The design and characterization of a High-Performance Single-Particle Aerosol Mass Spectrometer (HP-SPAMS)

Du, Xubing; Xie, Qinhui; Huang, Qing; Li, Xuan; Yang, Junlin; Hou, Zhihui; Wang, Jingjing; Li, Xue; Zhou, Zhen; Huang, Zhengxu; Gao, Wei; Li, Lei

doi:https://doi.org/10.5194/egusphere-2022-872

Preprints

https://doi.org/10.5194/egusphere-2022-872

Preprints

01 Nov 2022

| 01 Nov 2022

The design and characterization of a High-Performance Single-Particle Aerosol Mass Spectrometer (HP-SPAMS)

Xubing Du, Qinhui Xie, Qing Huang, Xuan Li, Junlin Yang, Zhihui Hou, Jingjing Wang, Xue Li, Zhen Zhou, Zhengxu Huang, Wei Gao, and Lei Li

Abstract. This study describes a high-performance single-particle mass spectrometry (HP-SPAMS) design in detail. The comprehensive improvements of the injection system, optical sizing system, mass spectrometry, and data acquisition system have improved particle detection efficiency and chemical analysis. The combination of an aerodynamic particle concentrator (APC) system and a wide range of aerodynamic lenses (ADLs) enables the concentration of particles in the 100–5000 nm range by a factor of 3–5 times. The ion delayed exaction technology of bipolar time-of-flight mass spectrometry improves the mass resolution by 2~3 times, allowing the differentiation of multiple homogeneous masses of different substances. Moreover, the 4-channel data acquisition technology greatly enhances the dynamic range of mass spectrometry. The as-improved HP-SPAMS enhances the overall capability of the instrument in terms of particle detection number and detection efficiency. Moreover, it improves accuracy and sensitivity for component identification of individual particles.

The experimental performance of HP-SPAMS shows that the sizing detection efficiency of polystyrene latex microspheres is almost 70 %–100 % in the range of 300–3000 nm. Compared to the previous SPAMS, HP-SPAMS has a larger inlet flow rate, detection efficiency, and higher laser frequency, which makes HP-SPAMS increase the effective number of particles detected in the air by 47.8 times and improve the temporal resolution of detection. For the analysis of individual particles, the HP-SPAMS's improved resolution helps distinguish between most organic fragment ions and metal ions and facilitates the analysis of complex aerosol particles. For the analysis of individual particles, the increased resolution of the HP-SPAMS contributes to the differentiation of most organic fragment ions and metal ions and facilitates the evaluation of complex aerosol particles. In the case of atmospheric lead-containing particles, for example, HP-SPAMS can completely differentiate the isotopes of lead elements and the number of lead-containing particles is 145 times higher than that detected by SPAMS. The outstanding detection efficiency and chemical analysis capability of HP-SPAMS will be of great importance for low concentration aerosol detection and complex aerosol component analysis.

Received: 02 Sep 2022 – Discussion started: 01 Nov 2022

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Journal article(s) based on this preprint

13 Feb 2024

Development and characterization of a high-performance single-particle aerosol mass spectrometer (HP-SPAMS)

Xubing Du, Qinhui Xie, Qing Huang, Xuan Li, Junlin Yang, Zhihui Hou, Jingjing Wang, Xue Li, Zhen Zhou, Zhengxu Huang, Wei Gao, and Lei Li

Atmos. Meas. Tech., 17, 1037–1050, https://doi.org/10.5194/amt-17-1037-2024,https://doi.org/10.5194/amt-17-1037-2024, 2024

Short summary

Xubing Du, Qinhui Xie, Qing Huang, Xuan Li, Junlin Yang, Zhihui Hou, Jingjing Wang, Xue Li, Zhen Zhou, Zhengxu Huang, Wei Gao, and Lei Li

Interactive discussion

Status: closed

RC1:
'Comment on egusphere-2022-872', Anonymous Referee #2, 13 Nov 2022

Review of Du et al., The design and characterization of a high-performance single-particle aerosol mass spectrometer (HP-SPAMS)

This manuscript is, as the title implies, a technical description of a single particle mass spectrometer. This is a commercial instrument, but the description is primarily technical and does not feel too much like an advertisement. It falls reasonably into the type of paper that describes the performance of a commercial instrument.

