Heesoo Pyo

Determination of organochlorine pesticides in sediment using graphitized carbon black solid-phase extraction and gas chromatography/mass spectrometry.

An analytical method for the determination of organochlorine pesticides (OCPs) in sediment samples involves ultrasonic extraction, solid-phase extraction (SPE), gas-chromatography (GC)/electron-capture detection (ECD), and GC/mass spectrometry (MS). OCPs were extracted from sediment samples by ultrasonication in mixtures of n-hexane and acetone. Several SPE sorbents [Florisil, silica gel, C18, Oasis HLB, and graphitized carbon black (GCB)] were evaluated as means of preliminary purification. GCB SPE cartridges successfully removed major contaminants such as non-polar hydrocarbons when eluted with an acetone-acetonitrile mixture. After purification, the extract was preferentially screened using GC/ECD and confirmed and quantified using GC/MS. The percentage recovery of samples spiked with 10 or 100ng/g OCP ranged from 73.9% to 106.0% with a relative standard deviation of 0.4-5.7%. Detection limits ranged from 0.002 to 0.005ng/g for GC/ECD and from 0.03 to 0.50ng/g for GC/MS detection. The linear dynamic range extended from 0.2 to 20ng/g, with a correlation coefficient (R(2)) greater than 0.995. The method was validated using a standard reference material (SRM 1941b) and spiked sediment samples. Real sediment samples collected from a river near a Korean industrial area exhibited low levels of several OCPs when analyzed using this method.

Association between urinary levels of bisphenol-A and estrogen metabolism in Korean adults

Bisphenol-A (BPA) possesses estrogenic properties both in vitro and in vivo as an endocrine disrupting chemical. Humans experience a long-term and cumulative exposure to BPA. BPA was detectable in 97.3% of 1904 urine specimens from Korean adults. We investigated urinary estrogen concentrations in subjects with low and high BPA concentrations and its possible association with estrogen metabolism. Urine samples were collected from a high BPA concentration group (BPA-H; n=100, 11.05 ± 20.47 μg/g creatinine) and a low BPA concentration group (BPA-L; n=100, 0.70 ± 0.22 μg/g creatinine) from Korea Biomonitoring Program of Hazardous Materials Survey 2009-2010. Urinary estrogens were enzymatically hydrolyzed, extracted, and then derivatized for quantitative analysis by gas chromatography-mass spectrometry. Estrogen levels were higher in the BPA-H group than in the BPA-L group. Concentrations of estrone, 17β-estradiol, and their hydroxylated metabolites in both men and women were significantly higher in the BPA-H group than in the BPA-L group (p<0.04). Furthermore, in the BPA-H group, estrogen metabolism to 4-hydroxy-estrone and 4-hydroxy-17β-estradiol was more active than that to 2-hydroxy-estrone and 2-hydroxy-17β-estradiol. Although single measurement and/or single spot urine samples limit the measurement of long-term exposure to BPA, we found significant differences of estrogen metabolism in the BPA-H and the BPA-L groups. The increase of hydroxyestrogens, especially 4-hydroxyestrogens, can be an important factor resulting negative effects of prolonged exposure to BPA.

Biomonitoring of urinary di(2-ethylhexyl) phthalate metabolites of mother and child pairs in South Korea

