Mass-shift Mode Research Articles

Characterisation of titanium dioxide (nano)particles in foodstuffs and E171 additives by single particle inductively coupled plasma-tandem mass spectrometry using a highly efficient sample introduction system

This study addressed primarily the characterisation and quantification of titanium dioxide (TiO2) (nano)particles (NPs) in a large variety of commercial foodstuffs. The samples were purchased from local markets in Spain before the ban of TiO2 food additive (E171) in the EU. The analyses were carried out by single particle inductively coupled plasma-tandem mass spectrometry (spICP-MS/MS) in mass shift mode (oxidation of 48Ti to 48Ti16O (m/z = 64)) and using a highly efficient sample introduction system (APEX™ Ω). This novel analytical approach allowed accurate characterisation of a large panel of TiO2 NPs sizes ranging from ∼12 to ∼800 nm without isobaric interferences from 48Ca isotope, which is highly abundant in most of the analysed foodstuffs. TiO2 NPs were extracted from foodstuffs using sodium dodecyl sulphate (0.1%, w/v) and diluted with ultra-pure water to reach ∼ 1000 particles signals per acquisition. All the analysed samples contained TiO2 NPs with concentrations ranging from 1010 to 1014 particles kg−1, but with significant low recoveries compared to the total Ti determination. A selection of samples was also analysed using a similar spICP-MS/MS approach with a conventional sample introduction system. The comparison of results highlighted the improvement of the limit of detection in size (12 nm) by the APEX™ Ω system, providing nanoparticulate fractions ranging from ∼4% (cheddar sauce) up to ∼87% (chewing gum), which is among the highest nanoparticulate fractions reported in literature using a spICP-MS approach. In addition, two commercially available E171 additives were analysed using the previous approaches and other techniques in different European laboratories with the aim of methods inter-comparison. This study provides occurrence data related to TiO2 NPs in common commercial foodstuffs but it also demonstrates the potential of the novel analytical approach based on APEX™-ICP-MS/MS to characterise nano-size TiO2 particles in complex matrices such as foodstuffs.

Measurement of ultra-trace level 237Np in soil and sediment by triple-quadrupole inductively coupled plasma-mass spectrometry with different mass modes combined with chemical separation

Long-lived trans‑uranium nuclides such as 237Np, may reside in the environment for long period and result in ecological impact and human health threat. Accurate measurement of 237Np in the environment is important for the risk assessment and ecological evaluation. However, the spectral peak tailing and polyatomic ions interference greatly limit the measurement of 237Np with triple quadrupole ICP-MS (ICP-MS/MS), which have been successfully used for analysis of ultra-trace level 239,240Pu and 241Am. The novel methods for 237Np measurement with ICP-MS/MS in both on-mass and mass-shift modes were examined in this paper. When helium was used as the collision gas for the ICP-MS/MS measurement with on-mass mode, the interference contribution to the counts for 237Np (at m/z 237) as low as 4 × 10−8 was observed only from Hg, while no measurable interference from Tl and Pb was observed. Moreover, when the mass-shift mode is employed with O2/He and He as the collision/reaction gas, the interference contributions from Hg, Tl and Pb were all negligible. The detection limit of 237Np was reduced to 0.014 fg/g and 0.019 fg/g for on-mass and mass-shift mode, respectively. The novel methods were demonstrated to enable accurate determination of 1.0 fg/g level 237Np in the emulated sample solutions with a 237Np/238U atomic ratio as low as 10−9. Combined with appropriate chemical separation procedure, the developed methods were verified with certified reference materials and soil samples.

