Kyung Su Park

Analysis of minor and trace elements in milk and yogurts by inductively coupled plasma-mass spectrometry (ICP-MS)

This study aimed at analysing the content of 22 minor and trace elements in milk and yogurts from South Korea, using inductively coupled plasma-mass spectrometry (ICP-MS), after digestion using heating block. The analytical method was validated by detection limits, precision, accuracy and recovery experiments, obtaining satisfactory results in all cases. Results of both minor and trace elements were found mostly similar in all varieties of milk and yogurts studied. Copper and manganese were comparatively high in fruit mixed yogurts, while selenium was high in milk samples. The overall concentrations of minor elements were found to have good nutritional values in accordance to RDA. Zn showed the highest concentration, followed by Rb, Se, Sr and Cr. The level of toxic trace elements, including As, Cd and Pb were very low and did not pose any threat to consumers.

Determination of toxic heavy metals and speciation of arsenic in seaweeds from South Korea

This study aimed at determining the levels of toxic heavy metals including As, Pb, Cd, Al, Hg and As species, such as, As-III, As-V, MMA, DMA, AsB, and AsC in various edible species of seaweeds from South Korea. ICP-MS was used for determination of As, Pb and Cd, ICP-OES was used for Al, DMA was used for Hg, and LC-ICP-MS was used for As speciation. The analytical methods were validated by linearity, detection limits, precision, accuracy and recovery experiments, obtaining satisfactory results in all cases. From the results toxic heavy metals were found in the decreasing order of: Al>As>Pb-Cd>Hg. Generally concentrations of all analysed heavy metals and both organic and inorganic species of As were very low compared to PTWIs specified by JECFA and EC. Their contribution to the overall intake by the subject seafoods was found very low and thus would not pose any threat to consumers.

Analysis of arsenic in rice grains using ICP-MS and fs LA-ICP-MS

With rice being the main staple crop in Asian countries such as China, Korea and Japan, the detection of arsenic (As), an element known to be carcinogenic to humans, has been the topic of high public interest. In this study, the total arsenic content in 200 white and 104 brown rice samples collected in Korea was analyzed using a Quadrupole Inductively Coupled Plasma-Mass Spectrometer (ICP-MS). One of the rice grain samples was polished with 3, 5, 7, 9 and 11 degrees of milling and arsenic concentration variance from the surface to the inner core region was investigated. Furthermore, spatial distribution of arsenic over the cross-section of a brown rice grain was obtained using femtosecond Laser Ablation-Inductively Coupled Plasma-Mass Spectrometry (fs LA-ICP-MS). For the total arsenic content analysis, 91.7 ± 28.1 and 101 ± 33.6 μg−1 kg−1 of arsenic were measured in the white and the brown rice, respectively. The fs LA-ICP-MS mapping image explains that the higher arsenic concentration in the brown rice is due to high arsenic distribution in the rice husk (protective covering of rice). Consequently, some degree of rice milling may be effective in the reduction of arsenic intake.

Chalcogenization-Derived Band Gap Grading in Solution-Processed CuInxGa1–x(Se,S)2 Thin-Film Solar Cells

Significant enhancement of solution-processed CuIn(x)Ga(1-x)(Se,S)2 (CIGSSe) thin-film solar cell performance was achieved by inducing a band gap gradient in the film thickness, which was triggered by the chalcogenization process. Specifically, after the preparation of an amorphous mixed oxide film of Cu, In, and Ga by a simple paste coating method chalcogenization under Se vapor, along with the flow of dilute H2S gas, resulted in the formation of CIGSSe films with graded composition distribution: S-rich top, In- and Se-rich middle, and Ga- and S-rich bottom. This uneven compositional distribution was confirmed to lead to a band gap gradient in the film, which may also be responsible for enhancement in the open circuit voltage and reduction in photocurrent loss, thus increasing the overall efficiency. The highest power conversion efficiency of 11.7% was achieved with J(sc) of 28.3 mA/cm(2), V(oc) of 601 mV, and FF of 68.6%.

