Page:NIOSH Manual of Analytical Methods - 2557.pdf/3
DIACETYL: METHOD 2557, Issue 1, dated 15 August 1994 - Page 3 of 4
d. Desorb (steps 5 through 7) and analyze together with standards and blanks (steps 11 and 12). e. Prepare a graph of DE vs μg diacetyl recovered. 10. Analyze a minimum of three quality control blind spikes and three analyst spikes to ensure that the calibration graph and DE graph are in control. MEASUREMENT:
AL
11. Set gas chromatograph according to manufacturer’s recommendations and to the conditions listed on page 2557-1. Inject a 1-μL sample aliquot manually using the solvent flush technique or with an autosampler. NOTE: If peak area is above the linear range of the working standards, dilute with solvent, reanalyze
and apply the appropriate dilution factor in the calculations. 12. Measure peak areas. CALCULATIONS:
IC
13. 13. Determine the mass, μg (corrected for DE), of diacetyl found in the sample front (Wf ) and back (Wb) sorbent sections, and in the average media blank front (Bf ) and back (Bb) sorbent sections. NOTE: If Wb > Wf /10, report breakthrough and possible sample loss 14. Calculate concentration, C, of diacetyl in the air volume sampled, V(L): (Wf + Wb ) - (Bf + Bb ) V
ST OR
C=
, mg/m3
NOTE: μg/L Ξ mg/m3
EVALUATION OF METHOD:
HI
This method was developed in response to a request to identify and quantitate possible hazardous chemicals in food packaging facility. Diacetyl, a toxic and reactive compound [2], was identified as a possible suspect chemical in the facility. Because of the reactivity of diacetyl, several specialized analytical conditions were required during the method development. The use of a deactivated glass inlet liner and a Stabilwax-DA capillary column were required to prevent the reaction of diacetyl in the injection port and with the column which resulted in tailing peaks and decomposition of the analyte. It was further determined that the reactivity of diacetyl could be inhibited or slowed down by storage in the dark at 5 °C. Standards prepared in amber volumetric flasks were stable for a couple days. Even with storage under these conditions, collected samples containing diacetyl were only stable for 7 days (95%). The average DE recovery for diacetyl was 90% over a range from 47 to 470 μg [1]. A set of samples was prepared to check the method. The mean recovery was 103.1% (n=12) with a standard deviation of 4.45%. The precision of an average test result was 9.79% [3]. NOTE: While this method can be used to sample and analyze for acetoin, recovery is not optimized and is 65%-70%, which is below the acceptable recovery criteria of at least 75% for NMAM methods [4]. REFERENCES: [1] Pendergrass SM [2001]. Diacetyl backup data report, unpublished report, NIOSH/DART.
NIOSH Manual of Analytical Methods (NMAM), Fourth Edition