• Mirco Written by Mirco Rossetti, Application Specialist | 20 October 2022

How much are you paying for ultra-pure analytical grade acids?

Make your own HF, HNO3 and HCl acids

Purify your own HF, HNO3 and HCl acids with the Milestone subCLEAN system is the smarter choice for your lab.
Low cost, low grade acid is automatically loaded into the distillation container where it is gently heated below its boiling temperature using a sub-boiling technique.
High purity acid vapours rapidly condense into a collection bottle by forced air cooling meaning that no chiller is required either.
In contrast to acid purification through conventional distillation, where strong boiling action generating aerosolized particles results in contamination of the original liquid with the distillate, acid distillation system using sub-boiling technology prevents the formation of spray or droplets and yields to a very high pure acid.
  1. Reduce your sample prep blanks
  2. ‘On-demand’ acid purification
  3. Up to 90% cost saving of ultrapure acids
  4. Re-purification of contaminated acids
  5. ‘On-demand’ acid purification

Questions and Answers

Q1: Which acids can I distill with this system?
The duoPUR can be used to purify all common laboratory acids, mainly HNO3 and HCl. HF purification can be done in the subCLEAN, which use a PTFE boiler. The use of H2SO4 and H3PO4 is not recommended due to the high boiling point.
Q2: I currently purchase Baker ULTREX® II or SEASTAR Optima Grade acids. Can I distill my own acids with the duoPUR and get them as clean as these?
Yes. Acids produced with the duoPUR are as clean as, or cleaner than, commercially available double-distilled acids.
Q3: How long will it take to distill my acid, and how much can I distill at one time?
The time and power settings for the subPUR, duoPUR, subCLEAN system determine the distillation rate and the purity of the distillate. Higher power results in faster distillation rates, but the purity may suff¬er. Simple method development will determine the proper program time for your required acid purity.
Q4: If I want to double-distill my acid, should I run it twice in the same still, or sequentially using one still and then the second?
The easiest method sequentially in one still then in the second. However, if the duoPUR is used to purify more than one acid type, using the same still twice is better option, because it will limit the draining and rinsing time. Also, the impurities leached from the quartz are not the same from acid to acid. This might result in elevated concentrations for some elements or recontamination of the quartz. Repeated distillations using the same acid results in a “cleaning effect” on the quartz, effectively making it cleaner each time the system is run.
Q5: Can the system become contaminated?
The duoPUR and the subCLEAN are closed systems that cannot become contaminated during proper, routine use. It is possible, however, for an operator to introduce contaminants into the system. The most common source of contamination is the collection bottle. Milestone recommends the collection bottle only be used to collect the purified acid, and not for routine dispensing.
Q6: How often does the system have to be drained?
The system should be drained every six months, or when the quality of acid begins to degrade.
Q7: How do I drain (get rid of) the waste acid?
The dedicated pump allows to drain and fill the system automatically, further reducing the user exposure to the acid.
Q8: Can the duoPUR and subCLEAN be run unattended, or does someone need to be present while it runs?
The microprocessor control and the safety interlocks allow the system to run unattended.
Q9: Why would I want to make my own high-purity acids when I can just buy them?
Making your own acids is much less expensive than purchasing them from an outside supplier. Depending on your individual rate of use, it may take just a few months for a sub-boiling distillation unit to pay for itself. See our duoPUR savings calculator to analyze your individual situation. Also, you will have the added advantages of being able to re-purify your contaminated acids, rather than downgrading them and allow for acid purification on-demand.
Q10: Is there any data available of heavy metal analysis using HF and without HF for cosmetic?
The repeatability studies during the development of the ISO 21392 did never include HF. So, no data are available.
Suggestion: some data may be found in scientific publication

Guidelines for acid purification systems

Clean chemistry tools for atomic spectroscopy