The technical specifications are in some respects quite impressive. This instrument is, for example, significantly better than the ATOFMS sold some years ago in the US by TSI, Inc. The writing is good and the references are balanced. The manuscript should be publishable with minor revisions.

One general change that would benefit the manuscript is to do fewer comparisons to the previous SPAMS instrument developed by the same group and emphasize absolute performance more. The authors are justifiably proud of their improvements, but the eventual paper should be presented for a general audience of all users of single particle mass spectrometers, not just those who own an older instrument developed/sold by the same authors. An example of something to de-emphasize or delete: “the number of lead-containing particles is 145 times higher than that detected by SPAMS” (abstract). An example of something to emphasize more: the comparison in Figure 4 of the detection efficiency of various kinds of particles, presumable due to spherical or non-spherical shapes. This is a very useful comparison between types of particles. These are just examples: there are probably dozens of places in the manuscript where the comparisons to the older SPAMS could be reduced. A few are OK, but only a few.

One important technical detail that is missing is a list of the spot sizes of the detection and ionization lasers. One cannot interpret the performance of the aerodynamic lens without knowing how big of a target is provided by the detection lasers beams. And one needs the ionization laser spot size to know the fluence available to ionize particles.

I found the discussion of the aerodynamic concentrator incorporated into the aerodynamic focusing inlet to be confusing. Maybe because it is incorporated into the inlet, it was never clear to me what the baseline was for its performance. In the abstract it says that it “enables concentration… but a factor of 3-5 times”. Compared to what? And then in section 3.1 I was not clear in the discussion of detection efficiency what the maximum detection efficiency should be. Should it be 100%? Or perhaps the maximum should be 300 to 500%, because the best possible performance would be 100%, but the concentrator would then multiply that by 3 to 5? I think a clear definition of how the baseline is defined would solve these. By the way, incorporating the aerosol concentrator into the inlet instead of having a separate concentrator upstream looks like a clever idea with several advantages.

It would be interesting to see a few spectra on a logarithmic scale, perhaps in supplemental material, to see the dynamic range from the high range/low range digitization and whether or not that induces any artifacts.

Near line 104, the pressure would be helpful as well as the orifice diameters. I think the symbol/line labels in Figure 5 may be incorrect.

Citation: https://doi.org/10.5194/egusphere-2022-872-RC1
- AC1: 'Reply on RC1', Lei Li, 04 Jan 2023
  
  We thank the reviewers for their valuable comments on the manuscript. We have responded individually (see supplement) and have made corrections in the manuscript in the corresponding places. If you have any questions, please contact us.
  
  Thank you and best regards.
  
  Citation: https://doi.org/10.5194/egusphere-2022-872-AC1
RC2:
'Review of the manuscript egusphere-2022-872 with the title: 'The design and characterization of a High-Performance Single-Particle Aerosol Mass Spectrometer (HP-SPAMS)' by Du et al.', Anonymous Referee #1, 22 Nov 2022

The manuscript by Du et al. entitled 'The design and characterization of a High-Performance Single-Particle Aerosol Mass Spectrometer (HP-SPAMS)' describes the development and improvement of single particle mass spectrometry in the inlet system, higher detection efficiency and hit rate, and greatly improved mass resolution in the analyzer. The results shown here impressively demonstrate the possibilities of this technology and clearly show advantages and actual scientific questions, which will be addressed here.

However, questions remain and should be discussed and improved before publication. Overall, this manuscript should be accepted for publication after improvements focused on the specific comments below.

More general comments:

- Add spot sizes for ionization and sizing lasers.

- Add energies of ionization lasers of SPAMS and HP-SPAMS because it highly influences the hitrate.

- Define 'hitrate' (' of mass specs in relation to # at PMT2 ??)

- The detection efficiency is given in % -> in relation to what? How is the higher repetition rate of the newer system and its timing electronics taken into account?

