Pharmacy Balances and Weighing Techniques

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Questions and Answers

What is the maximum acceptable tolerance for error in pharmaceuticals?

± 10%

± 2%

± 5% (correct)

± 15%

How is % error calculated?

Measured value divided by Desired value

Error of measurement times 100%

Error of measurement divided by Quantity desired (correct)

Desired value minus Measured value

In the example provided, if the intended volume is 100 mL but the actual volume is 98 mL, what is the error of measurement?

2 mL (correct)

3 mL

5 mL

1 mL

What does accuracy refer to in the context of measurements?

The closeness of a measurement to the true value Signup and view all the answers

If you know the sensitivity of a balance, what can you calculate?

The % error when weighing any amount Signup and view all the answers

What is the prescribed sensitivity requirement (SR) for a prescription balance?

6 mg Signup and view all the answers

Which of the following is NOT a feature of electronic balances?

Requires manual calibration at all times Signup and view all the answers

For what reason must a balance be placed on a level solid surface?

To maintain accurate weights Signup and view all the answers

What does the term 'geometric dilution' refer to in pharmaceutical compounding?

A technique for ensuring uniformity in mixtures by using ratios Signup and view all the answers

What is a primary consideration when selecting a balance for pharmaceutical purposes?

Nature and quantity of the material Signup and view all the answers

What is the capacity of a typical prescription balance?

120 g Signup and view all the answers

Which of the following factors can affect an electronic balance's accuracy?

Temperature variations Signup and view all the answers

What is the function of a mortar and pestle in pharmaceutical compounding?

To grind and mix powders Signup and view all the answers

What is the purpose of trituration in pharmaceutical preparations?

To reduce the particle size or blend powders. Signup and view all the answers

Which material is most appropriate for triturating crystalline substances?

Wedgewood mortar. Signup and view all the answers

In the process of geometric dilution, what is primarily being ensured?

Homogeneity of the product. Signup and view all the answers

Which statement about mortars and pestles is true?

Glass is suitable for soft powders and semi-solids. Signup and view all the answers

What must be remembered when weighing substances during trituration?

The substance must exceed the lowest weighable quantity. Signup and view all the answers

Which option correctly describes sensitivity in the context of measurement?

It is calculated from the error tolerated and expressed in percentage. Signup and view all the answers

What is a characteristic of geometric dilution?

It is beneficial for mixing small amounts of material with large quantities. Signup and view all the answers

What is the primary function of mortars and pestles in pharmaceuticals?

To reduce particle size through comminution. Signup and view all the answers

Which materials should stainless steel spatulas not be used with?

Iodine and strong acids Signup and view all the answers

What is the primary use of a spatula in a laboratory setting?

Mixing cream or ointments Signup and view all the answers

How does levigation help in the preparation of a paste?

By reducing particle size and breaking down aggregates Signup and view all the answers

Which of the following is NOT considered volumetric glassware?

Erlenmeyer flasks Signup and view all the answers

What characteristic distinguishes volumetric pipettes from Mohr pipettes?

Volumetric pipettes deliver a fixed volume. Signup and view all the answers

Which statement about graduated cylinders is true?

Cylindrical graduated cylinders have better accuracy than conical ones. Signup and view all the answers

What is the appropriate volume measurement for using a graduated cylinder?

At least 20% of the cylinder's capacity Signup and view all the answers

What is the capacity range of volumetric flasks?

1 mL to 5000 mL Signup and view all the answers

Study Notes

Balances

Balances are used to measure the mass of objects.
Prescription balance is a type of balance that is required in every licensed pharmacy.
The sensitivity requirement (SR) of a prescription balance is 6mg.
The sensitivity requirement is the weight that will cause a specified change in the balance.
Electronic balances use electromagnetic force to restore the beam to neutral.
Electronic balances must be protected from electromagnetic fields and may be affected by temperature changes.
Balances should be kept on a level, solid surface, free from vibration, air movement, and dust.

Weighing

Weight is the force of gravity exerted on a mass.
The force of gravity varies with altitude.
Tolerance of ± 5% is acceptable for most pharmaceutical preparations.
The percent error can be calculated by dividing the error of measurement by the desired quantity and multiplying by 100%.
The lower weighable quantity (LWQ) is the smallest quantity that can be weighed at a desired level of accuracy.

Trituration and Geometric Dilution

Trituration is the process of grinding a drug in a mortar with a pestle to reduce particle size or blend powders.
Geometric dilution is a process used to mix a small amount of material with a much larger amount of solid or semi-solid material.
Geometric dilution is effective for mixing and ensuring product homogeneity.

Mortars and Pestles

Mortars and pestles are utensils used for small-scale comminution.
Comminution is the process of reducing particle size.
Mortars and pestles can be made of glass, porcelain, or Wedgewood material.

Spatulas

Spatulas are used primarily for mixing creams and ointments.
Stainless steel spatulas should not be used with substances that can corrode the metal, such as strong acids or iodine.
Modern stainless steel is usually safe for use with most materials.
Spatulas are commonly used for levigation.

Levigation

Levigation is the process of mixing powder with a small amount of liquid to form a smooth paste.
The liquid used helps to wet the powder and reduce particle size.
Levigation is often done with a flexible spatula on a glass slab or in a mortar.

Volumetric Glassware

Volumetric glassware is used to measure exact quantities of liquids.
Volumetric glassware includes pipettes, graduated cylinders, and volumetric flasks.
Pipettes are calibrated "to deliver" (TD), while graduated cylinders and volumetric flasks are calibrated "to contain" (TC).
Erlenmeyer flasks, beakers, and prescription bottles are not considered volumetric glassware and should not be used for measuring.

Pipettes

Pipettes are used to measure volumes smaller than 5 mL.
Volumetric pipettes deliver a fixed volume, while Mohr pipettes deliver variable volumes.
Pipettes should be filled using a bulb; mouth-pipetting is unacceptable and dangerous.

Syringes

Syringes are available in a variety of sizes from 0.5 to 60 mL.
Syringes are used for both parenteral and oral administration of medications.

Volumetric Flasks

Volumetric flasks are used to prepare specific volumes of solutions.
They come in sizes ranging from 1 to 5000 mL.

Graduated Cylinders

Graduated cylinders are used for measuring and transferring liquids when the volume is greater than 2 mL.
They can be made of glass or plastic and may be cylindrical or conical.
Cylindrical graduated cylinders are more accurate than conical ones.
When measuring liquids, it is important to select the device most appropriate for the volume being measured.

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Description

This quiz covers essential concepts related to balances used in pharmacy, including prescription balances, sensitivity requirements, and the principles of weighing. Participants will learn about the factors that affect accurate measurements and the importance of proper balance handling in pharmaceutical settings.