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HPLC Analysis

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  • 10-04-2014 8:52pm
    #1
    spoona
    Registered Users Posts: 3 ✭


    I recently did an analysis of carbofuran which gave a lambda max of 274 in the UV instrument, but when analysed by HPLC with the detector set at 274 it wouldn't detect the compound... the literature listed 205 nm as the best suitable detector wavelength, and when I used this the results were perfect....

    Anyone have any idea why the UV reading for the lambda max would be 274 nm but the best detection wavelength in HPLC was at 205 nm??

    There was no other compound in the solution other than acetonitrile which was absorbing at 195 nm.
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    #2
    El Siglo
    Registered Users Posts: 3,803 ✭✭✭El Siglo


    spoona wrote: »
    I recently did an analysis of carbofuran which gave a lambda max of 274 in the UV instrument, but when analysed by HPLC with the detector set at 274 it wouldn't detect the compound... the literature listed 205 nm as the best suitable detector wavelength, and when I used this the results were perfect....

    Anyone have any idea why the UV reading for the lambda max would be 274 nm but the best detection wavelength in HPLC was at 205 nm??

    There was no other compound in the solution other than acetonitrile which was absorbing at 195 nm.

    When was the last time the instrument was calibrated and serviced? I remember the spectrophotometer I used before used to mess up if the sample holder had even the tiniest smudge. Have you got any reference standards? Try running these and see what you get. Might be worth running your sample again and seeing if the same result comes back.


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    #3
    spoona
    Registered Users Posts: 3 ✭spoona


    I'm not positive on the most recent date of calibration, but I ran other samples of imidacloprid, clothianidin and thiamethoxam and they all gave accurate lambda max readings which were perfectly suitable for the HPLC detector and as was stated in the literature.

    I can't completely rule out an issue with the spectrophotometer, but I don't think it was the issue.

    Any other thoughts on why this might happen?


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    #4
    The_Captain
    Registered Users Posts: 1,376 ✭✭✭The_Captain


    If it's not a calibration issue, most likely scenario is sample contamination


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    #5
    spoona
    Registered Users Posts: 3 ✭spoona


    It has been suggested to me that while it's unusual that the lambda max wouldn't be suitable for the HPLC detection, that 205 nm is so low for detection that it should pick up anything at that wavelength that the results would still be reliable, especially since you would expect loads of noise at that wavelength but I was getting clear defined peaks.

    ??


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