- Figure 4: PMT2 is of course always lower in signal number and therefore detection efficiency, why is the detection efficiency in (d) with all errorbars the same as for PMT1? This should at least show a difference due to the divergence of the particle beam.

- Figure 4: Please add data from CPC for better understanding of the detection efficincy and normalize to to sample volume, so that the two systems can be better compared.

- Figure 6: please also add a plot as the third one for the (non-HP) SPAMS.

- Figure 7: right side y-axis update to #/time (24 h ??)

- Figure 7: normalize to sample flow (ml/ccm^3 -> like SMPS)

Line 95: Why is this size used? Is there the possibility to use also even larger sized orifice with higher flows and even more particles? Is the flow through the aerodynamic lens also higher or is it the same as in the older version?

Line 176: Not in every case the number of particles is 10 times as high, for NaCl particles the difference is sometimes only about one third. Furthermore, as shown in Figure 4, the difference is size and particle type dependent. Please revise formulation more precisely and elaborate.

Line 183: Compared to what number? PMT2 or CPC? Please add information on count number of CPC 1/ccm^3

Line 183/184: Both are decreasing with smaller particle sizes, please revise formulation more precisely and elaborate.

Line 209: Should be: ...SMPS, HP-SPAMS, and SPAMS respectivley... change word order

Line 210: This is a total value not taking into account the sample flow rate, please add normalized values.

All in all, the first paragraph in the results section (lines 159 - 194) is very confusing and should be fundamentally revised. The comparisons with the previous and older measurement system are misleading in this form, since no laser energies and spot sizes are given and the results have not been normalized. This will make the difference between the systems considerably smaller, nevertheless this is a very good and useful improvement of the technology.

Citation: https://doi.org/10.5194/egusphere-2022-872-RC2
- AC2: 'Reply on RC2', Lei Li, 04 Jan 2023
  
  We thank the reviewers for their valuable comments on the manuscript. We have responded individually (see supplement) and have made corrections in the manuscript in the corresponding places. If you have any questions, please contact us.
  
  Thank you and best regards.
  
  Citation: https://doi.org/10.5194/egusphere-2022-872-AC2

Interactive discussion

Status: closed

RC1:
'Comment on egusphere-2022-872', Anonymous Referee #2, 13 Nov 2022

Review of Du et al., The design and characterization of a high-performance single-particle aerosol mass spectrometer (HP-SPAMS)

This manuscript is, as the title implies, a technical description of a single particle mass spectrometer. This is a commercial instrument, but the description is primarily technical and does not feel too much like an advertisement. It falls reasonably into the type of paper that describes the performance of a commercial instrument.

The technical specifications are in some respects quite impressive. This instrument is, for example, significantly better than the ATOFMS sold some years ago in the US by TSI, Inc. The writing is good and the references are balanced. The manuscript should be publishable with minor revisions.

One general change that would benefit the manuscript is to do fewer comparisons to the previous SPAMS instrument developed by the same group and emphasize absolute performance more. The authors are justifiably proud of their improvements, but the eventual paper should be presented for a general audience of all users of single particle mass spectrometers, not just those who own an older instrument developed/sold by the same authors. An example of something to de-emphasize or delete: “the number of lead-containing particles is 145 times higher than that detected by SPAMS” (abstract). An example of something to emphasize more: the comparison in Figure 4 of the detection efficiency of various kinds of particles, presumable due to spherical or non-spherical shapes. This is a very useful comparison between types of particles. These are just examples: there are probably dozens of places in the manuscript where the comparisons to the older SPAMS could be reduced. A few are OK, but only a few.

One important technical detail that is missing is a list of the spot sizes of the detection and ionization lasers. One cannot interpret the performance of the aerodynamic lens without knowing how big of a target is provided by the detection lasers beams. And one needs the ionization laser spot size to know the fluence available to ionize particles.

