Antonio Bazo Sánchez

@article{,

title = {Discrete Entity Analysis via Microwave-Induced Nitrogen Plasma–Mass Spectrometry in Single-Event Mode},

author = {Ana Rua-Ibarz and Flávio V. Nakadi and Eduardo Bolea-Fernandez and Antonio Bazo and Beatrice Battistella and Anna Matiushkina and Ute Resch-Genger and Carlos Abad and Martín Resano},

url = {https://doi.org/10.1021/acs.analchem.5c04341},

doi = {10.1021/acs.analchem.5c04341},

year  = {2025},

date = {2025-10-14},

urldate = {2025-10-14},

journal = {Analytical Chemistry},

volume = {0},

number = {0},

pages = {null},

abstract = {In this work, single-event microwave-induced nitrogen plasma–mass spectrometry (single-event MINP-MS) was evaluated for the first time for the analysis of discrete entities such as nanoparticles, biological cells, and microplastics. Nitrogen (N2) effectively overcomes Ar-based polyatomic interferences, enabling (ultra)trace element determination of Fe and Se using their most abundant isotopes, 56Fe (91.66%) and 80Se (49.82%). Iron oxide nanoparticles (Fe2O3 NPs) ranging from 20 to 70 nm were accurately characterized, with excellent agreement with established sizing techniques, such as transmission electron microscopy (TEM) and dynamic light scattering (DLS). A limit of detection (LoD) of 8.6 ag for Fe─equivalent to an LoDsize of 19 nm for Fe2O3─was achieved, which is significantly lower than recent values reported for high-end quadrupole-based ICP-MS. Selenium nanoparticles (SeNPs) of 150 and 250 nm were also accurately characterized, without the N2-based plasma experiencing issues handling relatively large metallic NPs (linearity, R2 = 0.9994). Se-enriched yeast cells (SELM-1 certified reference material) were successfully analyzed via single-cell MINP-MS using external calibration based on SeNPs and a transport efficiency-independent approach. In addition, 2–3 μm polystyrene (PS) and polytetrafluoroethylene (PTFE) were accurately sized by monitoring 12C+, confirming the method’s suitability for handling micrometer-sized polymeric materials (microplastics). The average duration of individual events (680 ± 160 μs) suggests that the digestion of individual entities in N2-based plasmas is comparable to that in Ar-based plasmas. These results open new avenues for this instrumentation as an alternative to ICP ionization sources, also in the context of discrete entity analysis.},

note = {PMID: 41084806},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{nokey,

title = {Ions with Ions, Entities with Entities: A Proof-of-Concept Study Using the SELM-1 Yeast Certified Reference Material for Intra- and Extracellular Se Quantification via Single-Cell ICP-Mass Spectrometry},

author = {Antonio Bazo and Eduardo Bolea-Fernandez and Ana Rua-Ibarz and Maite Aramendía and Martín Resano},

url = {https://pubs.acs.org/doi/10.1021/acs.analchem.5c01588},

doi = {https://doi.org/10.1021/acs.analchem.5c01588},

issn = {1520-6882},

year  = {2025},

date = {2025-06-07},

urldate = {2025-06-07},

journal = {Anal. Chem.},

abstract = {In this work, two novel nanoparticle (NP)-based calibration strategies, external calibration and a relative method, have been explored for single-cell ICP-mass spectrometry (SC-ICP-MS) analysis. The fundamental principle of these methods is to rely on individual entities (well-characterized NPs of the target analyte) for calibration rather than on ionic standard solutions. The performance of the NP-based calibration approaches has been compared to that of the reference method (particle size with AuNP standards). In addition to the intracellular Se content (mass per individual cell), the extracellular Se (dissolved fraction) was also determined directly and simultaneously using the average background from the SC-ICP-MS time-resolved signal. The figures-of-merit of the methods developed have been evaluated by relying on the analysis of the SELM-1 cell-certified reference material, consisting of Se-enriched yeast cells, and certified for its total Se content (intracellular + extracellular Se). All methods successfully determined the Se elemental contents, but an improvement in accuracy and precision was observed for the NP-based methods compared to the reference one. Furthermore, the NP-based methods were found to be less time-consuming, more straightforward, and more user-friendly in terms of calculations. These results open new avenues for calibration in quantitative SC-ICP-MS analysis and call for a fundamental change in the methodology, where the determination of ionic contents is based on the use of ionic standard solutions for calibration, while the determination of elemental contents in discrete micro/nanoentities, such as cells, should ideally be based on calibration using standard entities, thus avoiding the need to calculate a transport efficiency coefficient.},

