Friday, April 23, 2021

Difference between colloid and emulsion

The major difference between colloids and emulsion is that the colloid is a heterogeneous mixture that can form when any state of matter such as solid, liquid, or gas combines with a liquid, while the emulsion is also a heterogeneous mixture of two immiscible liquids in which the dispersed particles do not settle on standing.  

What is colloid and emulsion?

Colloid and emulsion both are often used synonymously, emulsions are formed when two immiscible liquids combine, while a colloid solution can be a liquid or solid dispersion in another liquid. In other words, an emulsion can be called a colloid however not all colloids are emulsions.

Colloids:

A colloid is a heterogeneous mixture in which a dispersed particle is intermediate in size between a solution and a suspension. The particles are uniformly distributed through the dispersion medium, which may be a solid, liquid, or gas. A colloid result when particle’s diameter is ranging in 1 to 1000 nanometer and are dispersed in a liquid solvent.
Colloids differ from solutions in that their dispersed particles are much larger than those of a solution. The dispersed particles of a colloid are not as large as those in a suspension, so the solute does not settle out on standing. The colloids can be separated from the solution because they exhibit light scattering.
Example of a colloid: “Milk” is a colloid solution in which fat particles are uniformly distributed in the water.  

Emulsion:

An emulsion is a type of colloid that refers to microscopic liquid particles dispersed in another liquid. An emulsion is a mixture of oil and water and can only be made by mixing with immiscible liquids and it can be stabilized by adding surfactant or emulsifier.
The emulsion consists of two categories, oil-in-water (O/W) or water-in-oil (W/O) emulsion, depending on the continuous phase. In oil in the water is in large quantity hence it continues phase, and in Water in oil the oil large quantity hence it continues phase and water is in small quantity hence it is discontinues phase.
Example of an emulsion: “milk” is one example of an emulsion of fat and water. Oil and water mixtures are emulsions when shaken together.

Difference between colloid and emulsion:

  • A colloid is a stable system of two phases, one of which is dispersed in the other in the form of very small particles or droplets, whereas emulsion is a stable suspension of small droplets of one liquid in another with which it is immiscible.
  • The colloid shows scatter light (Tyndall effect) while the emulsion can also show the Tyndall effect.
  • A colloid can form when any state of the substance combines with a liquid, while the emulsion consists of two liquid components that immiscible with each other.
  • A colloid is a homogeneous non-crystalline substance consisting of large, whereas an emulsion is a fine dispersion of minute droplets.
  • Colloids do not separate on standing while the emulsion does not settle on standing.
  • The particle size of colloids 1-1000 nm, while the particle size in the emulsion usually ranges from approximately 10 nm to 100 μm.
  • Colloids cannot be separated by filtration, while emulsion also cannot be filtered out.
  • Emulsion dosage forms are opaque in appearance, whereas colloids are translucent because of the Tyndall effect.
Commonly asked questions on colloid and emulsion are as follows.

What is the difference between a colloidal solution and an emulsion? Give one example of each.
The dispersed phase in a colloidal solution is solid, and the dispersion medium is liquid, while in an emulsion, both the dispersed phase and the dispersion medium are liquids.
Example of Colloidal solution- muddy water, cell fluids, etc.
Example of Emulsion- cold cream, milk.etc.

What is the difference between a colloidal solution, gel, and emulsion?
The basic difference between a colloidal solution, gel, and the emulsion is their dispersed phase and dispersed medium. The dispersed phase in the colloidal solution is solid, in the gel is liquid, and in the emulsion is liquid, whereas the dispersed medium in the colloidal solution is liquid, in the gel is solid, and in the emulsion is liquid.


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Thursday, April 22, 2021

Difference between solute and solvent

The basic difference between a solute and a solvent is that a solute is a substance that is added to a solvent to form a solution, while a solvent is a substance that dissolves the solute particles during the formation of the solution.

Solute and solvent both are substances used in chemical laboratories, pharmaceuticals, chromatography, other than they are also part of day-to-day life. A solution has two components namely solute and solvent. The solvent can dissolve the solute in a homogeneous solution.
The solute in a heterogeneous mixture is not evenly distributed, and its concentration different in various parts of the solution. The solute completely dissolves in another substance in a homogeneous mixture, and the solute is evenly dispersed in the solution.

