Measurement of trace elements in murine liver tissue samples: Comparison between ICP-MS/MS and TXRF

BACKGROUND

Trace elements exhibit essential functions in many physiological processes. Thus, for research focusing on trace element homeostasis and metabolism analytical methods allowing for multi-element analyses are fundamental. Small sample amounts may be a big challenge in trace element analyses especially if also other end points want to be addressed in the same sample. Therefore, the aim of the present study was to examine trace elements (iron, copper, zinc, and selenium) in murine liver tissue prepared by a RIPA buffer-based lyses method.

METHODS AND RESULTS

After centrifugation, lysates and pellets were obtained and trace elements were analyzed with TXRF in liver lysates. The results were compared to that obtained by a standard microwave-assisted acidic digestion with subsequent ICP-MS/MS analysis of the same liver tissue, liver lysates, and remaining pellets. In addition, trace element concentrations, determined in murine serum with both methods, were compared. For serum samples, both TXRF and ICP-MS/MS provide similar and highly correlating results. Furthermore, in liver lysate samples prepared with RIPA buffer, comparable trace element concentrations were measured by TXRF as with the standard digestion technique and ICP-MS/MS. Only marginal amounts of trace elements were detected in the pellets.

CONCLUSION

Taken together, the results obtained by the present study indicate that the RIPA buffer-based method is suitable for sample preparation for trace element analyses via TXRF, at least for the here investigated murine liver samples.

Determination of ultra-trace levels of titanium in human serum using inductively coupled plasma tandem mass spectrometry based on O2/H2 reaction gas

This study proposes a new strategy to determine ultra-trace Ti in human serum using inductively coupled plasma tandem mass spectrometry (ICP-MS/MS). The human serum samples were diluted with 1% (v/v) HNO₃, followed by the determination of ultra-trace Ti using ICP-MS/MS. In the MS/MS mode, a small amount of H₂ was mixed with O₂ (the reaction gas) in a collision reaction cell (CRC) to form an O₂/H₂ reaction mixture, and then, the conversion of Ti⁺ to TiO⁺ was determined by the O₂ mass shift method. High concentrations of Ca, S, and P in human serum were ionized in plasma, and the formed Ca⁺, SO⁺, and PO ⁺ reacted with O₂ in CRC to form CaO⁺, SO₂⁺, and PO₂⁺ to interfere with the determination of TiO⁺. We employed the mass shift reaction of H₂ and oxide ions to eliminate this interference. This method was evaluated using the human serum sample spike recovery experiment and comparative analysis by sector field (SF)-ICP-MS. The results showed that using reaction gas mixture O₂/H₂ reduced the background equivalent concentration (BEC) of Ti and improved sensitivity. The values determined by this method were consistent with the SF-ICP-MS values, which confirmed its accuracy and reliability. The limit of detection (LOD) of Ti was 0.78-7.20 ng L^-1, the recovery was 96.0%-104%, and the relative standard deviation (RSD) was 2.0%-4.2%. This method has solved the problem that the determination of ultra-trace Ti in human serum cannot be accurately determined using O₂ reaction mode. It realizes the interference-free and highly sensitive determination of the ultra-trace Ti in samples with high levels of Ca, S, and P and provides a new technique for high-throughput and accurate determination of ultra-trace Ti in human serum.

A CE-ICP-MS/MS method for the determination of superparamagnetic iron oxide nanoparticles under simulated physiological conditions

Over the past few years, superparamagnetic iron oxide nanoparticles (SPIONs) have attracted much attention due to their medicinally attractive properties and their possible application in cancer diagnosis and therapy. However, there is still a lack of appropriate methods to enable quantitative monitoring of the particle changes in a physiological environment, which could be beneficial for evaluating their in vitro and in vivo behavior. For this reason, the main goal of this study was the development of a novel capillary electrophoresis-inductively coupled plasma mass spectrometry (CE-ICP-MS/MS) method for the determination of SPIONs suitable for the future examination of their changes upon incubation with proteins under simulated physiological conditions. The type and flow rate of the collision/reaction gas were chosen with the aim of simultaneous monitoring of Fe and S. The type and concentration of the background electrolyte, applied voltage, and sample loading were optimized to obtain SPION signals of the highest intensity and minimum half-width of the peak. Analytical parameters were at a satisfactory level: reproducibility (intra- and inter-day) of migration times and peak areas (presented as RSD) in the range of 0.23-4.98%, recovery: 96.7% and 93.3%, the limit of detection (for monitoring 56Fe16O+ by mass-shift approach) 54 ng mL-1 Fe (0.97 μM) and 101 ng mL-1 Fe (1.82 μM) for SPIONs with carboxyl and amino terminal groups, respectively. To the best of our knowledge, this is the first reported use of CE-ICP-MS/MS for the quantification of SPIONs and monitoring of interactions with proteins.

