Org Prep Daily

December 2, 2009

Predetermined conclusions

Filed under: Uncategorized — milkshake @ 6:56 am

In the last year of elementary school I got encouraged to take part in the science fair – The top winners of the national highschool science project competition could possibly earn the admission to a college of their choosing. I was a new chemistry club member and it was decided there that I ought to try an analytical chemistry project –  an assay to determine content of vitamin C in various foods by titration. There is a simple redox method and I could compare how the processing and contact with metals diminished the ascorbic acid content. (Cooked food has less ascorbic acid because it gets oxidized and metals catalyze the oxidation etc. etc.)

So I started on this stuff but it bothered me a bit when I was reading in the book that described this analytical method that there are actually other components  in the food that also have reducing properties and they would show up in this titration and I had no way of telling them apart from ascorbic acid or figuring out their relative ratio – so my result would always end up higher, as a sum of two unknown values. The club boss suggested that I should not dwell on this over too much –  after all, it was an established method and I was only doing a modest experimental work to practice for more serious research – and that I ought to get on with the work for which she had the plan laid out for me. So I listened and did the whole thing.

Next, before I even completed writing up the ascorbic acid stuff – and since we were working so well together – the chemistry club boss suggested that the second project I should try is to measure lead in fruit picked from trees growing along the roads because of the health issues posed by the wide-spread use of leaded gasoline at that time. There is dithizone, a ligand that makes a deep purple complex with lead and she had a spectrophotometer in the lab which she wanted to put to some use and it would be much more interesting project – one that had a chance of winning awards for our club…

A small problem arose when I finished the calibration curves for the dithizone-lead complex standards and proceeded to apples picked from trees along a busy road:  it turned out that there was not much lead in those apples (I could barely detect a hint of the colored complex but there was no way to quantify that on this instrument). I got promptly sent out on missive to try to find some more-contaminated fruit so that we can have material to support our serious study –  I was told to make sure to pick the fruit only when there was no rain for few days, and that I should prepare the samples from the surface layer only. (How exactly you separate the surface in a reproducible way was not obvious to me – but reproducibility was apparently not the biggest concern in our project). When I asked if this really was the way to go about the  sample collection, it was made clear to me that I better find some lead-laden fruit somewhere soon or she will not waste her time with me anymore. So I stopped attending that chemistry club and resumed my research on home-made fireworks and rockets and methods for  ethanethiol production – the projects in which I found some encouragement from my non-chemist buddies.

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