Page:NIOSH Manual of Analytical Methods - 3600.pdf/3

 MA NEB, Derm al Patch: MET HO D 360 0, Issue 1, dated 15 M arch 200 3 - Page 3 o f 5 6.

7. 8. 9.

Prepare sufficient desorbin g s olu tion for all sam ple s a nd bla nks: 4 g L-cysteine and 12 g Na 4EDTAC2H 2O in 400 m L of de ionized water for every 10 sam ples (40 m L per sam ple). Prepare this solution in the field to prevent premature oxidation of the L-cysteine preservative. NOTE: The EDTA here m ust be the tetrasodium form, not the disodium form. See SPECIAL PRECAUTIONS. Add 40 m L of d eso rbing solution to each shipping bottle, cap, and shake well to wet the Nu Gauze® and dissolve the Maneb. Prepare 2 to 10 blank samples by adding 40 mL to clean Nu Gauze® patches in shipping bottles. Pack shipping bottles securely in blue ice or other means to keep at 4 / C, and ship via overnight express.

SAMPLE PREPARATION: NOT E: Desorption of samples is done on site. 10. On arrival at laboratory, store samples at 4 °C. 11. Ultrasonicate capped sample bottles for 5 to 10 minutes. 12. Transfer 1 to 2 mL of each desorbed sample solution, standards, and blanks to autosampler vials for analysis. Analyze within 24 hours.

CALIBRATION AND QUALITY CONTRO L: 13. Calibrate daily with at least six working standards over the range of 0.1 to 100 µg/mL. a. Pipet aliquots of ca libration s tock solution into 1 0-m L volum etric flas ks, and bring to volum e with desorbing solution. b. Include a calibration blank of unspiked working solution. c. Analyze together with field sam ples, field blanks, and laboratory control samples (steps15 through 17). d. Prepare a calibration graph (pe ak area vs. concentration, µg/m L). NOTE: To prepare media standards, prepare a slurry of Maneb in methanol, 1 mg/mL. Ultras onicate for approximately 2 minutes to pulverize and disperse the particles of Man eb. Shak e slurry periodically to ke ep the M ane b su spe nde d. Up to 20% ethylene glycol can be included to help keep the particles in suspension. W ithdraw a measured amount using a 100-µL syring e with a large bore ($ 19-gauge needle) and spike onto a dry Nu Gauze® patch within a 50- to 65-m L amber wide-m outh bottle. After drying, desorb the Maneb-spiked Nu Gauze® with 40 mL of desorbing solution and ultrasonicate. 14. Prepare laboratory contro l sam ples (LC S), in duplica te, with each sam ple se t. a. Spike Maneb in methanol onto 10-cm x 10-cm Nu Gauze® patches placed in 50- to 65-m L amber glass bottles in concentrations within the analytical range. b. Desorb with 40 mL of desorbing solution. c. Analyze along with field sam ples, standards, and blank s (steps 15 throug h 17).

MEASUREMENT: 15. Set liquid chromatograph to manufacturer’s recomm endations and conditions given on page 3600-1. 16. Transfer sa m ple aliquots to injection vials. Inject 100-µL aliquots man ually or with an autosam pler. Rinse and dry syringe after each injection. 17. Mea sure peak areas. If sample peak area exceeds the linear calibration range, dilute with aqueous 1% L-cysteine, 3% Na 4ED T AC2H 2O solution, reanalyze, and apply the appropriate dilution factor in the calculations.

NIOSH Manual of Analytical Methods, Fourth Edition