NIST SRMs Research Articles

Characterizing the Organohalogen Iceberg: Extractable, Multihalogen Mass Balance Determination in Municipal Wastewater Treatment Plant Sludge.

The large number and diversity of organohalogen compounds (OHCs) occurring in the environment poses a grand challenge to analytical chemists. Since no single targeted method can identify and quantify all OHCs, the size of the OHC "iceberg" may be underestimated. We sought to address this problem in municipal wastewater treatment plant (WWTP) sludge by quantifying the unidentified fraction of the OHC iceberg using targeted analyses of major OHCs together with measurements of total and extractable (organo)halogen (TX and EOX, respectively; where X = F, Cl, or Br). In addition to extensive method validation via spike/recovery and combustion efficiency experiments, TX and/or EOX were determined in reference materials (BCR-461 and NIST SRMs 2585 and 2781) for the first time. Application of the method to WWTP sludge revealed that chlorinated paraffins (CPs) accounted for most (∼92%) of the EOCl, while brominated flame retardants and per- and polyfluoroalkyl substances (PFAS) accounted for only 54% of the EOBr and 2% of the EOF, respectively. Moreover, unidentified EOF in nonpolar CP extracts points to the existence of organofluorine(s) with physical-chemical properties unlike those of target PFAS. This study represents the first multihalogen mass balance in WWTP sludge and offers a novel approach to prioritization of sample extracts for follow-up investigation.

Comparison and validation of the QuEChERSER mega-method for determination of per- and polyfluoroalkyl substances in foods by liquid chromatography with high-resolution and triple quadrupole mass spectrometry

Instances of food contamination with per- and polyfluoroalkyl substances (PFAS) continue to occur globally, but sample preparation and analytical methods are quite limited and often monitor for a small percentage of known PFAS. This study aimed to evaluate, validate, and compare performance of two instruments with the recently developed “quick, easy, cheap, effective, rugged, safe, efficient, and robust” (QuEChERSER) sample preparation mega-method – a method developed to monitor chemicals over a broad range of physicochemical properties. Initial evaluation of the QuEChERSER mega-method for determination of PFAS in food demonstrated recoveries, matrix interferences, and co-extractive removal comparable to (or better than) US Food and Drug Administration (FDA) and USDA Food Safety and Inspection Service (FSIS) methods. Subsequent validation of QuEChERSER in beef, catfish, chicken, pork, liquid eggs, and powdered eggs on a high-resolution mass spectrometer achieved acceptable recoveries (70–120%) and precision (RSDs ≤20%) for all 33 target analytes at the 1 and 5 ng g−1 levels and 67–88% of analytes at the 0.1 ng g−1 level, depending on the matrix. Additional validation was performed by tandem mass spectrometry on a triple quadrupole instrument. This approach provided no non-detects and better recoveries at the 0.1 ng g−1 level than the HRMS method but exhibited more variability at 1 and 5 ng g−1 spiking levels. Analysis of NIST SRMs 1946 and 1947 gave accuracies of 70–117%. These results demonstrate the capability of combining PFAS analysis with a mega-method previously validated for 350 analytes, while collecting non-target data for future retrospective analysis of emerging alternatives with a high-resolution mass spectrometry method.

Validation of the QuEChERSER mega-method for the analysis of pesticides, veterinary drugs, and environmental contaminants in tilapia (Oreochromis Niloticus)

