Speciation of manganese binding to biomolecules in pine nuts (Pinus pinea) by two-dimensional liquid chromatography coupled to ultraviolet and inductively coupled plasma mass spectrometry detectors followed by identification by electrospray ionization mass spectrometry

Advances in analytical methodology for speciation of manganese in pine nuts are presented in this work. The approach is based on the use of orthogonal chromatographic systems, namely size-exclusion chromatography (SEC) of the extracts and strong anion exchange (IEC) of the fractions collected by the first column. In both columns, manganese elution is first monitored by a quadrupole inductively coupled plasma mass spectrometry (ICP-MS) instrument equipped with an octopole reaction cell and an ultraviolet (UV) detector. SEC is performed by using two columns covering the molecular weight range from <10 to 70 kDa that allows an initial screening of the molecular weight of the Mn species. The higher resolution capability of the low molecular weight range column is the reason to use the latter for further experiments. The fraction from SEC-ICP-MS in which Mn is present at highest concentration is submitted to IEC-ICP-MS allowing Mn-citrate and MnCl(2) identification by retention time matching with standards. The concentration of these species is estimated to be 75 and 125 microg kg(-1) (as Mn), respectively, in the pine nuts samples and the presence of Mn-citrate is confirmed by nanoelectrospray ionization quadrupole time-of-flight mass spectrometry (nESI-QqTOF-MS). In the same fraction, a third Mn-containing peak is detected in the IEC-UV-ICP-MS chromatogram. This peak corresponds to a protein containing Mn that was later submitted to a tryptic digestion and analyzed by nESI-QqTOF. The MS/MS data of a doubly charged peptide are used to obtain the sequence of the protein with the Mascot search engine. The peak turned out to be isocitrate dehydrogenase, a protein commonly associated with Mn. Copyright (c) 2008 John Wiley & Sons, Ltd.     

Fractionation of soluble selenium compounds from fish using size-exclusion chromatography with on-line detection by inductively coupled plasma mass spectrometry

Fish accumulate significant amounts of selenium and are an important dietary source of this element. Some studies have however indicated a low bioavailability of the selenium from fish. Since little is known of the selenium forms in fish, we have studied soluble selenium compounds in fish species, and compared different techniques for fractionation of selenocompounds (size-exclusion chromatography, ultrafiltration, and precipitation with trichloroacetic acid). The size-exclusion column (Superdex 200 HR 10/30) was coupled on-line to inductively coupled plasma mass spectrometry (ICP-MS). The limit of detection was 0.20 microgram l-1 and the selenium response was linear in the investigated concentration range of 0-20 micrograms l-1 (r2 = 0.98). For plaice 47% of the selenium was extractable while the extraction efficiency for cod was 23%. The fish extracts were injected onto the column four times each and the variation in the quantitative data for different selenium-containing fractions between the runs was small (RSD < 10%). The recovery of selenium in the chromatographic step was about 70%, indicating some interaction between the fish extracts and the column material. Ultrafiltration using a membrane with a cut-off at M(r) 10,000 gave results similar to the size-exclusion fractionation, for cod about 20% of the soluble selenium had a M(r) < 10,000 and the corresponding value for plaice was 69%. Removal of high-molecular-weight compounds from the sample by trichloroacetic acid precipitation showed a similar proportion of low-molecular-weight compounds for plaice (77%), while the obtained value for cod was higher (38%) compared with the other techniques.     

Multielemental analyses of tree rings by inductively coupled plasma mass spectrometry

Inductively coupled plasma mass spectrometry (ICP-MS) was evaluated for major, minor, trace, and ultra-trace elemental analyses of individual tree rings. The samples were obtained from an old-growth Douglas fir (Pseudotsuga menziesii) growing 15 km northeast of Mount St. Helens volcano, Washington, USA and from trees at various other North American sites. Samples were brought into solution by microwave digestion in sealed Teflon vessels. Eightly percent of elements from Li to U had detection limits in the solid (wood) below 8.0 ng g^–1 (parts per billion, ppb). When selected element concentrations in the Mount St. Helens samples are plotted against time, two anomalous peaks occur at A. D. 1478 and 1490 that closely correlate with past eruptions of the volcano. These preliminary results show that ICP-MS is a rapid and sensitive analytical method for multielemental analyses of individual tree rings.     

