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Wednesday, March 31, 2021

Principle and applications of gas chromatography

Gas chromatography is the most widely used analytical method for quality control as well as identification and quantification of molecules in sample mixtures in many research and industrial laboratories. GC is frequently used in many applications of forensic and environmental as it allows for very small amounts of detection. A large range of samples can be determined as long as the analytes are enough thermally stable and are relatively volatile. Depending on the stationary phase used there are two types of GC, such as gas-liquid chromatography (GLC) and gas-solid chromatography (GSC).

Principle of gas chromatography (GC):

Gas chromatography is a technique for separating and quantifying vaporized analytes using an inert carrier gas (Nitrogen or Helium). The GC works on the same principles as column permeation chromatography, in which analytes are dissolved in the mobile phase and moved through a porous stationary phase. The basic principle involved in gas chromatography is partitioning, in which the analytes are distributed or partitioned between the two-phase i.e. stationary phase and mobile phase. The analytes are separated based on their affinity, the more affinity will elute slowly while lower affinity toward the stationary phase will elute rapidly from the column.

Gas-liquid chromatography (GLC) is the most regular form of GC, in that a stationary phase is a non-volatile liquid. The stationary phase can be coated on small inert solid particles packed in a coiled metal or glass column. Most analyzes of GC performed in the early years of GC using this kind of packed column. But, in recent years the capillary columns have been widely used since it has more separation efficiency and sensitivity. The carrier gas, sample injection port, column, column oven, and detector, etc. are the components essential to perform the process of GC.

Applications of gas chromatography (GC):

Pharmaceutical applications of GC: The gas chromatography is widely used for the qualitative and quantitative analysis of a sample of formulations and medicinal products in pharmaceutical production. 
Analysis of food, flavors, and fragrances: The quality and quantity of fragrances, flavors, and food products are required to be maintained; hence GC is used to analyze them. It is also used to determine the pesticides, and contaminants from foodstuff, vegetables, and fruits.
Applications of GC in the analysis of pesticides: The column of GC provides high resolution, efficiency, and exceptional inertness towards neutral, basic, and acidic compounds, therefore, it is appropriate for the analysis of volatiles and pesticides.
Applications of gas chromatography in academic research: GC-MS is the most powerful technique, it is used for the identification and characterization of molecules, which provide high resolution compared to the HPLC column.
Environmental applications of gas chromatography: GC is the most generally used technique for the identification of organic molecules in environmental samples. 
Applications of GC in clinical and forensic purposes: In several fields of forensic science the gas chromatography is used, ranging from the analysis of crime investigations, alcohol, and drug abuse. It is also essential in clinical applications to the analysis of drugs in the blood.
Applications of GC in a variety of industries: Gas chromatography has wide applications in many industries such as the petroleum industry, food industry, beverage industry, pharmaceutical industry, 
chemical industry, and gas industry, etc. 

Applications of gas liquid chromatography: 

A major trend in the field is combining substantial fractionation properties of gas-liquid chromatography with better analytical properties of instruments such as ultraviolet (UV), infrared spectrophotometer (IR), mass (MS), and NMR. In its application for chemical problems, the system must distinguish between two functions operating. The first is as a tool for isolation. In this capacity, it is unmatched, applied to biochemical systems, metal-organic and complex organic.

The second is to offer a means to complete the analysis. Here, the retention time of the compound is working for qualitative detection, while the peak area/height gives quantitative information. In comparison to other approaches, gas-liquid chromatography is a relatively underutilized analytical technology, as it is working with volatile components.


Commonly asked questions on chromatography are as follows.


Which factors influence the separation of the components in gas chromatography?

The separation of the components in GC is affected by the vapor pressure, length of the column, the polarity of analyte versus the polarity of stationary phase on the column, the temperature of column and oven, the flow rate of carrier gas and amount of sample injected.


What is the most commonly used detector in gas chromatography?

There are many types of detectors are used in gas chromatography such as flame ionization detector (FID), thermal conductivity detector (TCD), mass spectrometer (GC/MS), thermal conductivity detector (TCD)and electron capture detector (ECD), but out of these, the flame ionization detector is most commonly used detector in gas chromatography.


