17 Results
The linearity of the HPLC system was tested using analytical standards of Ibuprofen and Paracetamol at a range of 10-400mg/L. The specifi c wavelengths of both Ibuprofen and Paracetamol were utilised by the Diode Array Detector. Figures 2 show the calibration curves of both target analytes, at the maximum absorbance wavelengths.
The SCION HPLC exhibited excellent linearity over the concentration range of 10-400mg/L for both target compounds, each with an R2 value of 0.9994. Following the calibration standards, the sample containing the Ibuprofen and Paracetamol tablet extracts was analysed. Figure 3 shows the stacked chromatograms of both target compounds at their specifi c wavelengths.
Figure 4. Absorbance spectra comparison of both Ibuprofen and Paracetamol.
Figure 3. Stacked chromatograms of target compounds at their specifi c absorbance wavelengths.
Ibuprofen has a specifi c absorbance wavelength of 237nm whereas Paracetamol has a maximum absorbance at 254nm. Utilising the multi-wavelength capability of the Diode Array Detector it was possible to detect both target compounds in a single injection, in under 12 minutes. The concentration of both target compounds was determined using the respective calibration curves. The quantitative value for Ibuprofen was 34.11mg/L whilst the Paracetamol was calculated at 39.24mg/L.
For further identifi cation and confi dence in results, the absorbance spectra of the target compounds were also compared with a spectral library. Figure 4 shows the absorbance spectra of both Ibuprofen and Paracetamol.
CompassCDS software was used for the spectral library comparisons, in which an in house reference library was used. Figure 4 shows the overlay of the absorbance spectra generated during both the sample analysis and the reference standard, in which both Ibuprofen and Paracetamol exhibited a 100% match, thus confi rming the positive identifi cation of both target compounds (as the spectra of the sample is overlaid with the reference and the match is 100%; the reference spectra is not visible). Repeatability of the system was performed with six consecutive injections of the 10mg/L calibration standard. Figure 5 shows the overlay chromatograms for both Ibuprofen and Paracetamol.
Excellent repeatability of the 10mg/L analytical standard was observed, over six consecutive injections; with an RSD of 0.27% for Ibuprofen at 237nm and 0.18% for Paracetamol at 254nm. Retention times were also stable and reproducible with RSD values of 0.06% and 0.04%, respectively. The excellent repeatability and linearity observed demonstrates the robustness of the SCION HPLC system.
Conclusion
SCION Instruments developed a fast, accurate method for the simultaneous identifi cation and quantifi cation of combination drugs by HPLC-DAD. This method is critical to numerous industries including pharmaceutical and toxicology. With a single injection and utilising the multi-wavelength capabilities of the Diode Array Detector it was possible to clearly separate Ibuprofen and Paracetamol, two commonly used over the counter medications, in under 12 minutes. Compound identifi cation was further confi rmed through absorbance spectral comparisons using CompassCDS. Excellent linearity and repeatability of the SCION HPLC-DAD was demonstrated with low RSD values and high R2 values.
Figure 5. Overlay of 10mg/L analytical standard chromatograms (n=6).
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