Multielemental characterization of honey using inductively coupled plasma mass spectrometry fused with chemometrics

Honey is considered a desirable ingredient in a range of different foodstuffs because of its nutrient and therapeutic effect. The honey characteristics mainly depend on the type of vegetation visited by the bees and the climatic conditions in which the plants are growing. Therefore, the purity, floral and geographical origin and authenticity are important factors influencing the overall perception of honey and honey‐based products in terms of quality and price. An important parameter in this picture is the elemental composition of honey because it can be linked with the floral type of honey, floral plant density and the botanical origin of nectar and pollens. In this work, the concentration range variation of 18 elements (Al, As, Ba, Ca, Cd, Co, Cr, Cu, Mg, Mn, Na, Ni, K, Pb, Sr, Ti, V and Zn) was investigated in four varieties of honey (linden, acacia, rape, and sunflower) originating from Romania, because the elemental profile of honey may give important information to differentiate its geographical and varietal origin for authenticity purpose. All the determinations were carried out by inductively coupled plasma quadrupole mass spectrometry (ICP‐Q‐MS). The most abundant minerals decreased in the following order: K > Ca > Mg > Na, having the mean values of 248.70, 59.97, 20.54 and 11.92 mg kg^?1, respectively. The mineral content marks the differences in honey samples from different botanical origin and can be used as a tool for authentication purposes and also extends its applicability to assess the traceability of honey. Analysis of variance showed the preliminary relationships between the elements and samples. Further, the discrimination between different studied honey samples was achieved by principal component analysis (PCA). The multivariate analysis of the data allowed us to separate the honey samples into distinct groups according to their macroelement and microelement composition, emphasizing the origin of variation of element concentrations by honey type. Therefore, this approach might be potentially useful for the control of honey quality, origin or authenticity, and even to use the honey as environmental tracer.     

Multielemental trace analysis of biological materials using double focusing inductively coupled plasma mass spectrometry detection

The analytical potential of double focusing-inductively coupled plasma-mass spectrometry (DF-ICP-MS) for total elemental analysis in clinical samples (serum, blood, urine and other biological fluids), tissues and food products is illustrated by reviewing typical applications recently published. Also, the use of DF-ICP-MS as specific detector for trace element speciation in biological samples is discussed. After adequate separation of interferences in the chromatographic column, low resolution measurements (R = 300) can be used to provide enhanced sensitivities of more than 100 times compared with quadrupole-inductively coupled plasma-mass spectrometry (Q-ICP-MS). This capability is extremely valuable in speciation studies. Also, the use of DF-ICP-MS at low resolution could provide very precise isotope ratio measurements for isotope dilution analysis due to the ‘flat topped’ peaks obtained at this resolution. Unfortunately, the literature on these last two issues is rather scarce so far, in spite of their extremely high analytical possibilities for biological research. Moreover, the bright future of DF-ICP-MS as a most powerful multielemental detector for trace element applications in biological systems will be highlighted. Apart from applications detailed above other important application fields can be envisaged. In particular, we will speculate on its possible use to confirm/establish ‘reference values’ of trace element content in ‘normal’ populations and so to help to diagnose health and disease status, related with trace element total content or their speciation in clinical specimens.     

Elemental fractionation in laser ablation inductively coupled plasma mass spectrometry

The major challenge to the use of laser ablation sample introduction, combined with inductively coupled plasma mass spectrometry, is the problem of calibration. In the geological analysis of minerals, calibration is complicated by the extraordinarily wide variety of sample matrices which may be encountered. While there is a lack of mineral standards with well characterized concentrations near 1 g/g, the NIST glass reference materials (SRM 610–617) have been demonstrated to be very useful for the analysis of a wide variety of lithophile elements in silicate samples. An internal reference element, for which the concentration is known in the sample, has been widely used to make corrections for the multiplicative effects of volume (or weight) of the sample ablated, instrument drift, and matrix effects. This procedure works extremely well where elements being determined and the internal reference element being used share similar ablation behaviours; i.e., they do not fractionate progressively during the ablation and transport process. In this study, it is demonstrated that, in terms of ablation behaviour, elements fall into several distinct clusters and that the elements within these clusters correlate well with each other during a period of ablation. Thus, elements within a cluster can be determined using an internal reference element from within the same cluster. While a combination of periodic varying properties typifies the clusters, the geochemical classification of elements into lithophile (silicate loving), and chalcophile (sulphide loving) appears to offer the best characterization of the major groups.     

