Coupled Plasma Mass Spectrometry Detection Research Articles

Covalent organic frameworks based hierarchical porous hybrid monolithic capillary: Synthesis, characterization, and applications in trace metals analysis

The preparation of hierarchical porous monolithic column with high covalent organic frameworks (COF) loading and micropores accessibility is challenging due to the easy aggregability and sedimentation of COFs. Herein, a novel strategy based on high internal phase emulsion (HIPE) polymerization was proposed for preparing COF hybrid capillary monolithic column with hierarchical porosity. COFs with different frameworks including imine COFs (COF-OMe, COF-F and COF-SH), triazine COF (CTF-1) and boron-based COF (COF-5) were selected to investigate the universality of the preparation strategy. The presence of COF in the monolithic capillary was confirmed by scanning electron microscope, X-ray diffraction and fourier transform infrared spectroscopy. Nitrogen adsorption/desorption experiments and thermogravimetric analysis showed that the prepared COF hybrid monolithic capillary exhibited high COF loading (e.g., 28.7% for COF-SH) and accessibility (e.g., 98.5% for COF-SH), mainly due to the thin walls of void-window structures originated from polymerization of HIPE. The successful preparation of water-stable COF-F, COF-OMe, COF-SH and CTF-1 hybrid monolithic columns demonstrated the proposed synthesis strategy is universal to water-stable COF without tedious optimization of dispersion system, effectively avoiding the sedimentation of COF in pre-polymerization solution. Then, the sulfhydryl-modified COF hybrid polymer (poly(COF-SH-HIPE)) monolithic column was evaluated for the extraction of heavy metal ions, and a method based on poly(COF-SH-HIPE) monolithic capillary microextraction on-line coupled with inductively coupled plasma mass spectrometry detection was developed for analysis of trace Cd, Hg and Pb in human fluid samples.

All-in-One Microfluidic Chip for Online Labeling, Separating, and Focusing Rare Circulating Tumor Cells from Blood Samples Followed by Inductively Coupled Plasma Mass Spectrometry Detection.

Circulating tumor cell (CTC) detection is essential for early cancer diagnosis and evaluating treatment efficacy. Despite the growing interest in isolating CTCs and further quantifying surface biomarkers at the single-cell level, highly efficient separation of rare CTCs from massive blood cells is still a big challenge. Here, we developed an all-in-one microfluidic chip system for the immunolabeling, magnetic separation, and focusing of HepG2 cells (as a CTC model) and online combined it with single cell-inductively coupled plasma mass spectrometry (SC-ICP-MS) for quantitative analysis of the asialoglycoprotein receptor (ASGPR) on single HepG2 cells. Lanthanide-labeled anti-ASGPR monoclonal antibody and antiepithelial cell adhesion molecule-modified magnetic beads were prepared as signal and magnetic probes, respectively. Target cells were highly efficiently labeled with signal and magnetic probes in the mixing zone of the microfluidic chip and then focused and sorted in the separation zone by specific magnetic separation techniques to avoid matrix contamination. The average cell recovery of HepG2 cells was derived to be 94.1 ± 5.7% with high separation efficiency and purity. The sorted cells with signal probes were detected for enumeration and quantification of ASGPR on their surface by SC-ICP-MS. The developed method showed good specificity and high sensitivity, detecting an average of (1.0 ± 0.2) × 105 ASGPR molecules per cell surface. This method can be used for absolute quantitative analysis of ASGPR on the surface of single hepatocellular carcinoma cells in real-world samples, providing a highly efficient analytical platform for studying targeted drug delivery in cancer therapy.

