Evaluation of Aerosols | Pharmaceutics

Evaluation of pharmaceutical aerosols can be done by a series of physical, chemical, and biological tests to ensure proper performance of the package and safety during use and storage.

Flammability, Combustibility, Flash point, Flash Extension & Flashback, Vapour Pressure, Density, moisture content, Propellants, Valve Discharge rate, Foam stability, Net Content, Spray Pattern, meter value, safety,
Evaluation of Pharmaceutical Aerosol

1. Flammability & Combustibility

               a) Flash Point

               b) Flash extension & Flashback

2. Biological Testing

  1. i) Therapeutic efficacy/activity &
  2. ii) Toxicity

3. Physicochemical characteristics

 i) Vapour Pressure

ii) Density

iii) Moisture content

iv) Identification of Propellants

v) Concentration propellants ratio

4. Performance

               a) Aerosols valve discharge rate

               b) Leakage

               c) particle size determination

               d) Foam stability

               e) Net content

               f) Spray pattern

               g) Dosage with meter valve

1. Flammability & Combustibility

a) Flash Point

In order to determine the flash point of an aerosol, two basic apparatus types are available which are an open cup and closed cup.

Apparatus: Open Cup Tag Apparatus

Flash-point test is done by cooling the temperature of the aerosol product to 25F.

Test liquids temp. is allowed to increase slowly & temp. at which vapors Ignite is called as Flash Point.

Open cup tag apparaturs, Aerosol, Flash point
Open Cup Tag Apparatus

Closed cup tests

Closed cup tests purpose to simulate the situation of a fluid spill in a closed environmental condition.

In closed cup tests to determine the flash point the investigated sample is placed inside a sealed test cup and introduced to a potential ignition source, determining the temperature at which the sample flashes.

An open cup apparatus will constantly give a higher flash point than a closed cup one as the open cup permits loss of internal vapors to the atmosphere above the apparatus.

b) Flash extension & Flashback

This type of evaluation test is also known as the flame projection test. Product is sprayed through an open candle flame for about 4 seconds at a fixed distance of 6 inches. (15 cm), & the flame’s extension is measured in (cm) and recording the length of the flame projection. An aerosol product is judged flammable if its flame extends 18 inch. (46 cm) or more through an open flame, or if the flame flashes back to the actuator. 

2. Biological Testing

i) Therapeutic efficacy/activity

  • For Inhalation Aerosols is depends on the particle size.
  • For Topical Aerosols is applied to test areas & adsorption of therapeuticingredient is determined.

ii) Toxicity

  • For Inhalation Aerosols:- exposing test animals to vapor sprayed fromAerosol container.
  • For Topical Aerosols:- Irritation & Chilling effects are determined

3. Physicochemical characteristics

PropertyMethod
Vapour PressureCan Puncturing Device
Pressure Gauge
DensityHydrometer
Pycnometer
Moisture contentKarl Fisher method
Gas Chromatography
Identification of Propellants Gas Chromatography
IR Spectroscopy
Physicochemical characteristics of Aerosols

4. Performance

a) Aerosols valve discharge rate

  • Content of the aerosol product of known weight is discharged for a specific period of time.
  • By reweighting the container after the time limit, the change in the weight per time dispensed gives the discharge rate (gram per second).

b) Leakage

  • It is done by measuring the Crimp’s dimension & comparing. Final testing of valve closure is done by passing filled containers through water bath.

c) particle size determination

Particle size of aerosol product are determined by Cascade Inspector and light scattering decay.

Cascade Inspector

Principle: Stream of particles projected through a series of nozzle and glass slide at high velocity, larger particles are impacted first on lower velocity stages and smaller particles are collected at Higher velocity stage.

Light scattering decay

Principle: An aerosol settles under turbulent conditions the change in the light intensity of a tyndall beam is measured.

d) Foam stability

 some foam have a lifetime of a limited few seconds and those known as “quick breaking” foam, while other foams can persist up to hours.