Assessment of TiO2 (nano)particles migration from food packaging materials to food simulants by single particle ICP-MS/MS using a high efficiency sample introduction system

TiO2 is the most widely used white pigment in plastics and food packaging industry, thus the question of its migration towards food and hence the impact on consumers is raised. Since recent research indicate its potential toxicity, it is necessary to study TiO2 contamination as a consequence of food storage. For this purpose, plastic containers from commercially-available dairy products and custom-made TiO2-spiked polypropylene materials were put in contact with 50% (v/v) ethanol and 3% (w/v) acetic acid, which were used here as food simulants. The migration assays were carried out under standard contact conditions of packaging use (as recommended by Commission Regulation (EU) N° 10/2011 for food contact migration testing), and under conditions of extreme mechanical degradation of the packaging. The TiO2 (nano)particles released in the food simulants were analysed by single particle inductively coupled plasma-tandem mass spectrometry in mass-shift mode and using a high efficiency sample introduction system (APEX™ Ω) to avoid matrix effects from food simulants. For the dairy product containers and for the spiked polypropylene, results showed release of TiO2 particles of rather large sizes (average size: 164 and 175 nm, respectively) under mechanical degradation conditions, i.e. when the polymeric structure is damaged. The highest amounts of TiO2 were observed in 50% ethanol after 10 days of storage at 50 °C (0.62 ng cm−2) for the dairy product containers and after 1 day of storage at 50 °C (0.68 ng cm−2) for the spiked polypropylene. However, the level of Ti released in particle form was very small compared to the total Ti content in the packaging and far below the acceptable migration limits set by European legislation. Release under standard contact conditions of use of the container was not measurable, thus the migration of TiO2 particles from this packaging to dairy products among storage is expected to be negligible.

Simultaneous Determination of Transuranium Radionuclides in Urine by Tandem Quadrupole ICP-MS/MS with Mass-Shift Mode Combined with Chemical Separation.

The urine bioassay method for transuranium nuclides (237Np, 239,240,241Pu, 241Am, and 244Cm) is needed to quickly assess the potential internal contamination in emergency situations. However, in the case that the analysis of multiple radionuclides is required in the same sample, time-consuming/tedious sequential analytical procedures using multiple chromatographic separation resins would have to be employed for the separation of every single radionuclide. In this work, a rapid method for the simultaneous determination of transuranium nuclides in urine was developed by using triple quadrupole inductively coupled plasma mass spectrometry (ICP-MS/MS) combined with a single DGA resin column. The chemical behaviors of Np/Pu and Am/Cm on the DGA resin were consistent in 8-10 mol/L HNO3 and 0.005-0.02 mol/L NaNO2 when 242Pu and 243Am were selected as tracers for Np/Pu and Am/Cm yield monitoring. Based on their different reaction rates with O2, 237Np, 239,240,241Pu, 241Am, and 244Cm in the same solution were simultaneously measured by ICP-MS/MS in the same run. The elimination efficiency of 238U+ tailing (7.43 × 10-9), 238U1H16O2+/238U16O2+ (8.11 × 10-8) and cross contamination of 241Pu and 241Am (<1%) were achieved using 10.0 mL/min He-0.3 mL/min O2 even if the eluate was directly measured without any evaporation. The detection limits of transuranium nuclides were at the femtogram level, demonstrating the feasibility of ICP-MS/MS for simultaneous transuranic radionuclides urinalysis. The developed method was validated by analyzing the spiked urine samples.

Direct accurate Eu anomaly analysis in very high Ba/Eu silicate samples by triple-quadrupole ICP-MS in MS/MS mass shift mode

