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analyses using several separation techniques, providing expected results and easy method transfer.
• Cleaning Validations and Solvent/Column Quality Control – The high sensitivity of WCPC allows the chromatographer to detect small changes in solvent purity and column bleed over time. In addition, it is an ideal tool for cleaning validation where trace amounts of analyte need to be detected.
• Difficult Analyte Detection – The NQAD is an ideal detector for analytes that were previously difficult to detect such as phosphotidylcholine, a molecule which is challenging to separate and detect reproducibly because it contains both polar and nonpolar ends. Reproducibility detecting challenging compounds saves the customer time
Figure 5: Gradient Elution Effect of Different Universal Detectors
analytes that elute later in the chromatogram (with a higher concentration of organic) are greatly exaggerated. Because the response from the NQAD is not as dependent on mobile phase composition, a much more accurate representation of analyte concentrations can be achieved, even during gradient elution methods (Figure 5).
Areas of Application Given below are the typical areas of application that the NQAD is being used for:
• Impurity Analysis – The high sensitivity coupled with the wide dynamic range possible with WCPC allows for impurities to be detected along with the main analyte peak in a single run, a time saving benefit.
– The additional benefit of fraction collection is available for the isolation of impurity peaks so they may be characterized using alternative instrument techniques.
• Excipients Characterization – Many excipients do not contain a chromophore which makes WCPC an ideal orthogonal detector to UV detection. Seeing more sample components per run saves time and money as less runs need to be performed and less organic solvents are used reducing disposal costs.
• Method Transfer – WCPC detectors are UHPLC/HPLC/SFC compatible. This allows the use of the same detector for multiple sample
A typical instrument configuration would include the WCPC detector as an orthogonal detector to UV detector and/or a Mass Spectrometer.
Commercial products based on WCPC The NQAD™ or Nano Quantity Analyte Detector is the first aerosol based detector in the field of Universal Detector for Liquid Chromatography to utilize Water Condensation Nucleation. The detector is optimized for use in UHPLC, HPLC and SFC.
The NQAD detector is designed and manufactured by Quant Technologies, Blaine, MN, USA and is exclusively distributed by Dorton Analytical Ltd in the United Kingdom.
The author thanks Quant Technologies for the use of the diagrams included in this article.
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