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.

Whole blood selenium determination by inductively coupled plasma mass spectrometry.

OBJECTIVE: To develop a sensitive method for accurately measuring whole blood selenium and determining an appropriate reference interval for the local Cleveland population. DESIGN AND METHODS: The assay was developed and validated on an inductively coupled plasma mass spectrometry (ICP-MS) with a collision cell. Whole blood trace element free EDTA tubes were used to collect samples for the reference interval study (n=50). Samples were collected after at least 8h fast from healthy adults (76% females) with ages between 19 and 64yr. Whole blood aliquots (1mL) in acid washed cryogenic vials were stored at -70°C until analysis. RESULTS: The method passed the matrix effect, interference (except for Gd), and carryover tests. The method had a linear range of 0.2-7.1µmol/L with accuracies of 87.1-118.1%. The total assay imprecision (CV) was <2.5% across the concentration levels tested. Comparison to another ICP-MS assay offered by an independent clinical lab yielded a Deming regression with a slope of 0.98, an intercept of 0.1µmol/L, a standard error of estimate of 0.1µmol/L, a correlation coefficient of 0.9846, and an average difference of 0.8%. The whole blood Se reference interval using a transformed parametric method was 2.2-3.5µmol/L. CONCLUSIONS: This whole blood Se ICP-MS methodology is sensitive and acceptable for patient testing.

Determination of Phosphorus and Potassium in Commercial Inorganic Fertilizers by Inductively Coupled Plasma-Optical Emission Spectrometry: Single-Laboratory Validation, First Action 2015.18.

A previously validated method for the determination of both citrate-EDTA-soluble P and K and acid-soluble P and K in commercial inorganic fertilizers by inductively coupled plasma-optical emission spectrometry was submitted to the expert review panel (ERP) for fertilizers for consideration of First Action Official Method(SM) status. The ERP evaluated the single-laboratory validation results and recommended the method for First Action Official Method status and provided recommendations for achieving Final Action. Validation materials ranging from 4.4 to 52.4% P2O5 (1.7-22.7% P) and 3-62% K2O (2.5-51.1% K) were used for the validation. Recoveries from validation materials for citrate-soluble P and K ranged from 99.3 to 124.9% P and from 98.4 to 100.7% K. Recoveries from validation materials for acid-soluble "total" P and K ranged from 95.53 to 99.40% P and from 98.36 to 107.28% K. Values of r for citrate-soluble P and K, expressed as RSD, ranged from 0.28 to 1.30% for P and from 0.41 to 1.52% for K. Values of r for total P and K, expressed as RSD, ranged from 0.71 to 1.13% for P and from 0.39 to 1.18% for K. Based on the validation data, the ERP recommended the method (with alternatives for the citrate-soluble and the acid-soluble extractions) for First Action Official Method status and provided recommendations for achieving Final Action status.

Magnetic effervescent tablet-assisted ionic liquid dispersive liquid-liquid microextraction of selenium for speciation in foods and beverages.

A novel, simple and rapid method based on magnetic effervescent tablet-assisted ionic liquid dispersive liquid-liquid microextraction (MEA-IL-DLLME) followed by graphite furnace atomic absorption spectrometry (GFAAS) determination was established for the speciation of selenium in various food and beverage samples. In the procedure, a special magnetic effervescent tablet containing CO2 sources (sodium carbonate and sodium dihydrogenphosphate), ionic liquids and Fe3O4 magnetic nanoparticles (MNPs) was used to combine extractant dispersion and magnetic recovery procedures into a single step. The parameters influencing the microextraction efficiency, such as pH of the sample solution, volume of ionic liquid, amount of MNPs, concentration of the chelating agent, salt effect and matrix effect were investigated and optimised. Under the optimised conditions, the limits of detection (LODs) for Se(IV) were 0.021 µg l(-)(1) and the linear dynamic range was 0.05-5.0 µg l(-)(1). The relative standard deviation for seven replicate measurements of 1.0 µg l(-)(1) of Se(IV) was 2.9%. The accuracy of the developed method was evaluated by analysis of the standard reference materials (GBW10016 tea, GBW10017 milk powder, GBW10043 Liaoning rice, GBW10046 Henan wheat, GBW10048 celery). The proposed method was successfully applied to food and beverage samples including black tea, milk powder, mushroom, soybean, bamboo shoots, energy drink, bottled water, carbonated drink and mineral water for the speciation of Se(IV) and Se(VI) with satisfactory relative recoveries (92.0-108.1%).

Recognizing and overcoming analytical error in the use of ICP-MS for the determination of cadmium in breakfast cereal and dietary supplements.

The potential effect of spectral interference on the accurate measurement of the cadmium (Cd) mass fraction in fortified breakfast cereal and a variety of dietary supplement materials using inductively coupled plasma quadrupole mass spectrometry was studied. The materials were two new standard reference materials (SRMs)--SRM 3233 Fortified Breakfast Cereal and SRM 3532 Calcium Dietary Supplement--as well as several existing materials--SRM 3258 Bitter Orange Fruit, SRM 3259 Bitter Orange Extract, SRM 3260 Bitter Orange-containing Solid Oral Dosage Form, and SRM 3280 Multivitamin/Multielement Tablets. Samples were prepared for analysis using the method of isotope dilution and measured using various operating and sample introduction configurations including standard mode, collision cell with kinetic energy discrimination mode, and standard mode with sample introduction via a desolvating nebulizer system. Three isotope pairs, (112)Cd/(111)Cd, (113)Cd/(111)Cd, and (114)Cd/(111)Cd, were measured. Cadmium mass fraction results for the unseparated samples of each material, measured using the three instrument configurations and isotope pairs, were compared to the results obtained after the matrix was removed via chemical separation using anion exchange chromatography. In four of the six materials studied, measurements using the standard mode with sample introduction via the desolvating nebulizer gave results for the unseparated samples quantified with the (112)Cd/(111)Cd isotope pair that showed a positive bias relative to the matrix-separated samples, which indicated a persistent inference at m/z112 with this configuration. Use of the standard mode, without the desolvating nebulizer, also gave results that showed a positive bias for the unseparated samples quantified with the (112)Cd/(111)Cd isotope pair in three of the materials studied. Collision cell/kinetic energy discrimination mode, however, was very effective for reducing spectral interference for Cd in all of the materials and isotope pairs studied, except in the multivitamin/multielement matrix (SRM 3280) where the large corrections for known isobaric interferences or unidentified interferences compromised the accuracy. For SRM 3280, matrix separation provided the best method to achieve accurate measurement of Cd.

Low volume microwave digestion and direct determination of selenium in biological samples by hydride generation-atomic fluorescence spectrometry.

A low volume microwave digestion (LVMWD) procedure has been developed to have all forms of selenium (Se) compounds in biological samples decomposed to Se (IV) and allow total Se be directly determined by hydride generation-atomic fluorescence spectrometry (HG-AFS), or voltammetrically. Between 0.3 and 0.4 mL of mixed digestion reagents consisting of concentrated (15.4 M) HNO(3)-(18.5 M) H(2)SO(4) (v:v=10:1) and >5 to <40 mg sample were found ideal systems with an optimized MW digestion program. Total Se in five certified reference materials was accurately determined. The results obtained by the conventional and LVMWD techniques agreed well. By avoiding pre-reduction step, this method, suitable for a wide range of biological samples, fully takes the advantages of HG-AFS or voltammetric techniques for their high sensitivity, high tolerance to matrix-related interference and accessibility in instrumentation. LVMWD not only enhances the sample output by 3 times and reduces the operational cost and acid wastes, but also makes the small sample analysis possible for many environmental and medical related research objectives. The digestion pathways of Se containing organic samples are also discussed based on the experimental results.

Quality specifications for the determination of copper, zinc, and selenium in human serum or plasma: evaluation of an approach based on biological and analytical variation.

BACKGROUND: Trace element external quality assessment schemes monitor laboratory performance and provide a stimulus for improvement in accuracy. However, monitoring of participant performance varies according to the scheme and can lead to conflicting conclusions. METHODS: Quality specifications based on biological intra- and interindividual variability were calculated and compared to those currently used by various trace element external quality assessment schemes for plasma or serum copper, zinc, and selenium concentrations. For this purpose, we evaluated results reported by participating laboratories in different schemes, at key concentrations, using z scores. RESULTS: Minimal quality specifications developed from the biological intra- and interindividual variability were, for Cu, +/-0.84 micromol/L or 12% of the assigned target concentration, whichever is greater; for Zn, +/-1.20 micromol/L or 15% of the assigned target concentration, whichever is greater; and for Se, +/-0.072 micromol/L or 12% of the assigned target concentration, whichever is greater. Reported performance of the participating laboratories depended on analyte, concentration, and the selected quality specification. In addition, the most commonly used methods for the determination of Cu, Zn, and Se may give different results. CONCLUSIONS: The proposed minimal quality specifications based on biological variation are generally slightly less stringent than those currently in use, although they do not drastically change the performance evaluation in the different schemes. These specifications are a first step in the harmonization of practices among the schemes and remain to be evaluated.

The use of microemulsion for determination of sodium and potassium in biodiesel by flame atomic absorption spectrometry.

A new method for F AAS determination of sodium and potassium in biodiesel using water-in-oil microemulsion as sample preparation is proposed. The method was investigated for biodiesel produced from different sources, as soybean, castor and sunflower oil and animal fat and was also applied for vegetable oils. The optimized condition for microemulsion formation was 57.6% (w/w) of n-pentanol, 20% (w/w) of biodiesel or vegetable oil, 14.4% (w/w) of Triton X-100 and 8% (w/w) of water (aqueous standard of KCl or NaCl in/or diluted HNO(3)). The optimized instrumental parameters were: aspiration rate of 2 mL min(-1) and the flame composition of 0.131 of C(2)H(2)/air ratio. For comparison purpose, the determination of sodium and potassium were also carried out according to European norms (EN 14108 and EN 14109, respectively). These norms are applied for determination of sodium and potassium in fatty acid methylic ester samples and consist in the sample dilution using organic solvent and determination by F AAS. The stability of microemulsified aqueous standards and samples was investigated and it was found to be stable for at least 3 days while the organic standard diluted with xylene showed a decrease around of 15% in the analytical signal in 1h. The limits of detection were 0.1 microg g(-1) and 0.06 microg g(-1) and the obtained characteristic concentrations were 25 microg L(-1) and 28 microg L(-1) for sodium and potassium, respectively. The proposed method presented two times better limits of detection and better precision (0.4-1.0%) when compared with the dilution technique (1.5-4.5%). The accuracy of the method was evaluated through recovery tests and comparison with the results obtained by dilution technique. The recoveries ranged from 95% to 115% for biodiesel and 90% to 115% for vegetable oil samples. Comparison between the results obtained for biodiesel by both methods showed no significant differences at the 95% confidence level according to a Student's t-test. This study shows that the proposed method based on microemulsion as sample preparation can be applied as an efficient alternative for sodium and potassium determination in biodiesel samples.

Validation of method for total selenium determination in yeast by flame atomic absorption spectrometry.

A procedure using open digestion followed by flame atomic absorption spectrometry is described for measuring the total selenium content of Se-enriched yeast. The limits of detection and quantitation were 2.5 mg/L and 5 mg/L Se, respectively. The signal response was linear over the range of 5-50 mg/L Se, and the average recovery from spiked samples was 98.9%. The validated method was used to measure the Se content of Se-enriched yeast reference material and produced a result of 2145 +/- 38 mg/kg (n = 3), which is in good agreement with the certified level of 2125 +/- 65 mg/kg.

Determination of selenium in marine biological tissues by transverse heated electrothermal atomic absorption spectrometry with longitudinal Zeeman background correction and automated ultrasonic slurry sampling.

A fast, sensitive, and reliable method for determination of selenium in marine biological tissues by electrothermal atomic absorption spectrometry with slurry sampling was developed. Slurries were prepared from fresh and frozen seafood samples that were previously homogenized, dried, and ground; particle sizes <100 microm were taken for analysis. A 3% (v/v) HNO3 solution containing 0.01% (v/v) Triton X-100 was used as slurry diluent. Slurries were mixed on an automated ultrasonic slurry sampler at 20% amplitude for 30 s just before an aliquot was injected into the furnace. The method was successfully validated against the following certified reference materials: NRCC CRM DORM-2 (Dogfish muscle); NRCC CRM TORT-2 (Lobster hepatopancreas); NRCC CRM DOLT-2 (Dogfish liver); and BCR CRM 278 (Mussel tissue), and was subsequently applied to determination of Se in 10 marine biological samples. The influences of the drying procedure (oven-, microwave-, and freeze-drying), matrix modifier amount, mass of solid material in cup, and pipetting sequence are discussed. The limit of determination of Se was 0.16 microg/g and the repeatability, estimated as between-batch precision, was in the range of 4-8%. Se contents in the samples ranged from 0.6 to 2.8 microg/g. The proposed method should be useful for fast assessment of the daily dietary intake of Se.

The determination of phosphorus in Haemophilus influenzae type b conjugate vaccines by inductively coupled plasma-atomic emission spectrometry.

This study describes a method for the determination of phosphorus in lyophilized Haemophilus influenzae type b conjugate vaccines by inductively coupled plasma-atomic emission spectroscopy (ICP-AES). The concentration of polysaccharide is directly related to the concentration of phosphorus as measured in the laboratory. Phosphorus is present in the polyribosyl-ribitol phosphate (PRP) group of the Haemophilus influenzae type b conjugate vaccine. The repeating unit of PRP is 3-B-D ribose[1-1]ribitol-5-phosphate. Phosphorus in the final container is measured in microg per dose. The amount of PRP is calculated from this and reported in microg per dose. The Haemophilus influenzae type b conjugate vaccine was analyzed for phosphorus content within the range of 1.34 to 2.02 microg phosphorus per ml. The relative difference of phosphorus concentrations determined by the ICP-AES method from the phosphorus concentrations determined by the traditional colorimetric molybdate method ranged from 2.2 to 10.6%. Phosphorus spike recovery for the vaccine ranged from 93 to 99% (1.93+/-0.13 microg P/ml). The phosphorus determination of NIST SRM 3139 phosphorus spectrometric solution differed by 3.0% from the certified phosphorus value (10.00 mg P/ml).

Determination of selenium in meat products by hydride generation atomic absorption spectrophotometry.

Wet digestion using a mixture of nitric, sulfuric, and perchloric acids and an aluminum block digester effectively and rapidly decomposed meat samples for selenium determination by hydride generation atomic absorption spectrophotometry. Digestion did not require constant attention by an operator. Selenium recoveries (range, 94-105%) from National Institute of Standards and Technology standard reference materials and spiked samples were used to validate method accuracy. Coefficients of variation (CVs) of repeatability of in-house reference materials used for precision study were 6.4 and 5.6%, respectively, for seafood mix and mutton liver. Selenium levels in meat products from Brisbane markets varied widely: 0.042-0.142, 0.081-0.42, and 0.050-0.198 microgram/g (wet weight) respectively, for beef, chicken, and pork. Overall, selenium levels in manufactured meat ranged from 0.041 to 0.189 microgram/g. The levels of selenium found in this study were generally lower than those reported in Finland but comparable with those reported in some parts of the United States.

Studies on some trace and minor elements in blood. A survey of the Kalpakkam (India) population. Part I: Standardization of analytical methods using ICP-MS and AAS.

Blood is one of the widely used specimens for biological trace element research because of its biological significance and ease of sampling. We have conducted a study of the blood of the Kalpakkam township population for trace and minor elements. For this purpose, analytical methods have been developed and standardized in our laboratory for the elemental analysis of blood plasma and red cells. Inductively coupled plasma-mass spectrometry (ICP-MS), a relatively new technique, has been applied for the analysis of trace elements. Details regarding spectral interference and matrix interference encountered in the analysis of blood and the methods of correcting them have been discussed. Flame atomic absorption spectrometry (AAS)/atomic emission spectrometry (AES) has been applied for the determination of minor elements. Precision and accuracy of these methods have also been discussed.

Quality control procedures for monitoring whole blood and plasma trace metal levels by atomic absorption spectrophotometry.

Well co-ordinated quality control procedures are required to insure that trace metal results determined at ppb (micrograms kg-1 or micrograms l-1) levels by atomic absorption spectrophotometry are reliable. Control materials can be prepared "in-house" provided they are calibrated against standard reference materials (SRM). A mean +/- SD data base should be determined for each quality control material with daily results plotted on Levey-Jennings charts. Westgard's multi-rule quality control scheme is recommended for assessing analytical performance. Additional information may be obtained by using cumulative sum (cusum) charts to detect analytical drift from the mean, and standard deviation index or 'z-score' plot to show analytical bias. Proficiency or quality assurance programs should be used to supplement internal quality verification of analytical performance.