Chromatography Quiz #30

Chromatography Quiz #29: Amino Acids Elevated Baseline – RESULTS

Pickering Labs would like to congratulate all of our winners for our previous newsletter’s Elevated Baseline Amino Acids Chromatogram: Tom Schneider from Suffolk County Water Authority, Narjes Ghafoori from LA County Environmental Toxicology Lab, and Dr. David Green from Pepperdine University!

Winners will soon receive: A Harvest Bundle of Gifts from!

This bountiful harvest bundle includes: creamy Pumpkin Cheesecake, a beautiful Autumn Garden Party plant gift, and a Pumpkin-Shaped Gift Basket which features juicy pears, pumpkin bars, cranberry relish, and much more. It’s the perfect way to celebrate the changing of the seasons. Best of all, bundle gift items are sent individually to make the celebration last a little longer!

Congratulations to our quiz winners and we hope they look forward to receiving their gifts next week!

Thank you all for your submissions!

The correct answers for the Elevated Baseline Amino Acids Chromatogram are as follows:

The shift on the baseline is called an ammonia plateau and it is due to the presence of low-level amines and ammonia in the buffers. These compounds accumulate on the column during equilibration time and come out during the gradient in a form of a plateau. Since the buffers have low pH, these compounds are unavoidable but care should be taken to avoid excessive contamination that can cause the plateau to be too high. Amines are present even in the air and get dissolved in buffers as time goes by.

The issue usually comes from buffer A. Try and replace with a new lot if possible.

Below are some tips on how to minimize any potential problems:

  • Remove all filters from the ends of HPLC lines that go into the buffer bottles. All our products are filtered before bottling and these in-line filters only drag contamination from one bottle to another.
  • Replace open buffers on the instrument at least every two weeks. If you don’t use the full bottle in 2 weeks, pour half of the bottle into a clean glass bottle to put on the instrument and tightly cap the remaining portion to keep until future use.
  • Don’t flush column with water, use only Column Regenerant for cleaning the column.
  • Don’t use the first injection of the sequence for calculations since it usually has a different profile due to differences in equilibration time.
  • Program the needle wash between the runs to avoid carry over.
  • If you see unexpected peaks on your blank or other chromatograms make a fresh vial of the solution and run again to confirm the problem. Also run “No Injection” to see if the peaks are coming from the injected sample of from the baseline.
  • Flush HPLC periodically with 100% water, then 100 % methanol, then 100 % water with no column attached (!!!) to keep the lines clean.

Chromatography Quiz #30 – Aflatoxins Analysis, Decreased Signal:

Simply email your answer as well as your full contact information to Rebecca at by December 21, 2018 in order to win. You will receive email confirmation that your submission has been received. The answer to the quiz and winner congratulations will be published in the next issue (to be anonymous, please notify Rebecca in submission).

Aflatoxin analysis by photochemical derivatization is achieved with the parameters listed below:

Analytical Column: Mycotox Column, C18 4.6x250mm
HPLC Eluent: Sodium Phosphate buffer PN 1700-1108/Methanol/Acetonitrile (57/28/15)
Flow Rate: 1 ml/min
FLD: Excitation 365nm, Emission 430nm
UVE Photochemical reactor with 254nm UV light: 1.0ml knitted reaction coil.


What could contribute to a decrease in signal?