Gas Chromatography – Liquid Chromatography
Mass Spectrometry – Sample Preparation – Reference Standards
GAS CHROMATOGRAPHY
Keep Your GCs Running Reliably – Inlet Maintenance
Routine maintenance is an important step in getting the best performance from your gas chromatograph. There are numerous parts in the inlet that require regular replacement including inlet liners, liner O-rings, septa, ferrules, and, for some instruments, inlet seals. Replacement schedules can vary depending on samples and run conditions, but you will reduce your need for troubleshooting when you get your systems on a preventative maintenance schedule. Components and steps may vary based on the instrument or its configuration. Your instrument manual is always the definitive source of instructions.
Split vs. Splitless – Which Injection Mode Should I Use?
Split and splitless are the two most common GC injection techniques. But how do you know which to use? In this video, we follow a sample through split and splitless injections and compare the strengths of each technique to help you choose the right one for your analysis.
An Introduction to Low-Pressure GC-MS (LPGC-MS)
Recently we have demonstrated how low-pressure GC-MS can speed up pesticide analysis in food threefold. Today, we are sharing the background for this innovative technology and explaining how it works and why a new simplified setup makes it more accessible for routine analysis.
Is There a Gas Leak in Your GC? Here's What Can Go Wrong...
Gas leaks are one of the most prevalent and troublesome problems when doing gas chromatography. They can negatively affect your chromatography in a number of ways. This quick video details the headaches leaks can cause and explains why an electronic leak detector is the best way to prevent these problems.
Leak Checking a GC System, A Leak Free System Will Allow Greater Sample Throughput and Less Downtime
We recommend leak checking the system before beginning the column conditioning cycle and eliminating all leaks before proceeding with column conditioning and analytical work.
- Begin at the carrier gas source and regulator and carefully check each fitting and connection along the pathway to the GC.
- Turn off the oven fan and check all fittings, adaptors, and connections inside the oven as well.
- Don't forget to check all column and guard column connections, such as connectors or unions as well – often a leak can be traced to a column end that was crushed during installation.
Check These 10 Common GC Leak Locations
Even the smallest gas leak can cause a loss in sensitivity, contaminate samples, damage columns and instruments, and lead to a lot of wasted time. Grab your leak detector and check these 10 common leak locations now to keep your GC running smoothly.
Spring Cleaning Your GC System
Spring has sprung and now is a good time to give your GC system a thorough going over.
Importance of Inert GC Pathways
When measuring trace-level impurities, your GC system needs to be optimized and inert. If it is not, low-level compounds cannot be adequately distinguished from the baseline and accurate identification and quantification become difficult or impossible. Sensitivity is strongly influenced by column factors including inertness and bleed.
Carrier Gases: Hydrogen as an Alternative to Helium
As the Helium shortage continues to grow, Helium prices are rocketing sky high and in some cases companies are being told they can not get any. Switching to Hydrogen as a carrier gas offers some great advantages.
Tech Tip – How to Correctly Use a Press-Tight Connector
If you've ever attached a guard column, connected two columns together, or repaired a broken column, you know how essential it is to have a clean, reliable connection. In this Restek tip, we'll show you how to ensure a quality connection using a Press-Tight connector.
LIQUID CHROMATOGRAPHY
Featured Video: Why Are There So Many C18 Columns?
From end-capped to aqueous, there are a multitude of C18 phases to choose from. But, a C18 is a C18 right? In this video tip, Restek explores the world of C18 columns. They'll identify the parameters you should consider when selecting a phase and discuss the advantages of using one that is well suited to your specific analysis.
Keep Samples Moving Through the Lab by Preventing High HPLC Backpressure
High backpressure is a fact of life for HPLC and UHPLC analysts but diagnosing problems and preventing future ones is the best way to keep your instruments up and running. Read on to learn how to ensure removal of particulates that can cause unexpected downtime.
Good HPLC Practice Guide
The Good HPLC Practice Guide, developed by Knauer, is a helpful aid in perfecting your practices and includes ideas about your mobile phase, UV detection, sample preparation and lab safety. It contains a convenient checklist to consult when starting up or shutting down your HPLC system.
Understanding HILIC Separations to Improve Your Results
In HILIC (hydrogen interaction liquid chromatography), the three main mechanisms involved in analyte retention are:
- The adsorption of an analyte on polar groups of the stationary phase as a result of hydrogen-bonding, electrostatic (coulombic) and dipole interactions.
- The partition of analytes between the organic bulk mobile phase and the water rich surface layer surrounding the stationary phase.
- Ion exchange interactions.
YMC provides a review highlighting influences on the separation mechanisms in HILIC
to provide a helpful tool for method development and troubleshooting.
Click here for more information.