I found the discussion of the aerodynamic concentrator incorporated into the aerodynamic focusing inlet to be confusing. Maybe because it is incorporated into the inlet, it was never clear to me what the baseline was for its performance. In the abstract it says that it “enables concentration… but a factor of 3-5 times”. Compared to what? And then in section 3.1 I was not clear in the discussion of detection efficiency what the maximum detection efficiency should be. Should it be 100%? Or perhaps the maximum should be 300 to 500%, because the best possible performance would be 100%, but the concentrator would then multiply that by 3 to 5? I think a clear definition of how the baseline is defined would solve these. By the way, incorporating the aerosol concentrator into the inlet instead of having a separate concentrator upstream looks like a clever idea with several advantages.

It would be interesting to see a few spectra on a logarithmic scale, perhaps in supplemental material, to see the dynamic range from the high range/low range digitization and whether or not that induces any artifacts.

Near line 104, the pressure would be helpful as well as the orifice diameters. I think the symbol/line labels in Figure 5 may be incorrect.

Citation: https://doi.org/10.5194/egusphere-2022-872-RC1
- AC1: 'Reply on RC1', Lei Li, 04 Jan 2023
  
  We thank the reviewers for their valuable comments on the manuscript. We have responded individually (see supplement) and have made corrections in the manuscript in the corresponding places. If you have any questions, please contact us.
  
  Thank you and best regards.
  
  Citation: https://doi.org/10.5194/egusphere-2022-872-AC1
RC2:
'Review of the manuscript egusphere-2022-872 with the title: 'The design and characterization of a High-Performance Single-Particle Aerosol Mass Spectrometer (HP-SPAMS)' by Du et al.', Anonymous Referee #1, 22 Nov 2022

The manuscript by Du et al. entitled 'The design and characterization of a High-Performance Single-Particle Aerosol Mass Spectrometer (HP-SPAMS)' describes the development and improvement of single particle mass spectrometry in the inlet system, higher detection efficiency and hit rate, and greatly improved mass resolution in the analyzer. The results shown here impressively demonstrate the possibilities of this technology and clearly show advantages and actual scientific questions, which will be addressed here.

However, questions remain and should be discussed and improved before publication. Overall, this manuscript should be accepted for publication after improvements focused on the specific comments below.

More general comments:

- Add spot sizes for ionization and sizing lasers.

- Add energies of ionization lasers of SPAMS and HP-SPAMS because it highly influences the hitrate.

- Define 'hitrate' (' of mass specs in relation to # at PMT2 ??)

- The detection efficiency is given in % -> in relation to what? How is the higher repetition rate of the newer system and its timing electronics taken into account?

- Figure 4: PMT2 is of course always lower in signal number and therefore detection efficiency, why is the detection efficiency in (d) with all errorbars the same as for PMT1? This should at least show a difference due to the divergence of the particle beam.

- Figure 4: Please add data from CPC for better understanding of the detection efficincy and normalize to to sample volume, so that the two systems can be better compared.

- Figure 6: please also add a plot as the third one for the (non-HP) SPAMS.

- Figure 7: right side y-axis update to #/time (24 h ??)

- Figure 7: normalize to sample flow (ml/ccm^3 -> like SMPS)

Line 95: Why is this size used? Is there the possibility to use also even larger sized orifice with higher flows and even more particles? Is the flow through the aerodynamic lens also higher or is it the same as in the older version?

Line 176: Not in every case the number of particles is 10 times as high, for NaCl particles the difference is sometimes only about one third. Furthermore, as shown in Figure 4, the difference is size and particle type dependent. Please revise formulation more precisely and elaborate.

Line 183: Compared to what number? PMT2 or CPC? Please add information on count number of CPC 1/ccm^3

Line 183/184: Both are decreasing with smaller particle sizes, please revise formulation more precisely and elaborate.

Line 209: Should be: ...SMPS, HP-SPAMS, and SPAMS respectivley... change word order

Line 210: This is a total value not taking into account the sample flow rate, please add normalized values.

All in all, the first paragraph in the results section (lines 159 - 194) is very confusing and should be fundamentally revised. The comparisons with the previous and older measurement system are misleading in this form, since no laser energies and spot sizes are given and the results have not been normalized. This will make the difference between the systems considerably smaller, nevertheless this is a very good and useful improvement of the technology.

