What are the common grades for chemicals and reagents?

Grades of chemicals and reagents refer to their degree of purity. Before starting any experiment, researchers determine the grade of the chemical or reagent to ensure that the materials used in their assay have met all regulatory and compliance standards for their intended purpose. There are 7 common grades for chemicals and reagents listed from highest to lowest level of purity: 

1. ACS grade – ACS grade is an indication of very high purity. Chemicals graded ACS meet or exceed the purity standard set by the American Chemical Society (ACS). Chemicals graded ACS have a purity equal to or more than 95% and can be used for any lab or analytical applications that have stringent quality specifications. 
2. Reagent grade – Reagent grade is also an indication of very high purity that meets or exceeds standard set by American Chemical Society. Reagent grade chemicals can be used in all scientific assays where quality is critical. These chemicals are acceptable for medicinal, food, and drug use. 
3. USP grade – USP grade chemicals meet or exceed the requirements set by the United States Pharmacopeia (USP). Chemicals graded USP can be used for most laboratory purposes and are also acceptable for medicinal, food, and drug use. The only caveat is that prior to use, the USP being followed must always be reviewed to ensure that the grade is appropriate for that specific methodology. 
4. NF grade – NF grade chemicals meet or exceed standards set by the National Formulary (NF). Equivalent grades must be determined before use by reviewing the listings in the book of public pharmacopeial standards jointly published by the USP and the NF. NF grade chemicals are most commonly used for educational purposes and as an upper-level intermediate quality chemical.
5. Laboratory grade – Laboratory grade chemicals have a relatively high purity, although their exact levels of impurities are unknown. These chemicals are excellent for teaching and training purposes but may not be pure enough to be used in medicinal, food, and drug applications. They may be used in general laboratory work where there’s no requirement for an analytical reagent. 
6. Purified grade – Purified grade chemicals meet no official standard of purity. These chemicals may contain impurities that prevent them from being used for any type of medicinal, food, or drug applications. Purified grade chemicals, also called practical or commercial grade chemicals, are often supplied in bulk for commercial or industrial use, where they are generally used in qualitative testing or low grade applications.  
7. Technical grade – Technical grade chemicals have a lower level of purity than purified grade and are not suitable for medicinal, food, or drug use of any kind. These chemicals contain impurities and are often supplied in bulk for commercial or industrial use, where they are generally used in low grade applications or qualitative testing.