• Journal of Food Hygiene and Safety
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• v.37 no.4
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• pp.232-237
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• 2022

The present study investigated the bactericidal effects of chlorine dioxide (CD) and electrolyzed water (EW) on pathogenic bacteria, such as Bacillus cereus, Staphylococcus aureus, Salmonella Typhimurium, and Escherichia coli O157:H7, by treatment them with CD and EW, respectively, for 0, 2, 4, 6, 8, and 10 min. Additionally, the sensitivities of Gram-positive (B. cereus and S. aureus) and Gram-negative (S. Typhimurium and E. coli O157:H7) to CD and EW were compared, respectively. In CD, the D-values for B. cereus, S. aureus, S. Typhimurium, and E. coli O157:H7 were 1.85±0.64, 2.06±0.85, 2.26±0.89, and 2.59±0.40 min, respectively. In EW, the D-values for B. cereus, S. aureus, S. Typhimurium, and E. coli O157:H7 were 2.13±0.32, 1.64±0.64, 1.71±0.32, and 1.86±0.36 min, respectively. All strains decreased consistently for 10 min in both CD and EW. However, the D-values of each bacterial species did not differ significantly between CD and EW (P>0.05). When comparing the bactericidal effect of CD and EW, no difference in D-value was observed, even though the pH and available chlorine concentration of CD were significantly lower than those of EW. These data could be used for the application of CD and EW in the food industry, considering characteristics such as the selection of optimal disinfectants, determination of optimal concentrations, and sensitivity to disinfection targets.

• Journal of the Korean Chemical Society
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• v.13 no.4
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• pp.281-287
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• 1969

Rate constans for the chloride exchange of some arylmethylchloride in dry acetone have been determined, and activation parameters have been evaluated. The reactivities of substates are explained with perturbational molecular orbital (PMO) method and HSAB principle. It was found that carbon-chlorine resonance integral at the transition state is a out 67% of ${\beta}$, the carbon-carbon resonance integral.

• Proceedings of the Korean Institute of Building Construction Conference
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• 2019.05a
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• pp.238-239
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• 2019

In this study, it was intended to confirm the possibility of using the Durometer in estimating the setting time by comparing the Proctor penetration resistance with the Durometer type A of hardness in concrete substituting CBS Dust. With the hardness of Durometer type A, it is expected to be used conveniently in the field of practice as it is determined to be about 18 HD for the initial determination and 31 HD for the end measurement.

• Korean Journal of Food Science and Technology
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• v.49 no.6
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• pp.591-598
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• 2017

This study aimed to evaluate the measurement uncertainty for the quantitative determination of chlorite and chlorate in ready-to-eat fresh-cut vegetables using ion chromatography with a hydroxide-selective column. One gram of the homogenized sample in deionized water was sonicated and centrifuged at 8,500 rpm. The supernatant was purified by passing it through a Sep-Pak tC18 cartridge, followed by chromatographic determination using a Dionex IonPac AS27 column. The linearity of the calibration curves, recovery, repeatability, and reproducibility of the method were satisfactory. The method detection limit was estimated to be approximately 0.5 mg/kg. Each uncertainty component was evaluated separately, and the combined and expanded uncertainty values were calculated at the 95% confidence level. The measured concentrations for 3 mg/kg of chlorite and chlorate standard materials were $3.18{\pm}0.32$ and $3.10{\pm}0.42mg/kg$, respectively. These results confirmed the reliability of the developed method for measuring the two chlorine-based oxyanions in fresh-cut vegetables.

• Korean Journal of Environmental Agriculture
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• v.1 no.1
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• pp.48-52
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• 1982

Methods for the measurement of aquatic bacteria can be divided into two groups. The first group of these methods is based on the 'replicon' concept that live bacterial cells, when diluted and transferred to a suitable medium, produce colonies. These methods distinguish living from dead bacteria, but they massively underestimate bacterial numbers. The second group of enumeration methods uses visual counting technique using specific apparatus such as a microscope. These methods are generally direct and simple, but it is very hard to distinguish between live and dead bacteria and between small particle and bacteria. Recently developed technique in staining methods has provided a reliable method of visual determination of aquatic bacteria. This uses epifluorescence microscopy to measure the total bacterial population. In order to present the fluorescence microscopy as a new methodology for the determination of bacterial numbers in water supplies, data were obtained from chlorine and monochloramine doses added to samples. Total counts by fluorescence microscopy were compared with standard plate count method. The total number of bacteria in water supplies can be determined with fluorescence microscopy. This technique allows better resolution of small bacteria and differentiation of particle from bacteria. Chloramine was found to persist longer in natural waters and prevent bacterial regrowth.

• Korean Journal of Food Science and Technology
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• v.29 no.3
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• pp.427-431
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• 1997

A simultaneous and rapid gas chromatographic determination of organophosphorus, organo-chlorine, carbamate, and pyrethroid pesticides in polished rice was developed. The pesticides were extracted from samples with acetone by automated soxhlet apparatus and this extract was evaporated to dryness. The residue was dissolved in hexane, the solvent was applied to a Sep-Pak florisil catridge, was eluted with 50% ethyl acetate in n-hexane, and was injected to dual GC-ECD/NPD system. This simple method affords a high recovery of hydrophilic pesticides, allows rapid analysis, and is cheap to perform. Except for dichlorvos and captan, recoveries of 46 pesticides were over 60%.