Solute:

A solute is a substance that can be dissolved into a solution by a solvent. It can come in several forms, such as solid, liquid, and gas. The substance, or solvent that dissolves the solute molecule, separates the molecules of the solute and distributes them evenly which creates a homogeneous mixture.
The solute amount in a solution is determined in terms of its concentration. The solute concentration in a solution is measured by the ratio of the volume of the solute to the total volume of the solution.
Examples of solute consist of sugar in tea, salt in seawater, protons in the cytosol, etc. 

Solvent:

A solvent is a substance that allows solutes to dissolve and form a solution. We always believe a solvent to be a liquid however it can also be a solid, a gas, or a supercritical liquid. A solvent can be further classified into two types, which are polar solvents and non-polar solvents.
Examples of the solvent consist of water, alcohols, methanol, acetonitrile, hydrocarbons, and esters, etc.
Solute VS Solvent
  • The major difference between solute and solvent is that a solute is a substance that gets dissolved whereas a solvent is a dissolving medium.
  • The boiling point of solute is higher than solvent, while the boiling point of solvent is lower than solute.
  • Solutes may exist in solid, liquid, or gaseous states, while solvents are often liquid.
  • Solubility of solute depends on the properties of the solute such as surface area and size of molecules, and the properties of both the solvent and the solute are interdependent of each other.
  • The amount of solute in a solution is less than the amount of solvent in a solution, while the amount of solvent in a solution is greater than the amount of solute in a solution.
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Wednesday, April 21, 2021

Difference between syrup and solution

The major difference between solution and syrup is that a solution is a homogeneous mixture formed by dissolving one or more active ingredients, whereas syrup is a viscous oral liquid consisting primarily of sugar or any other sweetening agent.
Dosage forms are intended to deliver the active pharmaceutical ingredient (API) at the site of action within the body. They come in many types depending on the mode/route of administration. Based on the physical form they are liquid, solid, semisolid, and gaseous dosage forms, and based on route they are oral, topical, inhalation, and parenteral route of drug administration. The most commonly used dosage forms include tablets, capsules, granules, syrup, suspensions, elixir, creams, ointments, and injections, etc.

Liquid dosage forms provide rapid and high absorption of soluble drug products hence are one of the oldest dosage forms used to treat various diseases. It can be administered orally, parenterally, or topically. It is especially used for patients who have difficulty swallowing, such as children and elders.
E.g. Syrups, solutions, ear drops, ear drops, lotion, elixirs, and parenteral preparations, etc.

What is syrup in pharmacy?

Liquid syrups are one of the dosage forms that contain a concentrated solution of sugar mixed in water or other aqueous liquid. The syrup is a saturated solution in which drugs dissolve. Some syrup is less viscous, while some are more viscous which is dependent upon the concentration of sweeteners used in the formulation.
It is an oral suspension in liquid form that is used as a vehicle for the drug. Simple syrup, medicated syrup, and flavored syrup are the three types of syrups preferably suitable for pediatric use. The syrup should be stored in a tightly-closed container and in a cool, dry place after use to preserve them.

What is a solution in pharmacy?

Pharmaceutical solutions are liquid formulations in which one or more solutes with excipients have been dissolved in a suitable solvent or miscible solvent mixture. Pharmaceutical solutions are homogeneous, and they can be classified as oral, otic, ophthalmic, or topical, as well as injections, which are sterile and pyrogen-free solutions intended for parenteral administration. Vehicle solutions are classified as aqueous solutions and non-aqueous solutions.

Difference between syrup and solution:

  • The pharmaceutical syrup is intended to use for oral administration while solutions are used for many routes of administration, including oral, rectal, otic, parenteral, and ophthalmic.
  • The syrup can be opaque and cloudy in appearance, while the solution can clear in appearance.
  • Because of the high sugar content, the syrup may not be appropriate for diabetic patients, while the solution is suitable for all types of patients.
  • The oral syrup is always sweet while the oral solution is not.
  • The syrup scatters the beam of light, while the solution is transparent does not disperse the ray of light.
  • The syrup may take more time to filter as it is more viscous, whereas the solution can rapidly be filtered through the filter paper.

Commonly asked questions on syrup and suspension are as follows.

Is syrup a suspension or colloid?
The syrup is not a colloid, it is a suspension solution. Since a colloid is an insoluble microscopic particulate suspended in a solvent, the mixture contains both liquid and solid components.

What is the similarity between syrup and solution?
The major similarity between syrup and solution is that pharmaceutical syrups and solutions are the mixtures of solutes in which the drug particles are also completely dissolved in the solvent.

