How Not to Break Your Cryogenic Cuvettes

Greetings of the day!

To crush your cuvettes, to see them driven before you and to hear the lamentations of your lab managers!

To crush your cuvettes, to see them driven before you and to hear the lamentations of your lab managers!

Today we're going to focus on a topic close to our hearts here at FireflySci, mainly that of NOT breaking your cryogenic cuvettes.

Most cuvettes are not made for cryo applications and will shatter in miraculous fashion when you expose them to temperatures in the low kelvins. A surefire way to accomplish this is to rapidly drop the temperature or bring it up and you will see something approaching the cell to the right. FireflySci, however, has a line of cryogenic cuvettes specifically made to survive these conditions better than most. 

Closeup on our cryogenically fused 64fluv10 cuvette

Closeup on our cryogenically fused 64fluv10 cuvette

To begin with, our cryo cuvettes are made from our UV Quartz (Suprasil 3001) material, which can endure thermal shock better than most. We also perform custom fusing with specific emphasis on making sure our edges and corners are protected as they are the most common areas where cracking starts. 

The cause of thermal shock is when an abrupt change in temperature causes the cuvette to expand or contract at differing rates in different areas. This will cause a strain that can manifest as a small hairline crack and eventually a full-on shatter. A good way to visualize this is what happens when you place an ice cube into a warm glass of water. There is a distinct noise as the cracks appear immediately all over the cube.

The way to avoid this is not particularly complicated but it is important. Here are a couple of tips to avoid issues:

1. Slow (I mean SLOOOWWWW) cool-down and heat-up.

Don't be like T1000. Cool and warm up those cuvettes very, very slowly!

Don't be like T1000. Cool and warm up those cuvettes very, very slowly!

This is the one single way to avoid cracks with our cryogenic cuvettes. If you are going to be dropping your Cryostat down to 77K there is no way to overemphasize the importance of slowly bringing the temperature down and then bringing it back up. AT LEAST an hour for cool-down and AT LEAST an hour for warm-up should be used. 

If you think you haven't given it enough time to cool off and heat up disregard this feeling and let it cool even longer!

2. Don't add a sample of a different temperature into the cuvette.

If you have a very cold cryo cuvette that has not fully warmed up it would be ill-advised to drop a room temperature sample into the chamber. Think of the ice cube example from above.

3. Add fluid directly down the center of the cuvette via funnel or nozzle.

One surefire way to create a temperature gradient that can shatter a cuvette is to pour a warmer sample down the side of a wall. What this would do is create a large difference in temperature on the walls increasing your risk of breakage. It is often a better idea to insert your sample beforehand to avoid this issue.

4. Avoid handling right away

If you have just taken the cuvette out of your Cryostat make sure not to handle it right away. The reason for this is that your cuvette might still be very cold and the heat from your hand might cause an abrupt fluctuation in temperature leading to fissures and shattering. Try to wait at least 30-45 minutes before handling the cuvette.

Here's to your shatter-less success!

The FireflySci Team

Material Breakdown for All FireflySci Cuvettes

Material Breakdown for All FireflySci Cuvettes

Hi again, everyone! We often get customers with specific questions about the material of our cuvettes such as thermal expansion rate, chemical compatibility,etc. As such, we've decided to compile a complete list of the materials that we use along with a complete detailing of their properties.

Optical Glass

Source: Knight Optical- http://www.knightoptical.co.uk

For what we call Optical Glass we use Schott B270, a versatile material that allows customers to use our cuvettes through the VIS and NIR range (340-2,500nm).  B270 Ultra-White or Superwite, as it's called, is a crown glass that is produced through melting high purity raw materials. The end result is highly transmittant, flat glass that offers remarkable chemical stability. 

Our most cost-effective material, B270 enables our customers a large amount of flexibility while working on a budget. Some of the other features include low acoustic attenuation of surface acoustic waves and the ability to fuse additional glass structures onto our Optical Glass cuvettes.