Citation: https://doi.org/10.5194/egusphere-2022-872-RC2
- AC2: 'Reply on RC2', Lei Li, 04 Jan 2023
  
  We thank the reviewers for their valuable comments on the manuscript. We have responded individually (see supplement) and have made corrections in the manuscript in the corresponding places. If you have any questions, please contact us.
  
  Thank you and best regards.
  
  Citation: https://doi.org/10.5194/egusphere-2022-872-AC2

Peer review completion

AR: Author's response | RR: Referee report | ED: Editor decision | EF: Editorial file upload

AR by Lei Li on behalf of the Authors (04 Jan 2023) Author's response Author's tracked changes Manuscript

ED: Referee Nomination & Report Request started (16 Jan 2023) by Lucia Mona

RR by Anonymous Referee #3 (24 Mar 2023)

RR by Anonymous Referee #4 (08 May 2023)

Suggestions for revision or reasons for rejection

This manuscript describes the comparison of the performance between the “High-Performance” HP-SPAMS and the prior version (SPAMS). While limited design details are provided, data is included for the scattering efficiency and hit fraction vs size for both instruments, as well as mass spectral resolution. Yet, there are many general statements in the manuscript for which details/data are not provided, or for which the authors cite a manuscript for a different single-particle mass spectrometer. Line numbers referred to in this review correspond to the track changes version of the manuscript.

As noted in the previous reviews, details are missing from the Section 2 description of the HP-SPAMS. Detailed descriptions of the specific parts that we changed (including both the previous and current parts) are needed. Some details were added in the revision, and this is helpful. Yet, it still is often not clear what exactly changed between the two versions of the instrument, and most of the statements are vague/general. The improvements made to the instrument appear to include adding an aerodynamic particle concentrator system, applying delayed ion extraction, using a high frequency YAG laser, and adding four-channel data acquisition.

The authors have previously published focused manuscripts about the design and characterization of the two main improvements to instrument:
1) Delayed ion extraction:
- Li et al. 2018, J. Am. Soc. Mass Spec., “Improvement in the Mass Resolution of Single Particle Mass Spectrometry using Delayed Ion Extraction”
- Chen et al. 2020, Atmos. Meas. Tech., “Increase of the particle hit rate in a laser single-particle mass spectrometer by pulse delayed extraction technology”
2) Improved aerosol inlet:
- Du et al. 2023, Atmosphere, “Design and simulation of aerosol inlet system for particulate matter with a wide size range”
While Li et al. (2018) and Chen et al. (2020) are cited, it is not clear that that details of the design and previous characterization can be found in those manuscripts, and it would be very helpful for the current manuscript for this to be made clear in Section 2. Further, these previous manuscripts provided data on hit %s and mass spectral resolution that could be used in the current manuscript to comment on how much each improvement made a difference to the overall performance of the HP-SPAMS.

Based on these previous manuscripts, the authors’ main goal in the current manuscript appears to be the characterization of the full integrated system (HP-SPAMS) and comparison to the original SPAMS, rather than a detailed description of the “design”, which is lacking, as noted above. The manuscript title needs to be revised to indicate this.

Several of the improvements made to this instrument have been previously described for other single-particle mass spectrometers, but this is not clear in the manuscript. This comment relates to the inadequate response of the authors to the previous requests for additional comparisons to non-SPAMS instruments. I provide examples (not meant to be comprehensive – the authors need to do a literature search) here. Delayed pulse extraction is used by several single-particle mass specs: miniSPLAT (Zelenyuk et al., 2015, J. Am. Soc. Mass Spec.), BAMS (Czerwieniec et al. 2005, J. Am. Soc. Mass Spec.), SPASS (Erdmann et al. 2005, Aerosol Sci. Technol.), LAMPAS-2 (Costa Vera et al. 2005, Rapid. Commun. Mass Spectrom.), ALABAMA (Clemen et al. 2020, AMT). Four-channel data acquisition is used on other single-particle mass spectrometers, including the ALABAMA (Brands et al. 2011, Aerosol Sci. Technol.) and ATOFMS (Pratt et al. 2009, Analytical Chem.). The 100 Hz Nd:YAG laser (Centurion, Quantel) is used on the Univ. of Michigan ATOFMS (Gunsch et al. 2017, Atmos. Chem. Phys.).

