Types of Assays in Chemistry

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Questions and Answers

What is the primary purpose of an assay?

To categorize natural and artificial materials into distinct groups

To quantitatively measure or qualitatively assess a target entity (correct)

To enhance the therapeutic effect of drugs

To identify the aesthetic properties of substances

What characteristic distinguishes a chemical assay from a bioassay?

Chemical assays require less manpower than bioassays.

Chemical assays are exclusively used for quantifying biological activity.

Bioassays are more cost-effective than chemical assays.

Bioassays are less precise when measuring a drug's concentration. (correct)

In which situation would a bioassay be indicated over a chemical assay?

When active principles of the drug are unidentified (correct)

When a chemical method is faster and simpler

When measuring high dose pharmacological responses

When the chemical composition of the drug is fully known

Which statement about bioassays is true?

Bioassays should be comparative against a standard drug. Signup and view all the answers

What is a common limitation of conducting a bioassay?

It is less sensitive than chemical assays. Signup and view all the answers

Which aspect is NOT covered by the principles of bioassay?

Bioassays should be able to separate interfering substances. Signup and view all the answers

How does a chemical assay compare to a bioassay in terms of time management?

Chemical assays are less time-consuming than bioassays. Signup and view all the answers

Which statement about immunoassays is accurate?

Immunoassays utilize the interaction between antigens and antibodies. Signup and view all the answers

What is a characteristic of a quantal bioassay?

It involves all or none responses. Signup and view all the answers

Which of the following is NOT a purpose of bioassays?

To determine the exact mechanisms of drug action. Signup and view all the answers

What is the main drawback of biological assays?

The effects in animals may not be the same as in humans. Signup and view all the answers

What does LD50 refer to in bioassays?

Lethal Dose for 50% of the population. Signup and view all the answers

Which of these tests uses a rabbit as a test animal?

Tubocurarine Chloride bioassay Signup and view all the answers

Which statement regarding accuracy limits of bioassays is accurate?

An accuracy of 20% of the true value is acceptable. Signup and view all the answers

Graded bioassays produce effects that depend on which factor?

Dosage, which produces a gradual effect. Signup and view all the answers

Which of the following substances would be tested using a rat in a biological assay?

Vitamin A Signup and view all the answers

Study Notes

Assay

Investigative procedure used to measure or assess the presence, amount, or activity of a target entity called the analyte which could be a drug, biochemical substance, or organic sample.

Types of Assays

Chemical Assay: Study of separation, identification, and quantification of chemical components in natural and artificial materials.
Immunoassay: Uses the interaction between an antigen and its antibody to identify and quantify the specific antigen or antibody in a sample.
Biological Assay: Testing procedure to estimate the concentration of a pharmaceutical drug in a formulated product or bulk material. The potency of the drug is compared with the standard by observing its effects on animals or human volunteers.

Comparison of Chemical & Bioassay

Chemical Assay

More precise
Less time-consuming
Less expensive
Active constituent & structure fully established
Less sensitive
Requires less manpower
Easy to handle

Bioassay

Less precise
More time-consuming
More expensive
Active constituent & structure not known
More sensitive
Requires more manpower
Difficult to handle

Indications of Bioassay

When the chemical method is unavailable, too complex, or insensitive to low doses (e.g., histamine).
When the active principle of a drug is unknown (e.g., insulin).
When the chemical composition of a drug is unknown (e.g., long-acting thyroid stimulator).
When the chemical composition of a drug is variable but it has the same pharmacological action (e.g., cardiac glycosides).
When the active principle cannot be isolated (e.g., posterior pituitary extract, insulin).
When the biological activity of a drug cannot be defined by a chemical assay (e.g., cis and trans forms of methylphenidate).
When it's not possible to separate interfering substances (e.g., Vitamin D).

Principles of Bioassay

All bioassays should be compared against a standard drug.
The standard and new drug should be, as far as possible, identical to each other.
The activity measured should be the activity of interest.
The degree of pharmacological response produced should be reproducible under identical conditions (e.g., adrenaline).
The method of comparison preferably (not essentially) tests the therapeutic property of the drug.
Individual variations must be minimized.

Classification of Bioassay

Quantal: All or none response in all individuals (e.g., digitalis-induced cardiac arrest in guinea pigs, hypoglycemic convulsions in mice by insulin). It's used to compare LD50 and ED50 and threshold response values.
Graded: The effect is produced gradually depending on the dose (e.g., contraction of smooth muscle preparation).

Accuracy limits of bioassay

An accuracy within 20% of the true value is considered good.
An accuracy within 10% of the true value is considered excellent.

Dependency of biological testing procedure

Biological assay depends on the size of the dose and potency of the drug.
The effect produced in animals might not be the same as that produced in humans (exceptions exist).

Partial list of official quantitative biological tests

Drug and Dosage Form	Test Animal(s)
Antibiotics	Suitable Microorganism
Insulin	Rabbit & Mice
Digitalis & other glycosides	Pigeon & Guinea Pig
Vitamin A & D	Rat
Parathyroid drugs	Dog
Posterior pituitary	Rat
Tubocurarine Chloride	Rabbit

Purpose of Bioassay

To compare a test sample with a standard substance to determine the quantity of the test required to produce an equivalent biological response.
To measure the pharmacological activity of a new or chemically undefined substance.
To test the response of living animals to the toxicity of chemical contaminants.
To investigate the function of endogenous mediators (e.g., in the development of the inflammatory response).
To determine the concentration and potency of an unknown substance.
To improve and maintain standards of environmental conditions that affect people's wellbeing.
To determine the specificity of a compound (e.g., penicillins' effectiveness against G+ve bacteria but not G-ve bacteria).

Preparation of standard

A selective representative sample of a substance that serves as a basis for comparison.

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Description

Explore the various types of assays used in scientific investigations, including chemical assays, immunoassays, and biological assays. This quiz covers the methods of measurement, assessment, and comparison of these techniques, highlighting their precision and applications in drug testing and analysis.