|
Ammonium Acetate
Ammonium acetate, also known as spirit of Mindererus in aqueous solution, is a chemical compound with the formula NH4CH3CO2. It is a white, hygroscopic solid and can be derived from the reaction of ammonia and acetic acid. It is available commercially. History The synonym Spirit of Mindererus is named after R. Minderer, a physician from Augsburg. Uses It is the main precursor to acetamide: :NH4CH3CO2 → CH3C(O)NH2 + H2O It is also used as a diuretic. Buffer As the salt of a weak acid and a weak base, ammonium acetate is often used with acetic acid to create a buffer solution. Ammonium acetate is volatile at low pressures. Because of this, it has been used to replace cell buffers that contain non-volatile salts in preparing samples for mass spectrometry. It is also popular as a buffer for mobile phases for HPLC with ELSD and CAD-based detection for this reason. Other volatile salts that have been used for this include ammonium formate. When dissolving ammonium acet ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Deliquescent
Hygroscopy is the phenomenon of attracting and holding water molecules via either absorption (chemistry), absorption or adsorption from the surrounding Natural environment, environment, which is usually at normal or room temperature. If water molecules become suspended among the substance's molecules, adsorbing substances can become physically changed, e.g. changing in volume, boiling point, viscosity or some other physical characteristic or property of the substance. For example, a finely dispersed hygroscopic powder, such as a salt, may become clumpy over time due to collection of moisture from the surrounding environment. ''Deliquescent'' materials are sufficiently hygroscopic that they dissolve in the water they absorb, forming an aqueous solution. Hygroscopy is essential for many plant and animal species' attainment of hydration, nutrition, reproduction and/or seed dispersal. Biological evolution created hygroscopic solutions for water harvesting, filament tensile strength, ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
High-performance Liquid Chromatography
High-performance liquid chromatography (HPLC), formerly referred to as high-pressure liquid chromatography, is a technique in analytical chemistry used to separate, identify, and quantify specific components in mixtures. The mixtures can originate from food, chemicals, pharmaceuticals, biological, environmental and agriculture, etc., which have been dissolved into liquid solutions. It relies on high pressure pumps, which deliver mixtures of various solvents, called the mobile phase, which flows through the system, collecting the sample mixture on the way, delivering it into a cylinder, called the column, filled with solid particles, made of adsorbent material, called the stationary phase. Each component in the sample interacts differently with the adsorbent material, causing different migration rates for each component. These different rates lead to separation as the species flow out of the column into a specific detector such as UV detectors. The output of the detecto ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Ammonium Carbonate
Ammonium carbonate is a chemical compound with the chemical formula . It is an ammonium salt of carbonic acid. It is composed of ammonium cations and carbonate anions . Since ammonium carbonate readily degrades to gaseous ammonia and carbon dioxide upon heating, it is used as a leavening agent and also as smelling salt. It is also known as baker's ammonia and is a predecessor to the more modern leavening agents baking soda and baking powder. It is a component of what was formerly known as sal volatile and salt of hartshorn, and produces a pungent smell when baked. It comes in the form of a white powder or block, with a molar mass of 96.09 g/mol and a density of 1.50 g/cm3. It is a strong electrolyte. Production Ammonium carbonate is produced by combining carbon dioxide and aqueous ammonia. About 80,000 tons/year were produced as of 1997. : An orthorhombic ammonium carbonate monohydrate is known (). It crystallizes in an ammonia solution exposed in a carbon dioxide-rich atmos ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
INS Number
The International Numbering System for Food Additives (INS) is an international naming system for food additives, aimed at providing a short designation of what may be a lengthy actual name."Class Names and the International Numbering System for Food Additives"CAC/GL 36-1989 in 1989, Revision 2008. Last amendment 2011. Published by Codex Alimentarius It is defined by Codex Alimentarius, the international food standards organisation of the World Health Organization (WHO) and Food and Agriculture Organization (FAO) of the United Nations (UN). The information is published in the document ''Class Names and the International Numbering System for Food Additives'', first published in 1989, with revisions in 2008 and 2011. The INS is an open list, "subject to the inclusion of additional additives or removal of existing ones on an ongoing basis". Numbering system INS numbers consist of three or four digits, optionally followed by an alphabetical suffix to further characterize individual ad ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Food Additive
Food additives are substances added to food to preserve flavor or enhance taste, appearance, or other sensory qualities. Some additives, such as vinegar ( pickling), salt ( salting), smoke ( smoking) and sugar ( crystallization), have been used for centuries to preserve food. This allows for longer-lasting foods, such as bacon, sweets, and wines. With the advent of ultra-processed foods in the late 20th century, many additives having both natural and artificial origin were introduced. Food additives also include substances that may be introduced to food indirectly (called "indirect additives") in the manufacturing process through packaging, storage or transport. In Europe and internationally, many additives are designated with E numbers, while in the United States, additives in amounts deemed safe for human consumption are designated as GRAS. Identification To regulate these additives and inform consumers each additive is assigned a unique number called an "E number", whi ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Cation Exchange Capacity