Tripodal amphiphiles tunable for self-assembly to polymersomes

Cyclotriphosphazenes grafted with equimolar amounts of a hydrophilic polyethylene glycol and a hydrophobic oligopeptide in cis-nongeminal way form a new class of tripodal amphiphiles allowing both intra- and intermolecular hydrophobic interactions that differ from linear block copolymer amphiphiles. It has been found in this study that the tripodal amphiphiles can be tuned for self-assembly from micelles to bilayered polymersomes by controlling the hydrophobicity of the oligopeptide grafted. For instance, the tripodal amphiphiles with an intermediate hydrophobicity (0<log P<1) (P=[solute](n-octanol)/[solute](water)) reassemble from initially formed micelles into polymersomes, whereas the trimers bearing highly hydrophobic oligopeptides (log P>1) remain as stable micelles in aqueous solution. These biodegradable polymersomes exhibit outstanding physicochemical properties required for practical drug delivery and other biomedical applications. In particular, the cyclic phosphazene trimer platinated with a hydrophobic cis-bis(cyclohexylamine)Pt-moiety forms very stable polymersomes with excellent tumor selectivity by EPR effect and seems to be a promising candidate for preclinical studies.

Serum trace metal levels in Alzheimer's disease and normal control groups.

Objective: To determine whether serum trace metals are related to abnormal cognition in Alzheimer’s disease (AD). Methods: We studied serum lead (Pb), cadmium (Cd), mercury (Hg), and arsenic(As) in 89 patients with AD and in 118 cognitively normal individuals. We analyzed the results of the blood tests and the food intake. Results: Serum Pb levels correlated with word list recall (P = .039) and word list recognition (P = .037). Without age adjustment, serum Cd levels (P = .044) were significantly higher in the AD group. After stratified age adjustment, the levels of selected trace metals did not differ significantly between AD and normal individuals. Food intakes regarding selected trace metals were not significantly different between the 2 groups. Conclusions: In this study, serum Pb, Cd, Hg, and As levels were not directly related to abnormal cognition in AD. Serum Pb levels were significantly negatively correlated with verbal memory scores.

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.

Determination of toxic heavy metals in Echinodermata and Chordata species from South Korea

This study aimed at analysing concentrations of heavy metals including arsenic, lead, cadmium, aluminium and mercury in commonly consumed seafood species belonging to Echinodermata (Anthocidaris crassispina and Stichopus japonicus) and Chordata (Halocynthia roretzi and Styela plicata). The samples were digested by a microwave system and analysed for As, Cd and Pb by inductively coupled plasma mass spectrometer, for Al by inductively coupled plasma-optical emission spectrometer and Hg by Direct Mercury Analyser. The analytical method was validated by determining sensitivity, linearity, precision, spiking recoveries and analysis of the Standard Reference Material (SRM) NIST 1566-b, an Oyster Tissue. Results showed considerably higher accumulation of Al and As in analysed samples, compared to Pb and Cd, while Hg had the lowest contamination. On comparison, the obtained results with the recommended standards by the Food and Agriculture Organization, European Commission and Ministry of Food and Drug Safety of Korea, it was concluded that the analysed seafoods were safe and thus would not pose a threat to consumers.

Speciation of Arsenic in Rice by High-Performance Liquid Chromatography–Inductively Coupled Plasma Mass Spectrometry

ABSTRACT This study reports the optimization and validation of arsenic speciation of rice. Total arsenic was determined by inductively coupled plasma mass spectrometry; arsenite, arsenate, monomethylarsonic acid, and dimethyarsinic acid were quantified by high-performance liquid chromatography–inductively coupled plasma mass spectrometry. Methods using nitric acid and malonic acid were validated at various extraction conditions and mobile phase systems. The linear dynamic range, limit of detection, precision, fortification, and analysis of a white rice flour certified reference material (CRM-7503-a) were evaluated for quality assurance. The use of 5 mM malonic acid for extraction with an isocratic mobile phase was optimized for extraction time and temperature and employed for arsenic speciation in rice. The concentrations of total arsenic, arsenite, arsenate, monomethylarsonic acid, and dimethyarsinic acid were low compared to the provisional tolerable weekly intakes specified by the Food and Agriculture Organization/World Health Organization Joint Expert Committee on food additives and European food safety authority and thus do not pose a threat to consumers.

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.