Di(2-ethylhexyl) phthalate (DEHP) is one of the common phthalate plasticizers used primarily in soft polyvinyl chloride, which is a plastic polymer that makes up the total weight of goods from 1% up to 40% in many consumer products. The aims of this study were to examine the urinary DEHP metabolites in South Korean children and to investigate the correlation between mother and child DEHP urine excretion. Three kinds of urinary DEHP metabolites: mono(2-ethylhexyl) phthalate (MEHP), mono(2-ethyl-5-hydroxyhexyl) phthalate (5-OH-MEHP) and mono(2-ethyl-5-oxohexyl) phthalate (5-oxo-MEHP), were analyzed. The total of 954 samples (nChildren=392, nMothers=265, nAadults=297), including 258 mother and child pairs, were analyzed using isotope dilution gas chromatography-mass spectrometry. Many studies present higher concentration of DEHP metabolites detected from adults in reproductive age than adults in other ages. Therefore, adults who are age-matched to mothers were evaluated to serve as a standard of comparison against mothers. All statistical analysis was made by adjusting detected volume concentrations (μg/L) with respect to creatinine concentrations (mg/dL) since urinary DEHP metabolites were studied using human reference. The difference in median levels of sum of urinary DEHP metabolites was only significant when children were analyzed in relation to region (p-value≤0.005). Among the three DEHP metabolites, only MEHP of children was significantly correlated to that of paired mothers (p-value≤0.01). The present paper defines the relative metabolic rate (RMR) of DEHP metabolism for the first time in study on phthalates. Children had faster RMR than mothers and adults, specifically in the first step of DEHP metabolism (RMR1: MEHP hydroxylation to 5-OH-MEHP), and RMR1 of children between 1 and 24 months was the fastest. The above results may be used to study and assess human health risk from DEHP exposures, especially among mothers and children in Korea.

Simultaneous analysis of urinary phthalate metabolites of residents in Korea using isotope dilution gas chromatography–mass spectrometry

Phthalates are used in industry products, household items, and medical tools as plasticizers. Human exposure to phthalates has raised concern about its toxicity. In the present study, optimization was conducted for the simultaneous analysis of eight kinds of phthalate metabolites using gas chromatography-mass spectrometry (GC-MS): MEP, MiBP, MnBP, MBzP, MiNP, MEHP, MEOHP, and MEHHP. In order to minimize the matrix effect and to do quantitative analysis, isotope dilution and LLE-GC-MS methods were performed. Urine samples were enzymatically hydrolyzed, extracted with a mixture of n-hexane and ethyl ether (8:2; v:v), and subsequently derivatized with trimethylsilylation. All eight kinds of analytes showed clear resolution and high reproducibility in GC-MS results. The method detection limit ranged from 0.05 ng/mL to 0.2 ng/mL. Calibration curves were found to be linear from 0.2 to 100 ng/mL with -(2)>0.992. The relative standard deviation of the intraday precision using water and urine ranged from 2.1% to 16.3%. The analysis was performed with urine samples that were collected from adults residing in the Republic of Korea. The analyzed concentration results were compared according to gender and region. As a result, DEHP metabolites showed the highest detected concentration (75.92 μg/g creatinine, 100%), and MiNP, a metabolite of DiNP, showed the lowest detected concentration (0.42 μg/g creatinine, 22.5%). On average, female urine (200.76 μg/g creatinine) had a higher detected concentration of ∑8 phthalate metabolites than male urine. Samples from rural regions (211.96 μg/g creatinine) had higher levels than samples from urban regions.

Estimation of the Biological Half-Life of Methylmercury Using a Population Toxicokinetic Model.

Methylmercury is well known for causing adverse health effects in the brain and nervous system. Estimating the elimination constant derived from the biological half-life of methylmercury in the blood or hair is an important part of calculating guidelines for methylmercury intake. Thus, this study was conducted to estimate the biological half-life of methylmercury in Korean adults. We used a one-compartment model with a direct relationship between methylmercury concentrations in the blood and daily dietary intake of methylmercury. We quantified the between-person variability of the methylmercury half-life in the population, and informative priors were used to estimate the parameters in the model. The population half-life of methylmercury was estimated to be 80.2 ± 8.6 days. The population mean of the methylmercury half-life was 81.6 ± 8.4 days for men and 78.9 ± 8.6 days for women. The standard deviation of the half-life was estimated at 25.0 ± 8.6 days. Using the direct relationship between methylmercury concentrations in blood and methylmercury intake, the biological half-life in this study was estimated to be longer than indicated by the earlier studies that have been used to set guideline values.

