All Things Chromatography
TLC plates come in lots of fun forms and sizes—at least we think they’re fun! You can differentiate TLC plates by:
• Adsorbent material that makes up the layer itself
• Type of plate backing
• Layer thickness
• Plate size
• Fluorescent indicator - UV254 (yes or no)
• Format of scoring (or none)
• Preadsorbent zone (yes or no)
• Channeling (yes or no)
All clear now? Didn’t think so! In this first article of our two-part series, let’s look at the first four factors to help you make the right choice.
Most often, the actual layer is silica gel, but it can also be aluminum oxide, cellulose, microcrystalline cellulose, Florisil®, as well as various forms of modified silica gel such as reversed phase layers (C2, C8, C18), amino, cyano, and others. Which layer should you use? It depends on the compound you’re separating. Your best bet is to check what others have done first so you’re not reinventing the wheel. Historical data matters!
The layer’s backing is most often glass, because it can tolerate the most chromatography solvents. Using a flexible backing—namely polyethylene or aluminum—makes sense only when you must quickly and easily cut the plate (or sheet) into smaller sized pieces. Glass can also be cut or purchased pre-scored, so really it comes down to preference, availability, and price.
Thickness depends on the chromatographic separation you’re doing. For instance, the thickness for standard analytical TLC is 250um (1/4th of a millimeter). But for quantitative level analytical TLC, you’ll need a thinner plate—typically 200um, 150um, or even 100um. This category of TLC has a special name: high performance thin layer chromatography, or HPTLC. Meanwhile, thicker plates (500um, 1000um, 1500um, and 2000um) are best for preparative applications where you’re separating much larger samples. In this case, you’ll want to recover the separated sample components with a scraper or suction device.
This is a lot easier to figure out—whew! You just need to know about how many samples you want to run at the same time and what distance you need to chromatograph your samples for adequate separation. Standard sizes are 20x20, 10x20, 5x20, 10x10, 5x10, and 2.5x7.5 (microscope slide). Of course, all measurements are in centimeters. Additional specialty sizes are 2.5x10, 5x5, 2.5x5, and, our favorite, 20x40. Yes, you do need a very large custom developing tank for that one!
We hope this gets you on the right track when you need TLC plates. For more info, stay tuned for part II, where we explain fluorescent indicator, scored plates, preadsorbent zone, and channeling. We find this stuff so exciting and can’t wait to share it with you!
Have a great TLC day!
Our friends at SeparationsNow.com recently published an article about how thin layer chromatography is being used to help identify powerful antioxidants in the Pereskia bleo plant.
Here's some excerpts:
Pereskia bleo is among 17 species of Pereskia cacti, consumed as a vegetable as well as being used as a traditional herbal medicine in Latin America and Asia. Its leaves have been used to treat diseases associated with inflammation, such as high blood pressure, diabetes and even cancer. Supporting its medical use, analyses have shown that P. bleo contains several bioactive elements, including alkaloids, flavonoids, sterols, terpenoids and carotenoids.
To properly analyse herbal extracts, chromatographic analysis of the entire sample should be used.
However, the major systems used for analysis – NMR, GC-MS and HPLC-MS – are prohibitively expensive in developing countries, where herbal extracts are most widely used. A more affordable alternative is thin-layer chromatography
Our friends at ChemistryWorld recently published a piece about how thin layer chromatography was used in connection with other analytical methods to determine the use of synthetic dyes in the clothing industry throughout the 1800s.
Here's a few excerpts:
‘This analysis reveals important information for conservators and curators of fashion, raising interesting observations and questions,’ saysJeffrey Church, a molecular spectroscopist at the Commonwealth Scientific and Industrial Research Organisation (CSIRO) in Australia who worked on the study with colleagues from the National Gallery of Victoria...
After taking small samples from each dress, the researchers separated and analysed the dyes and mordants, which are used to bind the dyes to the material, using various techniques, including thin layer chromatography, surface enhanced Raman spectroscopy and energy dispersive x-ray spectroscopy
We appreciate so much the work being done by educators around the world to engage students in better understanding science.
We've found that most students respond well to videos, and we'd like to offer a couple that we think might help students grasp the concepts of chromatography while providing some entertainment.
We encourage all educators to use and share these if they find them useful.
Whether you use chromatography supplies or work for a lab, university, or organization that does, we'd like to hear from you with this extremely brief survey (five questions or fewer)
Bob Bickler is a Technical Specialist with 38 years of chromatography experience and writes for The Flash Purification Blog.
Recently, Mr. Bickler wrote a post that outlines something we've been telling people for years:
Here's an excerpt:
I know your time is valuable but investing 10 minutes of it running TLC prior to your flash purification will give you much better separations, increased fraction purity, and reduce the amount of wasted solvent. You really have nothing to lose and everything to gain.
In addition to Flash Chromatography, we believe the same principle applies to HPLC and other separation methods.
This week, we're participating in the 29th Annual Research Festival at the National Institutes of Health.
The festival features workshops and posters on a wide variety of subjects, from RNA Biology and Theapeutics to chemical biology and research on vaccines.
We will be at Booth #267 at the exhibition on September 17 and 18.
If you will be at the NIH Research Festival, we hope you will stop by booth 267.
We were recently contacted by U.S. Korea Connect - an organization that promotes trade between the two countries. They had read about our trip to Korea and wanted to talk about our experiences in the Korean marketplace.
Our friends at U.S. Korea Connect have now published a Success Story based on our experiences, here's an excerpt:
Analtech Inc. works closely with its distributors, ML Science and LK Lab Korea, to connect with labs throughout the region and increase the company’s market share in the chromatography field.
U.S. Korea Connect also asked for some thoughts on making connections in Korea, which led to a blog post, here's an excerpt from that post:
We appreciate the recognition from U.S. Korea Connect, we're grateful to our friends at ML Science and LK Lab Korea for their partnership, and we are thankful to the Delaware Office of International Trade and the World Trade Center Delaware for their continuing support and assistance.
The 43rd Annual Conference of the National Association of Scientific Materials Managers will be held in St. Petersburg, Florida July 22-30, 2016.
The Conference Host, Ana Rodriguez with Rollins College, offers this preview:
The 42nd Annual Conference of the National Association of Scientific Materials Managers in Long Beach, California was a great success.
From insightful and inspiring presentations from Sean Kaufman to sessions on improving inventory control and Green Chemistry, this conference offered everyone valuable information and great opportunities to share expertise.
And yes, we had a great time seeing all of our NAOSMM friends on the Queen Mary and around the Long Beach area.
Here's a look at the conference: