Hi everyone,
I want to ask your opinion about different ways to decrease average noise and standard deviation in our chromatograms which help us to improve selectivity and sensitivity of our LC-MS/MS and LOD and LOQ values as well.
I work on grain (mainly wheat and corn) mycotoxins in my lab, and usually after reconstituting my extracts with eluents, I keep them in fridge overnight to remove sediments.
I also use syringe filter as they have always been helpful in extraction process.
I will be more than happy to hear about your thought and other methods that you use in this way.
Warmest regards,
Nasim
Your question is very general and to provide the most constructive advice, it would be best to be on-site, looking over your specific method(s), instrument setup and techniques. This is how we provide the best quality advice and suggestions that can help a specific client (by looking over what they are doing). However, here are some generic suggestions in no particular order that may help you:
(1) Improve your existing method to better resolve the peaks of interest. Have the targeted peaks elute early with good peak shapes to improve detection (but with good K primes > 2 !). This includes using sample prep procedures (if applicable) that focus the target compounds, simplifying the mobile phase used, using narrow bore columns with small particles and optimized flow rates for YOUR instrument. *Remember that your results will only be as good as your method. Put time into developing the best (optimized) method FIRST.
(2) Once the method parameters have been optimized, optimize the MS settings. Optimize, gas flows, temperatures, ion filters etc. Reduce noise, maintain a clean flow path and source. Do not use Ion pairing reagents !
(3) Have the HPLC and MS systems professionally cleaned and serviced on a regular basis. Use high quality solvents, additives and gasses. Poor quality materials degrade your signal.
(4) Consider using pre or post-column adducts to increase signal intensity. "Adduct formation in LC-MS Analysis (esp. ESI)"; https://hplctips.blogspot.com/2011/12/adduct-formation-in-lc-ms-analysis-esp.html
(5) Take a professional training class from the instrument manufacturer in using and optimizing the LC-MS system (esp the software). A one-week long class is usually enough to provide you with a lot of new practical information.
(6) Contact a professional chromatographer in your local area to consult on your specific method. On-site consulting. You will save time and money by having someone with many years (>10) of practical industrial experience in the same application area(s) AND using the same make and model of LC-MS system.
- Remember that it takes on average about ten years of full-time industrial experience to achieve a basic level of proficiency in LC-MS (MS-MS) as this is not something you can learn in a classroom.
Dear William Letter
I have been following you for a couple of years, and I confess that your experience in LC-MS/MS is fascinating. Thank you so much for taking time and replying to this question.
I will consider all of them.
Regards,
Nasim
Dilute and shoot is the most inexpensive and straightforward analysis option that presents a noisy baseline therefore lower selectivity and sensitivity (Even if you choose the ms/ms).
For the best specificity, immunoaffinity SPE extraction of toxins (There are many products on the market, e.g R-biopharm) followed by ms to the n experiment is the best choice (at least MS2). Sensitivity therefore LOQ is adjustable within this procedure (By scaling up or down) but would be costly.