NMR Blog

Smokin' Hot Inserts

2008-04-04T15:36:00.006-04:00

Norell’s Optimizer Inserts™, otherwise known as Smokin' Hot Inserts, are precision adapters that hold 3mm, 4mm or 4.25mm NMR tubes inside a 5mm spinner turbine. They are available for Bruker and Varian spectrometers and do not include the spinner turbine. This Patent Pending device is very useful and the perfect accessory for the NMR enthusiast.

Get your Smokin' Hot Inserts today!

Spring Forward with a New Catalog

2008-03-18T10:35:00.002-04:00

We are happy to announce that we have a redesigned catalog just in time for Spring. With NEW products, NEW technical drawings and a NEW unique style, this catalog is a candy for the eyes and health food for the mind. Please call or email us today for your free updated version.

1-800-519-3688
609-909-3700
customerservice@nmrtubes.com

"The Hollywood Swing of Things"

2008-02-19T10:55:00.002-05:00

Book your plane ticket now for the 49th ENC at Asilomar, March 9th-14th. When you arrive, go directly to the Acacia Suite and get into "The Hollywood Swing of Things". We will transport you to a era overflowing with extravagant boas, gangster hats and swingin cats. CLICK HERE for a preview of what's to come!

Visit the ENC website for more information on the conference. http://www.enc-conference.org/

NMR Sample Tubes for Lab Automation Systems

2008-01-21T15:51:00.000-05:00

We have specially manufactured NMR tubes for use with Varian and Bruker lab automation systems. They are supplied with our patent pending NorLoc™ caps that provide a sealing feature which prevents solvent evaporation with common NMR solvents and provides superior sealing for air sensitive samples. In addition to our standard 0.38mm wall tubes, we also make 0.77mm and 1.40mm wall tubes which are used for reducing salt effects when running bio-samples. All of our automation system tubes meet or exceed Bruker and Varian specifications for use in their automation systems.

For more information, please call 1-800-519-3688

A Cweet™ Confection for the Holidays!

2007-12-05T08:21:00.000-05:00

With sugarplums dancing in my head, I thought a blog about something sweet, or in this case Cweet™, would be perfect. The smell of holiday cookies makes my mouth water, but then the realization of how much sugar is in those cookies makes me take a moment to question whether or not I really want to indulge. Scenarios such as this are why food manufacturing companies are constantly on the look out for new low calorie or, preferably, no calorie sweeteners. An up-and-comer in this growing industry is Natur Research Ingredients of Los Angeles who announced they will be manufacturing Cweet™ Natural Intense Sweetener, which is derived from the fruit of a West African tropical plant named Pentadiplandra brazzeana Baillon. The extract from the plant is called brazzein and is "2000 times sweeter than sucrose when compared to a 2% sucrose solution in water and 500 times sweeter compared to 10% sugar solution. However, it has a taste closer to sucrose itself than other sweet proteins, such as thaumatin, is soluble in water and its sweetness is maintained even at 80 Celsius, which is important for foods that must be pasteurised, for instance. Wisconsin's Fariba Assadi-Porter uses NMR to study the structure-function relationships in brazzein and its analogues in order to understand precisely why this compound so stimulates our sweet receptors. Stable-isotope-assisted multinuclear NMR is the key that unlocks detailed chemical and structural information at the atomic level when the compound is present in living cells and interacting with the receptor. The team's current model of the binding of brazzein to the sweet receptor, suggests that the 54-amino acid protein chain binds at several points to the receptor. The sweet proteins do not share the same chemical properties as sugars like sucrose. In fact, these proteins do not interact with the same binding sites as sugars. "What makes these proteins sweet is far more complex than small sweeteners like sucrose, aspartame, etc," Assadi-Porter told SpectroscopyNOW, "There are many factors that dictate sweetness, such as the three-dimensional fold and large positive charges." She and her colleagues are now attempting to understand the detailed structural and chemical properties that are important for the sweetness of brazzein and its interaction with the sweet receptor." ("Sweet Structure Producer", spectroscopynow.com)

The complexity of the structure with the simplicity of the pleasure of something so sweet is amazing and even more intriguing is that brazzein tastes sweet only to old world monkeys and humans. I, for one, am thankful to be able to enjoy all the sweets in my life. May you all have a Happy Holiday Season and focus on all the sweets in your life.

