Fast Capillary Gas Chromatography Research Articles

Fast gas chromatography with solid phase extraction clean-up for ultratrace analysis of pesticide residues in baby food

A sample preparation method based on single solvent phase extraction and solid-phase extraction (SPE-NH 2) clean-up is studied in combination with fast capillary gas chromatography (GC) to determine 18 selected pesticides belonging to various chemical classes in apples, the common raw material for baby food production and baby food, at the concentration level ≤10 μg/kg maximum residual limit (MRL). Possibilities of mass spectrometry (MS) detector and electron capture detector (ECD) in fast gas chromatography (GC) of samples with complex matrice at ultra trace levels of pesticide residues were studied and compared. MS detection in single ion monitoring (SIM) mode provided higher selectivity compared to ECD. Optimisation of extraction as well as the simplifying of the whole process of sample preparation was carried out. Recoveries obtained at concentration level of 5 μg/kg (the required value for limit of quantification (LOQ) in baby food) were >90%, except of dimethoate (77.7%) and captan (46.4%) with MS detection. The obtained LOQs were at least 1 order lower than 5 μg/kg for the majority of compounds. The repeatability of gas chromatography–mass spectrometry (GC–MS) measurements of the matrix matched standards expressed as relative standard deviation was <11% except of captan and cypermethrin.

Optimization of Conditions for PTV Large-Volume Injection Combined with Fast GC-MS

Large-volume injection utilizing programmable temperature vaporizer in solvent vent mode is combined with fast capillary gas chromatography and mass spectrometric detection. Optimized injection and chromatographic conditions made possible manual injection of a 20-microL ethyl acetate extract containing 15 organochlorine pesticides and their separation on a short, 0.1-mm-i.d. column in less than 8 min.

Determination of perfume oil in household products by headspace solid-phase microextraction and fast capillary gas chromatography

Headspace solid-phase microextraction (HS-SPME) has been successfully applied to the determination of perfume components in scented candle wax, liquid laundry detergent, and fabric softener. Different fiber coatings (100 μm polydimethylsiloxane, 50/30 μm divinylbenzene/Carboxen/polydimethylsiloxane, 70 μm Carbowax/divinylbenzene, and 85 μm polyacrylate) were tested and the extraction conditions were optimized. For most compounds extraction efficiency, reproducibility, and long-term stability were highest for polydimethylsiloxane. The compatibility of SPME with fast gas chromatographic separation was investigated. The speed of conventional gas chromatography was increased by a factor of 2.5, without loss of separation efficiency, simply by reducing the column length and inner diameter and adjusting the separation conditions by use of method translation software. It was demonstrated that SPME is a suitable sample-introduction technique for fast GC if split injection is used.

Design considerations for rapid‐heating columns applied in fast capillary gas chromatography

AbstractNumerical calculation procedures are developed to predict the optimum experimental conditions for rapid‐programming fast capillary gas chromatography (GC). Retention times and peak widths are calculated from experimentally determined thermodynamic compound properties. Errors in the predicted values are below 2 and 15% for the retention times and peak widths, respectively. It is shown that rapid temperature programming is a powerful tool for speeding up the separation of samples containing homologous series of compounds such as, e.g., triglycerides. The optimal programming rate and the minimum required column length to obtain the shortest possible analysis time with sufficient resolution (Rs=1.5) are predicted. Using a wide‐bore column with a length of 10 m, a programming rate of 4°C/s and a carrier gas velocity of approximately 250 cm/s, the shortest possible analysis time for a triglycerides sample can be obtained while still maintaining sufficient resolution. With these instrumental settings the analysis time of a triglycerides separation can be reduced from 15 to approximately 5 minutes. © 2001 John Wiley &amp; Sons, Inc. J Micro Sep 13: 337–345, 2001

Theory of Fast Capillary Gas Chromatography Part 4: Column Performancevs.Liquid Film Thickness

Theory of Fast Capillary Gas Chromatography Part 4: Column Performancevs.Liquid Film Thickness

Aircraft Measurements of Nitrogen Dioxide and Peroxyacyl Nitrates Using Luminol Chemiluminescence with Fast Capillary Gas Chromatography

Fast capillary gas chromatography with luminol detection has been used to make airborne measurements of nitrogen dioxide (NO2) and peroxyacetyl nitrate (PAN). The analysis system allows for the simultaneous measurement of NO2 and peroxyacyl nitrates (PANs) with time resolution of less than 1 min, an improvement of a factor of 4−5 over previously reported methods using electron capture detection. Data presented were taken near Pasco, Washington, in August 1997, during a test flight onboard the U.S. Department of Energy G-1 aircraft. We report measurements of NO2 in the boundary layer in a paper mill plume and a plume from a grass fire, in addition to analyses for free tropospheric NO2 and PAN. Ratios of PAN/NO2 were observed to increase with altitude (decreasing temperature) and to reach values of 2−4 above the boundary layer, consistent with the thermal equilibrium of the peroxyacetyl radical and NO2 with PAN. Estimates for the peroxyacetyl radical in the continental free troposphere, calculated from this equilibrium, were found to be in the range of 104−105 molecules per cubic centimeter. These results demonstrate the application of this approach for airborne measurements of NO2 and PAN in a wide range of field study scenarios.

