Sodium acetate detection

The triphenylmethoxyacetate was prepared in 53% yield from a nucleoside and the sodium acetate (Ph3C0CH2C02Na, i-Pr3C6H2S02Cl, Pyr) as a derivative that could be easily detected on TLC (i.e., it has a distinct orange-yellow color after it is sprayed with ceric sulfate). It is readily cleaved by NH3/MeOH (100% yield). ... 

Note The reagent can be employed on cellulose layers. Sodium acetate-buffered kieselguhr layers are less suitable [6]. Only a few sugars are detectable and those with lower sensitivity if acid is not added to the reagent [7]. 

The existence of Br nsted relationships affects the experimental problem of detecting general acid or base catalysis. This is clearly shown by an example given by Bell. Consider the reaction under study as carried out in an aqueous solution containing 0.10 M acetic acid and 0.10 M sodium acetate, and suppose that the Br nsted equation applies. Three catalytic species are present these are HjO, with = - 1.74 H2O, pKa 15.74 and HOAc, pTiT 4.76. -pp i7i-3 93.pp.9i-5 9s concentrations of these acids are 1.76 x lO- M, 55.5 M, and 0.10 M, respec-... 

Fig. 7-9. Separation of amino acids after derivatization 5 with OPA and mercaptoethanol. Column Superspher 100 RP-18 (4 pm) LiChroCART 250-4, mobile phase 50 mM sodium acetate buffer pH 7.0/methanol, flowrate 1.0 ml min temperature 40 °C detection fluorescence, excitation 340 nm/emission 445 nm. Sample amino acid standard sample (Merck KGaA Application note W219180).

In the galvanic detector, the electrochemical detector consists of a noble metal like silver (Ag) or platinum (Pt), and a base metal such as lead (Pb) or tin (Sn), which acts as anode. The well-defined galvanic detector is immersed in the electrolyte solution. Various electrolyte solutions can be used, but commonly they may be a buffered lead acetate, sodium acetate and acetic acid mixture. The chemical reaction in the cathode with electrons generated in the anode may generate a measurable electrical voltage, which is a detectable signal for measurements of DO. The lead is the anode in the electrolyte solution, which is oxidised. Therefore the probe life is dependent on the surface area of the anode. The series of chemical reactions occurring in the cathode and anode is ... 

Some observations are important for improvement of the yield and for the elucidation of the mechanism of the Meerwein reaction. Catalysts are necessary for the process. Cupric chloride is used in almost all cases. The best arylation yields are obtained with low CuCl2 concentrations (Dickerman et al., 1969). One effect of CuCl2 was detected by Meerwein et al. (1939) in their work in water-acetone systems. They found that in solutions of arenediazonium chloride and sodium acetate in aqueous acetone, but in the absence of an alkene, the amount of chloroacetone formed was only one-third of that obtained in the presence of CuCl2. They concluded that chloroacetone is formed according to Scheme 10-50. The formation of chloroacetone with CuCl2 in the absence of a diazonium salt (Scheme 10-51) was investigated by Kochi (1955 a, 1955 b). Some Cu11 ion is reduced by acetone to Cu1 ion, which provides the electron for the transfer to the diazonium ion (see below). 

In the context of their new synthetic route to arenediazo phenyl ethers (see Sec. 6.2), Tezuka et al. (1987 a, 1989) investigated the reaction products of phenyldi-azo 1-naphthyl ether (12.10) under various conditions. When an acetonitrile solution of the diazo ether 12.10 was kept standing at room temperature for one week in the dark, the 4- and 2-phenylazo-l-naphthol isomers (12.11 and 12.12) were formed in 48% (20%) and 9% (8%) yields respectively. In the presence of acid (aqueous HC1 or H2S04) or of various bases (aqueous NaOH, pyridine, aniline, or sodium acetate) the yields of the azo products are much lower, but higher proportions of biphenyl, 1-naphthol, and phenol are formed. The crosscoupling product l-phenylazo-2-naphthol was not detected when the reaction was carried out in the presence of 2-naphthol. As this mechanistic test reaction gave rather low yields of the two azo compounds 12.11 and 12.12 in the presence and absence of 2-naphthol,... 

Note The sodium acetate was added to the mobile phase solely to improve the separation. It had no detectable effect on the production of fluorescence during thermal activation, since the fluorescence reaction also occurred in the absence of sodium acetate. 

