The document discusses pH meters, which are electronic instruments used to measure the pH (acidity or alkalinity) of liquids. A pH meter consists of a glass electrode and reference electrode connected to an electronic meter. It measures the voltage difference between the electrodes, which corresponds to hydrogen ion concentration and thus pH. The document covers pH meter components, calibration using buffer solutions, factors affecting measurements, applications including quality control of Ayurvedic formulations, and limitations. pH meters provide accurate pH readings and are useful for standardization in pharmaceutical and other industries.

1. Presented by – Dr. Ajith kumar
Final year PG scholar
Dept. Of Rasashastra & Bhaishajya Kalpana
KLE Shri B.M.Kankanavadi Ayurveda Mahavidyalaya,Belagavi
INSTRUMENTAL SEMINAR
PH METER

2. CONTENTS
• Introduction
• Objectives
• pH
• History
• Types
• Parts of pH Meter
• pH measurement
• Basic principles
• Depending factors
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3. CONTENTS
• Standard operating procedure
• Precaution
• Utility
• Examples
• Limitations
• Article
• Conclusion
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4. INTRODUCTION
• A pH meter is an electronic instrument used for measuring pH (acidity or
alkalinity) of a liquid.
• A typical pH meter consists of special measuring probes ( a glass electrode and a
reference electrode) connected to an electronic meter that measures and displays
the pH reading.
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5. OBJECTIVES
• To understand how to evaluate the pH of different substances.
• To find out the utility of pH meter and importance of pH in Ayurveda.
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6. pH
• pH is a unit of measure which describes the degree of acidity or alkalinity(basic)
of a solution.
• It is measured on scale of 0 to 14.
• The formal definition of pH is the negative logarithm of hydrogen ion avtivity.
pH = -log[H+]
• The addition of acid to water which increases the concentration of Hydrogen ions
and reduces the concentration of hydroxyl ions.
• The addition of base to water would increase the concentration of hydroxyl ions
and decrease the concentration of hydrogen ions.
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7. pH
• Acidic solutions have a lower pH(inversely proportional ), while basic solutions
have a higher pH(directly proportional).
• At room temperature (25°C or 77°F), pure water is neither acidic nor basic and has
a pH of 7.
• pH is an important quantity that reflects the chemical conditions of a solution.
• The pH can control the availability of nutrients, biological functions, microbial
activity, and the behavior of chemicals.
• It is a physical parameter used in qualitative as well as quantitative assessment of
formulations.
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8. pH
• pH is measured by 3 methods.
1.Litmus paper – to find out the nature of sample (acid/base)
2.pH indicating paper – gives range of pH
3.pH meter – gives accurate value
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9. HISTORY
• The first commercial pH meter was built around 1936 by Radiometer
in Denmark and by Arnold Orville Beckman in the United States.
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10. pH meter
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11. SIMPLE pH METER
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12. pH meter
• A pH meter is an electronic device used for measuring the pH of a liquid, though
special probes are sometimes used to measure the pH of semi-solid substances.
• A typical pH meter consists of a special probe (a glass electrode) connected to an
electronic meter that measures and displays the pH reading
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13. TYPES
TYPES
MANUAL pH
METER
DIGITAL pH
METER
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14. PARTS OF pH METER
Three parts:
• A pH measuring electrode
• A reference electrode
• High input meter.
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15. pH measurement
• A pH measurement system consists of 3 parts
• The pH measuring electrode is a hydrogen ion sensitive glass bulb.
• The reference electrode output does not vary with the activity of the hydrogen ion.
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16. ELECTRODE
• Electrodes are rod-like structures usually made of glass,
with a bulb containing the sensor at the bottom.
• The glass electrode for measuring the pH has a glass bulb
specifically designed to be selective to hydrogen-ion
concentration.
• On immersion in the solution to be tested, hydrogen ions in
the test solution exchange for other positively charged ions
on the glass bulb, creating an electrochemical potential
across the bulb.
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17. ELECTRODE
• The electronic amplifier detects the difference in electrical potential between the
two electrodes generated in the measurement and converts the potential difference
to pH units.
• The magnitude of the electrochemical potential across the glass bulb is linearly
related to the pH according to the nernst equation.
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18. NERNST EQUATION
• Nernst Equation is an equation that represents relationship between the
concentrations of an ion under non-standard and equilibrium conditions.
• Its one of the most important equations in chemical engineering to balance a
chemical gradient that exists for the ion in question.
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19. REFERENCE ELECTRODE
• The reference electrode is insensitive to the pH of the solution,
being composed of a metallic conductor, which connects to the
display.
• This conductor is immersed in an electrolyte solution, typically
potassium chloride, which comes into contact with the test
solution through a porous ceramic membrane.
• The display consists of a voltmeter, which displays voltage in
units of pH.
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20. BASIC PRINCIPLE
• On immersion of the glass electrode and the reference electrode in
the test solution an electrical circuit is completed In
which there is a potential difference will be created and detected by
the voltmeter.
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21. BASIC PRINCIPLE
 The circuit can be thought of as going from the conductive element of the
reference electrode surrounding potassium-chloride solution, through the
ceramic membrane test solution,
The hydrogen-ion-selective glass of the glass electrode solution inside
the glass electrode silver of the glass electrode, and finally the
voltmeter of the display device.
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22. DEPENDING FACTORS
• Temperature Compensation
Temperature compensation is contained within the instrument, because pH
electrodes and measurements are temperature sensitive. The temperature
compensation may be either manual or automatic.
• Buffer Solutions
Buffers are solutions that have constant pH values and the ability to resist changes
in that pH level. They are used to calibrate the pH measurement system (electrode
and meter).
