I took samples of tapwater in order to examine concentrations of Escherichia coli and enterococcus in a rural area. I was told, from an analytical lab, to take samples in four sterilized vessels bought from pharmacy.
The problem is that at the completion of the last vessel, its cap fell frοm my hand down into the soil and some grains of sand were stuck on the inner surface of the cap. As fast as I could I picked it up and washed it off totally with the water of the sampling tap. After that I closed my last sampling vessel with it and this is the completion of the sampling.
How large is the possibility my sampling has a serious contamination of these twο biological pollutants after this incident?