What are the examples of solutions?
In a solution, all the components appear as a single phase. Common examples of solutions are the sugar dissolved in water, salt dissolved in water, juice, soda water, etc.


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Monday, April 19, 2021

Difference between syrup and suspension

The major difference between syrup and suspension is that the syrup is a concentrated mixture of sugar and water whereas suspension is made up of fine particles of an undissolved solid that are dispersed in a liquid medium.  

The dosage forms are the different drug products they are classified according to the route of drug administration and according to the physical form. Medicines and drugs come in different forms they can be solid, semisolid, liquid, and gaseous dosage forms and they can be administered orally, topically, parenterally, inhalation, and instilled in body cavities. Some examples of dosage forms are tablets, capsules, granules, emulsion, syrup, suspension, elixirs, parenteral preparations, lotions, linctuses, eardrops, suppositories, troches, gels, paste, creams, ointments, and mouthwash, etc.


Oral liquids are homogeneous liquid formulations that typically consist of one or more active pharmaceutical ingredients in a suitable solution, emulsion, or suspension. Oral liquid dosage forms are usually classified into two types- monophonic and biphasic. It is more suitable for patients particularly for children and elderly patients who have difficulty swallowing tablets or other solid medication. Liquids are absorbed faster, more palatable than solids, have more flexibility to formulated and it does not have an unpleasant taste and odor these are some of the advantages of liquid dosage forms.

The pharmaceutical suspension and syrup are both liquid oral dosage forms although they have some differences in their nature and properties, let's check them.

What is syrup?

The pharmaceutical syrup is a viscous oral liquid consisting primarily of sugar or any other sweetening agents. It is one of the dosage forms in which drugs with preservatives and excipients are made soluble in the liquid. Some syrup is less viscous, some are more viscous, and their viscosity depends on the sweetness concentration used in the formulation. There are three types of syrups, simple syrup, medicated syrup, and flavored syrup, and these are best suited for pediatric use.

What is suspension?

Pharmaceutical suspension is a semi-solid or biphasic liquid dosage form, in which the internal phase is dispersed uniformly throughout the external phase, resulting in a coarse dispersion. The internal phase ranges from 0.5 to 5 microns in size, whereas the outer phase, which is usually aqueous in some instances, maybe organic or oily liquid for non-oral use. Oral suspensions, parenteral suspensions, ophthalmic suspensions, and suspensions for external use are the four major types of suspensions based on their pharmaceutical use. 

Difference between syrup and suspension:

  • A syrup is a solution that completely dissolves into its solvent, whereas a suspension is a mixture of solutes in which the drug particles do not completely dissolve in the solvent.
  • The syrup may not be suitable for patients with diabetes due to the high amount of sugar, while the suspension may be appropriate because it does not make with sugar.
  • Syrups are dissolved in various solvents such as sugar or alcohol, while suspensions are dissolved in water.
  • The syrups are suitable for children because the sugar in the formulation masks the bitter or unpleasant taste, while the suspension may not be suitable for children due to unpleasant taste.
  • The pharmaceutical syrup is a solution that fully dissolves into its solvent, so it does not need to be shaken, while suspensions need to shake well before administration, as the drug particles settle to the bottom upon long-standing.
  • Pharmaceutical suspension products require labeling such as "shake well before use", while syrup does not require this type of labeling.
Syrup VS Suspension
Difference between syrup and suspension

Commonly asked questions on syrup and suspension are as follows.

What is the similarity between syrup and suspension?
The major similarity between syrup and suspension is that both are drugs and medicines suspended in a type of a dissolvent.

Is syrup a colloid or suspension?
The syrup is a suspension solution, not a colloid.

Is liquid medicine a suspension?
Liquid suspension occurs when a medication is prepared in a liquid form that may be a suspension, syrup, or solution in nature.


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Saturday, April 17, 2021

Difference between suspension and solution

The major difference between suspension and solution is that the suspensions are a heterogeneous mixture, which means that the components do not mix completely and will most likely separate in the near future whereas, the solutions are homogeneous mixture since the components mix well together and remain mixed without separation.     
Suspensions and solutions are both mixtures of various substances that are formed by combining one or more substances with different properties. Suspension, solution, colloids, and other dispersions are parallel however they have characteristics that differentiate each other.

