• Analytical Science and Technology
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• v.16 no.1
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• pp.32-38
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• 2003

The rapid and sensitive determination method of sildenafil and its related compounds (Vardenafil, Homosildenafil, Tadanafil.) has been investigated using high performance thin layer choromatography (HPTLC). Optimizing separation conditions and simultaneous determination method of these compounds were studied. The calibration curves of those compounds at 254 nm was found to be linear in the range of $1.0{\sim}56.5{\mu}g/mL$, respectively. The detection limts (LOD) and quantification limits (LOQ) of these were found to be $0.8{\sim}1.8{\mu}g/mL$ and $1.0{\sim}2.3{\mu}g/mL$. The coefficient of variation (C.V.) were less than 2.5%. Finally, the present method was applied to determine sildenafil and its related substances in dietary supplement.

• Analytical Science and Technology
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• v.17 no.6
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• pp.520-526
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• 2004

To determine 6 anti-impotence drug-like compounds such as sildenafil, vardenafil, tadalafil, homosildenafil, hydroxyhomosildenafil and hongdenafil in food, simultaneously, high performance liquid chromatography was applied. In the case of solid sample, it was extracted in organic solvents after homogenizing with mortar and pestle. Whereas liquid sample was just diluted in water and then extracted in organic solvents. Maximum lengths of UV for targets have been identified on photodiode array spectra. As results, vardenafil, hongdenafil, hydroxyhomosildenafil, sildenafil, homosildenafil, and tadalafil were eluted in order using $C_{18}$ column in acetonitrile containing phosphoric acid as the mobile phase. The maximum wavelength (${\lambda}_{max}$) was 216 nm for vardenafil, 233 and 282 nm for hongdenafil, 222 and 293 nm for hydroxyhomosildenafil, sildenafil and homosildenafil, and 284 nm for tadalafil. The overall recoveries were ranged from 95% to 109% and the limit of detection was about 0.04 mg/kg at signal/noise>3. Levels of targets in the selected food samples were 1.7 (hongdenafil) ~ 63 (tadalafil) mg/one dose.

• Korean Journal of Food Science and Technology
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• v.52 no.2
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• pp.113-118
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• 2020

We investigated the quality characteristics and antioxidant capacities of Korean commercial yogurt. Twenty commercial yogurt samples exhibited a pH of 4.05-4.51, titratable acidity of 0.80-1.45%, viable counts of 6.65-9.39 log CFU/g, and total phenolic content of 0.71-2.92 mg gallic acid equivalent/g dry weight (dw). Lactic acid was the major organic acid detected by HPLC with UV detection, and its content was 5.4 times and 46.5 times higher than that of malic acid and citric acid, respectively. The tested commercial yogurt samples exhibited antioxidant potential (1.62-8.95 mM trolox equivalent/g, dw) measured based on scavenging activities of DPPH and ABTS radicals. The average antioxidant potentials of commercial set yogurt containing fruit syrup were significantly (p<0.05) higher than that of cream and plain yogurt. A positive linear correlation was observed between the total phenolic content and the antioxidant capacities, suggesting that phenolic components are likely to contribute significantly to the antioxidant potential of commercial yogurt.

• Journal of Food Hygiene and Safety
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• v.29 no.1
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• pp.31-39
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• 2014

Norovirus causes acute gastroenteritis in all age groups and its food poisoning outbreaks are rapidly increasing in Korea. Reverse transcription-polymerase chain reaction (RT-PCR) is most widely used for the rapid detection of foodborne viruses due to high sensitivity. However, the false positive results of RT-PCR obtained against already inactivated viruses could be a serious drawbacks in food safety area. In this study, we investigated a method to yield true positive RT-PCR results only with alive viruses. To decompose the RNA genes from dead viruses, the enzymatic treatments composed of proteinse K and Ribonuclease A were applied to the sanitized and inactivated virus particles. Another aim of this study was to quantify the efficiencies of several major sanitizing treatments using real-time RT-PCR. Feline calicivirus (FCV) that belongs to the same Caliciviridae family with norovirus was used as a surrogate model for norovirus. The initial level of virus in control suspension was approximately $10^4$ PFU/mL. Most of inactivated viruses treated with the enzymatic treatment for 30 min at $37^{\circ}C$ were not detected in RT-PCR, Quantification results to verify the inactivation efficiencies of sanitizing treatments using real-time RT-PCR showed no false positive in most cases. We could successfully develope a numerical quantification process for the inactivated viruses after major sanitizing treatments using real-time RT-PCR. The results obtained in this study could provide a novel basis of rapid virus quantification in food safety area.

