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About pH and Buffer .pdf

This document summarizes information about pH and buffers. It defines pH as the negative log of the hydrogen ion concentration, and describes Sorensen's pH scale which ranges from 0-14. Common methods for measuring pH are discussed, including pH strips, indicators, meters, and calorimetric/electrometric methods. The key components and functions of buffers are outlined, including the buffer equation, buffer capacity, and examples of acidic and basic buffers. The roles of important biological buffers and uses of buffers in pharmaceutical systems and applications are highlighted in less than 3 sentences.

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By – Priya Awasthi B PHARMA PH AND BUFFER
CONTENT :- ▪︎ pH - Introduction - pH value - Sorenson’s pH scale - Measurement of pH - Applications of pH ▪︎ Buffer - Introduction - Types of buffers - Buffer equation - Buffer capacity - Buffer in biological and pharmaceutical systems - Application of buffers
PH VALUE Introduction-: ▪︎ It is the negative log of the hydrogen ion concentration. pH = -log[H+] • pH has a unit of measure which describes the degree of acidity or alkalinity (basic) of a solution. • It is measured on a scale of 0 – 14 . • Low pH values correlate with high concentration of H+ and high pH value correlate with low concentration of H+.
• When weak acids or weak bases are dissolved in water, they can contribute H+ by ionizing or consume H+ by being protonated. These processes are also governed by equilibrium constant thetotal hydrogen ion concentration from all sources, which is experimentally measurable , is expressed as the pH of the solution. • pH is the measure of how acidic / basic solution is. The range goes from 0 to 14 , with 7 being neutral. pH of less than 7 indicates acidity, whereas a pH of greater than 7 indicates a base .
PH VALUE • The pH value of a substanceis directly related to the ratio of the hydrogen ion and hydroxyl ion concentration. • If the H+ concentration is higher than OH- the material is acidic . • If the OH- concentration is higher than H+ the material is basic. • < is acidic , 7 is neutral , > is basic.
SORENSEN’S PH SCALE • Danish biochemist Soren Sorenson in 1909 developed the pH scale and introduced pH definition as minus (-) logarithm of [H+] to the base 10. • A pH of 7 considered as “neutral’’, because the concentration of hydrogen of hydrogen ions is exactly equal to the concentration of hydroxide (OH-) ions produced by dissociation of the water. • The hydrogen ion concentration in pure water at room temperature is about 1×10-⁷ M .
MEASUREMENT OF PH ph value can be measured by using following methods :- • ph stripes • ph indicators • ph meter • Electrometric and calorimetric
□ pH stripes – A pH test strip is a strip of litmus paper with which you can measure the pH value of a liquid. The substance in the paper causes the paper to show a different colour at different acidities. The official pH scale is from 0 to 6 , where 0 is very acidic and 6 very alkaline. Example - Litmus Paper. □ pH indicators – Indicators are the organic compounds of natural or synthetic origin whose color is dependent on pH. The pH Indicators are either weak acids or weak bases having different colours in undissocisted dissociated forms : HIn <--> H± + In – (colour – A) (colour - B)
□ pH meter - The pH meter is a laboratory equipment which used to measure acidity or alkalinity of a solution. The pH meter measures the concentrationof hydrogen ions [H+] using an ion sensitive electrode. It is the most reliable and convenient method for measuring pH . □ Electometric – The basic principle of the electrometric pH measurement is determination of the activity of the hydrogen ion by potentiometric measurement using a standard hydrogen electrode and a reference electrode. The measuring device is calibrated using a series of standard solutions of known pH.
Calorimetric- Calorimetric method is based on the property of acid – base indicator dyes ,which produces colour depending on pH of the sample. The color change can be measured as an absorbance change spectrophotometrically . APPLICATIONOF pH *Uses in industries • Wastewatertreatment. • Aquaculture. • Food and beverages. • Pool and spa water. • Aquarium and fish tanks . • Research . • Hydroponics.
* Uses in daily life • Existence of living beings. • Digestion of food. • Importance in soil. • Stopping tooth decay. • Remedy for acidic effect of honeybee bite. • Enhancing solubility. • Increasing stability. • Improving purity and comforting the body. • Storage of products.
