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Figure 3: Calibration Curve including Doxepin Internal Standard. Response Ratio ofCocaine/Doxepin (RA/RIS) vs Concentration Ratio Cocaine/Doxepin C¿IS¿¿0.511.522.530.000.501.001.502.002.50
Calibration Curve of Chromatogram Response Ratio of analytes vs. Concentration Ratio
“y” corresponds to the Response Ratio R(¿¿A/RIS)¿, “x” corresponds to the Concentration Ratio C¿IS¿¿, and 0.747 is the Response Factor, “F”Figure 4: Chromatogram Peaks of LLE
Figure 5: Chromatogram Peak of SPETable 3: Chromatogram Peak Areas of Cocaine and Doxepin in Solid Phase Extraction (SPE)Sample and Liquid-Liquid Extraction (LLE)SolutionPeak Area of CocainePeak Area ofDoxepinArea Ratios (RA/RIS)SPE1021562663733461.60LLE168402012188611.38Using the slope equation of figure 3 and the area ratios from table 3 above, the unknown concentration of cocaine for each extraction technique can be found.Table 4: Calculated Concentration of Cocaine in SPE and LLE Samples via Calibration Curvesincluding Doxepin Internal Standard and Calibration Curve without Doxepin Internal StandardSolutionVolumeSTDVolume ofMethanolConcentration ofCocaine (ppm)Concentration ofCocaine (ppm) via
Table 5: Percent Recoveries of Cocaine in SPE and LLE samples using calibration curvesincluding Internal Standard and excluding Internal StandardSPE With InternalStandardLLE With InternalStandardSPE Without InternalStandardLLE Without InternalStandard85.6%73.8%35.8%10.8%Based on the data of table 5, the percent recoveries found using both calibration curves provide a clear picture as to which graph is more appropriate to use. Using the calibration curve with the internal standard provided percent yields 50%-60% greater than the curve without the internal standard.
Table 6: Summary of ResultsCalculatedConcentration ofCocaine inUnknown (ppm)ActualConcentration ofCocaine inUnknown (250ppm)% RecoveryPeak AreaSPE21425085.6%102115626LLE18425073.8%1684020The fragment that gives rise to the peak at 272 m/z is the fragment that excludes the O−CH3of the ester.
This pattern results in an ion containing 16 carbon atoms, 3 oxygen atoms, 1 nitrogen, and 18 hydrogen atoms. Summing the atomic masses yields an ion of mass 272 amu. The base peak, which is 82 amu is given by this fragmentation pattern: