Direct immersion

Electric heaters have also been directly immersed in the molten zone. Zone refining has been accompHshed with a single hehcal heater rotating in an annular sample space (71). 

Two basic methods are used for SPME direct immersion of the fibre into the sample and headspace sampling. Experimental parameters comprise the polarity of the sample matrix and coating material, solvent and salting-out. Other parameters for optimisation of SPME conditions include desorption time, injector port temperature and initial oven temperature. 

In principle, different reference electrodes may be used if the cell is provided with a separate compartment and a Luggin capillary. But if the flow cell technique is to be applied, it is more convenient to avoid the use of capillaries where the solution cannot be easily exchanged. Active bulk components could diffuse through the capillary and give rise to erroneous responses. A small palladium gauze charged with hydrogen directly immersed in the solution can be used as the reference electrode (PdH ) [18]. 

Fig. 9. Direct immersion ultrasonic horn equipped for inert atmosphere work. [Design of K. S. Susiick (183). ...

Since the ultrasonic radiating surface is not in direct contact with the reaction solution, the acoustic intensities are much lower than those of the direct immersion horn, and so homogeneous sonochemistry is often quite sluggish. On the other hand, there is no possibility of contamination from erosion of the titanium horn. 

Figure 2. Direct Immersion Ultrasonic Horn Equipped for Inert Atmosphere Work.

Additional considerations in the design and operation of a remote hydrogen plasma system include the following (1) convective heat transfer between the downstream gas and the specimen can introduce a significant difference between the heater temperature and the specimen surface temperature (this effect is generally not as severe as for direct immersion in... 

The principal feature of the system in Fig. 1 is the exclusion of any effects associated with the direct immersion of the specimen in a plasma, such as might arise from charged-particle bombardment or illumination of the specimen during hydrogenation. 

Essential to the identification of H-induced defects in silicon was the use of a remote hydrogen plasma system as described in Section 1.2. The alternative of direct immersion in a plasma introduces charged-particle bombardment and possible photochemical effects that can obscure the purely chemical consequences of hydrogen migrating into silicon. While the evidence presented below strongly argues for the existence of H-induced defects, many issues remain to be resolved. 

Valproic acid Direct immersion PDMS (100) GC-FID (LOD l mg/mL) Equilibrium dialysis followed SPME Krogh et al., 1995 (7)... 

Aniline, phenols, nitrobenzenes Direct immersion PA (85) GC-MS Protein binding study, determination of free concentrations Vaes et al., 1996 (8)... 

Antidepressants Direct immersion PDMS (100) GC-NPD, GC-MS (LOQ 90-200 ng/mL) Theoretical model for influence of proteins Ulrich and Martens, 1997 (9)... 

Benzodiazepines Direct immersion PA (85) GC-FID (LOQ 0.01-0.48 mmol/mL) 1-Octanol-modified PA fiber, pretreated plasma (TCA) Reubsa et al., 1998 (11)... 

Anesthetics Direct immersion CW-DVB (65) PA (85) PDMS (100) GC-NPD (LOQ 0.5 mmol/mL) Study of protein-binding ultra filtrate plasma Abdel-Rehim et al., 2000 (15)... 

The immersible hydrogen sensor (IHS-12 in Fig. 29) can be used to quantify hydrogen uptake by directly immersing it in the corrosive environment. Hydrogen uptake can also be measured under cathodic protection. 

Recently, DeGrandpre [12] developed a probe-type sensor for the determination of PCO2 in sea water by direct immersion of the probe, which, however, has some connotations of flow-through sensor even though a pH indicator such as Phenol Red (piTj = 7.5) or Bromothymol Blue (pAn = 6.8) rather than the sample is circulated over the sensing microzone —the basic forms of these indicators have a high molar extinction coefficient at 560 and... 

Pomades consist of fats that contain fragrance substances and are produced by the hot or cold enfleurage of flowers. Hot enfleurage is the oldest known procedure for preserving plant fragrance substances. In this method, flowers (or other parts of a plant) are directly immersed in liquid or molten wax. 

---