Abstract
Chemical and biochemical processes can be significantly altered by small variations in the pH of the medium, so that many experimental studies require effective means to control this parameter. There are mechanisms that allow the pH control of aqueous solutions when adding (small) amounts of strong acids or strong bases to the chemical system. These solutions, known as buffer [1], are composed of a mixture of a weak acid salt with a strong base and its respective weak acid (eg sodium acetate / acetic acid) or a weak base salt with acid strong and its respective weak base (eg ammonium chloride / ammonia). The concept of a buffer was proposed in the early twentieth century and has been studied ever since. Note that the main purpose of a buffer is to control the pH of the solution, but it can also perform secondary functions, such as controlling the ionic strength of the reaction medium. According to the theory proposed by Brønsted and Lowry [2-5], they should be seen only as mixtures of conjugated acids and bases that minimize the pH variations of an aqueous solution through the effect of the common ion. This text hopes to give a broader and more critical view of acid-base buffers
References
- Fiorucci AR, Soares MHFB, Cavalheiro ETG. O conceito de solução tampão. Química Nova na Escola, 2001, 13: 18-21.
Disponível em http://qnesc.sbq.org.br/online/qnesc13/v13a04.pdf
- Brønsted JN. The conception of acids and bases. Rec. Trav. Chim., 1923, 42: 718-728.
-Lowry TM. Chem. & Ind., 1923, 42: 43.
-Brønsted JN. Acid and basic catalysis. Chem. Rev., 1928, 3: 231-338.
- Andrade JC de. Química analítica básica: os conceitos acido-base e a escala de pH. Revista Chemkeys [Online], 2010, 1(1): 1-6.
Disponível em: https://econtents.bc.unicamp.br/inpec/index.php/chemkeys/article/view/9642
doi: 10.20396/chemkeys.v0i1.9642.
- Po HN, Senozan NM. Henderson-Hasselbalch Equation: Its History and Limitations. J. Chem. Educ., 2001, 78: 1499-1503.
- Butler, JN. Ionic Equilibrium: a Mathematical Approach, Addison-Wesley Publ. Co., 1964.
-Andrade JC de. Química analítica básica: o comportamento ácido-base em solução aquosa. Rev. Chemkeys [Online], v.1,2019, e019001
Disponível em: https://econtents.bc.unicamp.br/inpec/index.php/chemkeys/article/view/9847
doi: 10.20396/chemkeys.v1i0.9847.
-Lewis GN, Randall M. The activity coefficient of strong electrolytes. J. Am. Chem. Soc., 1921, 43: 1112 – 1154.
-Debye P, Hückel, E. The theory of electrolytes. I. Lowering of freezing point and related phenomena. Physik. Z., 1923, 24: 185–206.
-Kielland J. Individual activity coefficients of ions in aqueous solutions, J. Am. Chem. Soc., 1937, 59: 1675-1678
-Andrade JC de. Química analítica básica: equilíbrios iônicos em solução aquosa. Rev. Chemkeys [Online], 2009, 9(3):1-13.
Disponível em: https://econtents.bc.unicamp.br/inpec/index.php/chemkeys/article/view/9647
doi: 10.20396/chemkeys.v1i0.9647
- van Slijke DD. On measurements of buffer values, J. Biol. Chem, 1922, 52: 525-590.
- Stoll VS, Blanchard JS. Buffers: Principles and Practice. Methods in Enzymology, 1990, 182: 24-38.
- Bassi, ABMS. Quantidade de Substância. Rev. Chemkeys [Online], 2005, 9(2)1-13.
Disponível em: https://econtents.bc.unicamp.br/inpec/index.php/chemkeys/article/view/9635
doi: 10.20396/chemkeys.v0i9.9659
- Andrade JC de, Custódio R. Quantidade de Matéria e Concentração. Rev. Chemkeys, [Online], 2000, 3(8): 1-3.
Disponível em: https://econtents.bc.unicamp.br/inpec/index.php/chemkeys/article/view/9648
doi: 10.20396/chemkeys.v0i3.9648
- American Society for Testing and Materials, ASTM. Standard test method for pH of aqueous solutions with the glass electrode. Item 6.3: Preparation of pH Buffers, ASTM E70 -19 (2019).
- Durst, RA. Standard Reference Materials: Standardization of pH Measurements. NBS SPECIAL PUBLICATION 260-53, 1975, 39 pp.
- Buck RP, Rondinini S, Covington AK, Baucke FGK, Brett CMA, Camões MF, Milton MJT, Mussini T, Naumann R, Pratt KW, Spitzer P, Wilson GS. Measurement of pH. Definition, Standards and Procedures (IUPAC Recommendations 2002). Pure Appl. Chem., 2002, 74: 2169–2200.
- Robinson HW. The influence of neutral salts on the pH of phosphate buffer mixtures. J. Biol. Chem., 1929 82: 775-802.
- Green AA. The Preparation of Acetate and Phosphate Buffer Solutions of Known pH and Ionic Strength. J. Am. Chem. Soc., 1933, 55: 2331-2336.
- Bates RG, Acree SF. pH of aqueous mixtures of potassium dihydrogen phosphate and disodium hydrogen phosphate at 0 to 60 oC. (Research paper RP1648). Journal of Research of the National Bureau of Standards, 1945, 34: 373-394.
- Elving PJ, Markowitz JM, Rosenthal I. Preparation of buffer systems of constant ionic strength. Anal. Chem., 1956, 28: 1179-1180
- Paabo M, Bates RG, Robinson R A. Buffer solutions of potassium dihydrogen phosphate and sodium succinate at 25°C. Journal of Research of the National Bureau of Standards. 1963, 67A: 573
- https://www.aatbio.com/resources/buffer-preparations-and-recipes/ - acessado em 28 de fevereiro de 2020.
- http://delloyd.50megs.com/moreinfo/buffers2.html - acessado em 28 de fevereiro de 2020.
Outras referências didáticas:
Thomson BM, Kessick MA. On the preparation of buffer solutions. J. Chem. Educ., 1981, 58:743-746
Silva CR, Simoni JA. Avaliação da capacidade tamponante - um experimento participativo. Química Nova, 2000, 23: 405-409.
Buckley PT. Preparation of buffers: an experiment for quantitative analysis laboratory. J. Chem. Educ., 2001, 78: 1384.
Pergantis SA, Saridakis I, Lyratzakis A, Mavroudakis L, Montagnon T. Buffer squares: a graphical approach for the determination of buffer pH using logarithmic concentration diagrams. J. Chem. Educ. 2019, 96: 936−943.
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