AR Grade (Analytical Reagent) chemicals

What AR grade means

AR, or Analytical Reagent, grade denotes chemicals of high purity whose specification lists maximum limits for named impurities, such as chloride, sulfate, heavy metals, iron and insoluble matter, as well as a minimum assay. The grade exists so that the reagent itself does not contribute measurable error to an analysis. The terms GR (Guaranteed Reagent) and pro analysi (p.a.) are used by some manufacturers for broadly equivalent grades.

AR is a trade grade rather than a single legal standard. Different manufacturers set their own AR specifications, often modelled on ACS Reagent Chemicals or ISO reagent standards, so it is worth comparing specific limits when switching supplier.

Typical specifications

Parameter	Example: sodium chloride AR
Assay	≥ 99.5 to 99.9%
Insoluble matter	≤ 0.005%
Sulfate (SO₄)	≤ 0.001 to 0.004%
Heavy metals (as Pb)	≤ 5 ppm
Iron (Fe)	≤ 2 ppm
pH of 5% solution	Within a stated range

Values in the table are typical of the grade. The limits that apply to a given product are those stated on its specification and lot Certificate of Analysis.

Where it is used

• Preparation of volumetric solutions and standards for titrimetry
• Gravimetric and instrumental quantitative analysis
• Quality control testing in pharmaceutical, food, water and metallurgical laboratories
• Research where impurities could interfere with results

How it differs from neighbouring grades

LR grade has a lower assay and fewer or wider impurity limits, which makes it economical for synthesis, cleaning and teaching but unsuitable for quantitative work. ACS grade is a specific, published standard: a product labelled ACS must meet the current ACS Reagent Chemicals monograph, whereas AR limits are set by each manufacturer. HPLC and other application grades add tests specific to an instrument technique, such as UV absorbance or residue, that AR does not include. For primary standards in titrimetry, a certified or primary-standard grade may be required in addition.

Choosing AR grade

Use AR when the reagent's impurities could reach your result, and check that the limits on the COA cover the impurities that matter for your method.

Ordering AR grade reagents

When you request a quotation for an AR product, we state the assay and impurity limits that the offered lot meets. If your method depends on a particular impurity, such as iron in a colorimetric test or chloride in a conductivity measurement, mention it and we will confirm the relevant limit before you order.