The above excerpt was taken from this article in spectroscopynow.com. For more information, please refer to that article as well as the Wisconsin Alumni Research Foundation.

What is Pryex®?

2007-10-01T13:54:00.000-04:00

Pyrex® is a name we all feel comfortable with. It represents quality and in the laboratory glassware industry it is often thought to be the only option acceptable to buyers. It is amazing what the power of branding can do. Corning, Inc. did such a good job that Pyrex® became a genericized trademark for what is also known as borosilicate glass.

Borosilicate glass was developed slightly prior to Corning's take on the substance. It's first brand name was actually Duran®, developed by Otto Schott in the late 19th century. Another brand name currently used to refer to this type of glass is Kimax® which is produced by Kimble Chase.

Borosilicate glass is created by adding boron to the traditional glassmaker's frit of silicate sand, soda and ground lime. The glass produced has a thermal expansion coefficient about one-third that of ordinary glass resulting in a material that is less stressed by temperature gradients and more resistant to breaking. This along with other factors such as chemical damage resistence, refractory properties and physical strength are what make borosilicate glass a good choice for Norell's NMR tubes.

Desparately Seeking Sunshine

2007-09-14T16:18:00.000-04:00

by The Resonance Rhymer

The science of NMR is o' so fine
Fiddling and faddling with turbines, divine!
I research, I report
Throw test tubes for sport
When all I want is some warm sunshine

My skin is clammy, pasty and white
All day I dream of seeing natural light
Use the Raytector to tan?
Now there's a plan
One more FUBAR sample and I just might

I traded sunglasses for goggles
Why I chose this? The thought only boggles

CAFFEINE!!!

2007-09-12T09:23:00.000-04:00

We all know caffeine is one of nature's fabulous gifts. Without it, scientists everywhere would accidentally be nullifying experiments and creating havoc on a daily basis. Exhausted limp bodies would be collapsing on desks worldwide, resulting in samples and equipment crashing to floors simultaneously, creating massive earthquakes and disrupting sleeping children. As humane scientific individuals, we obviously don't want this to happen and therefore keep caffeine readily available and research the fantastic stimulant as much as possible. Thanks to some Canadian scientists working for the cause, we now know some more information about this wonderful molecule. Click here to read the latest in caffeine news.

NEW! Norell Graphic Packaging

2007-09-12T08:45:00.000-04:00

We are happy to announce our new graphic packaging. Yeah! Color is here! We have streamlined our box system to 5 sizes which bear a consistent visual theme incorporating "techy" features and bright colors inspired by nature. Keep your eye out and enjoy a little color therapy :-)

Increasing NMR signal sensitivity of samples containing high salt concentration

2006-12-15T16:46:00.000-05:00

A supplementary solution for increasing NMR signal sensitivity of samples containing high salt concentration, by reducing back ground signal noise.

There is a great article by Alexander E. Kelly, Horng D. Ou, Richard Withers, and Volker Dötsch titled “Low-Conductivity Buffers for High-Sensitivity NMR Measurements”, J. Am. Chem. Soc., 124 (40), 12013 -12019, 2002. 10.1021/ja026121b S0002-7863(02)06121-8 Web Release Date: September 13, 2002 Copyright © 2002 American Chemical Society , that demonstrates that salt concentration alone is not the decisive factor in controlling background noise levels created by high salt matrixes, but that concentration and ion mobility together need to be considered in reducing noise levels.

