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Article
Rapid, Efficient Quantitation of Water in Solvents and Solvents in Water using an Ionic Liquid-based GC Column
Dilani A. Jayawardhana, Ross M. Woods, Ying Zhang, Chunlei Wang, Daniel W. Armstrong
Developing versatile, rapid and accurate analytical techniques for the detection and quantification of water in a variety of materials remain an important and ubiquitous analytical problem. Indeed, water is one of the most prevalent impurities in many industrial and consumer products and processes. In other cases water is an essential component, the concentration of which must be known accurately and controlled. Here, we report an effective and sensitive ionic liquid (IL) based capillary gas chromatographic (GC) method with a thermal conductivity detector (TCD) to determine water content in liquid samples. The open tubular capillary columns, coated with specific ILs developed in this study, increased the sensitivity and increased the ruggedness of this technique.
Trace Metabolic Profiling and Pathway Analysis of Clomazone Using Liquid Chromatography Coupled with Triple Quadruple-Linear Ion Trap Mass Spectrometry in Predictive Multiple Reaction Monitoring Mode
Wei Zou, Hagai Yasuor, Albert J. Fischer, and Vladimir V. Tolstikov UC Davis Genome Center, Department of Plant Sciences, University of California
Davis Detection, analysis, and characterization of low-abundant metabolites remain an unresolved problem in metabolic studies. In the present study, we report a novel approach addressing this challenge. This current methodology derived from the predictive multiple reaction monitoring (pMRM) mode available on triple quadruple-linear ion trap mass spectrometers. pMRM mode could offer the highest sensitivity among various acquisition modes in studying trace levels of metabolites of herbicide clomazone in plants. In addition, pMRM mode allowed identification of positional isomers of metabolites. Unknown metabolites were further identified and validated by obtaining accurate masses and isotopic ratios using selected ion monitoring (SIM) and data-dependent MS-MS scans on high resolution LC–MS.
Columns
LC Troubleshooting: How Do You React to the Symptoms that Your LC Column Has Major Problems?
John W. Dolan
With the popularity of medical shows on television, you'd think we'd all know how to act in a medical emergency. After all, we know what to do when we have an emergency with our liquid chromatographic (LC) column, don't we? Or is it really an emergency? In this month's LC Troubleshooting, we'll consider the process of column triage. When will the column survive on its own? When does it have recoverable injuries? And when is it beyond resuscitation? We'll concentrate on three primary symptoms of column failure: increased peak tailing, increased pressure, and changed retention times.
GC Connections: Headspace Sampling
John Hinshaw
Headspace sampling for gas chromatography (HSGC) prevents nonvolatile residue accumulation in the inlet and column entrance while simplifying sample preparation. Although it is not applicable to solutes of low volatility, chromatographers use HSGC to advantage for a wide range of samplematrix combinations. This installment of GC Connections reviews the basics of headspace sampling and how it is applied to various analytical challenges.
Coupling Matters: GCXGC with Fluidic Modulation
Paul McA Harvey, Samuel DH Poynter, Robert A Shellie
Properly informed column choice greatly simplifies the process of method development and provides greater flexibility in instrument settings for comprehensive two-dimensional gas chromatography with fluidic modulation. In the present investigation a long (20 m) narrow-bore (0.10 mm i.d.) column was used in the first separation dimension. In this way, the separation column itself provides sufficient pressure-drop to minimise flow disturbance in the first dimension column caused by actuating the modulator valve. Employing a narrow-bore column in the first dimension is highly beneficial since it is also more suited to lower volumetric flow rates and therefore permits use of a longer modulation period without causing modulator breakthrough. Enantioselective separation of spearmint essential oil was performed to demonstrate performance of a fluidic modulation system. A 3 s separation window provided adequate space with minimal wrap-around for separation of the terpenoid compounds present in the spearmint oil sample and the column ensemble and flow arrangement used easily permitted a 3 s modulation period without any evidence of modulator breakthrough.
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