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The increase in selectivity at a peak width setting
of 0.1 Da FWHM is due to the fact that Clenbuterol
is a chlorinated compound and thus the negative mass
deficiency can be used to eliminate interferents from the
urine matrix in SRM mode. This increased selectivity can
be achieved without detrimental loss of transmission.
Typically only a factor of two to three fold decrease in
peak area is observed between analyses performed at 0.7
and 0.1 Da FWHM, however, greater selectivity could
then be achieved.
The calibration curves for Clenbuterol concentrations
of between 0.1 to 100 pg/µL at resolution settings of 0.1
and 0.7 Da FWHM both demonstrate excellent linearity.
The calibration line at 0.7 Da FWHM showed a high
intercept due to chemical background in the urine blank.
This was significantly reduced by the use of high
resolution.
The use of higher resolution to increase selectivity
and precision could enable the limit of quantitation
of an assay to be lowered and achieves a higher degree
of confidence in identification of analytes in biological
matrices.
Table 2: Calculated standards at 0.1 Da FWHM
SAMPLE NAME AREA CALC AMT UNITS %RSD
Urine blank 0.00 0.00 pg/L
Urine blank 0.00 0.00 pg/L
Cal 0.1 pg/L 11245.02 0.10 pg/L 0.2%
Cal 0.1 pg/L 11272.54 0.10 pg/L 0.2%
Cal 0.5 pg/L 41960.02 0.46 pg/L 1.1%
Cal 0.5 pg/L 42592.84 0.46 pg/L 1.1%
Cal 1 pg/L 90353.60 1.02 pg/L 3.4%
Cal 1 pg/L 94633.92 1.07 pg/L 3.4%
Cal 5 pg/L 435920.49 5.04 pg/L 0.4%
Cal 5 pg/L 438538.32 5.07 pg/L 0.4%
Cal 10 pg/L 893656.24 10.36 pg/L 0.9%
Cal 10 pg/L 904758.00 10.49 pg/L 0.9%
Cal 50 pg/L 4120496.02 47.90 pg/L 1.3%
Cal 50 pg/L 4195902.58 48.78 pg/L .3%
Cal 100 pg/L 8667429.70 100.81 pg/L 0.5%
Cal 100 pg/L 8727427.54 101.50 pg/L 0.5%