What is the major difference between GC-MS and LC-MS?

Both GC-MS and LC-MS are separation technique used to separate the compounds. The major difference between GC-MS and LC-MS is that the in GC-MS mobile phase uses as inert gases such as nitrogen or helium, whereas LC-MS uses a solvent or mixture of solvents as its mobile phase.


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Monday, March 29, 2021

HPLC column care and maintenance

The column is such an essential part for the separation in high-performance liquid chromatography, hence the proper care and maintenance of the column are needed for better performance and longer life. Every chromatographer knows the importance of columns in HPLC analysis, since the resolution, theoretical plate number, peak symmetry, tailing factor, and system suitability depend on column performance.

Column conditioning:

Every reversed-phase HPLC column should be conditioned for the first time use, following long-term storage, and when the significant changes in the mobile phase. The mobile phase utilized in the conditioning ought to be similar to those used in the consequent chromatography.
The general procedure of column conditioning is as follows:
1. Wash the column with about 3 column volumes of aqueous mobile Phase with a low flow rate.
2. Run linear gradient system from 100% aqueous mobile phase to 100% organic mobile phase up to 2-3 column volume at the identical flow rate as above.
3. Equilibrate the column on a minimum of 5 column volumes with the organic mobile phase, until the monitor signals get stable.
4. If you change the mobile phase system, a blank run should be done to verify any impurity that may emerge in the mobile phase.


Table of contents

 

Column conditioning

Column cleaning

Column storage

Regeneration of the reversed-phase column

Important points

Column cleaning:

Regularly cleaning the HPLC column is essential, particularly when dealing with samples that have any column foul contaminants and particulate matter. Increased back pressures, fluctuating baseline, and loss of resolution are all signs that the column may require to be cleaned. In silica-based reversed-phase media, the peak has loss resolution because of peak branding and it may also be caused by dissolution of the matrix during regular use of mobile phase or buffer of above pH 7.
A typical procedure for cleaning an HPLC column is as follows.

  • All the solvent using in the analysis should be HPLC grade and filtered through the 0.45-micron nylon filter membrane and degassing is also necessary.
  • Equilibrate the column at a low flow rate with several column volumes of mobile phase containing HPLC grade water.
  • 100% - 20 column volumes of water
  • 50:50% - 20 column volumes of water: acetonitrile or methanol
  • 100% - 20 column volumes of acetonitrile or methanol.The buffer solutions are very harmful to the performance and lifespan of the column, hence wash the column with an appropriate volume of water, so that salt does not get accumulated in the column and system.

Column storage:

Reverse phase columns are based on silica gel so they should not be stored in an aqueous solution. This is because the silica has inherent instability under aqueous conditions. Silica-based reversed-phase columns are generally stored in pure organic solvents, for example, methanol, which should be free from additives or TFA.

Regeneration of the reversed-phase column:

The RP-HPLC columns include C8, C18, CN C1, C30, C4, and phenyl stationary phases. To wash and generate the column, flush it with the following solvents.

  • 20 column volumes of 95:5% of water: acetonitrile (v/v)
  • 20 column volumes of 100 % of acetonitrile
  • 5 column volumes 100 % of isopropanol
  • 20 column volumes 100 % of hexane
  • 5 column volumes 100 % of isopropanol
  • 20 column volumes 100 % of acetonitrile
  • 20 column volumes of water: acetonitrile (95:5 v/v)
After washing with this sequence of solvents, the column needs to re-equilibrate with your mobile phase composition.

Important points:

Since almost 90% of the separation is working using reverse phase chromatography (RP-HPLC), some important points to consider in protecting and improving the life and performance of HPLC columns are listed below.
  • Properly install the column when you change or replace it.
  • Confirm the efficiency of the new column supplied by the vendor.
  • The column should be protected from knocks, bumps, and mechanical shock.
  • To protect against impurities and other foreign particulates, always use a guard column.
  • Always use HPLC grade solvents (methanol, Acetonitrile, and water, etc.) for analysis.
  • To exclude impurities and foreign particles, filter out the mobile phase using 0 .45 μ and before injecting the sample filter the sample using a 0 .20 μ membrane filter.
  • Degas all mobile phases and samples before use for the analysis.
  • Always use freshly prepared buffer solution (phosphate, acetate, and formate, etc.) for analysis.
  • Before injecting the sample, saturate the column with the mobile phase.
  • Do not overload the HPLC column resulting in broad peaks of analytes.
  • If a column oven is available then maintain column temperature, and also maintain the room temperature.
  • Always maintain the pH of the buffer/mobile phase in the range of 2.0 to 9.5 pH.
  • Avoid using a viscous buffer. Phosphate buffer concentrations should be less than 20 mM.
  • Avoid injecting the highly acidic and basic sample into the sample loop, always neutralize the sample.
  • Do not inject biological samples directly into the HPLC injector.
  • Avoid any sudden pressure fluctuation during the analysis.
  • Do not work with high flow rates, it creates pressure
  • Periodically check the performance of the column with the standards and do not operate HPLC system at back pressure greater than 4000 psi.
  • After each use, thoroughly clean the column with HPLC grade water and a suitable solvent.
  • Avoid storing the column with buffers, store it with the necessary solvents (methanol/acetonitrile), and do not allow it to dry. 

 

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Applications of Paper Chromatography in Pharmaceutical Analysis

Paper chromatography is one of the kinds of chromatography which is used for separating complex mixtures and identifying the analytes or components. The mixture gets separated since several analytes will attract more to the stationary phase (a piece of specialized paper) and several components can be attracted to the mobile phase hence they travel with it. Paper chromatography is typically utilized as an instructing to explain the basic functions of chromatography, however it is used in some pharmaceutical applications, let's check it out.
  • Reaction monitoring.
  • To ensure the control of the purity of pharmaceuticals.
  • For the study of ripening and fermentation.
  • For the analysis of the reaction mix in biochemical laboratories.
  • To detect contaminated substances in beverages and foodstuffs.
  • For the analysis of cosmetics.
  • Separation and purification techniques for components.
  • Forensic testing.
  • Performance-enhancing drug testing.

 It is the one of the oldest method used in several applications of chemistry. Let’s check some common applications of paper chromatography.

  • Paper chromatography is specifically used to separate mixtures of polar and non-polar molecules.
  • As it has a broad range of mobile phase or solvent system, it is used to identify unknown organic and inorganic components from sample mixtures.
  • Colored mixtures, such as pigments, are separated and identified using paper chromatography as a qualitative technique.
  • Sugar, nucleic acids, lipids, amino acids and some biomolecules can be easily detected using paper chromatography by spraying with sufficient reagents on stationary phase (e.g. Ninhydrin solution).
  • In the pharma field it is used for the determination of drugs, hormones etc.
  • It can be used in forensics testing and drug abuse, by comparing an unknown chromatogram with a known chromatogram which may aid in the investigation of a crime scene.
  • Paper chromatography can be used to analyze the fermentation and ripening process.

Commonly asked questions on paper chromatography are as follows.

What industries use paper chromatography?
Paper chromatography is commonly used in the analysis of various foods as well as in the pharmaceutical industries. It is mostly used in the analysis of colors that is used in the ice-creams, sweets, jams & jellies, beverages, and other foodstuffs.

What is the principle of paper chromatography?
The paper chromatography and thin-layer chromatography (TLC) works on the same principle that is partition chromatography in which the molecules are partitioned or distributed between liquid phases.

What factors affect paper chromatography?
Many factors affect paper chromatography such as the concentration of the sample, the length of the paper, type of solvent or mobile phase used, the thickness of paper, quality of paper used, and working temperature.

 

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Advantages and disadvantages of paper chromatography
Pharmaceutical Applications of Column Chromatography
Applications of HPTLC in Pharmaceutical Analysis
Applications of Thin Layer Chromatography in Pharmaceutical Analysis
Advantages and Disadvantages of Column Chromatography
What is the basic principle of HPTLC
what are the advantages of TLC over HPLC chromatography
Advantages and disadvantages of mass spectrometry
Advantages and disadvantages of ion-pair chromatography
Advantages and Disadvantages of Thin Layer Chromatography
Advantages and Disadvantages of UV Visible Spectroscopy 

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Saturday, March 27, 2021

Monophasic and biphasic liquid dosage forms

Monophasic and biphasic dosage are types of liquid dosage forms used for oral, external, special, and parenteral administration. However, there are some advantages, applications, and differences between monophasic and biphasic liquid dosage forms, so let's take a look at them.