Evaluation of Cd2+ stress on Synechocystis sp. PCC6803 based on single-cell elemental accumulation and algal toxicological response

With the development of single cell analysis techniques, the concept of precision toxicology has been proposed in recent years. Due to the heterogeneity of cells, we need to perform toxicological assessments on individual cells. Microalgae, one kind of important primary producers, play as a major pathway by which heavy metals enter the food chain and thus accumulate/transfer to higher trophic levels. Herein, the biosorption of Cd (Ex-Cd) and bioaccumulation of Cd (In-Cd) for Synechocystis sp. PCC 6803 were investigated by online 3D droplet microfluidic device combined with inductively coupled plasma mass spectrometry detection. Meanwhile, the algal toxicological responses of the algae cell to Cd2+ exposure under different concentration (50, 100, and 150 μg L − 1) and time (15 min, 24, 48 and 96 h) were studied. Combining single-cell analysis with toxicological indicators, the toxicity mechanism of Cd2+to algal was discussed. The single cell analysis results revealed heterogeneity in cellular uptake of Cd2+. The proportion of Cd-containing cells and Cd content in single algal cells all reached the maximum at 24 h. The uptake of Cd2+ occurred within 15 min under all tested exposure concentrations and a large part of Cd2+ were adsorbed on the algal cells surface. The Pearson correlation analysis showed that cell density, chlorophyll a and carotenoids were significantly negatively correlated with Cd accumulation, whereas ROS level and SOD activity were significantly positively correlated with Cd accumulation. It suggested that Cd2+accumulated intracellular would show toxic effects on the algal cells and oxidative stress is the main mechanism of Cd toxicity to algal cells. This work promotes our understanding of the toxicological responses of microalgae under Cd stress at single cells level.

Ultrasensitive determination of β-conglutin food allergen by means an aptamer assay based on inductively coupled plasma mass spectrometry detection

The overall objective of this work is the evaluation of different competitive aptamer assays based on inductively coupled plasma mass spectrometry (ICP-MS) detection for the determination of β-conglutin (food protein allergen from lupin) in flour samples. To this end, two competitive aptamer assay schemes were developed using either thiolated aptamers chemisorbed onto gold nanoparticles (AuNPs) or biotinylated aptamers linked to streptavidin-AuNPs. The influence of ICP-MS detection mode (i.e., conventional vs single particle) on assay performance was explored. In the case of the thiolated aptamer, the limit of detection (LoD) obtained using the single particle mode was improved 2-fold as compared to the LoD provided by the conventional mode. With regards to the biotinylated aptamer, the use of the conventional mode provided a 5-fold improvement of LoD as compared to that obtained for the single particle one. Using the optimized conditions, the best LoD of 2 pM was obtained with the biotinylated aptamer operating with conventional ICP-MS detection. When compared to previous reports using the same aptamer in a competitive assay, the developed method significantly improved the LoD by at least an order of magnitude. Different flour samples containing lupin were successfully analyzed according to European Conformity guidelines for the analysis of food contaminants.

Associations of Maternal Urinary Arsenic Concentrations during Pregnancy with Infant and Child Mental, Psychomotor, and Cognitive Development: The HOME Study

Background and aims Arsenic exposure during pregnancy may increase the risk for intellectual deficits in children, but limited data exists from prospective epidemiologic studies, particularly at low arsenic exposure levels. We investigated the association between prenatal urinary arsenic concentrations and childhood cognitive abilities in the Health Outcomes and Measures of the Environment (HOME) Study. Methods We used anion exchange chromatography coupled with inductively coupled plasma mass spectrometry detection to measure arsenic species content in pregnant women’s urine. The summation of inorganic arsenic (iAs), monomethylarsonic acid (MMA), and dimethylarsinic acid (DMA) refers to ∑As. We longitudinally assessed children’s cognitive function (n = 260) longitudinally at 1, 2, and 3 years using Bayley Scales of Infant and Toddler Development, at 5 years using Wechsler Preschool and Primary Scale of Intelligence, and at 8 years using Wechsler Intelligence Scale for Children. Results We observed a modest decrease in mental development index and full-scale intelligence quotient at ages 3 and 5 years with each doubling of ∑As (median and IQR of 3.63 and 2.40-5.86 µg/L) with estimated score (ß) differences and 95% confidence interval (CI) of -1.8 from -4.1 to 0.5 and -2.5 from -5.1 to 0.0, respectively. This trend was stronger among children whose mothers had lower iAs methylation capacity and low urinary arsebonetaine concentrations. Conclusions Our findings suggest that exposure levels relevant to the general US population may adversely affect children’s cognitive abilities. Keywords arsenic; neurodevelopment; cognitive; Bayley Scale of Infant Development; Wechsler Preschool and Primary Scale of Intelligence; in utero exposure; Mental development index; Full scale intelligence quotient.

