Quenching solution

Fig. 10.5. TTT diagram for the precipitation of CuAh from the Al + 4 wt% Cu solid solution. Note that the equilibrium solubility of Cu in Al at room temperature is only 0.1 wt% (see Fig. 10.3). The quenched solution is therefore carrying 4/0.1 = 40 times as much Cu as it wants to.

Another case to which we can apply the principle of microscopic reversibility is the isomerization of cis- and rrans-(H20)4CrClJ and the loss of Cl- from each. This system has been studied both by careful chromatographic separation of the components20 in quenched solutions and by simultaneous multiwavelength spec-trophotometric determinations.21 The scheme is as follows, where the subscript c indicates cis, t trans, and m the monochloro complex ... 

The reduction of Co(lll) by Fe(II) in perchloric acid solution proceeds at a rate which is just accessible to conventional spectrophotometric measurements. At 2 °C in 1 M acid with [Co(IlI)] = [Fe(II)] 5 x 10 M the half-life is of the order of 4 sec. Kinetic data were obtained by sampling the reactant solution for unreacted Fe(Il) at various times. To achieve this, aliquots of the reaction mixture were run into a quenching solution made up of ammoniacal 2,2 -bipyridine, and the absorbance of the Fe(bipy)3 complex measured at 522 m/i. Absorbancies of Fe(III) and Co(lll) hydroxides and Co(bipy)3 are negligible at this wavelength. With the reactant concentrations equal, plots of l/[Fe(Il)] versus time are accurately linear (over a sixty-fold range of concentrations), showing the reaction to be second order, viz. 

E. Quench and purification. While the butyllithium addition is taking place, an acidic ethanol quench solution is prepared in a 3-L, two-necked, round-bottomed flask, equipped with a mechanical stirrer and a 250-mL, pressure-equalizing dropping funnel. The flask is charged with 1 L of absolute ethanol and the funnel with 250 mL of acetyl chloride. The ethanol is stirred rapidly and the flask is cooled with an ice bath as the acetyl chloride is added over a 30-40-min period and then the cooling bath is removed and stirring is continued for 20-30 min. After the main reaction mixture has been stirred for 30 min at room temperature, it is cooled with a dry ice-acetone bath. The acidic ethanol solution is cooled with an ice bath and the cold, main reaction mixture is quenched by addition (via a double-ended needle) into the rapidly stirred, cold, acidic ethanol solution over a 3 to 3.5 hr period (Note 16). 

It is important to quench the reaction into the acidic ethanol. If the quench solution is added to the reaction mixture, very little product is obtained. 

A reaction quench is a system where an inhibiting substance (quench solution stored in a separate container vessel) can be quickly and effectively fed into the reactor via a pipe which is protected with appropriate isolation valves. This action is independent of other process actions that may be required. The reaction quench can be manually initiated or automatically when certain process parameters are exceeded. 

Carotenoids exhibit multiple physiological roles, i.e. as light-harvesting pigments in photosynthesis, as quenching solutes for the triplet state of chlorophyll a to... 

A fully automated system for performing detailed studies has been developed to improve the reproducibility and throughput (Fig. 12.2) [8]. It consists of two functional components a sample-deuteration device and a protein processing unit. The preparation operations (shown at the top of Fig. 12.2) are performed by two robotic arms equipped with low volume syringes and two temperature-controlled chambers, one held at 25 °C and the other held at 1 °C. To initiate the exchange experiment, a small amount of protein solution is mixed with a deuter-ated buffer and the mixture is then incubated for a programmed period of time in the temperature-controlled chamber. This on-exchanged sample is immediately transferred to the cold chamber where a quench solution is added to the mixture. 

Fig. 12.2 Diagram of a fully automated system for acquiring H/D exchange MS data starting with a stock solution of the nondeuterated protein. In this system [8], the liquid handler mixes a small amount of concentrated protein solution with a selected deuterated buffer and the mixture is incubated for a programmed period of time. The exchange reaction is conducted in a temperature-controlled chamber held at 25 °C. The mixture is then transferred to an acidic quench solution held at 1 °C. After quenching the exchange reaction, the entire sample is injected onto an LC-MS system...

The exchange-quenched solution is then injected onto the protein processing system which includes injection loops, protease column(s), a trap column, an analytical column, electronically controlled valves, and isocratic and gradient pumps. 

Addition of the aqueous solution is exothermic and should, therefore, be carried out over the course of a few minutes. The checkers found that the initial internal temperature was S-O C which rose to 10°C upon addition of the first few mL of quench solution. 

Peroxide-Dependent Oxidations with Cytochrome P 450. Peroxide-dependent oxidations were carried out exactly as described above except that NADPH-cytochrome P-450 reductase and NADPH were omitted. The peroxide solution (50 fxL of a 20mM solution) was added to the premixed enzyme-substrate solution. The quenching solution was 100 fxL of 30% sodium hydroxide saturated in sodium dithionite. 

Quench solution 50 mM NH4C1 in PBS to quench free aldehyde groups after fixation. 

Following treatment, cells are fixed in 1 mL of 3% PFA for 10 min, then washed in PBS and incubated in quench solution for at least 20 min. 

Assay volumes usually range from 3 pL (for 1536-well MTPs) to 50 pL (384-well MTPs). Within a given total assay volume, smaller volumes of reagents are added. Frequently, we find it convenient to add reagents into the assay in equivalent volumes of assay buffer. As an example, for a 15-pL assay, one might add 5 pL of compound solution, 5 pL of enzyme stock solution, 5 pL of substrate mix, followed by 10 pL of quench solution in a stop buffer. For kinase assays, the stop buffer may be EDTA and for phosphatase assays, sodium orthovanadate. 

The formulations are taken from the literature and some predate the secondary scintillators dimethyl-POPOP and bis-MSB. These secondary scintillators may be used in any of the formulations given and are especially recommended for quenched solutions, in which an increased amount of secondary scintillator is desired. 

Calcein fluorescence quench solution Cobalt chloride (CoClj) (Sigma-Aldrich, St. Louis, MO) (see Note 8) is dissolved in 50nM 3-morpholinepropanesulphonic acid (MOPS) buffer (pH 7.5). 

Add 1 pi of quenching solution, followed by 0.5 pi of the appropriate pharmalyte solution. 

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