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In this study, analytical method is applied for the estimation of dynamic behaviors of beam-coupled structures. Mathematical expressions are given with terms of shape factors, material information and assembly angles of each sub-component. Based on Euler-Bernoulli beam theory, entire formulation is built with compatibility of system dynamics. The coupled structures are divided into two types, point coupling and mass coupling, related with the properties of coupling points. Point coupling is commonly used assumption that two sub-components are combined with lumped spring or damping, and mass coupling has undeformable rigid joint which has mass and inertia like welded structures. Dynamic properties of coupled structures are predicted in forms of frequency response functions and spectral responses about given forces. The verification process is conducted for assessing the accuracy of the estimation formula by using modal frequencies and mode shapes of beam-coupled structures. Extracted modal parameters from experimental modal analysis and finite element method are adopted as reference values for verification.

A solvent-free headspace gas chromatography-mass spectrometry (SF-HS-GC/MS) method was developed and validated for screening N-nitrosodimethylamine (NDMA) in various active pharmaceutical ingredients (APIs) and drug products. Experimental parameters such as incubation temperature, incubation time, and sample volume in solvent-free headspace conditions were optimized. The developed SF-HS-GC/MS method was validated in terms of linearity, limit of quantification (LOQ), precision, and accuracy. The results indicated excellent linearity from 5 to 500 ng g-1 with correlation coefficients higher than 0.9999. The LOQ of this method was 5 ng g-1 and matrix effects ranged from 0.97 to 1.11. The accuracy ranged from 92.77 to 106.54% and the precision RSDs were below 5.94%. No significant matrix effect was observed for any of the drug products. Also, artefactual NDMA formation in ranitidine, nizatidine, and metformin was investigated under HS conditions. Adjusted (mild) SF-HS conditions were suggested for precise quantification of NDMA in positive drug products by GC/MS. The present SF-HS-GC/MS method is a promising tool for the screening and determination of toxic NDMA in APIs and drug products.

This study aimed to measure phytoestrogen contents in health functional foods (HFFs) to alleviate menopausal symptoms that are commercially available in South Korea. A sensitive and selective method using gas chromatography–mass spectrometry (GC-MS) for the monitoring of 21 phytoestrogens was developed and fully validated. Phytoestrogens were extracted by liquid–liquid extraction using methyl tert-butylether as the solvent. Food samples were enzymatically hydrolyzed with β-glucuronidase/arylsulfatase. Before GC-MS, the analytes were derivatized to their trimethylsilyl derivatives by incubation with N,O-bis(trimethylsilyl)trifluoroacetamide with 1% trimethylchlorosilane for 30 min at 80°C. The calibration curves showed good linearity (r 2 > 0.99) in the range of interest for each analyte. The limits of detection and quantification of the 21 phytoestrogens were in the ranges of 0.5–20 and 1–50 ng/mL, respectively. The intra- and inter-day precisions were all below 15.7%. These multivariate procedures were efficient in determining the optimal conditions using peak heights as responses.

Background Lead (Pb), mercury (Hg), and cadmium (Cd) are well-known environmental pollutants. They are unnecessary in the biological processes of humans. This study was performed to estimate the representative background exposure levels to the metals by measuring concentrations in whole blood of the Korean general population. Methods This population-based cross-sectional study included 4,000 subjects (1,886 males and 2,114 females) 0–83 years of age in 2010 and 2011. Adult subjects (≥ 19 years of age) were collected by sex- and age-stratified probability method, and preschool- and school-aged subjects were recruited by a cluster sampling method. Written consent was provided prior to blood sampling. Pb and Cd blood concentrations were determined by a flameless atomic absorption spectrophotometry, and blood Hg was analyzed by a direct Hg analyzer. Results The geometric mean, median and 95th percentile of blood Pb was 1.82 µg/dL, 1.83 µg/dL, and 3.78 µg/dL, respectively. The respective values were 2.92 µg/L, 2.87 µg/L, 9.12 µg/L for Hg, and 0.56 µg/L, 0.59 µg/L, 2.20 µg/L for Cd. Blood Pb and Hg were higher in males than in females, but no sex difference was observed, respectively, in subjects 0–4 years of age for Pb and in subjects less than 20 years for Hg. However, blood Cd was higher in females than in males and no sex difference was observed in subjects < 30 years of age. Conclusion This study provides representative data of human exposure to Pb, Hg, and Cd covering whole age groups of the general population in Korea., Graphical Abstract

