• Mass Spectrometry Letters
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• 제14권2호
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• pp.48-55
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• 2023

This study compares the efficiency of weak acid hydrolysis (WAH) using formic acid (FA) and hydrochloric acid (HCl) in the analysis of myoglobin peptides. WAH using 2% and 5% formic acid resulted in the identification of 32 peptides, with varying degrees of cleavage at the C-terminus of aspartic acid residues. HCl WAH with different concentrations demonstrated an increase in the total number of identified peptides but a decrease in fully cleaved peptides as the HCl concentration increased. Notably, deamidation was observed during HCl WAH but not in FA WAH. The addition of HCl WAH after FA WAH provided a similar pattern to HCl WAH, with slightly higher levels of hydrolysis. These findings highlight distinct cleavage patterns and deamidation effects between FA and HCl in the context of WAH.

• 한국식품영양과학회지
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• 제27권6호
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• pp.1110-1116
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• 1998

To determine the optimum conditions for the enzymic hydrolysis against wheat gluten of high con centrations (6~14%, w/w, protein), a hydrolysis system combining weak acid pretreatment and enzymic hydrolysis was investigated. Alcalase showed the highest DH(degree of hydrolysis) of the tested proteases. After hydrolysis by alcalase, subsequently peptidases were applied for the better DH of the wheat gluten hydrolyzate. Peptidase NP2 showed the highest DH of the tested peptidases, but flavour zyme was shown for the lowest bitter taste of the resulting hydrolyzate. In order to minimize aggregation or gelling at higher initial substrate concentration during heat treatment, wheat gluten suspension was pretreated with possibly low concentrations of hydrochloric acid at 105oC for 1 hour, and then enzy matically hydrolysed with alcalase and subsequently with flavourzyme. Each required minimum concen tration of hydrochloric acid in the wheat gluten suspension of 6, 8, 10, 12, and 14%(w/w, protein) was 0.10, 0.15, 0.20, 0.225, and 0.275N, respectively. After the subsequent enzymic treatment by alcalase and peptidase NP2 for 24 hrs, the nitrogen solubility in the final wheat gluten hydrolysates was increased to 94.9, 86.4, 85.3, 89.3 and 95.0%, and their amino nitrogen content was increased to 2.87, 5.68, 7.34, 9.71 and 12.50mg/m, respectively.

• Korean Chemical Engineering Research
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• 제57권2호
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• pp.164-171
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• 2019

The protonation parameters, dissociation constants ($pK_{BH^+}$) of conjugate acid, slope values (m, ${\phi}$ and $m^*$) and correlation coefficients (r) of hydroxamic acids were determined by Hammett acidity function method, Bunnett-Olsen method and excess acidity method in hydrochloric and perchloric acid solutions. Effect of acid concentration on partition and percentage protonation was also studied. $pK_{BH^+}$ values show that hydroxamic acids do not behave as Hammett bases, but hydroxamic acids behave as weak bases in strong acidic solutions. The values of $pK_{BH^+}$ obtained through Bunnett-Olsen method and excess acidity method were compared with the Hammett acidity function. ChemAxon's MarvinSketch 6.1.5 software was also used for determining $pK_a$, pI and microspecies distribution (%) of hydroxamic acids with pH. Hydrogen donor and acceptor values and logD were also obtained. The results show that N-p-chlorophenyl-4-bromobenzohydroxamic acid has the highest $pK_a$ and lowest logD values. On the contrary, N-phenyl-3,5-dinitrobenzohydroxamic acid has lowest the $pK_a$ and highest logD values.