The authors should cite Su et al. (2023, Atmos. Environ., “Analysis performance of single particle aerosol mass spectrometer for accurate sizing and isotopic analysis of individual particles”) as an additional study that characterized the SPAMS. In particular, that study also reported the accuracy of the 208Pb/206Pb ratio to be closer than observed for the SPAMS in the current work (Figure 10 in the current manuscript). This comparison should be addressed. In addition, it is not only the correlation that matters (discussed on Line 291 and shown in Figure 10), but also the comparison to the theoretical isotope ratio, which is not provided in the current manuscript.

The authors state on Lines 38-39: “However, the limitations of current mass spectrometry (MS) detection capabilities render it not well suited for analyzing complex aerosol components in low concentration environments.” This is not accurate, as there have been single-particle MS measurements in the Arctic, free troposphere, and stratosphere – all low concentration environments. Only two references are cited in the next sentence, but there are many papers – especially using PALMS, SPLAT, and ATOFMS – that have shown highly successful data obtained in these environments.

On Lines 42-43 the authors refer to needing long-time collection and changing mixing state, but this is confusing because SPMS is, by definition, a real-time analysis method, such that long-time collection is not possible. Further, Pratt et al. (2009, Analytical. Chem.) shows aerosol mixing state with 2 and 4-min resolution. Therefore, it is clear that the authors’ statement needs revision for multiple reasons.

The authors state on Lines 44-45: “…the poor mass resolution and detection sensitivity of SPMS make it difficult to obtain an accurate analysis of aerosols. (Pratt et al. 2009; Zelenyuk et al. 2009)” Yet, neither of these papers shows this, and it is not an accurate statement, as there are many publications, especially using ATOFMS, SPLAT, and PALMS showing accurate, quantitative analysis by SPMS.

On Lines 56-57, the authors state “The particles that could be transmitted to the instrument are not entirely measurable, which could be related to the particle sizing efficiency and ionization probability”, with no reference. This statement is confusing, as many published single-particle mass spec characterization studies have quantified transmission through multiple methods.

On Lines 80-81, the authors state “Although there are many studies to improve one aspect of the performance of SPMS, the instrument’s overall performance is insufficient.” Yet, there have been many improvements to single-particle mass spec instruments over the past three decades, with great success, and many high-performing instruments exist. Please revise this statement to refer to the need to improve the SPAMS itself. Further, this statement makes it clear that a paragraph about the SPAMS itself is needed in Section 1, as the main goal of the current work is to compare the SPAMS and HP-SPAMS.

Line 94: Provide the height with the inlet included as well.

Line 95: Provide the actual, rather than approximate weight.

On Lines 101-102, it is stated “…most particles have entered the separation cone.” Please provide data, and quantify “most”.

Lines 106-107 state “…could theoretically transport particles in the range of 100-5000 nm.” Where is the theoretical transmission curve data? Further, scattering efficiency data appears to only go out to ~2-3 um in Figure 4.

Lines 112-113 state “Compared to the SPAMS, increasing the laser power enhanced the intensity of the scattered light from the particles.” Please state how much the laser power was increased by, as well as provide data comparing the scattered light.

Lines 114-115 state “the background noise level was effectively reduced, and the detection capability for small-size particles was improved.” This is referred to again on Lines 190-192 with the same phrasing. How much was the noise level reduced? What size is “small”? How much was the detection of these “small-size” particles improved? Provide quantitative data.

Line 125 states that “laser beam homogenization” is employed, but I could not find a description of how this was done. The reference (Steele et al. 2005) is to a different single-particle mass spectrometer. Please clarify how this was set-up for the HP-SPAMS and that is an improvement over the SPAMS. Also, it is confusing when, on Lines 212-213, the authors refer to a “non-uniform Gaussian beam”, suggesting that laser beam homogenization may not have been done? But, then Lines 255-256 mention a “uniform laser beam”. So, the laser set-up is not clear.

