Quadrupole-based Inductively Coupled Plasma Mass Spectrometry Research Articles

Impact of Measurement Protocol on ICP-MS Data Quality Objectives: Part I

Quadrupole-based inductively coupled plasma–mass spectrometry (ICP-MS) is undoubtedly the fastest growing trace element technique today. Since its commercialization in 1983, approximately 20,000 systems have been installed worldwide to carry out a diverse range of applications, including environmental, geological, semiconductor, biomedical, food, pharmaceuticals, cannabis-hemp, petrochemical, and nuclear applications. To meet such varied application needs, modern ICP-MS instrumentation has to be very flexible if it is to keep up with the increasing demands of its users. Nowhere is this more important than in the area of peak integration and measurement protocol. The way the analytical signal is managed in ICP-MS has a direct impact on its multielement characteristics, isotopic capability, detection limits, dynamic range, precision, signal stability and sample throughput—the major strengths that attracted the trace element community to the technique almost 40 years ago. This month’s column focuses on the fundamentals of quadrupole-based ICP-MS measurement regimes—in particular, the balance between maximizing productivity and optimizing performance.

Development, validation and application of an inductively coupled plasma – mass spectrometry method to determine cobalt in metal-on-metal prosthesis patients using volumetric absorptive microsampling

Metal-on-metal (MoM) prostheses, in which the bearing surfaces are made of a metal alloy, may release metal ions upon wear and corrosion, potentially inducing both local and systemic toxicity. As the systemic cobalt concentration increases with the degree of implant wear, this concentration needs to be monitored as a means of assessing implant function and the risk of adverse effects. Here, we report on the development, validation and application of a method to quantitatively assess these Co concentrations in whole blood, based on the combination of volumetric absorptive microsampling (VAMS) and inductively coupled plasma - mass spectrometry (ICP-MS). This method could allow patients to collect the required samples at home, as VAMS samples are easy to collect and can be transported to the laboratory via regular mail. The extraction procedure utilized an alkaline extraction mixture with yttrium as internal standard and proved to be independent of the hematocrit and age of the VAMS samples. The Co concentrations in the VAMS extracts were measured using quadrupole-based ICP-MS. The analytical method covers a range of 2–300 μg/L and displays excellent accuracy (bias ≤4%) and imprecision (relative standard deviation ≤ 5% and ≤15% at the lower limit of quantitation (LLOQ)). The method was applied to venous VAMS samples of MoM prosthesis patients (n = 78), yielding promising results. The comparison of these results with those obtained on the corresponding liquid whole blood samples, showed a correlation coefficient of 0.99 and 87% of the data fulfilled the criteria proposed by the Royal College of Pathologists of Australasia (RCPA).

Assessment of Pb contamination of soils, sediments and road dusts of the City of Lagos, Nigeria.

Lead (Pb) is of considerable concern among other heavy metals because of its toxic impact on the environment and human health. The geochemical nature and source-transport-fate of Pb in Nigeria's environmental media are relatively unknown. This study was undertaken to quantify and characterize Pb in soils, sediments and road dusts from Lagos, Nigeria. A total of forty-eight soil samples, seventeen sediment samples and thirteen roadside soils were collected from within Lagos metropolis. The samples were air-dried, screened, pulverized and sieved through 63-µm nylon mesh. Mineralogical constituent of samples were determined using X-ray diffraction. The sieved fractions and pulverized rock samples were digested and analyzed for elemental Pb components using inductively coupled plasma mass spectrometry (ICP-MS). The chemical fractionations of Pb in the samples were determined by sequential analysis. Lead isotope compositions of the samples were determined using quadrupole-based ICP-MS. Lead isotopic ratios and geo-accumulation indexes were used for discriminating and evaluating Pb sources. Quartz, microcline, K-feldspar, plagioclase and kaolinite were the preponderant minerals in powdered rocks, soils and sediments. The concentration (mg/kg) of elemental Pb in sediments and dusts for Lagos was 21-1963; 23-830 and 22-830, respectively. The plots (208Pb/207Pb)/(206Pb/207Pb) revealed that the Pb in the environmental media was derived from anthropogenic sources. The Pb isotopic ratios for soils, sediments and dusts were characterized by lower 208Pb/206Pb ratios, compared to bedrock. The Pb contents are held principally in the organic sulfide and reducible and carbonate phases. The Pb is held in very reactive geochemical phases, and these portend great risk to the environment and public health.

Multi-element analysis of crude oils using ICP-QQQ-MS

Determination of trace element contents in crude oils constitutes a powerful geochemical tool, complementing organic geochemical analyses and allowing a deeper insight into the processes of oil generation, migration and maturation. Inductively coupled plasma mass spectrometry (ICP-MS) has been widely applied to trace element determination in petroleum samples due to its low detection limits and fast multi-element capability. However, quantification of several elements by quadrupole-based ICP-MS is hampered by low sensitivity due to high ionisation energy, severe polyatomic interferences and/or low abundance. In the present contribution an ICP tandem mass spectrometer (ICP-MS/MS), or triple quadrupole ICP-MS (ICP-QQQ-MS) has been used to overcome these limitations. Prior to analysis, samples were subjected to high pressure acid digestion, allowing external calibration by means of aqueous standards. 25 elements, including P, S, the first-row transition metals, As, Se, Re, Pb and U, could be quantified in one measurement. Polyatomic interferences on the lighter elements could be removed by reaction of the target ions with O2 or NH3 in the collision/reaction cell of the ICP-MS/MS. The accuracy of the analytical method was assessed by the analysis of the standard reference materials NIST SRM 1634c (trace elements in fuel oil) and 1084a (wear-metals in lubricating oil). The measurement procedure was applied to the analysis of crude oil samples from the Alpine Foreland Basin of Austria.

