Yun Gyong Ahn

Quantitative analysis of heterocyclic amines in urine by liquid chromatography coupled with tandem mass spectrometry

A sensitive, reproducible, and rapid analytical method for the analysis of trace-level heterocyclic amines (HCAs) that are expected to have high levels of human exposure was developed. Liquid-liquid extraction (LLE) with dichloromethane (DCM) followed by solid-phase extraction (SPE) was carried out. Liquid extraction with DCM under basic conditions was efficient in extracting HCAs from urine samples. For further purification, mixed mode cationic exchange (MCX) cartridges were applied to eliminate the remaining interferences after liquid extraction. Separation and quantification were performed by liquid chromatography coupled with tandem mass spectrometry (LC-MS/MS) in selected reaction monitoring (SRM) mode. The overall recoveries ranged between 71.0% and 113.6% with relative standard deviations (RSDs) of 5.1% to 14.7% for the entire procedure. The limits of detection (LODs) and limits of quantification (LOQs) of the proposed analytical method were in the ranges of 0.04 to 0.10 ng/ml and 0.15 to 0.36 ng/ml, respectively. This method was applied to the analysis of monitoring in urine samples for Korean school children, and the results demonstrated that the method can be used for the trace determination of HCAs in urine samples.

Analysis of Polychlorinated Dibenzo-p-dioxins and Dibenzo-furans in Sanitary Products of Women

To dissolve and develop the analytical methods for native polychlorinated dibenzo-p-dioxins (PCDDs) and polychlorinated dibenzofurans (PCDFs) in sanitary products, we collected sanitary napkins fro...

Formation of dimethyldithioarsinic acid in a simulated landfill leachate in relation to hydrosulfide concentration

Abstract Dimethyldithioarsinic acid (DMDTAV), present in such intense sources as municipal landfill leachate, has drawn a great deal of attention due to its abundant occurrence and different aspect of toxicity. The hydrosulfide (HS−) concentration in leachate was studied as a major variable affecting the formation of DMDTAV. To this end, the HPLC–ICPMS system equipped with the reversed-phase C18 column was used to determine DMDTAV. Simulated landfill leachates (SLLs) were prepared to cover a mature landfill condition with the addition of sodium sulfate and sulfide at varying concentrations in the presence of dimethylarsinic acid (DMAV). The concentration of sodium sulfide added in the SLLs generally exhibited a strong positive correlation with the concentration of DMDTAV. As such, the formation of DMDTAV in the SLLs is demonstrated to be controlled by the interactive relationship between DMAV and the HS−.

Identification and Characterization of Diploid and Tetraploid in Platycodon grandiflorum

AbstractPlatycodon grandiflorum (PG), a species of herbaceous flowering perennial plant of the family Campanulaceae, has been used as a traditional oriental medicine for bronchitis, asthma, pulmonary tuberculosis, diabetes, hepatic fibrosis, bone disorders and many others similar diseases and as a food supplement. For the primary profiling of PG gas chromatography coupled with high resolution – time of flight mass spectrometry (GC/HR-TOF MS) was used as an analytical tool. A comparison of optimal extraction of metabolites was carried out with a number of solvents [hexane, methylene chloride, methanol, ethanol, methanol: ethanol (70:30, v:v)]. In extracts with methanol: ethanol (70:30 v:v) were detected higher amounts of metabolites than with other solvents. Principal component analysis (PCA) and partial least-squares discriminant analysis (PLS-DA) plots showed significant differences between the diploid and tetraploid metabolite profiles. Extracts of tetraploid showed higher amounts of amino acids, while extracts of diploid contained more organic acids and sugars. Graphical Abstractᅟ

Discrimination of Platycodon grandiflorum and Codonopsis lanceolata using gas chromatography-mass spectrometry-based metabolomics approach

Species of herbaceous flowering perennial plant of the family Campanulaceae such as Platycodon grandiflorum (P. grandiflorum) and Codonopsis lanceolata (C. lanceolata) widely used in traditional medicine to treat different diseases. In spite of different medicinal results after consumption of the plants, it is hard to distinguish between two of them, because of their similar morphological characteristics. In this study, a gas chromatography-mass spectrometry (GC-MS) - based metabolite profiling approach was performed and examined to discriminate tuberous roots of P. grandiflorum and C. lanceolate for medicinal purposes. Two basic approaches for sample preparation, headspace solid-phase microextraction (HS-SPME) and solvent extraction were adopted. Multivariate statistical techniques, such as orthogonal partial least-squares discriminant analysis (OPLS-DA) plots showed significant differences between P. grandiflorum and C. lanceolata for polar primary and volatile organic metabolites. A number of potential candidates were suggested as the chemomarkers for discrimination of two plants.