• Korean Journal of Optics and Photonics
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• v.28 no.3
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• pp.116-121
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• 2017

In this paper, a Raman spectrometer is designed to detect chemicals contaminating the ground. The system is based on Raman spectroscopy, which is spectral analysis of scattered light from chemicals, induced by a laser. The system consists of a transmitting-optics module with a laser to induce Raman-scattered light from the sample, a receiving-optics module to collect the scattered light, and a spectrograph to separate the collected light into a wavelength spectrum. The telescope, a part of the receiving-optics module, is designed to produce a focal spot in the same position for variable measurement distances using the code V simulator, considering the distance change between the system and the road. The Raman spectra of 12 chemicals on a glass surface and on a concrete sample were measured. Intensity differences between the Raman spectra acquired on a glass surface and on a concrete sample were observed, but the characteristics of the spectra according to the chemicals on them were similar. Additionally, the Raman spectrum of PTFE (polytetrafluoroethylene) was measured at various distances. The measured and simulated optical throughputs were similar. In conclusion, it is confirmed that with this system the Raman spectrum can be measured, irrespective of the distance change.

• Analytical Science and Technology
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• v.21 no.6
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• pp.518-525
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• 2008

Mandipropamid is a new mandelamide-type fungicide to control foliar Oomycete pathogens in some vegetables. An analytical method was developed to determine mandipropamid residues in agricultural commodities using high-performance liquid chromatography (HPLC) and liquid chromatography/mass spectrometry (LC/MS). Mandipropamid was extracted with methanol from grape, tomato, green pepper, Chinese cabbage and potato samples. The extract was diluted with saturated sodium chloride solution and distilled water, and dichloromethane partition was followed to recover the mandipropamid from the aqueous phase. Florisil column chromatography was employed to further remove interfering co-extractives prior to HPLC analysis. Reverse-phased HPLC was successfully applied to determine mandipropamid in sample extracts with the detection at its ${\lambda}_{max}$ (223 nm). Overall recoveries of mandipropamid from fortified samples averaged $99.8{\pm}1.7$ (n=6), $89.3{\pm}5.3$ (n=6), $98.7{\pm}2.2$ (n=6), $99.7{\pm}6.8$ (n=6) and $91.1{\pm}3.1$ (n=6) for grape, tomato, green pepper, Chinese cabbage and potato, respectively. Limit of quantification of the method was 0.02~0.04 mg/kg for all samples. A LC/mass spectrometry with selected-ion monitoring was also provided to confirm the suspected residue. The proposed method was reproducible and sensitive enough to determine the terminal residue of mandipropamid in agricultural commodities.

• Korean Journal of Food Science and Technology
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• v.42 no.1
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• pp.1-7
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• 2010

To revise the dithiocarbamates residue analysis method and survey the residues in agricultural products that were treated with these fungicides in Korea, we purchased 20 types of foodstuffs (rice, potato, cabbage, apple etc.) from markets in five major cities. 236 samples of the purchased foodstuffs were then analyzed for the presence of dithiocarbamates by HPLC/UV and HPLC/APCI-MS. The $R^2$, LOD and LOQ in the range of 0.5-107.3 mg/L were as follows: DCC: y=174.34x+18.315, $R^2=0.9999$, 0.01 mg/L, and 0.04 mg/L; EBDC: y=227.38x-14.715, $R^2=1.0000$, 0.01 mg/L and 0.02 mg/L; PBDC: y=38.46x-21.412, $R^2=0.9999$, 0.04 mg/L, and 0.1 mg/L; ETU: y=52.752x-4.4819, $R^2=0.9998$, 0.02 mg/L and 0.03 mg/L; PTU: y=128.28x+4.4624, $R^2=0.9998$, 0.02 mg/L, and 0.04 mg/L. The levels of DDC, EBDC, PBDC, ETU and PTU in 20 agricultural products fortified to 10.0-107.3 mg/L ranged from 61.7-117.5%, 65.3-110.1%, 61.5-109.6%, 69.3-116.3% and 70.2-97.2%, respectively. Overall, dithiocarbamates were detected in 100 samples and the detection ratio was 42.4%. Among these, only 3 samples (1.3%) of Lycii fructus had residue levels that were above the action limits, while the remaining samples (233 samples) contained levels of dithiocarbamates below the detection limit or below the Korea MRLs (Maximum Residue Limits).

