Letter 25036

Dispensing Deionized Water  

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My work involves dispensing DNA on glass slides. As part of our process we perform several manual rinse steps with DI water. The DNA dispensed is basically looking for it's partner to complete it. We can not introduce any contaminates that can bind with the DNA, epecially bacteria. I would like to inexpensively automate the process. We found out the hard way that stainless steel will rust, rust contaminates the DNA. I am concerned about contaminates that could occur with deionized corrosion. I need to know specifically what materials are corroded by DI water, so I can get an idea of what material to use for the mechanical parts that will spray the DI water. The part would process DI water 24 hours 7 days a week.

Miranda Goff
bio science - Mesa, Arizona

What you should really be looking at is what grade of DI water you need. This will then help determine the materials used. Very pure DI water will dissolve eventually anything. I have found that the best material to use is teflon coated 316L stainless steel. (sometimes the 304 rusts)

Mike Wells
plating stuff - Jamestown, New York

Teflon would be a good material to look at for any parts teflon is available in. There are many different Stainless steel alloys. carpentor 20 is very corrosion resistant. Do you know which alloy you have tried. The more common 304 is a little less corrosin resistant.

Thanks,

Tim Hone
Water Treatment - Farmington Hills, MI

You may want to use PFA 0r PVDF tubing and fittings if the application is really critical,but for most applications, polyethylene or polypropylene are adequate. In order to assure that the water is bacteria-free,however, there should be final filter with a pore size of .05 or .02 microns.

Lyle Kirman
water treatment systems - Cleveland, Ohio

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