[crushedcorn]

I had to design an experiment to extract BPA from water stored in different types of plastic containers. I used these procedures and didn't obtain anything in week 1, so I'm hoping someone can tell me if there is any type of issue with my experimental procedures. Here is what I wrote for the method section of my research paper:

A #3 plastic bottle, a #1 plastic bottle, and a glass jar were filled with distilled water, capped, and sealed with a thin strip of paraffin to prevent evaporation. The containers were then stored in a dark, cool cabinet for one week before being tested for the presence of BPA.

1) 40mL of water from one of the containers was measured into a graduated cylinder and poured into a separatory funnel. Then, 5mL of dichloromethane and 5mL of anhydrous sodium chloride were added to the funnel to extract the BPA.
2) The contents of the funnel were gently mixed, stopping occasionally to vent, until two distinct layers formed. The bottom organic layer was dispensed into a clean pre-weighed flask.
3) Two additional extractions were made with 3mL each of dichloromethane and anhydrous sodium chloride and the organic layer was dispensed into the same flask.
4) Magnesium sulfate was added to the flask to dry the solution until the “snow globe” effect was obtained. The solution was then poured into a funnel fitted with a piece of fan-folded filter paper.
5) In the fume hood, the filtrate was gently warmed over a Bunsen burner and dried with a mild stream of air.
6) The flask was then weighed and the weight of the sample obtained was used to determine the molarity of BPA in the bottle of water.

The above procedures were repeated for all containers at week one.

Notes: Dicholoromethane was chosen to extract BPA based on previous lab work done on this topic.

Thanks for any feedback!

[Arkcon]

What any good experiment needs is a positive control.  I suppose that would be a spiked sample, to be certain that your procedure is adequate to extract BPA, and the extracted sample survives the procedure.  So that's something you might want to work on.

Query: how much BPA is in these bottles?  Do you know?  How much is used to make them, and how much is theoretically?  How much can water extract? How much can you detect? If you spike that amount + (I dunno) 10% into water, take it through your procedure how much BPA is detectable?  Is BPA lost in your procedure?  Is BPA added by the Parafilm^TM (I assume you're using that, and not really strips of parafin) covering?

[crushedcorn]

A positive control is a great idea. Unfortunately, it's not something I can get my hands on.

As for the bottles I'm testing, I have no idea how much BPA they have or if they have any at all. I did some research that said that bottles with recycle numbers 3 and 7 contain BPA, but my test on bottle #3 was fruitless. My partner and I are using disposable plastic water bottles that can be bought from a gas station or vending machine, so I also don't know how much BPA they should have theoretically or actually.

You bring up a lot of great questions that I didn't even consider. I may not be able to speak to them all in my project but they are points I'm going to try to dive into in my discussion. Thank you!