Triethyl ammonium acetate

Fig. 2-10. The effect of flow rate on the resolution of methylphenidate enantiomers on vancomycin CSP (250 x 4.6 mm). The mobile phase was methanol 1.0 % triethyl-ammonium acetate (95/5 v/v) pH 4.1 at ambient temperature (23 °C).

Examples of possible intramolecular general acid-base catalysis were reported by Kupchan et al. (1962). The methanolysis of coprostanol acetate and coprostane 3/3, 5/3-diol 3-monoacetate [12] in aqueous methanol was conducted in triethylamine-triethyl-ammonium acetate buffer. The rates of methanolysis at constant... 

FIGURE 4.5 Chromatograms of (a-e) tetralone derivatives on ristocetin A CSP using hexane-ethanol-TEA (12 8 02, v/v/v), (f) 3-amino-3-phenyl propionic acid [methanol-water (60 40, v/v)], (g) midodrine [methanol-1% triethyl ammonium acetate buffer, pH 7 (20 80, v/v)], (h) A-FMOC-glycy 1-arginine [methanol-water (60 40, v/v)], (i) thyroxine [methanol-1% triethyl ammonium acetate buffer, pH 7 (20 80, v/v)], (j) trihexyphenidyl [methanol-1% triethyl ammonium acetate buffer, pH 7 (20 80, v/v)] and (k) verapamil [methanol-1% triethyl ammonium acetate buffer, pH 7 (20 80, v/v)] on avoparcin CSP (From Refs. 8 and 14.)... 

Nucleotides and Dinucleotides Figure 17 shows the chromatogram of the dinucleotides where adenosine is connected with another nucleoside by diphosphate ester bond. The mobile phases used for the dinucleotides were (A) water and (B) methanol with volatile buffer system of triethyl-ammonium acetate. The clear separation of the dinucleotides as shown in these figures shows that the separation of the dinucleotides depends on the kind of nucleotide units, other than adenosine, in the dinucleotide. Figures 18 (water mobile phase) and 19 (methanol mobile phase) show the results for the six kinds of stationary phases. In both water and... 

The most common and the best example in this category comes from the application of cyclodextrins (CDs). Alak and Armstrong [5] mixed )8-CD-bonded silica gel with a binder in 50% aqueous methanol, whereas methanol/1% aqueous triethyl ammonium acetate (pH 4.1) was used as mobile phase for the resolution of enantiomers of dansyl amino acids. Because, then, CDs have been used in different manners, that is, as impregnating agent as well as chiral mobile phase additive for... 

Polypeptide Synthesis and Analysis. Sihca or controUed-pore glass supports treated with (chloromethyl)phenylethyltrimethoxysilane [68128-25-6] or its derivatives are replacing chloromethylated styrene—divinylbenzene (Merrifield resin) as supports in polypeptide synthesis. The sdylated support reacts with the triethyl ammonium salt of a protected amino acid. Once the initial amino acid residue has been coupled to the support, a variety of peptide synthesis methods can be used (34). At the completion of synthesis, the anchored peptide is separated from the support with hydrogen bromide in acetic acid (see Protein engineering Proteins). 

For sufficient retention of these very polar sulfonated carboxylates on RP columns, the addition of an ion-pairing (IP) agent such as tetraethylammonium acetate (TEAA) to the LC buffer was compulsory [13]. To maintain the compatibility of the eluent with the MS interface, the use of such an involatile cationic additive entailed a cation exchanger to be placed between the column and the interface [13]. Alternatively, equimolar amounts (5 mM) of acetic acid and triethyl-amine, which form the volatile IP agent triethylammonium, were added to the mobile phase in order to improve the retardation of very polar SPC [14]. While the first approach with TEAA was effective in retaining even the very short-chain C3- and C4-SPC (Fig. 2.10.4), the weaker IP agent triethylammonium notably increased the retention of C5-SPC and higher, whereas C4-SPC elutes almost with the dead volume of the LC (Fig. 2.10.5). Addition of commonly used ammonium acetate as buffer component led to the co-elution of the short-chain SPC ([Pg.322]

Therefore, the way to ensure reproducible adduct formation is to use mobile-phase additives (e.g. ammonium acetate or formate, formic, acetic or trifluoroacetic acid (in APCI), ammonium hydroxide, etc.). Their application in the mobile phase can be an effective way to improve the intensity of the MS signal and LC-MS signal correlation between matrix and standard samples. However, it is observed that some additives like trifluoroacetic acid or some ion-pairing agents (triethyl-amine) may play a role in ionisation suppression [3]. In addition, high concentrations of involatile buffers will cause precipitation on, and eventually blocking of, the MS entrance cone, leading to a fast decrease of sensitivity. For the in volatile NaAc buffer, it is advisable to maintain... 

