Ascorbate buffer

Extraction with sodium phosphate-sodium citrate/ ascorbate buffer at 100°C for lOmin enzymatic digestion with papain and amylase... 

Grant et al. studied a similar system using [Ni(cyclam)]2+ as the catalyst (cyclam = 1,4,8,11-tetra-azacyclo tetradecane), [Ru(bpy)3]2+ as the photosensitizer, and ascorbic acid as the sacrificial reductant [34], and observed a pH dependence on CO/H2 ratios, with the best ratio of 0.83 1 at pH 5. When Kimura etal. prepared pyridine derivatives of [Ni(cyclam)]2+ [35], the best complex, in C02-saturated ascorbate buffer at pH 5.1 and [Ru(bpy)3]2+ as the photosensitizer, produced 5.8-fold more CO than [Ni(cyclam)]2+. 

Stability studies of DOTATATE labelled with Lu, 1, Sm and Ho were carried out in acetate/ascorbate buffer and saline at 4, 12, 24 and 36 h intervals at room temperature (15-18°C). The quality of the complexes was measured using TLC. 

For Bi, B2, B3, and Bg, a ground sample (1 g) was autoclaved with HCl (120° C, 30 min), cooled, diluted to known volume with aqueous ammonium acetate, vortexed, and centrifuged. The filtered supernatant was injected onto the LC column. For B5, a ground sample (4 g), was treated with acetate buffer (pH = 5.6) and autoclaved (121° C, 15 min), cooled, diluted to known volume with aqueous ammonium formate, vortexed, and centrifuged. The filtered supernatant was injected onto the LC column. For B9, ground sample (2.5 g) was mixed with a sodium phosphate—sodium citrate/ ascorbate buffer (pH = 8), heated, cooled, and incubated with papain and di-a-amylase (40°C, 2 hr). The solution was diluted to known volume with aqueous ammonium formate, vortexed, and centrifuged. 

The use of an amperometric detector is emphasized in this experiment. Hydrodynamic voltammetry (see Chapter 11) is first performed to identify a potential for the oxidation of 4-aminophenol without an appreciable background current due to the oxidation of the mobile phase. The separation is then carried out using a Cjg column and a mobile phase of 50% v/v pH 5, 20 mM acetate buffer with 0.02 M MgCl2, and 50% v/v methanol. The analysis is easily extended to a mixture of 4-aminophenol, ascorbic acid, and catechol, and to the use of a UV detector. 

Until recent years the only syntheses of 3-hydroxy quinoline involved multistep processes, the last step of which consisted of the conversion of 3-aminoquinoline to 3-hydroxyquinoline via the diazonium salt. " Small quantities of quinoline have been oxidized to 3-hydroxyquinoline in low yields by using oxygen in the presence of ascorbic acid, ethylenediaminetetraacetic acid, ferrous sulfate, and i)hosi)halc buffer. The decarboxylation of 3-hydroxycinchoninic, acid in boiling nitrobenzene has been re-... 

Fig. 6.2.4 Change in the absorption spectrum of pholasin (14.5 p,M) caused by the luminescence reaction catalyzed by Pholas luciferase (1.1 p.M). The curve shown is the differential spectrum between a cell containing the mixture of pholasin and Pholas luciferase (0.9 ml in the sample light path) and two cells containing separate solutions of pholasin and the luciferase at the same concentrations (in the reference light path), all in 0.1 M Tris-HCl buffer, pH 8.5, containing 0.5 M NaCl. Four additions of ascorbate (3 iM) were made to the sample mixture to accelerate the reaction. The spectrum was recorded after 120 min with a correction for the base line. From Henry and Monny, 1977, with permission from the American Chemical Society.

Irreversible reaction of [18] iodine with acetylsalicylic acid, aethaverine, amidopyrine, ascorbic acid, benzo-caine, quinine, dihydrocodeine, fluorescein, glycine, hydrocortisone acetate, isoni-azid, metamizole, papaverine, paracetamol, phenacetin, phenol-phthalein, piperazine, resorcinol, salicylic acid, salicylamide, sulfaguanidine, thymol, triethanolamine, tris buffer detection by reaction chromatography... 

The first step in the analysis is extraction of the tobacco with buffer solution (pH 4.5) containing 20 mM ascorbic acid. The nitrosamines are then concentrated by partition with dichloromethane, and a chromatographic clean-up on alumina. In the final step, the concentrate is analyzed by GC-TEA and confirmation of the nitrosamines is obtained by GC-MS (O. If isolated amounts of the nitrosamines are below levels needed for GC-MS confirmation, we employ confirmatory techniques proposed by Krull et a. ( 5). 

Nonvolatile Nitrosamines In Tobacco. A method which we developed several years ago for the analysis of tobacco-specific nitrosamines (TSNA 31) involves extraction of tobacco with buffered ascorbic acid TpH 4.5) followed by partition with ethyl acetate, chromatographic clean-up on silica gel, and analysis by HPLC-TEA (Figure 9). Results obtained with this method for a large spectrum of tobacco products (Table IV), strongly support the concept that the levels of nitrate and alkaloids, and especially the methods for curing and fermentation, determine the yields of TSNA in tobacco products. Recent and as yet preliminary data from snuff analyses indicate that aerobic bacteria play a role in the formation of TSNA during air curing and fermentation. 

Solutions. Solutions of ferrlcyanlde (Baker Chemical Co., Phllllpsburg, NJ) were prepared In 1.0 M KCl (Mallnckrodt, Paris, KY). Ascorbic acid solutions were prepared In 0.1 H phosphate buffer adjusted to pH 2.0. All solutions were prepared with triple distilled water. Solution preparation precautions have been previously described (15). 

Neomycin phosphotransferase II (NPTII) extraction from cotton leaves and cottonseed. The extraction buffer consists of 100 mM Tris, lOmM sodium borate, 5mM magnesium chloride, 0.2% ascorbate and 0.05% Tween 20 at pH 7.8. The frozen leaf sample is homogenized in cold (4 °C) buffer. An aliquot of the homogenate is transferred to a microfuge tube and centrifuged at 12 000 g for 15 min. The supernatant is diluted and assayed directly by ELISA. 

Procedure The Ascorbate peroxidase (EC 1.11.1.7) activity can be obtained by measuring the oxidation of ascorbate in the presence of H202. Grind the algal sample in liquid nitrogen and extract in 2.5 ml 50 mM potassium phosphate buffer (pH 7.0) containing 10% (w/v)... 

Basic procedure (ACW kit) Mix 1500 pL of ACW reagent 1 (diluter) with 1000 pL of ACW reagent 2 (buffer) and 25 pL of photosensitizer reagent (lumi-nol based). Start measurement after brief vortexing. Assayed solution (or control) is added before addition of photosensitizer reagent. Volume of ACW reagent 1 is reduced by the volume of assayed plasma sample. Standard substance ascorbic acid. Duration of measurement 2-3 min. Measured parameter effective lag phase = lag-phase sample - lag-phase blank. Assayed amount of human blood plasma 2 pL. 

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