ABSTRACT Diverse food safety programmes around the world are designed to help ensure production of safe food. To meet this need, the development and implementation of more efficient and effective analytical methods to monitor residues (pesticides and veterinary drugs) and contaminants in food is important. In this study, we report the validation results for a simple high-throughput mega-method for residual analysis of 213 pesticides and veterinary drugs, including 15 metabolites, plus 12 environmental contaminants (polychlorinated biphenyls) in tilapia muscle for implementation in routine laboratory analyses. The generic sample preparation method and analytical approach are known as QuEChERSER (more than QuEChERS). A small portion of the initial extract (204 µL) is taken for analysis by ultrahigh-performance liquid chromatography (UHPLC) tandem mass spectrometry (MS/MS) covering 145 analytes, and the remaining extract undergoes a salting out step followed by an automated robotic instrument top sample preparation (ITSP) cleanup, also known as micro-solid-phase extraction (µSPE), plus fast low-pressure gas chromatography LPGC-MS/MS for 134 analytes (66 pesticides are targeted in both UHPLC-MS/MS and LPGC-MS/MS). The mega-method was validated in spiked tilapia samples at 5, 10, 15, and 20 ng/g with 10 replicates per level over two days (n = 80 overall), and 70–140% recoveries with RSDs ≤20% were achieved for 92% of the analytes in LC and 82% in GC. No significant matrix effects were observed for the analytes in LPGC-MS/MS, and only 5% of the analytes exceeded ±20% matrix effect in UHPLC-MS/MS. Analysis of standard reference materials (NIST SRMs 1946 and 1947) for contaminants in freeze-dried fish showed acceptable results, further demonstrating that the QuEChERSER mega-method can be implemented to expand analytical scope and increase laboratory efficiency compared to the QuEChERS method.

A sensitive vesicle mediated dispersive liquid-liquid microextraction of parts per quadrillion levels of beryllium from seawater samples prior to graphite furnace atomic absorption spectrometry determination

A rapid and highly sensitive vesicle mediated dispersive liquid–liquid microextraction procedure is developed for the determination of parts per quadrillion level of beryllium in seawater and air filter samples for providing its natural background and contamination levels. In this procedure, dioctylsulfosuccinate, an anionic vesicular surfactant and acetylacetone are used as dispersing and chelating agents, respectively. At pH > 9.5, beryllium forms hydrophobic beryllium-acetylacetonate complex spontaneously at room temperature. This complex is selectively filled into the vesicular cavities of dioctylsulfosuccinate and is extracted into small chloroform phase from bulk aqueous phase. The beryllium present in the chloroform phase is back extracted with dilute nitric acid and is analyzed by graphite furnace atomic absorption spectrometry. This method is applied to groundwater, seawater, coal fly ash, air filter and sea sludge samples. Under the optimized conditions, the limit of detection, limit of quantification and linear dynamic range are 10 fg mL−1, 33 fg mL−1 and 40–500 fg mL−1 for seawater; 0.15 ng g−1, 0.5 ng g−1 and 0.4–4 ng g−1 for air filter and 1.5 ng g−1, 0.39 ng g−1 and 0.4–4 ng g−1 for coal fly ash, respectively. For 1 L seawater sample an enrichment factor of 954 is achieved. Coefficient of determination (R2) is found to be 0.997. The recoveries are in the range of 94–105% at 200–500 fg mL−1. The relative standard deviations are 20%, 11%, 8% for ppq, ppt and ppb levels of Be, respectively. The accuracy of the procedure is verified by analyzing NIST SRMs 1640 and 1640a trace elements in natural water.

High-precision measurement of U-Pu-Np-Am concentrations and isotope ratios in environmental reference materials by mass spectrometry