Many researchers have approached us with the need to have less sample volume, after adjusting to a new buffer, to take advantage of this effect. For changing sample volume, we are offering our customers several solutions. One option is to use our 5mm thick walled (1.4mm wall) NMR tube, which has a 0.19ml fill volume compared to the 0.71ml fill volume of our standard 0.38mm wall tube at 50 mm sample height. The second option involves using a new special spinner insert adaptor that holds either 4.25mm, 4.00mm, 3.00mm, 2.50mm, 2.00mm, 1.70mm, and 1.00mm NMR tubes in a 5mm spinner turbine. We have adaptors for both stock Bruker and Varian spinner turbines, and good NMR signal has been reported even when using a 1mm NMR tube with a 5mm cryo-probe. The advantage of using the Norell spinner insert, is that you do not need to purchase or have specially made spinners for the complete selection of NMR tube sizes. You can now determine very easily the tube size that performs optimally for the type of sample and sample volume that is called for in the experiment.

Call the Norell customer service department for more details on how to use the new inserts.

Molar concentrations and volume calculations in NMR tubes

2006-12-15T16:31:00.000-05:00

We recently had a student ask us about molar concentrations and volume calculations in NMR tubes, so we thought that the following example could possibly help out other students having similar problems. In the original question, the student asked for the molar and mass concentrations of a 25k Daulton protein, of which 2.5 mg were dissolved in 1 liter of water. We wrote the solution out in pen, because it was easier to read. Click the link below to view.

http://www.nmrtubes.com/blog/121506_formula.jpg

What type of ESR sample tube to purchase?

2006-12-08T16:59:00.000-05:00

We recently had a grad student ask us what type of ESR sample tube to purchase. He was performing a quantitative experiment involving a metal complex dissolved in toluene. The point of the experiment was to study the interaction of various wavelengths of UV radiation upon the interaction of the metal complex. We recommended that precision Suprasil ESR tubes be used, primarily because the solvent height will remain the same between samples, which will keep the sensitivity of the cavity about the same. Also, the synthetic quartz can transmit wavelengths down to 190nm, which is what the experimenter required. Our recommendation was to use Norell Part No. S-4-EPRSQ-250P, a 4mm OD X 250 mm length precision ESR tube which is the typical size used in 4 or 5mm finger dewars.

Shimming suggestions using various brands of NMR tubes.

2006-11-27T08:33:00.000-05:00

There is a great article written back in 1991 by Prof. Gerry Pearson which is still recommended reading for anybody seeking to study in more detail the methods of shimming a supercon NMR. One important aspect of the article to note, which we occasionally receive questions about, is the shimming technique to eliminate spinning side bands. Quite often, Grad Students ask us about this problem, only to find out that they are shimming only the Z and Z nth order shim packs and disregarding the X and Y and combination nth order ones! With out further ado, I would like to give you the link so that you can read this interesting article yourself.

You can find it at the University of Iowa site : http://nmr.chem.uiowa.edu/manuals/Shimming-GAP-NMR-magnet.pdf

Good luck with your shimming.

Scratches in the glass, does it matter to an NMR tube?

2006-11-17T17:05:00.000-05:00

We recently had a researcher call us with a problem of tube breakage. He was using a NMR tube washing unit to recycle his NMR tubes, and found that some tubes were breaking very cleanly at specific points along the tubes. After talking to the researcher, he indicated that the NMR tubes were stored in metal racks that had drilled out holes where the tubes were positioned into. At these points of contact, and after being placed into the rack during several cycles of usage, the metal hole portion scratched into the surface of the NMR tube.

Our Norell Technical Service Department informed the customer, that NMR tubes, like any other piece of glassware, become flawed when scratched and will develop a weak spot.

The point to be made, is never store a NMR tube in a metal rack, to prevent scratching on the tubes outer surface, resulting in tube failure.

Round or flat bottomed NMR tubes, what's the difference?

2006-11-17T16:38:00.000-05:00

Some researchers in the past have stated that round bottomed NMR tubes are superior to flat bottomed because they shim better, while others couldn't tell the difference. A researcher recently wanted to know what the differences were between the two types of NMR tubes and which type would be better for his experiments.

To answer his question, we have to take a brief look into a past experiment of about 20 years ago, that involved a study in determining the strength of NMR tube bottoms. The experiment involved dropping flat and round bottomed NMR tubes from a height of about 5 feet, to observe any changes in the tubes bottoms. After doing this to 100 tubes of each type, the flat bottomed tubes outperformed the round bottomed ones by not breaking as many bottoms. Round bottom tubes would break more often, because the round bottom tubes had a significantly thinner glass wall than a the flat one's. At the same time, shimming experiments revealed that when the experiment only contained flat bottom NMR tubes, that shimming between the tubes took the same amount of time as with round bottom tubes. There was only a difference in shim times, when round bottom tubes were mixed up with flat bottom ones.

