Page:NIOSH Manual of Analytical Methods - 1460.pdf/3
ISOPROPYL ACETATE: METHOD 1460, Issue 1, dated 15 March 2003 - Page 3 of 3 a. Rem ove and disca rd back sorbent sec tion of a med ia blank sam pler. b. Inject a known amount of isopropyl acetate or of a standard solution of isopropyl acetate in solvent directly onto front sorbent section with a microliter syringe. c. Ca p the tube. Allow to stand overnight. d. Deso rb (steps 5 through 7 ) and analyze together with working standards (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 insure that the calibration graph and DE gra ph are in control.
MEASUREMENT: 11. Set gas chromatograph according to manufacturer's recomm endations and to conditions given on pag e 14 60-1 . Inject sam ple aliqu ot m anu ally using solve nt flush technique o r with autos am pler. NOTE: If pea k area is abo ve the linear ra nge of the working standard s, dilute w ith solve nt, reanalyze, and apply the appropriate dilution factor in calculations. 12. Measure peak area.
CALCULATIONS: 13. Determ ine the ma ss µg (co rrected for DE ) of isopropyl acetate found in the sam ple front (W f) and back (W b) sorbent sections, and in the averag e m edia blank front (B f) and back (B b) sorbent sections. NO TE: If W b > W f /10, report breakthrough and possible sample loss. 14. Calculate conce ntration, C, of analyte in the air volume sam pled, V (L):
NOTE:
- g/L=m g/m 3
EVALUATION OF METHOD: The current m ethod developm ent effort wa s th e re sult of req uests to evaluate and im prove problem atic gas chromatography methods as part of the NMAM methods update project. Initial evaluations confirmed that Anasorb CSC (coconut shell charcoal) tubes were still the most suitable media for the sampling and analysis of isopropyl acetate. The average DE recoveries for isopropyl acetate, at substantially lower analyte concentration ranges (17 to 698 µg versus 3.75 to 15.4 mg [1,2]) were improved over the previous method (98.4% [3] versus 86.2%[1,2]) when CS 2/m etha nol (99:1) w as u sed as the de sorption s olven t. The LOD for isopropyl acetate was lowered to 0.6 µg/sample [3] from the 10 µg/sample [1,2] reported in the previous method. A 30-day storage stability study was completed for isopropyl acetate with an average recovery of 99.9% [3].
REFERENCES: [1] [2] [3]
NIO SH [1977]. NIO SH Ma nua l of Analytical Metho ds, 2nd e d., V. 2, S50 , U.S. Departm ent of He alth and Human Services. DHEW (NIOSH) Publication No. 77-157-B. NIO SH [1977]. Do cum enta tion of NIO SH Valida tion T ests , NIO SH Contrac t No. CD C-9 9-74 -45. Department of Health, Education and W elfare. (NIOSH) Publication 77-185. Pende rgrass, SM [2000]. Isopropyl Acetate Backu p Data R eport, (unpublished, Novem ber).
METHOD WRITTEN BY: Stephanie Pendergrass, NIOSH / DART
NIOSH Manual of Analytical Methods (NMAM), Fourth Edition