Medication is more effective when they reach their site of action hence different dosage forms and routes are used to treat the various diseases. The dosage form is the medium that delivered medication to their sites of action within the body. It is a pharmaceutical product that contains a combination of drugs and excipients, formulated in a particular configuration and apportioned into a specific dose. Pharmaceutical dosage forms are classified as solid dosage form, semi-solid dosage form, liquid dosage form, and gaseous dosage form based on their physical form.
Liquid dosage forms are pourable pharmaceutical formulations that contain a mixture of active pharmaceutical ingredients (API) and excipients dissolved or suspended in an appropriate solvent or mixture of solvents. It is intended to provide a maximum therapeutic effect to patients who have trouble swallowing oral solid dosage forms.

Monophasic liquid dosage forms:

The monophasic dosage form is a single-phase system consisting of two or more components. It is the simple form of presenting the medication for rapid and high absorption of the drug. This is represented by the true solution and the true solution is a clear homogeneous mixture prepared by dissolving the solute in an appropriate solvent. The component of a solution that is present in large quantities is called "SOLVENT," while the component that is present in small quantities is called "SOLUTE."

Classification of monophasic liquid dosage forms:

Monophasic liquid dosage forms for oral use: example- linctuses, mixtures, syrups, elixirs, drops, and draughts, etc.
Monophasic liquid dosage forms for a particular use: example- nasal drops, ear drops, eye drops, eye lotions, mouthwashes, aerosols, gargles, inhalations, and throat paints, etc.
Monophasic liquid dosage forms for external use: example-lotions and liniments etc.
Parenteral solutions: example- intravenous, subcutaneous, and intramuscular injections, etc.

Advantages of monophasic liquid dosage forms:

  • It rapidly absorbs the drug than solid dosage form since the drug is already in the form of a solution.
  • Because it is homogeneous, it provides a more consistent dose than suspension or emulsion, which requires shaking.
  • It can be administered by various routes such as oral, parenteral, otic, ophthalmic, and nasal.
  • As compared with solid dosage forms (tablets, capsules) it is easy to swallow, especially for children and old patients.
  • The unpleasant taste and smell of the drug are masked by adding sweeteners and flavor-enhancing agents.

Disadvantages of monophasic liquid dosage forms:

  • It may undergo hydrolysis if exposed to direct sunlight, so it needs to be store in a cool and dark place.
  • The stability of the drug is reduced by hydrolysis or oxidation.
  • Water is used in the formulation as a vehicle that is susceptible to microscopic growth; as a result, a preservative is required.

Biphasic liquid dosage forms:

It is a liquid dosage form is one that has two phases; suspensions and emulsions are two examples of biphasic liquid dosage forms. A biphasic system consists of a solid dispersed state and a liquid continuous phase that can be aqueous or oily and is stabilized by the addition of a suspended agent. These are commonly taken orally or through the parenteral route, and they are also used for external applications.
It is used when the drugs are poorly soluble in the solvent. Drugs can be either liquid or solid from the dispersed phase of the system, when the solid drug is distributed in the dispersion medium; the formed system is called a suspension. When the liquid drug is delivered into the dispersion medium, the system form is called emulsion.

Classification of biphasic liquid dosage forms:

The biphasic liquid dosage forms have two types, emulsion and suspension.
Emulsion dosage form: It is a thermodynamically unstable system consisting of two immiscible liquid phases, one of which is dispersed as globules within the other and stabilized by an emulsifying agent. It has two types, water in oil type (w/o), and oil in a water type (o/w). Examples-application, liniment, and lotion, etc.
Suspension dosage form: It is a biphasic liquid or semi-solid dosage form, in which insoluble solid particles of the drug are homogeneously dispersed in a liquid or semi-solid medium. Examples- Gels, lotion, aerosols, inhalation, and eye drop, etc.

