Example 3
Biological samples such as urine were directly analyzed using the SFME nanoESI. FIG. 2 panels A-C. Calibration curves for quantitation of methamphetamine (FIG. 2 panel A), nicotine (FIG. 2 panel B), and benzoylecgonine (FIG. 2 panel C) in synthetic urine samples. 10 synthetic urine containing the drugs and internal standards were used as samples for the measurement. 5 μL ethyl acetate (EA) was used as the extraction phase for extraction, purification and spray. Internal standards: methamphetamine-d8 at 0.8 ng/mL, nicotine-d32 at ng/mL, benzoylecgonine-d3 at 1 ng/mL. The single reaction monitoring (SRM) transitions used: methamphetamine m/z 150→91, methamphetamine-d8 m/z 158→93; nicotine 163→130, nicotine-d3 m/z 166→130; benzoylecgonine m/z 290→168, benzoylecgonine-d3 m/z 293→171. Partition coefficients: LogPmethamphetamine=2.07; LogPnicotine=1.17, LogPbezoylecgonine=−0.59.
The matrix effect due to high concentration salts were minimized. Good LODs were obtained for drugs of abuse, even for benzoyecgonine with relatively low partition coefficient for the extraction phase. The partition coefficient (LogP) is defined as: LogP=log([solute]octanol/[solute]water), which represents the differential solubility of an un-ionized compound in an organic phase such as octanol immiscible with the aqueous phase at equilibrium.
