WordNet

a substance that exerts some force or effect
a businessman who buys or sells for another in exchange for a commission (同)factor, broker
any agent or representative of a federal agency or bureau (同)federal agent
a representative who acts on behalf of other persons or organizations
an active and efficient cause; capable of producing a certain effect; "their research uncovered new disease agents"
add a buffer (a solution); "buffered saline solution for the eyes"
(chemistry) an ionic compound that resists changes in its pH
(computer science) a part of RAM used for temporary storage of data that is waiting to be sent to a device; used to compensate for differences in the rate of flow of data between components of a computer system (同)buffer storage, buffer store
a cushion-like device that reduces shock due to an impact (同)fender
a power tool used to buff surfaces (同)polisher
how long something has existed; "it was replaced because of its age"
a time of life (usually defined in years) at which some particular qualification or power arises; "she was now of school age"; "tall for his eld" (同)eld
begin to seem older; get older; "The death of his wife caused him to age fast"
make older; "The death of his child aged him tremendously"
of the yellowish-beige color of buff leather
a soft thick undyed leather from the skins of e.g. buffalo or oxen
an implement consisting of soft material mounted on a block; used for polishing (as in manicuring) (同)buffer
bare skin; naked; "swimming in the buff"
polish and make shiny; "buff the wooden floors"; "buff my shoes" (同)burnish, furbish

PrepTutorEJDIC

『代理人』;周旋人 / 働き(作用)を起こすもの;作用物,薬剤 / (政府機関,特にFBI,CIAなどの)部員,機関員
(鉄道車両などの衝突の衝撃を弱める)緩衝器 / 間に立って争いや衝突の働撃を弱める人(物) / 物をみがく人(道具) / …'を'緩和する,和らげる / …'を'緩衝液で処理する
ばかな老人 / やつ
〈U〉(一般に)『年齢』,寿命;〈C〉(個々の)『年齢』,年 / 〈U〉成年(おとなとしての資格・権利を得る年齢;通例18または21歳) / 〈U〉『老齢』;《集合的に》老人たち / 〈U〉(人生の)『一時期』;〈C〉世代(generation) / 〈U〉〈C〉《しばしばA-》(歴史上の)『時代』 / 〈C〉《話》長い間 / 年をとる,ふける;〈物が〉古くなる / 〈年〉'を'とらせる;〈物〉'を'古びさせる
〈U〉もみ皮(牛・水牛などから採った黄褐色の皮;レンズなどをみがくのに用いる) / 〈U〉黄褐色 / 〈U〉(物をみがくのに用いる皮を張った)とぎ革 / 〈U〉《話》《おもに英》素肌(すはだ) / 〈C〉《話》ファン,…狂(fan) / もみ皮製の / 黄褐色の / 〈金属〉'を'もみ皮でみがく

Wikipedia preview

出典(authority):フリー百科事典『ウィキペディア（Wikipedia）』「2015/07/28 09:22:20」(JST)

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[Wiki en表示]

A buffering agent is a weak acid or base used to maintain the acidity (pH) of a solution near a chosen value after the addition of another acid or base. That is, the function of a buffering agent is to prevent a rapid change in pH when acids or bases are added to the solution. Buffering agents have variable properties—some are more soluble than others; some are acidic while others are basic. As pH managers, they are important in many chemical applications, including agriculture, food processing, biochemistry, medicine and photography.

What is a buffering agent?

A buffering agent can be either a weak acid or weak base. Buffering agents are usually added to water to form a buffer solution, which only slightly changes its pH in response to other acids and bases being combined with it, particularly a strong acid or a strong base. Another example is buffered aspirin which has a buffering agent, such as MgO or CaCO₃, that will help maintain the balance between the acid H-A (protonated) and the salt A⁻ (deprotonated) forms of aspirin as it passes through the acidic stomach of the patient. The H-A form of aspirin is a covalent molecule and is more absorbed by the stomach lining, leading to irritation. The antacid properties of these buffering agents help to maintain the balance toward the salt form by reducing the amount of stomach acid (HCl) which protonates the salt form, A⁻.

How a buffering agent works

The way buffering agents work can be seen by calculating how little the pH of buffer solutions will change after addition of a strong acid or a strong base, whereas the same addition would significantly change the pH of a non-buffered solution. Using the Henderson-Hasselbalch equation we get an equilibrium expression between the acid and conjugate base in terms of the log of the ratio of the acid to conjugate base (the salt of the acid). The concentrations of the weak acid and its salt can change significantly, but the log of their ratio will not. The resulting pH of this combination can be found by using Le Chatelier's principle. For a simple numerical example, take the case where the concentrations of the weak acid and its salt are equal. If an added strong base halves the [HA] ([HA] decreases to [HA]-0.5[HA]), then [A⁻] will increase by [A⁻]+0.5[A⁻] since every molecule of HA that is destroyed forms one molecule of [A⁻]. Thus the pH will be raised by a factor of log3 or 0.5 pH units (when the original [HA] and [A⁻] are equal):

Thus, if originally the pK_a = 7 and [HA] = [A⁻], then the pH will be changed from 7.0 to 7.5 after addition of a strong base that halves [HA] and adds a half to [A⁻]. If a similar addition of 0.001 mol NaOH is made to 1L of non-buffered water, the pH would change from 7 to 11.