Note It is occasionally recommended that sodium acetate be added to the reagent [2]. Thiophosphate insecticides with a simple P—S bond yield yellow chromatogram zones and those with a P=S double bond yield brown ones on a light brown background [10]. Further treatment of the stained chromatogram with iodine vapors increases the detection sensitivity [7] more than does spraying afterwards with caustic soda solution, which is also occasionally recommended [16, 17, 20, 21]. 

Verhoef and co-workers suggested omitting the foul smelling pyridine completely and proposed a modified reagent, consisting of a methanolic solution of sulphur dioxide (0.5 M) and sodium acetate (1M) as the solvent for the analyte, and a solution of iodine (0.1 M) in methanol as the titrant the titration proceeds much faster and the end-point can be detected preferably bipoten-tiometrically (constant current of 2 pA), but also biamperometrically (AE about 100 mV) and even visually as only a little of the yellow sulphur dioxide-iodide complex S02r is formed (for the coulometric method see Section 3.5). 

Fluorescence of the diaminopyridine group allows detection of conjugates down to the pico-mole range, with excitation and emission maxima at 345 and 400 nm, respectively. For detection of BAP and its conjugates, the optimal buffer environment is less than pH 5, because its fluorescent properties are pH dependent. A preferred buffer is sodium acetate at pH 4. 

FMOC-amino acids can be chromatographed using a C8 column and acetonitrile in sodium acetate buffer as the mobile phase. Fluorescence detection with excitation at 260nm and emission at 31 Onm gives the best results. 

Figure 3.19 Theophylline in blood serum on vinyl alcohol polymer column. Conditions column, Asahipak GS320 (vinyl alcohol copolymer gel), 50 cm x 7.6 mm i.d. eluent, 0.01 M sodium acetate buffer pH 4.0 in 10% aqueous acetonitrile flow rate, 2 ml min-1 detection, UV 280 nm. Peaks 1, protein 2, low Mr impurity and 3, theophylline.

Figure 4.12 Effect of counter-ions and copper on the retention of amino acids. Column, octadecyl-bonded silica gel, 25 cm x 4.6 mm i.d. eluent, 0.01 M sodium acetate buffer (pH 5.6) containing 1.2 mM sodium octanesulfonate (Oc) andj or 0.1 mM copper acetate (Cu) flow rate, 1ml min-1 detection, UV 220 nm. Compounds Glu, glutamic acid, Asp, aspartic acid.

Figure 4.15 Ion-pair liquid chromatography of free amino acids using a column switching system. Column I, butyl-bonded silica gel, 50 x 4.6 mm i.d., 2, octyl-bonded silica gel, 50 x 4.6 mm i.d., and 3, octadecyl-bonded silica gel, 250 x 4.6 mm i.d. eluent, 0.01 m sodium acetate buffer (pH 5.6) containing 4 mM copper acetate and 0.8 mM sodium heptanesulfonate flow rate, 1 ml min-1 detection, UV 235 nm. Peaks 1, Tyr 2, Val 3, Met 4, His 5, Lys 6, lie, 7, Leu 8, Phe 9, Arg 10, Asp 11, Ser 12, Glu 13, Thr 14, Gly 15, Pro 16, Cys and 17, Ala. 1-9 were separated on column 1 and 10-17 were separated by a combination of columns 2 and 3.

Figure 12.1 Clearance of small-molecule impurities from process buffers in a formulated protein product. Trace A the NMR spectrum of a control sample containing a mixture of three components (succinate, tetraethylammonium, and tetramethylammonium) in the final formulation buffer (sodium acetate). These three components were used in the recovery process for a biopharmaceutical product. Traces B and D the proton NMR spectra of the formulated protein product. No TEA or TMA were detected, but a small amount of succinate was observed in this sample. Traces C and E the proton NMR spectra of a formulated protein product spiked with 10 jag/ml of succinate, TEA, and TMA. Traces D and E were recorded with CPMG spin-echo method to reduce the protein signals. The reduction of NMR signals from the protein allows for better observation of the small-molecule signals.

FIGURE 3 Electropherogram of (di)aminopyridine standards. Electrophoretic conditions capillary 67 cm total length (60cm effective length), 50 pm ID BGE 100 mM sodium acetate buffer, pH 5.15 voltage 20 kV detection 240 nm. 4-AP 4-aminopyridine 2-AP 2-aminopyridine 3-AP 3-aminopyridine 3,4-DAP 3,4-diaminopyridine 2,3-DAP 2,3-diaminopyridine 2,6-DAP 2,6-diaminopyridine NEDA N-(l-naphthyl)ethylenediamine (internal standard). (Reprinted from reference 125, with permission.)... 

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