Profiling analysis of biogenic amines and their acidic metabolites in mouse brain tissue using gas chromatography-tandem mass spectrometry.

The profiling analysis of biogenic amines, including catecholamines and serotonin, and their metabolites in mouse brain tissue provides an important key to understanding their roles in the body and the possibility of simple and accurate diagnosis of neural diseases. A novel approach in the analysis of biogenic amines and their acidic metabolites in brain tissue using gas chromatography-tandem mass spectrometry (GC-MS/MS) is presented. Biogenic amines and their acidic metabolites in brain tissue were effectively separated using a mixed-cation-exchange solid-phase extraction (MCX-SPE) cartridge with a variation in the composition of the SPE elution solvents. A selective derivatization with hexamethyldisilazane (HMDS) and N-methyl-bis-heptafluorobutyramide (MBHFBA) was used to increase the detection sensitivity and to prevent the formation of any side-products. The identification and quantification of the target analytes were performed by gas chromatography triple quadrupole mass spectrometry (GC-MS/MS) using multiple ion reaction monitoring (MRM) mode. The overall recovery yields of the biogenic amines and their metabolites were above 87.5% at 10ng/g and 92.4% at 100ng/g of spiking concentration range. The isotopic-labeled internal standards were used for the precise quantification of bioamines and their metabolites. The calibration curves for the biogenic amines and their metabolites obtained through GC-MS/MS were linear (r(2)>0.995) over the concentration range of 1 (2 or 3)-200ng/mL. The present method was reproducible (relative standard deviation range 0.6-9.3%) and accurate (range 85.4-107.9%), with LLOQs of 0.71-3.69ng/mL. The developed method was successfully applied to the determination and quantification of bioamines and their metabolites in rat brain tissue samples.

Korean research project on the integrated exposure assessment of hazardous substances for food safety.

Objectives: This survey was designed to conduct the first nationwide dietary exposure assessment on hazardous substances including the intakes of functional food and herbal medicine. In this paper, we introduced the survey design and the results of the dietary exposure status and internal exposure levels of lead (Pb), cadmium (Cd), and mercury (Hg). Methods: We selected 4867 subjects of all ages throughout Korea. We conducted a food survey, dietary survey, biomonitoring, and health survey. Results: Pb and Cd were the highest (median value) in the seaweed (94.2 μg/kg for Pb; 594 μg/kg for Cd), and Hg was the highest in the fish (46.4 μg/kg). The dietary exposure level (median value) of Pb was 0.14 μg/kg body weight (bw)/d, 0.18 μg/kg bw/d for Cd, and 0.07 μg/kg bw/d for Hg. Those with a blood Pb level of less than 5.00 μg/dL (US Centers for Disease Control and Prevention, reference value for those 1 to 5 years of age) were 99.0% of all the subjects. Those with a blood Cd level with less than 0.30 μg/L (German Federal Environmental Agency, reference value for non-smoking children) were 24.5%. For those with a blood Hg level with less than 5.00 μg/L (human biomonitoring I, references value for children and adults, German Federal Environmental Agency) was 81.0 % of all the subjects. Conclusions: The main dietary exposure of heavy metals occurs through food consumed in a large quantity and high frequency. The blood Hg level and dietary exposure level of Hg were both higher than those in the European Union.

Effective application of freezing lipid precipitation and SCX-SPE for determination of pyrrolizidine alkaloids in high lipid foodstuffs by LC-ESI-MS/MS.