The concentration of Eu relative to neighbouring rare earth elements (REE) is an important tool in petrology and geobiology. In most sample matrices, precise and accurate middle REE concentration data can be obtained by direct ICP-MS analysis with careful correction of interferences (chiefly, BaO+ on Eu+ and NdO+ on Gd+). However, geologically interesting samples, including sediments from mid-ocean-ridge and other hydrothermal settings, certain limestones, Precambrian cherts, and some alkali-feldspars have such high Ba/Eu ratios that signals on both Eu isotopes are dominated by BaO. This necessitates high resolution mass spectrometry, highly accurate oxide-correction in these matrices, or requires the separation of the REE from the Ba-rich matrix prior to ICP-MS analysis. Here we report experiments with a triple-quadrupole ICP-MS where Eu was analysed as the mass shifted EuO+ after reaction with N2O or O2 for analysis of Palaeoarchaean cherts. Results were compared to conventional REE analysis with a generic oxide correction as well as individual sample oxide correction. It was found that the triple-quadrupole ICP-MS method with N2O reaction and the conventional ICP-MS analysis with individual sample oxide correction yielded indistinguishable middle REE data for samples with Ba/Eu of up to 125,000. The other two methods overestimated the Eu concentration in samples with Ba/Eu > 10,000, leading to spuriously high positive Eu anomalies, which could be misinterpreted as dominant high-temperature hydrothermal venting into the ancient ocean, for which there is currently no convincing evidence. The triple-quadrupole ICP-MS method with N2O reaction offers a fast, low-blank and high-sensitivity solution to REE analysis of high Ba/Eu geological matrices. Based on the insight from these experiments, we propose criteria with which legacy Eu anomaly data can be assessed for accuracy and inclusion into deep time secular trend studies.

Characterisation and quantification of titanium dioxide nanoparticles in food simulants by single particle inductively coupled plasma-tandem mass spectrometry using a high efficiency sample introduction system

This article reports the development of a novel method based on single particle inductively coupled plasma-tandem mass spectrometry (ICP-MS/MS) using a high efficiency sample introduction system (HESIS) for the characterisation and quantification of titanium dioxide (nano)particles (TiO2 NPs) in food simulants. The use of the mass-shift mode (O2 + H2 as a mixture reaction gas) avoids the isobaric interferences of 48Ca isotope hence allowing accurate characterisation of TiO2 NPs in complex matrices such the foodstuffs. Two HESIS (APEX™ Q and APEX™ Ω) were compared with the conventional ICP-MS/MS sample introduction system in terms of sensitivity and trueness for the detection of TiO2 NPs in various (organic) food simulants. APEX™ Ω proved to be an excellent approach to avoid matrix effects from food simulants and provided significantly lower limits of detection in size (LODsize) compared to the conventional introduction system. In order to avoid the saturation of the detector when detecting large TiO2 particles (> 300 nm), the analyses were carried out using the forced analogue detection mode and accurate characterisation of TiO2 NPs in terms of size and concentration was achieved, with an average LODsize of 20 nm over 3 days. This confirms the feasibility of this novel approach using an APEX™ Ω for the characterisation and quantification of TiO2 NPs in complex matrices such as the food simulants and its application to real-life studies regarding the migration of TiO2 NPs from food containers into the simulants.

Ultra-sensitive speciation analysis of tellurium by manganese and iron assisted photochemical vapor generation coupled to ICP-MS/MS

Photochemical vapor generation (PVG) of Te4+ was undertaken with a simple reactor consisting of a polytetrafluoroethylene reaction coil wrapped around a low-pressure mercury tube lamp and using a flow-injection for sample delivery. The composition of a reaction medium, the influence of irradiation time and the effect of added sensitizers and interferents were investigated using high-resolution continuum source atomic absorption spectrometry and a miniature diffusion flame atomizer. A mixture of 5 M acetic acid and 3.5 M formic acid and sample flow rate of 4 mL min−1 permitting a 36 s irradiation time were found optimal for PVG of Te4+. The addition of 250 mg L−1 Mn2+ and 15 mg L−1 Fe2+ ions as sensitizers enhanced the overall PVG efficiency 2.75-fold to 50 ± 2%. In order to achieve higher sensitivity necessary for determination of Te in real environmental samples, PVG was coupled to inductively coupled plasma triple quadrupole mass spectrometer and detection was performed with O2 in the reaction cell utilizing a mass shift mode of measurement (m/z 128 → m/z 144) to ensure interference free ion detection. A limit of detection 1.3 ng L−1 and repeatability (RSD) 0.9% at 250 ng L−1 were achieved. This ultrasensitive methodology was validated for speciation analysis of Te in water samples of various matrix complexities (fresh water, well water, seawater and contaminated water). Since no response was observed from Te6+ under optimal PVG conditions, Te4+ was selectively determined by direct PVG. The sum of Te4+ and Te6+ was determined after pre-reduction of Te6+ in 6 M HCl (95 °C), evaporation to dryness and reconstitution in the reaction medium containing sensitizers. Very good accuracy was demonstrated by spiked recoveries for both Te4+ and total Te in water samples and also by total Te determination in fresh water Standard Reference Material NIST 1643f.

