Tartrate buffer

Pb2+ Tartrate buffer or chloride solution (solubility limits the amount of lead to less than 50 mg per 100 mL) 2 A 2-3 V... 

Only in a tartrate buffer is the rate appreciable and it is significant that only in this buffer does the normally diamagnetic Mo(V) display esr signals g = 1.937 and g = 1.945) indicating the presence of monomeric Mo(V) which is regarded as the active species in the proposed mechanism, viz. 

Acridinium esters Acridinium- H202 Tartrate buffer (pH 2.8)... 

For pH and thermoinactivated samples, the conditions were equal to those in the standard assay, except that the concentration of tartrate buffer, pH 3.0, was 0.3 M. 

To study the effect of pH and temperature, 0.25 ml of the lignin peroxidase diluted with water was mixed with 0.75 ml of buffer, pH 3.0 - 7.0 and incubated at temperatures of30- 70°C. The protein concentration of the incubation mixture was 50 ig/ml. After various incubation times (0 - 27 h) the inactivation was stopped by adding 9 ml of cold 0.33 M tartrate buffer, pH 3.0. 

VAO activity was measured with a mixture of 1 mM veratryl alcohol, 250 mM sodium tartrate buffer, pH 5.0 and enzyme. Oxidation to vera-... 

Oxygen uptake during substrate oxidation was measured with a Clark oxygen electrode (Rank Brothers, Cambridge, U.K.) at room temperature with 1 mM substrate in 0.25 mM sodium tartrate buffer, pH 3.0 (3 mL). Rates are expressed relative to veratryl alcohol oxidation. 

The reaction of Mo204+ with N03 in tartrate buffer (which is capable of coordinating to the Mo2) at pH2.2-3.5 has also been studied.144 The kinetics give a half-order dependence on... 

Dimethylglyoxime has long been used as a precipitant for nickel and palladium. Nickel is usually precipitated from an ammoniacal tartrate buffer of pH about 8. Under these conditions iron and many other metals, even in large amounts, do not interfere. Palladium is precipitated from hydrochloric or sulfuric acid solution. Nioxime ° (1,2-cyclohexanedionedioxime) has the advantage of being more soluble in water than dimethylglyoxime and therefore less subject to coprecipitation with the metal chelate. 

As soon as the grape has been picked from the plant, the seeds and skins of 50 berries are separated from the others parts of the berry, separately immersed in two solutions of 50 mL tartrate buffer solutions containing 1 g/L SO2 and immediately frozen. Before analysis, samples are heated at room temperature and so kept for 4 h in order to allow the extraction to occur. Extracts are then homogenized and centrifuged, the supernatant is transferred in a 100-mL volumetric flask, pellets are re-suspended twice in 15-20 mL of tartrate buffer and, after centrifugation, the liquid phases are collected in the same volumetric flask and the final volume is adjusted to 100 mL by tartrate buffer. 

Data of polyphenols extracted from skins of Pinot noir and Barbera grapes using ethanol/H20/HCl 70 30 1 (v/v/v), tartrate buffer-12% ethanol containing Na2S205 2g/L and ethanol/H20/acetic acid 70 30 1 (v/v/v) solutions, are reported in Tables 2.2 and 2.3, respectively. 

HPLC analysis can be performed by direct injection of the tartrate buffer extract. The chromatographic peaks of catechin and epicatechin are well resolved, but an overlapping of procyanidins and epicatechin gallate with other compounds, may occur. To improve the separation among them, a fractionation of the sample on a C18 cartridge can be performed 5 mL of extract are added of 15 mL H2S04 5 x 10 3M and passed... 

Table 2.13 Hydroxystilbene contents determined in a tartrate buffer grape skins extract (Grippi, personal communication).

Table 1. Copigment effect on Malvidin-3-Glucoside in tartrate buffer (pH 3.2) solutions containg various amount of copigment (r is the copigment/malvidin ratio). A and X are the maximum absorbance and corresponding wavelength in the presence of copigment (Ao and Xo without).

Table 2. Hyperchromic effect (measured at 523 nm) of grape seed tannin fraction on MaIvidin-3-Glucoside in tartrate buffer (pH 3.5). mOP is the mean degree of polymerization measured by diioacidolysis. r the molar ratio between tannin and anthocyanin (a fixed concentration of 1 g/1 of tannin was used). T is the absorbance of tannin solution (control) at 523nm.

Silver ions yield an intensely purple complex with sodium 2-(8-hydroxyquinolin-5-ylazo)benzoate (29) in tartrate buffer at pH 5.2 to 6.1 A 525 nm, e 36500101. A method involving a large multiplication factor consists of decomposition of ferrocyanide complex ions [Fe(CN)6]4 with Ag(I) to give [Ag(CN)2]. In the presence of crystal violet (CV,... 

Mobile phase MeCN buffer 22.5 77.5 (Buffer was 5 mM pH 3.0 tartrate buffer containing 5 mM sodium 1-butanesulfonate and 50 mM sodium sulfate.)... 

Dimethoxybenzene, magnesium monoperoxyphthalate and iron(lll) meso-tetrakis-(2,3,5,6-tetrafluorophenyl)tetrasulphonatoporphyrin in the proportions (1 3 0.01) in acetonitrile/tartrate buffer (pH3) when kept at 20°C for 1 hour afforded 2-methoxybenzo-1,4-quinone in 95% yield (ref.143). 

One method that is httle-known, or at least rarely used to avoid this total acidity imbalance, consists of partially or completely eliminating the malic acid by chemical means, using a mixture of calcium tartrate and calcium carbonate. This method precipitates the double calcium salt, tartromalate, (Section 1.4.4, Figure 1.9) and is a very flexible process. When the malic acid is partially eliminated, the wine has a buffer capacity based on those of both tartaric and malic acids, and not just on that of the former. Tartrate buffer capacity is less stable over time, as it decreases due to the precipitation of monopotassium and calcium salts during aging, whereas the malic acid salts are much more soluble. 

It has been demonstrated that the half-wave potential for the reduction of Ti(IV) to Ti(III) is -0.81 V (against the standard calomel electrode) in 0.1 M HCl [27]. The further reduction of Ti(III) to Ti(ll) can be observed in alkaline media, but this reaction has no useful analytical significance. In these methods, oxalate, tartrate, or citrate buffer systems are used as supporting electrolytes to prevent the hydrolytic precipitation of hydrated titanium oxides. In the presence of tartrate buffer, well defined waves are obtained only at pH values less than 2, or between 6 and 7. The Ti(lV)-Ti(III) couple is reversible only in tartrate buffer at pH values less than 1. 

Other applications of CE to analyze food additives include the determination of vitamin C and preservatives (benzoate and sorbate) by both conventional CE and microchip electrophoresis with capacitively coupled contactless conductivity detection. The separation was optimized by adjusting the pH value of the buffer and the use of hydroxypropyl- -CD (HP- -CD) and CTAB as additives. For conventional CE, optimal separation conditions were achieved in a histidine/tartrate buffer at pH 6.5, containing 0.025% HP-f)-CD and 0.25 mM CTAB with a LOD ranging from 0.5 to 3 mg/L, whereas a histidine/tartrate buffer with 0.06% HP-fl-CD and 0.25 mM CTAB gave a LOD ranging from 3 to 10 mg/mL. By using a microchip electrophoresis format, a considerable reduction of analysis time was accomplished. ... 

CgH,kC-COOH, CgH,COOH Tartrate buffer Tartaric acid... 

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