Elemental fractionation in laser ablation inductively coupled plasma mass spectrometry

The major challenge to the use of laser ablation sample introduction, combined with inductively coupled plasma mass spectrometry, is the problem of calibration. In the geological analysis of minerals, calibration is complicated by the extraordinarily wide variety of sample matrices which may be encountered. While there is a lack of mineral standards with well characterized concentrations near 1 microg/g, the NIST glass reference materials (SRM 610-617) have been demonstrated to be very useful for the analysis of a wide variety of lithophile elements in silicate samples. An internal reference element, for which the concentration is known in the sample, has been widely used to make corrections for the multiplicative effects of volume (or weight) of the sample ablated, instrument drift, and matrix effects. This procedure works extremely well where elements being determined and the internal reference element being used share similar ablation behaviours; i.e., they do not fractionate progressively during the ablation and transport process. In this study, it is demonstrated that, in terms of ablation behaviour, elements fall into several distinct clusters and that the elements within these clusters correlate well with each other during a period of ablation. Thus, elements within a cluster can be determined using an internal reference element from within the same cluster. While a combination of periodic varying properties typifies the clusters, the geochemical classification of elements into lithophile (silicate loving), and chalcophile (sulphide loving) appears to offer the best characterization of the major groups.     

Multielemental speciation of trace elements in estuarine waters with automated on-site UV photolysis and resin chelation coupled to inductively coupled plasma mass spectrometry

An integrated approach for the accurate determination of total, labile and organically bound dissolved trace metal concentration in the field is presented. Two independent automated platforms consisting of an ultraviolet (UV) on-line unit and a chelation/preconcentration/matrix elimination module were specifically developed to process samples on-site to avoid sample storage prior to inductively coupled plasma mass spectrometry (ICP-MS) analysis. The speciation scheme allowed simultaneous discrimination between labile and organic stable dissolved species of seven trace elements including Cd, Cu, Mn, Ni, Pb, U and Zn, using only 5 ml of sample with detection limits ranging between 0.6 ng l⁻¹ for Cd and 33 ng l⁻¹ for Ni. The influence of UV photolysis on organic matter and its associated metal complexes was investigated by fluorescence spectroscopy and validated against natural samples spiked with humic substances standards. The chelation/preconcentration/matrix elimination procedure was validated against an artificial seawater spiked sample and two certified reference materials (SLRS-4 and CASS-4) to ensure homogenous performance across freshwater, estuarine and seawater samples. The speciation scheme was applied to two natural freshwater and seawater samples collected in the Adour Estuary (Southwestern, France) and processed in the field. The results indicated that the organic complexation levels were high and unchanged for Cu in both samples, whereas different signatures were observed for Cd, Mn, Ni, Pb, U and Zn, suggesting organic ligands of different origin and/or their transformation/alteration along estuarine water mixing.     

Multielemental analysis in small amounts of environmental reference materials with inductively coupled plasma mass spectrometry

The lowest possible sample weight for performing multielemental trace element analysis on environmental and biological samples by ICP-MS has been investigated. The certified reference materials Bovine Liver NIST SRM 1577b, Human Hair NCS DC 73347 and Oriental Tobacco Leaves CTA-OTL-1 were applied at sample weights (1, 5, 20 and 50 mg aliquots, n = 10) which were significantly lower than those recommended with most recoveries in the range of 95-110%. Samples were digested in a mixture of nitric acid, hydrogen peroxide and hydrogen fluoride by closed-vessel microwave digestion. Multielemental analysis was performed with an optimized ICP-QMS method. Aqueous standard solutions were applied for external calibration with rhodium as the internal standard element. The detection limits varied between 0.02-0.38 microg/g for Li, Na, Cr, Mn, Ni, Cu, Zn, Sr, Cd, Ba and Pb, and up to 1.92 microg/g for Mg, Al, Ca, Fe and Ni. Digested human plasma samples were spiked with multielemental solution (0.5-10 microg/L) to test the analytical method and the recoveries were 95-105% for most analytes. Our results show that in the case of homogeneous SRMs it is possible to use them in very low amounts (1-5 mg) for method development and quality control.     

