Capillary columns temperature

Chromatography Hewlett-Packard Ultra2 (25 m x 0.33 mm) cross-linked phenyl methyl silicone fused silica capillary column. Temperature program 55° (1 min.) -I- 30°C/min. to 180°C, and 4°C/min. to 320°C. 

Gasoline analyses were performed by gas chromatography using a 50 m dimethyl silicon capillary column temperature programmed to 280°C. 

Figure 3. Total ion chromatogram of extractable organics in a typical lot of Ambersorb XE-340 resin (SP-2100,10-m capillary column, temperature program 50(2)-250 at 5 °C/min, 1.0-pL splitless injection). 1, naphthalene 2,1- or 2-methylnaphthalene 3, biphenyl 4, 1,V-biphenyl, 2- or 3-methyl 5, fluorene 6, anthracene-phenanthrene 7tl- or 2-phenylnaphthalene 8, pyrene 9, fluoranthene 10, terphenyl isomer 11, benzo[b]naphthothiophene isomer 12, binaphthalene isomer 13, benzofluoranthene isomer. (Reproduced from...

Pyrolysis GC-MS Analysis. Flash pyrolysis was performed by using a pyroprobe 100 (Chemical Data Systems) temperature-control system. Samples were pyrolyzed from 150 to 750 °C with a temperature program of 20 °C/ms and a final hold for 20 s. After pyrolysis, the fragments were separated on a 25-m CP WAX 57 fused silica capillary column (temperature program 25-220 °C at 3 °C/min), followed by MS on a R 10-10 C (Ribermag, Rueil-Malmaison, France) operated at 70 eV and scanned from 20 to 400 m/z. 

When capillary column temperature is raised, as will be necessary in the determination of enthalpies and entropies of probe/polymer interactions, the retention times of the probes will increase. This might seem odd since it is normal to expect an increase in temperature to result in a decrease in retention time. This behavior is due to the gas viscosity. When the temperature of a gas is increased, its viscosity is also increased (as opposed to liquids where the opposite is true). In a system having a constant pressure drop (as with open tubular columns), an increase in the viscosity results in a simultaneous decrease in the velocity of the carrier gas as shown in the following relationship ... 

Samples (1 pi) of standards 1 and 2 and the soil extract were injected onto a 25 m WCOT BP5 capillary column temperature programmed 50-260°C at 15°C min , helium flow-rate 1 ml min , ECD, autoinjector with a precision of better than 99.4% (Table 10.16). 

Gas-liquid chromatography (GLC), or gas chromatography (GC), was first developed by lipid analysts. From its beginning more than 60 years ago, the instrumentation has become more sophisticated and accurate with the development of new detectors, capillary columns, temperature and pressure programming, etc. Many reviews and books detail these developments. Among the more comprehensive ones are the several books published by Dr. William W. Christie and his regularly updated website Lipid Library, whose... 

With capillary columns, temperature gradients have been demonstrated to be highly useful for larger molecules (Figure 3.13). 

Figure 3 Gas chromatography-mass spectrometric reconstructed ion chromatogram (RIC) of a typical crude oil. A RIC is equivalent to a GC flame ionization detection trace. The presence of triterpanes and steranes eluting between /j-C and n-C i are not evident due to low abundance and interference of coeluting compounds. Conditions Finnigan (San Jose, CA), 9610 gas chromatograph, Supelco (Bellefonte, PA), 30 m X 0.25 mm ID (0.1- Xm film thickness) DB-1 fused silica capillary column, temperature programmed from 120 to 310°C at 8°C/min, 1-pl injection at 50 1 split. Mass spectrometer Finnigan TSQ-46B, 70-eV electron ionization, full-scan mode from 35 to 500 Da in 1 sec cycle time.

The column is swept continuously by a carrier gas such as helium, hydrogen, nitrogen or argon. The sample is injected into the head of the column where it is vaporized and picked up by the carrier gas. In packed columns, the injected volume is on the order of a microliter, whereas in a capillary column a flow divider (split) is installed at the head of the column and only a tiny fraction of the volume injected, about one per cent, is carried into the column. The different components migrate through the length of the column by a continuous succession of equilibria between the stationary and mobile phases. The components are held up by their attraction for the stationary phase and their vaporization temperatures. 