For column dimensions and pricing on the columns mentioned in this article:
Neutral Polar Ligands
YMC-Triart Diol-HILIC Analytical Columns
YMC-Triart Diol-HILIC uHPLC Columns
YMC-Triart PFP Analytical Columns
YMC-Triart PFP uHPLC Columns
Positively Charged Ligands
YMC-Pack NH2 Analytical Columns
YMC-Pack Polyamine II Analytical Columns
Negatively Charged Ligands
YMC-Pack SIL-06 Analytical Columns
YMC-Pack SIL Analytical Columns
Addressing Bacterial and Fungal Growth in HPLC Mobile Phases and Columns
When using 100% aqueous mobile phases, bacterial and fungal growth in the column is a concern.
Click here for tips on how to prevent this from happening, and how to deal with it if it does.
Choosing the Right HPLC Column
Follow our HPLC column selection flow chart as a starting point for your method development. Click here to get started.
MASS SPEC
Electron Multiplier FAQ - How to Properly Pre-condition Your Multiplier
To get the longest lifetime from your multipliers, they should be pre-conditioned; this allows loosely bonded water molecules to be released from the surface, which can shorten the life of the multiplier.
To do so, place your multiplier under vacuum. It is recommended that a vacuum of 10-6 Torr or better be used.
Once the appropriate vacuum is reached, apply a small input to the multiplier. In counting mode approximately 15,000 counts/second. In current mode approximately .1uAmp.
Raise the voltage slowly to reach an appropriate gain level:
- In counting mode this should be approximately 107.
- In current mode this should be approximately 105.
Run the multiplier like this for several hours.
How do I clean a multiplier that gets contaminated?
- In the event that a multiplier becomes contaminated, it should be flushed with isopropyl or methanol.
- The multiplier can then be blown with dry nitrogen and baked at 150°C until dry.
- Multipliers should never be cleaned in acid, which will hurt performance and reduce overall lifespan
SAMPLE PREPARATION
SPE Does Much More than Sample Cleanup
In a perfect world, samples could simply be injected directly with no negative effects. But, in reality, matrix components can decrease analytical accuracy and increase instrument maintenance. SPE is a common technique for dealing with matrix issues, but it's also useful for other purposes. In this article, Restek reviews the primary uses of SPE and explain how the right approach saves time and reduces frustration.
Solid Phase Extraction (SPE)
SPE is a broad term to describe the digital (step wise) separation technique where liquids contact sorbents, and organic compounds or ions in the liquid adsorb to the functional group(s) of the sorbent.
QuEChERS
QuEChERS (pronounced Catchers), is an acronym for Quick, Easy, Cheap, Effective, Rugged and Safe. The process is a sample extraction and clean-up technique widely used for the analysis of multiple residues in food, forensic and environmental samples.
REFERENCE STANDARDS
How to Sonicate Your Reference Standards
Depending on how your reference standards are stored, it's possible some of the analytes may fall out of the solution. This will impact the analyte concentration, which can be particularly detrimental for reference standards containing long-chained alkanes such as Restek's MOSH/MOAH Retention Time Standard. Sonication can be used to help redissolve these analytes into the solution at the proper concentration.
How Long are Standards Good After the Ampul is Opened?
It's not uncommon for analysts to ask: how long are reference standards stable after opening the ampul when stored and handled properly? Restek designed an open ampul stabiity study using the 200+ pesticides in their LC and GC multiresidue kits to answer this question.
Matrix Spiking – Terms and Technique
Matrix Spiking is a technique that is used to evaluate the performance of an analytical procedure when testing a specific sample (matrix) type.
- A matrix spike test helps answer the question “Are our tests results valid when using this this method to test for samples of? A “good” matrix spike result increases your confidence in the accuracy and validity of the sample test results.
A Matrix Spike is generated by adding a known amount (the spike) of analyte to a sample, testing the spiked sample, and determining if the amount added has been recovered; this is sometimes referred as % recovery.
- In practice, two portions of the sample are prepared for testing. In the “matrix spike” portion, we add a known amount of standard (this increases the concentration by a known amount). When we test the sample and then the matrix spike, the matrix spike result should be higher by that known amount added. If the analytical procedure is not working well for your sample, the matrix spike result will be higher or lower than expected.
The Importance of CAS Numbers when Requesting Standards
Going through a long list of compounds for an analytical standard and adding a CAS number for every compound on the list is something nobody wishes to do. Unfortunately, it's become crucial for accurate processing of ever lengthening analyte lists, especially for international methods. Many drugs and pesticides have local variations on name or spelling while CAS numbers are constant throughout the world. CAS numbers are now the primary identifier for analytes in most, if not all, ISO 17034 Certified Reference Materials.
To let us help you find the best solutions for extensive analyte lists please:
- Include CAS numbers whenever you have them.
- Include a technical contact to clarify any oddities in a list when submitting a quote request.
- Let us know if you need us to add the CAS numbers for you. Otherwise we'll need to check if you have or can get them.
- If you need us to add CAS numbers, understand it will take us time to do so, and that you'll need to review and approve the CAS numbers and associated chemical names before you order.
The following 2 sites are places where CAS numbers can be found:
Contact our Technical Team for further assistance.