Advantages of biphasic liquid dosage forms:

  • It is used for the drugs that are insoluble in solution; therefore it is necessary to prepare an insoluble form of the drug, which is then administered as a suspension.
  • It exhibits higher bioavailability rates than other dosage forms.
  • Suspension can offer prolonged action of the drug since solid particles must be dissolved before absorption.
  • Two incompatible ingredients/drugs can be included in a dose, one in each phase of the emulsion.

Disadvantages of biphasic liquid dosage forms:

  • Not all drugs are compatible to formulate with biphasic form.
  • It is bulky and therefore difficult to handle, transport and store.
  • It is costly compared with the solid dosage form.

Difference between monophasic and biphasic liquid dosage form:

Liquid oral doses comprise a wide range of dosage forms, broadly classified as the monophasic and biphasic liquid dosage forms. The major difference between monophasic and biphasic liquid dosage forms is that the monophasic liquid dosage forms have a single homogeneous phase, whereas biphasic liquid dosage forms consist of two distinct phases. Both forms include at least one drug in formulation, monophasic forms are homogeneous and completely dissolve in liquid, whereas biphasic forms are not dissolved in a vehicle.

Commonly asked questions on dosage forms are as follows.

What is the classification of dosage forms?
Pharmaceutical dosage forms are classified based on physical form and route of administration, based on the physical form are solid, semi-solid, liquid, and gaseous dosage form.

How many types of emulsions are there?
There are two basic types of emulsions, oil in a water type (o/w) and, water in an oil type (w/o).

How many types of suspension are there in the pharmacy?
Based on the ratio of solids, suspension dosage forms are empirically classified as dilute or concentrated systems and based on the nature and behavior of solids, suspensions are classified as flocculated or deflocculated.
 
 
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Saturday, March 20, 2021

Difference between sustained and controlled release dosage form

The major difference between sustained and controlled release dosage forms is that in sustained medication the dose is maintained over a long period and the release of the drug is not fixed per unit time, however, in controlled forms, the release of the drug is very definite per unit time. Whereas, in controlled drug delivery drug is delivered locally or systematically at a predetermined rate for a specified time.

The drug is effective only when it arrives at the site of action therefore a variety of dosage forms and routes of administration are used to deliver the drug. The dosage form of a pharmaceutical product refers to its method of entering or delivering a biological system. The dosage forms are classified according to the physical form and route of administration.
According to physical form, the dosage forms are classifieds into solid dosage forms, semisolid, liquid, and gaseous dosage forms. According to the route of drug administration, the dosage forms are classifieds into oral, parenteral (injection), inhalation, topical, sublingual, rectal, nasal, buccal, and transdermal routes administration, etc.

Sustained release dosage form:

The purpose of sustained-release dosage forms is to release drugs at a predetermined rate so that a constant concentration of drugs is maintained for a specific time, according to the needs of the body throughout the treatment period.
The major advantage of developing sustained-release formulations is to modify and increase the performance of drug by increasing the time of drug action, reduce the frequency of dosing, reducing side effects, reducing the required dose employed, and providing the shortest possible time using the smallest amount of medication administered by the most appropriate route.

Controlled release dosage form:

Controlled drug delivery is that which delivers the active pharmaceutical ingredients (API) systematically or locally at a predetermined rate for a prescribed time. The controlled release drug delivery system employs drug encapsulating devices that allow for the controlled release of the drug over longer periods, which can range from days to months.
Controlled-release systems provide a sustained-release profile as well, but unlike sustained-release drug delivery systems, they are formulated or designed to produce predictable constant concentrations of active pharmaceutical ingredient (API), independently of the biological environment of the application site. This means that, unlike the sustained-release system, they are controlling the concentration of an active ingredient in the target tissue or blood, not just the release of the drug from the dosage form.

Here are some of the points of difference between sustained and controlled release dosage forms are mentioned.
  • sustained release dosage forms follow first-order kinetics, while controlled release dosage forms have followed zero-order kinetics.
  • In sustained release implies a slow release of the medication over a period of time and this release may or may not be controlled, Whereas the controlled release is a completely zero-order release, the medication releases over time irrespective of concentration.
  • sustained-release medication is restricted to oral dosage forms whereas controlled-release medications are used in a variety of administration routes, such as oral vaginal, and transdermal administration, etc.
  • In sustained release forms, the dosage is maintained for a long time and drug release is not definite per unit time, while drug release is predictable very definite per unit time in controlled-release forms.
Commonly asked questions on dosage forms are as follows.

