i tried running my protein over a SEC column (sephacryl 300) and something went wrong cause now the column, when i remove it from the chromatogram, drips buffer out of the top of the column. since there is no injected flow, why is there buffer coming off in a reverse flow? could air bubbles trapped in the column prevent buffer from moving down the column and the blow back is due to the buffer only being able to move so far? i would think the pressure would drastically increase if this was the case and this does not happen. any suggestion would be beneficial. thanks