Lines 161-162: It is stated “To compare the detection capability of the instrument at low concentrations, the fraction of the samples fed by the SPAMS and HP-SPAMS was diluted by 40 times…”. Please provide the initial and diluted number concentrations, to provide important context for what is meant by “low”.

Lines 189-190: Please provide the current and previous critical orifice sizes for context. The reference here to Cahill et al. (2014) is for a different single-particle mass spectrometer.

Lines 210-212: Here it is stated that particles of different composition require different laser energy thresholds, but hit % data is only provided for the ambient data (Figure 5) and is not provided for the four different particle types shown in Figure 4, for which chemically-dependent scattering efficiency data are shown. Add hit % data that corresponds to the lab scattering data in Figure 4, as presumably the entire instrument was running during the experiment, such that hit data should be available. Increase the discussion of chemical biases here, including the role of the low chosen laser power (0.5 mJ).

Report the HP-SPAMS data in terms of number concentration, rather than #/min, in Figure 6. Then in the text, compare to the SMPS number concentration in the same size range, to the HP-SPAMS number concentration, to enable a quantitative comparison. This is important because the authors are claiming very high scattering and detection efficiencies in Figures 4-5, and so, a quantitative comparison is needed here. Currently only correlation analysis was completed, at the bottom of page 7. It would also be more meaningful to examine the correlation with the SMPS concentration in the same size range where the HP-SPAMS has high scattering and detection efficiency. The scatter and hit rates of the instrument are also important to discuss to provide context for the instrument performance.

Line 235-236: I could not find where these data are provided. Please clarify what is meant by “detect” (hit?), and provide data. Is this an average value or a maximum?

Lines 251-256: This discussion suggests that the ion transmission above m/z 100 improved, or the detection of these ions improved. Page 9 points to the data acquisition board change (signal amplification), which makes sense, but it isn’t mentioned here as a likely explanation.

Please clarify the sentence on Lines 278-279. Are the authors referring in the second part to the increased detection of ions > m/z 100? Also, how does this factor of 47.8 compare to the expected based on the data in Figures 4 and 5?

Additional comments:
- Line 16: By “multiple homogeneous masses”, do the authors mean “isobaric ions”?

- Line 28: Incomplete sentence

- Line 30: Change “outstanding” to “improved”

- Lines 33-34: Add reference to a review.

- Line 108: Is one laser used with its beam split, or are two lasers used? Please clarify.

- Lines 116-117: I assume that authors are referring to the calibration of velocity to dva. Please clarify the description here.

- Line 170: There appears to be a typo or English phrasing problem here.

- Line 205: I assume the authors mean “delayed ion extraction” rather than direct current extraction here?

- Line 238: Do the authors mean “nuclei” instead of “nuclear”?

- Lines 247-249: The authors should cite their previous paper here, as it showed a detailed analysis of this improved resolution and would support the statement made.

- Lines 260-261: This statement is confusing. Please clarify.

- Line 273: Please add “compared to the SPAMS” to provide context for the statement “more sensitive and accurate”.

- Line 290: Include figure # here.

- Lines 296-278: Clarify in this sentence that these improvements are compared to the SPAMS.

- Line 307: This states 0.97 corresponds to R-square, but Line 221 states it is a Pearson correlation (i.e. r, not r2). Which is correct?

- Lines 311-312: It is stated “although the sensitivity of HP-SPAMS to analyze individual particles cannot be quantified”. I don’t understand this statement, as this is what the authors have characterized in this paper.

- Line 314: Why is this not attributed to the ion detection, rather than the ion generation?

- Figure 4: Please change “Detection Efficiency” to “Scattering Efficiency” on the plot y axes to match the caption revision.

- Figure 6: Change “variation curve” to “temporal plot”. Is the DUST METER the PM2.5 concentration? Provide the size range of the SMPS for context. