Stripping, procedure

Many polarographic analysers are available commercially which can be used for the pre-concentration electrolysis step, and will then apply the requisite stripping procedure and produce a recorder chart of the result. In many modem instruments, microprocessor control is incorporated so that the requisite series of operations take place automatically. 

Release of trichloroethylene also occurs at treatment and disposal sites. Water treatment facilities may release trichloroethylene from contaminated water through volatilization and air-stripping procedures (EPA 1985e). Trichloroethylene is also released to the atmosphere through gaseous emissions from landfills. The compound may occur as either an original contaminant or as a result of the decomposition of tetrachloroethylene. Trichloroethylene has also been detected in stack emissions from the incineration of municipal and hazardous waste (James et al. 1985 Oppelt 1987). 

Given the absenee (or near absenee) of Mel in these reaetions, we sought to demonstrate the proeess on a eontinuous proeess. We purposely ehose to employ the same vapor take-off (vapor stripped) reaetor we used in om earher studies of the Rh/Mel co-catalyzed carbonylation of methanol (3) since the vapor stripping procedure used in the process would force any Mel formed in situ overhead where we could detect it in the effluent. This would represent the most rigorous test of the new non-Mel process we could contrive. 

Grob and Zurcher [36,53-55] have carried out very detailed and systematic studies of the closed loop gas stripping procedure and applied it to the determination of parts per billion of 1-chloroalkanes in water. Westerdorf [56] applied the technique to chlorinated organics and aromatic and aliphatic hydrocarbons. 

Grob et al. [220-223] have carried out very detailed and systematic studies of the closed-loop gas stripping procedure and applied it to the determination of xg/l of 1-chloroalkanes in water. Westerdorf [224] applied the technique to chlorinated organics, and aromatic and aliphatic hydrocarbons. Waggot and Reid [225] reported that a factor of major concern in adapting the technique to more polluted samples is the capacity of the carbon filter, which usually contains only 1.5-2 mg carbon. They showed that the absolute capacity of such a filter for a homologous series of 1-chloro-n-alkanes was 6 xg for complete recovery. 

To show the substance distribution in the different skin layers, the allocation of the different removed skin segments, obtained either by a stripping procedure or by cryo-cutting, is essential. 

Selective partitioning of target contaminants can be achieved during stripping procedures. 

Radionuclidic analyses are performed with either a lithium-drifted germanium or intrinsic germanium detector. The assay for Sr-82 is based upon its 777 keV photon of 13.6% abundance. Strontium-85, which is often present in amounts comparable to that of Sr-82, is assayed by its 514 keV photopeak, which must be resolved from prominent 511 keV annihilation radiation by a curve stripping procedure (12). 

Ultrasensitive adsorptive stripping procedures, based on the unique coupling of catalytic and adsorption processes, have been developed recently [33-35]. Such dual amplification strategy results in remarkably low detection limits of 10 12 M. Note, for example, the large (pA) hydrogen catalytic currents observed... 

Table 24.1 Representative Adsorptive Stripping Procedures for Measurements of Trace Metals...

While early ASV schemes were limited to about a dozen amalgam-forming metals, the recent development of adsorptive stripping procedures has greatly expanded the scope of stripping analysis to more than 40 trace metals. 

Alternative stripping procedures using concentrated solutions containing chloride or nitrate ions to displace the vanadate from the loaded solvent, or sulfur dioxide to reduce the vanadium(V) to the oxovanadium(IV) cation have been proposed.210... 

V, using a potential step of 0.0024Y. Modulation time was 0.05 s and interval time of applied pulses was 0.2 s. During the stripping step the current is recorded in quiescent solution. To obtain a calibration curve a known quantity of heavy-metal solution was successively added and the above accumulation and stripping procedures were applied without the removal of the electrodes. All experiments were carried out without the removal of oxygen. 

Despite the simplicity of tape stripping procedure, numerous artifacts may result in inaccurate conclusions following dermatopharmacokinetic studies. The origin of such artifacts as well as possible ways to avoid them are discussed in the following. 

A further bias in determining dermatopharmacokinetics may originate from imprecise repetitive application of the tape on the skin being stripped. The use of a thin template to delimit the skin area is a simple way to keep the tape stripping area constant and unchanged during the entire tape stripping procedure. 

A further factor influencing dermatopharmacokinetics is the duration of tape stripping procedure. Redistribution of the solute in the SC may occur when tape stripping procedure is performed over a long period of time relative to its lag time for diffusion across SC.15 Furthermore, lateral spreading of the solute from neighboring, noninvolved skin into the stripped area may happen under certain circumstances.16... 

As described earlier, the amount of SC removed by tape stripping is highly variable and depends on the way the tape stripping procedure is performed as well as on SC characteristics and conditions. 

Add 2 mL of hexadecane and 2 boiling stones to the 500-mL distillation flask containing the combined isooctane extracts, and attach the flask to a suitable vacuum distillation assembly. Evacuate the assembly to about one-third atmosphere, then immerse the flask in a steam bath, and distill the solvent. When isooctane stops dripping into the receiver, turn off the vacuum, wash down the walls of the flask with 5 mL of isooctane added through the top of the distillation head, then replace the thermometer and again evacuate. The isooctane should distill over in about 1 min. At the end of this distillation, add another 5-mL portion of isooctane, and repeat the stripping procedure. 

More recently, Bommannan et al. [61] used ATR-IR to examine the SC as a function of serial tape stripping. The nonuniform and inhomogeneous nature of the membrane has inevitably led to questions concerning the exact location of the barrier within the SC. With ATR-IR in conjunction with tape stripping, it has been possible to probe, at discrete intervals across the forearm SC in human subjects, spectral features associated with both the intercellular lipids and the hydration level of the membrane, key determinants of skin barrier function. On average, each tape-stripping procedure removed one SC layer per strip and enabled the progressive examination of 50-75% of the SC tissue. 

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