• Journal of the Korean Society of Safety
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• v.14 no.4
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• pp.114-119
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• 1999

When NaOCl was generated and put into sea-water cooling machine in order to overcome the biological hindrances against sea-water cooling machine, it was converted into metallic ion, particularly Ca and Mg, as a hydrate in sea-water and is to stick to electrolyte as a side reaction. This phenomena make the distance between the electrolytes narrow to decrease the flow rate, which induces the local vortex flow which erodes the pole plate. Moreover, this increases the resistance of the electrolyte as well as voltage to decrease the electrolytic efficiency, which has curtailed a chlorine yield and caused a pole plate cut. We are able to overcome these problems by chemical cleaning and intend to extend the life-time of electrolyte and to increase output of the sea-water electrolysis facilities by studying optimal policy regarding chemical cleaning of electrolytic cell. Cleaning time of electrolytic facilities is determined when both increase in electrolytic efficiency and decrease in pole-plate voltage are 10%. At this time as operating current of electrolytic facilities is high, operating time is diminished. Whereas, parameter of end point determination according to cleaning is Mg ionic concentration in solution. When we use Cleaner as a 7wt% HCl, cleaning time is about 80min proper. We are able to maintain pole plate performance by protecting against pole plate cut by means of electrolytic by-product, improve operating rate of facilities, and cut down on maintenance expenditure after acidic cleaning.

• Proceedings of the Korean Institute of Building Construction Conference
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• 2018.11a
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• pp.6-7
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• 2018

In the previous study, durometer, namely rubber hardness tester Was used to confirm the possibility of using the setting time of concrete for determination. in this study, the possibility of using condensation time judgment condensation estimation system by comparing the measuring station setting estimation system Measuring needle of the proctor penetration resistance tester by newly making a measurement needle and refining the coagulation estimation system Want to make sure. As a result of this study, it was possible to use one condensation estimation system showing similar correlation between the two types of durometer showing high correlation with the penetration resistance value of proctor testers, It is considered to be fruitful to use the dew condensation estimation system for determining the setting time.

• Journal of the Korean Society of Tobacco Science
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• v.20 no.2
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• pp.183-190
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• 1998

This study was conducted to analyze chemical components in flue-cured tobacco using near infrared spectroscopy(NIRS). Samples were collected in '96 and '97 crop year and were scanned in the wavelengths of 400 ～ 2500 nm by near infrared analyzer(NIRSystem Co., Model 6500). Calibration equations were developed and then analyzed flue-cured samples by NIRS. The standard error of calibration(SEC) and performance (SEP) of '96 crop year samples between NIRS and standard laboratory analysis(SLA) were 0.18% and 0.24% for nicotine, 1.60% and 1.77% for total sugar, 0.13% and 0.15% for total nitrogen, 0.58% and 0.68% for crude ash, 0.23% and 0.28% for ether extracts, and 0.09% and 0.08% for chlorine, respectively. The coefficient of determination($R^2$) of calibration and prediction samples between NIRS and SLA of '96 crop year samples was 0.94～0.99 and 0.83～0.97 depending on chemical components, respectively. The SEC and SEP of '97 crop year samples were similar to those of '96 crop year samples. The SEP of '97 crop year samples which were analyzed using '96 calibration equation was 0.32 % for nicotine, 2.72% for total sugar, 0.14 % for total nitrogen, 1.00 % for crude ash, 0.48 for ether extracts and 0.17% for chlorine, respectively. The prediction result was more accurate when calibration and prediction samples were produced in the same crop year than those of the different crop year. The SEP of '96 and '97 crop year samples using calibration equation which was developed '96 plus '97 crop year samples was similar to that of '96 crop year samples using 96 calibration equation and that of '97 crop year samples using '97 calibration equation, respectively. The SEP of '97 crop year samples using calibration equation which was developed '96 plus '97 crop year samples was lower than that of '97 crop year samples analyzed by '96 calibration equation. To improve the analytical inaccuracy caused by the difference of crop year between calibration and prediction samples, we need to include the prediction sample spectra which are different from calibration sample spectra in recalibration sample spectra, and then develop recalibration equation. Although the analytical result using NIR is not as good as SLA, the chemical component analysis using NIR can apply to tobacco leaves, leaf process or tobacco manufacturing process which demand the rapid analytical result.

• Journal of the Korean Chemical Society
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• v.39 no.7
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• pp.513-523
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• 1995

Polychlorinated dibenzo-p-dioxins (PCDDs) and dibenzofurans (PCDFs) are the most concerned toxic organic pollutants to human. Because of their extremely high toxicity and uncertain genotoxic potential, their determination in environmental and biological samples is of great interest. Municipal solid waste incinerator facilities have been reported as the major contributors of dioxins and furans to the environment, and their formation from combustion is a universal phenomenon, everywhere. In this study dioxins and furans were analyzed from the bottom ash produced during combustion in an municipal waste incinerator located in Seoul. The EPA method was modified for sample pretreatment: the soxhlet method was used for extraction and clean-up procedures were performed by using silica and basic alumina, excluding active-carbon. The extract was then analyzed by HRGC/HRMS. A general trend of increase in the amounts of 6∼7 chlorine-substituted dioxins and furans was observed. Total dioxins, furans and 2,3,7,8-TCDD were determined as 8.05 ng/g, 4.75 ng/g, and 6.93 pg/g, respectively.