We report results of precise and sensitive mass spectrometric measurements of uranium, plutonium, neptunium, and americium concentrations and isotope ratios in a variety of environmental reference materials. Most of our work has been done on NIST SRM 4350b, River Sediment, but we also present results for NIST SRM 4354, Lake Sediment; NIST SRMs 4355 and 4355a, Peruvian Soil; NIST SRM 4357, Ocean Sediment; NIST SRM 1648a, Urban Particulate Material; NIST SRM 1649b, Urban Dust; IAEA CRM 385, Ocean Sediment; USGS BCR-2, Columbia River Basalt; and USGS BHVO-2, Hawaiian Volcanic Observatory Basalt. These materials reflect a wide range in long-lived actinide concentrations (e.g. 1E4 to 1E10 atoms 239Pu/g) and isotope ratios. Measurements were performed in a clean laboratory by isotope dilution, multi-collector thermal ionization and multi-collector inductively coupled plasma mass spectrometry. In general, our results are in agreement with, but lower the uncertainty of, literature or certificate values for these reference materials. Our uranium results for the basalts also confirm previously reported high-precision mass spectrometric results from our laboratory. In many cases our measurements of U-Pu-Np-Am nuclides appear to be novel.Extensive results for NIST SRM 4350b, River Sediment, indicate that this material is heterogeneous for Pu-Np-Am concentrations and isotope ratios at a sample size of 5 g or lower. Pu–Np isotope ratios and a241Pu-241Am model age of 1954 reflect a mix of plutonium production operations at the nearby Hanford, Washington site, and global atmospheric fallout from nuclear weapons testing. Results for the oceanic sediment materials (NIST SRM 4357 and IAEA 385) collected near Sellafield, U.K. vary but are also indicative of local anthropogenic sources of varying Pu isotopic composition and a mean 241Pu-241Am model age of 1964. Large environmental fractionation between Pu and Np is observed for the ocean, river, and lake sediment reference materials. Novel measurements for the two air particulate SRMs indicate high U, Pu and Np concentrations for these collections in 1976–1977 with an anomalous regional fallout Pu isotopic signature. Results for BHVO-2 and other Hawaiian basalts indicate that those which erupted before or during the period of abundant atmospheric nuclear weapons testing (1950–1970) contain significant levels of Pu (on the order of 1E7 atoms 239Pu/g) with a global fallout Pu isotopic composition, compared to more recent eruptions which incorporated less Pu. Hence, Hawaiian basalts may provide an integrated temporal record of anthropogenic actinide fallout deposition from the atmosphere since eruption.

Trace element analysis of human seminal plasma: A cautionary tale of preanalytical variation and use of non-traditional matrices in human biomonitoring studies.

Ensuring harmonization of (ultra-)trace element measurements in non-traditional matrices is a particular analytical challenge that is highlighted in this work for seminal plasma as part of the developmental core at the Wadsworth Center Human Health Exposure Analysis Resource Targeted Laboratory. Seminal plasma was collected from 39 male partners of women undergoing in vitro fertilization and analyzed by inductively coupled plasma tandem mass spectrometry (ICP-MS/MS) following deproteinization with concentrated HNO3. Validation was accomplished using: 1) two aqueous NIST SRMs; 2) a seminal plasma QC pool, characterized via standard additions; 3) standard additions on a subset of samples; and 4) sample duplicates. Agreement with NIST certified or reference values were obtained to within ±15% for the SRMs, and agreement between aqueous calibration values and standard additions values agreed to within ±10-20% for all elements. Standard additions of seminal plasma samples revealed varying matrix effects for Cu and Cr that were not found for the pooled samples. Duplicate analyses agreed to within ±10-30% depending on element. A potential source of contamination in colloidal silica used for processing seminal plasma was identified that requires further study. Comparisons with literature indicate lack of consensus for As, Cd, Cr, Mn, Pb, and V content in seminal plasma. Further work is needed to improve harmonization of future studies.

Quality assurance and harmonization for targeted biomonitoring measurements of environmental organic chemicals across the Children's Health Exposure Analysis Resource laboratory network.

