Reagents, cleaning procedures

The atomically clean, well-ordered Ni(lOO) surface was obtained by using a standard cleaning procedure as described in detail elsewhere [17]. The deposition of potassium was achieved by evaporation from a SAES getter source [18]. Reagent grade (99.999% purity) gases of O2, H2 and CH4 were introduced into the UHV chambers through leak-valves. 

In the following cleaning procedures, all work should be done in a fume hood, hand and eye protection should be worn, and a lab apron is recommended. After cleaning, an item should be thoroughly rinsed in water followed by a rinse in distilled water. If an item needs to be dried, a final rinse in reagent-grade methanol, ethyl alcohol, or acetone can be used. 

The polystyrene samples were used as received. Examination by XPS showed only carbon on the surface (XPS does not detect hydrogen). The pyrolytic carbon samples were prepared by a "steady state" fluidized bed process (j ). The carbon samples were polished by the manufacturer using 7-alumina. Before use in this study the pyrolytic carbon samples were ultrasonically cleaned in reagent grade methanol for five minutes. Examination by XPS of both the as received and ultrasonic methanol cleaned samples showed removal of small amounts of chlorine, magnesium, silicon, and sulfur by the cleaning procedure. 

Avoiding the use of organic solvents during MAOS of heterocycles lead to a clean, efficient and economical technology (Green Chemistry). Apart from this the safety is increased, workup is considerably simplified, cost is reduced, the use of toxic solvents can be avoided and the reactivities and sometimes the selectivities can also be enhanced without dilution. Due to these positive aspects of solvent free synthesis, there is a marked increase in the use of environmentally benign reagents and procedures. 

This section presents an overview of the cold-trap pre-concentration gas phase detection method for the determination of mercury in seawater. A more thorough and complete discussion of the analytical details (e.g., cleaning procedures, reagent preparation, analytical manipulations) can be found in Fitzgerald et al (21). 

The metallic and Ionic cleaning procedures studied by Kern were evaluated by radiotracer methods. This technique requires the use of radionuclide enriched reagents. Recently, a procedure utilizing secondary Ion mass spectrometry (SIMS) has been developed for studying very low levels of contamination on silicon surfaces (18). 

Leaching with reagent grade nitric acid for 7 days, twice in this and following cleaning procedures all bottles were completely filled ... 

Materials, reagents, apparatus, and their cleaning procedures have been published previously (6,12). All solvent ratios were on a v/v basis. Sediment dry weights were determined on 10-20-g samples (6). 

The sampling and storage containers, and any reagents used for sample preservation, have to be checked for mercury contamination at an appropriate level. Special cleaning procedures, such as washing with hydrochloric or nitric acid, might be necessary. However, storage of samples does not only involve a risk of contamination-, also the possibility of loss of mercury has to be considered (see Aqueous samples section). 

All reagents and solvents must be residue grade or equivalent. Cleaning procedures are described in UNEP (1995). 

All the nucleophilic 1,3-cycloeliminations involved in the formation of the three-membered ring commented so far, needed bases. However, as shown in Reaction scheme 86, this 1,3-elimination also proceeds under electrophiUc conditions, when aluminumtrichloride or just hydrochloric acid in dioxane is the cyclizing reagent for a clean procedure without byproducts [222]. 

Dissolve a known weight (ca 0.5 g) of the steel by any suitable procedure. Treat the acidic sample solution (< 200 /jg Co), containing iron in the iron(II) state, with 10-15 mL of 40 per cent (w/v) sodium citrate solution, dilute to 50-75 mL and adjust the pH to 3-4 (indicator paper) with 2M hydrochloric acid or sodium hydroxide. Cool to room temperature, add 10 mL of 3 per cent (10-volume) hydrogen peroxide and, after 3 minutes, 2mL of the reagent solution. Allow to stand for at least 30 minutes at room temperature. Extract the solution in a separatory funnel by shaking vigorously for 1 minute with 25 mL of chloroform repeat the extraction twice with 10 mL portions of chloroform. Dilute the combined extracts to 50 mL with chloroform and transfer to a clean separatory funnel. Add 20 mL of 2M hydrochloric acid, shake for 1 minute, run the chloroform layer into another separatory funnel, and shake for 1 minute with 20 mL of 2M sodium hydroxide. Determine the absorbance of the clear chloroform phase in a 1 cm cell at 530 nm. 

Alumina supported sodium metaperiodate, which can be prepared by soaking the inorganic support with a hot solution of sodium metaperiodate, was also found to be a very convenient reagent for the selective and clean oxidation of sulphides to sulphoxides79. The oxidation reaction may be simply carried out by vigorous stirring of this solid oxidant with the sulphide solution at room temperature. As may be expected for such a procedure, solvent plays an important role in this oxidation and ethanol (95%) was found to be... 

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