Temperature Programmable Injection Systems

Characteristics of the sample Hot split Hot spMtIess PTV split PTV splitless PTV solvent split On column 

In spite of the many advantages of the cold injection system, in practice there are also limits to its use. These exist both between different cold injection techniques and in comparison with hot injection techniques (Table 2.23). These include the analysis of thermally labile substances. Because of the low injection temperature a cold injection is expected to be particularly suitable for labile substances. However, during the heating phase, the residence times of the substances in the insert are long enough to initiate thermal decomposition. In this case, only on-column injection can be used because it completely avoids external evaporation of the sample for transfer to the column (see Section 2.2.6.3). A test for thermal decomposition was suggested by Donike with the injection of a mixture of the same quantities of fatty acid TMS esters (CIO to C22 thermolabile) and n-alkanes (C12 to C32 thermally stable). If no thermal decomposition takes place, all the substances appear with the same peak intensity. 

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Special attention is required for an inert GC inlet system to achieve a tailing free peak shape and high compound response. For this purpose the PTV injector as a temperature programmable injection system was chosen, with a special liner deactivation using the SurfaSil treatment for high inertness (Thermo Scientific, 2014). 

Upler, A. and Johnson, G.L. (1989) Optimization of Conditions for High Temperature Capillary Gas Chromatography Using a Split-Mode Programmable Temperature Vaporizing Injection System, in... 

Quantitative analysis Quantitative analyses were conducted on a Hewlett Packard 5890 Series II GS-System (Chrompak HP5, 30 m 0.25 pm FID detector) against an external calibration with benzoic acid methyl ester. The column pressure was adjusted to 15 psi, split 75 mL min-1, injected volume 1 pL. Both, the injector and detector temperatures were at 250 °C. The temperature programme consisted of a ramp of 20 °C min1 to 100 °C, 1 °C min- to 104 °C, followed by 20 °C min- to 210 °C. With this programme, the retention times are 2.8, 4.2, 10.7 and 1.2 min for benzyl alcohol, benzyl acetate, benzyl ether and octane, respectively. The total error was determined to be 5%. 

All capsule pipeline systems include a pipe, many capsules, an injection system to inject capsules into the pipe, a pumping system to pump the fluid and capsules through the pipe, an ejection system to eject the capsules from the pipe, an instrumentation system to monitor the flow rate, pressure, temperature, and the passage of capsules at key locations, and an automatic control system that uses programmable logic controllers and an SCADA (Supervisory Control and Data Acquisition). 

Fig. 2.48. Schematic of a thermodesorption (TDS)-temperature programmable cooled injection system (CIS). Legend 1, TDS 2, temperaturised transfer capUlary 3, CIS 4, mass flow controller 5, back-pressure regulator 6, pressure gauge 7, split/splitless valve 8, TDS/CIS spbtflow switch 9, analytical column, connected to MSD. Reproduced by permission of Gerstel GmbH Co. KG, Miilheim a.d. R., Germany.

When GC is being used, possible contamination of the system (injector and column) with nonvolatile polymeric material is the main issue. One option is to allow direct introduction of a polymer-containing sample (solution), but to confine the polymer to a removable part ( hner ) of the injection system. On some injection systems (specifically programmable-temperature vaporizers, or PTVs), a series of injections may be performed before the quantitative analysis of monomer is jeopardized and the liner needs to be replaced. Such an approach may be acceptable if... 

The analytical method comprises a triple quadrupole GC-MS/MS system with liquid autosampler. The gas chromatograph is equipped with a temperature programmable PTV injector for splitless injection. The separation is performed using a 5% phenyl phase column of standard dimensions. After a short dispersive SPE clean-up the acetonitrile extract is directly injected after centrifugation. The Thermo Scientific TraceFinder software with compound database of pesticides was used for method setup and data processing (The Pesticides Compound Database, 2014). 

Special attention in this multicomponent setup is necessary to the GC inlet system. A temperature programmable injector (PTV) is used, offering a cleaning step at an elevated temperature after each extract injection. The choice of liner and deactivation turned out to be critical for the long-term robustness. This is caused by the short sample preparation generating extracts with a high matrix load, as it is shown in Figure 4.107. 

A 5 ml volume of the 0.5 mol 1 solution of BF3 etherate in nitrobenzene is placed in the calorimetric cell under dry nitrogen or argon. The syringe pusher is filled with a sufficient volume of 2.5 mol 1 pyridine solution. Using these values, 0.100-0.200 ml injection steps allow for 5-10 additions. For an isothermal titration calorimeter, the time interval between each injection should be sufficient for the signal to return to the baseline (for a Dewar calorimeter, allowance is made for temperature stabilization after each injection). When the temperature of the system is equilibrated, the data acquisition and the injection programme are started. A preliminary experiment should be carried out to measure the blank value, corresponding to the heat of dilution of pyridine solution in the pure solvent. 

Gas Chromatograph (GC) (for a Fused Silica Column)—k multi-ramp temperature, programmable GC built for capillary column chromatography. It must have a flame ionization detector and a split injection system that will not discriminate over the boiling range of the samples analyzed. 

Gas Chromatographic System, equipped with temperature programmable gas chromatograph suitable for split injections with WCOT column or cool-on-column injector which allows the injection of small (for example, 0.1 pL) samples at the head of the WCOT column or a retention gap. An autosampler is mandatory for the on-column injections. 

For sample introduction in HTGC, split, splitless, on-column injection, or combinations of the latter, the programmable temperature vaporizing (PTV) injector are suitable. Howeveq with the exception of cold on-column injection, none of these introduction systems fulfill the requirements of an adequate HTGC injection device and guarantees reliable results. 

Most chromatographs today are sold with autoinjectors. Such units are capable of injecting samples into the LC from vials on a sample carousel or from microtiter plates. They usually contain sampling loops and a syringe pump for injection volumes from less than I pL to more than 1 mL. Some have controlled-temperature environments that allow for sample storage and for carrying out derivatization reactions prior to injection. Most are programmable to allow for unattended injections into the LC system. 

The FID collector assembly was modified to connect, via Swage-lok fittings, to a small bore (0.027-inch i.d.), heated, programmable, stainless steel transfer tube, manufacured by Chemical Data Systems, Inc., Oxford, Pa. 19363. The GC injection ports, FID detector, and transfer tube were maintained at lOO C for all experiments conducted. The total column effluent from the GC was conducted through the transfer tube to the detector, a Perkin-Elmer model 360 atomic absorption spectrophotometer fitted with a deuterium background corrector and a HGA-2100 graphite furnace atomizer employing a temperature dial control power supply. 

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