Concerning the OFID test method for oxygenates:a) The method has a program run of 20 minutes, but over half the eluting peaks on the table in the method come off after 20 minutes. For example, the last oxygenate present on the table elutes off at 38 38 minutes. Can one use other chromatographic conditions such as those conditions set in the ASTM draft method for OFID analysis to achieve shorter retention time and better analytical techniques?
a) Yes (10/31/94)
b) Yes (10/31/94)
c) It would generally be inappropriate to purchase prepared Calibration and Independent Standards from the same purveyor; however, if one is purchasing pristine pure compounds for the purported purpose of preparing precise standards, one vendor may be acceptable.
The main concept is that an inaccuracy caused by an impure standard material would be identified by the use of a different compound, assuming that the second compound is not impure by an identical amount. Similar logic is applied in that a different chemist should prepare the second standard to avoid replicating an inadvertent mispreparation. (10/31/94)
d) Quality control for OFID (FR V59, No32, pp7828-7833)
| OC Provision | Required | Recommended |
|---|---|---|
| CalCheck Standards 1 per 10 samples or once per analysis batch | +10% EtOH
| +6% EtOH MeOH +10% MTBE t-BuOH |
| Independent Check Stds 1 per 100 samples or once per analysis batch | +10% EtOH | +6% EtOH MeOH +10% MTBE t-BuOH |
| Spikes Required only if matrix effects are suspected. One per analysis batch or one per ten samples recommended | +10% EtOH MeOH +16% MTBE t-BuOH | +10% EtOH MeOH +13% MTBE t-BuOH |
| Duplicates | Limit to Range | |
| (Duplicates are not required, but it is recommended that one sample in tenor one per analysis batch be duplicated)(10/31/94) | MeOH 0.043C + 0.010 (0.27-1.07%) MeOH 0.053C (1.07-12.73%w/w) EtOH 0.053C MTBE 0.029C + 0.069 DIPE 0.048C ETBE 0.074C TAME 0.060C |
This question and answer was posted at Consolidated List of Reformulated Gasoline and Anti-Dumping Questions and Answers: July 1, 1994 through November 10, 1997 (pdf) (18.2 MB, July 2003, EPA420-R-03-009)