Volatile secondary substances

In some instances crop plants were also selected for a higher content of certain types of secondary products. Cultivated apples, pears and other fruits have a better aroma, i.e., contain more volatile secondary substances, and in addition to a higher sugar content are much more attractively colored than their wild progenitors. The pigments (E 5.5.2) and scent volatiles are usually nontoxic for humans, in contrast, for example, to the tanning substances which many of the wild forms of our cultivated fruits contain. 

One difference between these systems and the biological treatment of nonhazardous wastewater is that the exhaust air may contain volatile hazardous substances or intermediate biodegradation products. Therefore, the air must be treated as secondary hazardous wastes by physical, chemical, physico-chemical, or biological methods. Other secondary hazardous wastes may include the biomass of microorganisms that may accumulate volatile hazardous substances or intermediate products of their biodegradation. This hazardous liquid or semisolid waste must be properly treated, incinerated, or disposed. 

Secondary metabolites in plant cell culture are typically stored within the vacuolar compartments of the cells. Small amounts of metabolites are usually excreted into the medium or may appear in the medium due to cell lysis. In some cases, active transport of metabolites adjusts intracellular and extracellular levels in response to cellular conditions. Poor yields of secondary substances released into the medium may be caused by several factors. In those cases where low yield is due to cellularly mediated regulation of the ratio between intracellular and extracellular product concentrations, processes which reduce net medium concentrations such as enzymatic or non-enzymatic degradation, or volatility, should increase net production by depleting the level of the secondary substances in the culture medium. By using the so-called in situ extraction method, the accumulation of a secondary substance inside the cell, in the culture medium, and in the extraction phase should approach an equilibrium, which... 

Both cell culture with a lipophilic extraction phase and with a polar extraction phase have been reported to be helpful for the accumulation and detection of secondary substances [7,8]. Plant cell cultures release lipophilic and volatile substances such as ethylene, ethanol, and acetaldehyde. The addition of a lipophilic phase to the culture medium can be used as a means of accumulating and detecting these substances. Maisch et al. [8] found that the addition of XAD-4 resin to Nicotiana tabacum cultures enhanced the production of phenolic secondary metabolites several times compared to the adsorbent-free control. Kim and Chang [9] reported in situ extraction for enhanced shikonin production by Lithospermum erythrorhizon. When n-hexadecane was added to the cultivation, higher specific shikonin productivity was obtained than that from the cultures of free cells without extraction. They also suggested that n-hexadecane addition at an early stage in calcium alginate immobilized cell cultures was effective for shikonin production. Most of the produced shikonin was dissolved in n-hexadecane, so it would reduce the costs for shikonin separation. 

The volatility of a substance is of particular importance in transfer. The more volatile a substance, the more readily it is likely to transfer to foods if it is present in secondary packaging, compared to less volatile substances. This assumes that the substance can transfer through the primary packaging or other intervening layers (see section below on intervening layers). 

Altshuller, A. P. (1983) Review Natural volatile organic substances and their effect on air quality in the United States. Atmospheric Enviroinment 17, 2131-2165 Altshuller, A. P. (1993) Production of aldehydes as primary emissions and from secondary atmospheric reactions of alkenes and alkanes during the night and early morning hours. Atmospheric Environment 27, 21-31... 

By using these ionic liquids as secondary dispersing agents, universal, water-based pigment pastes can be used for all types of paints and coatings. This will reduce the use of volatile organic substances/solvents in paints and coatings in the future. 

We make no attempt to characterize these chemicals beyond the generalizations that (i) wide ranges of both primary and secondary plant substances act as excitatory stimuli (ii) inhibition of investment behaviors is triggered mainly by secondary substances but sometimes by unfavorable balances of primary nutrients and (iii) because they are relatively non-volatile and effectively compartmentalized, many phytochemicals generating the inhibitory inputs influence insect behavior only during or after the examining phase when direct contact has been established. Readers are referred to Hedin et al. (1974) for analysis of behaviorally active phytochemicals by chemical class. 

Volatile aldehydes and ketones are the most important odour-and taste-active substances. They occur in foods as primary substances, as components of various essential oils and also result from enzymatic and chemical reactions from various precursors as secondary substances. They are often desirable flavour-active components of foods, but in some cases may also carry undesirable odour and taste. Then they serve as indicators of unwanted changes in sensory or nutritional value of foods (such as autoxidation of lipids). 

A big step forward came with the discovery that bombardment of a liquid target surface by abeam of fast atoms caused continuous desorption of ions that were characteristic of the liquid. Where this liquid consisted of a sample substance dissolved in a solvent of low volatility (a matrix), both positive and negative molecular or quasi-molecular ions characteristic of the sample were produced. The process quickly became known by the acronym FAB (fast-atom bombardment) and for its then-fabulous results on substances that had hitherto proved intractable. Later, it was found that a primary incident beam of fast ions could be used instead, and a more generally descriptive term, LSIMS (liquid secondary ion mass spectrometry) has come into use. However, note that purists still regard and refer to both FAB and LSIMS as simply facets of the original SIMS. In practice, any of the acronyms can be used, but FAB and LSIMS are more descriptive when referring to the primary atom or ion beam. 

Pyrolyses of formates, oxalates and mellitates yield CO and C02 (H2, H20 etc.) as the predominant volatile products and metal or oxide as residue. It is sometimes possible to predict the initial compositions from thermodynamic considerations [94], though secondary reactions, perhaps catalyzed by the solids present, may result in a final product mixture that is very different. The complex mixtures of products (hydrocarbons, aldehydes, ketones, acids and acid anhydrides) given [1109] by reactants containing larger organic groupings makes the collection of meaningful kinetic data more difficult, and this is one reason why there are relatively few rate studies available for the decompositions of these substances. 

Note Primary amines yield fluorescent chromatogram zones even before the application of reagent 3. Secondary amines do not yield fluorescent derivatives until they have been treated with reagent 3. Hence, the reagent sequence allows the stepwise detection of primary and secondary amines. Taurine is preferred as the essential component of reagent 3 over the multiplicity of other possibilities because it produces intense fluorescence it is also not very volatile and is readily available. Amides and substances with peptide linkages, eg. hippuric acid, are not detected, neither are secondary amines that are volatile at high temperatures. 

Schematic representation of the experimental setup is shown in Fig 1.1. The electrochemical system is coupled on-line to a Quadrupole Mass Spectrometer (Balzers QMS 311 or QMG 112). Volatile substances diffusing through the PTFE membrane enter into a first chamber where a pressure between 10 1 and 10 2 mbar is maintained by means of a turbomolecular pump. In this chamber most of the gases entering in the MS (mainly solvent molecules) are eliminated, a minor part enters in a second chamber where the analyzer is placed. A second turbo molecular pump evacuates this chamber promptly and the pressure can be controlled by changing the aperture between both chambers. Depending on the type of detector used (see below) pressures in the range 10 4-10 5 mbar, (for Faraday Collector, FC), or 10 7-10 9 mbar (for Secondary Electrton Multiplier, SEM) may be established.

Researchers have found high inhalant use in other countries as well. An estimated 3.5% to 10% of children age 12 and under in the United Kingdom have abused volatile substances and between 0.5% and 1% have become long-term users. In 1999, Australia s National Drug Alcohol Centre secondary school survey of 25,480 students found that 32% of 12-year-old boys and 37% of 12-year-old girls reported that they had used an inhalant at some point. 

High temperature and low reactivity host substances (e.g., polymers) are known to favor secondary decompositions, leading to other active radicals and nonreactive volatiles... 

The term essential oil does not reflect its role in the plant s functioning and metabolism. Plant volatile oils funcbon as secondary metabolites. (A metabolite is a compound produced by the plant s metabolism.) Primary metabolites are the compounds needed for the plant to live and include the food substances produced in photosynthesis. The secondary metabolites vary widely in chemical structure and serve a variety of purposes within the plant. They include protective, survival and reproductive roles. However, they are responsible for giving a plant its aroma and flavour and have significant physiological and psychological effects on animals and people. 

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