Hey Gerry, 1) Use 700 C quartz chips in the reduction furnace 2) Look in and see if the insert puts the sample in the hot zone for your column 3) Check that unburned molten metal isn't plugging column 4) Run much less (<10) samples per insert I hope these help. John John Furey Physical Scientist US Army ERDC EP-P 3909 Halls Ferry Rd Vicksburg, MS 39180 (601)-634-2778 (601)-634-4002 fax [log in to unmask] -----Original Message----- From: Stable Isotope Geochemistry [mailto:[log in to unmask]] On Behalf Of Gerard Olack Sent: Friday, January 13, 2006 9:01 AM To: [log in to unmask] Subject: [ISOGEOCHEM] sulfur burning issue HI All-- I switched our EA, Costech ECS 4010, over to sulfur mode (tungstic oxide oxidation column, pre-packed from Costech, teflon tubing, 2m GC column), and can't seem to get the SO2 to come out in a single peak. Organic material, sulfanilamide or ground fish, gives two main peaks--a sharper early one at ~400 sec and another one (or more) broad one around 550 sec. Both sulfides and sulfates (with added tungstic oxide) only give the latter broad peak(s), regardless of sample size or added organic material. The early peak is similiar to the what I was getting the last time I ran sulfur (sulfides, sulfates, some sulfanilamide). I've changed the transfer lines a couple of time (now bypassing Costech detector plumbing), cranked the hotplate under our conflo up, have the GC running at 110 (highest temp setting), swapped drying tubes, and have been playing with drop timing and oxygen amounts. I'll be swapping the ash collector and having at it again--but I would appreciate any suggestions. Also are their any particular pitfalls to watch out for when running organic samples? We're running ~8mg for the fish to get a reasonable signal (or what will be reasonable once we get a fairly clean peak). thanks in advance-- take care gerry p.s. I was playing with PEEK tubing in place of teflon (lower gas permeability than teflon, don't heat gun PEEK). It seemed ok in initial tests last time around, but it was one of the first items that got swapped out this time. It's more expensive than teflon/PTFE tubing, but it may be a viable option if you require lower gas backgrounds.