Metabolomics has focused on toxicological applications to (1) understand the mechanisms of toxicity, (2) identify novel biomarkers of toxicity, and (3) provide in vivo assessment in animal models through simple and fast methods to date. The toxicological effects of nonylphenol (NP) were evaluated after intraperitoneal injection of rats with 0, 50, and 250 mg kg(-1) day(-1) NP for four consecutive days. In the nontargeted approach, different extraction conditions were introduced to investigate the effects of NP on rats through gas chromatography/mass spectrometry (GC/MS). The GC/MS data obtained were further analyzed with partial least-squares discriminant analysis to compare toxicological effects between control and treated groups. The targeted approach was also used in combination with GC/MS to quantify endocrine hormones and to identify possible biomarkers in rat urine under optimal extraction conditions. In addition, we considered the metabolic trajectory to examine the metabolite profiles and patterns related to steroid metabolism in rats that were treated with NP, considering both treatment amount and time. The data suggest that tetrahydrocorticosterone and 5alpha-tetrahydrocorticosterone are possible urinary biomarkers of NP-induced toxicity. This metabolomic approach is a promising tool to assist with screening in toxicological studies.

Extracts of 33 samples of seaweed, shrimp, fish and shellfish, including two certified reference materials, were investigated for their contents of arsenic compounds (arsenic speciation).An anion exchange high performance liquid chromatography procedure was optimized to separate six arsenic compounds present in the seafood samples with dynamic reaction gas cell by inductively coupled plasma mass spectrometry. The concentration of each species in the sample were: arsenobetaines - 0.019-1.04 mg/kg, arsenocholine - 0.033-69.0 mg/kg, arseniousacid - ND-1.25 mg/kg, dimethylarsinate - ND-3.75 mg/kg, monomethylarsonate - ND-8.33 mg/kg, arsenic acid - ND-0.55 mg/kg. Additionally, unknown arsenic species were present in most of samples. The intake of inorganic arsenic via ingestion of the seafood samples that were analyzed did not represent a toxicological problem to humans. The limits of detection (LOD) were in the range of 0.5-2.5 µg/kg .

This study has attempted to establish an analysis method through validation against heavy metals in the body (Pb, Cd and Hg) using ICP-MS and Gold amalgamation and find out the relevance between heavy metal and Alzheimer’s disease after analyzing the distribution of heavy metal concentration (Pb, Cd and Hg) and correlations between a control group and Alzheimer’s disease group. In this study, Pb and Cd levels in the blood and serum were validation using ICP-MS. For analysis of Hg levels in the blood and serum, the gold amalgamation-based ‘Direct Mercury Analyzer’ has been used. According to an analysis on the heavy metal concentration (Pb, Cd and Hg concentration) in the blood, Cd concentration was high in the Alzheimer’s disease group. In the serum, on the contrary, Pb and Hg were high in the Alzheimer’s disease group. For analysis of correlations between heavy metal levels in the blood and serum and Alzheimer’s disease, t-test has been performed. Even though correlations were observed between the blood lead levels and Alzheimer’s disease, they were statistically insignificant because the concentration was higher in a control group. No significance was found in Cd and Hg. In the serum, on the other hand, no statistical significance was found between the heavy metal (Pb, Cd and Hg) and Alzheimer’s disease. In this study, no statistical significance was observed between heavy metal and decrease in cognitive intelligence. However, it appears that a further study needs to be performed because the results of the conventional studies were inconsistent.

Fifteen chlorination by-products were analyzed in 416 water samples collected from 35 water treatment plants in Korea from 1996 to 1998. These samples were divided into five groups according to water sources (Han-river, Nakdong-river, Youngsan-river, Kum-river and Cheju) and detected CBPs were classified into six classes (trihalomethanes; THMs, haloacetic acids; HAAs, haloacetonitriles: HANs haloketones; HKs, chloralhydrate; CH, chloropicrin; CP) and then, it was observed the detection tendency and frequency of CBPs in each water source. The total concentration of CBPs in treated water from Nakdong-river or Han-river was higher than those from the other rivers. And the distribution pattern of each class of CBPs was similar in all water sources. THMs were the highest portion in the range of 40-50%, and HAAs and HANs were 28-35 and 9-15%, respectively. And there was a strong correlation between HANs and HKs (r=0.813). Each and total concentrations of CBPs showed to be more affected by the water source in two-way analysis of variance (two-way ANOVA) among the concentration of CBPs, the source of water and season.