DNA gel loading buffer is intended to be mixed with samples containing DNA in order to facilitate loading of the samples into the wells of horizontal and vertical agarose and polyacrylamide. The 10X gel loading buffer is composed of 0.21% Bromophenol Blue, 0.21% Xylene Cyanol FF, 0.2M EDTA, pH 8.0 and 50% glycerol in molecular biology grade water. The 6X gel loading buffer is composed of 0.03% Bromophenol Blue, 0.03% Xylene Cyanol FF, 60mM EDTA, pH 7.6 and 60% glycerol in molecular biology grade water.
EDTA in the buffer terminates the reactions containing enzymes that require magnesium or calcium. The addition of 1 volume of DNA gel loading buffer to 9 or 5 volume of sample increases the density of the sample and gives it colour, thus facilitating loading. In addition, the two dyes migrate in the same direction as the nucleic acids, serving as rough indicators of the electrophoretic progress.
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