Ammonium Acetate Phosphate

Buffer systems based on ammonium acetate, phosphate or hydrogen carbonate are usually added at concentrations of about 20 mM to adjust the pH of the mobile phase to values between 2 and 8. Ion pairing reagents can be used at low concentrations, typically 0.1%, to increase the hydrophobicity of charged analytes. They... 

AMMO 2.5 EC , cypermetlu-in, 13 Ammonia, 13 Ammonium acetate, 13 Ammonium arsenate, 13 Ammonium benzoate, 13 Ammonium bicarbonate, 13 Ammonium bifluoride, 14 Ammonium bisulfite, 14 Ammonium carbamate, 14 Ammonium carbonate, 14 Ammonium chloride, 14 Ammonium chlorplatmate, 14 Ammonium clu omate, 14 Ammonium citrate, 14 Ammonium diclu omate, 14 Ammonium fluoride, 14 Ammonium fomiate, 15 Ammonium hexafluorosilicate, 15 Ammonium hydroxide, 15 Ammonium metavanadate, 15 Ammonium molybdate, 15 Ammonium nitrate, 15 Ammonium oxalate, 15 Ammonium perfluorooctanoate, 15 Ammonium persulfate, 15 Ammonium phosphate, 15 Ammonium picrate, 16 Ammonium salicylate, 16... 

Crucibles fitted with permanent porous plates are cleaned by shaking out as much of the solid as possible, and then dissolving out the remainder of the solid with a suitable solvent. A hot 0.1 M solution of the tetrasodium salt of the ethylenediaminetetra-acetic acid is an excellent solvent for many of the precipitates [except metallic sulphides and hexacyanoferrates(III)] encountered in analysis. These include barium sulphate, calcium oxalate, calcium phosphate, calcium oxide, lead carbonate, lead iodate, lead oxalate, and ammonium magnesium phosphate. The crucible may either be completely immersed in the hot reagent or the latter may be drawn by suction through the crucible. 

Discussion. Some of the details of this method have already been given in Section 11.11(C), This procedure separates aluminium from beryllium, the alkaline earths, magnesium, and phosphate. For the gravimetric determination a 2 per cent or 5 per cent solution of oxine in 2M acetic add may be used 1 mL of the latter solution is suffident to predpitate 3 mg of aluminium. For practice in this determination, use about 0.40 g, accurately weighed, of aluminium ammonium sulphate. Dissolve it in 100 mL of water, heat to 70-80 °C, add the appropriate volume of the oxine reagent, and (if a precipitate has not already formed) slowly introduce 2M ammonium acetate solution until a precipitate just appears, heat to boiling, and then add 25 mL of 2M ammonium acetate solution dropwise and with constant stirring (to ensure complete predpitation). 

Beryllium is sometimes precipitated together with aluminium hydroxide, which it resembles in many respects. Separation from aluminium (and also from iron) may be effected by means of oxine. An acetic (ethanoic) acid solution containing ammonium acetate is used the aluminium and iron are precipitated as oxinates, and the beryllium in the filtrate is then precipitated with ammonia solution. Phosphate must be absent in the initial precipitation of beryllium and aluminium hydroxides. 

Synthesis of the pyridine derivative, in which the nitrogen is closest to the A-ring was also described by Simoni et al. [60], is shown in Scheme 34 and was more productive than the synthesis described in Scheme 33. The keto-compound 134 was reacted with the vinamidinium hexafluorophosphate salt (CDT-phosphate) 135, ferf-BuOK, ammonium acetate, and an equimolar amount ofDABCO (l,4diazabicyclo[2.2.2]octane). Hydrogenation using 10%... 

When chromatographic resolution of species based on modifications located at the protein surface is desired, it may be advisable to use conditions that favor retention of native conformation.17 Here, the standard acidic conditions described in the preceding text may be inappropriate, and mobile phases buffered near neutrality may be required. Buffers based on ammonium acetate, ammonium bicarbonate, and triethylammonium phosphate may prove more useful in resolving polypeptide variants with differing posttranslational modifications, amino acid substitutions, or oxidation and deamidation products. The addition of more hydro-phobic ion-pairing agents may be needed to obtain polypeptide retention, and a variety of alkyl sulfonates and alkyl amines have been described for specific applications.17... 

