Temperatures autosamplers

Column temperature Autosampler temperature Injection volume... 

Column temperature 22 °C (room temperature) Autosampler temperature 15 °C... 

Sample injection Column temperature Autosampler temperature... 

Inspect the culture tubes in the manifold to determine if there is water in the organic eluent for any sample. If a water layer is present, quantitatively transfer the organic phase into a clean culture tube using a small amount of additional solvent as necessary. Return the culture tube containing the organic extract to its proper location in the manifold rack. Remove the Cig and sodium sulfate mbes, and reinstall the silica tubes on the manifold. With the sample remaining in the culture tube, continue to apply vacuum to the manifold to remove excess solvent. When the solvent volume is < 1 mL, discontinue vacuum, and allow the sample to return to room temperature. Adjust the sample volume in the culture mbe to 1 mL with isooctane-ethyl acetate (9 1, v/v). Transfer the entire sample into an autosampler vial for GC/MS analysis. Sample extracts may be stored for up to 1 month in a refrigerator (< 10 °C) before analysis. 

Column temperature Injection volume Autosampler temperature Flow rate... 

The concept of SPME was first introduced by Belardi and Pawliszyn in 1989. A fiber (usually fused silica) which has been coated on the outside with a suitable polymer sorbent (e.g., polydimethylsiloxane) is dipped into the headspace above the sample or directly into the liquid sample. The pesticides are partitioned from the sample into the sorbent and an equilibrium between the gas or liquid and the sorbent is established. The analytes are thermally desorbed in a GC injector or liquid desorbed in a liquid chromatography (LC) injector. The autosampler has to be specially modified for SPME but otherwise the technique is simple to use, rapid, inexpensive and solvent free. Optimization of the procedure will involve the correct choice of phase, extraction time, ionic strength of the extraction step, temperature and the time and temperature of the desorption step. According to the chemical characteristics of the pesticides determined, the extraction efficiency is often influenced by the sample matrix and pH. 

Chromatographic columns (glass with stopcock and solvent reservoir, 10-mm i.d.) Fused-silica capillary column, DB-1701, 60 m x 0.32-mm i.d., O.lS-qm film thickness (14% cyanopropylphenyl)methylpolysiloxane Varian 3400 gas chromatograph equipped with a temperature-programmed SPI injector, a Varian 8100 autosampler, and a Varian Saturn II lontrap mass spectrometer Centrifuge vials, 10- and 250-mL Evaporation flasks, 100- and 250-mL Separatory funnel, 250-mL... 

Cool on-column >250 pm column (i.d.) 1 ppm (FID) Reduced thermal degradation and discrimination Wide range of analyte concentrations High sample capacity (LVI) Autosamplers Direct quantification Excellent precision Control of operational conditions (initial oven temperature) Optimisation required Not applicable for polar solvents Column contamination by dirty matrices Poor long term stability... 

Stability — Samples remain stable for at least 468 days when frozen at -20°C. They are stable for at least five simulated freeze-and-thaw cycles and approximately 28 hr at room temperature. The analyte is viable for at least 6 days in a reconstitution solution stored in the autosampler (temperature set point at 10°C). A dried-down batch (sample process stopped at dry-down step) was stable at least 5 days in a refrigerator (temperature varied from 4 to 8°C). A stock solution of paricalcitol is stable for at least 11 months. Stock solution of internal standard is stable about 4.5 months under refrigeration. 

Lercanidipine — Kalovidouris et al.57 applied UPLC-MS/MS to the determination of lercani-dipine in human plasma after oral administration of lercanidipine. A Waters Acquity UPLC system with cooling autosampler and column oven was coupled with a Waters BEH C18 column (50 x 2.1 mm, 1.7 jum). The mobile phase was composed of 70% acetonitrile in water containing 0.2% v/v formic acid, delivered at a flow of 0.30 mL/min. The column temperature was maintained at 40°C and sample vials at 5°C. 

In this instrument the sample is first oxidized in a pure oxygen environment. The resulting combustion gases are then controlled to exact conditions of pressure, temperature and volume. Finally the product gases are separated under steady-state conditions and swept by helium or argon into a gas chromatography for analysis of the components. The equipment is supplied with a 60 position autosampler and microprocessor controller... 

Gas chromatographic data was obtained on a Tracor Model 220 gas chromatograph equipped with a Varian Model 8000 autosampler. The analysis column was a 1.7 m "U column, 4 mm id, filled with 3% SP-2250 packing (Supelco, Inc., Bellefonte, PA) held at 200 C. The injection temperature was 250 and the nitrogen carrier gas flow rate was 60 mL/min. The detector temperatures were 350 for electron capture and 190 for flame photometric. Detector signals were processed by a Varian Vista 401 which gave retention times and peak areas. 

It is recommended that OQ test the following on an HPLC system flow accuracy, pump compositional accuracy, pressure pulsations, column oven temperature accuracy/stability, detector noise/drift and wavelength accuracy, autosampler injection precision and carryover. 