Associations of maternal urinary arsenic concentrations during pregnancy with childhood cognitive abilities: The HOME study.

Arsenic exposure during pregnancy may increase the risk for intellectual deficits in children, but limited data exist from prospective epidemiologic studies, particularly at low arsenic exposure levels. We investigated the association between prenatal maternal urinary arsenic concentrations and childhood cognitive abilities in the Health Outcomes and Measures of the Environment (HOME) Study. We used anion exchange chromatography coupled with inductively coupled plasma mass spectrometry detection to measure arsenic species content in pregnant women’s urine. The summation of inorganic arsenic (iAs), monomethylarsonic acid (MMA), and dimethylarsinic acid (DMA) refers to . We assessed children’s cognitive function (n = 260) longitudinally at 1-, 2-, and 3-years using Bayley Scales of Infant and Toddler Development, at 5 years using Wechsler Preschool and Primary Scale of Intelligence, and at 8 years using Wechsler Intelligence Scale for Children. We observed a modest decrease in mental development index and full-scale intelligence quotient at ages 3 and 5 years with each doubling of with estimated score (ß) differences and 95% confidence interval (CI) of −1.8 from −4.1 to 0.5 and −2.5 from −5.1 to 0.0, respectively. This trend was stronger and reached statistical significance among children whose mothers had lower iAs methylation capacity and low urinary arsenobetaine concentrations. Our findings suggest that arsenic exposure levels relevant to the general US population may affect children’s cognitive abilities.

Magnetic porous coordination networks for preconcentration of various metal ions from environmental water followed by inductively coupled plasma mass spectrometry detection

Magnetic composites of Fe3O4@SiO2@PCN-224 (MPCN-224) was obtained by one-pot method with the interaction between PCN-224 monomer and silicon layer on magnetic core. MPCN-224 exhibited a core-shell structure with the specific surface area of 1114 m2 g−1 and good adsorption performance for various metal ions. With MPCN-224 used as the sorbent, a method combing magnetic solid phase extraction (MSPE) with inductively coupled plasma mass spectrometry (ICPMS) detection was established for the enrichment and determination of trace Cr(III), Zn(II), Pb(II) and Bi(III) in environmental water samples. Under the optimized conditions, the developed method exhibited low detection limits of 0.94–11.4 ng L−1 and wide linear range for target four metal ions. The analysis speed was fast (2/5 min for adsorption and desorption respectively). The MPCN-224 sorbent could be reused for at least 12 times, and the regeneration can be achieved easily by adjusting solution pH. The sorbent and the MSPE-ICPMS method have a great potential for adsorption and determination of trace metal ions in environmental water samples.

Phytic acid functionalized magnetic adsorbents for facile enrichment of trace rare earth elements in environmental water, digested atmospheric particulates and the extracts followed by inductively coupled plasma mass spectrometry detection

Phytic acid (PA) functionalized magnetic adsorbents was synthesized through simple process. The functionalized sorbents are featured with core-shell structure, good magnetism, chemical stability, selectivity, and fast adsorption/desorption dynamics for the preconcentration of trace rare earth elements (REEs). With the aid of inductively coupled plasma mass spectrometry detection, the prepared Fe3O4@SiO2@PA sorbents were employed for the separation and enrichment of 15 REEs from environmental water and atmospheric particulates with different sizes. Under the optimal conditions, the method presented an enrichment factor of 300-fold and low detection limits (0.002–1.1 ng/L) for 15 REEs, with the relative standard deviations of 1.4–4.4%. Environmental water samples were analyzed by the proposed method, and 15 REEs of 0.08–5.80 ng/L were found in local rainwater and river water. The REEs concentration in locally collected fine particulate matter was 0.01–0.93 ng/m3, 0.03–1.70 ng/m3 and 0.03–2.47 ng/m3 of REEs were found in inhalable particulate matter and total suspended particulate samples, respectively. The bioaccessibility of REEs in PM2.5 was evaluated by using Gamble's solution extraction, which was calculated to be 0.73–5.46%.

