|
The
method detection limit of 0.2 ppbv for each target carbonyl
was achieved. 10 collocated samples were collected for
evaluation of method precision including both sampling
and analysis performance. Tables 5.2a and 5.2b shows
the percentage difference between field samples and
collocated samples. Precision of field replicates should
be 20% or better, hence the collocated samples of 10th
July, 1999 and 19th September, 1999 were invalidated
due to their exceedence of this standard. It was discovered
that these breaches of the precision standard were due
to the flow rate of the collocated sampler being unstable.
The percentage differences were below 20% for all target
compounds, except on 15th June, 1999, 13th October,
1999 and 6th November, 1999, but they were all deemed
acceptable under the precision test. The average percentage
difference of formaldehyde and acetaldehyde were 14.93%
and 15.65% respectively.
|
Table
5.2b Summary of Percentage Difference Between
Carbonyl Field Samples and Collocated Samples
|
| Compounds |
Average
Percentage Difference (%) |
| formaldehyde |
 14.93 |
| acetaldehyde |
15.65 |
|
|