So to answer the researchers question, if you already are using NMR tubes with round bottoms, for the sake of faster shimming times, buy round bottomed tubes. If all your tubes have flat bottoms, continue to use flat bottom tubes. Just don't mix up flat bottomed ones with round bottomed ones, if shimming times between tubes is important to you.

Background Signals in Quartz

2006-11-07T15:00:00.000-05:00

It has been well documented that damage to quartz, either by grinding, polishing or spot heating will cause increased ESR background signal. This is notably due to Si-O and Si-H bond breakage and the formation of unpaired electrons that once occupied these orbitals. A second less well known cause is the exposure to x-rays, gamma radiation, and intense UV radiation. It has been found that Quartz sample tubes, upon storage next to high energy radiation sources, have after a prolonged period exhibited strong EPR centers that were significant enough to cause interference of sample data. Should you have EPR sample tubes that are producing higher than average background signals, we recommend that you ship the tubes to Norell Inc. for re-annealing. The annealing temperatures that we use to prepare quartz sample tubes for EPR are high enough to reform any chemical bonds broken by the above conditions. Please contact our Technical Service Department at 609-909-3700 for further details.

Using Hydrofluoric Acid or Ammonium Bifluoride to clean NMR tubes

2006-11-07T14:58:00.000-05:00

Some NMR tube cleaning procedures have called for the use of HF and/or (NH4)2F2 before final rinsing with DI water and drying. Since glass is solubilized with these reagents, the NMR tube walls become thinner and also irregular with time, since the dissolution rate is uneven and unpredictable on the wall's surface. Not only will the NMR tube become compromised in its ability to hold sample without breakage, but the quality of the NMR spectrum will become degraded, because of the irregularity of the wall thickness. Our recommendation is to use a high quality glass cleaning surfactant, such as NRS-250, that removes organic contaminants without damage to the glass walls of the NMR tube and extends the life of the NMR tube.

Using EVA and Polyethylene NMR Tube Caps with Organic Solvents

2006-11-07T14:56:00.000-05:00

While preparing a sample for NMR, a Laboratory Technician noticed that his sample solution became colored after shaking with CDCl3 while in the NMR tube. The question was directed to our Technical Service Department, as how to prevent this from occurring when making up new samples. Upon questioning, the Technician mentioned that he was using standard EVA NMR tube caps that were supplied with his NMR tubes. He would prepare his samples for NMR by adding solid sample directly to the tubes with Chloroform-d, and then inverting the tubes to facilitate mixing. After further questioning he mentioned that the solvents were in contact with the caps. We informed him that in using halogenated solvent with EVA or Polyethylene, there is a risk of dissolving the cap and/or leaching out monomers, plasticizers, curing agents, and color components from the plastic. Our recommendation was to only use Teflon® caps, TC-5-PTFE or TC-10-PTFE, to avoid any possible contamination of sample solution from leaching effects of the solvent.

How clean are NMR tubes out of the box?

2006-10-13T10:03:00.000-04:00

A researcher recently wanted to know how clean NMR tubes were out of the box, and if there were organic contaminants on the glass. His question came from reading the below articles on NMR tube cleanliness that were posted on a manufacturer's website, and the AMMRL NMR discussion group. The concern is obvious, but the correct answer is different for each tube manufacturer.

“NMR tubes are not 'analytically clean' when delivered to you. So if your NMR samples require scrupulously clean glass, follow the procedures below for Difficult Cleaning Problems to assure your sample purity is never jeopardized. Since NMR tubes are formed over a metal mandrel and certain organic lubricants are used, these cleaning steps will assure that any trace organic or inorganic residues from these procedures is removed.”reference http://www.wilmad-labglass.com/services/NMR_010.jsp

I also found http://calmarc3.cchem.berkeley.edu/archives/ammrl/96/archive/0194.html where the marketing manager of the same company discusses out of the box NMR tube cleanliness.

Some other brands do not mention a specific manufacturing process, so pre-washing would seem logical based on reading the above.

It seems that some manufacturers use organic solvents routinely during the tube manufacturing process, and that contaminants are present in out of the box tubes.

Factually speaking, modern tube making processes have eliminated the use of petroleum oils and the like, strictly because of contaminant issues with customers. The mandrel process dates back to earlier times, when state-of-the-art tube making equipment was non-existent. As a matter of fact, Norell Brand NMR tubes are manufactured using a processes that uses no lubricants, organic solvents, or inorganic reagents.

It's hard to believe that for critical NMR applications, a manufacturer would employ antiquated use of petroleum oils in glass manufacturing, when better techniques are readily available.

So to answer the researcher's initial question, only Norell NMR tubes are completely free of metal and organic impurities, and that pre-washing Norell Brand NMR tubes is unnecessary.

What temperature range is safe for my NMR tube?

2006-09-15T11:48:00.000-04:00

For whatever reason, if the sample temperature must be chilled down, or oppositely heated up beyond room temperature, the recommend glass of choice is ASTM Type 1 Class A glass. NMR tubes made from this glass type have thermal expansion rates 60% less than that of standard boro-silicate glass. Since some NMR tubes require withstanding temperatures down to -70 ^oC or up to +200 ^oC, the increased expansion rate can cause conventional boro-silicate NMR tubes to crack. We have a full line of NMR tubes that are made from ASTM Type 1 Class A glass under the “Select Series” Brand, which you can see on our web page www.nmrtubes.com.

Why does one brand of NMR tubes fit differently into my spinner turbine than another brand?

2006-09-15T11:44:00.000-04:00

Some brands of NMR tubes have outside diameter variations that present problems when loading sample into a spinner turbine, such that serious damage will occur to the NMR probe. Special care must be taken with stringent attention to quality control when monitoring NMR tube production, so that outside diameter variations are held to a minimum. In Norell’s manufacturing process, with the use of state-of-the-art equipment, NMR tube outside diameter variations are held to extreme minimums.

Keep in mind that spinner turbine o-rings can be worn out too and need replacing. From field tests we have found that spinner turbines also vary considerably in bore inside diameter and are not not manufactured as precise as glass NMR tubes. It is therefore recommended to service spinner turbines periodically along with replacement of the o-rings.

What pressure can my Norell NMR tube hold?

2006-09-15T11:23:00.000-04:00

Some reaction mixtures that are out-gassing in the NMR tube, or air-sensitive samples that require pressurizing the NMR tube with inert gas would require the NMR tube to withstand pressure without failure. This question is asked quite often and the formula bellow provides the solution. Please keep in mind that there are also other factures that can cause tube failure under pressure, such as a worn out and scratched tube. Scratches are weak points in glass, and our suggestion is to always use a new NMR tube with samples that require sealing samples under pressure.

Maximum allowable pressure P_max = NMR tube wall thickness (mm) / NMR tube O.D. (mm) X 2,000 psi

Example : 0.38mm/5mm X 2000 psi ≈ 150 psi

SMASH Poster Abstract Review

2006-08-25T17:21:00.000-04:00

Polymeric NMR Sample Tubes Evaluated in a 1 mm Microprobe

Michael J. Cavaluzzi1, David J. Kiemle2, Deborah J. Kerwood3, and Philip N. Borer1,3
1. Advanced Resonance Technologies, Inc., 111 College Pl, 2-212 CST, Syracuse, NY 13244-4100 2. Chemistry Department, SUNY College of Environmental Science & Forestry, 121 Jahn Lab, 1 Forestry Dr, Syracuse, NY 13210-2726 3. Chemistry Department, Syracuse University, Syracuse, NY 13244

