Archive for 2013

How much buffer to weigh and what’s the best way to prepare my buffered mobile phase?

Occasionally we get this question and sometimes folks do need help with the calculations. We discussed in a previous post what a buffer is composed of. Click on this link if you need to review it: When should you use a buffer for HPLC, how does it work and which one to use? For a […]

When should you use a buffer for HPLC, how does it work and which one to use?

As many of you know, buffers are usually used in mobile phases to hold the pH constant. They are composed of a weak acid or weak base, combined with its conjugate base or acid in solution that is at least partially aqueous (at least 50%).  This pair of compounds exists in equilibrium, so that when […]

Keep your GC organochlorine pesticide analysis systems up longer by using split injection.

As noted in earlier blogs, “Fast Organochlorine Pesticide Analysis Using Hydrogen Carrier Gas with Split Injection GC-ECD” and “Split Injection Minimizes Endrin and DDT Breakdown for GC-ECD Analysis of Organochlorine Pesticides”, split injection is a viable alternative to splitless injection for analysis of organochlorine pesticides (e.g. when using EPA Method 8081). Notable benefits include: 1.  […]

GC compound responses lower than expected? Maybe this will help.

We occasionally gets calls in tech service from a customer who has been experiencing lower than expected compound responses when analyzing a chemical standard.  In many cases we hear “It worked fine the last time we did it”.  So what could have happened since the last time you successfully did the analysis?  Several of the most […]

Column Bleed & Septa Bleed – Same Old Thing!

On a seminar trip I was confronted with describing why septa bleed and column bleed are different. My canned answer is that septa bleed has a base peak of m/z 73 and column bleed has a base peak of m/z 207 and we can prove this with a GC-MS. Keep in mind that both column […]

Molecular Sieve 5A & 13X packed columns – Installation / Conditioning / Helpful Hints

Molecular Sieve 5A & 13X Columns (packed) Molecular Sieve 5A & 13X (micropacked) Things to Consider Before Ordering a Packed Column . Following the steps below will ensure that your Molecular Sieve packed column is ready to use just several hours after installation.  You should only use dry high-purity Nitrogen as the carrier gas to […]

Molecular Sieve Packed Columns and Fixed (Permanent) Gas Analysis

For some reason, I find molecular sieve packed columns interesting.  Maybe it’s because they have a niche as the go-to columns for fixed (permanent) gas analysis.  Maybe it’s because they are old school technology that a new generation of analysts are always asking questions about.  Maybe it’s because using them successfully is a function of […]

[24] What do Chromatograms tell us? Base line is Rising with a Near Constant Slope..

Chromatograms are like fingerprints.  If you can “read” chromatograms well, you often can find a plausible cause. In this series, we will show a series of GC-chromatograms that are obtained from users and discuss some potential causes for the phenomena. Then we can move into some solutions for improvement.   In chromatography, we always like […]

Analyzing pesticides in herbal tea using QuEChERS and GCxGC-TOFMS of course!

Herbal tea, a non-caffeinated drink made from plants, herbs, or spices has been used throughout history for its potential medicinal benefit.   Various herbal material is mixed depending on the desired medicinal or flavor properties for the tea.   As with any plant based commodity, there is the potential for pesticide residues to remain in the final […]

PAHs in PrAHa (PrAgue, CzecH Republic) at RAFA

I must have been thinking about my Rxi-PAH GC column lecture at the Recent Advances in Food Analysis meeting as I strolled around Prague taking in some of the sights, including the beautiful St Vitus Cathedral shown in my first photo below, because I looked down at the floor tiles and saw PAHs.  I then […]