occupational Safety and Health, NIOSH Manual of Analytical Methods… (1994)

“ Using the second blank chromatogram, subtract this chromatogram electronically from sam ple chromatograms. This improves the UV baseline of sample chromatograms and facilitates accurate integration of peaks in low level samples. Analyze one add itional so lvent blank within the sam ple se t. 10. Analyze a minimum of three field controls and three field blanks or at least one field control and one fie ld blank for every ten samples. Use the field controls and field blanks to identify non-isocyanate peaks (generally reagent artifact peaks) that are likely to appear in the samples. ”

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Source: Wikisource

National Institute for Occupational Safety and Health, NIOSH Manual of Analytical Methods… (1994)

“ Im pinger sam ples are noted to have fe we r artifacts than filter sam ples. A ltho ugh this may be due in part to greater stability of the dilute M AP solutions versus M AP on filters , it ma y also be attribu table to the generally lower amount of reagent used in impinger samples as well as the solid-phase extraction procedure to which impinger sa m ples are s ubje cted . Stability of MAP-Isocyanate Derivatives: Pure, solid MAP-derivatized isocyanate monom ers are stable for years when stored in the freezer. ”

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Source: Wikisource

National Institute for Occupational Safety and Health, NIOSH Manual of Analytical Methods… (1994)

“ If there is an interfering peak in the area of interest that is not influenced by pH, changing the length of hold at the beginning of the run should move the interference peak away from the area of interest. NOTE 4: For multi-component monom ers such as TDI and HMDI and for multi-component isocyanate products that contain monom er and oligom er, ch anging the hold at the beginning, changing the gradient ramp, placing a hold in the middle of the ramp, or a combination of all of the abo ve m ay help in sep aration of the individual co m pon ents for a s pec ific prod uct. ”

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Source: Wikisource

National Institute for Occupational Safety and Health, NIOSH Manual of Analytical Methods… (1994)

“ Follow steps under Sample Preparation step 5 for the impinger part of the sample. b. Follow steps under Sample Preparation step 4 for the filter part of the sample.
NIOSH Manual of Analytical Methods (NMAM) , Fourth Edition ISOCYANAT ES, TOTA L (MAP) : METHO D 5525, Issue 1, dated 15 March 2003 - Page 5 of 17 CALIBRATION AND QUALITY CONTRO L: 7. Ca librate with six working standards in the range of interest. Prepare liquid standards with concentrations in terms of m oles isocyanate group per liter (normality) in the range 3 x 10 -5 N to 2 x 10- 8 N. Intersperse standards am ong sam ples. ”

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Source: Wikisource

National Institute for Occupational Safety and Health, NIOSH Manual of Analytical Methods… (1994)

“ As an example, these are equivalent to an LOD of 17 ng per sample and an LOQ of 42 ng per sample for HDI monom er. Bello et al. estimated the method detection limit to be 8 ng per sam ple for HDI monom er [9] . The instrumental LOD is substantially lower than the method detection limit, but is not achievable because of low levels of reagent-derived artifacts that are present in the chromatogram . Occ asionally an analyte peak will coelute with a relatively large artifact peak, raising the LOD and LOQ substan tially. ”

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Source: Wikisource

National Institute for Occupational Safety and Health, NIOSH Manual of Analytical Methods… (1994)

“ These HPLC recoveries were conducted at high analyte levels. It is recognized that quantitative recoveries of complex products are not possible at low levels because many components fall below the lim it of detection [7] . As part of an International Organization for Standardization (ISO) intercomparison study, two comm ercial products containing oligomeric isocyanates we re stu died [8] . Le vels spiked on filters were 2100, 1050, 525, and 105 ng NCO group per filter, corresponding to 2X, 1X, 0.5X, and 0.1X the U.K. STEL level. ”

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Source: Wikisource

National Institute for Occupational Safety and Health, NIOSH Manual of Analytical Methods… (1994)

“ METHO D 5525, Issue 1, dated 15 March 2003 - Page 3 of 17
SPECIAL PRECAUTIONS: Diisocyanates are highly toxic and known respiratory irritants. Follow manufacturer’s guidelines when handling pure products. Follow hazardous material shipping requirements when transporting. Preparation of urea derivatives, samples, and standards should be don e in a h ood to avo id exp osu re to iso cyanate and s olven t vapo rs. T oxicity of MA P is unknow n. Acetic anhydride is a severe irritant; acetonitrile is flamm able and an irritant. Methylene chloride is an irritant and suspected carcinogen. ”

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Source: Wikisource

National Institute for Occupational Safety and Health, NIOSH Manual of Analytical Methods… (1994)

“ Add 3 mL of 9:1 acetonitrile-methanol to the SPE cartridge. Elute at approx.1-2 mL/m in until the liquid level re aches th e top of the sorbent. C ollect th e eluate in a pre-weighed glass vial. f. Add 3 m L of m etha nol to the SP E ca rtridge. Elute and collect the eluate in the same vial as in step 5.g. g. Use a stream of nitrogen to reduce the volum e to exactly 1.0 mL. Rec onstitute to volum e if necessary by addition of acetonitrile. Determine exact volume using the sample weight and the density of acetonitrile (0.786 g/m L) . 6. Impinger + Filter a. ”

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Source: Wikisource

National Institute for Occupational Safety and Health, NIOSH Manual of Analytical Methods… (1994)

“ NOT E 3: Fie ld blanks are samplers handled exactly th e sam e as sam ples except tha t no air is drawn through them. 1. Filter sampling a. Calibrate each sampling pump with a representative sampler in line. NOTE: W hen sampling aerosol with aerodynamic diameter >20 μm, an IOM sam pler with stainless stee l cassette or other su itable inhalable sam pler shou ld be u sed [1,2] . b. Attach filter cassette to sampling pump with flexible tubing. c. Sam ple at a rate of 1 to 2 L/min (2 L/min for the IOM) for a total sample of at least 1 L. d. ”

National Institute for Occupational Safety and Health

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Quotes from NIOSH Manual of Analytical Methods… (National Institute for Occupational Safety and Health)

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