Page:NIOSH Manual of Analytical Methods - 1405.pdf/3

 ALC OH OLS CO MB INED : MET HO D 140 5, Issue 1, dated 15 M arch 200 3 - Page 3 o f 6 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 bind spikes and three analyst spikes to insure that the calibration graph and D E graph are in control.

MEASUREMENT: 11. Set gas chromatograph according to manufacturer’s recomm endations and to conditions given on pag e 14 05-1. Inject s am 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 eluent, reanalyze, and apply the appropriate dilution factor in calculations. 12. Measure peak area. Divide the peak area of analyte by the peak area of internal standard on the same chrom atogram.

CALCULATIONS: 13. Determ ine the ma ss, µg (correc ted for DE) of an alyte found in the sam ple front (W f) and back (W b) sorbent sec tions and in the average m edia blank front (B f) and (B b) sorben t sec tions. 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):

NO TE : :g/L = m g/m 3

EVALUATION OF METHOD: Previous Evaluations [2] This method, NIOSH 1405, combines and updates NIOSH Methods 1401 and 1402. Methods 1401 an 1402 were based on the 2nd edition NMAM Methods S66 (n-butyl alcohol), S53 (sec-butyl alcohol), S64 (isobutyl alcohol), S62 (n-propyl alcohol), S52 (allyl alcohol), S55 (diacetone alcohol), S54 (cyclohexan ol), S58 (isoamyl aocohol), and S60 (methyl isobutyl carbinol) which were issued on January 17, 1975 [3] and validated using 10-L air s am ples of atm ospheres generated by injec tion of the pure alcohol into dry air using a calibrated syringe drive [1]. No storage stability studies were performed. Overall precision and recoveries are shown Table 4, representing non-significant bias in each method. Current Evaluation [4] Meth ods for alcohols (n-butyl alcohol, sec-butyl alcohol, isobutyl alcohol, n-propyl alcohol, allyl alcohol, diacetone alcohol, cyclohexanol, isoamyl alcohol) were evaluated using analytes fortified on Anasorb CSC sorbent tubes (Lot #2000). Table 5 lists the desorption efficiency (DE) and precision for the compounds tested in the evaluation. Storage stability studies were performed at two different concentration levels: one at approximately 10 µg each analyte/sample for the low level, and the other at approximately 150 µg each analyte/sample for the high level. The sam ples w ere stored for 7, 14, 21, and 30 days at 5 °C. The res ults are sum m arized in Table 5.

NIOSH Manual of Analytical Methods (NMAM), Fourth Edition