• Mass Spectrometry Letters
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• v.10 no.1
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• pp.18-26
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• 2019

We developed a bioanalytical method for simultaneous determination of nine NBOMe derivatives (25H-NBOMe, 25B-NBOMe, 25E-NBOMe, 25N-NBOMe, 25C-NBOH, 25I-NBOH, 25B-NBF, 25C-NBF, and 25I-NBF) in human plasma using liquid chromatography tandem mass spectrometry (LC-MS/MS). Human plasma samples were pre-treated using solid-phase extraction. Separation was achieved on a C18 column under gradient elution using a mobile phase containing 0.1% formic acid in acetonitrile and 0.1% formic acid in water at a flow rate of 0.3 mL/min. Mass detection was performed in the positive ion mode using multiple reaction monitoring. The calibration range was 1-100 ng/mL for all quantitative analytes, with a correlation coefficient greater than 0.99. The intra- and inter-day precision and accuracy varied from 0.85 to 6.92% and from 90.19 to 108.69%, respectively. The recovery ranged from 86.36 to 118.52%, and the matrix effects ranged from 27.09 to 99.72%. The stability was acceptable in various conditions. The LC-MS/MS method was validated for linearity, accuracy, precision, matrix effects, recovery and stability in accordance with the FDA guidance. The proposed method is suitable for reliable and robust routine screening and analysis of nine NBOMe derivatives in forensic field.

• Korean Journal of Environmental Agriculture
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• v.39 no.4
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• pp.368-374
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• 2020

BACKGROUND: The residual analysis of polar pesticides has remained a challenge. It is even more difficult to simultaneously analyze multiple polar pesticides. Diquat, paraquat, and chlormequat are typical examples of highly polar pesticides. The existing methods for the analysis of diquat, paraquat and chlormequat are complex and time consuming. Therefore, a simple, quick and effective method was developed in the represent study for simultaneous analysis of diquat, paraquat and chlormequat in animal products, meat and fat using UPLC-MS/MS. METHODS AND RESULTS: Sample extraction was carried out using acidified acetonitrile and water and re- extracted with acidified acetonitrile and combine the extracts followed by centrifugation. The extract was then cleaned up with a HLB cartridge after reconstitution with acidic acetonitrile and water. The method was validated in quintuplicate at three different concentrations. The limits of detection (LOD) and quantification (LOQ) were 0.0015 and 0.005 mg/L, respectively. Matrix suppression effect was observed for all of the analytes. A seven point matrix matched calibration curve was constructed for each of the compound resulted excellent linearity with determination coefficients (R2) ≥ 0.991. Accuracy and precision of the method was calculated from the recovery and repeatability and ranged from 62.4 to 119.7% with relative standard deviation less than 18.8%. CONCLUSION: The recovery and repeatability of the developed method were in the acceptable range according to the Codex Alimentarius guideline. The developed method can be applied for the routine monitoring of diquat, paraquat, and chlormequat in animal products, meat and fat.

• Korean Journal of Food Science and Technology
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• v.45 no.3
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• pp.382-384
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• 2013

We evaluated the presence of uniconazole residual pesticide in agricultural products by using multiclass pesticide multiresidue methods. Samples were collected from January to August, 2012. The pesticide was detected in 14 samples among the 3,632 samples tested. Amount of the uniconazole pesticide ranged from 0.098 to 2.2 mg/kg in the 14 samples. This method was described for the simultaneous determination of uniconazole by using gas chromatography with an electron capture detector (GC-ECD) and mass spectrometry (MS). For evaluating the GC-ECD method, uniconazole was spiked into gyeojachae at a level of 0.05, 0.5 mg/kg. The recoveries of uniconazole with the GC-ECD method ranged from 98.9-109.4%. The results indicate that our method of simultaneous analysis is applicable to uniconazole analysis.

