UNIX sort with exponential values?

Question

I have a csv file with 7 fields of data. I want to sort the 7th field in reverse numerial order (smallest values first). The 7th field of data looks like this:

0.498469643137
1
6.98112003175e-10
9.11278069581e-06

I have tried to use the UNIX sort tool like this:

$ sort -t"," -n -k -r 7 <my_file>

The problem I am having is that sort does not recognize exponential form. For example, sort thinks 6.98112003175e-10 is larger than 1. How can I use sort to sort a csv column, but recognize the scientific notation? Thanks in advance for the help.