You might expect that if you rubbed a makeup that is 5% lead onto your skin that it would make you ill immediately. Having stood in my lab, measuring how much lead passes through pigskin, I can tell you that this is not the case. If lead passes through, it will take hours. This week, my experiments have run for sixteen to twenty-four hours.
We are measuring concentrations in the part per billion range in the bottom of the Franz cell. My experiment is ruined if ten nanograms of lead get into the bottom system. Given that the top side of the skin in the upper Franz cell is painted with at least ten million times more lead than this, it makes the experiment challenging.
Starting and stopping a Franz cell experiment takes me about one to two hours. Most of this time is spent cleaning. I am trying to eliminate lead contamination. I wash and rinse the inside of the Franz cells using distilled water at least six times before an experiment. I wash the tops thoroughly with water and alcohol. I re-assemble everything with fresh gloves. I fill the bottom cell with ultraclean saline. I place washed pigskin on top.
Of course, I then pipette a 5% lead makeup into the top of my beautiful clean experiment. I go away for a day. I pray that there isn’t a tiny hole in the skin. When I come back, I decant the saline into a clean vial and send it off to a specialty lab for analysis. I wash the Franz cells.
The skin absorption experiment really is wash, rinse, repeat.
This is amusing for my family because I have always hated doing the washing up. I will do any other chore instead. Here I am, now doing very nitpicky washing up for hours in my lab.
There are some parts of a science career that are tedious. Washing Franz cells is not a fun time for me. However, there are such joys in discovery! The things I find out make it all worthwhile.
I cannot wait to get last week’s results back. I so hope the experiment worked. If it did, we will be the first people to truly know how dangerous a particular white lead makeup was. How fantastic and amazing is that?