What are the types of modified release dosage forms?
A variety of modified dosage forms are designed by pharmaceutical industries to reduce side effects as well as increase patient compliance by reducing the frequency of dosing. The classification of a modified release dosage form is sustained-release, prolonged-action, extended-release, targeted-release, delayed-release, repeat-action, and controlled-release dosage forms.

What is the importance of dosage forms?
Appropriate dosage forms are required to protect the drug from destructive influences of the atmospheric conditions such as moisture or oxygen, to deliver extended action of the drug through a control release mechanism to mask the unpleasant taste and odor, and to protect the drug from being destroyed from gastric acid of oral administration, etc.

What are the types of pharmaceutical tablets?
Different types of tablets in pharmacy are formulated and they can vary in size, shape, weight, hardness, thickness, dissolution, and disintegration. Compressed tablets, film-coated tablets, enteric-coated tablets, chewable tablets, sugar-coated tablets, effervescent tablets, buccal and sublingual tablets are some of the types of tablets.
 
 
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Thursday, March 18, 2021

Difference between Dissolution and Solubility

The major difference between dissolution and solubility is that the dissolution is a kinetic process, by which a solute in a solid, liquid, or gaseous phase dissolves in a solvent to form a solution, Whereas solubility is the maximum concentration of a solute that can dissolve in a solvent at a specified temperature, it is a thermodynamic process.

Dissolution and solubility are related to each other, yet there is a slight disparity amongst them. Dissolution is the procedure as solute dissolves up in medium (solvent), but solubility is the outcome of dissolution. In this process, the solid part refers to the solute, and the liquid is referred to as a solvent, several factors affect this type of reaction such as temperature, solute size, and solvent properties.
Before understanding the difference between dissolution and solubility it is important to know the three essential components involved in the term dissolution and solubility i.e. solvent, solute, and solution.
Solute: A solute is a compound that dissolves in a solvent.
Solvent: A solvent is a liquid that is used to dissolve a solute.
Solution: The mixture formed when a solute is dissolved in a solvent is referred to as a solution.
Solutes may be liquids, solids, or gas, and although solvents are usually liquids, they can also be solid and gaseous solvents.
Difference between dissolution and solubility

Below are some points of differences between dissolution and solubility are mentioned.
  • Dissolution is the capacity of solute to be dissolved whereas solubility is the rate of solute dissolving in a solution.
  • Dissolution is a kinetic process whereas solubility is a thermodynamic process.
  • In dissolution, solute dissolves in a solvent to form a solution whereas solubility is the outcome of dissolution.
  • Dissolution is measured in mol/s whereas solubility is measured in mol/kg.

Dissolution:

Dissolution is a kinetic process that is performed by the dissolution test apparatus (USP, IP, BP dissolution apparatus) for the oral solid dosage form and is used to find the rate of a solute dissolving in a solution, in which the process the solutes are always soluble in the medium or solvent.
Factors affecting dissolution:
  • Surface area
  • Physicochemical properties of the drug
  • The temperature of the process
  • The concentration of the solute
  • Viscosity and polarity of the solvent

Solubility:

Solubility is a thermodynamic process in which the chemical property refers to the ability of a particular solute, the substance, to liquefy in the solution or solvent. Solubility is used for finding out the solute capacity to be dissolved in a particular solvent quantity, in which the process solutes are not always soluble in the medium or solvent it depends on the solute properties.
Factors affecting solubility:
  • The concentration of the solute
  • The temperature of the system
  • The polarity of the solvent
  • The polarity of the solute
  • The pressure of the system
Commonly asked questions on solubility and dissolution are as follows.

How does solubility affect dissolution rate?
Both solubility and dissolution rate are two different phenomena. The solubility of the sample in a solvent may be poor, but its dissolution rate might be high. A solute, on the other hand, can be very soluble but take a long time to reach its final saturation concentration.

