so sometimes things happen that um some things happen to the chromatograph that um result in band of bragging so in reality chromatographic peaks are generally broader than would be expected solely from the random nature of migration but sometimes we see things that happen that result in a different shape or elongation to that chromatographic peak so the first one is what's known as multiple pathways or any diffusion and so in any diffusion what happens is so here's your flow that sometimes one species might take a short path through the comment on the stationary phase the packing the stationary phase and the second one might take a completely different path well based on the fact that you're going to have different paths going to the stationary phase the result of when a and b come off the column may be incorrect because it's just a result of the path they took versus their actual affinity to the stationary phase so this type of broadening is independent of flow rate it doesn't matter what kind of flow rate you have and it's always going to be something that could result in either broadening of the peak or shifting of the peak another type is what's known as longitudinal diffusion and so here longitudinal diffusion you'll notice that it's going to depend on your flow rate so t equals zero so if we have a quick flow rate through you're going to get a very sharp peak if you have a very slow through you're going to get a very broad peak and depending on where that intermediate is will give you the intermediate size peak so this type of broadening is proportional to the inverse flow rate so the faster the flow rate the narrower the peaks going to be or the faster the flow the sharper those peaks are going to be so this is a fast flow here and you get a very sharp peak so this side is proportional to the inverse fluoresce you kind of have to manage or figure out what is the best flow rate you could have the third type is what's known as finite rate of mass transfer and so here is your ideal mobile phase stationary phase it comes through here's your mobile phase your stationary phase here's a result in reality what you see here is at the front end of the sample zone the solute and mobile phase encounter fresh stationary phase but equilibrium is not yet established and so here it meets there and here's your moa phase stationary phase and as a result of that you can get this broad mean you see right here therefore the solute is carried further down the column than expected and then as it's carried further down the column you're going to get some type of broadening and shifting from that at the rear end of the sample zone the solutes in the stationary phase encounter fresh mobile phase but the rate of transfer of the solute back into the mobile phase is not instantaneous so that's this broad mean right here therefore the tail of the sample zone is more drawn out than expected the result is band bronzing at both ends of the peak and so you get this widening of the band right there this type of broadening is proportional to fluorite so you may look at this and say well why does it matter if it's elongated in both sides why does that matter the issue comes in for separation purposes is if your a and b species are very close together and both of them broaden like this you may not get a distinction between the two and you may not be able to see both of your peaks that are present