Examples

Agriculture

Monopotassium phosphate (MKP) is an example of a buffering agent. It has a mildly acidic reaction; when applied as a fertilizer with urea or diammonium phosphate, it minimizes pH fluctuations which can cause nitrogen loss and simultaneously provides potassium nutrient.

Humans

Buffering agents in humans, functioning in acid base homeostasis, are extracellular agents (e.g., bicarbonate, ammonia) as well as intracellular agents (including proteins and phosphate). A dilute mixture of monosodium phosphate and disodium phosphate can be made to approach physiological pH and can serve as an agent for phosphate loading or colonic lavage.

Paper

Calcium carbonate is frequently added to paper to ensure that it resists the effect of acids in the environment and does not prematurely age.

Shampoos and detergents

Most shampoos are buffered so that they are slightly acidic. The buffer counteracts the alkalinity of soap. If either of these substances become too acidic or too alkaline, they could damage fabric, and/or skin and hair.

References

Atkins, Peter; Jones, Loretta (2005). Chemical Principles: The Quest for Insight (Third ed.). New York: Freeman. ISBN 0-7167-5701-X.
Harris, Daniel C. (2003). Quantitative Chemical Analysis (Sixth ed.). New York: Freeman. ISBN 0-7167-4464-3.

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English Journal

Effects of processing on the recovery of food allergens from a model dark chocolate matrix.

Khuda SE1, Jackson LS2, Fu TJ2, Williams KM3.
Food chemistry.Food Chem.2015 Feb 1;168:580-7. doi: 10.1016/j.foodchem.2014.07.084. Epub 2014 Jul 29.
To alleviate the risk to allergic consumers, it is crucial to improve factors affecting the detection of food allergens in processed chocolate products. This study evaluated processing effects on (1) recovery of peanut, egg, and milk allergens using five different extraction buffers, and (2) identif
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Combination of poly(diallyldimethylammonium chloride) and hydroxypropyl-γ-cyclodextrin for high-speed enantioseparation of phenothiazines by capillary electrophoresis.

Yu PL1, Tu YY1, Hsieh MM2.
Talanta.Talanta.2015 Jan;131:330-4. doi: 10.1016/j.talanta.2014.08.015. Epub 2014 Aug 13.
High-speed capillary electrophoresis (CE) enables the simple, rapid, and inexpensive analysis of large sets of chiral samples in the pharmaceutical industry. Hence, we developed a novel method for separating enantiomers of d,L-phenothiazines simply and rapidly, based on using poly(diallyldimethylamm
PMID 25281110

Influence of reducing agents on biosafety and biocompatibility of gold nanoparticles.

Xia DL1, Wang YF, Bao N, He H, Li XD, Chen YP, Gu HY.
Applied biochemistry and biotechnology.Appl Biochem Biotechnol.2014 Dec;174(7):2458-70. doi: 10.1007/s12010-014-1193-7. Epub 2014 Sep 30.
Extensive biomedical applications of nanoparticles are mainly determined by their safety and compatibility in biological systems. The aim of this study was to compare the biosafety and biocompatibility of gold nanoparticles (GNPs) prepared with HEPES buffer, which is popular for cell culture, and so
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Japanese Journal

Chemical alteration by tooth bleaching of human salivary proteins that infiltrated subsurface enamel lesions —Experimental study with bovine lesion model systems—

IIZUKA Junko,MUKAI Yoshiharu,TANIGUCHI Motoe,MIKUNI-TAKAGAKI Yuko,TEN CATE Jacob Martien,TERANAKA Toshio
Dental Materials Journal 33(5), 663-668, 2014
… Bound proteins to the experimental and untreated control specimens were eluted in a stepwise manner with phosphatebuffered saline, 0.4 M phosphate buffer, and 1 M HCl. … In-office bleaching agent may be useful in treating enamel lesions for removing proteins bound to these lesions. …
NAID 130004696767

Encapsulation of Iron Oxide Nanoparticles into Red Blood Cells as a Potential Contrast Agent for Magnetic Particle Imaging

TAKEUCHI Yuki,SUZUKI Hiroya,SASAHARA Hisato,UEDA Junpei,YABATA Isamu,ITAGAKI Kouji,SAITO Shigeyoshi,MURASE Kenya
Advanced Biomedical Engineering 3(0), 37-43, 2014
… When magnetic nanoparticles (MNPs) are used as a contrast agent for magnetic particle imaging (MPI), they are rapidly excreted during systemic circulation by the reticuloendothelial system such as Kupffer cells in the liver. … MNPs were encapsulated into RBCs by the hypotonic dialysis method using a hypotonic buffer solution at three different osmotic pressures. …
NAID 130004568028

Dynamic Coating Capillary Electrophoresis for Separation of Humic Acid Using Mixture Solution of Non-ionic Polymers both as Coating Agent and Separation Medium

TAKAHASHI Toru,KAWANA Jun,TAMURA Yuuki,HOSHINO Hitoshi
Analytical Sciences 29, 1099-1102, 2013-11
… An aqueous solution containing hydroxyethyl cellulose (HEC), polyethylene glycol (PEG), andpH buffer component was employed for both the dynamic coating agent and the separation medium. …
NAID 120005496885