Theory of Fast Capillary Gas Chromatography – Part 3: Column Performance vs. Gas Flow Rate

At the high pressure drop required for the fast analysis of complex mixtures, the equations for the column plate height, H, and plate duration, Q, as functions of the carrier gas velocity, u, differ substantially from the equations for the same quantities expressed via the carrier gas flow rate, F. While u as an independent pneumatic variable is more convenient for the theoretical studies, F is a more convenient as a control parameter in practical applications. Equations for H vs. u and for Q vs. u from Parts 1 and 2 are transformed here into expressions for H vs. F and Q vs. F. An efficiency-optimized flow rate (EOF) and a speed-optimized flow rate (SOF) are found. Expressions for these two quantities are considerably simpler than their velocity-based counterparts. In particular, SOF does not depend on column length, film thickness, and pressure drop.

Theory of Fast Capillary Gas Chromatography - Part 3: Column Performancevs. Gas Flow Rate

At the high pressure drop required for the fast analysis of complex mixtures, the equations for the column plate height, H, and plate duration, Q, as functions of the carrier gas velocity, u, differ substantially from the equations for the same quantities expressed via the carrier gas flow rate, F. While u as an independent pneumatic variable is more convenient for the theoretical studies, F is a more convenient as a control parameter in practical applications. Equations for Hvs.u and for Q vs.u from Parts 1 and 2 are transformed here into expressions for H vs. F and Q vs. F. An efficiency-optimized flow rate (EOF) and a speed-optimized flow rate (SOF) are found. Expressions for these two quantities are considerably simpler than their velocity-based counterparts. In particular, SOF does not depend on column length, film thickness, and pressure drop.

Examination of aroma production kinetics of different commercial wine yeasts in fermenting muscat ottonel wines with the help of spme head-space sampling and fast gc analysis

Solid phase microextraction (SPME) coupled to fast capillary gas chromatography was used for monitoring the wine fermentation process. This combination offers a simple, quick and sensitive approach suitable for characterization of head-space components of wines during the fermentation process without a complicated sample preparation procedure. In this work this method was used to observe the differences in aroma production between three different commercial yeasts and the indigenous yeast flora.

The Influence of Liner Dimensions on Injector Band Broadening in Split Injections in Fast Capillary Gas Chromatography

The Influence of Liner Dimensions on Injector Band Broadening in Split Injections in Fast Capillary Gas Chromatography

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.

Theory of fast capillary gas chromatography part. 2: Speed of analysis

AbstractUsing hold‐up time as a measure of the speed of analysis with a given column efficiency, a theory of pneumatic optimization of a column in the fast high pressure drop isothermal and temperature programmed GC is developed. Expression for the hold‐up time as a function of column efficiency, carrier gas velocity and film thickness is derived. Also found are the expressions for the minimum hold‐up time and optimum gas velocity in a speed‐optimized column. These quantities are compared with their counterparts in the efficiency‐optimized column.

Theory of fast capillary gas chromatography. Part 1: Column efficiency

AbstractTypically, fast GC requires high column pressure drop. Under that condition, known relations do not provide a complete description of dependence of [apparent] plate height, ĥ, on average velocity, u, of carrier gas.A complete descriptions for ĥ vs. u is derived and analyzed. It is shown that, under the high pressure drop, ĥ = B/u2 + C1 u2 + C2 u. This is substantially different from the Van Deemter equation ĥ = B/u + Cu for the low pressure drop. Analytical expressions for the minimum plate height and for the respective optimum u under the high pressure drop are derived and analyzed.

Novel Column Heater for Fast Capillary Gas Chromatography

In this paper, we present two designs for the implementation of extremely fast temperature programming of gas chromatographic columns. Both designs incorporate heating and temperaturesensing elements placed along the column. Resistive heating controls the column temperature via a feedback circuit and a software-selected temperature program. Linear temperature increases up to 10°C/s are obtained. The performance of each design is evaluated for applications to volatile and semi-volatile hydrocarbons. Retention times deviate only slightly in comparison with a standard commercial instrument, and peak widths increase for compounds beyond C 13 . The proposed column heater designs have satisfactory retention time reproducibility. They are lightweight and consume little power, making them promising alternatives for fast portable gas chromatography.