Determination of Ethyl Xanthate in Aqueous Solution by High Performance Liquid Chromatography–Inductively Coupled Plasma–Tandem Mass Spectrometry and Spectrophotometry

Xanthates are commonly used collectors in flotation processes but are highly toxic to the aquatic environment. However, there are few methods for reliable determination of low xanthate concentrations in water samples. In this work, a sensitive, selective, and fast method is presented for the determination of potassium ethyl xanthate (KEX). KEX was determined by high-performance liquid chromatography–inductively coupled plasma–mass spectrometry (HPLC-ICP-MS/MS) directly and as diethyl dixanthogen [(EX)2] after oxidation with triiodide. The HPLC method was optimized for (EX)2 and the separated compounds were detected by ICP-MS/MS. The ICP-MS/MS was used in mass-shift mode using O2 as the cell gas and S+ was measured as SO+ to reduce spectral interferences. Detection limits of 88 µg L−1 for KEX and 20 µg L−1 for (EX)2 calculated from the peak area were obtained using mass-shift 32S+ → 32S16O+. No significant matrix effects were present when spiking experiments of (EX)2 were done to a sample collected from the tailings of a flotation process. The developed method demonstrates the potential of the HPLC-ICP-MS/MS for the determination of ethyl xanthate. This method may be extended to analyzing other xanthates and similarly structured sulfur containing collectors.

Determination of ultra-trace level241Am in soil by triple-quadrupole inductively coupled plasma-mass spectrometry with mass-shift mode combined with chemical separation

ICP-MS/MS measurement with mass-shift mode using O2/He–He collision gas can effectively suppress the interference of polyatomic ions from interfering elements (Pb, Hg, Tl,etc.) in analysis of ultra-trace level241Am in environmental samples.

Mass-shift mode to quantify low level129I in environmental samples by ICP-MS/MS

Mass shift measurement mode in ICP-MS/MS was used for the first time to improve the limit of detection of129I and129I/127I.

Correction: Mass-shift mode to quantify low level 129I in environmental samples by ICP-MS/MS

Correction for ‘Mass-shift mode to quantify low level 129I in environmental samples by ICP-MS/MS’ by Coralie Carrier et al., J. Anal. At. Spectrom., 2022, 37, 1309–1317, https://doi.org/10.1039/D2JA00128D.

Development and Co-Validation of a Certified Reference Material (NMIJ CRM 7204-A) for the Analysis of Trace Elements in Seawater Sample

Abstract A certified reference material (CRM), i.e. NMIJ CRM 7204-a, was characterized for the analysis of 10 regulated trace elements in sample seawater, provided in 500 mL polyethylene bottles. Homogeneity and stability of the elements were investigated by inductively coupled plasma tandem quadrupole mass spectrometry after proper dilution, while mass-shift mode was applied to the measurement of trace elements except for Cd and Pb. A property value was obtained as the weighted mean of the results obtained by different methods with weights based on the reciprocal of the standard uncertainty. Combined uncertainty of a property value was obtained as the root mean square of the standard uncertainties of homogeneity, stability, analysis reproducibility, method-to-method variance, and calibrating standard. In NMIJ CRM 7204-a, the concentration of Cd is approximately 3 µg/kg, while those of other trace elements are around 10 µg/kg. Validity of the certified values was confirmed with analytical results of As and Cd by National Institute of Metrology (NIM, China) and those of Cd and Ni by Korea Research Institute of Standards and Science (KRISS, Korea). The concentrations of Na, Mg, K, and Ca along with the density values at 15, 20, and 25 Celsius were provided as information values.

