Whether it’s in a chemical’s title or its description, there is usually a note about a reagent’s grade. If you only use molecular biology grade, will using HPLC grade be a problem? What do these reagent grades even mean? How much do these grades really matter?
These are great questions when it comes to buying reagents, and it’s a subject that can be a little tedious to research.
So, I approached this topic in two primary ways to simplify what these different chemical grades really mean and why it matters. First, I’ll go into the fundamentals about how these grades originated and what their purpose is for being differentiated from one another. Then I’ll go into some of the more common grades and what they mean. By the end of the article, you’ll have a much better idea about how to judge chemicals and what you can get away with substituting when needed.
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Part I: Chemical Grade Fundamentals
The General Purpose of Different Chemical Grades:
To answer how much these chemical grades really matter, we need to look at why these different reagent grades were put into place – or what their general purpose is. Simply put, reagent grades relate to certain specifications and whether a chemical meets those specifications.
Now, this idea goes deeper than simply having grades represent a level of purity. While that is true, certain chemical grades are also going to be tailored to a specific procedure, application or market. For example, chemical grades for food and pharmaceutical chemicals may involve detecting impurities related to toxicity, metals and bioactive impurities.
To get a better understanding of what each grade is going to be concerned with, take a look at our companion printable guide. This guide details common chemical grades and offers explanations to give you a full understanding. Or scroll to Part 2 in this article for an overview.
What Determines the Specifications for Different Chemical Grades:
Chemicals have monographs which serve as a standard, providing information about a reagent’s appearance, solubility, molecular weight, safety and purity.
When it comes to purity, the monograph will have information about appropriate testing assays and the acceptable results defined by the publishing organization. According to the US Pharmacopoeia (USP.org), monographs are aimed to help control quality.
Chemical monographs can be found from a variety of standards organizations including the American Chemical Society (ACS) and the United States Pharmacopoeia (USP).
As an example of what a monograph looks like, the ACS’s demo monograph for Acetic Anhydride provides the chemical’s general description and specifications at the top of the page. Next, the page shows basic information about quality checks and its corresponding page in the ACS’s “Reagent Chemicals: Specifications and Procedures” book.
The takeaway is that material grades do matter because they originate from a standard that is defined by an organization in an effort to keep the manufacturing processes and chemical quality the same. These standards also ensure they fit within the needs of the corresponding applications or uses (food grade, HPLC grade, etc.); however, more information about specialty grades is included below in Part 2.
Substituting One Grade for Another:
A familiar scenario in a lab setting goes something like, “Oh no! I ran out of my molecular biology grade reagent. Can I get away with using ____ grade instead?” It’s a little scary to be in this situation because you worry about compromising the quality and results of your experiment. So here are some questions to ask yourself which will help you reach your conclusion about the answer.
- Is the version I have available considered to be a grade higher / higher quality? And does having a higher or lower grade matter?
- What do I know or what can I easily find out about the grade I was originally using and the grade I intend to use?
- Are the standards between the two different grades relatively similar? Where do they differ? And do the differences matter based on my current experiment?
- Will the results of this procedure and the reagents I’m presently using be published or am I performing a simple test of little consequence?
- What are the regulatory considerations when substituting?
Part 2: Differences in Chemical Grades
In an earlier topic, I mentioned our printable guide on the different reagent grades; this guide makes a great reference sheet; however, it would be good to go into some greater detail so that the subject is entirely understood. I’ve broken this section down so that you learn about primary chemical grades, get information about specialty grades and become aware of international grades.
Common Chemical Grades in Order of Purity (Highest to Lowest):
1. ACS Grade – Highest purity chemical grade, meeting or exceeding American Chemical Society standards.
2. Reagent Grade– A high purity grade, which is usually equal to the ACS grade. Reagent grade chemicals are generally suited for laboratory and analytical research.
3. USP Grade– This chemical grade meets or exceeds the requirements of the United States Pharmacopeia (USP).
4. NF– Chemical grade that meets or exceeds the requirements of the US National Formulary. However, since it was merged with the USP, it has become USP-NF.
5. Lab Grade– Chemical grade of high quality, but its exact impurities are unknown. It is, however, pure enough for education applications, but does not meet the purity requirements for food, or drug uses.