Pyrrolizidine alkaloids (PAs) are naturally occurring plant toxins associated with serious hepatic disease in humans and animals. In this study, rapid and sensitive analytical method was developed for the determination of 9 toxic PAs in popularly high lipid foodstuffs by liquid chromatography-electrospray ionization-tandem mass spectrometry (LC-ESI-MS/MS). PAs in lipid foodstuff were effectively purified by freezing lipid precipitation (FLP) and strong cation exchange (SCX)-solid-phase extraction (SPE). Especially, FLP could easily remove the large amounts of triacylglycerols in the lipid sample extract and effectively combine with SPE cleanup. During the FLP procedure, over 77% of the lipids in the foodstuff extracts were rapidly eliminated without any significant loss of the PAs with over 81% recovery. The elimination efficiency of lipids by FLP was tested with LC-atmospheric chemical ionization (APCI)-MS. For further purification, SCX-SPE cartridge could successfully purify PAs from the remaining interfering substances by the variation pH with 5% NH4OH in methanol. For precise quantification and confirmation of PAs in complicate sample matrices, appropriate transition ions in LC-MS/MS-multiple-ion reaction monitoring (MRM) mode were selected on the basis of MS/MS fragmentation pathways of PAs. The established analytical method was validated in terms of the linearity, limits of detection (LOD), and quantification (LOQ), precision, and accuracy. The method was deemed satisfactory by inter- and intra-day validation and exhibited both high accuracy and precision (relative standard deviation<11.06%). Overall limits of detection and quantitation of PAs were approximately 0.06-0.60ng/mL at a signal-to-noise ratio (S/N) of 3 and were about 0.20-1.99ng/mL at a S/N of 10 for all foodstuffs. The established method was successfully applied for the monitoring of toxic PAs in several types of high lipid foodstuffs such as soybeans, seed oil, milk, and margarine.

Analysis of mesocarb analogues in urine and plasma of rats by high-performance liquid chromatography and thermospray liquid chromatography-mass spectrometry

The pharmacokinetics and metabolism of synthetic 2-hydroxymesocarb and 4-methyl-2-hydroxymesocarb analyzed by HPLC-DAD and thermospray LC-MS were studied in rats. Multistep liquid-liquid extraction (LLE) was used with diethyl ether at pH 7.0. The major metabolites of 2-hydroxymesocarb in both urine and plasma of the rat were the p-hydroxylated derivative of the phenylcarbamoyl group of the parent drug. The metabolites of 4-methyl-2-hydroxymesocarb in urine of rats may be the oxidized forms at the phenylcarbamoyl group of the parent drug. Absorption (ka) and elimination (ke) rate constants in plasma of 2-hydroxy-mesocarb were 0.0300 and 0.00485 min-1, respectively; those of 4-methyl-2-hydroxymesocarb were 0.0546 and 0.00797 min-1, respectively. The half-lives (t1/2) of 2-hydroxymesocarb and 4-methyl-2-hydroxymesocarb in plasma were 144 and 86 min, respectively.

Analysis of 3-MCPD and 1,3-DCP in Various Foodstuffs Using GC-MS

3-Monochloro-1,2-propanediol (3-MCPD) and 1,3-dichloro-2-propanol (1,3-DCP) are not only produced in the manufacturing process of foodstuffs such as hydrolyzed vegetable proteins and soy sauce but are also formed by heat processing in the presence of fat and low water activity. 3-MCPD exists both in free and ester forms, and the ester form has been also detected in various foods. Free 3-MCPD and 1,3-DCP are classified as Group 2B by the International Agency for Research on Cancer. Although there is no data confirming the toxicity of either compound in humans, their toxicity was evidenced in animal experimentation or in vitro. Although few studies have been conducted, free 3-MCPD has been shown to have neurotoxicity, reproductive toxicity, and carcinogenicity. In contrast, 1,3-DCP only has mutagenic activity. The purpose of this study was to analyze 3-MCPD and 1,3-DCP in various foods using gas chromatography -mass spectrometry. 3-MCPD and 1,3-DCP were analyzed using phenyl boronic acid derivatization and the liquid–liquid extraction method, respectively. The analytical method for 3-MCPD and 1,3-DCP was validated in terms of linearity, limit of detection (LOD), limit of quantitation, accuracy and precision. Consequently, the LODs of 3-MCPD and 1,3-DCP in various matrices were identified to be in the ranges of 4.18~10.56 ng/g and 1.06~3.15 ng/g, respectively.