<p><span style=": ; mso-bidi-font-family: 'Times New Roman'; mso-fareast-language: EN-GB; color: #323d4f; Trebuchet MS&quot: ; font-size: 10pt; sans-serif&quot: ; font-family: Trebuchet MS; , &quot: ; mso-fareast-font-family: 'Times New Roman'; ">Hi All

I’m in the process of developing and validating methods for a finished product that contains the following substances:
Naphazoline HCl - HPLC – UV Detector
Polysorbate 80 - HPLC – ELS Detector
Hypromellose - HPLC – ELS Detector
Polyaminopropyl biguanide - HPLC – ELS Detector
Zinc sulphate - AA
Disodium edentate - HPLC – UV Detector

The methods will be used for stability testing. Would I be required to perform forced degradation studies on all of the above methods? How would you prove "peak purity" when using a ELS detector? At this stage the methods are HPLC but my intention is to convert them to UPLC.  Any suggestions would ne appreciated.

Many Thanks
Mike</span></p><p class="MsoNormal" style="margin: 0in 0in 10pt;"><span style="line-height: 115%; font-family: "Verdana", "sans-serif"; color: #323d4f; font-size: 7.5pt; mso-fareast-font-family: 'Times New Roman'; mso-bidi-font-family: 'Times New Roman'; mso-fareast-language: EN-GB;"><br clear="all" style="mso-special-character: line-break;"/></span></p>


  • Using the ELSD by itself? Not much (e.g., peak shape distortion). But there’s nothing against using other detection systems for this type of test, particularly if the compound doesn’t show up using those systems. PDA would be my choice, MS is good too if available. If any of the degradants have chromaphors, the PDA would find them real quick. Other types of detectors could be useful too.