[Sabine86]

Hi,

I ' ve already tried twice to do a Phospholipid-Assay (Stewart), i.e. to establish a standard curve for Phosphatidylcholin, but it hasnt worked yet. That means macroscopically it looks fine, because the lower chloroform layer  gets the more red the higher is the content of PC. But I can't confirm this result by measuring it at 488 nm. Do someone know what could be the reason for that?

These are my values (without a background value measured). For each content I made up  two approaches with the same µg PC.

Content of PC per tube: Extinction approach 1 // Extinction approach 2
0 µg: -2,912 // -2,41
10 µg: -3,22 //-1,9
25 µg: -3,01 // -1,8
50 µg: -2,9 // -0,93
75µg: -2,74 // -2,95
100µg: -2,89 // -2,79

I'd be very glad about an answer!

[Arkcon]

Try to generate a chart from your table of values using a spreadsheet/charting program and see if you can see a trend.  Your numbers seem to be all over the place, but there may be a trend to see where you're going wrong.  Perhaps you're saturating your optical instrument, or something like that.