CommentsWhen the syringe is inserted, the needle travels along the needle port tube for about 4.5 cm before it reaches the needle seal. The loop contains only pure sample, undiluted by residual mobile phase. Large loops can produce a large loss of pressure, which takes a longer time to return to normal. This will show if the artifacts are caused by the difference in solvents. The «Comments» section at the bottom of each subject has useful supplemental information.
When the needle is too small in diameter, the seal will not grip it tightly enough. Investigate further to see if the artifacts are oxygen peaks (see Appendix D). Cause C Trace contaminants within the injector are loaded. Flushing after every injection is rarely needed, but if necessary, do it just before the next analysis. It is usually sufficient to flush after every ten or twenty injections.
See the illustration in Symptom 5. In routine operation, remove the syringe after turning to INJECT, but keep the handle in this position so the loop is continuously flushed with mobile phase. Observe the peaks. If the peaks of the second injection are larger and correspond to the retention times of the artifacts, it indicates that the problem is differences in oxygen concentration. You may also want to consider the problem may be caused by a component other than the injector (see Appendix C and Appendix D). Figure 12. Peaks in blank are CARRYOVER from previous sample. Sturdy and accurate, Etatron’s probes are the perfect choice for measuring and regulating your dosing system. Cause B The vent tube(s) is not level with the needle port.