Development and Validation of Gas Chromatography-Triple Quadrupole Mass Spectrometric Method for Quantitative Determination of Regulated Plasticizers in Medical Infusion Sets

A method for the quantitative determination of dibutyl phthalate (DBP), benzyl butyl phthalate (BBP), bis(2-ethylhexyl) adipate (DEHA), bis(2-ethylhexyl) phthalate (DEHP), di-n-octyl phthalate (DNOP), dioctyl terephthalate (DOTP), diisononyl phthalate (DINP), and diisodecyl phthalate (DIDP) in medical infusion sets was developed and validated using gas chromatography coupled with triple quadrupole mass spectrometry (GC-MS/MS) in the multiple reaction monitoring (MRM) mode. Solvent extraction with polymer dissolution for sample preparation was employed prior to GC-MS/MS analysis. Average recoveries of the eight target analytes are typically in the range of 91.8–122% with the relative standard deviations of 1.8–17.8%. The limits of quantification (LOQs) of the analytical method were in the ranges of 54.1 to 76.3 ng/g. Analysis using GC-MS/MS provided reliable performance, as well as higher sensitivity and selectivity than GC-MS analysis, especially for the presence of minority plasticizers at different concentrations.

Inter-Laboratory Validation of Method to Determine Residual Enrofloxacin in Chicken Meat

An inter-laboratory study was performed to evaluate the performance of a method developed for the quantification of enrofloxacin in chicken meat. Liquid-liquid extraction combined with a clean-up procedure based on solid-phase extraction followed by a liquid chromatography-tandem mass spectrometric method was used by three individual laboratories. All the investigated results of calibration curves and limits of quantification were within the acceptable range for regulatory testing of enrofloxacin. The three laboratories received blind a certified reference material to analyze in triplicate and assess using statistical analysis. From the results, no statistical differences were found between the laboratories in the precision of the method. Additionally, all the results of the z-score, which is an indication of fixed interval bias criteria for accuracy from the laboratories, fell within the allowable limits (±2σ). Based on this proficiency testing by inter-laboratory comparisons, the analytical method including the sample preparation step was proven to be applicable.

Polychlorinated dibenzo-p-dioxins and dibenzofurans levels in piglet liver with various diseases

This study deals with the levels of toxic polychlorinated dibenzo‐p‐dioxin and furan congeners (PCDD/Fs) in the livers of piglets affected by infectious diseases using isotope dilution high‐resolution gas chromatography/high‐resolution mass spectrometry (HRGC/HRMS). Seventeen toxic congeners in the liver samples infected with bacterial and viral diseases were compared. For porcine reproductive and respiratory syndrome virus (PRRSV) samples, the North American‐ and European‐type PRRS diseases were observed. This study shows that there are significantly different levels of PCDD/Fs, present, which vary according to the types of diseases as evidenced by our analysis of the piglet liver samples.

Development of chemical ionization method in a GC-TOF mass spectrometer for accurate mass and isotope ratio measurement

An accurate mass and isotope ratio were determined using a gas chromatography/time of flight mass spectrometer in CI positive mode for the identification of unknown metabolites. High mass tune was used to improve the ion intensity of . Chromatographic resolution and dynamic range enhancement were performed to obtain more reliable accurate masses and correct isotope abundance ratios. Average absolute errors of mass and isotope ratios for 24 reference metabolite -TMS (trimethylsilyl) derivatives were 6.8 ppm, 1.5% of (M+1/M ratio) and 1.7% of (M+2/M ratio), respectively. The correct formulas of twenty one compound were retrieved within top-2 hit from the heuristic algorithm for elemental composition using each accurate mass and isotope abundance ratio.