A key requirement is that the autosampler needs to be temperature stabilized so that the viscosity of the buffer remains consistent over time. Changes in sample or buffer temperature will directly affect the sample injected along with the migration time. Temperature stabilization can be accomplished in a variety of ways including oven and a peltier cooler. 

The temperature control of the autosampler should be similar to the temperature control of a refrigerator. The unit should be able to maintain a temperature of 5 3°C with accuracy within 0.1°C. 

CE instruments are thermostated to dissipate excessive Joule heat. Generally that covers only the main part of the capillary, and not, e.g., the autosampler with the buffer and sample vials. In some instruments, it is difficult to control the autosampler temperature due to the near presence of extraneous heating sources such as the detector lamp. Also, some labs... 

These liner exchange systems make feasible yet another analysis mode direct thermal desorption (DTD). Here the liner or an insert is packed with the solid sample. The liner exchange system can then be used in place of a conventional autosampler. The liner is automatically inserted into the PTV and the volatiles thermally desorbed onto the column. Some analysts may feel uneasy about such desorption from the solid phase how does one know that all of the volatile analytes have been released from the sample crystal lattice However, where applicable, this approach may not be as difficult to validate as one might imagine. For instance, the PTV can be cooled after the analyte transfer, and then, at the end of the chromatographic temperature programme, reheated to repeat the process. Ideally all of the analyte should transfer in the first cycle and none in the second, demonstrating that complete desorption occurs in the method. 

In commercially available instruments, all vials containing either the sample solution or the solutions employed for separation and for rinsing the capillary between runs are held in an autosampler, which in most instruments can be thermostated at a desired temperature. The autosampler can also be programmed to carry out the collection of separated fractions for micropreparative applications. The operations performed by the autosampler and by the other equipments of the separation unit... 

The injection temperature can be a signiflcant issne for thermally unstable samples or where samples are stored for hours in an antosampler prior to injection. For this reason, most manufacturers sell autosamplers with optional thermostated sample compartments. This can be done either by placing the sample tray in an air bath oven or by a condnctive temperature control of the sample rack. The need to keep samples cool prior to injection when conpled with elevated temperature separation increases the complexity of the flow system reqnired. For such application, a separate mobile phase pre-heater with a low volnme placed between the injector and the column is a good choice. Alternatively, the injector valve wonld need to be monnted ontside the antosampler or in the column oven to insure preheating of the mobile phase before the colnmn. 

A-11 equipped with a model 655-40 autosampler and a UV detector (Hitachi model 655A UV monitor) set at 208 nm. Column temperature was controlled with a Coolnics model CTR-120 device (Komatsu Electronics, Tokyo, Japan). Chromatogram peak areas were integrated with a Hitachi D-2500 chromato-integrator. The column was an Inertsil NH2 (5 p,M, 4.0 x 250 mm)... 

Autosampler The autosampler should have an injector capable of injecting sample volumes from 1 to 100 pL. The injector should have a precision of <1.5% RSD. The injector carryover should be <0.5% of peak area. The autosampler should pick the correct vial. The autosampler should use relays and/or contacts to communicate with the laboratory CDS. Temperature-controlled sample racks should be capable of maintaining samples in the temperature range of 4-15 °C (+3°C). 

As a consequence of the limited stability of the OPA derivatives, the derivatization procedure should be carried out in an intelligent autosampler such as the Gilson 231XL sampler, equipped with a temperature-controlled sample holder (Gilson 832). 

Pipette plasma, urine (both 50 pi), or CSF (200 pi) into an Eppendorf tube. Add 50 pi internal standard. Add twice 250 pi acetonitrile while vortexing. Spin down the protein at 12,000 rpm (12,000 xg) in the refrigerated microcentrifuge for 10 min. Transfer the supernatant to an evaporation vial and blow nitrogen at 37°C until dry. The residue is taken up in 200 pi buffer and vortexed. Check the pH (11). Transfer to another Eppendorf vial, add 20 pi methyl chloroformate, react at ambient temperature for 5 min (check pH > 6). Stop the reaction with 20 pi 6 M HC1 (check pH=l). Centrifuge again at 12,000 rpm (12,000xg) and 4°C for 10 min (two layers will form). The upper layer is transferred to an autosampler vial. 

Remove tubes from the heating block and allow to cool to room temperature. Remove the caps and transfer the contents of each tube to a clean GC-MS autosampler vial. Cap the vials. Samples may be stored in the refrigerator until analysis for up to 24 h. 

We use a GC Top 8000 gas chromatograph coupled with a PolarisQ ion-trap mass spectrometer and equipped with an AI3000S autosampler (Thermofinnigan www. thermo.com). The steroids are separated on a DB-1 crosslinked methyl-silicone column, 15 mx 0.25 mm i.d., film thickness 0.25 pm (J W Scientific marketed by Agilent). Helium is used as a carrier gas at a constant pressure of about 35 kPa. A 1-pl aliquot of the final derivatized extract is injected into the system operated in splitless mode (valve opened at 2 min). The GC temperature program is the same described before for the quadrupole GC-MS system. The injector and transfer lines are kept at 260°C and 280°C, respectively. The ion source temperature is 225°C. A damping gas flow of helium is applied to the ion trap. 

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