Since the double bond placement in enol silyl ethers is predictable and controllable,18 the method allows the regiospecific introduction of a-hydroxy groups. Omission of the fluoride treatment permits isolation of a-trimethylsiloxy carbonyl compounds,17 while treatment of enol silyl ethers, first with HCPBA, then with triethyl ammonium fluorlde/acetic anhydride gives... 

The best route is the synthesis from ammonium acetate and triethyl orthoformate (see Section 2.20.4.5.2). 

MeCN/MeOH/ethyl acetate, 88 10 2 MeOH/MeCN/ CH2Cl2/hexane, 65 27 4 4 MeCN/MeOH/ CH2C12 (75 20 15) containing 0.1% BHT and 0.05% triethyl-amine (the MeOH contains 0.05 M ammonium acetate)... 

Ammonium acetate, reaction with triethyl orthoformate to give form-amidine acetate, 46, 39 Ammonium />-chloropheny dithiocarba-mate, 45, 21... 

Gradients of aqueous and organic mobile phases are typically used for LC-MS/MS analysis of drug compounds and metabolites. The most common aqueous solvents are water with 0.1 % formic acid or 0.1 % acetic acid (v/v) or volatile buffers like 5 mM ammonium-acetate or ammonium-formate. Often adjusted to a certain pH value with the corresponding acid or base (the pH of the eluents will have to be optimized with respect to the polarity of the analytes, since ionic species will have very low or no retention on the reversed pahse LC-columns). Other volatile buffers can be used as well. Phosphate buffers should be avoided, since they will cause suppression of the ionization and thus lead to very bad analytical performance (Venn 2000). Reagents like triethyl-amine should also be avoided as mobile phase or as part of mobile phases. They induce ion suppression as well. In terms of the organic solvents, methanol and acetonitrile are very widely used and they are very well suitable for LC-MS. Other solvents can be used as well, as long as they are compatible with the materials used in the LC-MS system. 

The residue then was dissolved in 30 ml of 0.04 M aqueous triethyl-ammonium bicarbonate buffer (pH 7.5), (resulting pH 5.6). It was chromatographed on a DEAE cellulose column (HCOJ form) (3.4 X 15.0 cm), with elution first with 500 ml of water and then with a linear gradient of trimethylammonium bicarbonate at pH 7.2 (0-0.07 M). XXVII was completely resolved from some of XXVIII which was formed under the above reaction conditions. However, it was still contaminated by small amounts of cAMP and ethyl 2-diazo-malonic acid. These impurities were apparently generated from the hydrolysis of some XXVII when the triethylammonium bicarbonate was removed. Pure samples of XXVII were obtained by preparative paper chromatography on either Whatman 40 or 3 MM paper with overnight development with ethanol 0.5 M ammonium acetate, pH 7.0 (5 2, v/v). 

Ammonium, (methoxycarbonylsulfamoyl)-triethyl-,hydroxide, 56,41 Ammonium acetate, (2-phenyl-l-aziri-dinyl)-, 55,114 Amyl bromide, 56, 82 Aniline, 56, 122 57, 112 Aniline, 2-bromo-, p-bromination of, 55, 23 Aniline, 3-bromo-,p-bromination of, 55, 23 ANILINE, 4-bromo-/V,jV-dimethyl-3-(tri-fluoromethyl)-, 55, 20... 

Formimidamidium acetate, which can be formed from ammonium acetate and triethyl orthoformate, trimerizes to the parent 1,3,5-triazine in a yield of 81 % 283 (see Houben-Weyl, Vol. E5, p 119). 

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