Type 1 Water Parameters

Type 1 Ultrapure Water Contaminant Removal

This table outlines the contaminants that must be removed to achieve Type 1 ultrapure water quality (HPLC, LC-MS, ICP-MS, molecular biology, cell culture), including the target parameter, filtration or purification media, method, and the logic for removal.

ContaminantTypical Type 1 Spec / RequirementFiltration / Purification MediaMethodLogic for Removal
Particulates< 1 µm (often 0.2 µm final), USP <788> compliantDepth filters, membrane filters (PES, PTFE, nylon)MicrofiltrationPrevents blockages in HPLC columns, avoids scattering in detectors, protects downstream equipment.
Bacteria< 1 CFU/100 mL (ideally non detectable)0.2 µm sterilizing-grade membranes, UV (254 nm)Microfiltration + UV killPrevents biofilm, endotoxin formation, and sample contamination.
Endotoxins< 0.25 EU/mL (cell culture grade)Positively charged membranes (nylon-66, PES)Adsorptive filtrationNegatively charged endotoxins bind to cationic surface; essential for cell culture to prevent immune reactions.
RNase< detection limit (molecular biology grade)Ultrafiltration (5–10 kDa MWCO), cationic membranesSize exclusion + electrostatic adsorptionEnzymes too large to pass UF pores; bound by positive charges to prevent RNA degradation.
DNase< detection limit (molecular biology grade)Ultrafiltration (5–10 kDa MWCO), cationic membranesSize exclusion + electrostatic adsorptionSame principle as RNase; protects DNA integrity in PCR/sequencing.
Ions (cations/anions)Resistivity 18.2 MΩ·cm at 25 °CMixed-bed ion exchange resins (H⁺/OH⁻)Ion exchangeRemoves dissolved salts and charged species, critical for low background conductivity and accurate analysis.
Silica< 0.01 mg/L for ICP-MSStrong-base anion exchange resinIon exchangeSilica interferes in trace metals analysis and damages some equipment.
Total Organic Carbon (TOC)< 5 ppb (LC-MS grade)UV oxidation (185 nm) + activated carbon + C18 (optional)Oxidation + adsorptionUV converts organics to CO₂, which IX removes; carbon/C18 adsorb hydrophobic organics to prevent ghost peaks and noise.
Volatile Organics< detection for LC/GC applicationsActivated carbon, VOC-specific adsorbentsAdsorptionPrevents contamination in GC or headspace analysis.
Trace Metals< 0.01 ppb for ICP-MSChelating resins, ultrapure IX resinsIon exchange / chelationMetals cause false positives in ICP-MS and damage instruments.
Pyrogens< 0.25 EU/mLPositively charged UF membranesAdsorptive ultrafiltrationPyrogens cause fever/inflammation in biological systems; removal critical for in vivo/in vitro work.
ColloidsNon detectableUltrafiltration (10–50 nm)Size exclusionPrevents baseline drift and fouling of LC columns, optical detectors.

How tight is too tight?

A common problem labs have is that the filter housing (bowl) gets tightened too much when the Ion-Ex or 1 Micron filters are changed and the next time they need to be replaced it seems like it is impossible to loosen it.

When doing up the bowl make sure the O-ring is in place and has not fallen out, without the O-ring the filter housing can seize as there is little give in the head and it plastic on plastic.

Bowls should only be done up by hand. The seal is provided by the O-ring, so it should be replaced if it does not seal when don up hand tight. The black spanner is intended for for loosening the housings.

IMPORTANT: If the bowl is over tightened they can crack as the styrene material it is made from can be quite brittle.