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Presentation on Buffer

This document discusses buffers, their types (acidic and basic), mechanisms of action, and their applications in pharmaceutical preparations, laboratories, and industrial processes. It highlights the importance of maintaining pH balance in biological systems and details various buffer compositions and their uses. Key features of effective biological buffers and the role of proteins in buffering are also summarized.

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BUFFER Presented by- Rubina Roy Assam University, Silchar
INTRODUCTION  A buffer is a compound or mixture of compounds which when present in a solution resists changes in pH upon the addition of small quantities of acid and bases.  Buffer systems follow Le-Chatelier’s Principle.  Buffers are significant in maintaining pH of living system. Image source: Chemed.chem.purdue.edu
TYPES OF BUFFER Buffer Acidic Buffer Basic Buffer (combination of weak acid & its salt with strong base) (combination of weak base & its salt with strong acid) CH3COOH/CH3COONa NH4OH/ NH4Cl H3PO4/ NaH2PO4 NH3/NH4Cl
Buffer Action Mechanism of action in acidic buffer • Let us consider a buffer system of CH3COOH & CH3COONa. • CH3COOH CH3COO- + H+ • CH3COONa CH3COO- + Na+ Adding small amount of acid Adding small amount of Base (HCl) (NaOH) HCl H+ + Cl- NaOH Na+ + OH- H+ + H2O H3O+ H3O+ + CH3COO- CH3COOH + H2O OH- + H3O+ 2 H20 Image source: Chemguide
Mechanism action of basic buffer • Let us consider a buffer system of NH4OH & NH4Cl. • NH4OH NH4 + + OH- • NH4Cl NH4 + + Cl- Adding small amount of base Adding small amount of acid (NaOH) (HCl) NaOH Na+ + OH- HCl H+ + Cl- OH- + NH4 + NH4OH H+ + H2O H3O+ H3O+ + OH- 2H2O Image source: Chemguide
Hendersen-Hasselbalch Equation Buffer Equation Acid Buffer Basic Buffer (CH3COOH) (NH4OH) CH3COOH CH3COO- + H+ NH4OH NH4 + OH- Weak acid salt weak base salt Ka = Kb = [H+] = Ka [OH-]= Kb -log [H+] = -log Ka –log -log [OH-]= -log Kb - log pH = pKa – log pOH = pKb – log pH = pKa + log pOH = pKb + log So, pH = pKa + log pOH = pKb + log
Buffer Capacity • Buffer capacity is the efficiency of a buffer solution to resist pH change on addition of small amount of acid or base. • Buffers can resist pH change upto ±1 unit of its buffering zone. • Buffering capacity = Fig. Titration Curves of Different Buffers Image source: www.bioinfo.org
Applications of Buffer In Pharmaceutical Preparation – To adjust the pH of drug and medicine , in order to minimize drug degradation & to improve patient’s comfort – The drugs applied through injections are maintained at an ideal pH of 7.4 (as that of blood) – Buffers used in injections are acetate, phosphate, citrate, etc. – Buffers like borate, carbonate, phosphate are used in ophthalmic preparations to maintain the pH of the medicine within the pH range of lacrimal fluid (7-8). In Laboratory To callibrate pH meter for determination of pH of water, soil, food and other samples To carry out various biological research such as DNA & RNA isolation, protein crystallisation. In Industrial Preparation To ensure stability of ointments and creams on applied areas like skin To set up appropriate conditions for dyeing fabrics To set up appropriate conditions for fermentation process in food production
List of Commercial Buffers Name Composition pH Range Use Phosphate Buffer Sodium Phosphate Dibasic + Sodium Phosphate Monobasic + Distilled water + HCl /NaoH 6.36-7.36 Ophthalmic preparations, biological research Citrate Buffer Citric acid + Sodium Citrate + distilled water + HCl/NaoH 3-6.2 Pharmaceutical preparations, biological research, RNA isolation Acetate Buffer Sodium acetate + Acetic acid + distilled water + HCl/NaoH 4.26-5.26 Purification & precipitation of nucleic acids, Protein crystallization Carbonate-Bicarbonate Buffer Sodium Carbonate + Sodium Bicarbonate + Distilled water + HCl 9.2-10.6 Used in protein-coating in Enzyme Immunoassay (EIA) technique, Dairy product preservation Tris-acetae-EDTA Buffer (TAE) Trisaminomethane + EDTA + Glacial Acetic acid + water + HCl 8-8.5 DNA & RNA extraction by gel electrophoresis Tris-borate-EDTA buffer (TBE) Trisaminomethane + Boric Acid+ EDTA + Distilled Water + HCl 8-8.3 Gel electrophoresis
In Biological System Criteria of Good Biological Buffer A) Solubility More water soluble B) Permeability Freely permeable to cell membranes C) Ionic strength & Inertness Should not hinder enzyme activity D) UV absorption Light absorption should be within 230 nm Should not interfere with the spectrophotometric studies in biological research.
Image source: onlinebiologynotes.com
Phosphate buffer Image source: Chemistry@Elmhurst
Protein Buffer Haemoglobin Buffer Image source: Biology Discussion
Amino Acid Buffer Image source: BiologyDiscussion
Plasma Protein Buffer • All proteins with positively charged & negatively charged groups can act as buffer. • Proteins having histidine residues are adept in buffering. • Albumin is the predominant plasma protein functioning as buffer. • Albumin consists of 610 amino acids. Amino acids in Albumin Acidic amino acid Basic amino acid Neutral amino acid Aspartic acid Histidine, lysine, arginine Phenylalanine, valine, threonine, leucine
Carbonic acid-Bicarbonate buffer
Acid-Base Balance Disorders
ACIDOSIS Image source: www.bioinfo.org
Diabetic Ketoacidosis
ALKALOSIS Image source: www.bioinfo.org
SUMMARY • Acid-base balance is necessary to be maintained for the functioning of all biological activities. • Various types of buffers work in a coordinated manner in the living body. • In plants bicarbonate and phosphate buffers are found in the chloroplast, protoplasm, and vacuoles. • Drastic deviation from normal pH of body leads to chronic situations resulting death.
REFERENCES • Kosikowsky, F. V., & Dahlberg, A. C. (1949). Application of a Sodium Carbonate- Bicarbonate Buffer in the Phosphatase Test for Cheese1. Journal of Dairy Science, 32(9), 760-763. • Lebovitz, H. E. (1995). Diabetic ketoacidosis. The Lancet, 345(8952), 767-772. • Nelson, D. L., Lehninger, A. L., & Cox, M. M. (2008). Lehninger principles of biochemistry. Macmillan.
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