BUFFER Introduction - A buffer solution is a solution that only changes slightly when an acid or a base is added to it. For an acid- buffer solution, it consists of a weak acid and its conjugate base. For a basic- buffer solution, it consistsof a weak base and its conjugate acid. Typically a mixture of a weak acid and a salt of its conjugate base or weak base and a salt of its conjugate acid.
TYPES OF BUFFER Generally buffers are of two types :- 1. Acidic buffers 2 . Basic buffers
ACIDIC BUFFERS An acidic buffer is a combination of weak acid and its salt with a strong base. i.e. Weak acid and salt with strong base (conjugate base). □ Example- • CH3COOH / CH3COONa • H2CO3 / NaHCO3 • H2PO4 / NaHPO4 • HCOOH / HCOONa
BASIC BUFFERS A basic buffer is a combination of weak base and its salt with a strong acid. i.e. Weak base and salt with strong acid (conjugate acid). □ Example: • NH4OH / NH4Cl • NH3 / NH4Cl • NH3 / (NH4)2CO3
BUFFER EQUATION The strength of a weak acid (buffer) is usually represented as an equilibrium constant. The acid – dissociated equilibrium constant , which measures the propensity of an acid to dissociate , is described using the equation. It is also known as “HENDERSON HASSELBALCH EQUATION ’’ . Lawrence Joseph HENDERSON wrote an equation , in 1908 , describing the use of carbonic acid as an buffer solution. Karl Albert HASSELBALCH later re-expressed that formula in logarithm terms , resulting in the HENDERSON – HASSELBALCH equation.
BUFFER CAPACITY Buffer capacity is defined as the number of moles of an acid or a base required to be added to one litre of the Buffer solution so as to change its pH by one. The greater the buffer capacity the less the pH changes upon addition of H+ or OH - . Choose a buffer whose pKà is closest to the desired pH.
BUFFER IN BIOLOGICAL AND PHARMACEUTICAL SYSTEMS Biological Buffer Systems:- □ Phosphate Buffer Systems : • It is mainly intracellular buffers . It’s concentration in plasma is very low . • The Phosphate buffer system is found to be effective at a wide pH range , because it has more than one ionizable group. • In the body , Na2HPO4 / NaH2PO4 is an effective Buffer system.
□ Protein Buffer System :- • The protein buffers are very important in the plasma and the intracellular fluids but their concentration is very low in cerebrospinal fluid , lymph and interstitial fluids. • The proteins exists as anions serving as conjugate bases (Pr) at the blood pH is 7.4 and from conjugate acids (HPr) accepting H+ . • They have the capacity to buffer some H2CO3 in the blood.
□ Hemoglobin buffer :- • Predominant non carbonic buffer in ECF .pKa- 6.8 . • Buffers both resp and metabolic acids. • Buffers CO2 by two methods - 1. Allow CO2 to combine directly with amino acids to form carbamino compound. Accountsfor 15 – 25 % of total CO2 transport. 2. CO2 is catalyzed in RBCs to H+ and HCO3 – by carbonic anhydrase enzyme. H+ buffered by Hb to HHb . The free HCO3 diffuses into plasma in exchange to Cl- , known as Chloride Shift .
□ Buffer in Pharmaceutical Systems :- • Buffers are used to prepare standard solutions of definite pH value which are insensitive towards the addition of small amounts of acids or bases. • Penicillin preparations are stabilized by the addition of Na-citrate or aluminum hydroxide. • Sulfamide preparation usually contains bicarbonate sodium acetate or sodium citrate when acts as a buffer. • Buffer solution are employed in the formation of ophthalmic preparation. • A combination of KH2PO4 and K2HPO4 is widely used in bacteriologica culture media for the cultivation of bacteria. • It is used to control the pH of a chemical reaction catalyzed by enzymes.
• Standard buffer solutions are used with indicator for the determination of pH. • It is also used to check the performance of electrodes used in pH determination.
APPLICATION OF BUFFERS • To improve purity. • To increase stability. • To enhances solubility. • To optimize biological activity. • To maintain constant pH.
THE END !!! THANK YOU !!!