• Clean Technology
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• v.20 no.2
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• pp.108-115
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• 2014

Various metal chlorides and acid catalysts in ionic liquid solvent were investigated to directly convert cellulose into 5-hydroxymethylfurfural (5-HMF). Metal chlorides containing Sn(II), Zn(II), Al(III), Fe(III), Cu(II), and Cr(III) were used and acidic ionic liquid immobilized on silica gel as an acid catalyst and commercial acid catalysts (sulfuric acid, chloric acid, Amberlyst-15,DOWEX50x8) were used for comparison studies. The acid strength and amount of acid catalysts were probed with Hammett indicator. The selectivity and yield of 5-HMF were determined with reaction temperature, reaction time and catalyst ratio. A catalyst containing $CrCl_3-6H_2O$ and $SiO_2-[ASBI]HSO_4$ showed the highest selectivity and it was found that this catalyst had higher activity than commercial solid acid catalysts such as Amberlyst-15 and DOWEX50x8. The selectivity of 5-HMF appeared to be mainly dependent on the acid strength and catalyst ratio, it was found that levulinic acid was produced from 5-HMF by rehydration.

• Korean Journal of Food Science and Technology
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• v.11 no.3
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• pp.171-175
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• 1979

Thermal properties of crude papain and crude peroxidase from domestic papaya were investigated. The crude extract of papaya was inactivated at the temperature range of $60^{\circ}{\sim}90^{\circ}C$ at pH 7.0 and the rest of the activities of papain and peroxidase were determined, respectively. The heat inactivation of papain and papaya peroxidase was biphasic at low temperature. For the thermal inactivation of papain extract, the enthalpy of activation was 91.4 kJ/mol, the entropy of activation, -49.6 J/mol K, and the free energy of activation, 108.5 kJ/mol. The activation energy for the inactivation of papaya peroxidase was 168.5 kJ/mol, the entropy of activation, $200.4\;J/mol{\cdot}K$ and the free energy of activation, 99.7 kJ/mol. The thermal stability of papain showed that it has a possibility for use as a meat tenderizer. It was also discussed that papaya peroxidase could be more suitable as a biochemical criteria for heat treatment than papaya catalase.

• Economic and Environmental Geology
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• v.51 no.6
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• pp.509-520
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• 2018

Alkalinity is one of the basic variables, which determine geochemical characteristics of natural waters and participate in processes changing concentrations of various contaminants either directly or indirectly. However, not a few laboratories and researchers of Korea still use alkalinity-measurement methods not appropriate for groundwaters, and which becomes one of the major reasons for the poor ion balance errors of the geochemical analysis. This study was performed to review alkalinity-measurement methods, to discuss their advantages and disadvantages, and, thus, to help researchers and analytical specialists in analyzing alkalinity of groundwaters. The pH-titration-curve-inflection-point (PTC-IP) methods, which finds the alkalinity end point from the inflection point of the pH titration curve are revealed to be most accurate. Gran titration technique among them are likely to be most appropriate for accurate estimation of titrant volume to the end point. In contrast, other titration methods such as pH indicator method and pre-selected pH method, which are still commonly being used, are likely to cause erroneous results especially for groundwaters of low ionic strength and alkalinity.

• KOREAN JOURNAL OF PACKAGING SCIENCE & TECHNOLOGY
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• v.28 no.1
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• pp.47-53
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• 2022

Recently, intelligent packaging of foods has been increasingly developed in response to the growing interest of consumers in checking food quality. Indicators, an important element in intelligent packaging, change color to detect specific substances or indicate food quality changes. Gas indicators can be built into food packaging to detect volatile substances that are released when food quality changes. Ethylene gas is produced as climacteric fruits ripen. Climacteric fruit ripening results from a rapid increase in ethylene production and respiration. In the case of packaged fruits, the ethylene gas concentration in the headspace is closely related to the ripeness of each fruit variety. If an ethylene gas indicator that can be used in fruit packaging is available, the consumer will be able to eat the fruit at the optimal time. In this paper, the characteristics and pros and cons of the ethylene gas indicators developed so far were analyzed by reviewing various types of indicators such as metal reduction-based indicator, fluorescence-based indicator, pH indicator-based indicator, and liposome-based indicator.

