HiJohn, we had just this problem last year, at last this was solved only by baking for more time. Maybe you can try, baking continually the capillaries,every time less than 10 minutes. cheers zengjie *********************************************** Zengjie Zhang Assistant Professor The Open Research laboratory on Isotope Geology Chinese Academy of Geological Sciences 26 Baiwanzhuang Road, Beijing 100037, China 86-10-68999635(lab) 86-10-68999094(O) [log in to unmask] Question Is Everything <br><br><br>>From: J T Hill <[log in to unmask]><br>>Reply-To: Stable Isotope Geochemistry <[log in to unmask]><br>>To: [log in to unmask]<br>>Subject: [ISOGEOCHEM] Contamination on 253<br>>Date: Mon, 25 Jul 2005 16:51:16 +0100<br>><br>>Hiya All<br>><br>>Does anyone have experience of cleaning the capillaries and <br>>change-over<br>>valve on a 253/Kiel?<br>>We think we have a contamination problem as the internal precision <br>>and<br>>delta value are OK for a time then there are "bursts" in which the <br>>value is<br>>erroneous by up to almost 1 per mille each way. This is for carbon <br>>or<br>>oxygen and sometimes both. We think the instrument itself is OK as <br>>the<br>>system stability tests check out. The problem may be due to <br>>phosphoric acid<br>>finding its way into the capillaries and or contamination from bulk <br>>samples<br>>from the Kiel. Baking these parts for a few hours has made no <br>>difference.<br>>If contamination is the cause, we shall have to clean the <br>>capillaries and<br>>changeover block and valves. We can probably arrange an HPLC pump to <br>>pump<br>>liquid through the capillaries and we have ultrasonic baths. The <br>>expense<br>>of simply replacing all these parts is so great that we would prefer <br>>to<br>>decontaminate the existing parts if possible.<br>><br>>Regards<br>><br>>John<br>><br>><br>><br>>John Hill<br>>Mass Spectrometry Facility<br>>University College London<br>>Chemistry Department<br>>20 Gordon St.<br>>London<br>>WC1H 0AJ<br>><br>>Tel: 020 7679 4605<br>>Fax: 020 7679 7451<br>>Mobile: 07956 924058<br> _________________________________________________________________ 享用世界上最大的电子邮件系统— MSN Hotmail。 http://www.hotmail.com