Determination of ultra-trace level plutonium isotopes in soil samples by triple-quadrupole inductively coupled plasma-mass spectrometry with mass-shift mode combined with UTEVA chromatographic separation

Although triple-quadrupole inductively coupled plasma-mass spectrometry (ICP-MS/MS) has become an attractive technique for the measurement of long-lived radionuclides, the abundance sensitivity, isobaric and polyatomic ions interferences seriously restrict the application. The spectral peak tailing and uranium hydrides (UH+, UH2+) from 238U have a serious influence on the accurate measurement of 239Pu and 240Pu, especially for the ultra-trace level plutonium isotopes in the higher uranium sample. A new method was developed using ICP-MS/MS measurement in mass-shift mode with collision-reaction gas combined with a chemical separation procedure. As O2 readily converted Pu+ ion to PuO2+, while disassociated the interfering diatomic ions of interfering elements (U, Pb, Hg, Tl, etc.), the interferences from these elements were completely eliminated if plutonium was detected as PuO2+ at the m/z more than 270. By the mass filter in MS/MS mode combined with O2 as reaction gas the lower peak tailing of 238U+ (<5 × 10−12) was significantly suppressed. By this way, the 238UO2H+/238UO2+ atomic ratio was reduced to 4.82 × 10−9, which is significantly lower than that of other collision-reaction gas modes. Interferences from Pb, Hg and Tl polyatomic ions were also completely eliminated. Thus, accurate measurement of ultra-trace level 239Pu in high uranium sample solutions with the 239Pu/238U concentration ratio of 10−10 was achieved by the mass-shift mode with 0.15 mL/min O2/He + 12.0 mL/min He as collision-reaction gas, and high elimination efficiency of uranium interferences up to 1014 can be obtained by combination with the chemical separation using a single UTEVA resin column. The developed method can be applied to accurately determine the fg level 239Pu in high uranium samples, such as large-size deep seawater, deep soil and sediment, uranium debris of nuclear fuel.

Investigating the feasibility of ICP-MS/MS for differentiating NIST salmon reference materials through determination of Sr and S isotope ratios

Inductively coupled plasma tandem mass spectrometry (ICP-MS/MS) was investigated for possible use in food fraud studies through the measurement of strontium and sulfur isotope ratios. Oxygen mass shift mode was applied to shift 87Sr/86Sr and 34S/32S isotope ratios to their respective oxides, 87Sr16O+/86Sr16O+ and 34S16O+/32S16O+, effecting a gas-phase chemical separation of the elements from Rb and Kr (for Sr) and molecular N and O species, along with P- and S-hydrides (for S). A total least squares regression approach was employed to generate the isotope ratio data from time-resolved analyses, and method uncertainties and accuracies were determined. The utility of the approach was shown by using the Sr and S isotope ratios together to differentiate between NIST RM 8256 Wild-Caught Coho Salmon and NIST RM 8257 Aquacultured Coho Salmon. These materials are currently under development at NIST as certified food fraud standards and method evaluation materials for comprehensive chemical analysis.

Simultaneous determination of zircon U-Pb age and titanium concentration using LA-ICP-MS: Analysis data and crystallization temperature.

Simultaneous determination of zircon U–Pb age and titanium concentration for a single analysis spot gives both the crystallization age and temperature. In laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS) analysis, it is challenging to quantitatively analyse a low level of titanium concentration. Two approaches were employed using a quadrupole mass spectrometer equipped with a collision/reaction cell (CRC). In the first approach, the MS/MS mass-shift mode with oxygen reaction gas provided reliable and consistent measurement of titanium as 48Ti16O+. In the second approach, the titanium concentration was determined quantitatively from the signal intensity of 49Ti in the non-gas mode (without the inflow of collision/reaction gas into the CRC). The methods were applied to zircon samples of the Kurobegawa granite (KRG), the Okueyama granite (OKG), the Toki granite (TKG), and the Tono plutonic complex (TCP). The biotite K–Ar geochronology were employed for rock samples of the KRG, OKG, and TPC (N = 3) of which the zircon crystals were analysed. The obtained titanium concentrations of the zircon crystals can lead to the crystallization temperatures through Ti-in-zircon geothermometer.

