Page:NIOSH Manual of Analytical Methods - 5525.pdf/17

 ISOCYANAT ES, TOTA L (MAP): METHO D 5525, Issue 1, dated 15 March 2003 - Page 17 of 17 APPENDIX D: PREPARATION OF B ULK DERIVATIVES 1. Dilute bulk 1/10 in methylene chloride by wt/wt. Quickly proceed to step 2. a. W eigh disposable 7 m L vial em pty. b. Add about 0.5 g bulk, weigh vial again. c. Add 4.5 g (3.4 mL) m ethylene chloride by volume addition, weigh vial again. Use this total weight of 1:10 dilution in calculating final concentration of bulk solution. Density of methylene chloride is 1.325 g/m L. 2. W eigh 1.0 mL of the 1:10 dilution of bulk to determine density. Use this density in calculating the final concentration of bulk solution. 3. Dilute the solution resulting from Step 1 1:100 (10 :L into 990 :L) in methylene chloride by vol/vol. Imm ediately proceed to step 4. 4. Add 25 :L of the solution resulting from Step 3 to 975 :L acetonitrile containing 5X10 -4 N MAP ( 1:40 dilution). 5. Let react overnight in dark. 6. Add 5 :L acetic anhydride. Allow to react at least two hours at room tem perature or overnight in the refrigerator before proceeding. 7. Analyze by HPLC, injecting 30 :L. 8. Total dilution is about 1:40,000. 9. Final bulk solution concentration (C B, g/mL):

where: W tbulk = W ttot = Dens 1:10 = DF =

the the the the

weight of sample (Step 1) combined weight of sample and methylene chloride (Step 1) density of the initial sample preparation (Steps 1 and 2) dilution factor (Steps 3 and 4) (as presented above, DF = 0.00025)

NIOSH Manual of Analytical Methods (NMAM), Fourth Edition