PHAN (FINALS): ASH and WATER DETERMINATION

Vegetable or animal drugs

Analysis of Crude Drugs:

- natural substances

Analysis of Crude Drugs

made to establish the purity, or to determine the amount of therapeutically active constituents present for the purpose of standardization

Crude drugs

are derived from any part or parts of plants and may contain one or more active ingredients

Drug evaluation

may be defined as the determination of identity, purity and quality of a drug

Identity

Quality

Purity

Scope of Drug Evaluation (3)

Identity

- identification of biological source

of the drug

Quality

- the quantity of the active

constituents present.

Purity

- the extent of foreign organic

material present in a crude drug.

(1) Organoleptic

(2) Microscopic

(3) Physical

(4) Chemical

(5) Biological

Methods of Drug Evaluation: (5)

Organoleptic

- It includes the visual examination of drug

- Gives the gross, morphological structure of the sample

❖ Plant parts: Barks, Underground

structures, Leaves, Flowers, Fruits,

Seeds

❖ Color, odor, taste, texture, shape or

size

Microscopic or Anatomical

Evaluation

Gives a more detailed examination of a drug, even histological stuctures (cells and tissues) useful for plants DNA barcoding

Physical Evaluation

- Physical contents or physical properties innate or characteristic of specific compound in the sample or the sample as a whole

Moisture Content - Optical Rotation

Viscosity - Refractive Index

Melting point

Ash Content

Extractive values

Volatile oil Content

Chemical Evaluation

- Chemical constants or analytical constants, determination of chemical constituents - ash, moisture, crude fiber, and extractive obtained with different solvents,

- Tests to determine different and specific chemical constituents - estimation of alkaloidal content, acid value, ester value or phytoconstituents

Phytochemical Screening

Testing or evaluating chemical composition of plant sample

JUST READ Phytochemical Screening

Extraction and Qualitative Phytochemical Screening of Medicinal Plants: A Brief Summary

❖ Article in International Journal of Pharmacy · January 2018, By Teresa May B. Bandiola Phytochemical Screening and extraction: A Review

❖ Article in Internationale Pharmaceutical Scientia March 2011, By Preshant Tiwari

❖ Tabulate the following:

1. Phytochemical screening

2. Methods of Extraction

3. Commonly used solvents for extraction

Physicochemical and Instrumental

They make use of various instruments for evaluation like spectrophotometry, chromatography, etc.

Spectrophotometry

Used to identify what are the different functional group present in the constituent

fingerprint region

Peaks correspond to compound as a whole

Useful if you have reference standard

Biological Evaluation

- Determination of the effects of drugs upon microbes, animals, as animal tissues

- This method requires special apparatus for their performance and a technique that is not chemical in nature

International Standard preparation

Biological evaluation uses _____ to compare the biological effects of the test substance

Quantal

"all or none response" or "endpoint method"

Graded

"response is proportional to dose, it may be between no response to maximum response"

Tubocurarine Head Drop Test

Examples of Biological Assay:

• "All or none response"

• Flaccid paralysis of muscles (fine movements)

Tubocuranhe relaxes the rabbits's neck muscle producing the ENDPOINT head crop effect

Digitalis Pigeon Emesis Test

Examples of Biological Assay:

• "All or none response"

• ENDPOINT Stoppage of heart characterized by emesis

Digitalis is a positive inotropic agent which causes an increase cardiac muscle contractien

Oxytocin Chicken thigh Arterial Pressure

Examples of Biological Assay:

• Graded response

• Decrease in arterial Blood Pressure

Oxyiocin has a vasodilation effect leading to decrease in BP

Ash Content

_____ of a crude drug is the residue left after incineration.

Ash Content

usually represents the inorganic salts

naturally occurring in the drug adhering to it.

adulteration

Ash content may also include inorganic matter added for the

purpose of _____

adulteration,

substitution,

contamination or

carelessness in handling

High ash content indicates (4) =

Determination of Ash

serve as basis for judging the identity

and cleanliness of a drug

Total ash, acid-insoluble ash and water-soluble ash

Ash standards

set a maximum limit on total ash or acid insoluble ash

Total ash

usually contains carbonates, phosphates, sulfates, chlorides, oxides, etc. of calcium, magnesium, potassium, sodium, aluminum, iron and other metallic elements.

Acid insoluble ash

is the residue after incineration using the residue after acid treatment and it represents silica

silica

Acid insoluble ash

= represents

Treat w/ diluted HCl and filter using ASHLESS filter paper (less than 0.007%)

soluble chlorides,

alkali and

ammonium salts

Water soluble ash

= represents

Ash>boiled w/ distilled water>filter>ignite residue on filter paper>weigh

Muffle Furnace

Used to convert sample into ash

Very Dull Red Heat 500C-550C

Dull Red Heat 550C-700C (most use)

Bright Red Heat 800C- 1000C

Yellow Red Heat 1000C-1200C

White Heat 1200C- 1600C

Approximate Temperature

Equivalents muffle furnace

Just read or memorize

❖ 825 °C - Ca carbonates oxides

❖ 1550 °C - Ca phosphates pyrophosphates

❖ 600°C - Li carbonates oxides

❖ 1500°C - KCl sublimes

Such temperatures can be obtained using the Bunsen burner (in blue flame)

Constant Weight

When 2 consecutive weighings do not differ by more than 0,5 mg

Residue on Ignition

For determining ash content of expensive chemicals (organic substances) using temperature of 600 +/- 50 degrees.

