how to store an approximate number? (number is too small to be measured)-Collection of common programming errors

I have a table representing standards of alloys. The standard is partly based on the chemical composition of the alloys. The composition is presented in percentages. The percentage is determined by a chemical composition test. Sample data.

But sometimes, the lab cannot measure below a certain percentage. So they indicate that the element is present, but the percentage is less than they can measure. I was confused how to accurately store such a number in an SQL database. I thought to store the number with a negative sign. No element can have a negative composition of course, but i can interpret this as less than the specified value. Or option is to add another column for each element!! The latter option i really don’t like. Any other ideas? It’s a small issue if you think about it, but i think a crowd is always wiser. Somebody might have a neater solution.

Question updated:

Thanks for all the replies.

• The test results come from different labs, so there is no common lower bound.
• The when the percentage of Titanium is less than

Originally posted 2013-11-09 20:45:35.