Multielemental analysis in small amounts of environmental reference materials with inductively coupled plasma mass spectrometry

The lowest possible sample weight for performing multielemental trace element analysis on environmental and biological samples by ICP-MS has been investigated. The certified reference materials Bovine Liver NIST SRM 1577b, Human Hair NCS DC 73347 and Oriental Tobacco Leaves CTA-OTL-1 were applied at sample weights (1, 5, 20 and 50 mg aliquots, n = 10) which were significantly lower than those recommended with most recoveries in the range of 95–110%. Samples were digested in a mixture of nitric acid, hydrogen peroxide and hydrogen fluoride by closed-vessel microwave digestion. Multielemental analysis was performed with an optimized ICP-QMS method. Aqueous standard solutions were applied for external calibration with rhodium as the internal standard element. The detection limits varied between 0.02–¶0.38 μg/g for Li, Na, Cr, Mn, Ni, Cu, Zn, Sr, Cd, Ba and Pb, and up to 1.92 μg/g for Mg, Al, Ca, Fe and Ni. Digested human plasma samples were spiked with multielemental solution (0.5–10 μg/L) to test the analytical method and the recoveries were 95–105% for most analytes. Our results show that in the case of homogeneous SRMs it is possible to use them in very low amounts (1–5 mg) for method development and quality control.     

Elemental speciation by chromatographic separation with inductively coupled plasma mass spectrometry detection

Separation techniques coupled to inductively coupled plasma mass spectrometry (ICP-MS) is reviewed. ICP-MS technique is described briefly. Coupling of the different separation techniques are described, together with the most common applications used for each technique that has been described in the literature. An overview for the future of separation techniques coupled to ICP-MS with regard to elemental speciation is discussed.     

Neptunium determination by inductively coupled plasma mass spectrometry (ICP-MS)

The determination of neptunium-237 (²³⁷Np) traditionally has been performed by alpha spectrometry or neutron activation analysis. These methods are labor intensive and require several days for completion. Inductively Coupled Plasma Mass Spectrometry (ICP-MS) is a possible alternative for²³⁷Np determinations. This paper describes the analytical method developed for samples that have significant levels of uranium present. The lower reporting limits achievable by ICP-MS are competitive with the counting methods, but the real advantage for this laboratory lies in the lower cost and faster turnaround time provided by ICP-MS.     

Arsenic speciation by coupling high-performance liquid chromatography with inductively coupled plasma mass spectrometry

Summary An ICP-MS detector in combination with HPLC has been evaluated for the analysis of six arsenic compounds. The influence of the presence of an organic modifier in the mobile phase on arsenic response and the quality parameters of the analysis are discussed. Detection limits for arsenic species under study range from 10 to 30 pg. The determination of arsenic compounds in solutions simulating fish or sediment extracts has been used to demonstrate the applicability of this technique.     

Determination of arsenic species by inductively coupled plasma mass spectrometry with ion chromatography

Five arsenic species, trimethylarsine oxide, dimethylarsenic acid, monomethylarsonic acid, arsenobetaine and sodium arsenite, in urine were analysed by inductively coupled plasma mass spectrometry with ion chromatography (IC ICP MS). Since the toxicities of different arsenic compounds are different, speciation of arsenic compounds is very important in the investigation of metabolisms. In this paper, we applied ion chromatography (IC) as a separation device and inductively coupled plasma mass spectrometry (ICP MS) as a detection device. For separation of the five arsenic compounds, an anion-exchange column and, as mobile phase, tartaric acid were used. The eluent from the IC column was introduced directly into the nebulizer of the ICP MS and analysed at 75 amu. Detection limits were from 4 to 9 pg as arsenic.     

