Inductively Coupled Plasma Mass Spectrometry Method Research Articles

Effect of Wastewater Sample Pre-Treatment on Determination of Selected Heavy Metals Using ICP-MS Method

Polychlorinated substances, polyaromatic hydrocarbons, heavy metals and pesticides are among the priority even at low concentrations. The problem, however, is that such low concentrations are impossible to measure using most available methods. This researchfocused on the determination of selected priority substances – heavy metals, namely lead and cadmium, in which the determination ofPb and Cd in wastewater by Inductively Coupled Plasma Mass Spectrometry (ICP-MS) was preceded by water sample pre-treatment.The paper deals with the influence of the pre-treatment on the resulting measured values. Two processes were selected as pre-treatmentprocesses. The first pre-treatment procedure was a simple filtration using a filter paper for moderate filtration. As the second procedure, we applied decomposition of the sample by nitric acid in the open system. The pre-treated wastewater samples were subsequentlyexamined using ICP-MS. Based on the obtained results, we can conclude that decomposition of the sample by nitric acid in the opensystem is a more suitable pre-treatment method for water samples

Concentration-dependent Differences in Urinary Iodine Measurements Between Inductively Coupled Plasma Mass Spectrometry and the Sandell-Kolthoff Method

A large amount of historical data regarding urinary iodine concentration (UIC) were measured with the Sandell-Kolthoff (S-K) method for iodine nutrition surveillance. The congruence in urinary iodine measurements between inductively coupled plasma mass spectrometry (ICP-MS) and the S-K method has been debated. A total of 2064 adult urine samples were included in the present study. The UIC measurement results obtained simultaneously by standardized ICP-MS and the S-K method were analyzed. The UIC obtained with ICP-MS was significantly higher than that obtained with the S-K method (158 μg/L vs. 148 μg/L, p < 0.001). The Bland-Altman difference plot showed a small but significant mean difference of 6.12 μg/L between the two methods. The stratified analysis showed that the correlation coefficient was higher in the UIC < 300 μg/L group than the UIC ≥ 300 μg/L group (0.93 vs. 0.88, p = 0.0001). The mean difference between the S-K and ICP-MS methods was positively correlated with the UIC. The ICP-MS and S-K methods were comparable when the UIC was less than 300 μg/L; however, UIC values between 300 and 600 μg/L should be compared with caution after considering the research objective. We do not suggest comparing UICs obtained from the ICP-MS and S-K methods in iodine monitoring studies if the UIC is greater than 600 μg/L.

Arsenic and Lead Determination in D&C Red No. 6 Lakes and D&C Red No. 7 Lakes Containing Barium Sulfate Using X-Ray Fluorescence Spectrometry.

Color additives requiring batch certification by the U.S. Food and Drug Administration have Code of Federal Regulations (CFR) specification limits for certain elements and are usually analyzed by x-ray fluorescence spectrometry (XRF). However, analysis of some color additives presents difficulties. An XRF method was developed for quickly determining whether barium sulfate-containing color additives certifiable as D&C Red No. 6 lakes and D&C Red No. 7 lakes meet the CFR specifications for arsenic (As) and lead (Pb). Difficulties in preparing XRF standards and analyzing As and Pb in matrices with the heavy x-ray absorber barium (Ba) were overcome by first preparing As- and Pb-fortified cellulose, then blending color additive samples with fortified and unfortified cellulose to produce XRF calibration materials. Satisfactory compensation for changes in intensity caused by Ba absorption was achieved by measuring varying concentrations of As and Pb at several concentrations of Ba. Test samples of barium sulfate-containing D&C Red No. 6 lakes and D&C Red No. 7 lakes were analyzed by the XRF method and by an inductively coupled plasma-mass spectrometry (ICP-MS) method. The ICP-MS method poses some difficulties and is time consuming. In contrast, the XRF method requires very little sample preparation, is nondestructive, uses calibrations that are stable for long periods of time, and offers acceptable determination limits (1 mg/kg As, 4 mg/kg Pb) which are less than the CFR specification limits (3 mg/kg As, 20 mg/kg Pb). The new XRF method is applicable for use in routine batch certification.

Establishment and application of a new serum sodium candidate reference method

BackgroundLevels of serum sodium (Na) are widely determined in clinical laboratories. Accordingly, sodium quantification must be performed using reliable methods. Herein are reported the results of the evaluation of a new inductively coupled plasma mass spectrometry (ICP-MS) method for sodium quantification. MethodsSerum samples were diluted 100 × by 0.3% ultrapure nitric acid, and germanium (Ge) was used as an internal standard. Sodium calibration solutions with different concentrations were added to serum matrix solutions. The serum sodium concentration was calculated according to the standards addition method. The analytical performance of the method, as well as a comparison with other sodium method, was investigated. ResultsThe correlation coefficients (r) between the measured Na/Ge ratios and the analyte concentration ratios were all > 0.9999. Intra- and between-assay coefficients of variation (CVs) were < 0.64% and < 0.57%, respectively, and the total CV was < 0.67%. The trueness of the method was verified by measuring a certified reference material, SRM 956d. The new ICP-MS method was compared with the 2017 and 2018 External Quality Assessment Scheme for Reference Laboratories in Laboratory Medicine (RELA). The results were well correlated with those obtained by the routine indirect ion selective electrode (ISE) method: sodium (ICP-MS, mmol/L) = 0.9895 × sodium (ISE, mmol/L) + 1.3049 (r = 0.9914, n = 40). The mean deviation between the results of the ICP-MS method and the indirect ISE method was –0.15%. ConclusionsThe new ICP-MS method proved to be accurate, reliable, simple, and fast and may be used as a candidate reference method for setting target values in the standardization of serum sodium measurements.

Simultaneous multielement analysis by ICP-MS with simple whole blood sample dilution and its application to uremic patients undergoing long-term hemodialysis

Few studies were reported on trace elements’ alterations in uremic patients undergoing long-term (>24 months) hemodialysis (HD), especially by using the whole blood as the biological fluid for the measuring purpose. Our objective was to develop an improved micro-sampling inductively coupled plasma-mass spectrometry (ICP-MS) method to determine the levels of Ca, Mg, Cu, Zn, Fe, Mn, Se and Pb in uremic patients receiving long-term HD. A ICP-MS method with a modified whole blood sample preparation procedure with small volumes was established and applied for the simultaneous quantification of the various elements in uremic patients undergoing long-term HD. 124 eligible uremic patients receiving long-term HD (75 males and 49 females) and 77 healthy subjects (54 males and 23 females) were recruited and Ca, Mg, Cu, Zn, Fe, Mn, Se and Pb levels were further determined. Our results revealed that uremic patients with HD had significantly higher blood levels of Ca, Mg, Zn and Pb and lower Cu, Fe, Se and Mn concentrations than healthy controls. In conclusion, a reproducible and reliable ICP-MS method using minimal whole blood sample volume (50 μL) with a simple dilution-based preparation procedure was successfully improved, validated and applied. Uremic patients undergoing long-term HD might be at increased risk of some essential trace elements deficiency (especially for Cu, Fe and Se) or toxic trace element excess (Pb) in respect to healthy subjects. Monitoring of blood levels and supplementation of some trace elements may be indicated in uremic patients undergoing long-term HD.

ОПРЕДЕЛЕНИЕ НИЗКИХ СОДЕРЖАНИЙ (МЕНЕЕ 0,0005% (ПО МАССЕ)) МЫШЬЯКА В НИКЕЛЕВЫХ СПЛАВАХ МЕТОДАМИ ИСП-МС И ААС С ЭЛЕКТРОТЕРМИЧЕСКОЙ АТОМИЗАЦИЕЙ

In this work, the determination of low contents (less than 0,0005 wt. %) of arsenic in complex alloyed samples of nickel alloys was carried out by means of inductively coupled plasma mass spectrometry (ICP-MS) and atomic absorption spectrometry with electrothermal atomization. Also, the ICP-MS method was used to determine the arsenic content in chromium, which is an alloying component of nickel alloys. A technique for dissolving a sample and preparing it for analysis is presented. Spectral interferences are eliminated by applying mathematical correction equations, a reaction-collision cell and using corrective additives. The correctness of the results obtained is confirmed by the analysis of certified reference materials of nickel alloys and chromium.

Contribution to the study of selected heavy metals in urban wastewaters using ICP-MS method

Heavy metals pose a significant risk to all environmental elements and human health. The danger lies in the fact that they can be toxic even at low concentrations. For this reason, inductively coupled plasma mass spectrometry (ICP-MS) was chosen from all available methods to monitor the concentration of selected heavy metals. In comparison with other methods, very low concentrations of monitored substances (in μg/l) can be determined by ICP-MS.This paper deals with the monitoring of the concentration of selected heavy metals at the inlet and outlet of the municipal wastewater treatment plant, namely lead, cadmium and nickel. The results show that the purification process has a positive effect on the reduction of the concentration of heavy metals in wastewater.

Исследование состава мха – естественного биоиндикатора для мониторинга воздуха Восточно-Казахстанской области

Here are the results of determining the chemical composition of moss in the East Kazakhstan region. The following research stages were carried out: harvesting plant materials; methods of taking samples of the studied material for analysis; determination of the concentration of elements by inductively coupled plasma mass spectrometry (ICP-MS). Developed methods for dry and wet ashing bioindicator. The results of the analysis of moss obtained by the ICP-MS method and the instrumental neutron activation analysis (INAA) method are compared. The reliability of the results of the analysis by the method of additives and photometric determination of the concentration of elements was determined.

A novel screening method for transition metal-based anticancer compounds using zebrafish embryo-larval assay and inductively coupled plasma-mass spectrometry analysis.

As novel metallodrugs continue to emerge, they are evaluated using models, including zebrafish, that offer unique sublethal endpoints. Testing metal-based anticancer compounds with high-throughput zebrafish toxicological assays requires analytical methods with the sensitivity to detect these sublethal tissue doses in very small sample masses (e.g., egg mass 100μg). A robust bioanalytical model, zebrafish embryos coupled with inductively coupled plasma-mass spectrometry (ICPMS) for measurement of delivered dose, creates a very effective means for screening metal-based chemotherapeutic agents. In this study, we used ICPMS quantitation with the zebrafish embryo assays to detect metal equivalents at multiple response endpoints for two compounds, the chemotherapeutic agent cisplatin and ruthenium (Ru)-based prospective metallodrug, PMC79. We hypothesized that cisplatin and PMC79 have different mechanisms for inducing apoptosis and result in similar lesions but different potencies following water-borne exposure. An ICPMS method was developed to detect the metal in waterborne solution and tissue (detection limit: 5 parts per trillion for Ru or platinum [Pt]). The Ru-based compound was more potent (LC50 : 7.8μm) than cisplatin (LC50 : 158μm) and induced disparate lesions. Lethality from cisplatin exposure exhibited a threshold (values >15mg/L) while no threshold was observed for delayed hatching (lowest observed adverse effect level 3.75mg/L cisplatin; 8.7 Pt (ng)/organism). The Ru organometallic did not have a threshold for lethality. Cisplatin-induced delayed hatching was investigated further by larval-Pt distribution and preferentially distributed to the chorion. We propose that zebrafish embryo-larval assays coupled with ICPMS serve as a powerful platform to evaluate relative potency and toxic effects of metallodrug candidates.

Determinations of uranium concentrations in soil, water, vegetables and biological samples from inhabitants of war affected areas in eastern Croatia (ICP-MS method)

The occurrence of elevated uranium levels in post-war areas raise concerns among populations, especially in areas affected by heavy bombardment and potential use of depleted uranium weapons. The aim of this study was to assess public exposure to the uranium Water, soil, vegetables, urine, serum and hair samples were collected for the first time in eastern Croatia and analysed using an inductively coupled plasma mass spectrometry (ICP-MS) method, in order to try to explain the possible origins of uranium in the population and environment. Urine, serum and hair samples were collected from 389 inhabitants. A large variation of uranium concentrations in urine, serum and hair samples was found in this study. The majority of urine, serum and hair samples from our study had uranium concentrations below the reference literature values. A higher uranium concentration in the hair of 4% of inhabitants, mostly from rural areas, could not be explained at this stage of research. A further, extended epidemiological study should be made of uranium in the region.

Validation of a simple inductively coupled plasma mass spectrometry method for detecting urine and serum iodine and evaluation of iodine status of pregnant women in Beijing

Rapid and simple method for serum and urine iodine is necessary for iodine-related diseases. This study aimed to establish and validate a simple and rapid method for quantification of iodine in human urine and serum using inductively coupled plasma mass spectrometry (ICP-MS). Generally, samples were diluted using water with 1.5% isopropanol and 7 mmol hydrous ammonium before analysis by the ICP-MS. Performance of the method was validated, and the urine and serum iodine levels of 72 pregnant women were analyzed. Results showed that the lower limit of detection of the ICP-MS method was 0.87 µg/L. No significant memory effects were observed. Recovery in both serum and urine was approximately 100%. Compared with NIST SRM3668, bias was <1%, exhibiting good accuracy. The inter-run coefficients of variation (CVs) for serum and urine iodine were 2.8–3.5% and 3.5–6.7%, respectively, and total CVs for serum and urine iodine were 3.2–3.7% and 3.9–6.7%, respectively. Comparison of the iodine results obtained by the ICP-MS method and the conventional S–K method revealed excellent correlation (r = 0.984, mean bias = –1.7%). The median urine iodine of pregnant women (125.5 μg/L) was lower than that of WHO criteria for iodine deficiency (median urinary iodine <150 μg/L) while 55.6% of the individuals with urine iodine level less than 150 μg/L. The median serum iodine level of the pregnant women was 69.0 μg/L. In conclusion, a rapid and simple ICP-MS method for urine and serum iodine measurements has been established and validated, and the pregnant women in Beijing may still suffer from insufficient iodine intake.AbbreviationsCVcoefficients of variationHPLChigh-performance liquid chromatographyICP-MSinductively coupled plasma mass spectrometryKEDkinetic energy discriminationKIpotassium iodideLODlimit of detectionS–KSandell–Kolthoff reactionPUMCHPeking Union Medical College Hospital

A preliminary investigation of metal element profiles in the serum of patients with bloodstream infections using inductively-coupled plasma mass spectrometry (ICP-MS)

BackgroundWe determined metal element profiles (MEPs) by inductively-coupled plasma mass spectrometry (ICP-MS) in the serum of patients with blood stream infection (BSI) and find out very important (VIP) metal elements in specific infections. MethodsSixty-eight metal elements were identified in both serum and the bacteria isolated from 14 BSI patients with Staphylococcus infection, 39 with Enterobacteriaceae infection, 5 with Enterococcus infection and 58 healthy subjects without infection by ICP-MS methods. Statistical analysis, Principal Component Analysis (PCA) and Partial Least Squares Discriminant Analysis (PLS-DA) were performed to process data among different groups, select differential metal elements and operate correlation analysis. ResultsThe MEPs in the serum of BSI patients with 4 types of bacteria (Staphylococcus aureus, Escherichia coli, Enterococcus faecium, and Klebsiella pneumonia), and the corresponding MEPs of the bacteria were established. VIP metal elements were screened out in different BSI patients. Correlation analysis showed that there were some correlations between serum concentrations of metal elements and bacterial infection. ConclusionWe found differential metal elements in the serum of BSI patients compared with controls, thus providing a basis for the diagnosis, prevention and treatment of BSI from the perspective of metallomics.

Determination of Non-Transferrin Bound Iron, Transferrin Bound Iron, Drug Bound Iron and Total Iron in Serum in a Rats after IV Administration of Sodium Ferric Gluconate Complex by Simple Ultrafiltration Inductively Coupled Plasma Mass Spectrometric Detection.

A rapid, sensitive and specific ultrafiltration inductively-coupled plasma mass spectrometry method was developed and validated for the quantification of non-transferrin bound iron (NTBI), transferrin bound iron (TBI), drug bound iron (DI) and total iron (TI) in the same rat serum sample after intravenous (IV) administration of iron gluconate nanoparticles in sucrose solution (Ferrlecit®). Ultrafiltration with a 30 kDa molecular cut-off filter was used for sample cleanup. Different elution solvents were used to separate each form of iron from sample serum. Isolated fractions were subjected to inductively-coupled mass spectrometric analysis after microwave digestion in 4% nitric acid. The reproducibility of the method was evaluated by precision and accuracy. The calibration curve demonstrated linearity from 5–500 ng/mL with a regression (r2) of more than 0.998. This method was effectively implemented to quantify rat pharmacokinetic study samples after intravenous administration of Ferrlecit®. The method was successfully applied to a pharmacokinetic (PK) study of Ferrlecit in rats. The colloidal iron followed first order kinetics with half-life of 2.2 h and reached background or pre-dose levels after 12 h post-dosing. The drug shown a clearance of 0.31 mL/min/kg and volume of distribution of 0.05 L/kg. 19.4 ± 2.4 mL/h/kg.

A validated inductively coupled plasma mass spectrometry (ICP-MS) method for the quantification of total platinum content in plasma, plasma ultrafiltrate, urine and peritoneal fluid

Oxaliplatin is a platinum (Pt)11HIPEC, hyperthermic intraperitoneal perioperative chemotherapy; HNO3, nitric acid; Pt, platinum; RE, relative error; Tb, terbium. containing antineoplastic agent that is applied in current clinical practice for the treatment of colon and appendiceal neoplasms. A fully validated, highly sensitive, high throughput inductively coupled plasma mass spectrometry (ICP-MS) method is provided to quantify the total Pt content in plasma, plasma ultrafiltrate, urine and peritoneal fluid. In this ICP-MS approach, the only step of sample preparation is a 1000-fold dilution in 0.5% nitric acid, allowing the analysis of 17 samples per hour. Detection of Pt was achieved over a linear range of 0.01–100 ng/mL. The limit of quantification was 18.0 ng/mL Pt in plasma, 8.0 ng/mL in ultrafiltrate and 6.1 ng/mL in urine and peritoneal fluid. The ICP-MS method was further validated for inter-and intraday precision and accuracy (≤15%), recovery, robustness and stability. Short-term storage of the biofluids, for 14 days, can be performed at −4 °C, −24 °C and −80 °C. As to long-term stability, up to 5 months, storage at −80 °C is encouraged. Furthermore, a timeline assessing the total and unbound Pt fraction in plasma and ultrafiltrate over a period of 45 h is provided. Following an incubation period of 5 h at 37 °C, 19–21% of Pt was recovered in the ultrafiltrate, emphasizing the extensive and rapid binding of oxaliplatin-derived Pt to plasma proteins. The described method can easily be implemented in a routine setting for pharmacokinetic studies in patients treated with oxaliplatin-based hyperthermic intraperitoneal perioperative chemotherapy.

Synthesis of ZnO Thin Films Doped with Ga and In: Determination of Their Composition through X-Ray Spectroscopy and Inductively Coupled Plasma Mass Spectrometry

An approach is proposed to study the composition of synthesized thin zinc films doped with In and Ga through local X-ray spectral analysis (LXSA) and inductively coupled plasma mass spectrometry (ICP-MS). A relationship between the amount/distribution of additives in the sample and synthesis conditions on rotating substrates is found. The results of determining the dominant impurities in film solutions with ICP-MS are used to validate those obtained with the LXSA method without sample preparation. To find doping impurities at an amount less than 1 at % is possible only through the ICP-MS method.

Validating a Single-Particle ICP-MS Method to Measure Nanoparticles in Human Whole Blood for Nanotoxicology

ABSTRACTWith the rising use of nanomaterials in everyday objects, an uptake of those materials by humans is very likely. To assess their effect on the body, reliable detection of nanoparticles even in very low amounts in human blood becomes increasingly important. Single-particle (SP) inductively coupled plasma–mass spectrometry (ICP-MS) is a fast and reliable method for counting and sizing particles at lowest concentrations, while simultaneously distinguishing between dissolved and particulate analytes. For the first time to our knowledge, a dedicated method validation approach for silver and gold nanoparticle analysis in human whole blood has been performed. With only little sample preparation, trueness expressed as bias with values below or equal to 5% and imprecision values below 6% for particle size as well as an effective limit of detection of around 20 nm are possible. The concentration working range throughout all measured samples was in the nanogram per liter range, making SP-ICP-MS a powerful tool in future nanotoxicological applications and trace analysis of nanoparticles.

Quantification of impurities in carbon nanotubes: Development of ICP-MS sample preparation methods

Carbon nanotubes (CNTs) are one of the prospective nanomaterials to be used in consumer products. Commercially available carbon nanotubes contain significant amounts of metal impurities which are added during synthesis as a catalyst. The presence of metal impurities in CNTs influences the physicochemical properties of materials and its applications. The quantification of metal impurities in CNTs is essential to conduct environmental and health risk assessments. This study aims to develop a method which can be used effectively in laboratories to quantify multi-element impurities in CNTs using Inductively Coupled Plasma-Mass Spectrometry (ICP-MS). Prior to the analysis, samples were prepared by conventional microwave acid digestion (CMAD) and microwave oxygen combustion (MOC). In addition, the ICP-MS method was validated by determining multiple analytical figures of merit such as linear calibration range, system suitability, method detection limit (MDL), limit of quantitation (LOQ), and accuracy. The developed CMAD and MOC methods were suitable to digest metal impurities in carbon nanotubes and the ICP-MS results were in good agreement (80–110% of recovery) with the certified values. In comparison of two methods, CMAD is a simple and straightforward two-step procedure with safe experimental conditions, and requires only 5 mg of sample. Moreover, CMAD overcomes the disadvantage of the pre-existing CNT digestion methods such as the requirement of multi-step acid digestion and drying processes.

A candidate reference method for serum potassium measurement by inductively coupled plasma mass spectrometry.

Potassium is an important serum ion that is frequently assayed in clinical laboratories. Quality assurance requires reference methods; thus, the establishment of a candidate reference method for serum potassium measurements is important. An inductively coupled plasma mass spectrometry (ICP-MS) method was developed. Serum samples were gravimetrically spiked with an aluminum internal standard, digested with 69% ultrapure nitric acid, and diluted to the required concentration. The 39K/27Al ratios were measured by ICP-MS in hydrogen mode. The method was calibrated using 5% nitric acid matrix calibrators, and the calibration function was established using the bracketing method. The correlation coefficients between the measured 39K/27Al ratios and the analyte concentration ratios were >0.9999. The coefficients of variation were 0.40%, 0.68%, and 0.22% for the three serum samples, and the analytical recovery was 99.8%. The accuracy of the measurement was also verified by measuring certified reference materials, SRM909b and SRM956b. Comparison with the ion selective electrode routine method and international inter-laboratory comparisons gave satisfied results. The new ICP-MS method is specific, precise, simple, and low-cost, and it may be used as a candidate reference method for standardizing serum potassium measurements.

Urinary iodine: comparison of a simple method for its determination in microplates with measurement by inductively-coupled plasma mass spectrometry

The aim of our study was to develop and validate an inexpensive, rapid, easy to use quantitative method to determine urinary iodine without major procurement costs for equipment. The rationale behind introducing this method is the increasing demand for urinary iodine assessments. Our study included 103 patients (76 female, 27 male), age (arithmetic mean) 52 ± 17.3 years. Urinary iodine was determined in microplates by a modification of the Sandell-Kolthoff reaction. The results were compared with inductively-coupled plasma mass spectrometry (ICP-MS) for iodine, considered as reference method. Geometric mean of urinary iodine determined by the Sandell-Kolthoff reaction method was 62.69 μg/l (95% confidence interval 53.16–73.92) whereas by the ICP-MS method it was 65.53 μg/l (95% confidence interval 54.77–78.41). Passing-Bablok regression equations for both methods gave y = 3.374 + 0.873x (y: Sandell-Kolthoff method, x: ICP-MS). Spearman´s correlation coefficient was 0.981, indicating a very high degree of agreement between the two methods. Bland-Altman plots showed no significant systematic difference between the two methods. The modified Sandell-Kolthoff method using microtiter plate technique presented here is a simple, inexpensive semi-automated method to determine urinary iodine with very little toxic waste. Comparison with the ICP-MS-technique yielded a good agreement between the two methods.

Iodine in food- and dietary supplement–composition databases

The US Food and Drug Administration (FDA) and the Nutrient Data Laboratory (NDL) of the USDA Agricultural Research Service have worked independently on determining the iodine content of foods and dietary supplements and are now harmonizing their efforts. The objective of the current article is to describe the harmonization plan and the results of initial iodine analyses accomplished under that plan. For many years, the FDA’s Total Diet Study (TDS) has measured iodine concentrations in selected foods collected in 4 regions of the country each year. For more than a decade, the NDL has collected and analyzed foods as part of the National Food and Nutrient Analysis Program; iodine analysis is now being added to the program. The NDL recently qualified a commercial laboratory to conduct iodine analysis of foods by an inductively coupled plasma mass spectrometry (ICP-MS) method. Co-analysis of a set of samples by the commercial laboratory using the ICP-MS method and by the FDA laboratory using its standard colorimetric method yielded comparable results. The FDA recently reviewed historical TDS data for trends in the iodine content of selected foods, and the NDL analyzed samples of a limited subset of those foods for iodine. The FDA and the NDL are working to combine their data on iodine in foods and to produce an online database that can be used for estimating iodine intake from foods in the US population. In addition, the NDL continues to analyze dietary supplements for iodine and, in collaboration with the NIH Office of Dietary Supplements, to publish the data online in the Dietary Supplement Ingredient Database. The goal is to provide, through these 2 harmonized databases and the continuing TDS focus on iodine, improved tools for estimating iodine intake in population studies.