Improvements in high-temperature PTV injection for HT-CGC

without abstract

Fast capillary gas chromatography. Comparison of different approaches

Savings in analysis time in capillary GC have always been an important issue for chromatographers since the introduction of capillary columns by Golay in 1958. In laboratories where gas chromatographic techniques are routinely applied as an analytical technique, every reduction of analysis time, without significant loss of resolution, can be translated into a higher sample throughput and hence reduce the laboratory operating costs. In this contribution, three different approaches for obtaining fast GC separations are investigated. First, a narrow-bore column is used under conventional GC operating conditions. Secondly, the same narrow-bore column is used under typical fast GC conditions. Here, a high oven temperature programming rate is used. The third approach uses a recent new development in GC instrumentation: Flash-2D-GC. Here the column is placed inside a metal tube, which is resistively heated. With this system, a temperature programming rate of 100°/s is possible. The results obtained with each of these three approaches are compared with results obtained on a column with conventional dimensions. This comparison takes retention times as well as plate numbers and resolution into consideration

Development of an interface for directly coupled solid-phase extraction and GC-MS analysis

Solid-phase extraction (SPE) is widely used as a sample preparation technique in numerous application areas of chromatography. Large-volume injection is an attractive technique for coupling SPE to gas chromatography (GC) because it provides improved detection limits and circumvents the need for miniaturization of the SPE instrumentation. In this article, the authors describe how they linked an SPE system with a GC-mass spectroscopy (MS) instrument using an interface consisting of a switching valve, a short length of capillary tubing, and a restrictor. They applied large-volume programmed temperature vaporization injection to transfer the SPE eluate into the gas chromatograph. They tested the performance of the SPE-GC-MS system by analyzing two real-world samples: caffeine in urine and triazines in drinking water. Both automated large-volume injections and on-line SPE-GC-MS experiments showed good repeatability at the desired concentration levels

Determination of phenolic derivatives of antipyrine in plasma with solid-phase extraction and high-performance liquid chromatography-atmospheric-pressure chemical ionization mass spectrometry

This manuscript describes a method to determine antipyrine and its phenolic derivatives in plasma by reversed-phase high-performance liquid chromatography–mass spectrometry (RP-HPLC–MS). The sample pretreatment consisted of a C18 solid-phase extraction (SPE), to remove the salts and proteins. The retention behavior of antipyrine and its phenolic derivatives in the SPE procedure was estimated by the k values determined on a C18 HPLC column at different pH values and with different buffer compositions. Recoveries of antipyrine and its phenolic products were 90% in water and 100% in plasma. Atmospheric pressure chemical ionization (APCI) was used to introduce the components into the mass spectrometer. The mass spectrometer was operated in the single ion monitoring mode (SIM mode) as well as in the selective reaction (SR) mode. The SR mode or tandem MS resulted in the best signal-to-noise ratio, with a detection limit for antipyrine of 6 pg in 20 µl. For the different phenolic antipyrines, different target ions were used and conditions were optimized for each

Fast capillary gas chromatography. Comparison of different approaches

Savings in analysis time in capillary GC have always been an important issue for chromatographers since the introduction of capillary columns by Golay in 1958. In laboratories where gas chromatographic techniques are routinely applied as an analytical technique, every reduction of analysis time, without significant loss of resolution, can be translated into a higher sample throughput and hence reduce the laboratory operating costs. In this contribution, three different approaches for obtaining fast GC separations are investigated. First, a narrow-bore column is used under conventional GC operating conditions. Secondly, the same narrow-bore column is used under typical fast GC conditions. Here, a high oven temperature programming rate is used. The third approach uses a recent new development in GC instrumentation: Flash-2D-GC. Here the column is placed inside a metal tube, which is resistively heated. With this system, a temperature programming rate of 100°/s is possible. The results obtained with each of these three approaches are compared with results obtained on a column with conventional dimensions. This comparison takes retention times as well as plate numbers and resolution into consideration

Determination of phenolic derivatives of antipyrine in plasma with HPLC-Tandem MS using ESI and Turbo ion spray as interfaces

Free radical damage plays an important role in biology and medicine, especially in the aging process of human beings. In the field of free radical products, determining the degree of this free radical damage is still a major problem. Several determination methods exist, most of which involve the use of a so-called endogenous marker. One of the disadvantages of endogenous markers is that they are involved in biochemical pathways. An exogenous marker with a well-known metabolic pathway can distinguish between naturally formed metabolites and free radical products. Whereas these radical products are formed only via competitive reactions, their concentration in biological fluids will be low. In this work, antipyrine was used as a potential exogenous marker for oxidative stress. A method to determine antipyrine and its phenolic derivatives in plasma by means of reversed-phase high performance liquid chromatography combined with a mass spectrometer (RP-HPLC-MS) was developed. Electrospray ionization (ESI) and turbo ion spray ionization were used as interfaces between the HPLC and the mass spectrometer. To optimize the ESI measurements and the turbo ion spray measurements, a -column (1 mm I.D.) was used for the LC separation. The mass spectrometer was operated in the multiple reaction mode (MRM). For the different phenolic derivatives of antipyrine, different target ions were used and optimized. A m/z=205/120 (mother/daughter) resulted in the best signal to noise ratio. Using -HPLC instead of conventional HPLC combined with ESI resulted in an increase of the signal to noise ratio by a factor 15. The turbo ion spray interface combined with -HPLC increased this factor by 1.4. The detection limit, determined for antipyrine because no standards for the phenolic derivatives of antipyrine are available, for this method (MS/MS mother/daughter m/z 188.9/104.0) was 1.25 pg in 20-L water