Triethylammonium acetate

In this experiment students analyze an artificial RNA digest consisting of cytidine, uridine, thymidine, guanosine, and adenosine using a Cjg column and a mobile phase of 0.4% v/v triethylammonium acetate, 5% v/v methanol, and 94.6% v/v water. The chromatogram is recorded using a UV detector at a wavelength of 254 nm. 

Fig. 2-5. Examples showing the complementary separations on glycopeptide CSPs. (A) Separation of N-CBZ-norvaline on vancomycin (left) and teicoplanin (right). The mobile phase was methanol 1 % triethylammonium acetate (20/80 v/v) pH 4.1. (B) Separation of warfarin on teicoplanin (left) and vancomycin (right) CSPs. The mobile phase was acetonitrile 1 % triethylammonium acetate (10/90 v/v) pH 4.1. (C) Separation of naproxen on teicoplanin (left) and ristocetin A (right). The mobile phase was methanol 0.1 % triethylammonium acetate (30/70 v/v) pH 4.1. All columns were 250 x 4.6 mm i.d. The flow rate for all the separations was 1 mL min1 at ambient temperature (23 °C).

Fig. 2-15. Reversed-phase retention of the first eluted and the second eluted enantiomers of 5-methyl-5-phenylhydantoin as a function of mobile phase composition. The column was a 250 x 4.6 mm vancomycin CSR The buffer was triethylammonium acetate at pH 7.0. The flow rate was 1.0 mL min-1 at ambient temperature (23 °C).

Merino-Merino et al. [32] used the OPA reagent (o-phthaldehyde condensed with 2-mercaptoethanol) to separate penicillamine enantiomers after their derivatization. Racemic and (/q-penicillamine were dissolved in aqueous 0.5 M NaOH, and treated with the derivatizing solution (methanolic o-phthaldehyde and 2-mercaptoethanol in 0.4 M potassium borate buffer solution of pH 10). The reaction mixture was set aside for 2 min at room temperture, whereupon a portion of solution was analyzed by HPLC. The method used a Cyclobond column (25 cm x 4.6 mm) maintained at 5 °C, a mobile phase of ethanol/1% triethylammonium acetate (1 1 pH 4.5) eluted at... 

DHQD-CL or DHQ-CL) was used as the chiral auxiliary.175,176 However, the enantioselectivity observed under catalytic conditions was inferior to that observed under stoichiometric conditions. The addition of triethylammonium acetate, which increases the rate of hydrolysis of the Osvm-glycolate intermediate, improved enantioselectivity. A further improvement in enantioselectivity was brought about by the slow addition of substrates (Scheme 44).177 These results indicated that the hydrolysis of the Osvm-glycolate intermediate (57) was slow under those conditions and (57) underwent low enantioselective dihydroxylation (second cycle). Thus, Sharpless et al. proposed a mechanism of the dihydroxylation including a second cycle (Scheme 45).177 Slow addition reduces the amount of unreacted olefin in the reaction medium and suppresses the... 

ACN acetonitrile, TEA triethylamine, MeOH methanol, DEA Diethylamine, IPA isopropanol, TEAA triethylammonium acetate, ElOAc glacial acetic acid. 

Tubes for collecting fractions 100 mM triethylammonium acetate, pH 7.0, in water 10 mM triethylammonium bicarbonate, pH 7.0, in water... 

Armstrong et al. [54] resolved the enantiomers of some amino acids and their derivatives on x-CD-based CSPs using 1% aqueous triethylammonium acetate (pH 5.1). The same authors also tested a /LCD CSP for the chiral resolution of amino acids [55]. In addition, they evaluated a y-CD phase for the enantiomeric resolution of some dansyl amino acids and other drugs. The mobile phase was 38% methanol with 1% triethylammonium acetate [58]. In another study, the same authors reported the chiral resolution of 25 pairs of amino acids in less than 30 min [63]. The enantiomers of some /i-adrcncrgic blockers were resolved on a /LCD stationary phase, with 1% aqueous triethylammonium acetate, containing methanol, as the mobile phase [9,48]. 

In the reversed phase system, buffers are used most often as the mobile phases with small amount of organic modifiers. The use of buffers as the mobile phases has increased the efficiency of the resolution. Ammonium nitrate, triethylammonium acetate (TEAA), and sodium citrate buffers have been used very successfully. A variety of organic modifiers have been used to alter selectivity [2,5,22], Acetonitrile, methanol, ethanol, 2-propanol, and THF have shown good selectivities for various analytes. In the reversed-phase mode, the amount of organic modifiers is typically low, usually of the order of 10-20%. The typical starting composition of the mobile phase is an organic modifier-buffer... 

FIGURE 7 Effect of mobile phase composition on the resolution of enantiomers of different racemates in reversed-phase HPLC on antibiotic CSPs. (a) First ( , O) and second ( , ) enantiomers of 5-methyl-5-phenylhydantoin on a Chirobiotic T column using an acetonitrile-triethylammonium acetate buffer (—) and a methanol-triethylammo-... 

TABLE 4 Effect of pH on Chiral Resolution of Several Racemates on Chirobiotic V CSP Using Acetonitrile-1% Triethylammonium Acetate Buffer (10 90, v/v) as the Mobile Phase... 

FIGURE 10 Effect of temperature on enantiomeric resolution on antibiotic CSPs. (a) k, a, and Rs for proglumide (O), 5-methyl-5-phenylhydantoin ( ) and iV-corbyl-DL-pheny-lalanine (x) on Chirobiotic V column using acetonitrile-1 % triethylammonium acetate buffer (10 90, v/v) as the mobile phase and (b) separation of enantiomers of /1-methyl phenylalanine on the Chirobiotic T column using water-methanol (10 90, v/v) as the mobile phase at (A) 1°C, (B) 20°C, (C) 50°C. 1 = erythro-L 2 = erythro-D 3 = threo-L 4 = threo-D. (From Refs. 1 and 22.)... 

Aziridinyl ketones can be synthesized from unsaturated carbonyls using a series of other methods. For example, azabicyclo[4.1.0]heptanone 27 was obtained from cyclohexenone 25 in its reaction with TV-bromotoluenesulfona-mide sodium salt 33 [49] (Scheme 1.10). The reaction of chalcone with N-chlorotoluenesulfonamide in the presence of silver nitrite is described in [50]. Trans-Aziridinyl ketone 18 was synthesized by reacting chalcone 22 with N,N-diamino-l,4-diazoniabicyclo[2.2.2.]octane dinitrate 34 and sodium hydride in 2-propanol [30, 51]. Aziridinyl ketones can be obtained in the reaction of a -unsaturated ketones with A,A-dichlorosulfonamines [52] and with amines in the presence of lead tetraacetate and trifluoroacetic acid [53] or in the presence of triethylammonium acetate under electrochemical reaction conditions [54]. 

Enantiometric mixtures of nimodipine were separated on (3-cyclodextrin-bonded silica gel plates. The plates were developed with light petroleum/ ethyl acetate/methanol, methanol/1% triethylammonium acetate (pH 4.1), or methanol/acetonitrile/1% triethylammonium acetate as mobile phases. Spots were identified by illumination at 365 nm, or by exposure to iodine vapor [11]. 

DHPLC is usually performed on a styrene-divinylbenzene-based polymeric stationary phase, with a mobile phase that contains triethylammonium acetate as the IPR to provide adequate reversed phase (RP) retention for the negatively charged nucleic acid molecules. The samples are usually amplified according to polymerase chain reaction (PCR) protocols and then injected into the chromatographic system. 

---