Chromatography Quiz #23 Results
Pickering Labs would like to congratulate our winners of our last newsletter’s AAA quiz: Wanda Ingersoll from Mississippi Public Health Lab, David Green from Pepperdine University Natural Science Division, Narjes Ghafoori from LA County Environmental Toxicology Lab, and Helene Lachance from Shur-Gain Nutreco!
They have each won and will shortly be receiving: a Bose SoundLink Color Bluetooth Speaker! A lightweight-compact wireless speaker in a stylish-vibrant color! Connect to any bluetooth device and take your tunes to go! We hope our quiz winners enjoy their prizes for the remainder of the summer and beyond!
Thank you all for your submissions!
The correct answer to the Polyether Antibiotics Analysis quiz:
It was beautifully answered by one of our winners. Here is their response:
Multiple Choices:
A) Bad lamp
B) Reference Wavelength
C) Sampling rate
D) All of the above
“This appears to be a really bad choice of reference wavelength. The vanillin absorbs like crazy from 200-350 nm. At almost 60g/L the reference absorption will be topped out at >4AU. No DAD detector I know of can handle this. The noise is simply the remaining electronic noise from the 360 nm (plus bandwidth) diodes on the array. The solution is to move the ref wavelength out to, say, 600 nm since the antibiotics probably don't absorb there or, better, turn off the ref wavelength, acquire and store whole spectra, and do post-processing after the analysis when a clear region of the spectrum can be found.”
Chromatography Quiz #24: Glyphosate Peak Shape
What caused the bad Glyphosate peak shape in the troubleshooting (red) chromatogram below? Simply email your answer as well as your full contact information to Rebecca at rlsmith@pickeringlabs.com by October 1st, 2016 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).
Glyphosate Analysis – Bad Peak Shape
Pinnacle PCX post-column instrument is being used, in a traditional HPLC setup as recommended by Pickering Laboratories. The reference (blue) signal and troubleshooting (red) signal are overlaid in the chromatogram below. The quiz question: what is causing the bad peak shape?
Hint: Please assume the same reagent, column, and method are being used for both chromatograms.
Normal/reference post-column conditions for glyphosate analysis:
Reagent 1: GA116 – hydrolysis reagent
Reagent 2: GA104 with OPA and Thiofluor
Reactor: 36 °C, 0.5 mL
Reagent flow rate: 0.3 mL/min
Injection volume: 100uL
Glyphosate analysis does not utilize Hydrolysis reagent; Hypochlorite solution should be used as Reagent 1. If the correct reagents are used, the poor peak shape could be caused by the failure to add bleach (or adding the incorrect amount of bleach) to the Hypochlorite solution.