Trace element analysis of human urine collected after administration of Gd-based MRI contrast agents: characterizing spectral interferences using inorganic mass spectrometry.

Analysis of human urine is commonly used in biomonitoring studies to assess exposure to essential (e.g., Cu, Zn, Se) and non-essential (Pb, Cd, Pt) trace elements. These data are also used in epidemiological studies to evaluate potential associations between trace element exposure and various health outcomes within a population. Today most trace element analyses are typically performed using quadrupole-based inductively coupled plasma mass spectrometry (Q-ICP-MS). However, there is always the potential for spectral interferences with Q-ICP-MS instrumentation, especially when analyzing human specimens that may contain medications and other exogenous substances. Moreover, such xenobiotics may be unknown to the investigators. In a recent study focusing on environmental exposures and endometriosis: Endometriosis: Natural History, Diagnosis, and Outcomes (ENDO Study), urine specimens (n=619) were collected from participating women upon enrollment into the study or prior to surgery or pelvic magnetic resonance imaging (MRI), and analyzed for 21 trace elements by Q-ICP-MS. Here we report on some anomalous results observed for Se and Pt with elevated concentrations up to several orders of magnitude greater than what might be expected based on established reference intervals. Further investigations using Sector Field (SF-) ICP-MS instrumentation led to identification of doubly charged and polyatomic gadolinium (Gd) species traced to a Gd-based contrast agent that was administered to some subjects just prior to urine collection. Specifically, interferences from Gd2+ and several minor polyatomics were identified as interferences on all of the major isotopes of Se including 74Se, 76Se, 77Se, 78Se, 80Se, and 82Se. While trace amounts of Pt were present in the urine, a number of Gd-containing polyatomic species were also evident as major interferences on all isotopes of Pt (190Pt, 192Pt, 194Pt, 195Pt, 196Pt, and 198Pt), including Gd-chlorides, Gd-argides, and Gd-oxides. These observations underscore the importance of considering potential isobaric interferences when interpreting unusual trace element results for clinical specimens.

Monitoring Mn in whole blood and urine: a comparison between electrothermal atomic absorption and inorganic mass spectrometry

Measurements of Mn in blood and urine are used in biomonitoring studies as biomarkers of exposure. We compared methods for determining Mn, including graphite furnace atomic absorption spectrometry (GFAAS), quadrupole-based inductively coupled plasma mass spectrometry (Q-ICP-MS) (standard and dynamic reaction cell (DRC) mode), and sector field (SF-) ICP-MS. We investigated polyatomic interferences in ICP-MS that can affect Mn measurements in blood and urine matrices, especially at concentrations associated with biomonitoring studies. Method detection limits (3SD) for blood (and urine) Mn were 1.5 (2.1) µg L−1 for GFAAS, 0.6 (0.5) µg L−1 for SF-ICP-MS, 1.0 (0.5) µg L−1 for DRC-ICP-MS and 6.4 (0.6) µg L−1 for Q-ICP-MS operated in standard mode. Method reproducibility for blood (22 µg L−1Mn) and urine matrices (9 µg L−1Mn) was found to be between 3 and 4% RSD for all methods, except for blood Mn by Q-ICP-MS (11% RSD) and urine Mn by GFAAS (7% RSD). Accuracy was assessed using various reference materials. Careful optimization of the DRC mode is required with blood because, in addition to polyatomic interferences, a large amount of Fe causes spectral overlap on Mn. GFAAS, DRC-ICP-MS and SF-ICP-MS methods show good agreement for Mn in urine and blood across the clinical range studied and, when properly optimized, are suitable for monitoring Mn in blood and urine. In contrast, Q-ICP-MS in standard mode exhibits a positive bias of ∼1 µg L−1 in urine and ∼4 µg L−1 in blood with respect to the other three methods investigated. The implications of this work are important when biomonitoring studies are compared and reference ranges are established.

A highly sensitive analytical method for metal-labelled amino acids by HPLC/ICP-MS

A highly sensitive method for the determination of amino acids by inductively coupled plasma mass spectrometry (ICP-MS), after separation by high performance liquid chromatography, was developed. Amino acids in the presence of a 0.1 mol L−1sodium tetraborate solution were derivatized with a six-coordinated complex of ruthenium, bis(2,2′-bipyridine)-4′-methyl-4-carboxybipyridine-ruthenium N-succinimidyl ester-bis(hexafluorophosphate), dissolved in dimethylformamide. The derivatives were stable and were remained associated during separation on an octadecyl reversed phase column with a linear gradient elution using 100 mmol L−1sodium phosphate buffer and acetonitrile. Ten kinds of amino acids derivatized with the reagent were successfully separated from each other. The ruthenium in the derivative was detected by quadrupole-based ICP-MS, and the detection limit for the amino acids (signal-to-noise ratio of 3) was 5 fmol per injection.