Magnetic Porous Coordination Networks for Preconcentration of Various Metal Ions from Environmental Water Followed by Inductively Coupled Plasma Mass Spectrometry Detection

Magnetic Porous Coordination Networks for Preconcentration of Various Metal Ions from Environmental Water Followed by Inductively Coupled Plasma Mass Spectrometry Detection

Phytic Acid Functionalized Magnetic Adsorbents for Preconcentration of Trace Rare Earth Elements in Environmental Water and Atmospheric Particulates Followed by Inductively Coupled Plasma Mass Spectrometry Detection

Phytic Acid Functionalized Magnetic Adsorbents for Preconcentration of Trace Rare Earth Elements in Environmental Water and Atmospheric Particulates Followed by Inductively Coupled Plasma Mass Spectrometry Detection

Detailed evaluation of conditions of photochemical vapor generation for sensitive determination of nickel in water samples by ICP-MS detection

Photochemical vapor generation (PVG) of Ni was optimized using inductively coupled plasma mass spectrometry detection and a 19 W high-efficiency flow-through photoreactor operated in a flow injection mode (0.49 mL sample volume). The main aim was to achieve very high sensitivity and low limits of detection (LOD) for determination of Ni in fresh water samples, which necessitated to keep low Ni contamination and rather low dilution of samples by added formic acid as a photochemical agent. With respect to that a reaction medium composed of 30% (m/v) formic acid and a flow rate through the photoreactor of 1.5 mL min−1, which corresponds to an irradiation time of 29 s, were chosen as optimal. These PVG conditions were characterized by 42% overall PVG efficiency and by relative and absolute LOD of 1.9 ng L–1 and 0.9 pg, respectively. Almost double efficiency was achievable when pH was adjusted by an addition of 1.5 M ammonium formate, reflected in the proportional increase in sensitivity. However, no significant benefit to analytical performance was found at those conditions. Interferences from inorganic anions likely to be encountered during analytical application to real samples (i.e., NO3−, Cl−, SO42−) were investigated in detail as well as interferences from several transition metals and metalloids. The accuracy was successfully verified by an analysis of the standard reference material NIST 1643f (fresh water) and certified reference materials SLRS-6 (river water), ERM-CA713 (wastewater) and CTA-FFA-1 (fine fly ash), the last one after simple acid digestion. The applicability of this sensitive methodology was further demonstrated by a direct analysis of three water samples (river and well) that were collected and only acidified with formic acid to 30% (m/v).

Selenoproteome Expression Studied by Non-Radioactive Isotopic Selenium-Labeling in Human Cell Lines.

Selenoproteins, in which the selenium atom is present in the rare amino acid selenocysteine, are vital components of cell homeostasis, antioxidant defense, and cell signaling in mammals. The expression of the selenoproteome, composed of 25 selenoprotein genes, is strongly controlled by the selenium status of the body, which is a corollary of selenium availability in the food diet. Here, we present an alternative strategy for the use of the radioactive 75Se isotope in order to characterize the selenoproteome regulation based on (i) the selective labeling of the cellular selenocompounds with non-radioactive selenium isotopes (76Se, 77Se) and (ii) the detection of the isotopic enrichment of the selenoproteins using size-exclusion chromatography followed by inductively coupled plasma mass spectrometry detection. The reliability of our strategy is further confirmed by western blots with distinct selenoprotein-specific antibodies. Using our strategy, we characterized the hierarchy of the selenoproteome regulation in dose–response and kinetic experiments.

