Phase soaking, injection

Sample is injected at a temperature below the solvent boiling point. If the retention gap can be wetted by the solvent, a flooded zone is formed. The solvent film evaporates from the rear to the front and volatile anal3 tes are reconcentrated by the solvent trapping effect. In addition, phase soaking effects reconcentration of the analytes due to the increased retention power of the thicker stationary phase. Less volatile components remain spread over the retention gap and are reconcentrated by the phase-ratio-focusing effect. 

Sample is injected into the GC under conditions that cause the major part of the solvent to evaporate while the remaining solvent floods the retention gap that is, the solvent introduction rate is higher than the evaporation rate. In this way. about 90% of the introduced solvent can be evaporated during introduction. Volatile analytes are reconcentrated due to phase soaking and solvent trapping in the remaining solvent film. Less volatile components remain spread over the retention gap and are reconcentrated by the phase-ratio-focusing effect. 

Eig. 2. Cychc steam stimulation of an oil well (a) steam, injected into a well over a period of days or weeks in a heavy oil reservoir, introduces heat (huff) that, coupled with (b), alternate soak periods lasting a few days to allow (c) a production phase of weeks or months (puff), thins the oil. This process may... 

Insertion/introduction of the needle into the GC port, depression of the plunger, and thermal desorption of the analytes. Alternatively, the analytes are washed out of the fiber by the HPLC mobile phase via a modified HPLC six-port injection valve and a desorption chamber that replaces the injection loop in the HPLC system. The SPME fiber is introduced into the desorption chamber, under ambient pressure, when the injection valve is in the load position. The SPME-HPLC interface enables mobile phase to contact the SPME fiber, remove the adsorbed analytes, and deliver them to the separation column. Analytes can be removed via a stream of mobile phase (dynamic desorption) or, when the analytes are more strongly adsorbed to the fiber, the fiber can be soaked in mobile phase or another stronger solvent for a specific period of time (e.g., 1 min) before the material is injected onto the column (static desorption) (Fig. 6). 

Fig. 14. Schematic representation of Grass Creek COt well treatment for (a) injection, (b) soak and (c) production phases, depicting how the updip waterflood water injector pushed the CO2 into the waterleg during the soak period, resulting in a delay in the increased calcium concentration (see Fig. 4c) and in the production of the injected CO, during the production phase.

Sample preparation 3 mL Plasma 30 p,L 10 p,g/mL triazolam in water, mix 1 min, allow to stand for 15 min at room temperature, add to 3 mL Extrelut SPE cartridge and allow to soak in for 10 min, elute with 20 mL dichloromethane. Evaporate eluant at 30° under reduced pressure, take up residue in 1 mL MeCN water 5 95, stand for 15 min, centrifuge at 14000 g for 2 min, remove supernatant. Iiyect a 250 p,L aliquot of the supernatant onto column A with mobile phase A and elute to waste. After 7 min forward flush the contents of column A onto column B with mobile phase B. After 0.47 min remove column A from the circuit and elute column B with mobile phase B, monitor the effluent from column B. When not in use, flush column A with mobile phase A. Between iiyections clean column A with two injections of 250 p.L MeCN. 

Sample preparation Condition a 100 mg 1 mL Bond-Elut C2 SPE cartridge with 1 mL MeOH, 1 mL water, and 1 mL pH 9.0 borate buffer. Centrifuge a cotton roll soaked with saliva at 1000 g for 5 min, remove the liquid supernatant. 1 mL Supernatant + 50 xL 100 pg/mL tertatolol, add to the SPE cartridge, wash with 500 pL water, wash with 500 pL MeCN, elute with two 500 pL portions of acidified MeOH. Evaporate the eluate to dryness under a stream of nitrogen at 60°, reconstitute the residue in 50 pL mobile phase, mix for 15 s, inject a 40 pL aliquot. (Acidified MeOH was 50 mL MeOH -t 300 pL 96% acetic acid.)... 

There are six major chemical cleaning methods circulation, fill and soak, cascade, foam, vapor-phase organic, and steam-injected cleaning. 

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