What is the advantage of dissolution testing?
The dissolution can determine the rate of release and the extent of absorption of the dosage forms, which is a major advantage of dissolution.

What is dissolution in chemistry?
A mechanism by which a solute in a liquid, solid, or gaseous phase dissolves in a solvent to form a solution is known as dissolution.
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Wednesday, March 17, 2021

Difference between emulsion and suspension

The major difference between emulsion and suspension is that the suspension is a heterogeneous mixture in which the dispersed particles are large and settle on standing, whereas the emulsion is a heterogeneous mixture of two immiscible liquids in which the dispersed particles do not settle on standing.

Suspensions:

The pharmaceutical suspension is a biphasic liquid or semi-solid dosage form, in which insoluble solid drug particles are homogeneously dispersed in a liquid or semi-solid medium. The internal phase is uniformly distributed in the external phase, resulting in a coarse dispersion. The internal phase is ranging in size from 0.5 to 5 m, while the external phase, which is generally aqueous in some instances, can be an organic or oily liquid for non-oral use.
The pharmaceutical suspensions are classified into four major parts according to their pharmaceutical use i.e. oral suspensions, parenteral suspensions, ophthalmic suspensions and, suspensions for external use.
  • A suspension is a heterogeneous mixture of large dispersed particles that settle upon standing.
  • The size of suspended particles more than 1000 nm, and is visible to the naked eye.
  • It can scatter light or opaque.
  • For the stability of the formulation, suspending agents are needed.
  • Both orally and topically applications are also possible with compounded suspensions.
  • Freezing should be avoided during storage as it will lead to aggregation.
  • Suspension dosage forms are also opaque when mixed but on standing, it's clear and separate.
  • It can be filtered out.
  • Solid particles are dispersed in any medium, which can be solid, liquid, or gas.

Emulsions:

The pharmaceutical emulsion is a thermodynamically unstable system that consists of two immiscible liquid phases, one of which is dispersed as globules within the other and is stabilized by a third substance known as an emulsifying agent. An example of an emulsion is oil and water they are immiscible and when mixed and shaken form emulsions.
Pharmaceutical emulsions are classified into two types 1. Oil in a water type (o/w), 2. Water in oil type (w/o).
  • An emulsion is a heterogeneous mixture of two immiscible liquids and a type of colloid and dispersed particles, which do not settle upon standing.
  • The dispersed particles range in size from 1 to 1000 nm and are invisible to naked eyes.
  • It can show the Tyndall effect
  • For the stability of the formulation, emulsifying agents are needed.
  • Topical and oral applications are also possible with compounded emulsions.
  • Freezing should be avoided during storage as it leads to cracking.
  • Emulsion dosage forms are opaque in appearance.
  • It cannot be filtered out.
  • The dispersed medium and dispersed phase in the emulsion are both liquids.
Difference between emulsion and suspension

Here are points are mentioned to understand the differences between suspension and emulsion.
  • Two substances in any phase of matter, such as solid, liquid, or gas, can be contained in a suspension, whereas an emulsion consists of only two immiscible liquids.
  • In emulsification, only stabilization is possible where you can make the emulsion more stable by using an emulsifier.
  • To increase product stability, emulsifying agents are required for emulsion, while suspending agents are required for suspension.
  • Suspensions are simple to separate, while emulsions may or may not be, it is depending on the state of matter in which particles are present in either of them.
Commonly asked questions on dosage forms are as follows.

What are the types of liquid dosage forms?
The liquid dosage forms are divided into two types based on phase: monophasic liquid dosage form and biphasic liquid dosage form. Some examples of liquid dosage forms are liniments, lotions, solution, draughts, syrups, linctuses, creams, mixtures, drops, mouthwashes, douches, elixirs, and eye drops, etc.

Is milk an emulsion or suspension?
Since the fat globules in milk are suspended in water, milk is oil in water emulsion.

What are the different routes of drug administration?
A route of administration is the path by which medication is taken into the body. Oral, enteral, parenteral (injection), topical, rectal, ocular, otic, sublingual, and buccal are some of the routes of drug administration.
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