Suspension:

A suspension is a heterogeneous mixture of particles that have a diameter greater than 1000 nm and are visible to the naked eye. It is a heterogeneous mixture consisting of solid particles sufficiently large for sedimentation. All particles are completely mixed in this form of a mixture and can be seen under a microscope but light cannot pass through them.

When insoluble solid particles are dispersed in a liquid medium, they form a suspension. The solute particles are uniformly dispersed in the medium when shaken, but if left undisturbed, the solute particles, which vary in size from 0.5 to 5 μm, settle and can be isolated from the solution by filtration or centrifugation. They are classified according to their dispersion phase that can be solid and their dispersion medium which can be solid, liquid, or gas.

Examples of suspension:

  • Sand in water
  • Milk of magnesia
  • Dusty air
  • Paints in which dyes are suspended in turpentine oil
  • Flour in water
  • Muddy water  

Solution:

A solution is a clear homogeneous mixture and solute particles no longer appear nor do they settle. The particles of solute have dimensions of molecular size and do not disperse the light beam passing through it. The solution has two components, solute, and solvent; a solute is a substance that is to be dissolved, and a solvent is a substance that dissolves the solute through a chemical change.

Since the composition is homogeneous, it is not possible to separate the solute from the solvent by filtering. Distillation is the only alternative, as it extracts the solvent while leaving a solid residue of the solute behind. The true solution, colloidal solution, and suspension are the three types of solutions that are classified based on the nature of particle sizes. These types of solutions show substantial differences in their nature, filterability, appearance, and color.

Examples of solution:

  • Salt solution
  • Alcohol in water
  • Tincture of iodine
  • Sugar solution
  • Soda water  

Difference between suspensions and solutions:

  • Suspension is a heterogeneous mixture whereas the solution is a homogeneous mixture type.
  • In suspension, the solute does not dissolve, it is suspended in the liquid and settled in the medium, while in solution, the solutes and solvents are suitably mixed in the liquid phase.
  • Suspension scatters the beam of light, while the solution does not scatter the beam of light.
  • The particle size of the suspension is more than 100 nm, whereas the particle size of the solution is less than 1 nm.
  • Suspension may or may not exhibit the Tyndall effect which depends on the type of mixture, while the solution does not exhibit the Tyndall effect.
  • The particles of a suspension can be seen by the naked eye whereas the particles of a solution are at the ion or molecular level and cannot be seen with the naked eye.
  • The suspension is unstable, whereas the solution is highly stable.
  • The suspension is cloudy and opaque, whereas the solution is unclouded and clear in appearance.
  • The suspension is settling on standing, while the solution is not settled.
  • There is no diffusion in the suspension, while rapid diffusion occurs in the solution.
  • The suspension particle does not pass through the filter paper, while the solution passes through the filter paper. 
Suspension VS Solution
Difference between suspension and solution

Commonly asked questions are as follows.


What are the different types of the solution?
Solid-solid, solid-liquid, solid-gas, liquid-solid, liquid-liquid, liquid-gas, gas-solid, gas-liquid, and gas-gas are the types of solution.

How is a solution similar to a suspension?
Both solution and suspension are mixtures of two or more components and none of those components are chemically bonded together. The components in both solution and suspension can be isolated based on their physical properties by size, solubility, and density.

What are Colloids?
A colloid is a mixture in which one material is suspended in another by microscopically scattered insoluble particles. Example: milk, butter.

Which dosage form is semi-solid oil in water emulsion?
The cream is semi-solid oil in water emulsion that comes in two types: oil-in-water (O/W) and water-in-oil (W/O).
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Saturday, April 10, 2021

Semi solid dosage form and its classification

Learn about semi-solid dosage forms and their types, packaging, and storage of semi-solid dosage forms, ideal properties of semisolid dosage for, and excipients or additives used in the semi-solid dosage form.

Medication is more effective when it reaches its site of action therefore the different routes and dosage forms are used to treat various diseases. Dosage forms are the way by which active pharmaceutical ingredients (API) are delivered to sites of action within the body to achieve the optimum desired results with the least amount of side effects. It consists of a combination of drugs and excipients, prepared in a specific configuration and apportioned into a specific dose.

Based on the physical state the pharmaceutical dosage forms are classified as solid, semi-solid, liquid dosage forms, and gaseous dosage form and based on route of administration the pharmaceutical dosage forms are classified as oral, parenteral, topical, rectal, inhaled, ophthalmic, buccal and sublingual route of drug administration.


What is a semi-solid dosage form?