An important problem with all liquid stationary phases is their tendency to bleed from the column. The temperature limits listed in Table 12.2 are those that minimize the loss of stationary phase. When operated above these limits, a column s useful lifetime is significantly shortened. Capillary columns with bonded or... 

It is clear that the separation ratio is simply the ratio of the distribution coefficients of the two solutes, which only depend on the operating temperature and the nature of the two phases. More importantly, they are independent of the mobile phase flow rate and the phase ratio of the column. This means, for example, that the same separation ratios will be obtained for two solutes chromatographed on either a packed column or a capillary column, providing the temperature is the same and the same phase system is employed. This does, however, assume that there are no exclusion effects from the support or stationary phase. If the support or stationary phase is porous, as, for example, silica gel or silica gel based materials, and a pair of solutes differ in size, then the stationary phase available to one solute may not be available to the other. In which case, unless both stationary phases have exactly the same pore distribution, if separated on another column, the separation ratios may not be the same, even if the same phase system and temperature are employed. This will become more evident when the measurement of dead volume is discussed and the importance of pore distribution is considered. 

The thermal sweeper is a commercial product licensed to Zoex Corporation, Lincoln, NA, USA (16). The sweeper incorporates a slotted heater (operated at about 100 °C above the oven temperature) which passes over the capillary column (normally an intermediate thicker film column is used in this region as an accumulator zone). Eigure 4.3 is a schematic diagram of how the instrumental arrangement may be considered. The greater temperature of the rotating sweeper forces the solute which has been retained in the phase in the accumulator section to be volatilized out of the phase into the carrier gas stream, and then bunched up and brought forward... 

For routine separations, there are about a dozen useful phases for capillary columns. The best general-purpose columns are the dimethylpolysiloxane (DB-1 or equivalent) and the 5% phenyl, 95% dimethylpolysiloxane (DB-5 or equivalent). These relatively nonpolar columns are recommended because they provide adequate resolution and are less prone to bleed than the more polar phases. If a DB-1, DB-5, or equivalent capillary column does not give the necessary resolution, try a more polar phase such as DB-23, CP-Sil88, or Carbowax 20M, providing the maximum operating temperature of the column is high enough for the sample of interest. See Appendix 3 for fused silica capillary columns from various suppliers. 

As with capillary columns, it is crucial to have an inactive surface and maintain a reasonably even temperature over the length of the interface. This is usually accomplished by using only glass in the interface. The additional connections necessary in an enrichment-type interface present new areas for leaks to occur. Connections are especially prone to develop leaks after a cooling/heating cycle. 

The maximum column temperatures used in GC/MS are usually 25-50° lower than those used in capillary GC with a flame ionization detector. Higher temperatures can be used in GC/MS but there will be more column bleed, which will require more frequent cleaning of the ion source of the mass spectrometer. 

The purity of 1 and 2 is assessed by analytical gas-liquid chromatography (GC) on a Hewlett-Packard 5890 gas chromatograph equipped with a flame-ionization detector and fitted with a 50 m x 0.2 mm HP-5 fused silica glass capillary column using linear temperature programming from an initial temperature of 150°C for 5 min to a final temperature of 200°C for 10 min at a rate of 5°C/min. 

The use of a fused silica capillary column for the GC analysis of the neutral oil extract has provided the means for improving the resolution of components in a more inert system. The sultones are determined by temperature-programmed GC over CP-Sil-5 CB (methyl silicone fluid) in a 25 m x 0.2 mm fused silica capillary column using nonadecane as internal standard. A sample split ratio of 1 100 is recommended for a 3-pl injection. 

The combination of chromatography and mass spectrometry (MS) is a subject that has attracted much interest over the last forty years or so. The combination of gas chromatography (GC) with mass spectrometry (GC-MS) was first reported in 1958 and made available commercially in 1967. Since then, it has become increasingly utilized and is probably the most widely used hyphenated or tandem technique, as such combinations are often known. The acceptance of GC-MS as a routine technique has in no small part been due to the fact that interfaces have been available for both packed and capillary columns which allow the vast majority of compounds amenable to separation by gas chromatography to be transferred efficiently to the mass spectrometer. Compounds amenable to analysis by GC need to be both volatile, at the temperatures used to achieve separation, and thermally stable, i.e. the same requirements needed to produce mass spectra from an analyte using either electron (El) or chemical ionization (Cl) (see Chapter 3). In simple terms, therefore, virtually all compounds that pass through a GC column can be ionized and the full analytical capabilities of the mass spectrometer utilized. 