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pubstate = {published},

tppubtype = {article}

}

@article{D5JA00253B,

title = {A novel particle mass calibration strategy for the quantification of AuNPs in single cancer cells via laser ablation ICP-mass spectrometry. A case study},

author = {Antonio Bazo and Eduardo Bolea-Fernandez and Kharmen Billimoria and Ana Rua-Ibarz and Maite Aramendía and Paula Menero-Valdés and Jack Morley and Sara Neves and Armando Sánchez-Cachero and Heidi Goenaga-Infante and Martín Resano},

url = {http://dx.doi.org/10.1039/D5JA00253B},

doi = {10.1039/D5JA00253B},

year  = {2025},

date = {2025-01-01},

urldate = {2025-01-01},

journal = {J. Anal. At. Spectrom.},

pages = {-},

publisher = {The Royal Society of Chemistry},

abstract = {Laser ablation ICP-mass spectrometry (LA-ICP-MS) has developed as a powerful tool for elemental quantitative analysis of individual cells, assuring that the content of each cell is analyzed individually. However, this technique is still limited by the difficulties associated with calibration using solid standards. This work proposes a particle mass calibration strategy that is independent of both the properties and thickness of the gelatin films used for calibration, overcoming a significant drawback of previously established methods. The fundamental principle of this strategy relies on the individual ablation of nanoparticles (NPs) of well-characterized size that are embedded in the films, so that their mass can be directly used for calibration without the need to calculate their exact concentration within the gelatin. The performance of the newly developed method was compared to that of the previously reported approaches (ionic and particle number calibration) in terms of linearity and homogeneity between different films prepared from the same gelatin solution. As a case study, the three calibration strategies were used for the quantitative analysis of HeLa cancer cells exposed to AuNPs. In parallel, in-suspension single-cell (SC) ICP-MS Au data were obtained and used as reference for comparison with the three LA-SC-ICP-MS strategies. The results obtained with the novel particle mass approach demonstrated better accuracy and repeatability over three different working sessions, addressing key limitations and providing a robust and reliable method for quantitative LA-SC-ICP-MS analysis. The particle mass method holds promise for quantitative LA-ICP-MS analysis of samples beyond NP-exposed cells, such as biological tissues.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{BAZO2025344694,

title = {Improving detection and figures of merit in single-particle inductively coupled plasma-mass spectrometry via transient event heights},

author = {Antonio Bazo and Lorién López-Villellas and Matilde Mataloni and Eduardo Bolea-Fernandez and Ana Rua-Ibarz and Marco Grotti and Maite Aramendía and Martín Resano},

url = {https://www.sciencedirect.com/science/article/pii/S0003267025010888},

doi = {https://doi.org/10.1016/j.aca.2025.344694},

issn = {0003-2670},

year  = {2025},

date = {2025-01-01},

urldate = {2025-01-01},

journal = {Analytica Chimica Acta},

volume = {1378},

pages = {344694},

abstract = {Background 

Single-particle inductively coupled plasma-mass spectrometry (SP-ICP-MS) is a powerful method for characterizing micro- and nanoparticulate materials. The technique primarily relies on the linear relationship between the integrated intensities of individual events (peak areas) and the analyte mass, though transit times (peak widths) have also been used for quantitative purposes. This work (1) evaluates the potential of using peak heights as analytical signals in SP-ICP-MS, (2) introduces a new method for determining peak heights, and (3) explores scenarios in which peak height offers added value over the commonly used SP-ICP-MS signals. 