A consortium of laboratories established under the Children's Health Exposure Analysis Resource (CHEAR) used a multifaceted quality assurance program to promote measurement harmonization for trace organics analyses of human biospecimens that included: (1) participation in external quality assurance (EQA)/proficiency testing (PT) programs; (2) analyses of a urine-based CHEAR common quality control (QC) pool with each analytical batch across all participating laboratories; (3) method validation against NIST Standard Reference Materials® (SRMs); and (4) analyses of blinded duplicates and other project-specific QC samples. The capability of five CHEAR laboratories in organic chemical analysis increased across the 4-year period, and performance in the external PT program improved over time - recent challenges reporting >90% analytes with satisfactory performance. The CHEAR QC pools were analyzed for several classes of organic chemicals including phthalate metabolites and environmental phenols by the participating laboratories with every batch of project samples, which provided a rich source of measurement data for the assessment of intra- and inter-laboratory variance. Within-laboratory and overall variabilities in measurements across laboratories were calculated for target chemicals in urine QC pools; the coefficient of variation (CV) was generally below 25% across batches, studies and laboratories and indicated acceptable analytical imprecision. The suite of organic chemicals analyzed in the CHEAR QC pool was broader than those reported for commercially available reference materials. The accuracy of each of the laboratories' methods was verified through the analysis of several NIST SRMs and was, for example, 97±5.2% for environmental phenols and 95±11% for phthalates. Analysis of blinded duplicate samples showed excellent agreement and reliability of measurements. The intra-class correlation coefficients (ICC) for phthalate metabolites analyzed in various batches across three CHEAR laboratories showed excellent reliability (typically >0.90). Overall, the multifaceted quality assurance protocols followed among the CHEAR laboratories ensured reliable and reproducible data quality for several classes of organic chemicals. Increased participation in external PT programs through inclusion of additional target analytes will further enhance the confidence in data quality.

Three New Geochemical Reference Materials for Mineral Exploration and Environmental Contamination Studies: SdAR‐L2, SdAR‐M2 and SdAR‐H1

The preparation and characterisation of three new sediment‐based reference materials SdAR‐L2 (blended sediment), SdAR‐M2 (metal‐rich sediment) and SdAR‐H1 (metalliferous sediment) described in this paper involved collaboration between the United States Geological Survey (USGS) and International Association of Geoanalysts (IAG). Sediments and soils from six locations in the western United States were mixed according to a USGS‐designed blending programme that calculates the proportions of source materials required to match target mass fractions and minimise the number of elements with mass fractions below instrument detection limits. For selected element mass fractions, NIST SRMs 2709–2711 provided target values. By using this approach, the three reference materials retained a natural mineralogy that is so essential for matching matrix and dissolution characteristics. Geochemical characterisation of these materials was carried out through the IAG GeoPT proficiency testing programme. Three independent rounds of GeoPT testing were used, each providing results from over eighty laboratories. Contributed results were statistically evaluated to produce reference values for over forty elements in each material. Reference and information values as well as mineralogical compositions are presented to establish these samples as reference materials, especially for use in mineral exploration and environmental contamination monitoring studies.

Semi-automated high-throughput method for residual analysis of 302 pesticides and environmental contaminants in catfish by fast low-pressure GC–MS/MS and UHPLC-MS/MS

A fast, fit-for-purpose, high-throughput method was developed and validated for the analysis of 302 targeted contaminants in catfish muscle. Targeted contaminants included pesticides and metabolites with US regulatory levels, plus other lipophilic pesticides and environmental contaminants: PAHs, PCBs, PBDEs and other flame retardants. The sample preparation was based on QuEChERS extraction. The extract was split and analyzed by UHPLC-MS/MS for 128 analytes after filtering and by low pressure (LP) GC–MS/MS for 219 analytes after an automated robotic micro-SPE cleanup. The method was validated at four spiking levels (5, 10, 20 and 40 ng/g) with 10 replicates per level, and satisfactory recoveries (70–120%) and RSDs (≤20%) were achieved for 80% of the analytes. The method was further validated with NIST SRMs 1946 and 1947 and applied for the analysis of 22 market fish samples. Six pesticides and one PAH were found in the market fish samples, all below US regulatory levels.

Improvement of the Ca determination accuracy with k 0-INAA using an HPGe coaxial detector with extended energy range efficiency calibration

We show that use of the radionuclide 56Co for calibration of the full energy peak efficiency, e, of a coaxial HPGe detector, in addition to the commonly employed set of activity standards (133Ba, 241Am, 152Eu, 57Co, 137Cs, 88Y, 65Zn), affects significantly the e values in the high energy region. This change resulted in substantial improvement of the accuracy of Ca determination by k 0-INAA via the 49Ca radionuclide, which emits predominantly the 3084 keV photons, as demonstrated by Ca results in NIST SRMs 1547 Peach Leaves, 1633b constituent elements in coal fly ash, and 2711 Montana II Soil.