Semisolids are neither solid nor liquid they are a combination or mixture of both and are used for both local and systemic effects. It is intended used as drug carriers that are transported topically through the skin, rectal tissue, buckle tissue, urethral membrane, outer ear lining nasal mucosa, and cornea, etc.
The drug substances are generally applied to the skin in the form of semi-solid formulations for topical treatment of skin diseases or to improve the condition of the skin. The skin can also be recognized as an alternative option of entry for systematically acting drugs since many patients particularly children and elders have faced problems taking medicines orally or the parenteral route.

Types of semisolid dosage forms:

Semisolid dosage forms can be classified into two types, internal and external.
  • Internal: examples- suppositories, and pessaries, etc.
  • External: examples- ointments, creams, pastes, and jellies, etc.
Semi solid dosage form and its classification

Definitions: Semisolid dosage forms:

Creams: Cream is a semisolid dosage form for external use containing one or more active ingredients dispersed or dissolved in a suitable fatty base.
Ointments: Ointments are semisolid preparations for external use containing with or without active ingredients with a suitable ointment base, intended for application on the skin to soothe or heal wounds, scrapes, rashes, burns, or other skin problems.
Gels: Gels are semisolid preparations intended for application on the skin, containing hydrophilic or hydrophobic bases with gelling agents.
Paste: A paste is semisolid dosage forms containing a high proportion of finely powdered medicaments with a suitable fatty base intended for topical application.
Poultices: A poultice is a semi-solid made up of a soft, moist mass created by wetting a solid absorbent material. It is for external use containing active ingredients applied to the skin to hold the dressing and protective.

Ideal properties of semisolid dosage forms:

Physical properties: Non-gritty, smooth texture, elegant in appearance, non-hygroscopic, non-greasy, and non-staining.
Physiological properties: Miscible with skin secretion, non-irritating, do not alter membrane or skin functioning, and have a low sensitization index
Application properties: Easily applicable with efficient drug release and high aqueous washability.
Storage properties: Its store temperature should not exceed 25°, Should not be allowed to freeze and stored in a well-closed container.

Mechanism of drug penetration through the skin:

Three possible entry macro routes to the viable tissue:
1. Via the sweat ducts
2. Across the continuous stratum corneum
3. Through the hair follicles with their associated sebaceous glands

Factors affecting semisolid dosage forms:

  • The medication incorporated into the semisolid base should reach their site of action, for the effectiveness of the formulations. The skin, on the other hand, acts as a barrier, preventing molecules from the administered medications from entering the body.
  • Physio-chemical and biological are the two major factors that affect the dermal penetration of the drug.

List of excipients or additives used in semi-solid dosage forms:

  • Sweetening agents
  • Solubilizing agents
  • Flavoring agents
  • Coloring agents
  • Preservatives
  • Antioxidants
  • Thickening agents
  • Binding agents
  • Suspending agents
  • Lubricants
  • Solvents
  • Perfumes

Packaging and storage of semi-solid dosage forms:

  • Aluminum, metal, or plastic tubes are used to package ointments and other semisolid formulations.
  • The tubes are tested to ensure that they are compatible and stable with the intended product.
  • Tubes used to pack the final topical product are easier to use for patients, lighter, compatible with most drugs and excipients, cost-effective, and offer better protection against external contamination and environmental conditions.
  • Tubes of aluminum generally are coated or laminated to eliminate any interactions and protect from moisture.
  • All containers are sterilized before being filled.
  • Semisolids should be store in tightly closed containers to avoid contamination and in a cool environment to avoid product separation due to heat (temperature).
  • Light-sensitive preparations are packaged in light-resistant containers when necessary.  
Commonly asked questions o dosage forms are as follows.

Which dosage form is semi-solid oil in water emulsion?
Creams are semi-solid emulsions of oil and water that come in two types: oil-in-water (O/W) and water-in-oil (W/O).

How are the ointments classified?
Ointments are classified based on penetration and the basis of therapeutic use.

What is the advantage of a semi-solid dosage form?
The major advantage of a semi-solid dosage form is that it can be applied directly to the affected area, has a longer duration of action, and does not require oral administration.


