Concentration Of Tetrabutylammonium Hydroxide Research Articles

Pretreatment of corn stalk by low concentration tetrabutylammonium hydroxide aqueous solution at low temperature (20–80 °C)

Corn stalk was pretreated by aqueous tetrabutylammonium hydroxide to enhance enzymatic hydrolysis process. The effects of temperature (20–80 °C), concentration of tetrabutylammonium hydroxide (10–40 wt%), time (5–60 min) and ratio of solid to liquid (1:4–1:8, wt/wt) were investigated to find the optimal operational condition, which was determined as 20 °C, 30 wt%, 20 min and 1:5 respectively. This was a quite mild pretreatment condition resulting in 68.17% enzymatic hydrolysis sugar yield and the removal rate of hemicelluloses and lignin were 23.5% and 31.5% respectively. Besides, the microstructure and crystal structure changes of raw material and pretreated samples were analyzed by scanning electron microscope and X-ray diffraction respectively. Finally, a possible mechanism of pretreatment process was put forward based on the comprehensive analysis.

Aligned Inclusion of n‐Propionic Acid Tethering Hemicyanine into Silica Zeolite Film for Second Harmonic Generation

Organization of dipolar second-order nonlinear optical (NLO) dyes in uniform orientations is not only an interesting subject by itself but also an essential step towards a successful application of the dyes for second-harmonic generation (SHG). Zeolites have been tested as the hosts for aligned inclusion of dipolar organic NLO dyes. However, the previously tested dyes have been limited to p-nitroaniline and those that have low molecular second-order hyperpolarizability constants (b ∼ 3 × 10 electrostatic units (esu; 1 esu∼ 3.33564 × 10 C)) and the zeolites have mostly been limited to powders. As a result, the potential of NLO dye-including zeolites as practically viable SHG materials has not been fully explored. It is therefore necessary to develop methods to include high-b dipolar NLO dyes with a high degree of uniform orientation (DUO) into transparent zeolite films with uniformly oriented channels. We recently reported that hemicyanine (HC) with an octadecyl tail (HC-18; Scheme 1A; b ≥ 77 × 10 esu) preferentially enters the vertically aligned channels of transparent silicalite (SL) films (thickness 400 nm) supported on glass (SL/Gs) with the octadecyl chain first because of the hydrophobic interaction between the long alkyl chain and the silicalite channel. Interestingly, despite the fact that the average number of incorporated molecules (NC) in each 400 nm long channel was only 3.5, the measured second-harmonic intensity (I2x) was remarkably high, equivalent to 7.9 % of that of 3 mm thick quartz (along the y-axis). Indeed, the measured d33 value (a tensor component of the quadratic nonlinear susceptibility) was 5.3 pm V, which was ca. 18 times larger than the d11 value of quartz (0.3 pm V ), and was even larger than the d33 value of potassium dihydrogen phosphate (KDP; ca. 3 pm V), one of the widely used NLO materials, by roughly a factor of two. Although HC-18-incorporating SL/Gs were still unusable for practical applications because of the very small NC of HC-18 in the channels, the above result clearly demonstrated the potential of NLO-dye-incorporating SL/Gs, as they could be developed into practically useful SHG films by increasing the NC. In the case of HC, it was found that the NC increases substantially upon decreasing the alkyl chain length. Unfortunately, however, the decrease in the alkyl chain length led to a sharp decrease in I2x because of a larger negative effect caused by the decrease in the DUO than the positive effect caused by the increase in the NC. Thus, increasing both the NC and DUO has been a big challenge. We now report that the DUO of HC with a propionic acid tail (commonly designated as either HC-PA or HC-2-CO2H; Scheme 1B) in SL channels increased by a factor of about four when the dye was included in SL/Gs in the presence of tetrabutylammonium hydroxide (TBAOH), leading to a ca. 16-fold increase in I2x. The procedures for preparation of HC-PA and SL/Gs are described in the Experimental Section. The scanning electron microscope (SEM) image of a typical SL/G is shown in Figure S1 in the Supporting Information. HC-PA was introduced into SL/G from the aqueous solutions (20 mL) of HC-PA (0.1 mM) and TBAOH (see Experimental for detail); the concentration of TBAOH ([TBAOH]) varied from 0.0 to 3.0 mM. HC-PA had a maximum absorption (kmax) at 460 nm in the aqueous solution regardless of the [TBAOH] (Supporting Information Fig. S2), indicating that the base did not affect the C O M M U N IC A TI O N

Determination of sulfur oxides formed during the S(IV) oxidation in the presence of iron.

The reaction products (i.e., sulfate (SO4(2-)) and dithionate (S2O6(2-))) of S(IV) oxidation in the presence of iron(III) under different experimental conditions were investigated. Ion-interaction chromatography was used for the separation of sulfate and dithionate using tetrabutylammonium hydroxide (TBAOH) as an ion-pair reagent. The chromatographic method was optimized by varying the composition of the mobile phase (i.e., concentration of TBAOH, acetonitrile and Na2CO3) and by varying the flow rate of the mobile phase. The method was successfully applied to the determination of dithionate formed during the S(IV) oxidation in the presence of Fe(III). In air-saturated solutions sulfate was observed as the only product, while in N2-saturated solutions dithionate was also determined, but it is the minor reaction product and represents about 4% of the total amount of oxidized HSO3- under the studied conditions.

Cathodic stripping analysis of DNA/RNA bases in nonaqueous media

AbstractThe methods for the determination of nucleic acid bases by differential pulse cathodic stripping voltammetry in dimethyl sulfoxide are proposed and developed. One method uses mercury drop or film electrodes. The required anion is produced by the deprotonation of the parent molecule by added tetrabutyl‐ammonium hydroxide (TBAOH). Optimization of the method is discussed. The effects of deposition potential or time, scan rate, pulse height, TBAOH concentration, and other experimental parameters are examined. Included are the results of the determinations of thymine, uracil, cytosine, adenine, and guanine. The second method uses a mercury‐film rotating ring‐disk electrode. The anion, produced electrochemically at the disk held at a negative potential, is swept to the ring and deposited at a suitable, more positive potential. Detection limis for nucleic acid bases are 10−8 to 10−9 M.