6. Purified Grade– A chemical grade that is also known as the practical grade. Chemicals under this grade are of good quality but do not meet any official standards. It is best suited for educational applications only, and is not pure enough for food and drug applications.
7. Technical Grade– The technical grade is considered a good quality chemical grade for educational purposes, and has a purity around 85-90%. But it is not pure enough for food and drug applications.
Understanding Specialty Grades and Branded Grades:
Specialty grades were established not only to provide standards, but were also developed to evaluate impurities that are more concerning to certain research applications. Most manufacturers recognize a variety of these specialty grades; however, certain brands and manufacturers have developed their own material grades specialized for certain laboratory applications or equipment.
Of course sorting through these specialty grades can be quite challenging. First, you’re probably interested in filtering for what is most commonly accepted (analytical grade, molecular biology grade, HPLC grade, etc.) and understanding those differences. Then if a specialty grade is unique to an individual reagent company or manufacturer, you will wonder how to interpret it. Fortunately, most companies who define their own standards also provide information sheets about what those standards involve.
With that in mind, let’s take a look at the different, common specialty grades, which are also presented in the printable guide.
1. Analytical Grade –high purity reagents that are best suited for analytical applications. They are ideal for providing consistent results.
2. Biotechnology Grade/Molecular Biology Grade–chemicals are equal to ultra-pure chemicals and are ideal for molecular biology applications. This grade is primarily focused on tests for enzymatic, nuclease and bacterial impurities.
3. DNA Grade–chemicals suited for molecular biology applications that primarily involve DNA and are tested for protease and DNase impurities.
4. Electrophoresis Grade– chemicals suited for electrophoresis.
5. High Purity Grade– high purity grade chemicals are of high quality where there are no standards published.
6. HPLC Grade–high purity chemicals that are best suited for HPLC and mass spectrometry.
7. Proteomics Grade– chemicals that follow the requirements for protein research. They are tested for and required to be (in applicable cases) nuclease, DNase and protease free.
8. Sequencing Grade–are designed to be used with automated capillary sequencing equipment.
9. Tissue Culture Grade–high purity reagents ideal for use in tissue culture applications.
10.Ultra-Pure Grade – high-purity materials where impurities must be very low – in the parts per trillion or parts per billion level. These materials are considered to have a purity level exceeding USP monographs.
A Note about International Standards and Grades (BP, EP, JP and USP Grade Explanations):
USP grade was mentioned earlier in this article as a grade that meets the standards of the US Pharmacopoeia. However, you may also have seen grades such as BP, EP or JP. BP grade chemicals conform to the standards presented in the British Pharmacopoeia. EP grade chemicals meet the standards specified by the European Pharmacopoeia. And JP Grade chemicals meet the specifications outlined in the Japanese Pharmacopoeia.
There you have it – everything you ever wanted or were curious about when it comes to material grades in the lab.
The primary takeaways are:
- Chemical Grades are important because they are not only determined by an expectation of quality but are also defined by the quality standards most applicable for specific uses.
- Some manufacturers establish their own specialty grades and defined standards, but oftentimes present information on how to interpret their meaning.
- Chemical Grades provide manufacturers with guidance about how to consistently produce vital laboratory reagents.
- By having a better understanding of what differentiates the chemical grades, you can know what, if any, appropriate substitutes you may use in special cases.
Keep this one bookmarked and share with a friend!
American Chemical Society Publications: Reagent Chemicals, 10th Edition. (n.d.). Retrieved June 14, 2016, from http://pubs.acs.org/reagents/dem2016o/
Darling, R. B. (n.d.). Chemical Storage and Labeling [PDF]. Seattle: University of Washington Electrical Engineering.
Guidelines for the Use of Non-Pharmaceutical Grade Compounds in Laboratory Animals [PDF]. (2013, April 10). Bethesda: Office of Animal Care and Use (OACU).
USP Standards: Monographs (Written Standards). (2011, December). Retrieved June 14, 2016, from http://www.usp.org/sites/default/files/usp_pdf/EN/regulator/monograph_backgrounder_dec_2011.pdf
U.S. Pharmacopeial Convention. (2016). Retrieved June 14, 2016, from http://www.usp.org/
What is the BP. (n.d.). Retrieved June 14, 2016, from https://www.pharmacopoeia.com/
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