Chromatography Quiz No. 11

Chromatography Quiz #10 Results

We would like to congratulate the grand prize winners of our last newsletter’s Amino Acids Analysis (hardware problem) Chromatography Quiz: Hélène Lachance from Shur-Gain Nutreco in Canada, and Narjes Ghafoori from the LA County Environmental Toxicology Laboratory!!!

They have each won and will be receiving: a Google/Asus Nexus 7 Tablet!  We would like to thank all of you for your submissions.

The correct answer for the modified Amino Acids chromatogram: There was a bubble trapped in the LC Pump head.  Similar noisy baselines could be caused by any of the following: bad pump seals, bad check valves, scratched or damaged pump pistons, faulty pulse dampener, or problems with connections to the pump.  Post-column systems containing reciprocating pumps can also cause noisy pulsations in the baseline, and the frequency of the sine waves should be evaluated to determine which pump is causing the noise. 

This problem can also be caused by dirty reagents or eluents, however in this case the pulsations would be accompanied by the elevation of the background signal. 

Thank you!
Pickering Labs

Chromatography Quiz #11:

Identify the error made when running the Glyphosate chromatogram below and win a prize!  Simply email your answer as well as your full contact information to Rebecca at by January 31, 2013 in order to win.  You will receive email confirmation that your submission has been received.  The troubleshooting answer and winner congratulations will be published in the next issue (to be anonymous, please notify Rebecca in submission). 

Glyphosate Analysis for US EPA Method 547

Pickering Standard: Glyphosate Test Mixture 1700-0080, 2.5 ug/mL, 10 µL injection 

Pickering Column: 1954150 Cation-exchange Column for Glyphosate Analysis,
4 x 150 mm

Normal Operating Conditions: (for reference only, condition changes may be reflected in chromatogram)

Column Temperature: 55 °C

Flow rate: 0.4 mL/min

Eluent Gradient:

TIME K200 RG019 %
0 100 0
15 100 0
15.1 0 100
17 0 100
17.1 100 0
27 100 0

Post-column conditions for pesticide analysis:

Reagent 1: Oxidizing reagent – 100uL of 5% Sodium Hypochlorite in 950mL of GA116

Reagent 2: 100 mg of OPA, 2 g Thiofluor™ in 950 mL of GA104

Reactor 1: 36 °C, 0.5 mL

Reactor 2: ambient. 0.1 mL

Reagent flow rates: 0.3 mL/min

Detection: Fluorometer ex 330 nm, em 465 nm


Note: A special thanks to Michael Pickering for the suggestion and for providing the “old school” chromatograms (notice the chart reader font on the retention times)!



One thought on “Chromatography Quiz No. 11”

  1. The problem is heavy metal contamination in the column or the mobile phase.. This could lead to the tailing that is seen in the top chromatogram. This could also be caused by a contaminated guard column or an older analytical column that needs to be replaced.

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