Ammonium hydrogencarbonate

The oxidation of methyl phenyl sulfide with hydrogen peroxide, in the presence of ammonium hydrogencarbonate, takes place by a mechanism involving HCO4-... 

The ki of the carboxylation of resorcinol with ammonium hydrogencarbonate was about one tenth of that with potassium hydrogencarbonate. These results are in agreement with the reported lower yield (53.9%) [7] of the product even at applying higher pressure (5 MPa) and higher temperatures (110-125 °C). 

Literature proposed CZE methods for phenols and derivatives using test mixtures based on aqueous buffered systems (phosphate-borate and borate " ), volatile electrolytes (ammonium hydrogencarbonate, diethylmalonic acid/dimethylamine in isopropanol and L-cysteic acid, 3-amino-1-propanesulfonic acid, aminomethanesulfonic acid, and diethylmalonic acid ), andnon-aqueous media (ammonium acetate in ACN/acetic acid in MeOH acetate, bromide, chloride, and malonate in ACN and diprotic acids/tetrabutylammonium hydroxide and maleate in MeOH ). 

Figure 13 LH (A) and PH (B) curves for the decomposition of ammonium hydrogencarbonate. (Reproduced with permission from Parkes GMB, Barnes PA, and Charsiey EL (1999) Analytical Chemistry 71 2482-2487.)...

Ammonia is dissolved in brine and the solution is added to the top of a tower up which carbon dioxide is passed. Ammonium hydrogencarbonate is formed. This reacts to form a precipitate of sodiumhydrogen carbonate, which is sparingly soluble in brine... 

Both Camag and Analtech also distribute sealed chambers commercially, utilizing ammonium hydrogencarbonate for visualization purposes. Vapors formed as the salt is heated tend to char or otherwise cause visual changes in a plate which is heated simultaneously. Many compounds form fluorescent derivatives under these conditions. 

Fig. 4. MS-compatible buffers, 20 mM from the left formate, acetate, ammonium, ammonium hydrogencarbonate.

LC/MS applications in the alkaline pH range. The reason for this is the overlapping and additive buffer capacities of the ammonium cation and the hydrogencarbonate anion. Above 60 °C, ammonium hydrogencarbonate decomposes into water, ammonia, and carbon dioxide. 

Fig. 7. pH values of an ammonium hydrogencarbonate buffer with an aqueous pH of 9.8 0 methanol, acetonitrile. 

Other buffers often exhibita substantial UV absorption below 215 nm. However, for the normal UV detection range around 254 nm a large number of buffers is available. Acetate with its pK of 4.75 is probably the most popular buffer, since its pK is exactly intermediate between the first and second dissociation constants of phosphate. Ammonium hydrogencarbonate is a preferred buffer for the pH range around 9 to 10, since the buffering ranges of the ammonium ion (pK = 9.24) and the hydrogencarbonate ion (pK, = 10.25) overlap. 

We have already mentioned some of the commonly used mobile phase additives for MS-compatible pH control. The most important attribute is the volatility of all buffer components. The most frequently used mobile phase additives are formic acid and acetic acid, together vhth the true buffers formic acid/ammonium formate and acetic acid/ammonium acetate. In the alkaline pH range, the preferred additive is ammonia, and the buffer of choice is ammonium hydrogencarbonate. One can also use the ammonium ion with volatile counterions such as formate or acetate to establish a true buffer at the pfQ of the ammonium ion (pKj = 9.24). One finds sometimes in the literature the reported use of ammonium formate or acetate at neutral pH. It needs to be pointed out that this has little to do with pH control, since these salt solutions have no buffer capacity at pH 7 ... 

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