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SB (Sodium Borate or Sodium Boric Acid) buffer is a agarose gel electropheresis buffer for DNA gels. It has low conductivity and allows for less heat buildup and thus higher voltage and faster runs.


  • Sodium Borate decahydrate (Borax)
  • Boric Acid
  • dH2O


A simple version of this buffer can be easily made as a 20X (100 mM) concentrate.

  • 38.17 g Sodium Borate decahydrate
  • 33 g Boric Acid
  • Bring to 1L with dH2O
  • Dilute to 1X and use to make gel and running buffer.


There are some caveats here. Loading DNA that is in a high-salt solution (some DNA ladders, loading dyes, or restriction enzyme buffers) can increase the local conductivity around the sample and change its running characteristics - meaning that samples in different buffers won't always run at the same speed. The quickest solution here is actually to dilute the sample to the largest volume that you can load in the well.

In addition, one should minimize the amount of indicator dye in the loading dye, as this is a salt and contributes significantly to this problem. Using a fainter dye helps to increase the resolution of these gels.


It should be noted that there are several other "next-gen" electropheresis buffers, notably LA - Lithium acetate, which is touted as being superior in many respects to SB.


  1. Brody JR and Kern SE. Sodium boric acid: a Tris-free, cooler conductive medium for DNA electrophoresis. Biotechniques. 2004 Feb;36(2):214-6. DOI:10.2144/04362BM02 | PubMed ID:14989083 | HubMed [Brody-Kern]
  2. [website]

    "Easy Version"


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