Thiol-grafted magnetic polymer for preconcentration of Cd, Hg, Pb from environmental water followed by inductively coupled plasma mass spectrometry detection

A novel thiol-grafted magnetic polymer (MPPs-SH) was synthesized by “click reaction” between 1,2-ethanedithiol and Fe3O4@SiO2@poly (ethylene glycol dimethacrylate -co- glycidyl methacrylate). The resultant MPPs-SH had high S content (5.4 wt%) and exhibited large specific surface area (156.8 m2 g−1) as well as high adsorption capacity of 254, 64.2, 56.6 mg g−1 for mercury, cadmium and lead ions, respectively. With the prepared MPPs-SH as sorbent, a method of magnetic solid phase extraction combined with inductively coupled plasma mass spectrometry was developed for the quantification of trace mercury, cadmium and lead in environmental water samples. The extraction conditions including sample pH, sample volume, sorbent amount, adsorption/desorption time and elution volume were optimized. Under the optimal conditions, three heavy metal ions were extracted from 150 mL aqueous solution in 10 min and eluted by 0.2 mol L−1 HNO3 containing 2% thiourea in 5 min. The method presented low limits of detection (0.21, 0.82 and 2.9 ng L−1) for target ions. The accuracy of the method was validated by using Certified Reference Materials of Environmental Water including GSB 07–1185–2000 (201435), GSB 07–1183–2000 (201239) and GSB 07–3173–2014 (202046). The application potential was further validated by the determination of trace mercury, cadmium and lead in Yangtze river and East lake water samples. The content of target heavy metal ions in tested water sample was found to be in the range of 6.40–195 ng L−1, and the recoveries of 86.4–109% were obtained at three spiking concentration levels for mercury, cadmium and lead ions.

Evaluation of an Element-Tagged Duplex Immunoassay Coupled with Inductively Coupled Plasma Mass Spectrometry Detection: A Further Study for the Application of the New Assay in Clinical Laboratory.

Background: Element-tagged immunoassay coupled with inductively coupled plasma mass spectrometry (ICP-MS) detection has the potential to revolutionize immunoassay analysis for multiplex detection. However, a further study referring to the standard evaluation and clinical sample verification is needed to ensure its reliability for simultaneous analysis in clinical laboratories. Methods: Carcinoembryonic antigen (CEA) and α-fetoprotein (AFP) were chosen for the duplex immunoassay. The performance of the assay was evaluated according to guidelines from the Clinical and Laboratory Standards Institute (CLSI). Moreover, reference intervals (RIs) of CEA and AFP were established. At last, 329 clinical samples were analyzed by the proposed method and results were compared with those obtained with electrochemiluminescent immunoassay (ECLIA) method. Results: The measurement range of the assay was 2–940 ng/mL for CEA and 1.5–1000 ng/mL for AFP, with a detection limit of 0.94 ng/mL and 0.34 ng/mL, respectively. The inter-assay and intra-assay imprecision were all less than 6.58% and 10.62%, respectively. The RI of CEA and AFP was 0–3.84 ng/mL and 0–9.94 ng/mL, respectively. Regarding to clinical sample detection, no significant difference was observed between the proposed duplex assay and the ECLIA method. Conclusions: The ICP-MS-based duplex immunoassay was successfully developed and the analytical performance fully proved clinical applicability. Well, this could be different with other analytes.

Droplet-Splitting Microchip Online Coupled with Time-Resolved ICPMS for Analysis of Released Fe and Pt in Single Cells Treated with FePt Nanoparticles.

The intracellular release of Fe/Pt ions from FePt nanoparticles (NPs) in single cells is highly critical to elucidate the potential cytotoxicity or potential cell protection mechanism of FePt NPs. For the first time, the quantitative analysis of Fe/Pt released from FePt-Cys NPs in single cells was achieved by a droplet-splitting microchip coupled online to inductively coupled plasma mass spectrometry detection. The droplet-splitting chip integrates droplet generation, cell lysis, and droplet-splitting units. The quantification of released Fe/Pt was achieved via measuring standard Fe/Pt ionic solutions. For the determination of total Fe/Pt in single cells, the same microchip with different operation modes (total-mode) was used, and the quantification of total Fe/Pt was achieved with FePt NPs as the standard. The developed method with two analysis modes was applied to study the decomposition behavior of FePt-Cys NPs in single cells, and the results indicated that the percentages of the cells absorbing/decomposing FePt-Cys NPs increased with the incubation time. Almost all cells absorbed FePt-Cys NPs after 6 h, while only about 60% cells decomposed FePt-Cys NPs after 6 h and almost all cells decomposed FePt-Cys NPs after 18 h. Besides, the released Fe content was lower than its endogenous content in cells and the release rate of Pt was higher than that of Fe, providing a possibility that the released Pt may contribute more to cytotoxicity. The developed system enabled fractionation of Fe/Pt in single cells treated with FePt NPs with high accuracy, easy operation, and high throughput and showed a great potential for elemental speciation at the single-cell level.