Simultaneous determination of low Z elements in barium borosilicate glass samples by in situ current normalized particle induced gamma-ray emission methods

Particle induced gamma-ray emission (PIGE) method using 4 MeV proton beam was utilized to analyze two types of barium borosilicate glass (BaBSG) samples for quantification of concentrations of low Z elements. The in situ current normalization method was applied in the analysis of eight samples containing varying concentration of F along with Si, B and Na. Charge normalized PIGE method was applied to determine concentrations of above low Z elements including Li and Al in samples having simulated nuclear waste from reprocessing of thoria spent fuel. Synthetic samples and NIST SRMs were used for method validation.

Simultaneous Determination of Arsenic, Cadmium, Mercury, and Lead in Raw Ingredients, Nutritional Products, and Infant Formula by Inductively Coupled Plasma Mass Spectrometry: Single-Laboratory Validation.

A method was developed for the determination of As, Cd, Hg, and Pb in raw ingredients, nutritional products, and infant formula using inductively coupled plasma mass spectrometry (ICP-MS). Three raw ingredients (acid casein, maltodextrin, skim milk powder) and three standard reference materials [NIST 1548a (Typical Diet), NIST 1577c (Bovine Liver), NIST SRM 1568b (Rice Flour)] obtained from the National Institute of Standards and Technology were analyzed by two analysts using two ICP-MS instruments in different laboratories. NIST SRM 1568b was used as the control sample. All protocol validation parameters (intermediate precision, accuracy, linearity, quantitation limit, specificity, and robustness) were met. The overall precision (n = 8) for analyte concentrations (2.5-300 ng/g) ranged from 2 to 14% RSD. Spike recoveries ranged from 88 to109% for spike levels between 25 and 200%. The overall average concentration of As, Cd, Hg, and Pb measured in all three NIST SRMs were within the certified value ranges. Good linearity (correlation coefficient (r) = 0.9995 or better) was obtained for all analytes. Control chart results for 8 independent days showed that the method is robust (precision values of 10% and all points within ±3 σ were obtained). Excellent specificity was also demonstrated when the analytes were measured in the presence of high concentrations of the other concomitants.

Feasibility study of k 0-INAA at the ITU TRIGA Mark II research reactor, Turkey

This work is focused on testing the implementation of k 0-INAA using Kayzero for Windows and k0-IAEA software packages at the ITU TRIGA Mark II research reactor. The neutron spectrum parameters were determined using the bare triple-monitor method with Au and Zr monitors. The k 0-INAA performance was tested by analysis of NIST SRMs 2711 Montana Soil and 1547 Peach Leaves. The performance assessment based on the E n criterion showed that the concentrations of a number of elements in both NIST SRMs determined by both software packages are in agreement with NIST values.

Determination of Sulfur in Bio-Samples by ICP-QMS/QMS with an ORC

A method for determination of sulfur was investigated using an inductively coupled plasma tandem quadrupole mass spectrometer (ICP-QMS/QMS) with an octopole reaction/collision cell (ORC). It helped to achieve a lower background equivalent concentration (BEC) and a lower detection limit (DL) when 10% HNO3 with 10% ethanol was applied as the rinse solution. Sulfur measurement was carried out by shifting the measured mass from 32S+ to 32S16O+ by reaction with O2 gas. The introduction of H2 together with O2 as reaction gases provided a lower DL. The BEC and DL of 32S were 0.83 ng g-1 and 0.03 ng g-1, respectively. The validation of the present method was confirmed by determining sulfur in certified reference materials, NIST SRMs 2773, 2298, and 2299. The results of sulfur in amino-acids and protein indicate that determination of sulfur could be an effective technique for quantification of sulfur-containing amino acids and proteins.

