Broad Peaks Possible Causes

In conclusion, the TPD spectra can be characterized by two broad peaks, one at 100° and the other at 450°. However, these could be made up of a combination of several different peaks. Assignments of these individual peaks to specific Pt states are hardly possible, but the broad TPD profile arises out of two possible causes either to structural changes in the Pt crystallite forms or to variation of Pt-alumina interactions due to the heterogeneity of the alumina surface. 

In order to elucidate the role of molecular oxygen on the behavior and mechanism of the dehydrogenation process, the reaction was first studied on CP 0.6/97.1 SA catalyst at temperatures >300 °C in absence of oxygen. In this case, only N2 was used as a carrier gas at a flow rate of 50 ml min V The obtained chromatogram revealed that only the pre-injected cyclohexene was produced at longer retention time where the broad peak obtained ensured its strong adsorption on the catalyst surface. The conversion has been observed only when several O2 pulses were introduced. These observations could indicate that an oxygen flow must be used in the reactant stream in order to prevent possible deactivation of the solid catalyst caused by excessive adsorption of cyclohexene. Here, the reaction may be expected to proceed at lower temperatures as it is facilitated by the pulses of O2 applied. 

You observe that you are going through a lot more reversed-phase columns than you used to and your columns die earlier. Your supplier is not too unhappy, but you would like to know the cause. What does it mean to have a dead column If we exclude higher back pressure, decreased quality means a decrease in the number of theoretical plates (broad peaks, the packing is not OK) and/or a change in retention time (chemical change of the stationary phase). What possible causes should be considered ... 

Regarding resolution peak broadening, and as a result a reduction in the resolution, is possible with larger particles such as 5 pm and/or methanol/water, due to the viscosity. With multiple mechanisms as in the case of EPG or mixed-mode phases, HILIC, charged molecules, isomers etc. peak broadening is probable. In both cases, one is working in the C-term of the Van Deemter equation, the slow kinetics have already caused broad peaks, which even in the gradient mode could be difficult to cope with. 

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