Proteins crystallized from very low salt concentrations (examples are carboxypeptidase A and elastase) can often be treated exacdy like proteins crystallized from alcohol-water mixtures. Their low solubility in water allows them to be transferred from their normal mother liquor to a distilled water solution or to a solution of low (10-20%) alcohol concentration without disorder. It is advisable to carry out this transfer at near 0 C to further decrease the protein solubility. From this stage it is trivial to add alcohol while cooling, as described above. Complications arise, however, when the salt employed as a precipitant in the native mother liquor is insoluble in alcohols. The solution to this problem is to replace the salt by ammonium acetate at equivalent or higher ionic strength. Ammonium acetate is soluble up to 1 M in pure methanol, and is very soluble in nearly all alcohol-water mixtures, even at low temperature. It therefore provides a convenient substitute for salts such as sodium sulfate or sodium phosphate. 

Non-absorbing BGEs such as tetraborate at pH 9.3 and phosphate at pH values 10.2, 7.5, 6.5, 6.25, 6, or 2.5 may be used. Low pH buffers are also useful for the separation of nitrite from nitrate, taking advantage of their respective of 3.29 and —1.3. Special applications are CE—MS-compatible buffers where ammonium hicarhonate or ammonium acetate may be used. 

Different organic and inorganic buffers, such as ammonium acetate, ammonium formate, HEPES, Gly-Gly, and triethanolamine, were selected to study the response of biotin and fluorescein-biotin in MS and compared to phosphate buffer. Biotin and fluorescein-biotin were dissolved in the carrier solution compositions of buffer (10 mM pH 7.5)/methanol (50 50, v/v) at concentrations of 10 ng pl k Both infusion and 20 pl-loop injection experiments were performed with detection by MS in full-scan and SIM mode. Main optimization criteria are the maximum response of biotin and fluorescein-biotin with lowest interference of the carrier solution. HEPES, Gly-Gly, and triethanolamine give very high background response, which significantly hampers the detection of biotin and fluorescein-... 

Some commonly used buffers, such as sodium and potassium phosphate, are incompatible with ELSD, but there are ready alternatives. For example, ammonium acetate has similar buffering properties to potassium phosphate, and ammonium carbonate, ammonium formate, pyridinium acetate, and pyridinium formate are options for different pH ranges. Typical mobile phase modifiers that do not meet the volatility criteria can be replaced by a wide variety of more volatile alternates. For example, phosphoric acid, commonly used as an acid modifier fo control pH and ionization, can be replaced by trifluoroacetic acid other acids that are sufficiently volatile for use with FLSD include, acetic, carbonic, and formic acids. Triethylamine, commonly used as a base modifier, is compatible with FLSD other base modifiers that can be used are ethylamine, methylamine, and ammonium hydroxide [78]. 

If you use a buffer in the eluent, it must be volatile or else it will evaporate down to solid particles that scatter light and obscure the analyte. Low-concentration buffers made from acetic, formic, or trifluoroacetic acid, ammonium acetate, diammonium phosphate, ammonia, or triethylamine are suitable. Buffers for evaporative light scattering are the same as for mass spectrometric detection. 

Ammonium molybdate, when added in considerable excess to a boiling solution of an arsenate in nitric acid, gives a yellow crystalline precipitate of ammonium 12-molybdo-arsenate, (NH4)3H4[As(Mo207)6]. 4H20 (see p. 215). Like the corresponding molybdo-phosphate, the precipitate is readily soluble in ammonia or aqueous alkali. The arsenate may be detected in the presence of phosphate by boiling the yellow precipitate with aqueous ammonium acetate until clear a white precipitate or turbidity on cooling shows the presence of arsenate, and the filtrate may be tested for phosphate.1... 

Reaction velocity, proteinases, 355-356 Reagents and Solutions 5a-cholestane solution, 459 acrylamide solutions, 176 alcoholic potassium hydroxide (KOH), 472 alkaline phosphate substrate buffer, 213 ammonium acetate buffer, 0.1 M, pH 5.2, 714... 

FAB ionization has been used in combination with LC/MS in a technique called continuous-flow FAB LC/MS (Schmitz et al., 1992 van Breemen et al., 1993). Although any standard HPLC solvent can be used, including methyl-ferf-butyl ether and methanol, the mobile phase should not contain nonvolatile additives such as phosphate or Tris buffers. Volatile buffers such as ammonium acetate are compatible at low concentrations (i.e., <10 mM). Continuous-flow FAB has also been used in combination with MS/MS (van Breemen et al., 1993). The main limitationsof continuous-flow FAB compared to other LC/MS techniques for carotenoids, such as ESI and APCI, are the low flow rates and the high maintenance requirements. During use, the 3-nitrobenzyl alcohol matrix polymerizes on the continuous-flow probe tip causing loss of sample signal. As a result, the continuous-flow probe must be removed and cleaned approximately every 3 hr. 

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