Estimation of detection limits in inductively coupled plasma mass spectrometry

The theoretical estimation of the detection limits in inductively coupled plasma mass spectrometry has been investigated. This calculation includes significant parameters of the ICP source and mass spectrometer. The calculated values show generally good agreement with experimental results. The development of a mathematical relationship may be useful for evaluation of instrumental parameters and sample introduction techniques. Received: 30 January 1998 / Revised: 9 June 1998 / Accepted: 16 June 1998     

Estimation of detection limits in inductively coupled plasma mass spectrometry

The theoretical estimation of the detection limits in inductively coupled plasma mass spectrometry has been investigated. This calculation includes significant parameters of the ICP source and mass spectrometer. The calculated values show generally good agreement with experimental results. The development of a mathematical relationship may be useful for evaluation of instrumental parameters and sample introduction techniques.     

Element-tagged immunoassay with inductively coupled plasma mass spectrometry for multianalyte detection

The multianalyte immunoassay approach is currently attracting increasing attention due to its high sample throughput, short assay time, low sample consumption and reduced overall cost per assay. This paper reviews progress in the field of multianalyte immunoassays using inductively coupled plasma mass spectrometry, as well as applications of this approach in different fields. Examples related to the combination of protein microarray technology with the multitag approach of the immunoassay ICP-MS method and to the use of ICP-MS in the field of imaging are described. A novel strategy that involves tagging antibodies for ICP-MS detection in sensitive multitag bioassays is also presented. Finally, the outlook for this promising technique is discussed.     

Separation of metalloporphyrins by capillary electrophoresis with UV detection and inductively coupled plasma mass spectrometric detection

Vitamin B12, cobalt protoporphyrin, manganese protoporphyrin, and zinc protoporphyrin were separated using capillary electrophoresis, and a comparison was made between detection with inductively coupled plasma mass spectrometry (ICP-MS) and UV detection. Absolute limits of detection were slightly better with ICP-MS detection than with UV detection, but for both methods absolute detection limits were in the picogram range. The migration times of the analytes decreased by several minutes when ICP MS detection was employed, and this phenomenon was believed to be a result of a "suction effect" that developed when the CE capillary was interfaced to the ICP-MS nebulizer. However, the resolution between species containing the same metal atom was not altered significantly, and the separation was completed in much less time relative to separations performed with UV detection.     

Arsenic speciation by ion chromatography with inductively coupled plasma mass spectrometric detection.

Four As compounds were successfully separated and detected by single-column ion chromatography with inductively coupled plasma (ICP) mass spectrometric detection. The mass spectral interferent ArCl+ was reduced by chromatographically resolving chloride from the negatively charged arsenic species. Determination of four As species was investigated in urine, club soda and wine. Detection limits of 0.16 ng of As(III), 0.26 ng of As(v), 0.073 ng of dimethylarsinic acid (DMA) and 0.18 ng of methylarsonic acid (MMA) in wine were obtained. Sensitivity was further improved by using an He-Ar mixed gas ICP as the ionization source. However, the intensity of the ArCl+ interference was also increased using this plasma. Detection limits of 0.063 ng of As(III), 0.037 ng of As(v), 0.032 ng of DMA and 0.080 ng of MMA in club soda were achieved using the He-Ar plasma source. Similar limits of detection were found in urine and wine.     

Gas chromatography with inductively coupled plasma mass spectrometric detection in speciation analysis

The state-of-the-art of gas chromatography coupled with inductively coupled plasma mass spectrometry (GC-ICP MS) is comprehensively reviewed. Particular attention is given to the recent advances in ICP MS detection including: GC-ICP interface designs; low power plasmas; and alternative mass analyzers (time-of-flight, double-focussing single collector, double-focussing and collision cell single-focussing multicollectors). On the level of sample preparation for speciation analysis by GC-ICP MS, new derivatization reagents and advances in extraction techniques, such as capillary purge-and-trap, solid phase microextraction and stirbar solid phase extraction are discussed. The increasing role of organometallic species labeled with stable isotopes for the detection of sources of errors during sample preparation and for isotope dilution quantification is highlighted. Applications of GC-ICP MS to the analysis of real-world samples are summarized with a focus on the areas which particularly benefit from the high ICP MS detection sensitivity and tolerance to sample matrix.