• 대한금속재료학회지
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• 제56권12호
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• pp.870-877
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• 2018

Cyanex 272 shows the highest separation factor for the rare earth elements from hydrochloric acid solution among the organophosporus acidic extractants, D2EHPA and PC 88A. Solvent extraction of Tb(III) from weak hydrochloric acid solution with an initial pH 3 to 6 was compared with Cyanex 272, its mixture with Alamine 336, and ionic liquid with Aliquat 336. The solvent extraction reaction of Tb(III) using Cyanex 272 was the same as that of light rare earth elements. Synergism was observed for the extraction of Tb(III) by the mixture with Alamine 336 when the initial concentration ratio of Cyanex 272 to Alamine 336 was higher than 5. Use of the ionic liquid led to a great increase in the extraction percentage of Tb(III) from the same initial extraction conditions. While the equilibrium pH of the mixture was always lower than the initial pH, under some conditions extraction with the ionic liquid resulted in a higher equilibrium pH than the initial pH. The loading capacity of the mixture and the ionic liquid was the same and 2.6 times larger than that using Cyanex 272 alone. Ionic liquid was recommended as a suitable extractant for the extraction of Tb(III) from hydrochloric acid solution based on the ease of handling and higher extraction percentage.

• Membrane and Water Treatment
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• 제2권3호
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• pp.187-205
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• 2011

The electric transport of the mixture of hydrochloric and phosphoric acids through strong base (Neosepta ACM) and weak base (Selemion AAV) anion-exchange membranes was investigated. The instantaneous efficiency of HCl removal from the cathode solution, $CE_{Cl}$, with and without $H_3PO_4$ was determined. It was found that $CE_{Cl}$ was 0.8-0.9 if the number of moles of elementary charge passed through the system, $n_F$, did not exceed ca. 80% of the initial number of HCl moles in the cathode solution, $n_{Cl,ca,0}$. The retention efficiency of $H_3PO_4$ in that range was close to one. The transport of acid mixtures was satisfactorily described by a model based on the extended Nernst-Planck and Donnan equations for $n_F$ not exceeding $n_{Cl,ca,0}$. Among the tested model parameters, most important were: concentration of fixed charges, the porosity-tortuosity coefficient, and the partition coefficient of an undissociated form of $H_3PO_4$. For the both membranes, the obtained optimal values of fixed charge concentration, $\bar{c}_m$, were up to 40% lower than the literature values of $\bar{c}_m$ obtained from the equilibrium measurements. Regarding the $H_3PO_4$ equilibria, it was sufficient to consider $H_3PO_4$ as a monoprotic acid.

• 한국분말재료학회지
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• 제25권5호
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• pp.390-394
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• 2018

Metallic tantalum powder is manufactured by reducing tantalum oxide ($Ta_2O_5$) with magnesium gas at 1,073-1,223 K in a reactor under argon gas. The high thermodynamic stability of magnesium oxide makes the reduction reaction from tantalum oxide into tantalum powder possible. The microstructure after the reduction reaction has the form of a mixture of tantalum and magnesium oxide, and the latter could be entirely eliminated by dissolving in weak hydrochloric acid. The powder size in SEM microstructure for the tantalum powder increases after acid leaching in the range of 50-300 nm, and its internal crystallite sizes are observed to be 11.5 to 24.7 nm with increasing reduction temperatures. Moreover, the optimized reduction temperature is found to be 1,173 K as the minimum oxygen concentration is approximately 1.3 wt.%.

• Korean Chemical Engineering Research
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• 제57권6호
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• pp.749-757
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• 2019

Methyltrimethoxysilane (MTMS)과 trimethylethoxysilane (TMES)을 출발물질로 사용하여 여러 종류의 용매에 용해시킨 후 다양한 종류의 촉매를 사용해 물과의 가수분해 및 중축합반응을 진행시켜 비불소계 발수 코팅 용액을 제조하였다. 또한 이 코팅 용액을 냉연 강판 위에 스핀 코팅하고 열 경화시켜 발수 코팅 도막을 제조 하였다. 이 과정 중 촉매와 용매의 종류 변화가 생성된 코팅 도막의 발수성에 미치는 영향을 연구하였다. 강산인 염산과 질산을 촉매로 사용한 경우에는 용액 내에 siloxane polymer들의 응집이 발생한 흰색의 불투명 상태를 나타냈다. 반면에 약산인 아세트산, 인산과 옥살산을 사용한 경우에는 투명하고 침전이 없는 안정한 용액 상태를 보였다. 이로 인해 강산인 염산과 질산을 사용한 경우의 코팅 도막의 접촉각은 각각 $58^{\circ}$와 $92^{\circ}$로 낮은 발수성을 보인 반면에 약산인 아세트산, 인산과 옥살산으로 제조된 경우에는 각각 $101^{\circ}$, $103^{\circ}$, $116^{\circ}$의 접촉각을 보여 높은 발수성을 나타내었다. 또한 이소프로판올과 에탄올을 용매로 사용한 경우에는 용액 내에서 siloxane polymer들의 응집이 일어나 불투명한 침전이 발생한 상분리 현상을 보인 반면 메탄올, 에틸아세테이트와 메틸에틸케톤을 용매로 사용한 경우에는 투명하고 침전이 없는 안정된 상태를 나타내었다.