A Multifunctional Platform for the Capture, Release, And Enumeration of Circulating Tumor Cells Based on Aptamer Binding, Nicking Endonuclease-Assisted Amplification, And Inductively Coupled Plasma Mass Spectrometry Detection.

Inductively coupled plasma mass spectrometry (ICP-MS) combined with element tags has been well designed and extensively applied in cell enumeration. It possesses superior quantitative capability, strong resistance to matrix interference, multiplex detection capability but destructive characteristic. Herein, we constructed an ICP-MS based multifunctional platform for capture, nondestructive enumeration, and release of circulating tumor cells (CTCs). Aptamer on capture probe recognized Mucin 1 (MUC1) on membrane of MCF-7 cells specifically, thus the cells were captured by probe and the Initiator originally hybridized with Aptamer was substituted by MUC1 and released into solution. Then the released Initiator was separated from the captured cells and hybridized with Tb labeled Substrate on detection probe to release a large amount of nicked Tb fragments through the nicking endonuclease assisted amplification for subsequent ICP-MS detection. Meanwhile, cells captured by probe were released by nuclease digestion for further reculture. Such a strategy effectively avoids CTCs destruction resulted from ICP-MS enumeration, increases the detection sensitivity of ICP-MS by involving nicking endonuclease assisted amplification, and realizes cell recovery for further analysis. A limit of detection of 87 MCF-7 cells and a linear range of 250-10 000 MCF-7 cells were realized for ICP-MS enumeration. A cell recovery of 52.7% (with capture and release efficiency of 63.9 and 82.5%, respectively) and a viability of 74.3% were obtained, meanwhile the released cells exhibited strong proliferation ability. This multifunctional platform for CTCs capture, enumeration, and release has great applicable potential in early diagnosis and individual treatment for cancer.

Total metal content and chemical speciation analysis of iron, copper, zinc and iodine in human breast milk using high-performance liquid chromatography separation and inductively coupled plasma mass spectrometry detection

The aim of this research was to quantify essential trace elements (iron, copper, zinc and iodine) and establish their speciation in human milk. Both the element and the species are important in new-born nutrition. Colostrum, and transitional and mature milks (25) were collected from 18 mothers of pre-term or full-term infants. Concentrations of the target elements were determined using ICP-MS. For speciation, HPLC coupled to ICP-MS was employed. Total contents of the micronutrients varied in mothers of pre-term (Fe = 0.997, Cu = 0.506, Zn = 4.15 and I = 0.458 mg L−1) and mothers of full-term (Fe = 0.733, Cu = 0.234, Zn = 2.91 and I = 0.255 mg L−1) infants. Fe, Cu and Zn were associated with biomolecules with high molecular mass compounds, such as immunoglobulins, albumin and lactoferrin whilst iodine was only found as iodide.

Simultaneous determination of gastric cancer biomarkers pepsinogen PGI/PGII using element tagged immunoassay coupled with inductively coupled plasma mass spectrometry detection.

