做法
將聚合好的凝膠安置於電泳槽中，小心拔去梳子，加入電泳緩衝液後低電壓10-20V，預電泳20-30min，目的是清除凝膠內的雜質， 疏通凝膠孔徑以保證電泳過程中電泳的暢通。
預電泳後依次加入標準品和待分析樣品。（加樣時間要儘量短，以免樣品擴散，可在未加樣的孔中加入等量的樣品緩衝液避免邊緣效應。樣品一般在1.0mm厚的膠 加樣50-100ug/lane)。
It is really dependent on what gel you are talking about, pro-run for different gels has different purpose. In some case, for instance, SDS PAGE, there may be some residue chemicals in your gel, such as TEMED or ammonium persulfate. Pre-electrophoresis will move those ahead of your samples. Some times, people put some chemicals in the gel, then the pre-run makes the chemical react with something else. At these day, very few people would do pre-electrophoresis to SDS PAGE, but some other electrophoresis may require the pre-run. It really depends.
目的
檢測是否通電，同時根據相應的化學實驗達到其他的一些檢測和預製實驗條件。
