I have a question regarding the Los Gatos water isotope analyzers. We have a EP45 model and used it for almost 3 years. Last year we had a crack in one of the mirrors and had it exchanged by service. Since then we had some times where it worked, but usually it does not work properly. We get a lot of 17SD-errors, the Voltage in the detector curves is lower than it used to be and we get PRES errors some of the time, especially if we try to inject more volume. The precision of the instrument has decreased dramatically. We tried the usual service procedures, contacted Los Gatos Research and basically were given similar instructions to perform the standard maintenance procedures - exchange dririte, clean tubes, clean injector block, use a new syringe etc... but the problem remains.

What else can we try? In my opinion the 17SD error is just an indication of the low precision of the instrument in general. The low precision probably is a result of the lowered laser transmission, indicated by the lower detector voltage (which leads to less pronounced absorption peaks). Service told us, that apparently the "ring down time" has decreased. The way I interpret the whole situation is, that the length of the laser beam in the chamber is not as long anymore, or there is some absorption of the beam within the chamber. Does this make sense and what could be the cause of this?

Many thanks

Dr. Anja Wunderlich
TU Munich, Faculty of Civil, Geo and Environmental Engineering (Hydrogeology)
Arcisstr. 21, 80333 Munich, Room 1411
(take the entrance across Luisenstr. 45)
Telephone (office): +49 (89) 289 - 25861
Telephone (lab): +49 (89) 289 - 25828
Fax: +49 (89) 289 - 25841