Hey I am about to do a lab to determine the amount of caffeine and sodium benzoate in soft drinks via HPLC. To prepare I had to answer a series of questions before the lab. I am confused on some of them and request your help. The questions are:
Why is it necessary to perform the HPLC separation at a pH of 3? How does the pH affect the separation of caffeine and sodium benzoate?
Predict the elution order for caffeine and sodium benzoate in a reversed phase HPLC used in the experiment?
Why is reverse phase HPLC is being used in this experiment?
At pH=4 what will be the charge if any of caffeine and benzoate?
Can you use an ion exchange HPLC column. If so, what ion exchange would be best?
What is the detection limit for a UV-vis detector?
Why aren't you concerned that the soda is colored or not, unlike the situation for the diode array experiment?
What would happen if I double the length of the HPLC?
When looking at the calibration curve, would I use peak heights pr peak area for accurate results?
Any help would be greatly appreciated.© BrainMass Inc. brainmass.com October 25, 2018, 1:51 am ad1c9bdddf
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Microscale Organic Chemistry Lab Questions
1. Identify four moisture-protected reaction apparatus. I have identified 2 apparatus (Moisture-protected Claisen head with 3 or 5mL conical vial, arranged for syringe addition and magnetic stirring, and Moisture-protected water-jacketed condenser with 3 or 5mL conical vial, arranged for heating and magnet stirring). I may be making this harder than it should be and my question is: Does the Claisen head with 3 or 5mL conical vial constitute two apparatus, as well as the moisture-protected water-jacketed condenser with 3 or 5mL as two apparatus? If so, this would give me the four apparatus requested.
2. What is the basis for distillation techniques used to separate two or more components? I may be way off base, but from what I understand, different distillation techniques are used when substances have different boiling points. Simple distillation techniques can be used where liquid is separated from a nonvolatile solute and the vapor phase consists of only one component. Am I correct in thinking that it needs to be fractional semimicroscale distillation with multiple theoretical plates for two or more components, or am I way off?View Full Posting Details