ALC OH OLS IV: MET HO D 140 3, Issue 3, dated 15 M arch 200 3 - Page 3 o f 5 c.
Allow the tubes to air equilibrate for several m inutes , then cap the ends of ea ch tube a nd a llow to stan d overnight. d. Deso rb (steps 5-7) and a nalyze together with standards and blanks (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 ensure that the calibration graph and DE grap h are in con trol.
MEASUREMENT: 11. Set the gas chromatograph according to manufacturer’s recomm endations and to conditions given on page 1403-1. Inject a 1-µL sample aliquot manually using the solvent flush technique or with an autosam pler. NOTE: If peak area is above the linear range of the working standards, dilute with desorption so lvent, rean alyze and ap ply the ap prop riate dilution facto r in the c alculations. 12. Me asu re pe ak area s.
CALCULATIONS: 13. Determine the m ass, µg (co rrected for D E) of a na lyte 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 back (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 : m g/L = m g/m 3
EVALUATION OF METHOD: Initial Method Development Effort (Issues 1 and 2) Methods S79 (2-methoxyethanol), S361 (2-ethoxyethanol), and S76 (2-butoxyethanol) were issued on Februa ry 14, 1975 [2, 7], March 17, 1978 [3, 8, 9], an d Fe brua ry 14, 19 75 [2, 7], respectively, and validated using, respectively, 50-, 6-, and 10-L air samples of atmospheres generated by calibrated syringe drive. Storage stability of the se a lcohols was n ot determ ined. Current Method Development Effort (Issue 3) [10] Issue 3 is an update and improvement of NMAM 1403. Improvem ents in the method include the use of capillary column chromatography, lower LOD/LOQ values, a new 5 level desorption efficiency (DE) study at lower levels, and a storage stability study at 7, 14, and 30 days. The average D E determ ined for 2-m ethoxyethanol was 97 .8% (R SD = 1.0), for 2-ethoxythanol the DE was 100.2% (RSD = 1.2), and for 2-butoxyethanol the DE was 99.9% (RSD = 1.3). The average 30-day storage stability recovery at approxim ately 0.5x RE L for 2-m ethoxyethanol was 10 3.8% (R SD = 1.4), for 2-eth oxyethan ol was 105.0% (RS D = 1.6), and fo r 2-butox yethan ol was 82 .6% (RS D = 1.4). The precision and accuracy information listed in Table 2 was calculated by using the data from generated air sam ples [7, 8] an d the ana lytical data from the current update [10].
NIOSH Manual of Analytical Methods, Fourth Edition
