Masking reagents for

In order to determine S(IV) in rain water, it is necessary to prevent the oxidation of S(IV) between sampling and analysis. The suppressive effect on the oxidation of S(IV) was investigated by the addition of EDTA (Ethylenediaminetetraacetate) or TEA (Triethanolamine) as masking reagents for FeJ+ and Mn. Table III shows the suppressive effect of EDTA or TEA at various pH values. The suppressive effect was not observed between pH 3 and 5, because neither EDTA nor TEA chelate with Fe3+ and Mnz+ at these pH values. EDTA and TEA were found to be very effective for the suppression of the oxidation of S(IV) in solutions having neutral and basic pH values. 

In general, the use of a specific or selective reagent as precipitant for the element is advisable as1 is the use of a masking reagent for interfering elements. In this way a single or double precipitation procedure often becomes sufficient. 

Cu, Zn Serum UV-Vis 0.0—2.5 pg mL-1 Cu + Zn (mixed standard solutions) Sequential determinations/pulsed addition of a masking reagent for copper [21]... 

Poison antidote, complexing agent. Used as masking reagent for metals. Sol. alkalis. 

Sodium diethyldithiocarbamate, (C2H5)2N CS S Na+. This reagent is generally used as a 2 per cent aqueous solution it decomposes rapidly in solutions of low pH. It is an effective extraction reagent for over 20 metals into various organic solvents, such as chloroform, carbon tetrachloride, and ethanol. The selectivity is enhanced by the control of pH and the addition of masking agents. 

For the addition of an organometailic compound to an imine to give a primary amine, R in RCH=NR would have to be H, and such compounds are seldom stable. However, the conversion has been done, for R = aryl, by the use of the masked reagents (ArCH=N)2S02 [prepared from an aldehyde RCHO and sulfamide (NH2)2S02]. Addition of R"MgX or R"Li to these compounds gives ArCHR"NH2 after hydrolysis. ... 

The Stille coupling reaction is very versatile with respect to the functionality that can be carried in both the halide and the tin reagent. Groups such as ester, nitrile, nitro, cyano, and formyl can be present, which permits applications involving masked functionality. For example, when the coupling reaction is applied to l-alkoxy-2-butenylstannanes, the double-bond shift leads to a vinyl ether that can be hydrolyzed to an aldehyde. 

Generally, the selectivity can be improved by optimizing the reaction conditions, that is, by addition of buffers, masking reagents, etc. Nevertheless, many special reagents have been developed for very special applications in the last four decades, mainly by users of photometric methods, who had no or only limited access to modem sophisticated spectrometric methods. 

It is important to maintain low cytotoxicity, since transfection reagent-mediated toxicity could potentially mask the true phenotype of a target gene being studied. This chapter will attempt to describe the use of several cationic lipid/polymer-based transfection reagents for the in vitro delivery of siRNA and DNA. Emphasis will be laid on the key parameters that affect transfection efficacy. 

Foreman et al. [631] compared the direct method of the chelate formation with the preliminary ashing method for the analysis of beryllium in rat urine. A detailed study showed that both of the methods are satisfactory, whereas testing of column material and packings showed the best results for a PTFE column packed with SE-52. Down to 1 ng/ml of the element could be detected in urine with the use of an ECD and EDTA as a masking reagent and a 0.05 M benzene solution of trifluoroacetylacetone. 

The closely related Michaehs Becker reaction also is attendant with difficnlties. There are particnlar problems with solnbUity of the reagents that hinder facile reaction. Some advance in overcoming this type of problem is accomplished in some instances nsing amines as the base, and even Mannich-fype bases for which the base serves not only as the deprotonating agent, but also as a masked substrate for reaction. 

A new synthetic method for steroids has been developed using a butadiene dimer (66) as a building block and the palladium-catalyzed oxidation as the key reaction.3-Acetoxy-l,7-octadiene (66), prepared by the palladium-catalyzed reaction of butadiene with acetic acid, is hydrolyzed and oxidized to l,7-octadien-3-one (67) in high yield. The enone (67) is a very useful reagent for bisanellation because its termiiud double bond can be regarded as a masked ketone which can be readily unmasked by the palladium catalyst to form the l,S-diketone (68) after Michael addition at the enone moiety of (67 Scheme 20). Thus, the enone (67) is the cheapest and most readily available bisanellation reagent, permitting a simple total synthesis of steroids. 

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