Polymeric NMR Tubes have advantages over glass in most applications: • Polymeric tubes are shatterproof • Ultra-thin walls afford sensitivity increases of 20-40% • Polymer tubes are easy to fill and to recover sample • Standard probeheads and sample changers can be used. Here we describe the performance of polymer tubes compared to glass capillaries, both having 1 mm outside diameter. The mass sensitivity of 1 mm probes about four times that of 5 mm probes, yet the former have not found wide acceptance due to the difficulty of using glass capillaries. Samples were tested on a Brüker DRX-600 with a 1 mm TXI room temperature probehead. Primary comparisons are between polymeric tubes with inside diameters of 0.826 (ART-1A), 0.851 (ART-1B), and 0.889 mm (ART-1C), and a glass capillary with ID estimated at 0.814 mm. The resolution for 1% CHCl3 in d6-acetone was comparable at half-height (1 Hz) while the lineshape for polymer tubes was typically 20% broader at the base. The signal-to-noise ratio in the polymer tubes scales almost exactly with volume increase in the active region of the receiver coil (tested with 0.1%, 1% and 10% ethylbenzene in CDCl3). 30-40% less time will be required to achieve the same S/N in the larger ID polymer tubes compared to glass capillaries. Spectra acquired in ART-1C tubes will be shown, including: (1) a 1D 1H-spectrum of 1 microgram of stigmasterol where the chemical shifts are easily resolved in 512 scans, (2) a 2D 1H-15N-HSQC of 70 micrograms of 15Nu-ubiquitin shows that a 21 min acquisition distinguishes the expected peaks and has an increase in S/N ~ 30% over a glass capillary, and (3) a 2D 1H-15N-HSQC of 15Nu-labeled NCp7 protein from HIV-1. The mass of the protein is about 2% of that often used in a 5 mm room temperature probe (1 mM, 500 microliters). MJC and PNB hereby disclose their financial interest in ARTech, represented at the SMASH conference by Norell, Inc. NMR tubes with other dimensions will be available soon. Supported in part by NIH grant RR18442 to MJC and PNB.

Pressure limits of NMR tubes

2006-08-17T11:57:00.000-04:00

A customer recently asked if a glass NMR tube could hold 5 bar of pressure, and that he wanted to do a catalytic reaction under pressure during data acquisition. A standard NMR tube with a 0.38 mm wall and 5mm OD has a limit of about 10.3 bar, from P_max = tube wall thickness ÷ tube wall O.D. X 135 bar.

It is suggested that when using an NMR tube for higher pressure experiments within the recommended pressure rating, that you check for any damage to the surface of the glass tube before pressurizing, since this could lead to tube failure.

Can a NMR tube de-resolve a portion of a sample's spectrum?

2006-08-04T14:18:00.000-04:00

Recently we received spectra from a customer who was questioning a loss in resolution between two different NMR tube brands using an identical sample for the test.

spectrum1

spectrum2

The data was acquired on a Bruker DRX 500 taken at a temperature of 303 K and spin rate of 20Hz. The compound was from a stock solution containing a chiral, aliphatic, small molecular weight organic compound. The customer also mentioned that a shim file derived from gradient shimming was used and then further hand shimmed on Z-Z5, 8 scans with no line broadening.

Looking at the aliphatic region between 1 and 2.2 ppm, the two spectra seemed identical. However, between 7.35 and 7.4 ppm there was a noticeable difference between the two tubes in resolving the long range H-H coupling of a imine CH peak. It was assumed by the customer that these differences were caused by quality differences between the tube brands.

The customer's concerns were very convincing until they realized that when a NMR spectrum is acquired, the raw data is in the form of a free-induction decay which is carried over the entire length of the spectrum, and converted into a frequency domain function by Fourier transform. Therefore, the entire spectrum is subjected to one resolution constant, not many at various points of the spectrum. Since NMR sample tube quality plays only a partial role in resolution, other effects such as slight changes in the sample's water content, pH effects from the glass, or others, can lead to chemical exchange broadening, which could have caused this customer's problem.

It is important to note that strict quality control standards are used in NMR tube manufacturing. Since variation in concentricity and camber is at its worst ± 0.025 mm and ± 0.075mm in a disposable tube, it is critical not to rule out chemical influences that will effect spectrum resolution.

Click here for useful articles on shimming magnets.