• Analytical Science and Technology
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• v.19 no.1
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• pp.107-114
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• 2006

Early diagnosis and medical intervention are critical for the treatment of patients with metabolic disorders. A rapid analytical method was developed for simultaneous quantification of organic acids and amino acids in urine without labor-intensive pre-extraction procedure showing high sensitivity and specificity. A new method consisted of simple two-step trimethylsilyl (TMS)-trifluoroacetyl (TFA) derivatization using GC/MS-selective ion monitoring (SIM). Filter paper urine specimens were dried under nitrogen after being fortified with internal standard (tropate) in a mixture of distilled water and methanol. Methyl orange was added to the residue as indicator reagent. Silyl derivative of carboxylic functional group was followed by trifluoroacetyl derivative for amino functional group. N-methyl-N-(trimethylsilyl-trifluoroacetamide) and N-methyl-bistrifluoroacetamide were consecutively added and heated for 15-20 min at $65^{\circ}C-70^{\circ}C$, for TMS-TFA derivative, respectively. This reactant was analyzed by GC/MS-SIM. Linear dynamic range showed 0.001-50 mg with the detection limit of (S/N=3) 10-200 ng, and the quantification limit of 80-900 ng in urine. Correlation coefficient of regression line was 0.994-0.998. When the method was applied to the patients 'urine, it clearly differentiated the normal from the patient with metabolic disorder. The study showed that the developed method could be the method of choices in rapid and sensitive screening for organic aciduria and amino acidopathy.

• KOREAN JOURNAL OF CROP SCIENCE
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• v.52 no.2
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• pp.213-219
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• 2007

It has been well established that aluminum (Al) inhibits root tip growth rapidly in acid soil. We report the correlation between Al induced growth inhibition and impaired $H^+-flux$ in mung bean (Vigna radiate L. cv. Kumsung). The root growth inhibition was dependent on Al concentration (0, 10, 25, 50, $100{\mu}M$) and exposure time (12 and 24 h). Using Hematoxylin staining, it was observed that the root damage was occurred preferentially in regions with high Al accumulation. Using the pH indicator, it was shown that the surface pH of root tip was strongly alkalized in the control whereas changed only slightly in the $50{\mu}M$ Al-treated root. The $H^+-ATPase$ activity of plasma membrane vesicles was inhibited by 56% in the Al-treated roots compared to control root. Decrease in the amount of the plasma membrane $H^+-ATPase$ (100 kDa) translation in the plant roots under Al stress was demonstrated by Western blot analysis. These results indicate that the dynamics of $H^+-flux$ across the root tip play an important role in root growth under Al stress.

• Journal of the Korean Chemical Society
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• v.54 no.5
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• pp.556-566
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• 2010

A new kinetic spectrophotometric method is developed for the measurement of Mn(II) in natural water samples. The method is based on the catalytic effect of Mn(II) with the oxidation of Gallocyanin by $KIO_4$ using nitrilotriacetic acid (NTA) as an activation reagent at 620 nm. The optimum conditions obtained are $4.00{\times}1^{-5}\;M$ Gallocyanin, $KIO_4$, $1.00{\times}10^{-4}\;M$ NTA, 0.1 M HAc/NaAc buffer of pH = 3.50, the reaction time of 5 min and the temperature of $30^{\circ}C$. Under the optimum conditions, the proposed method allows the measurement of Mn(II) in a range of $0.1\;-\;4.0\;ng\;mL^{-1}$ and with a detection limit of down to $0.025\;ng\;mL^{-1}$. The recovery efficiency in measuring the standard Mn(II) solution is in a range of 98.5 - 102%, and the RSD is in a range of 0.76 - 1.25%. The newly developed kinetic method has been successfully applied to the measurement of Mn(II) in both some environmental water samples and certified standard reference river water sample, JAC-0031 with satisfying results. Moreover, few cations and anions interfere with the measurement of Mn(II). Compared with the other catalytic-kinetic methods and instrumental methods, the proposed kinetic method shows fairly good selectivity and sensitivity, low cost, cheapness, low detection limit and rapidity. It can easily and successfully be applied to the real water samples with relatively low salt content and complex matrices such as bottled drinking water, cold and hot spring waters, lake water, river water samples.