Sweat content - Beg./End of workout

[hauss]

Is there any difference between the content of sweat from the very beginning of your run and the end of say a 45 min. tough run? If there is a difference, what is it and is the difference greater if you are somewhat inactive the whole week prior to the run as opposed to being in the midst of a strict regimen?

[kniz]

Are you planning on bottling it?

Seriously this is all I could find, but it might answer some of your question.
Peak Performance.

The sweat salt content varies greatly: the better acclimatised players have lower sweat content, but again there is a large individual difference. Sweat salt (sodium chloride) losses can reach almost 10g in a single training session in some players, and this during twice-a-day training. Others lose only small amounts – 2g or less in the same training session.