Simultaneous determination of zircon U–Pb age and titanium concentration using LA-ICP-MS for crystallization age and temperature

Simultaneous determination of zircon U–Pb age and titanium concentration for a single analysis spot gives both the crystallization age and temperature. The crystallization age and temperature pairs in granitic zircons map the time–temperature (t–T) path of granitic magma before its solidification. In laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS) analysis, it is challenging to quantitatively analyse a low level of titanium concentration. This study employed two approaches using a quadrupole mass spectrometer equipped with a collision/reaction cell (CRC). In the first approach, the MS/MS mass-shift mode with oxygen reaction gas provided reliable and consistent measurement of titanium as 48Ti16O+. In the second approach, the titanium concentration was determined quantitatively from the signal intensity of 49Ti in the non-gas mode (without the inflow of collision/reaction gas into the CRC). The methods were applied to zircon samples of the Kurobegawa granite (KRG), the Okueyama granite (OKG), the Toki granite (TKG), and the Tono plutonic complex (TCP), and provided U–Pb ages and titanium concentrations consistent with previous studies. The crystallization ages and temperatures collected from individual analysis spots of zircon samples in the KRG, OKG, TKG, and TCP were plotted in the t–T diagrams and enabled us to characterize the rapid cooling paths at thermal conditions of zircon crystallization at the sampling sites.

Determination of rare earth elements in seawater samples by inductively coupled plasma tandem quadrupole mass spectrometry after coprecipitation with magnesium hydroxide

Coprecipitation with magnesium hydroxide was investigated as a pretreatment method for the determination of rare earth elements (REEs) in seawater samples, both for separation of the salt contents and for the enrichment of REEs. The precipitate of magnesium hydroxide was collected on a syringe filter and then subjected to the on-line measurement of REEs by an inductively coupled plasma tandem quadrupole mass spectrometer (ICP-MS/MS). Coprecipitation resulted in a separating rate of over 99% for salt contents, while the on-line measurement of REEs in the magnesium hydroxide provided an enhancement factor of 130-fold for the transient peak height of signal intensities. Mass-shift mode was applied to the measurement of REEs by ICP-MS/MS, where each isotope of the REEs was permitted to pass the first QMS and to react with oxygen gas in the reaction cell so as to form a monoxide ion, which was permitted to pass the second QMS and then measured by the detector. Mass-shift to monoxide ion effectively removed the spectral interferences in the measurement of REEs and permitted the correct determination of REEs in seawater samples. Detection limits were calculated based on the results of 10-set of the replicated blank test, which were low enough for the determination of REEs in natural seawater samples. The effectiveness of the present method was confirmed by the analysis of three certified reference materials of seawater, i.e. CASS-4, CASS-5, and NASS-6.

A new method for determining 236U/238U isotope ratios in environmental samples by means OF ICP-MS/MS

The 236U/238U isotope ratio is a widely used tracer, which provides information on source identification for safeguard purposes, nuclear forensic studies and environmental monitoring. This paper describes an original approach to determine 236U/238U ratios, below 10−8, in environmental samples by combination of ICP-MS/MS for 236U/238U ratio and multiple collector ICPMS measurements for 235U/238U and 234U/235U isotope ratios.Since the hydride form of UO+ (UOH+) is less prone to occur than UH+, we were focused on the oxidised forms of uranium in order to reduce hydride based-interferences in ICP-MS/MS. Then, in-cell ion-molecule reactions with O2 and CO2 were assessed to detect the uranium isotopes in mass-shift mode (Q1: U+ → Q2: UO+). The performances in terms of UO+ sensitivity and minimisation of hydride form of UO+ were evaluated using five different desolvating systems. The best conditions, using an Apex Ω or an Aridus system, produced uranium oxide hydride rate (235U16O1H+/235U16O+) of about 10−7 with O2 in the collision cell.The method was validated through measurements of two certified IRMM standards with 236U/238U isotope ratio of 1.245 × 10−7 and 1.052 × 10−8, giving results in agreement with certified reference values. The relative standard deviations on seven independent measurements for each standard were respectively of 1.5% and 6.2%. Finally, environmental samples corresponding to sediments from the radioactive contamination plume emitted by the Fukushima Daiichi Nuclear Power Plant accident were analysed after a well-established uranium chemical separation procedure. 236U/238U atomic ratios between 1.5 × 10−8 and 7 × 10−9 were obtained with a level accuracy lower than 20%.