Igniting the sample to dull redness and residue should not exceed 500micrograms

Loss on Ignition

For determining organic matter volatilized and driven off under the temperature range of 800 +/- 25 degrees Celsius

Loss on Drying

For determining volatile matter of any kind that is driven off at 110-120

degrees Celsius

Moisture content

Official drugs vary in their water content

* Determination of this constant is necessary to specify certain water content limits in the drug monographs.

* In order to ensure uniformity in the official drugs

Hydrates

Water of crystallization

Ex. CuSO4.5H2O- copper sulfate pentahydrated

Na2B4O5(OH)4.8H2O- borax

Sodium borate octahydrated

Hydroscopic Compounds

Water in adsorbed form example

❖ percent of active constituent must be calculated on the basis of the moisture-free drug.

❖ Variable quantities of moisture would adversely affect the calculated results.

❖ Control of the amount of water contained in chemicals is important in making solution of definite concentration and in the determination of the dosage substances used as medicaments

Water content is determined for the following reasons: just read

1. GRAVIMETRIC METHOD

2. GRAVIMETRIC METHOD

3. AZEOTROPIC/ TOLUENE

DISTILLATION

4. TITRIMETIC

5. DEW POINT METHOD

6. ELECTROLYTIC METHOD

6 METHODS OF WATER CONTENT

DETERMINATION

Gravimetric Method

-for drugs containing no constituents other than water, volatile at 105°C.

- for drugs containing ether-soluble constituents, volatile at 105°C.

Azeotropic Method or toluene distillation

- for the determination of moisture content of many vegetable drugs containing 2% or more of moisture

Titrimetric Method or Karl Fischer Method

- for crystalline compounds that contain water of hydration or absorbed water

Dew Point Method

- for determining Water at Very Low

Concentration

Electrolytic Hygrometric

- for determining Extremely Low Concentration of Water

METHOD I TITRIMETRIC METHOD/ KARL FISCHER METHOD

Method II - Azeotropic Method

METHOD III: Gravimetric Method

USP 3 methods for Water Content Determination Official Methods

Method I Titrimetric method/ Karl Fischer method

This method is the most rapid,

requires only a small sample and

is specific for water.

Direct titration

Method 1

Ia

Residual Titration

Method 1

Ib - use standard water soln and karl fischer reagent

coulometric titration

Method 1

Ic - applying current geberated by water content of sample

1ml

5 mg

Titrimetric method/ karl-fischer method

____ of reagent is equivalent to approximately ___ of water

methanol

Karl Fischer reagent

iodine,

sulfur

dioxide,

pyridine,

and methanol.

Karl fisher method involves titration of the sample in reagent ____ with ___, which consists of ____,____,___,___, and ____

Anhydrous methanol

prevents pyridine-sulfur complex

Iodine sulfur dioxide

Reacts with water

Pyridine

prevents reversal of reaction

Sodium Tartrate (Na2C4H4O6)

karl Fischer is standardized by ___ as primary standard

Standardization of KFR: just read

Place 36 mL of methanol in the titration vessel.

➕ Add Karl Fischer reagent until the canary yellow endpoint appears.

⚖️ Quickly add 150-350 mg of accurately weighed sodium tartrate.

🔁 Titrate again with Karl Fischer reagent until the same yellow endpoint is reached.

Method II - Azeotropic Method

is specified for the determination of moisture content of many vegetable drugs containing 2% or more of moisture.

disadvantage- the need for large amount of drug, from fifty (50) to one hundred (100) grams must be used in order to secure a volume of water that can be measured conveniently without considerable error

Toluene distillation

AZEOTROPE

- mixture of liquids with constant boiling point

METHOD III: Gravimetric Method

When the drug contains matter other than water which is volatile at 105°C, the volatile ether soluble extractive must be determined and the weight of this extractive is subtracted from the weight less by the drug upon drying, the difference is the moisture content of the drug.

Dew Point Method

Water at Very Low

Concentration: used what method

Water at Very Low Concentration

Measures water vapor by noting the temperature where dew/mist forms.

Happens after adiabatic expansion (cooling after pressure release).

Water content is read using calibrated charts

Electrolytic Hygrometric Method

Water at Extremely Low Concentration

Used what Method

Water at Extremely Low Concentration

The principle of selective electrolysis of water may be employed and the amount of electric current is a measure of the water content

Sodium Tartrate

What is the primary standard used in Karl Fischer Reagent?

Acid insoluble ash

This is defined as the ash insoluble in

HCl

Toluene distillation Method

Other name of azeotropic method

Crude Fiber

It consists mainly of cellulose

Gravimetric / Drying / Thermal

Method

This method of water content

determination is used in biologicals.

total ash - residue after treatment with water

Water soluble ash that represents the chlorides and alkali salts may be determined as:

110- 120 C

Temperature used when procedure is loss on drying