Selenium contents in Korean snack and dairy products (826.1)

Se is a trace micro‐mineral and antioxidant protecting human body from the free radical induced lipid peroxidation. However, there are little reports on the Se intake status of Koreans because of deficient Se database on foods. Furthermore, the accuracy of existing data is questionable because they were usually analysed using methods as pre‐treatment process such as wet digestion or dry digestion, which can cause selenium loss. This study was aimed to evaluate Se contents in edible portion of snack and dairy products by instrumental activation analysis(=INAA) method using freeze‐drying as a pre‐treatment process. The most frequently consumed snacks and dairy products by Korean were selected for the analysis of Se contents. To minimize contamination, all the instruments and storage tools were used after washing with HNO3. Each food samples were individually mixed using homogenizer equipped with titanium blade. The homogenized food samples of 10~20g were freeze‐dried at temperature of ‐60 C for 24~96 h and subsequently, used to analyze Se contents by IINAA‐method. Analytical quality control was conducted using NIST SRMs. The analysis limit of Se in foods by INAA was 0.01ppm. Se contents in processed foods were in the range of 0.22ug~14.9ug in 100g foods. The Se contents were various according to the type of processed foods. The average Se contents in 100g sandwich, snack, milk, soy milk, joghurt were presented. This result will be useful in establishing the food Se database for Koreans.Grant Funding Source: Korean Research Foundation

Verification of k 0-NAA results at the LVR-15 reactor in Řež with the use of Au+Mo+Rb(+Zn) monitor set

Long-time experience in neutron flux moni- toring on irradiation in the LVR-15 research reactor in R y ez y proved that Au?Mn?Rb and Au?Mo?Rb(?Zn) monitor sets for short and long irradiation, respectively, are more suitable in our conditions than the most frequently used Au?Zr set. The advantages of the former monitor set have been described previously, in the present work we discuss the advantages of the latter monitor set for long irradiations in varying active core configurations of the LVR-15 reac- tor. The successful application of the Au?Mo?Rb(?Zn) monitor set has been verified by comparative determination of the neutron flux parameters a (epithermal flux distribu- tion parameter), f (thermal-to-epithermal neutron flux ratio), and Fc,Au (comparator factor) using this and the Au?Zr monitor set, and by analyses of certified reference materials, namely NIST SRMs 1547 Peach Leaves, 2711 Montana Soil, and 1633b Trace Elements in Coal Fly Ash.

Quantification of complex polycyclic aromatic hydrocarbon mixtures in standard reference materials using comprehensive two-dimensional gas chromatography with time-of-flight mass spectrometry

This research is the first to quantify complex PAH mixtures in NIST SRMs using comprehensive two-dimensional gas chromatography coupled to time-of-flight mass spectrometry (GC×GC/ToF-MS), with and without extract cleanup, and reports previously unidentified PAH congeners in the NIST SRMs. We tested a novel, high orthogonality GC column combination (LC-50×NSP-35), as well as with a commonly used column combination (Rtx-5ms×Rxi-17) for the quantification of a complex mixture of 85 different PAHs, including parent (PAHs), alkyl- (MPAHs), nitro- (NPAHs), oxy- (OPAHs), thio- (SPAHs), bromo- (BrPAHs), and chloro-PAHs (ClPAHs) in extracts from two standard reference materials: NIST SRM1650b (diesel particulate matter), with cleanup and NIST SRM1975 (diesel particulate extract), with and without extract cleanup. The LC-50×NSP-35 column combination resulted in an average absolute percent difference of 33.8%, 62.2% and 30.8% compared to the NIST certified PAH concentrations for NIST SRM1650b, NIST SRM1975 with cleanup and NIST SRM1975 without cleanup, while the Rtx-5ms×Rxi-17 resulted in an absolute percent difference of 38.6%, 67.2% and 79.6% for NIST SRM1650b, NIST SRM1975 with cleanup and NIST SRM1975 without cleanup, respectively. This GC×GC/ToF-MS method increases the number of PAHs detected and quantified in complex environmental extracts using a single chromatographic run. Without clean-up, 7 additional compounds were detected and quantified in NIST SRM1975 using the LC-50×NSP-35 column combination. These results suggest that the use of the LC-50×NSP-35 column combination in GC×GC/ToF-MS not only results in better chromatographic resolution and greater orthogonality for the separation of complex PAH mixtures, but can also be used for the accurate quantification of complex PAH mixtures in environmental extracts, such as diesel particulate matter, without silica gel cleanup.