Characterization of natural water resources in Israel by inductively coupled plasma mass spectrometry

Analytical procedures are applied for the determination of plutonium, uranium and strontium concentration, their isotope ratios and the analysis of rare earth elements (REE) at trace and ultratrace level in natural Israeli water resources with relatively high matrix content (Na = 20–150 mg L −1, Mg = 20–50 mg L −1 and Ca = 40–100 mg L −1) by inductively coupled plasma mass spectrometry (ICP-MS). To avoid matrix and clogging effects on the cones during mass spectrometric measurements and to analyze Pu and REE at extremely low concentration levels, separation procedures from matrices were applied. An extremely low Pu contamination of the Sea of Galilee was observed due to global nuclear fallout after the nuclear weapons test in the 1960s. The detection limit, for example, for 239Pu was found to be <10 −19 g mL −1. For uranium a natural variation of the 234U/ 238U isotope ratios by a factor of up to 2 in comparison to the IUPAC table value was detected using ICP-MS. This paper discusses the application of double-focusing sector field ICP-MS with single and multiple ion collection as well as quadrupole-based ICP-MS (ICP-QMS) for the quantitative determination of REE, plutonium, uranium and strontium and their isotope ratios after analyte/matrix separation at trace and ultratrace levels in natural water.

Determination of Depleted Uranium in Urine via Isotope Ratio Measurements Using Large-Bore Direct Injection High Efficiency Nebulizer—Inductively Coupled Plasma Mass Spectrometry

Inductively coupled plasma mass spectrometry (ICP-MS), coupled with a large-bore direct injection high efficiency nebulizer (LB-DIHEN), was utilized to determine the concentration and isotopic ratio of uranium in 11 samples of synthetic urine spiked with varying concentrations and ratios of uranium isotopes. Total U concentrations and (235)U/(238)U isotopic ratios ranged from 0.1 to 10 microg/L and 0.0011 and 0.00725, respectively. The results are compared with data from other laboratories that used either alpha-spectrometry or quadrupole-based ICP-MS with a conventional nebulizer-spray chamber arrangement. Severe matrix effects due to the high total dissolved solid content of the samples resulted in a 60 to 80% loss of signal intensity, but were compensated for by using (233)U as an internal standard. Accurate results were obtained with LB-DIHEN-ICP-MS, allowing for the positive identification of depleted uranium based on the (235)U/(238)U ratio. Precision for the (235)U/(238)U ratio is typically better than 5% and 15% for ICP-MS and alpha-spectrometry, respectively, determined over the concentrations and ratios investigated in this study, with the LB-DIHEN-ICP-MS system providing the most accurate results. Short-term precision (6 min) for the individual (235)U and (238)U isotopes in synthetic urine is better than 2% (N = 7), compared to approximately 5% for conventional nebulizer-spray chamber arrangements and >10% for alpha-spectrometry. The significance of these measurements is discussed for uranium exposure assessment of Persian Gulf War veterans affected by depleted uranium ammunitions.

Determination of phosphorus in small amounts of protein samples by ICP–MS

Inductively coupled plasma mass spectrometry (ICP-MS) is used for phosphorus determination in protein samples. A small amount of solid protein sample (down to 1 micro g) or digest (1-10 micro L) protein solution was denatured in nitric acid and hydrogen peroxide by closed-microvessel microwave digestion. Phosphorus determination was performed with an optimized analytical method using a double-focusing sector field inductively coupled plasma mass spectrometer (ICP-SFMS) and quadrupole-based ICP-MS (ICP-QMS). For quality control of phosphorus determination a certified reference material (CRM), single cell proteins (BCR 273) with a high phosphorus content of 26.8+/-0.4 mg g(-1), was analyzed. For studies on phosphorus determination in proteins while reducing the sample amount as low as possible the homogeneity of CRM BCR 273 was investigated. Relative standard deviation and measurement accuracy in ICP-QMS was within 2%, 3.5%, 11% and 12% when using CRM BCR 273 sample weights of 40 mg, 5 mg, 1 mg and 0.3 mg, respectively. The lowest possible sample weight for an accurate phosphorus analysis in protein samples by ICP-MS is discussed. The analytical method developed was applied for the analysis of homogeneous protein samples in very low amounts [1-100 micro g of solid protein sample, e.g. beta-casein or down to 1 micro L of protein or digest in solution (e.g., tau protein)]. A further reduction of the diluted protein solution volume was achieved by the application of flow injection in ICP-SFMS, which is discussed with reference to real protein digests after protein separation using 2D gel electrophoresis.The detection limits for phosphorus in biological samples were determined by ICP-SFMS down to the ng g(-1) level. The present work discusses the figure of merit for the determination of phosphorus in a small amount of protein sample with ICP-SFMS in comparison to ICP-QMS.