Determination of polybrominated diphenyl ethers in fish tissue using gas chromatography-isotope dilution tandem inductively coupled plasma mass spectrometry with a mass-shift mode

Gas chromatography inductively coupled plasma triple quadrupole mass spectrometry (GC-ICP-MS/MS) operated in N2O reaction mode (mass-shift mode) was established for the analysis of six congeners of polybrominated diphenyl ethers (PBDEs): BDE 28, BDE 47, BDE 99, BDE 100, BDE 153 and BDE 154 in fish samples. The spectral interference on the determination of PBDEs was eliminated by measuring the product ion (BrO+) instead of traditional methods measuring Br+. After comparing the signal intensities of the three reaction gases (O2, H2, and N2O), the highest sensitivity was found using N2O as the reaction gas. The results showed that bromine is an element that suffers from strong spectral overlap in ICP, mainly from Ar-based polyatomic interferences. Spectral interference was assessed by measuring the bromine isotope ratio of 81Br+ and 79Br+ of the six priority PBDEs in the He collision mode and N2O reaction mode, respectively. In the conventional He collision mode, the relative isotope ratio of 79Br/81Br (the measured isotope ratio to the natural isotope ratio) of the analytes ranged from 0.955 to 0.965, which proves that using He as the collision gas cannot completely eliminate the spectral interference. In the N2O reaction mode, the relative isotope ratio of 79Br/81Br ranged from 0.991 to 1.004, demonstrating that spectral interference can be fully eliminated. Samples were processed using the modified QuEChERs method with detection limits ranging from 0.03 to 0.09 ng g−1 with a relative standard deviation of less than 3%. Six priority PBDEs in the NIST reference materials SRM 1947 (frozen fish tissue homogenate) were determined by mass-shift mode to verify this conclusion. No statistically significant difference was observed between the measured value and the certified value, with recoveries between 95% and 114%. The method was applied to the analysis of PBDEs in marine fish samples and five PBDEs were observed (BDE28,BDE-47, BDE-99, BDE-100 and BDE-153) at concentrations ranging from 0.04 to 0.54 ng g−1.

Arsenic Speciation of Edible Shrimp by High-Performance Liquid Chromatography-Inductively Coupled Plasma-Mass Spectrometry (HPLC-ICP-MS): Method Development and Health Assessment

This study aimed at developing an accurate method for determining the levels of total arsenic (As) and arsenic species in edible shrimp with the collision/reaction cell (CRC) in the O2 mass-shift mode to remove interferences. The microwave-assisted extraction method demonstrated satisfactory efficiency (86.9%), and As species were separated rapidly within 11 min when the optimized chromatographic conditions were adopted. During the study, the limits of detection, precision, and spike recovery for six arsenic species were in the ranges from 0.010 to 0.028 μg/L, 1.89 to 3.14%, and 96.9 to 103.2%, respectively. The analytical methods were successfully applied to determine the concentrations of total arsenic and As species in eight shrimp samples. The results showed that arsenobetaine was the predominant As species, and inorganic arsenic contents were below 0.5 mg/kg in the shrimp samples analyzed. The health risk assessment indicated that the shrimp samples detected posed no particular risk of As to local consumers.