Requirements masking agents

Flavor-Masking Deodorant. In addition to its use as a constituent of perfume compositions, vanillin is also useful as a deodorant to mask the unpleasant odor of many manufactured goods. As a masking agent for numerous types of ill-smelling mass-produced industrial products, particularly those of synthetic mbber, plastics, fiber glass, inks, etc, vanillin finds extensive use. It is often the most inexpensive material for the amount of masking effect it provides. Only traces are required for this purpose as the odor of vanillin is perceptible in dilutions of 2 x 10 mg/m of air. Cmde vanillin is acceptable for such purposes. 

Another major step in many analyses is separation (Chapters 22 to 25). When, because of the method chosen or the nature of the sample, this unit operation is not required, much effort can be saved. For example, if a masking agent will complex an interfering metal ion in an EDTA titration, a separation step may be avoided. Where a separation is essential, a choice among several techniques is usually available. In general, separation involves the formation of two phases, physically separated, one containing the material of interest and the other the interference. Either phase may be a gas, liquid, or solid. Thus six major types of separation processes are possible. Once separation has been effected, the quantitative determination by physical means is often straightforward. 

The determination error is smaller if the absorption of radiation is a consequence of the nature of the analyte itself, as with the coloured ions of transition metals. Conversion of the analyte into a form capable of absorbing radiation in proportion to its concentration requires some additional procedures (such as the use of a chromogenic reagent, pH adjustment, or addition of masking agents), that must be identical in the treatment of standard solutions and of the sample solution. 

In flow analysis, attainment of chemical equilibrium is not necessarily required, and this feature is of paramount importance, as emphasised in Chapter 1. Masking however should be quantitative to improve selectivity. In general, the masking agent is added prior to the main reagent, especially if the rate of the masking reaction is a limiting factor. This means that the... 

When the correction of an odor requires the removal of large gravimetric quantities of parent substances, other methods of separation must usually be employed, although in many cases activated carbon may still fill a need for the removal of residual traces. In this connection it may be of interest to relate an experience in which the roles were reversed A small dose of activated carbon effectively removed a very pungent odor from a fungicide but left a mild unpleasant odor that was subsequently corrected by a masking agent. 

The disadvantage of this reagent is that it is not specific for lead, and preliminary separations may be required. By judicious use of masking agents and proper adjustment of pH prior to solvent extraction of the lead complex, many major interferences can be eliminated. 

The sensor shows selectivity expected for EBT. A four-fold excess of calcium does not interfere with sensor response. Potential interferences from transition metal ions can be eliminated by including masking agents in the buffer required for pH control. 

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