Page:NIOSH Manual of Analytical Methods - 2005.pdf/3

This page needs to be proofread.

NITROAROMATIC COMPOUNDS: METHOD 2005, Issue 3, dated 15 January 1998 - Page 3 of 5 a. b.

Prepare three tubes at each of five levels plus three media blanks. Inject a known amount of calibration stock solution directly onto the front sorbent section of each silica gel tube with a microliter syringe. c. Allow the tubes to air equilibrate for several minutes, then cap the ends of each tube and allow to stand overnight. d. Desorb (steps 5 through 7) and analyze together with standards and blanks (steps 11 and 12). e. Prepare a graph of DE vs µg analyte recovered. 10. Analyze three quality control blind spikes and three analyst spikes to ensure that the calibration graph and DE graph are in control.

MEASUREMENT: 11. Set gas chromatograph according to manufacturer’s recommendations and to conditions given on page 2005-1. Inject a 1-µL sample aliquot manually using the solvent flush technique or with an autosampler. NOTE: If peak area is above the linear range of the working standards, dilute with methanol, reanalyze and apply the appropriate dilution factor in the calculations. 12. Measure peak areas.

CALCULATIONS: 13. Determine the mass, µg (corrected for DE) of analyte found in the sample front (W f) and back (Wb) sorbent sections, and in the average media blank front (B f) and back (Bb) sorbent sections. NOTE: If Wb > Wf/10, report breakthrough and possible sample loss. 14. Calculate concentration, C, of analyte in the air volume sampled, V(L):

C

NOTE: µg/mL

(Wf

Wb V

Bf

Bb)

, mg/m 3

mg/m3

EVALUATION OF METHOD: The update of this method included the use of capillary column chromatography that lowered the LOD/LOQ values, a lower 5-level desorption efficiency study, and a 30-day storage stability study for each analyte [1]. The method evaluation data for these compounds are listed in Table 2. Methods S217, Nitrobenzene, and S218, 4-nitrochlorobenzene, were initially issued on November 21, 1975 [4]. Method S223, o-nitrotoluene was issued on December 19, 1975 [4]. The analytesm-nitrotoluene and p-nitrotoluene were added on May 15, 1984 [3]. In the original method development work, sample tube capacity, or breakthrough, was determined as 5% of the generated atmosphere concentration as measured in the effluent of the sample tubes. Capacity was measured at >2.8 mg/sample for nitrobenzene; >2.5 mg/sample for nitotoluene isomers; and >2.2 mg/sample for 4-chlorobenzene [2.]

REFERENCES: [1] Pendergrass SM [1997]. Backup data report for nitroaromatic compounds method development. Cincinnati, OH: National Institute for Occupational Safety and Health, DPSE/NIOSH (unpublished December). [2] NIOSH [1977]. Documentation of the NIOSH Validation Tests, S217, S218, and S223, U.S. Department of Health, Education, and Welfare, Publ. (NIOSH) 77-185. [3] NIOSH [1994]. m-Nitrotoluene and p-Nitrotoluene: Method 2005. In: Eller PM, Cassinelli ME, eds. th NIOSH Manual of Analytical Methods, 4 ed. Cincinnati, OH: U.S. Departmentof Health and Human NIOSH Manual of Analytical Methods (NMAM), Fourth Edition

This article is issued from Wikisource. The text is available under Creative Commons Attribution-Share Alike 4.0 unless otherwise noted. Additional terms may apply for the media files.