Written and maintained by CASRAI Editorial Board
Last updated
HPLC-grade water is bottled water sold under a supplier’s own specification, not a single published standard. The label usually points to a short list of limits (residue after evaporation, UV absorbance and a filtration step), and those limits differ from one supplier to the next. Read the specification table for the exact bottle in use.
Short answer
“HPLC grade” on a water bottle is a supplier specification. Two product pages, one from Lab Alley and one for J.T. Baker 4218-03, both carry the label, yet they list different residue limits, different filter sizes and measure UV absorbance in different ways. Neither page defines the term by reference to a pharmacopoeia or ASTM method, so the useful question is not “is it HPLC grade?” but “which limits does this bottle’s sheet actually state?”
Definition and scope
In liquid chromatography, water is usually a large share of the mobile phase and is used for rinsing and sample preparation, so impurities in it can show up as baseline noise, ghost peaks or particulate that reaches the column. Bottled HPLC-grade water is sold as a ready-to-use alternative to water produced in house by a purification system. The grades that are defined in standards (Type I, II and III reagent water) are covered in the laboratory water grades guide; this page only covers what the HPLC-grade label tells you on a purchased bottle.
How the label is used in practice
Bottled HPLC-grade water is used where a lab has no purification system, where a method calls for a labelled solvent, or as a reference blank. For the chromatography itself, see the HPLC guide. Because the term has no single definition, each supplier publishes its own table. The sections below compare two of them directly.
Two supplier specifications compared
The table lists only values printed on the two product pages, checked on 2026-10-29. A blank means the page does not state that item.
| Item | Lab Alley “Water, HPLC Grade” | J.T. Baker 4218-03 “Water, HPLC Grade” |
|---|---|---|
| Residue after evaporation | Max 1 ppm | <= 2.0 ppm |
| Assay | Min 99.5% | Not stated on the page |
| Substances reducing permanganate | To pass test | Not stated on the page |
| UV absorbance | Limits at fixed wavelengths: 0.01 max. at 190, 200 and 210 nm; 0.005 max at 250 nm and at 300-400 nm (no unit printed) | Gradient-elution test: largest peak at 254 nm, <= 0.0010 au (a 205 nm gradient-elution entry is also listed, with no limit shown) |
| Filtration | 0.22 micron filter | 0.2 micron filter; the listing also shows a filtration test that passes |
| Total organic carbon / conductivity | Page quotes ASTM Type I values (<50 ppb TOC, <0.056 µS/cm) in its description | No TOC or conductivity entry on the page |
Three differences matter. First, the residue limit is not the same (1 ppm versus 2.0 ppm). Second, the filter size is stated as 0.22 versus 0.2 micron. Third, and most important, the two UV entries are not interchangeable: one is a set of absorbance limits across wavelengths, the other is the largest peak seen when the water is run as a gradient elution at a stated wavelength. The Baker listing also includes a fluorescence trace-impurity test measured as quinine base, which the Lab Alley table does not.
Checklist: what to read on a specification sheet
This is a reading checklist built from the two tables above, not purchasing advice.
- Residue after evaporation. Is a limit stated, and in what unit?
- How UV is expressed. Fixed-wavelength absorbance limits and a gradient-elution peak test describe different measurements. Check the wavelengths against the detector wavelength used in your method.
- Filter size. The two pages state 0.22 and 0.2 micron; check which is printed.
- TOC and conductivity. Present on one page only (as a quoted ASTM Type I figure), absent on the other. If a method needs them, confirm they are stated for the product itself.
- Units and test conditions. A limit with no unit or method (as with the UV values on one page) is harder to compare.
- Storage. The Lab Alley page gives no temperature and refers readers to the storage section of the Safety Data Sheet.
HPLC grade versus in-house Type I water
Type I reagent water is defined by standards, with conductivity and TOC limits; the Lab Alley page quotes the ASTM Type I figures of under 50 ppb TOC and under 0.056 µS/cm. A purification system produces that water on site and displays its resistivity or conductivity as it runs. The guide on laboratory water purification systems and the purification system comparison cover that route, and the maintenance guide covers keeping such a system’s output consistent. Bottled HPLC-grade water and Type I water are not the same thing by definition: one is a supplier’s list of limits, the other is a standard’s.
Common misunderstandings
“HPLC grade means a defined standard.”
Neither of the two pages cites a pharmacopoeial or ASTM definition of “HPLC grade water”. The label is a supplier’s, and its limits are whatever that supplier prints.
“All HPLC-grade bottles have the same limits.”
The comparison above shows different residue limits, different filter sizes and different UV test designs under the same label.
“Filtered means free of everything.”
The pages state a 0.22 or 0.2 micron filtration step to remove particulate matter. Filtration is a particle control; it is listed separately from the residue and UV limits, which address dissolved impurities.
“The water stays at specification once opened.”
The two pages give no shelf-life or opened-bottle claim, and the Lab Alley page points to the Safety Data Sheet for storage. Treat the table as describing the product as packed.
Where it matters for labs and supply decisions
For method documentation, record the supplier, product code and the specification entries relied on, since “HPLC grade” alone does not identify a set of limits. System upkeep that affects baseline, such as the items in the HPLC preventive maintenance schedule, is a separate issue from water quality, and vial and septa compatibility is covered in the vials and septa guide.
FAQ
What is HPLC-grade water?
Water sold under a supplier’s own “HPLC grade” specification, typically listing residue after evaporation, UV absorbance and filtration limits. The two supplier pages cited here do not tie it to a pharmacopoeial or ASTM definition.
Is HPLC-grade water the same as Type I water?
No. Type I is a standards-defined reagent water grade; HPLC grade is a supplier label. One supplier page quotes Type I values (<50 ppb TOC, <0.056 µS/cm) alongside its HPLC-grade table, while another lists no TOC or conductivity entry.
What do the UV absorbance entries mean?
They limit how much a water sample absorbs UV light, which matters for UV detection. One page lists absorbance limits at fixed wavelengths from 190 to 400 nm; the other lists a gradient-elution test at 254 nm with a limit of 0.0010 au.
Is the water filtered?
Both pages state filtration, 0.22 micron on one and 0.2 micron on the other.
Sources
- Lab Alley, “Water, HPLC Grade” product page, https://www.laballey.com/water-hplc-grade (checked 2026-10-29).
- J.T. Baker 4218-03 “Water, HPLC Grade” specification listing, Capitol Scientific, https://www.capitolscientific.com/JT-Baker-4218-03-4L-Water-HPLC-Grade (checked 2026-10-29).
