Sørensen buffer

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The Sørensen buffer is a buffer developed by Søren Sørensen to regulate the pH value . When he first defined the proton concentration of aqueous solutions as a pH value in 1909, he needed pH-stable test solutions for his biochemical research. Using the pKa values, he made a selection of substances, which he stocked in the form of seven stock solutions.

Stock solutions

  1. 0.100 n hydrochloric acid standard solution
  2. 0.100 n sodium hydroxide standard solution
  3. 0.100 molar glycine solution with table salt (7.507 g glycine and 5.85 g table salt per 1.00 liter)
  4. 9.073 g of primary KH 2 PO 4 (anhydrous) (= 0.0667 mol) in 1.00 liter of water
  5. 11.87 g of secondary Na 2 HPO 4 dihydrate (= 0.0667 mol) in 1.00 liter of water
  6. A solution of 19.21 g citric acid (= 0.100 mol) and 200 mL 1.00 N sodium hydroxide solution (= 0.200 mol), made up to 1.00 L with water.
  7. A solution of 12.37 g boric acid (= 0.200 mol) and 100 mL 1.00 N sodium hydroxide solution (= 0.100 mol), made up to 1.00 L with water.

From this he produced the buffer solutions known at the time as “Sørensen buffers” for the pH range 2-13.

Buffer solutions according to Sørensen

Hägg diagram of phosphoric acid - H 3 PO 4 : black; H 2 PO 4 - : purple; HPO 4 2− : blue; PO 4 3− : brown; H + : dashed; OH - : dotted
phosphate buffer application pH 4.9… 8.0
  • Glycine and sodium hydroxide solution or hydrochloric acid
  • Borate and sodium hydroxide solution or hydrochloric acid
  • Citrate and sodium hydroxide solution or hydrochloric acid
  • phosphate

Most of these combinations are only of historical significance today, the glycine buffer and above all the phosphate buffer (e.g. as isotonic PBS ), on the other hand, are still widely used.

Individual evidence

  1. ↑ Ernst Mislowitzer: The determination of the hydrogen ion concentration of liquids . A textbook of the theory and practice of hydrogen number measurements in an elementary representation for chemists, biologists and medical professionals. Springer-Verlag, 2013, ISBN 978-3-642-91971-8 , pp. 299 ( limited preview in Google Book search).
  2. ^ Methods according to Sörensen
  3. ↑ glycine buffer
  4. ↑ phosphate buffer
  5. ↑ Round-robin test in a network of various test laboratories