• 한국표면공학회지
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• 제32권3호
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• pp.410-415
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• 1999

The adhesion strength of sputtered copper films to Inconel substrates has been studied using the scratch test. The effects of substrate treatments before deposition such as chemical or ion bombardment etching were investigated by means of a mean critical load derived from a Weibull-like statistical analysis. It was found that the mean critical load was very weak unless the amorphous layer produced by mechanical polishing on the substrate surface was eliminated. Chemical etching in a nitric-hydrochloric acid bath was shown to have practically no effect on the enhancement of the adhesion. In contrast, the addition in this bath of nickel and copper sulphates allowed removal of the amorphous layer and an increase in the values of the mean critical load. However, it was observed that excessive chemical etching could cancel out the mean critical load enhancement. The results obtained in the case of ion bombardment etching pretreatments could be far higher than those obtained with chemical etching. Moreover, for a sufficiently long period of ion bombardment etching, the adhesion strength was so high that it was impossible to observe evidence of an adhesion failure.

• 자원리싸이클링
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• 제29권5호
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• pp.55-63
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• 2020

묽은 염산용액에서 이온성액체에 의한 코발트(II)와 니켈(II)의 분리를 조사하기 위해 이온성액체의 종류와 농도 및 수상의 초기 pH를 변화시켜 추출실험을 수행했다. 본 논문에서는 유기인산(D2EHPA, PC88A, Cyanex 272, Cyanex 301)을 Aliquat 336과 반응시켜 제조한 이온성액체와 Aliquat 336의 염소이온을 SCN과 치환한 이온성액체를 사용했다. 세 종류의 이온성액체(ALi-D2, ALi-PC, ALi-CY272)에 코발트(II)가 니켈(II)보다 추출이 잘 되었으며 평형 pH가 초기 pH보다 높았다. ALi-CY301의 경우 코발트(II)와 니켈(II)의 선택도는 추출조건에 의존했다. 또한 상기 이온성액체에 TBP의 첨가가 두 금속의 추출에 미치는 영향도 조사했다. 추출제로 ALi-SCN를 사용하는 조건에서 코발트(II)가 선택적으로 추출되어 두 금속을 완전히 분리하는 것이 가능했다.

• 한국축산식품학회지
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• 제37권5호
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• pp.708-715
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• 2017

The acid pretreatment of collagen molecules disrupts their crosslinks and assists in the release of acid-soluble proteins, fats, and other components. Generally, to achieve optimum extraction efficiency, strong acids may be used at a lower acid concentration compared to weak acids. This study aimed to determine the yield and physicochemical properties of gelatins extracted from buffalo hides pretreated with different acids. Hides were extracted with hydrochloric, citric, and acetic acids at concentrations of 0.3, 0.6, 0.9, 1.2, and 1.5 M. A completely randomized design and the least significant difference test were used in the experimental design, and all measurements were performed in triplicate. The highest yield (29.17%) was obtained from pretreatment with 0.9 M HCl. The gel strength did not differ significantly (p>0.05) according to acid type (280.26-259.62 g Bloom), and the highest viscosity was obtained from the 0.6 M citric acid pretreatment. All the gelatins contained ${\alpha}$- and ${\beta}$-chain components and several degraded peptides (24-66 kDa). The color and Fourier-transform infrared spectrum of the gelatin extracted using 0.9 M HCl were similar to those of commercial bovine skin gelatin. In general, the physicochemical properties of the gelatin complied with the industry standard set by the Gelatin Manufacturers Institute of America, revealing that buffalo hide could serve as a potential alternative source of gelatin.