Page:NIOSH Manual of Analytical Methods - 5526.pdf/3

 METHYLTIN CHLORIDES: METHOD 5526, Issue 1, dated 15 March 2003 - Page 3 of 5 SAMPLE PREPARATION: 5. Rem ove the retaining ring from the sorbent tube and discard. Transfer the glass fiber filter and the m ain resin bed to a 10-m L sam ple vial. 6. Rem ove and discard the foam plug that separates the two resin sections in the sorbent tube. Transfer the back up res in bed to a second 10-m L sam ple vial. 7. Into each vial, add 2 ml of 1% acetic acid in acetonitrile to desorb the m ethyltin chlorides. Put the vials on a mechanical shaker for 30 minutes. 8. Into each vial, add 2 ml of pH 4 buffer and 1 ml of derivatizing solution. Place the vials on the mechanical shaker for 15 minutes. 9. Extract the solution with three 1 ml portions of hexane. Com bine the hexane fractions in a 5 m l volum etric flask and dilute to volume with hexane.

CALIBRATION AND QUALITY CONTRO L: 10. Ca librate daily with at leas t six wo rking standa rds over the ra nge of interest. a. Ac curately pipette 10 :l of the c alibration stoc k solution into a vial that contains 5 mL of 1 % acetic acid in ace tonitrile. De rivatize like a sam ple following steps 7 throug h 9. b. Serially dilute this standard derivatized solution with hexane to produce solutions over the range of 0.2 to 0.02 :g/mL (as tin) of each methyltin chloride. c. Transfer to gc autosampler vials with PTFE-lined caps. d. Analyze together with samp les and blanks (steps 12 through 14). e. Prepare calibra tion gra ph (p eak area s vs. :g tin for eac h m ethyltin chloride). 11. De termine desorption efficiency (DE) at least once for each lot of O VS tubes used for sam pling in the calibration range (step 10). Prepare three samplers at each of six levels plus three media blanks. a. Transfer the front so rbent se ctio n of the O VS sam pler to a 4m L vial. b. Inject a known volume of calibration stock solution, or serial dilution, directly onto the front sorbent bed of ea ch O VS tube. c. Ca p vial an d allow spik ed s orbe nt bed to stand overnight. d. Deso rb (steps 7 through 9 ) and analyze together with standards and b lanks (steps 1 3 through 15). e. Prepare a gra ph o f DE vs. :g for eac h m ethyltin chloride re covered. 12. Analyze three quality control blind spikes and three analyst spikes to ensure that the calibration graph and DE graphs are in control.

MEASUREMENT: 13. Set gas chromatograph according to manufacturer’s recomm endations and to conditions given on page 552 6-1. 14. Inject a 1-:L sa m ple aliqu ot m anu ally using solve nt flush technique o r with an au tosa m pler. NOTE: If peak area is above the linear range of the working standards, dilute with hexane, reanalyze, and apply the appropriate dilution factor in the calculations. 15. Mea sure the area s of th e pe aks of th e m ethyltin chlorides. A sample chromatogram is shown in Figure 1.

CALCULATIONS: 16. Determine the m ass, :g (corrected for DE), for each m ethyltin chloride 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. 17. Calculate conce ntration, C, of each m ethyltin chloride in the air volume sa m pled, V (L): NO TE : :g/L / m g/m 3

NIOSH Manual of Analytical Methods (NMAM), Fourth Edition