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I took samples of tapwater in order to examine concentrations of escherichia coli and enterococcus, in a rural area. I was told, by the 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 to the soil and some grains of sand stack 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 was the completion of the sampling. How great is the possibility my sample has a serious contamination of these twο biological pollutants after this incident?

Thanks and sorry for the long story and bad english

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Document the incident and notify your supervisor. For environmental testing where SOP is involved, this would count as an incident, i.e. anything that falls outside SOP. Whether the incident is a non-conformance, deviation or nothing at all is up to your quality team. You can always take another sample, supplies withstanding, too.

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I would say there is a pretty big chance that you sample is contaminated. Maybe by washing most of the bacteria or fungi are removed. It would be very difficult to stick on the lid when you washed it but still. Wash the sampling tap distillate water or just tap water. If so you don't have to worry much normally it has to be free from bacteria. But, At school we did an experiment to demonstrate the present from bacteria in this water and we found bacteria. Because you took it with you and bottle opening isn't sterile. There is a big chance on contamination. But the greatest contamination would probably be the air. I think it's best to not use the data you will gain from this sample. It wouldn't be representative for you experiment. My English isn't that good either so don't worry about that.

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