Page:NIOSH Manual of Analytical Methods - 2537.pdf/3
ME TH YL & ET HYL M ETH ACR YLAT E: ME TH OD 2537, Issue 3, dated 1 5 Ma rch 2003 - Page 3 of 4 c. Allow the tub es to air equ ilibrate for several m inutes , then cap the ends of the tubes an d allow to stan d overnight. d. Deso rb (steps 5-8) and a nalyze together with standards and blanks (steps 11 and 12). e. Prepare a graph of DE vs. µg analyte recovered.
MEASUREMENT: 11. Set gas chromatograph according to manufacturer’s recomm endations and to conditions given on page 2537-1. Inject a 1-µL sample aliquot manually using the solvent flush technique or with an auto sam pler. NOTE: If peak area is above the linear range of the working standards, dilute with the carbon disulfide solvent, reanalyze and apply the appropriate dilution factor corrections in the calculations. 12. Measure peak areas.
CALCULATIONS: 13. Determ ine the ma ss, µg (correc ted for DE), for each analyte 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) sorben t sec tions. NOTE: If W b > W f/10, report breakthrough and possible sample loss. 14. Calculate conce ntration, C, of each analyte in the air volume sa m pled, V(L):
NO TE : :g/L=m g/m 3
EVALUATION OF METHOD: Initial Method Development Effort (Issues 1 and 2) Method S43 (methyl methacrylate) was issued on July 6, 1979, and validated over the range of 193 to 725 m g/m 3 [3]. Average DE recovery results achieved in two independent studies were 98.1% [3] and 96-100% [5] over the ra nge of 56 0 to 2350 µg/sample. Overall precision (S rT) was estimated to be 0.063. Breakthrough volume was 6.46 L at a g ene rated air conce ntration of 78 6 m g/m 3 for methyl methacrylate under conditions of 90% relative humidity [3]. Subsequent storage stability results indicated that methyl methacrylate was stab le for 32 da ys (97.3% ) and ethyl m etha crylate fo r 23 d ays (95-10 0% ) @ 4°C [5]. Current Method Development Effort (Issue 3) [1] The current m etho d de velop m ent effort w as the res ult of reque sts to evaluate and improve problematic gas chromatography m ethods as part of the NM AM m ethods upd ate project. Initial evaluations confirme d that XAD-2 (400/200 mg) sorbent tubes were still the most suitable media for the sam pling and a nalysis of bo th methyl and ethyl methacrylate. The average DE recoveries, using substantially lower analyte concentration ranges than in previous studies (10x LOQ to 0.1x REL vs. 0.5x REL to 2.0x REL), we re 100.4 % for m eth yl m etha crylate and 102 .3% for eth yl me thac rylate. The LOD values for both m ethyl and ethyl methac rylate were lowered by a factor of 20 to 0.4 and 0.5 µg/sample, respectively. A 31-day storage stability study was completed for bo th m ethyl m etha crylate (96 .2% @ 0.05x RE L/P EL ) an d ethyl methacrylate (99.8% @ 0.05x REL/PEL) at 5°C.
NIOSH Manual of Analytical Methods (NMAM), Fourth Edition