TERPENES: METHOD 1552, Issue 1, dated 15 May 1996 - page 3 of 4 MEASUREMENT: 11. Set gas chromatograph according to manufacturer's recommendations and to conditions given on page 1552-1. Inject 1-µL sample aliquot manually using solvent flush technique or with autosampler. NOTE: If peak area is above the linear range of the working standards, dilute with eluent, reanalyze and apply the appropriate dilution factor in calculations. 12. Measure peak area. CALCULATIONS: 13. Determine the mass, µg (corrected for DE) of analyte found in the sample front (Wf) and back (Wb) sorbent sections, and in the average media blank front (B) f and back (Bb) sorbent sections. NOTE: If Wb > Wf /10, report breakthrough and possible sample loss. 14. Calculate concentration, C, of analyte in the air volume sampled, V (L):
C
Wf
Wb
Bf V
Bb
, mg/m 3
EVALUATION OF METHOD: Sampling and analytical conditions for each terpene were derived from independent methods [1-3]. Recovery was determined by spiking coconut shell charcoal tubes with known amounts of each analyte in CS2 solution. Six samplers were spiked at each of three levels (20-, 60-, and 100-µg) for each terpene (18 samples for each analyte). Recovery, LOD, and stability data are listed in Table 2. Mean recoveries ranged from 93.4% to 97.6% with precisions, as calculated from the pooled relative standard deviations ( r), of <2% for each analyte. The LODs ranged from 0.3 to 0.6 µg per sample. Samples stored at 5 C were stable for 30 days. During the development of this method for terpenes, it was found that some terpenes (e.g., camphene, myrcene, -terpinene), upon exposure to activated charcoal and CS2 exhibit rearrangement or decomposition to other terpenes or related compounds. Because -terpinene exhibited an acceptable recovery, it was selected for a study to determine the degree of decomposition/rearrangement. The difference between standards aged 21 days and freshly prepared standards was not significant. However, spiked charcoal tubes desorbed with and allowed to stand in CS2 for 1 day gave a recovery of -terpinene of 77.4% with remainder converting to 1-methyl-3-methylethyl benzene. Spiked charcoal tubes aged for 30 days and then desorbed in CS2 gave a -terpinene recovery of 12.4% with 87.6% converting to 1-methyl-3-methylethyl benzene [3]. REFERENCES: [1] [2] [3] [4]
Searle E [1989]. Determination of airborne limonene vapour by charcoal tube sampling and gas-liquid chromatographic analysis. Analyst 114:113-114. Konttinen S, Kurttio P, Raunemaa T, Kalliokoski P [1989]. Comparison of methods for analyzing occupational monoterpene exposures. Chemosphere 19:1483-1488. Pendergrass SM [1992]. Terpene method development. Unpublished report, NIOSH, DPSE, MRSB. Stromvall M, Petersson G [1992]. Protection of terpenes against oxidative and acid decomposition on adsorbent cartridges. J Chromatogr 589:385-389.
NIOSH Manual of Analytical Methods (NMAM), Fourth Edition