• Journal of the Computational Structural Engineering Institute of Korea
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• v.36 no.6
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• pp.407-414
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• 2023

In this study, an automated jack-up system, applicable to various fields, was employed for 3D concrete printing and developed as a simultaneous liftable 3D concrete printing system. This developed printing system enables safe and precise jack-up by monitoring the measured jack-up distance using Pearson correlation coefficient analysis and a hydraulic system with interquartile range analysis in real-time during 3D concrete printing operations. It is possible to secure the quality of 3D concrete printing structures, which is essential for expanding the application of 3D concrete printing to construct larger structures. Specimens were printed using both conventional 3D concrete printing and simultaneous liftable 3D concrete printing to evaluate the system performance. The printed specimens were investigated using a 3D scanner. The layer-wise diameter and angle of intersection of the scanned specimens were measured, and an analysis was performed to verify the advantages of the simultaneous liftable 3D concrete printing.

• Korean Journal of Remote Sensing
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• v.27 no.4
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• pp.403-410
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• 2011

Consistent observation with high temporal and spatial resolution is required for an efficient monitoring of coastal environments. Remote monitoring system installed on the ground is capable of simultaneous observation of wide coastal area and consistent observation with high frequency, which a small number of in-situ measurements cannot manage. This paper studies two typical ground based coastal monitoring system, marine radar and camera system. Marine radar can produce time series of frequency spectrum by integrating wave number spectrum calculated from spatial and temporal variation of waves in the radar image. The time averaged radar images of waves can analyze wave breaking zone, rip currents and location of littoral bars. Camera system can observe temporal variation of foam generation originated from coastal contamination as well as shoreline changes. By extracting the part of foams from rectified images, quantitative analysis of temporal foam variation can be done. By using the two above systems of different characteristics, synergetic benefit can be achieved.

• The Bulletin of The Korean Astronomical Society
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• v.46 no.1
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• pp.52.1-52.1
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• 2021

We present the results of multi-epoch, multi-frequency monitoring of a blazar 4C +29.45, which was regularly monitored as part of the Interferometric Monitoring of GAmma-ray Bright AGNs program - a key science program of the Korean Very long baseline interferometry Network (KVN). Observations were conducted simultaneously at 22, 43, 86 and 129 GHz during the 4 years from December 2012 to December 2016. We also used additional data from the 15 GHz Owens Valley Radio Observatory (OVRO) monitoring program. From the 15 GHz light curve, we estimated the variability time scales of the source during several radio flux enhancements. We found that the source experiencesd 6 radio flux enhancements with variability time scales of 9-187 days during the observing period, yielding corresponding variability Doppler factors of 9-27. From the multi-frequency simultaneous KVN observations, we were able to obtain accurate radio spectra of the source and hence to more precisely measure the turnover frequencies 𝜈_r of synchrotron self-absorbed (SSA) emission with a mean value of ${\bar{\nu}_r}=28.9GHz$. Using jet geometry assumptions, we estimated the size of the emitting region at the turnover frequency. Taking into account these results, we found that the equipartition magnetic field strength is up to two orders of magnitudes higher than the SSA magnetic field strength (0.6-99 mG). This is consistent with the source being particle dominated.

• Journal of the Korean Society of Food Science and Nutrition
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• v.38 no.12
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• pp.1779-1784
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• 2009

Establishment of simultaneous analysis method and monitoring for individually analyzing residual eight ergosterol biosynthesis inhibitors, EBI (difenoconazole, diniconazole, fenarimol, fenbuconazole, hexaconazole, myclobutanil, nuarimol and paclobutrazol) pesticides in commercial agricultural products, were conducted. The simultaneous analysis method for the pesticides was established using a GC/MS/MS for EBI pesticides. Residual amount of those pesticides were investigated in 989 commercial agricultural products (fifteen kinds of cereal grains, vegetables, beans, nuts, fruits and mushrooms) from seven metropolitan cities and eight provinces. In EBI pesticides analysis, linearity of GC/MS/MS analysis was 0.9974-0.9992, and that of recoveries were 86-135% with relative standard deviations (RSD) <20%. The limit of quantification (LOQ) of the method ranged from 0.5 to 5.0 mg/kg for eight EBI pesticides. According to the monitoring of the EBI pesticides in commercial agricultural products, difenoconazole, fenarimol, hexaconazole showed various residual levels (total frequency of 8/989 detection, 0.8%). Paclobutrazole showed in excess levels of the MRLs (maximum residue limits) for pesticides in one chard sample by the Korea Food Code. As a result of exposure assessment on the detected 8 individual pesticides, all pesticides (difenoconazole, fenarimol, hexaconazole, paclobutrazole) were evaluated as safe level in comparison to toxicologically acceptable daily intake.