ObjectivesIn this study, a new immunoassay for the simultaneous determination of pepsinogen I (PGI) and pepsinogen II (PGII) in serum based on element labeling strategy coupled with inductively coupled plasma mass spectrometry (ICP‐MS) detection was proposed.MethodsThe sandwich‐type immunoassay was used to simultaneously detect PGI and PGII in serum. PGI and PGII were captured by anti‐PGI and anti‐PGII antibody immobilized on the magnetic beads and then banded with Eu3+ labeled anti‐PGI detection antibody and Sm3+ labeled anti‐PGII detection antibody, followed by ICP‐MS detection.ResultsThe linear correlation coefficient (R 2) of PGI and PGII standard curves was .9938 and .9911, with the dynamic range of 0‐200 ng/mL and 0‐60 ng/mL, respectively. The limit of detection for PGI and PGII was 1.8 ng/mL and 0.3 ng/mL, respectively. The average recovery was 101.41% ± 6.74% for PGI and 101.47% ± 4.20% for PGII. Good correlations were obtained between the proposed method and CLIA (r = .9588 for PGI, r = .9853 for PGII).ConclusionsWe established a mass spectrometry‐based immunoassay for the simultaneous detection of PGI and PGII in a single analysis. The element tagged immunoassay coupled with ICP‐MS detection has high sensitivity, accuracy, and specificity in clinical serum sample analysis.

Phosphoric acid functionalized magnetic sorbents for selective enrichment of TiO2 nanoparticles in surface water followed by inductively coupled plasma mass spectrometry detection

Phosphoric acid functionalized superparamagnetic iron oxide was synthesized, and different adsorption behavior of TiO2 NPs and titanium ions on it was found. By means of dispersion-corrected density functional theory (DFT-D), the adsorption mechanism of TiO2 NPs and titanium ions on the functionalized sorbents was explored, and the difference in the adsorption behavior was attributed to the different deprotonated forms of phosphates and the competitive adsorption of OH– anion with respect to either TiO2 NPs or aqueous titanium ions. Based on the different adsorption performance of phosphoric acid functionalized sorbents for TiO2 NPs and titanium ions under pH 3, a method by combining magnetic solid phase extraction (MSPE) with inductively coupled plasma mass spectrometry (ICP-MS) was established for the selective quantification of trace TiO2 NPs in environmental water. Under the optimal experimental conditions, the detection limit of TiO2 NPs was 17 ng/L with an enrichment factor of 400. The developed MSPE-ICPMS method was applied to the detection of trace TiO2 NPs in the Yangtze River and the East Lake water. Sub μg/L level of TiO2 NPs was found in the tested water samples, and recoveries of 91–110% and 90–110% were obtained for TiO2 NPs at three concentration levels in spiked water samples, respectively. The developed method exhibited high adsorption capacity and low detection limit for target TiO2 NPs, and was demonstrated with great potential for monitoring TiO2 NPs in the environment.

Comprehensive two-dimensional liquid chromatography with inductively coupled plasma mass spectrometry detection for the characterization of sulfur, vanadium and nickel compounds in petroleum products

The petroleum industry is increasingly concerned with the conversion of vacuum residues as a consequence of decreased conventional crude oil availability. The compositional analysis of heavy oil products has become a key step in conversion processes, but the complexity of these oil matrices tends to increase with their boiling point. In this study, comprehensive two-dimensional liquid chromatography (LCxLC) coupled to inductively coupled mass spectrometry (ICP-MS/MS) is considered with a view to meet new requirements and to bring additional information regarding the species present in these matrices. In search for a high degree of orthogonality, two separation techniques involving two different retention mechanisms were evaluated: Size Exclusion Chromatography (SEC) and Reverse Phase Liquid Chromatography (RPLC). In SEC, the analytes are separated according to their molecular weight while according to their hydrophobicity in RPLC. The separation power of both individual separation techniques was first evaluated. Off-line and on-line LCxLC were compared on the basis of an optimization approach. It is shown that off-line SECxRPLC can provide, for the same analysis time of 150 min, a higher peak capacity (2600 vs 1700) than on-line RPLCxSEC while a similar dilution factor (close to 30) but also requires far fewer fractions to be analyzed (12 vs 400). Asphaltenes which constitute the heaviest fraction of crude oils (obtained from petroleum industry) were analyzed by the developed off-line SECxRPLC method. The resulting 2D-contour plots show that co-elutions could be removed leading, for the first time, to new information on high molecular weight species containing sulfur and vanadium.