• Buffer capsule : each capsule dissolve in 100ml distilled water and gives buffer
solution
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24. SOP
MATERIALS AND EQUIPMENTS :
• pH meter
• General laboratory glassware
• pH 4 buffer, pH 7 buffer
PROCEDURE
• Switch on the button wait for approximately 2 mints
• Remove the stored water from the beaker, wipe the electrode with the blotting
paper and dry it.
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25. Contd….
• Measure the pH 4 by taking the buffer solution which is pink in color.
• Adjust the meter to read 4 with the calibrated 1.knob on left.
• Remove the buffer and wipe the electrode with blotting paper.
• Measure the pH of 10 buffer which is blue in colour.
• Adjust the meter to read 10 with the calibrated 2 knob on right side
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26. Contd…
• Remove pH 10 buffer and wipe the electrode with blotting paper.
• Measure the pH of 4 again pH should read 4, if not readjust calibrated
1 knob.
• Return to pH 10 buffer, pH should read10. If not readjust calibrated 2
knob.
• Then take fresh sample and take 3 readings.
• Average to be calculated.
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27. PRECAUTIONS
• A pH electrode is fragile and one should not be tempted to use it as a stirring glass
rod when adjusting pH and should not touch the beaker when placing the
electrode.
• A pH meter needs to be calibrated daily with the help of standard buffer solutions.
• pH readings are temperature-sensitive due to changes of glass electrode resistance.
A 10-fold increase in resistance results for every 30°C rise in temperature.
• Avoid temperature fluctuations and never keep the pH meter exposed to direct
sunlight.
• The glass electrode should not be left out of the storage solution for prolonged
intervals as the glass membrane gets dehydrated resulting in slower response and
can eventually lead to complete response failure.
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28. Contd….
• The electrode should not be immersed in dehydrating solutions such as sulphuric
acid and ethanol.
• Glass is rapidly attacked by hydrofluoric acid so never keep the electrode in HF
solution as it can lead to irreparable damage of the electrode.
• Avoid vibrations and shock.
• Handle carefully during inter-or intra laboratory transport to prevent breakage.
• After every soaking the electrode should be rinsed with distilled water. Droplets
adhering to electrode should be gently dried with tissue paper and not rubbed or
wiped.
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29. UTILITY
• Healthcare and clinical applications such as blood chemistry -For the diagnosis of
various disorders in human body
• Manufacturing Pharmaceuticals - Jam and jelly Manufacturing
• Soil measurements in agriculture
• Brewing of wine or beer
• Printing
• Environmental remediation
• Water quality for municipal water supplies, swimming pools
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30. IN AYURVEDA
• To evaluate the pH of different formulations such as Kashaya,
arishta, asava, kshara, vati etc.
• For the standardization of the formulations.
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31. EXAMPLES
 FROM API
 ARISHTAAND ASAVAS
1. Abhayarishta : 3.6 - 4.2
2. Amrutharishta : 3.4 - 4.4
3. Kumaryasava : 3.5 - 4.2
4. Punarnavasava : 3.5 - 4.5
5. Dasamoolarishta : 3.6 - 3.7
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32.  AVALEHA (5% aqueous solution)
1.Dasamoola haritaki : 3.96 – 4.08
2.Madhusnuhi rasayana : 4.02 – 4.17
 CHURNA (10% aqueous solution)
1.Avipattikara churna : 4.0 – 6.0
2.Bhaskaralavana churna : 4.0 – 4.17
3.Amalakyadi churna : 3.0 – 4.0
API
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33. API
 GUGGULU PREPARATIONS (1% aqueous solution)
1.Gokshuradi guggulu : 4.42 – 4.9
2.Laksha guggulu : 4.17 – 5.19
3.Yogaraja guggulu : 4.7 – 5.0
 KSHARA LAVANA (10% aqueous solution)
1.Apamarga kshara : 10.0 – 11.0
2.Kalyanaka kshara : 10.0 – 11.0
3.Arka lavana : 9.0 – 10.0
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34. API
 VATI (10% aqueous solution )
1.Sanjivani vati : 4.0 – 5.5
2.Rajapravartini vati : 6.5 – 7.5
 LEPA ( 5% aqueous solutions )
1.darvi malahara (gel) : 3.7 – 4.2
• For ghritha and thaila – no pH value available in API.
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35. OTHER SAMPLES
• For lotion and ointment -
 use pH paper
 prepare 10% solution with homogenizer/magnetic stirrer
 mix with hexane and make 10% solution (remove fat content)
• If the sample is more soluble makes 5% aqueous solution
• If it less soluble makes it as 10% aqueous solution
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36. LIMITATIONS
• The glass electrode can be damaged by strong alkaline solution, HF,
contamination, scratches and high temperatures leads to error in
values.
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37. ARTICLE
• Preparation and evaluation of fermented ayurvedic formulation : arjunarista
by, S. F.SAYYAD, D. S. RANDIVE, S.M. JAGTAB, S.R. CHAUDHARI AND
B.P. PANDA
= Alcohol percentage, pH, acid value, solid content, viscosity, refractive index and
specific gravity can be considered as the basic tools for the quality control measures
of arishtas.
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38. pH METER
• In market we get different types of pH meter
• Price starts from 300-400 rs.
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39. DIGITAL pH METER
PORTABLE pH METER
DIGITAL LCD POKET PEN
SOIL TESTER
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40. CONCLUSION
• A pH meter is an electronic instrument used for measuring the pH of a
liquid/semi-solid substances.
• We exploited the properties of this indicator to determine with precision the
acidity or alkalinity of various substances.
• pH meter is more useful than the other pH indicators because it gives accurate
reading and can measure the pH of a liquid as well as a semi-solid substance.
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