Most of us working in laboratories use different chemicals but lack required clarity on their grades. Validated Methods specify the grade of reagents to be used. It is important to use specified grades otherwise errors can arise due to contamination from reagents themselves. On the other hand you can incur additional cost in analysis if you use a superior grade of reagent when your analysis does not have such high purity requirements.
Laboratory reagents are classified on the basis of purity and intended use.
Classification based on purity
Technical grade – suitable for non-critical tasks such as rinsing, dissolving, etc
Synthesis grade – for organic synthesis and preparative tasks
Lab grade – covers most solvents used in common laboratory applications
A R grade – used for high precision work. Trace impurities are restricted to lowest possible limits for high precision. Such reagents used mainly for analytical applications, research and quality control . If such reagent meets the ACS specifications it will be denoted as AR (ACS)
ACS grade – ACS stands for American Chemical Society. Such grades are useful for high quality work
General reagent (GR) – reagent that meets or exceed AR grade specifications
Extra pure grade – suitable for laboratory accreditations and also work requiring compliance with pharmacopoeial standard requirements
Classification based on applications
Electronic grade – these have very stringent limits for metallic impurities as required for use in electronic component industry as such as below ppt or ppb levels
HPLC grade – solvents meet strict UV absorbance specifications and are filtered for removal of sub-micron suspended solids. Omnisolv HPLC grade products meeting ACS requirements suitable for use in HPLC applications
Spectroscopy grade – includes solvents of high purity, low residue on boiling and having absorption blank in wavelength region of interest.HPLC/spectroscopy grade for common use in HPLC and spectroscopic applications. Spectroscopy grade salts alkali metal salts having transparency in IR region such as KBr, NaCl, CsI,etc
Suprapur (E – Merck) – high purity grade acids having metallic impurities in ppb range
Environmental grade (Anachemia) – high purity acids refined through sub- boiling distillation
Environmental grade plus (Anachemia) – produced by additional distillation of environmental grade acids
Pesticide residue analysis applications
HR Omni grade solvents (EMD) – have GC impurities below ppt/ppb levels as tested by ECD detection
Nano grade – meet ACS grade specifications used for extraction and pre-concentration applications
Residue grade solvents – solvents suitable for pesticide residue analysis
Choice of the right grade of reagent is essential for the application in hand and it is also important to use reagents from same source for high precision of results
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