Development and Validation of Primary Method for the Determination of Glucose in Human Serum by Isotope Dilution Liquid Chromatography Tandem Mass Spectrometry and Comparison with Field Methods

Glucose is a common medical analyte measuring in human serum or blood samples. The development of a primary method is necessary for the establishment of traceability in measurements. We have developed an isotope dilution liquid chromatography tandem mass spectrometry as a primary method for the measurement of glucose in human serum. Glucose and glucose-<TEX>$^{13}C_6$</TEX> in sample were ionized in ESI negative mode and monitored at mass transfers of m/z 179/89 and 185/92 in MRM, respectively. Glucose was separated on <TEX>$NH_2P$</TEX>-50 2D column, and the mobile phase was 20 mM <TEX>$NH_4OAc$</TEX> in 30% acetonitrile/70% water. Verification of this method was performed by the comparison with NIST SRMs. Our results agreed well with the SRM values. We have developed two levels of glucose serum certified reference material using this method and distributed them to the clinical laboratories in Korea as samples for proficiency testings. The expended uncertainty was about 1.2% on 95% confidence level. In proficiency testings, the results obtained from the clinical laboratories showed about 3.6% and 3.9% RSD to the certified values. Primary method can provide the traceability to the field laboratories through proficiency testings or certified reference materials.

Analysis of Se contents in Korean processed foods according to food type

Selenium is an essential micro‐mineral and antioxidant protecting from the free radical induced lipid peroxidation. However, there are little reports on the Se nutritional status of Koreans because of deficient Se database on foods. This study was aimed to evaluate Se contents in edible portion of processed foods using instrumental activation analysis (=INAA) method, which cause little Se loss during pre‐treatment. The most frequently consumed processed foods by Korean were selected for the analysis of Se contents. Each food samples were individually mixed using homogenizer made with titanium. The homogenized food samples of 10~20g were freeze‐dried at temperature of −60 C for 24~96 h and subsequently, used to analyze Se contents by INAA‐method. Analytical quality control was conducted using NIST SRMs. The analysis limit of Se in foods by INAA was 0.01ppm. Se contents in processed foods ranged from 0.22ug to 14.9ug in 100g foods. The selenium contents were various according to the type of processed foods. The mean Se contents in 100g Ramen, which is one of the most consumed foods among Koran people, was in 8.6ug. The selenium contents were 8.4ug, 6.4ug, 1.4ug in 100g cold noddle, wonton and instant coffee mixture, respectively. This result will be useful in establishing the food Se database for Koreans.Grant Funding Source: National Reserch Foundtion of Korea

Activity of GSHpx and toenail Se contents in Korean young adults

Selenium, is a key constituent of enzyme, glutathione peroxidase, so effective in decreasing various oxidative stress. Toenail selenium level is a long term indicator for selenium nutritional status. The low activity of glutathione peroxidase in RBC is known to indicate a state of selenium deficiency. This study is aimed to measure the toenail selenium levels in Korean young adult and GSHpx activity in young adults. For the measurement of toenail selenium content, the instrumental activation analysis (=INAA) method was employed. Serums were subsequently used to analyze glucose and insulin level. The RBC was used to analyze the GSHpx activity. Toenail were washed in ultra‐sonicator and freeze‐dried at temperature of −60 C for 12~24 h. The toenail selenium contents were measured by INAA method using HANARO‐reactor. Analytical quality control was conducted using NIST SRMs. The toenail Se level and RBC GSHpx did not show significant difference by gender in our study participants. The toenail selenium status and GSHpx activity did not show significant correlation with insulin and glucose, but with c‐reactive protein level. This result suggests that the selenium status would be associated with inflammation in young adult and showed a vast research on the selenium status in Korean people is necessary for the evaluation of selenium association with risk factors for health.Grant Funding Source: National Research Foundation of Korea