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Friday, April 2, 2021

Advantages and Disadvantages of Gas Chromatography

Chromatography has evolved, from paper chromatography to TLC and chromatography to instrumental techniques including GC and HPLC. Gas chromatography (GC) is the significant analytical method for the separation of volatile compounds in a mixture by injecting a liquid or gaseous sample into a mobile phase, usually called the carrier gas, and passing the gas through a stationary phase. The mobile phase consists of an inert gas it may be nitrogen, helium, or argon and the column can be packed or capillary they can available in different diameters and lengths as per the requirement of the sample.
This kind of chromatography isolates analytes based on the volatility of analytes. The more volatile compound will be separated rapidly, whereas the less volatile compound will gradually be eluted from the column. The gas chromatography follows the principle of the partitioning of volatile compounds with mobile phase and stationary phase.
Several detector options are available with high sensitivity, to detect a wide range of samples that is not possible with other chromatographic techniques. The different types of GC detectors are flame ionization (FID), thermal conductivity, nitrogen phosphorous, photo-ionization, electron capture, flame photometric, electrolytic conductivity detector, and mass spectrometer, etc.

Advantages of gas chromatography (GC):

  • The major advantage of gas chromatography is its high sensitivity, resolution, and separation ability, which allows it to separate a wide range of volatile compounds.
  • It can be upgraded to a mass spectrometer (MS), which is used to determine the mass-to-charge ratio of ions.
  • It comes with a variety of detectors and injectors that can be used for various pharmaceuticals as well as other applications.
  • Gas chromatography can analyze a sample much faster than other chromatographic techniques.
  • It is a robust method of separation that gives the superior signal-to-noise ratio.
  • It only takes a very small amount of sample to inject, and its detectors are extremely sensitive, allowing it to detect extremely low concentrations (ng-pg).
  • As per the requirement of the molecule, there are different types of GC columns are available in many diameters and lengths.
  • Gas chromatography is easy, automated, and has quick analysis of data which gives comparatively high precision, accuracy, and reproducible results.
  • Operational parameters such as flow rate, temperature, and pressure, etc. are easy to change even during chromatographic runs.

Disadvantages of a gas chromatography (GC):

  • The major disadvantage of GC is that only volatile and thermally stable compounds can be separated using gas chromatography.
  • Detectors which are used in the GC are destructive, except for MS.
  • Selectivity in HPLC or TLC is also better as a mobile phase can be easily changed. In GC, you can just modify the temperature of the column and oven, but you cannot change the mobile phase as it has a constant flow of carrier gas (helium, nitrogen).
  • Since hydrogen gas, which is used for flame, is highly flammable, care must be taken when using it.
  • It is impossible to recover individual sample components.

Commonly asked questions on gas chromatography are as follows.

What is the advantage of gas chromatography over liquid chromatography?
The major advantage of gas chromatography over liquid chromatography is that, as compared to high-performance liquid chromatography, the column length of GC is longer, allowing for the separation of more complex sample mixtures with high resolution.

What is the advantage of GC over TLC?
The major advantage of GC over TLC is that the GC is an automated quantitative technique in which software can offer precise data such as peak area, resolution, tailing factor and height, etc. Whereas TLC is only separates the compounds and is not for quantitative analysis.

What are the disadvantages of hydrogen in gas chromatography (GC)?
It can decrease the resolution of the chromatogram, hydrogen can react with unsaturated components on the metal surface, and in GC-MS it can reduce the efficiency of turbo molecular vacuum pump these are some disadvantages of hydrogen in GC.


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Difference between TLC and Paper Chromatography

The major difference between TLC and paper chromatography is that the TLC uses the stationary phase as alumina, silica, and its compositions, whereas in paper chromatography, specialized cellulose paper is used as a stationary phase to separate the analytes.
 
TLC and paper chromatography both are separation techniques of chromatography, which are used to separate the components or biomolecules such as carbohydrates, amino acids, and proteins. As a stationary phase, the paper chromatography uses cellulose paper, and the separation mechanism depends on the solid-liquid adsorption. The same adsorption mechanism uses in thin layer chromatography, depending on solubility in the mobile phase the molecules or components are separated on the stationary phase.

Particle separation in both paper and thin-layer chromatography is based on the polarity of the molecules on the stationary and mobile phase. After the chromatograph is completed, the different spots will appear, and the Rf factor will be determined.

Thin Layer Chromatography:

TLC is a separation technique of chromatography, which works based on the solid-liquid adsorption of compounds. It has a stationary phase of silica gel or alumina and a solvent in the form of a mobile phase, where the particles are separated based on their polarity towards both phases. In TLC the colored compounds appear as colored spots and colorless compounds are seen under UV light (UV cabinet) or using a spraying solution (Ninhydrin).

