Chromatography Forum

Hi All,

I'm new to using Fluorescence detection with LC and I'm currently developing a method with UV and FL detection. I have a question I was hoping someone could help me with with. If I run a system suitability for the FLD system are the general chromatography system suitability criteria used? i.e. t < 2, N > 2000, Rs > 2 etc. I'm developing and validating this method to meet FDA/ICH requirements.

I'm new to using Fluorescence detection with LC and I'm currently developing a method with UV and FL detection. If I run a system suitability for the FLD system are the general chromatography system suitability criteria used?

My opinion would be: absolutely. And why not?

But I'm not a cGMP "expert". I'm hoping/figuring that you are running the column eluent through the two detectors in series and compiling the data seaprately, may save half your injections (unless the fluorescence detection is too sensitive and requires dilution of the solutions).

None of those suggestions are detector-specific.

Taking a more general view, they *are* only suggestions. The point to system suitability is to have a set of values which demonstrate that the method is working. It's up to you to establish what those value are.

Just as an example, if you're looking at a low-level degradant eluting after the parent peak, at an Rs of 2 you won't even see the small peak; it will be buried under the tail of the big peak. You may need Rs of 4 or 5 to reliably measure, and that should be reflected in your system suitability.

Thank you for your comments and suggestions.
Yes I'm running the DAD & FLD in tandem to detect 2 components in my sample for assay quantitation. I'm seeing great chromatography performance for my DAD but the for the sample detected by FLD performance is not as good. I'm detecting a monomer stabiliser by FLD and therefore my sample diluent contains a different but very closley related monomer stabiliser. These 2 stabilisers are eluting close together with an Rs of approximately 1.7, therefore I'm wondering if setting an Rs > 1.5 is acceptable? Prescision and tailing are meeting the reccomended acceptance criteria for system suit.