Multielement analysis of Zanthoxylum bungeanum Maxim. essential oil using ICP-MS/MS

The concentrations of trace elements (Cr, Ni, As, Cd, Hg, and Pb) in Zanthoxylum bungeanum Maxim. essential oil (ZBMEO) were determined by inductively coupled plasma tandem mass spectrometry. The ZBMEO sample was directly analyzed after simple dilution with n-hexane. Aiming for a relatively high vapor pressure of n-hexane and its resultant loading on plasma, we used a narrow injector torch and optimized plasma radio frequency power and carrier gas flow to ensure stable operation of the plasma. An optional gas flow of 20% O₂ in Ar was added to the carrier gas to prevent the incomplete combustion of highly concentrated organic carbon in plasma and the deposition of carbon on the sampling and skimmer cone orifices. In tandem mass spectrometry mode, O₂ was added to the collision/reaction cell to eliminate the interferences. The limits of detection for Cr, Ni, As, Cd, Hg, and Pb were 2.26, 1.64, 2.02, 1.35, 1.76, and 0.97 ng L^-1, respectively. After determination of 23 ZBMEO samples from different regions in China, we found that the average concentration ranges of trace elements in the 23 ZBMEO samples were 0.72-6.02 ng g^-1, 0.09-2.87 ng g^-1, 0.21-5.84 ng g^-1, 0.16-2.15 ng g^-1, 0.13-0.92 ng g^-1, and 0.17-0.73 ng g^-1 for Cr, Ni, As, Cd, Hg, and Pb, respectively. The trace elements in ZBMEO differed significantly when different extraction technologies were used. The study revealed that the contents of the toxic elements As, Cd, Hg, and Pb were extremely low, and hence they are unlikely to pose a health risk following ZBMEO ingestion. Graphical abstract The working mechanism of sample analysis by ICP-MS/MS.

Determination of tetrabromobisphenol-A/S and their main derivatives in water samples by high performance liquid chromatography coupled with inductively coupled plasma tandem mass spectrometry

As the most widely used brominated flame retardants (BFRs), Tetrabromobisphenol-A (TBBPA) as well as its alternative Tetrabromobisphenol-S (TBBPS) and their derivatives have raised wide concerns due to their adverse effects on human health and hence the sensitive detection of those BFRs was urgently needed. Herein, a novel analytical method based on high-performance liquid chromatography (HPLC) coupled with inductively coupled plasma tandem mass spectrometry (ICP-MS/MS) has been developed for the determination of TBBPA/S and their derivatives, including TBBPA-bis(2-hydroxyethyl ether) (TBBPA-BHEE), TBBPA-bis(allylether) (TBBPA-BAE), TBBPA-bis(glycidyl ether) (TBBPA-BGE), TBBPA-bis(2,3-dibromopropyl ether) (TBBPA-BDBPE) and TBBPS-bis(2,3-dibromopropyl ether) (TBBPS-BDBPE) in water samples. After optimization, the TBBPA/S and their derivatives, especially the TBBPA-BAE and TBBPA-BDBPE were simultaneously and sensitively quantified by determination of bromine (m/z=79) by using the ICP-MS. The instrument limits of detection (LODs) for the TBBPA, TBBPA-BHEE, TBBPA-BGE, TBBPA-BAE, TBBPA-BDBPE, TBBPS and TBBPS-BDBPE were determined to be 0.12, 0.14, 0.19, 0.14, 0.12, 0.17 and 0.13μgL^-1, respectively, which was close to or much better than the reported methods. The relative standard deviations (RSDs, n=5) of peak area and retention time were better than 2.2% and 0.2% for intra-day analysis, indicating good repeatability and high precision. The proposed method had been successfully applied for the analysis of TBBPA/S and their derivatives in water samples with satisfactory recoveries (67.7%-113%).