Results 

A new method was proposed to estimate peak height values in SP-ICP-MS accurately. The cumulative intensity across consecutive dwell times was modeled using a third-degree polynomial, from which the adjusted peak height was derived. This approach reduces the uncertainty associated with using raw maximum intensity values, yielding NP distributions comparable to those obtained via integrated intensities. The effect of dwell time on peak height was also evaluated. An optimal range (50 μs–200 μs) was identified, where a linear relationship was observed between the peak height and the square of the NP diameter. Within this range, peak height showed the lowest bias when characterizing smaller NPs, indicating the potential to improve the limit of quantification (LoQ). Additionally, peak heights proved helpful in determining the limit of detection (LoD) and setting appropriate threshold values for data processing, thereby helping to flag incorrect resultsand addressing a challenge in SP-ICP-MS analysis. 

Significance 

This is the first study to evaluate peak height as an analytical signal in SP-ICP-MS. The results highlight its advantages in specific applications, such as sizing NPs near the LoD, and in supporting the more reliable use of other signals, such as peak areas, by helping to identify incorrect threshold selection that could lead to biased distributions. Finally, monitoring peak heights allows for a more realistic and assumption-free determination of the LoD.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{BAZO2024343305,

title = {Intensity- and time-based strategies for micro/nano-sizing via single-particle ICP-mass spectrometry: A comparative assessment using Au and SiO2 as model particles},

author = {Antonio Bazo and Eduardo Bolea-Fernandez and Ana Rua-Ibarz and Maite Aramendía and Martín Resano},

url = {https://www.sciencedirect.com/science/article/pii/S0003267024011061},

doi = {https://doi.org/10.1016/j.aca.2024.343305},

issn = {0003-2670},

year  = {2024},

date = {2024-01-01},

urldate = {2024-01-01},

journal = {Analytica Chimica Acta},

volume = {1331},

pages = {343305},

abstract = {Background 

Single-particle ICP-mass spectrometry (SP-ICP-MS) is a powerful method for micro/nano-particle (MNP) sizing. Despite the outstanding evolution of the technique in the last decade, most studies still rely on traditional approaches based on (1) the use of integrated intensity as the analytical signal and (2) the calculation of the transport efficiency (TE). However, the increasing availability of MNP standards and advancements in hardware and software have unveiled new venues for MNP sizing, including TE-independent and time-based approaches. This work systematically examines these different methodologies to identify and summarize their strengths and weaknesses, thus helping to determine their preferred application areas. 

Results 

Different SP-ICP-MS methods for MNP sizing were assessed using AuNPs (20–70 nm) and SiO2MNPs (100–1000 nm). Among TE-dependent approaches, the particle frequency method was characterized by larger uncertainties than the particle size method. The results of the latter were dependent on the appropriate selection of the reference MNP, making the use of multiple reference MNPs recommended. TE-independent methods were based on external (linear and polynomial) calibrations and a relative approach. These methods exhibited the lowest uncertainties of all the strategies evaluated. External calibrations benefited from simpler calculations, but their application could be hindered by a lack of reference MNPs within the desired size range or by the need for interpolations outside the calibration range. Finally, transit time signals are directly proportional to the MNP size rather than its mass. The time-based method demonstrated adequate performance for sizing AuNPs but failed when sizing the largest SiO2MNPs (1000 nm). 

Significance and novelty 

This work provides further insights into the application of different SP-ICP-MS methodologies for MNP sizing. Both TE-independent approaches and the monitoring of the transit time as the analytical signal are underused strategies; in this context, a Python script was developed for accurate transit time measurement. After 20 years of development, a quantitative comparison of the different methodologies, including the most novel approaches, is deemed necessary for further growth on solid theoretical ground.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}