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How it was discovered that SWL™ is the world's first 100% contamination free device

The failed experiment: A scientist testing SWL™ in a lab reported a peculiar observation. He was evaluating SWL™ salt removal efficiency against a well-established fabricated dialysis device, in which membrane is fitted in a 'casette like' frame. Both SWL™ and the dialysis cassette were run in parallel, using a colored dye solution. The dye in case of SWL™ retained its original color, while that in the dialysis cassette underwent a drastic change! Thinking a mistake had been made, the scientist repeated the experiment. Again the dye changed color in the cassette device, but not in SWL™. The experiment was repeated not once, but 3-4 times and every time the same thing happened.

The matter was discussed with the inventor, who observed that while SWL™ was 'colorless' with no colored plastic part dipping in solution, the frame of the 'dialysis cassette' was bright orange. Was it possible that in solution, the 'orange color' was leaching out from the frame, maybe in nano or micro quantities? And maybe affecting the dye?

The invisible 'impurity' in water: The concept was tested by placing the cassette frame in distilled water for a few hours and then subjecting the water to a wavelength scan, using a highly sensitive spectrophotometer. The results were surprising! Though the water appeared colorless and to naked eye it appeared nothing had leached out from the frame, wavelength scan revealed that at particular wavelengths, the water was showing very high absorption. Some unknown impurity, most likely the coloring compound using in imparting color to the frame, was leaching out and contaminating the surrounding solution. Probably it was this compound that was causing the dye to change color.

The fundamental problem of 'accessory contamination': A look at other devices used in dialysis revealed that a 'fundamental problem' had been identified. All the devices available till date are a 'natural source' of contamination.

Dialysis tubingDialysis clampsDialysis cassettesOther fabricated devices


  • Dialysis tubing: tied with threads. Threads contain gums, bleaching agents etc. which are a natural source of contamination. Since lower end of the 'dialysis sac' tied with threads dips into solution, contamination cannot be avoided.
  • Dialysis clamps: made of colored plastic and dip into solution.
  • Dialysis cassettes: these must be fully immersed in the solution to 'operate' and dipping of the colored frame into water cannot be avoided. Also, these cassettes require a 'float' into which they are fitted. While researchers will change cassettes for new experiments, float invariably is reused- it appears 'not to be a part of experiment'. Unfortunately, it becomes a 'source of impurities' from prior experiments and keeps on contaminating subsequent solutions. Depending upon criticality of application, the experiments may or may not be affected.
  • Other fabricated devices: having some accessory in form of plastic support which is usually colored.

By virtue of design, these accessories dip into solution and are very likely to contaminate the solution with impurities in form of colorants added to the plastics. Dialysis tubing clamps are reused again and again and since the leaching out of color is too small to be visible to the naked eye, a researcher would not know if a problem is occurring e.g. loss of activity of an enzyme during purification may occur, but nobody would realize that the 'colorant' leaching out from the clamp caused it!

SWL™ is the only commercially available device in which only the membrane and NO OTHER PART OR ACCESSORY is in contact with the outside solution. All other parts viz. supporting ring, graduated chamber and supporting plate remain above the solution. Thus, spoilage of experiments due to accessory contamination is 100% eliminated.