I am working on the determination of tulathromycin in rat faeces using QE-focus (Thermo Fisher)(Waters BEH C18, 2.1x100mm, 1.7um)(0.1%FA+H2O, 0.1%FA+ACN) . I encountered two tricky problems. 1.Carry-over effect is too serious. I have tried using Needle wash MeoH:h2O:acn:IPA=1:1:1:1, But, it doesn't work. 2. Tulathromycin was detected in blank rat faeces. We have tried some other sources of feces, But it doesn't work. We use SPE MCX (Waters) cartridges to clean matrix. We have tried many methods in the past two months, but have little effect. what should I do to reduce carry-over effect and blank interference.? Thank you everyone. I'd appreciate some suggestions on my work
If you do not mind, can you share the blank and one sample chromatographs? Then only the provided information might be helpful
I agree with Udaya Jayasundara:- If you do not mind, can you share the blank and one sample chromatographs? Then only the provided information might be helpful
MORE basic information is needed to provide a constructive suggestion.
Can you provide us with one chromatogram showing a true BLANK analysis (NOTE: A "blank" is the mobile phase at initial conditions).
Can you provide us with a chromatogram showing what your "sample" looks like for comparison?
Only with this type of basic information can any troubleshooting suggestions be made that are applicable to your method and concern. Suggestions made w/o this information are speculative.
You should also speak with someone at your school (perhaps your teacher) who has formal experience using the instrument to develop methods too.
" "Carry-over" is a term used to describe a type of sample contamination which causes sample peaks to re-appear in later runs which do not actually contain the sample (e.g. blank runs). The contamination can last for several sequential runs, often decreasing in amount after each injection (which is a key observation when troubleshooting). When proper instrument training has been provided, modern HPLC system designs make carryover extremely rare, but when it does appear, the contamination can be due to: (1) A lack of HPLC maintenance; (2) Overloading samples which foul the column; (3) Poor Wash Vial Usage and/or Sample Vial Selection; (4) Inadequate operator training in how to set-up and use the chromatography system. *Note: Proper operator training greatly reduces the chances of contamination and is the most overlooked reason for the problem. "
Here is a link to a free article which offers possible causes, advice and troubleshooting tips to solve "carryover" problems in HPLC / LC-MS.
- "Carry-Over (Carryover) Contamination in HPLC and LC-MS Systems"; https://hplctips.blogspot.com/2015/02/carry-over-carryover-contamination-in.html
Need to see the chromatograms ploting at the same Y scale so we know the degree of carryover between the std and following blank.
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