3
Health Product Testing
3.1 Introduction
Modern medicines, toiletries and cosmetics are required to meet exacting standards with regard to
their quality, safety and efficacy, because of their direct interaction with the body. Imagine buying a
packet supposed to be paracetamol tablets, but which had been mispacked, and were in fact
laxatives!! Wouldn’t that give you the s…?
In Australia, the Therapeutic Goods Administration oversees the development of new products
and the manufacturing of existing ones. Inspectors from this government agency perform random
inspections of facilities responsible for manufacturing and testing of pharmaceuticals, whether they
are prescription or over-the-counter products. Testing and production records must be kept for seven
years, so that if any problem develops in the medium term, it can be traced back, the records can be
used to prove that the manufacturer met all standards required of it.
For non-therapeutic products such as toothpaste and shampoo, the legislative requirements are
less, because of the problems caused by manufacturing problems should be less. Even here, however,
health problems could result: toothpaste with excessive fluoride may result n dental problems, rather
than solutions.
The testing procedures for health products use the basic set of analytical techniques you are by
now very familiar with. Techniques capable of analysing organic compounds will be most important
here, and elemental techniques will be more used for impurity checks.
CLASS EXERCISE 3.1
List techniques suitable for analysis of organic compounds.
The reasons for testing health products are somewhat different to those for steel or paint:
•
identification of raw materials
•
assay of active ingredients
•
checking for levels of impurities
•
determining appropriate storage conditions
•
physical properties
3.2 Identification
Raw material supplies for the industry tend to mostly white powders and colourless liquids. While it
is the supplier’s responsibility to make sure that the one tonne pallet of sacks do contain paracetamol
as it says on the label, it is necessary that the user of the raw materials confirm that this is correct.
3. Health Product Testing
CLASS EXERCISE 3.2
(a) How would you check the identity of a pure organic compound?
(b)
How would you check the identity of an organic compound, supplied as a solution in water?
(c)
How would you check the identity of a substance, whose active form is one particular optical
isomer?
3.3 Assay
An assay is simply the analysis of the material to determine the concentration of the active substance.
This could be performed on the raw material, once identified, or on the final product. For some
complex products with many components, such as shampoos, it can be quite difficult to analyse each
component.
CLASS EXERCISE 3.3
(a) Why would you assay a sample of raw material, after it is has been confirmed that it is the right
substance?
(b)
Why would you assay the final product (tablet/powder/lotion/cream etc)?
(c)
How would you analyse the concentration of an organic compound in a health product?
Industrial Products (Testing)
3.2
3. Health Product Testing
3.4 Impurity checks
It is impossible to eliminate impurities in any manufacturing process, so all that can be done is make
sure that the impurities that do occur, are at levels that will not cause problems. The tests for
impurities may be done in two different ways, depending on the nature of the impurity:
•
quantitative analysis to determine the concentration
•
semi-quantitative (limit) tests that give a positive/negative result depending on whether the
impurity is above a certain concentration
Some examples of limit tests include:
•
whether an impurity is visible or not on a thin layer chromatography plate?
•
is there any soluble matter in the product (eg in barium sulfate used in X-ray work)?
•
does the addition of a specific colour-forming reagent show an absorbance above a specified
value?
•
is there a peak in the GLC at X minutes with a peak area greater than Y?
Limit tests will often be quite simple to perform. However, regardless of the complexity of the test,
the actual concentration of the impurity being checked for is not important. What is important is
whether or not it is outside acceptable limits.
3.5 Storage conditions
All pharmaceutical products are required to have a use-by date, as will other health products. This
means that the product remains equally effective until that date as the day it was manufactured.
Common problems associated with storage of health products for long periods include changes in
moisture content, photodegradation, chemical decomposition, breakdown of the physical form (eg
loss of emulsion). Each of which cause a change in the composition of the product.
CLASS EXERCISE 3.4
What are possible consequences of product change as a result of extended storage?
To ensure that these problems do not occur, the packaging of the product will provide appropriate
storage conditions where necessary. These may be of the form of "Keep in a tightly closed container"
or "Keep away from light" or "Keep below 30°C".
Industrial Products (Testing)
3.3
3. Health Product Testing
3.6 Physical properties
The physical properties of non-pharmaceutical products are often as important as their chemical
composition, and may be a better, and certainly simpler, guide as to whether the product is properly
formulated.
CLASS EXERCISE 3.5
For the following classes of toiletries and cosmetics, name some important physical characteristics that
affect the performance of the product.
Product
Physical Properties
Toothpaste
Perfume
Moisturising cream
Shampoo
Some of the physical tests used include colour, odour, pH, viscosity, density, physical appearance.
Colour
This is carried out using either simple inspection techniques (if it is not an important diagnostic
parameter) or using spectra colour matching. The latter uses a modified UV-spectrophotometer and
involves the measurement of absorbances at a series of different frequencies using a number of
different lamp sources. It is similar to the equivalent test which is used in the paint industry.
Odour
This can be carried out by a simple smell test. In most cases this is adequate for the needs of the
industry, but in some special cases such as perfumes it is possible to obtain a smell profile be using
special gas chromatographic techniques (head space sampling).
pH
This is carried out using a standard pH electrode in the majority of cases. This parameter is extremely
important in the cosmetics industry as the skin and hair can be greatly affected by alkaline or acid
substances. A good example is found in hair shampoos where they must carefully match the pH of the
human scalp (which is normally slightly acidic pH 5) to prevent causing stimulation of the sebaceous
gland which make hair too oily. Similarly if the pH is too alkaline it causes splitting of the ends of the
hair (known as split ends) as the protein in the hair is denatured.
Viscosity
Many cosmetics are applied to the skin in lotions and creams and it is important that they behave
correctly when this is carried out. If they are too viscose they will be sticky, or if they are not viscose
they will be runny.
Viscosity is determined by instruments such as capillary and Brookfield viscometers. The former
works by measuring the time taken for the liquid to move a certain distance through a capillary tube.
The latter measures the force required to rotate a stirrer blade at a particular rate, and this is related
to the viscosity. We will look further at the measurement of viscosity in the chapter on paints.
Industrial Products (Testing)
3.4
3. Health Product Testing
Specific Gravity (density)
This is carried out to determine fill weights for packaged goods. Often in the cosmetic industry the
labels of items quote the amount of product in mLs. It is generally easier however, to package goods
by weight, hence if the specific gravity is known a mass can be related to a volume of the product.
Specific gravity can be carried out in a number of ways including the use of pycnometers as used
in the paint industry, but additionally instrumental techniques such as density meters may be used.
Density meters provide a very accurate and extremely quick way of determining specific gravity. They
are hand held battery powered devices which simply involve placing a few mLs of the liquid into the
instrument and reading a result from a digital readout. A digital processor calculates the density by
vibrating it in a small glass tube and determining the period of the waveform produced.
3.7 Sampling
CLASS EXERCISE 3.6
(a) How would you obtain a laboratory sample of hand cream from a 1000 L mixing vessel which is
used to fill jars?
(b)
How would you obtain a sample of paracetamol for identification and assay from a thousand 20
kg bags that have just arrived by truck on ten pallets?
What You Need To Be Able To Do
•
•
•
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define important terminology
list and outline the significance of common testing procedures
explain aspects of analytical procedures
describe suitable sampling procedures
Industrial Products (Testing)
3.5