Various Methods to check foam stability are:

  • Visual methods
  • Time for given mass to penetrate the foam &
  • Time for given rod that is inserted into the foam to fall.
    Rotational viscometer

e) Net content

  • Tared Cans that have be placed on to filling line are reweighted and the different in the weight is equal to the net content.
  • In destructive method, weighting a full container and then dispensing as much as possible of the content. The content are then weighted. This gives the net content.

f) Spray pattern

  • The method is based on impingement of spray on piece of paper that has been treated with Dye-Talc mixture.
  • The particles that strike the paper cause that die to go into solution and to be added onto paper.

g) Dosage with meter valve

  • Reproducibility e of disease can be determined by assay technique
  • Assay technique
    • Accurate weighing of field container followed by dispensing of several dosages.
    • Containers are reweighted and difference in weight divided by the number of dosage dispensed gives average dose.

QUALITY CONTROL TESTS

It includes the testing of:-

1. Propellents
2. Valves, Actuator, Dip Tubes
3. Containers
4. Weight Checking
5. Leak Testing
6. Spray Pattern Testing

1. Propellent

Vapor pressure and density of the propellant are determined and compared with-specification sheet. Parameter Tested By Identification Gas Chromatography IR Spectroscopy Purity and acceptability Moisture, Halogen, Non-Volatile Residue determinations

2. Valves, Actuator, Dip Tubes

  • Sampling is done according to standard procedures as found in Military Standards ―MIL-STD-105D
  • For metered-dose aerosol valves, test methods were developed by
    • Aerosol Specifications Committee‘
    • Industrial Pharmaceutical Technology Section
    • Academy Of Pharmaceutical Sciences
  • The objective of this test is to determine magnitude of valve delivery & degree of uniformity between individual valves.
  • Standard test solutions were proposed to rule out variation in valve delivery.

3. Containers

Containers of aerosol are made of tin-plate, aluminum, stainless steel, and certain types of glass. One of the important criteria for the selection of an aerosol container is withstood internal created pressure as high as 140–180 psi at 130°F.

Both the coated and uncoated containers are evaluated for defects in the inner lining. Quite a lot of quality control aspects and assessment parameters are applied according to the type of container used.

4. Weight Checking

This test is done to check the accuracy of the filling procedure and assurance of uniformity of the final weight of the product.

5. Leak Testing

Leal testing is done by determining the crimp’s measurements.

This test involves allowing the filled containers passing through a water bath and final testing of valve closure is done. Pass the crimped aerosol containers through the water bath. If any leaks are present, the evolution of air bubbles can be observed and the container is rejected.

Bestowing to this test, leakage is defined as the weight change of the same container before and after being stored in a vertical position at 25°C±2°C for a minimum of 3 days. According to the USP-NF, 12 pressurized containers selected at random, aerosol dispensers are selected and weighed in mg, and this is considered as the weight before the positioning (W1). Allow the filled tested container to stand in an upright correct position at room temperature for at least 3 days, and weigh of each container should be determined again, finding the weight in mg of each container as (W2). The time during which the containers were under test (T) is determined in hours. Ultimately, the leakage rate of each container is calculated in mg/year as follows.

6. Spray Pattern Testing

Spray pattern, evaluation, Aerosol, Pharmapedia
Spray pattern test

This test is carried out to inspect for defects in valves and spray pattern as well as to clear dip tube of pure propellant &concentrate .The sprayed particles that strike on the surface of the substrate testing paper cause the dye to be converted into solution and to be absorbed onto the paper.

Evaluation of Packaging components of Aerosol

I. Protection

II. Compatibility

III. Safety

I. Protection

  • A light-resistant container that proposed to offer protection from light was evaluated by performing the Light transmission test
  • Water Vapor Permeation test, the capability of a container closure system to protect against transmission of moisture could be evaluated. 

II. Compatibility

A container component must be compatible with a dosage form/medicament.

III. Safety

For this test, the containers is evaluated for physicochemical tests.


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2 thoughts on “Evaluation of Aerosols | Pharmaceutics”

  1. Pingback: Pharmaceutical Aerosol | Pharmacy Notes | The Pharmapedia

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