Cation-exchange capacity (CEC) is a measure of how many cations can be retained on soil particle surfaces. Negative charges on the surfaces of soil particles bind positively-charged atoms or molecules (cations), but allow these to exchange with other positively charged particles in the surrounding soil water. This is one of the ways that solid materials in soil alter the chemistry of the soil. CEC affects many aspects of soil chemistry, and is used as a measure of soil fertility, as it indicates the capacity of the soil to retain several nutrients (e.g. K+, NH4+, Ca2+) in plant-available form. It also indicates the capacity to retain pollutant cations (e.g. Pb2+). Definition and principles Cation-exchange capacity is defined as the amount of positive charge that can be exchanged per mass of soil, usually measured in cmolc/kg. Some texts use the older, equivalent units me/100g or meq/100g. CEC is measured in moles of electric charge, so a cation-exchange capacity of 10 cmolc/kg co ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Dialysis (biochemistry)
In chemistry, dialysis is the process of separating molecules in solution by the difference in their rates of diffusion through a semipermeable membrane, such as dialysis tubing. Dialysis is a common laboratory technique that operates on the same principle as medical dialysis. In the context of life science research, the most common application of dialysis is for the removal of unwanted small molecules such as salts, reducing agents, or dyes from larger macromolecules such as proteins, DNA, or polysaccharides. Dialysis is also commonly used for buffer exchange and drug binding studies. The concept of dialysis was introduced in 1861 by the Scottish chemist Thomas Graham. He used this technique to separate sucrose (small molecule) and gum Arabic solutes (large molecule) in aqueous solution. He called the diffusible solutes crystalloids and those that would not pass the membrane colloids. From this concept dialysis can be defined as a spontaneous separation process of suspended ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Organic Synthesis
Organic synthesis is a branch of chemical synthesis concerned with the construction of organic compounds. Organic compounds are molecules consisting of combinations of covalently-linked hydrogen, carbon, oxygen, and nitrogen atoms. Within the general subject of organic synthesis, there are many different types of synthetic routes that can be completed including total synthesis, Enantioselective synthesis, stereoselective synthesis, automated synthesis, and many more. Additionally, in understanding organic synthesis it is necessary to be familiar with the methodology, techniques, and applications of the subject. Total synthesis A total synthesis refers to the complete chemical synthesis of molecules from simple, Precursor (chemistry), natural precursors. Total synthesis is accomplished either via a linear or convergent approach. In a Linear synthesis, ''linear'' synthesis—often adequate for simple structures—several steps are performed sequentially until the molecule is com ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Reductive Amination
Reductive amination (also known as reductive alkylation) is a form of amination that converts a carbonyl group to an amine via an intermediate imine. The carbonyl group is most commonly a ketone or an aldehyde. It is a common method to make amines and is widely used in green chemistry since it can be done catalytically in One-pot synthesis, one-pot under mild conditions. In biochemistry, Dehydrogenase, dehydrogenase enzymes use reductive amination to produce the amino acid Glutamic acid, glutamate. Additionally, there is ongoing research on alternative synthesis mechanisms with various metal catalysts which allow the reaction to be less energy taxing, and require milder reaction conditions. Investigation into biocatalysts, such as imine reductases, have allowed for higher selectivity in the reduction of chiral amines which is an important factor in pharmaceutical synthesis. Reaction process Reductive amination occurs between a carbonyl such as an aldehyde or ketone and an amine i ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Knoevenagel Condensation
In organic chemistry, the Knoevenagel condensation () reaction is a type of chemical reaction named after German chemist Emil Knoevenagel. It is a modification of the aldol condensation. A Knoevenagel condensation is a nucleophilic addition of an active hydrogen compound to a carbonyl group followed by a dehydration reaction in which a molecule of water is eliminated (hence ''condensation''). The product is often an α,β-unsaturated ketone (a conjugated enone). In this reaction the carbonyl group is an aldehyde or a ketone. The catalyst is usually a weakly basic amine. The active hydrogen component has the forms: * or for instance diethyl malonate, Meldrum's acid, ethyl acetoacetate or malonic acid, or cyanoacetic acid. * , for instance nitromethane. where Z is an electron withdrawing group. Z must be powerful enough to facilitate deprotonation to the enolate ion even with a mild base. Using a strong base in this reaction would induce self-condensation of the ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Ammonium Formate
Ammonium formate, NH4HCO2, is the ammonium salt of formic acid. It is a colorless, hygroscopic, crystalline solid. Reductive amination Acetone can be transformed into isopropylamine as follows: :CH3C(O)CH3 + 2 HCO2− +NH4 → (CH3)2CHNHCHO + 2 H2O + NH3 + CO2 :(CH3)2CHNHCHO + H2O → (CH3)2CHNH2 + HCO2H Uses Pure ammonium formate decomposes into formamide and water when heated, and this is its primary use in industry. Formic acid can also be obtained by reacting ammonium formate with a dilute acid, and since ammonium formate is also produced from formic acid, it can serve as a way of storing formic acid. Ammonium formate can also be used in palladium on carbon (Pd/C) reduction of functional groups. In the presence of Pd/C, ammonium formate decomposes to hydrogen, carbon dioxide, and ammonia. This hydrogen gas is adsorbed onto the surface of the palladium metal, where it can react with various functional groups. For example, alkenes can be reduced to alkanes, formaldehyde to me ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Charged Aerosol Detector
The charged aerosol detector (CAD) is a detector used in conjunction with high-performance liquid chromatography (HPLC) and ultra high-performance liquid chromatography (UHPLC) to measure the amount of chemicals in a sample by creating charged aerosol particles which are detected using an electrometer.Gamache P. (2005HPLC analysis of nonvolatile analytes using charged aerosol detectionretrieved September 17, 2015. It is commonly used for the analysis of compounds that cannot be detected using traditional UV/Vis approaches due to their lack of a chromophore. The CAD can measure all non-volatile and many semi-volatile analytes including, but not limited to, antibiotics, excipients, ions, lipids, natural products, biofuels, sugars and surfactants. The CAD, like other aerosol detectors (e.g., evaporative light scattering detectors (ELSD) and condensation nucleation light scattering detectors (CNLSD)), falls under the category of destructive general-purpose detectors (see Chromatography ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