Paper Chromatography:

Paper chromatography is a separation technique used to separate compounds based on their liquid-liquid adsorption and solubility of the compound. The paper acts as a stationary phase and the mobile phase is liquid, and the particles are isolated according to their polarity toward both phases. In paper chromatography, the colored compounds appear as colored spots and colorless analytes are seen under using a spraying solution (Ninhydrin).

The key differences between thin layer chromatography (TLC) and paper are as follows:

  • TLC is based on the principle of "adsorption," whereas paper chromatography is based on the principle of "partition".
  • TLC is based on solid-liquid absorption whereas paper chromatography is based on solid-liquid absorption.
  • The glass plates coated with silica gel acts as the stationary phase in TLC whereas the water trapped in the cellulose filter paper acts as a stationary phase of paper chromatography.
  • Thin-layer chromatography takes more time in preparation, whereas paper chromatography takes less preparation.
  • TLC allows the use of corrosive reagents, while paper chromatography does not because the corrosive agents may damage the paper. This is due to the TLC plate is resistant to strong solvents and color-creating agents.
  • Paper chromatography rapidly separates the molecules whereas thin layer chromatography requires more time.
  • In TLC the individual spots of solutes can be seen under UV-lamp whereas in paper chromatography cannot be evaluated under the UV light.
  • The development of chromatogram takes place (flow of mobile phase) in paper chromatography can ascending, descending, radial, and two-dimensional whereas the flow of mobile phase in TLC chromatogram develop in ascending order.
 
  
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Thursday, April 1, 2021

Ideal properties of semisolid dosage form

A pharmaceutical dosage form is a physical form of a drug, such as a solid, liquid, or gas, that is delivered in its proper form to specific sites of action within the body. The commonly used dosage forms include tablets, solutions, capsules, injections, semisolids, and aerosols they deliver the active pharmaceutical ingredient using different routes of drug administration such as oral, parenteral (Injection), topical, sublingual, and buccal.

Semi solids are topical dosage forms intended for therapeutic, protective, or cosmetic and can be used as drug carriers that are transported topically through the skin, outer ear lining nasal mucosa, rectal tissue, buckle tissue, and cornea. Semi solids contain one or more active pharmaceutical ingredients homogeneously dispersed (dissolve) in a suitable base and any appropriate excipients. Ointments, cream, pastes, gels, rigid foams, and plasters, etc. are examples of the semi-solid dosage form.

Ideal properties of semi solids:

Various routes and dosage forms are used to make the drug more effective in which topical or semisolid formulation is ideal for the skin.
 
Physical properties:
  • It should have a smooth texture
  • It should be elegant in appearance
  • It should be non-dehydrating
  • It should be non-gritty
  • It should be non-greasy and non-staining
  • It should be non-hygroscopic
Physiological properties:
  • It should be non-irritating
  • Do not alter membrane or skin functioning
  • It should be miscible with skin secretion
  • It should have a low sensitization index
Application properties:
  • It should easily applicable with efficient drug release
  • It should have a high aqueous washing ability
Storage properties:
  • Its store temperature should not exceed 25° degrees
  • Should not be allowed to freeze and stored in a well-closed container
Ideal properties of semisolid dosage form

Ingredients desirable for semisolid dosage form:

  • Bases
  • Humectants
  • Preservative
  • Antioxidants
  • Gelling agent
  • Emulsifier
  • Buffers
  • Permeation enhancer

Ideal properties of the base which used in semi solids:

The base is the most essential ingredient used in the semisolid dosage form. Ointment bases not only work as carriers for pharmaceuticals, although they also regulate the amount of absorption of medicaments incorporated in them.
  • It should be inert, non-irritating and non-sensitizing
  • It should be compatible with the skin pH and the drug
  • It should be a good solvent and/or emulsifying agent
  • It should be emollient, protective, non-greasy, and easily removable
  • It should release medicaments readily at the site of application
  • Pharmaceutically elegant and possess good stability

Factors that affect skin penetration:

Biological and physio-chemical are the two major factors that affect the dermal penetration of the drug.
Biological factors influencing skin absorption are skin condition, skin age, blood flow, region skin site, skin metabolism, and species difference, etc.
Physio-chemical factors influencing skin absorption are skin hydration, temperature and pH, diffusion coefficient, the concentration of the drug, partition coefficient, and molecular size and shape.
 
 
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