The power of the analytical blank.

Acid Purification Systems

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    Substantial ROI

    Up to 90% cost savings of ultra-pure acids by purifying low-cost reagent grade acids.

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    On-demand acid purification

    Works with a variety of acids; also, suitable for purification of organic solvents.

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    Designed for your needs

    Single, double or triple distill reagents (ppb, ppt)

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    Effective and efficient

    Re-purify contaminated acids with no waste.


Learn more about the factors that impact the analytical blank, digestion techniques, and Milestone’s Clean Chemistry products designed to help you maximize your ICP-OES and ICP-MS data.

Download Think Blank Primer

“In the preparation of high purity reagents, there is only one significant and practical choice for the method of purification: sub-boiling distillation.” – US EPA SW-846, Chapter 3, Update IVB.

Reagent contamination increases the background concentration of analytes present in a sample. Because of this, laboratories purchase expensive high-purity acids for trace metal (element) analyses. With small samples sizes, it is critical to keep blank levels low for good reproducibility. Milestone’s duoPUR and subCLEAN, sub-boiling distillation systems allow laboratories to make their own high purity acids at dramatically reduced costs.

Sub-Boiling Technology

The chemical reagents used during the analysis are an important source of the analytical blank. Sub-boiling distillation has been demonstrated to be the best method of acid purification. It uses contactless infrared lamps to vaporize the surface liquid at a temperature typically 20 °C below the boiling point.

With conventional distillation, the boiling of acid generates aerosolized particles, resulting in contamination of the distillate. In contrast to this, gentle surface evaporation during sub-boiling distillation prevents the formation of spray or droplets, yielding high purity acids.

duoPUR – Quartz Sub-Boiling System

The duoPUR consists of two quartz distillation units. Each unit contains two infrared heating elements, a water-cooled condenser, a high-purity PFA collection bottle, and a fully automatic acid loading/discharge system. The vaporized liquid is collected on the inclined water-cooled condenser and drips into the collection bottle. The distillation process is microprocessor controlled, allowing the user to set the distillation time and power level by using a compact control terminal with easy-to-read, bright, full-color, touch-screen display.

Distillation rates range from 50 to 400 mL per hour, depending on the power setting and cooling temperature.


The Milestone subCLEAN is a compact and easy-to-use sub-boiling system, where all parts in contact with acids are made of high-purity fluoropolymers. The subCLEAN is therefore suitable for the purification of HF, as well as for HNO3 and HCl.

Furthermore, it does not require cooling water or a chiller, as acid vapors rapidly condense into a collection bottle by forced air cooling.

The duoPUR and subCLEAN offer an alternative to the purchase of expensive high purity acids for trace elemental analysis.

  • Same technology used in the commercial production of acids for ultra-trace metals analysis
  • 90% cost saving of ultra-pure acids by purifying low-cost reagent grade acids
  • Purify the quantity you need, when you need it
  • Up to 400 mL per hour (duoPUR) and 80 mL per hour (subCLEAN)
Comparison of metal contamination (μg/L) in nitric acid purified by sub-boiling and traditional distillation

How much will you save each month?

Example: If a lab processes 200 samples per month using 30 mL of ultra-pure nitric acid (J.T. Baker Ultrex II) per sample, it will use 6 L of ultra-pure acid at a cost of $6,120.00 per month, or $1,020.00 per liter per month. Six liters of reagent-grade acid (Sigma-Aldrich) would only cost approx. $264.00 per month, or $44.00 per liter per month. By distilling this lower-grade acid, $5,856.00 would be saved every month, which translates to the duoPUR paying for itself in about 5 months.

*Sample pricing based on J.T. Baker Chemical and Sigma Aldrich – 2020

Additional Clean Chemistry Resources


Clean Chemistry Brochure DOWNLOAD


Get answers about our Clean Chemistry Products. DOWNLOAD


Learn How Acid Purification allows labs to purify low-cost reagent grade acids. DOWNLOAD

User Profile

DuoPUR Lowers Cost and Increases ROI for Water Testing Lab. DOWNLOAD

ROI Worksheet

How Much Will Sub-Boiling Distillation Save You Each Month? DOWNLOAD

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