How to Handle & Care for Spectrophotometer Calibration Standards

Liquid filter on the left and a Solid-State filter on the right

Liquid filter on the left and a Solid-State filter on the right

Do you have a set of spectrophotometer calibration standards in your lab?  If the answer is yes, the next few paragraphs will help save you tons of headaches and additional fees from mishandling your calibration standards. 

First, we’ll explain what can happen when standards are not handled properly.

  1. Incorrect readings – what is the point of having an NIST traceable standard that doesn’t work?  It doesn’t even make a good paperweight.
  2. Breakage – Standards that are cracked or chipped are not able to be repaired, so if you’ve not careful, you can throw that $1,000 right in the trash.
  3. Leakage (liquid standards only) – Liquid spectrophotometer calibration filters consist of many different chemicals.  Some of them are very hazardous, such as potassium dichromate, and you don’t want these things breaking and leaking all over your lab.

Solid-State Vs. Liquid Spectrophotometer Calibration Standards

The handling and cleaning procedure of solid-state filters and liquid filters is different.  In this guide, we will go over the care and maintenance of both types of calibration filters.  Let’s start with the solid-state filters.

How to Handle Solid-State Calibration Standards

Proper way to handle UV Calibration Filter

Proper way to handle UV Calibration Filter

 First off, always wear powder free gloves when handling solid-state calibration.  Fingerprints are the number one offender for incorrect readings.  Always pick up the standard by the sides.  A user should never touch the optical glass even while wearing gloves. 

Since solid-state filters are built in a metal housing, they have higher durability if they are accidentally dropped.  We’ve not saying they are ok to drop, dropping a solid filter can break the filter, but compared to a liquid filter they are more durable.

When inserting the filter into a spectrophotometer, be sure to insert the spectrophotometer calibration filter straight down into the cuvette holder.  Also when removing the filter make sure to pull straight up.  Any twisting motions can crack the neutral density glass rendering the filter unusable.

They may be shiny, but please no touching

They may be shiny, but please no touching

 

How to Clean Solid-State Calibration Filters

Pay no attention to the name on the can

Pay no attention to the name on the can

We do not recommend that you try to clean a solid calibration standard on your own.  We all love to use micro-fiber cloths to clean glasses, laptop screens, smartphones etc.  However, our results have shown that these types of cloths have cause smudges and scratches to the optical glass, so stay far away from them.  It’s the same deal with lens tissues, do not use them for cleaning a solid-state NIST calibration filter.

So what can I use for cleaning my filter?  The only safe way for a use to clean a solid calibration filter is with dust-free compressed air.  Simply lay the filter on a clean surface with the optical side facing up and give it a shot or two with the compressed air.  Note: only use dust-free air in a can.  Some compressor lines have dust in them and they can damage the optical surfaces.

How to Handle Liquid Calibration Standards

Proper way to pick up liquid standard

Proper way to pick up liquid standard

The handling procedure for liquid calibration standards is very similar to their solid-state brothers.  A big different between the two is that liquid standards are all housed in a UV quartz cuvette which means if you drop it,  then that’s the end of the filter.    Plus you’ll have to clean up the spill which could cause a hazardous problem.  So you have to be very careful when using liquid calibration standards.  Do not leave a filter on the lab table if it is not being used.  Please see the Storing section below.

Just to review, a liquid filter should be inserted and straight down into your spectrophotometer and should be pulled straight out for removal.

A liquid filter has to be picked up near the top of the filter and by the two frosted sides of the cuvette.  Some filters have a cap, in this case always hold the filter by the cap.  Powder free gloves must be worn when handling liquid filters.

How to Clean Liquid Calibration Standards

 Liquid filters are super easy to clean.  Since they are made with a UV quartz cuvette you can take a dust-free microfiber cloth and give the outside a good cleaning.  If there are tough stains on the outside, they can be removed by adding a drop of propan-2-ol to the lens tissue or micro-fiber cloth.  A dust-free compressed can of air will also do the trick for any type of dust removal.

Storing of Liquid & Solid-State Spectrophotometer Calibration Standards (Both liquid and solid-state standards)

  1. Always keep spectrophotometer calibration standards in their protective case when not in use.
  2. Store liquid calibration filters at room temperature.  These filters can freeze if stored in a place that is below freezing.
  3. Always use extreme caution when working with NIST calibration standards.

Conclusion

We all know and understand the importance of using calibration standards to validate our spectrophotometers.  By following the procedures outline above it will prolong the life of your calibration standards.  If you are using FireflySci’s solid-state filters and you follow the guidelines above, you’ll never need to send the filter in for re-calibration or cleaning.

If you have any questions please contact us.

Here’s to Your Success!

The FireflySci Team