Ethylene hydrogenation was carried out in a once-through flow reactor. The effluent gas mixture was analyzed with an online gas chromatograph (Hewlett-Packard HP 6890) equipped with an AI2O3 capillary column and a flame ionization detector. Testing conditions included Phydrogen = 200 Torr, Pethyiene = 40 Torr, catalyst mass of 10 to 20 mg and temperature varied from -50 to -25°C. 

The catalytic degradation of PS was carried out in a semi-batch reactor where nitrogen is continuously passed with a flow rate of 30 mL/min. A mixture of 3.0 g of PS and 0.3 g of the catalyst was loaded inside a Pyrex vessel of 30 mL and heated at a rate of 30 C/min up to the desired temperature. The distillate from the reactor was collected in a cold trap(-10 °C) over a period of 2 h. The degradation of the plastic gave off gases, liquids and residues. The residue means the carbonaceous compounds remaining in the reactor and deposited on the wall of the reactor. The condensed liquid samples were analyzed by a GC (HP6890) with a capillary column (HP-IMS). 

The catalytic reforming of CH4 by CO2 was carried out in a conventional fixed bed reactor system. Flow rates of reactants were controlled by mass flow controllers [Bronkhorst HI-TEC Co.]. The reactor, with an inner diameter of 0.007 m, was heated in an electric furnace. The reaction temperatoe was controlled by a PID temperature controller and was monitored by a separated thermocouple placed in the catalyst bed. The effluent gases were analyzed by an online GC [Hewlett Packard Co., HP-6890 Series II] equipped with a thermal conductivity detector (TCD) and carbosphere column (0.0032 m O.D. and 2.5 m length, 80/100 meshes), and identified by a GC/MS [Hewlett Packard Co., 5890/5971] equipped with an HP-1 capillary column (0.0002 m O.D. and 50 m length). 

The cracking of diphenylmethane (DPM) was carried out in a continuous-flow tubular reactor. The liquid feed contained 29.5 wt.% of DPM (Fluka, >99%), 70% of n-dodecane (Aldrich, >99% solvent) and 0.5% of benzothiophene (Aldrich, 95% source of H2S, to keep the catalyst sulfided during the reaction). The temperature was 673 K and the total pressure 50 bar. The liquid feed flow rate was 16.5 ml.h and the H2 flow rate 24 l.h (STP). The catalytic bed consisted of 1.0 g of catalyst diluted with enough carborundum (Prolabo, 0.34 mm) to reach a final volume of 4 cm. The effluent of the reactor was condensed at high pressure. Liquid samples were taken at regular intervals and analyzed by gas chromatography, using an Intersmat IGC 120 FL, equipped with a flame ionization detector and a capillary column (Alltech CP-Sil-SCB). 

The samples of the reaction mixtures were periodically withdrawn from the reactor and analyzed by GC. The GC analysis was performed using a 100 m Petrocol DH 0.25 mm capillary column with a 0.5 pm coating at the oven temperature of 333 K and the carrier gas (He) ressure of 280 kPa. Injector and FID temperature is 493 K. -Octane is used as the internal standard. 

Early work relied on the use of packed columns, but all modern GC analyses are accomplished using capillary columns with their higher theoretical plate counts and resolution and improved sensitivity. Although a variety of analytical columns have been employed for the GC of triazine compounds, the columns most often used are fused-silica capillary columns coated with 5% phenyl-95% methylpolysiloxane. These nonpolar columns in conjunction with the appropriate temperature and pressure programming and pressure pulse spiking techniques provide excellent separation and sensitivity for the triazine compounds. Typically, columns of 30 m x 0.25-mm i.d. and 0.25-qm film thickness are used of which numerous versions are commercially available (e.g., DB-5, HP-5, SP-5, CP-Sil 8 CB, etc.). Of course, the column selected must be considered in conjunction with the overall design and goals of the particular study. 

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