The acceptable range of surrogate recovery is from 50 to 120% for surrogate level of 50 ng/g. If the recovery of the surrogates is outside this range, the sample should be repeated and/or the entire analytical technique should be reviewed.
Method blanks should be run frequently to correct for background contamination.
5.2 Method Performance
Based on a 5.00 g sample and a final volume of 0.5 mL, the method detection limit (MDL) for both DBD and DBF is 1 ng/g. It was obtained by replicate analysis of spiked defoamer samples in a single laboratory. The MDL actually achieved in a given analysis will vary depending on instrument sensitivity and sample matrix effects.
The method has been tested for linearity of spike recovery from defoamers and has been demonstrated to be applicable over the concentration range from 1 to 100 ng/g.
In a single laboratory, six replicate determinations of DBF and DBD in a defoamer sample spiked at 10 ng/g level gave a mean recovery and a coefficient of variation of 103% and 8.9% respectively for DBF, and 106% and 5.9% respectively for DBD.