• Journal of the Korean Society of Food Science and Nutrition
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• v.44 no.1
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• pp.85-88
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• 2015

This study attempted to establish an HPLC analysis method for determination of marker compounds as a part of material standardization for the development of health functional food materials from Perilla frutescens Britton var. acuta Kudo. The quantitative determination method of rosmarinic acid as a marker compound of P. frutescens Britton var. acuta Kudo extract (PFE) was optimized by HPLC analysis using a C18 column ($4.6{\times}150mm$, $5{\mu}m$) with 0.1% acetic acid as the elution gradient and methanol as the mobile phase at a flow rate of 1 mL/min and detection wavelength of 280 nm. The HPLC/UV method was applied successfully to quantification of the marker compound in PFE after validation of the method with linearity, accuracy, and precision. The method showed high linearity in the calibration curve at a coefficient of correlation ($R^2$) of 0.9995, and the limit of detection and limit of quantitation were $0.36{\mu}g/mL$ and $1.2{\mu}g/mL$, respectively. Relative standard deviation (RSD) values of data from intra- and inter-day precision were less than 3.21% and 1.43%, respectively. Recovery rate test at rosmarinic acid concentrations of 12.5, 25 and $50{\mu}g/mL$ scored between 97.04~98.98% with RSD values from 0.25~1.97%. These results indicate that the established HPLC method is very useful for the determination of marker compound in PFE to develop a health functional material.

• Journal of Food Hygiene and Safety
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• v.39 no.2
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• pp.72-82
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• 2024

This study aimed to develop a scientifically and systematically standardized xylooligosaccharide analytical method that can be applied to products with various formulations. The analysis method was conducted using HPLC with Cadenza C₁₈ column, involving pre-column derivatization with 1-phenyl-3-methyl-5-pyrazoline (PMP) and UV detection at 254 nm. The xylooligosaccharide content was analyzed by converting xylooligosaccharide into xylose through acid hydrolysis. The pre-treated methods were compared and evaluated by varying sonication time, acid hydrolysis time, and concentration. Optimal equipment conditions were achieved with a mobile phase consisting of 20 mM potassium phosphate buffer (pH 6)-acetonitrile (78:22, v/v) through isocratic elution at a flow rate of 0.5 mL/min (254 nm). Furthermore, we validated the advanced standardized analysis method to support the suitability of the proposed analytical procedure such as specificity, linearity, detection limits (LOD), quantitative limits (LOQ), accuracy, and precision. The standardized analysis method is now in use for monitoring relevant health-functional food products available in the market. Our results have demonstrated that the standardized analysis method is expected to enhance the reliability of quality control for healthy functional foods containing xylooligosaccharide.

• Korean Journal of Food Science and Technology
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• v.42 no.3
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• pp.287-291
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• 2010

In this study, a simple and rapid pre-treatment method based on liquid extraction was applied for the simultaneous determination of three macrolides (spiramycin, tylosin, and tilmicosin) residues. In these studies, the stock farm products was used as a matrix sample. When the liquid extraction method was compared with the solid phase extraction (SPE) method, the former showed higher recovery percentages and simpler steps than the latter. The macrolids were separated using a reverse-phase C18 ($250\;mm{\times}4.6\;mm$, $5\;{\mu}m$) column and a gradient elution with mobile phases consisting of phosphate buffer (pH 2.5) and acetonitrile. Tylosin and tilmicosin were detected at 288 nm and spiramycin was detected at 232 nm. The average recovery percentage ranged between 83.0-90.2% for samples spiked with the three macrolids at 50 and 100 ng/g The validation results showed that the limit of detection (7 (spiramycin), 12 (tilmiconsin), 12 (tylosin) ng/g)) was under the regulatory tolerances and the linearity from calibration curves was satisfactory for determining the multi-residue of three macrolids in farm products. Monitoring samples were collected at the main cities in Korea as Seoul, Busan, Deajeon, Incheon, Deagu, and Gwangju. Microlide antibiotics were not detected in most samples.