About pH and Buffer .pdf

It is an informative article about the pH and buffer system which is related to technology and science. It consist information about the pH and buffer solution which is widely used in the fields of pharmaceuticals as well as science and technology .

1. By –Priya Awasthi
B PHARMA
PH AND BUFFER

2. 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

3. 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+.

4. •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 the total 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 .

5. PH VALUE
•The pH value of a substance is 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.

6. 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 .

8. MEASUREMENT OF PH
ph value can be measured by using following methods :-
•ph stripes
•ph indicators
•ph meter
•Electrometric and calorimetric

9. □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)

10. □pH meter -
The pH meter is a laboratory equipment which used to measure
acidity or alkalinity of a solution. The pH meter measures the concentration of
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.

11. 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 .
APPLICATION OF pH
*Uses in industries
•Wastewater treatment.
•Aquaculture.
•Food and beverages.
•Pool and spa water.
•Aquarium and fish tanks .
•Research .
•Hydroponics.

12. * 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.

13. 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 consists of 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.

14. TYPES OF BUFFER
Generally buffers are of two types :-
1.Acidic buffers
2 . Basic buffers

15. 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

16. 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

17. 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.

19. 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.

20. 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.

21. □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.

22. □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. Accounts for 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 .

24. □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.

25. •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.

26. APPLICATION OF BUFFERS
•To improve purity.
•To increase stability.
•To enhances solubility.
•To optimize biological activity.
•To maintain constant pH.

27. THE END !!!
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