The process of standardization involves comparing a solution to a standard solution to determine its exact concentration.
The process of standardization involves comparing a solution to a standard solution to determine its exact concentration. In standard solutions, we use standard substances and know their concentrations accurately. Traditionally, we label standard solutions either as primary standards or secondary standards. A secondary standard solution is standardized through a primary standard. Secondary standards can be used for a variety of analytical experiments.
Materials that contain the substance of interest at a known concentration are called biological standards. Units of measurement can also be specified. New material can be tested using this standard to determine its concentration. Primary standards are therefore used as primary calibrators or primary reference materials.
Functions of these primary and secondary standards
- The standardization of volumetric solutions
- The purpose of this reference is to determine unknown concentrations using it
- The preparation of secondary standards
- Calibration of instruments.
Primary standards
Primary standards are chemicals or reagents that have particular properties, especially
1. This is an incredibly pure substance
Primary standard materials should have a high degree of purity, preferably 99.98%, meaning they must be a chemical that has been prepared from very pure materials. There are various grades of purity of chemicals in chemistry labs. The purity percentage appears on the label. It is a suitable material for primary standards when the chemical is pure to 99.98% or more.
2. High level of stability
It should have a high degree of stability which means it will not easily react when it is pure. A more accurate expression would be that it should be relatively inert. If a reagent is unstable or changes its properties over time, it may not be reliable, since it reacts easily with air, water, or other molecules. Unreliable and unstable chemicals cannot ever be used as standards.
3. As anhydrous as possible
Salt should be anhydrous, meaning that its molecular structure contains no water molecules.
4. There is less hygroscopicity
Having anhydrous properties is not enough. It is preferable if the chemical is less hygroscopic than water molecules are absorbed when the container is opened.
5. The molecular weight of this substance is very high
6. Easy to weigh
The pure nature of the material allows it to be weighed easily since its weight is a true representation of its actual molecular weight.
7. It must be available and ready for use
8. Ideally, it should be nontoxic
9. It shouldn't cost too much
Secondary standards
Laboratory standards such as those involved in producing chemicals, reagents, kits, or producing quality control materials for other businesses are considered secondary standards. Primary standards are used as primary calibrators or primary reference materials. Additionally, secondary standards are used in smaller labs for the calibration of control materials, which is used for analyzing unknown concentrations of substances. As such, secondary standards function primarily to perform external quality control on smaller laboratories. To apply the secondary standard to the primary standard, it must be standardized and compared.
To prepare the secondary standard solution, an aqueous solution of high purity must be used. Water must be deionized when used as an aqueous solvent. Standard solutions prepared without pure solvent are worthless (These points apply to primary standard solutions as well).
Similarly, individuals should check dates of manufacture, expiration dates, dates of receipt of high-grade chemicals, whether the conditions for their transport were followed or not, whether the seal has been damaged, its purity, and whether a standard reference material was used before using them.
Chemicals and reagents classified as secondary standards have certain properties, for instance
- Compared to the primary standard, it is less pure
- Stability and responsiveness are less than primary standards
- This solution, however, remains stable for quite some time
- A comparison has been made against primary standards
Chemicals that meet the requirements for being standard chemicals, but do not meet those of primary standards
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FAQs
They use primary standard as the primary calibrator or primary reference material. Secondary standard in turn is used for the purpose of calibration of control material in smaller lab for analysis of unknown concentration of a substance.
What is the difference between primary and secondary reference standards? ›
Primary reference standards are obtained from EP, USP, BP, JP, and FP. Also, they are quite expensive. While secondary reference standards are substances which are prepared by comparison with a primary reference substance.
What is an example of a primary standard? ›
A primary standard is a reagent that is extremely pure, stable, has no water of hydration and has a high molecular weight . Some primary standards are sodium carbonate, potassium hydrogen iodate, potassium dichromate, oxalic acid etc.
What are the primary and secondary standards of measurement? ›
Primary Standard Quantity : It has only value and it is fixed. Secondary Standard Quantity : Its value is less accurate than primary standard quantity and it is obtained by comparing with a primary standard.
What is a secondary standard provide an example? ›
One of the primary standards used in chemistry is potassium hydrogen phthalate or KHP. A secondary standard, on the other hand, is a chemical that has been standardized against a primary standard. In the example that we discussed, the NaOH was standardized against a primary standard.
What are primary or secondary standards? ›
Primary standards are highly purified substances with precisely known properties used for accurate titrations and calibration. They are stable, non-hygroscopic, and easily weighed. Secondary standards are less pure solutions or substances employed for routine analytical procedures like instrument calibration.
What is the difference between primary standard and secondary standard PDF? ›
There are two types of standard.
A primary standard should be >99.8% pure. Secondary standard is more reactive, on comparing primary and secondary standards. Secondary standard or an instrument can be calibrated using primary standard. By titration using primary standard, secondary standard can be prepared.
What are the characteristics of a primary and secondary standard? ›
In chemistry, a primary standard is a highly pure compound used to accurately determine the concentration of another substance. A secondary standard cannot be weighed accurately, but its concentration can be determined. The NaOH solution used in the experiment was a secondary standard that needed to be standardized.
What are the primary standard and secondary standard in calibration? ›
Primary standard: direct measurement of physical volume of an enclosed space. Secondary standards: cannot be calibrated by measurement of internal volume. Calibration against a primary standard or a calibrated secondary standard is required.
What are the 2 main standards of measurement used today? ›
most commonly used units define quantities of length (or distance), area, volume, and horizontal or vertical angles. The two systems used for specifying units of measure are the English and metric systems.
A primary standard must have, at least, the following characteristics: high state of purity, stability in air and in solution, solubility, reasonably high formula mass.
Why is NaOH not a primary standard? ›
It is not suitable for the primary standards because they absorb the moisture from the atmosphere. It also absorbs carbon dioxide from the atmosphere. Hence, NaOH is not a primary standard because it has no quality of primary standard.
What is primary and secondary referencing? ›
In a primary source, an author shares his or her original research—whether it be case study findings, experiment results, interview materials, or clinical observations. However, in a secondary source, an author focuses on presenting other scholars' research, such as in a literature review.
What is primary standard and secondary standard calibration? ›
Primary standards are used as primary calibrators or primary reference materials. Additionally, secondary standards are used in smaller labs for the calibration of control materials, which is used for analyzing unknown concentrations of substances.
What is a primary standard reference material? ›
A primary standard reference material is an ultra high purity grade compound used in analysis involving assay, identification or purity tests.
What is the primary purpose of a reference standard? ›
A reference standard, or reference material, is prepared for use as the standard in an assay, identification, or purity test. It should have a quality appropriate to its use. It is often characterized and evaluated for its intended purpose by additional procedures other than those used in routine testing [11].
