Frequent Questions

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 minut

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
MeOH
+13% MTBE
t-BuOH


 

 

+6% EtOH
MeOH
+10% MTBE
t-BuOH

 Independent Check Stds
1 per 100 samples
or once per analysis batch
 

+10% EtOH
MeOH
+13% MTBE
t-BuOH

 

 

+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 is posted at http://www.epa.gov/otaq/regs/fuels/rfg/qa/420r03009.pdf. The original was posted in the Q&A posted on 10/31/94 which can found at http://www.epa.gov/otaq/rfg_qa.htm" See Question ID 3857 for RFG (Taken from the first question on http://www.epa.gov/otaq/regs/fuels/rfg/qa/420r03009.pdf )

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