• Journal of Ginseng Research
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• v.43 no.4
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• pp.508-516
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• 2019

Background: Ginsenosides are not only the principal bioactive components but also the important indexes to the quality assessment of Panax ginseng Meyer. Their contents in cultivated ginseng vary with the growth environment and age. The present study aimed at evaluating the significant difference between 36 cultivated ginseng of different cultivation areas and ages based on the simultaneously determined contents of 14 ginsenosides. Methods: A high-performance liquid chromatography (HPLC) coupled with triple quadrupole mass spectrometer (MS) method was developed and used in the multiple reaction-monitoring (MRM) mode (HPLC-MRM/MS) for the quantitative analysis of ginsenosides. Multivariate statistical analysis, such as principal component analysis and partial least squares-discriminant analysis, was applied to discriminate ginseng samples of various cultivation areas and ages and to discover the differentially accumulated ginsenoside markers. Results: The developed HPLC-MRM/MS method was validated to be precise, accurate, stable, sensitive, and repeatable for the simultaneous determination of 14 ginsenosides. It was found that the 3- and 5-yr-old ginseng samples were differentiated distinctly by all means of multivariate statistical analysis, whereas the 4-yr-old samples exhibited similarity to either 3- or 5-yr-old samples in the contents of ginsenosides. Among the 14 detected ginsenosides, Rg1, Rb1, Rb2, Rc, 20(S)-Rf, 20(S)-Rh1, and Rb3 were identified as potential markers for the differentiation of cultivation ages. In addition, the 5-yr-old samples were able to be classified in cultivation area based on the contents of ginsenosides, whereas the 3- and 4-yr-old samples showed little differences in cultivation area. Conclusion: This study demonstrated that the HPLC-MRM/MS method combined with multivariate statistical analysis provides deep insight into the accumulation characteristics of ginsenosides and could be used to differentiate ginseng that are cultivated in different areas and ages.

• Asian Journal of Atmospheric Environment
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• v.7 no.2
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• pp.105-113
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• 2013

We constructed and tested an airborne peroxyacetyl nitrate (PAN) monitoring system based on luminol chemiluminescence detection with fast gas chromatography. This system allowed for simultaneous measurement of PAN and nitrogen dioxide ($NO_2$) with a time resolution of <2 min. Actual sample masses within the fixed volume sample loop at various altitudes and temperatures were adjusted to standard atmosphere, using measured pressures and temperatures. The airborne PAN measurement system was evaluated during two field studies above the southern Korean Peninsula in August and October 2009. The detection limit based on the ISO approach was 0.035 ppbv PAN, well below the observed concentrations of 0.185-1.49 ppbv during these studies. Under these conditions, the PAN mixing ratios were positively correlated with $O_x$ ($O_x=O_3+NO_2$), with slopes varying between 0.014 and 0.033 and intercepts between 22.6 and 55.1 ppbv $O_x$. The intercepts corresponded roughly to background $O_x$ mixing ratios in central Europe; however, the slopes were above the range of slopes reported in other studies. We also enhanced the durability, safety, and ease of maintenance of the PAN monitoring system by redesigning the structure of the conventional luminol cell.

• Journal of Korean Society on Water Environment
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• v.20 no.2
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• pp.170-175
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• 2004

The purpose of this study was to monitor bacteria present in raw water and to investigate the effect of ozone, UV and combined ozone/UV processes for inactivating bacteria. Both polymerase chain reaction (PCR)-fragment length polymorphic analysis (PRA) and PCR-sequence analysis (PSA) were applied for the simultaneous analysis of numerous bacteria species present in each tested water, such as drinking water (DRW), drinking water source (DRWS) and sewage effluent water (SEW). According to the result, the number of detected bacteria species was zero in DRW, 58 in DRWS and 13 in SEW. After treatment of the each process, the ozone/UV process was the most successful for inactivating almost all bacteria. However, it was found that Flavobacterium sp., Pseudomonas sp. and Beta proteobacterium sp. had strong resistant to all tested processes, requiring further detailed study.