Our Optical Glass, Schott B270 cuvettes are easily identifiable through the "G", which we engrave on the upper right corner.

For a full rundown of the optical properties, including refractive indices, coefficient of thermal expansion and density, you can read further here: http://www.us.schott.com/advanced_optics/english/syn/advanced_optics/products/optical-materials/thin-glass/ultra-white-glass-b-270-i/index.html

Pyrex Glass

Source: Esco Optics- http://www.escooptics.com

What we call "Pyrex" is actually Corning 7740. Customers often favor using Pyrex/Borofloat over Optical Glass due to its superior transmission, extreme flatness and weak fluorescence. On top of this, low thermal expansion enables the cells to be used at temperatures in excess of 450ºC for long periods at a time, giving it superior durability over B270. Add to this an expanded chemical resistance and it's a no-brainer for many customers, especially those who have us do custom work. 

Transmission-wise, the Corning 7740 is a tad superior to Optical Glass with over 80% transmission between the wavelength range of 320-2,500nm.

Most of the time, however, customers go with Pyrex simply because it is the easiest material to fuse additional structures onto. Some typical add-ons include vacuum valves, graded seals and adapters. All BF33 cuvettes have a "P" designation on the upper-right corner.

To read more about the optical properties, go straight to the source here: http://www.quartz.com/pxprop.pdf

UV Quartz

UV Quartz (a.k.a. Suprasil 3001) transmission range of 190-2,500nm

What we refer to as UV Quartz is actually Suprasil 3001. Suprasil 3001 is an extremely high-purity, synthetic fused silica that combines a low thermal expansion coefficient and high chemical resistance to make it a far more durable choice than any of our glass materials. 

 With an operational wavelength range of 190-2,500nm, this is the go-to for work in the UV range but can be used all throughout the VIS and NIR as well. Suprasil is our most versatile material and can withstand some serious punishment and will only soften at over 1730ºC while the maximum recommended operational temperature is 1200ºC. Furthermore, you can even drop these cuvettes into the low Kelvins and this material will hold up in cryogenic applications as well. We even feature an entire line of cryogenic cuvettes made from Suprasil 3001 for both absorption and fluorescence.

Every Suprasil 3001/UV quartz cuvette is marked with "UV" on the upper-right corner.

To read more about the optical properties, check the following source: https://www.heraeus.com/media/media/hca/doc_hca/products_and_solutions_8/optics/Data_and_Properties_Optics_fused_silica_EN.pdf

IR Quartz

IR Quartz (A.K.A.Suprasil 300) Transmission range of 220-3,500nm

When it comes to dipping deeper into the NIR and even into the mid-IR range, Suprasil 300 is the material for the job. Suprasil 300 is manufactured by fusing quartz crystal in an electric vacuum furnace. The end product is a low-bubble, durable fused silica that enables optical transmission from 220-3,500nm. 

Much more cost-effective than Calcium Fluoride or ZnS for Mid-IR work, Suprasil 300 IR Quartz is used mostly in high-grade spectrophotometers such as Cary or Agilent machines.

Every Suprasil 300 IR quartz cuvette is marked with "IR" on the upper-right corner.

To read more about the optical properties, check the following source: https://www.heraeus.com/media/media/hqs/doc_hqs/products_and_solutions_8/optics/Data_and_Properties_Optics_fused_silica_EN.pdf

Sapphire

Sapphire transmission range of 250-5,000nm

Sapphire is our most rarely used and most expensive material but it sure does pack a punch. With an enormous transmission range of 250-5,000nm and extreme resistance to scratching, heat, electrity and chemical corrosion this is far and away our most durable material. 

Most people won't need something like sapphire but occasionally we have customers who want to build a flow cell or optical windows that can withstand extreme conditions or dip very far into the IR range. 

This is a cutting edge technology and as the demand for sapphire optics increases, FireflySci is, in turn, increasing their technical capabilities.

Learn more about sapphire here on Schott's website: http://www.schott.com/advanced_optics/english/download/schott-sapphire-may-2013-eng.pdf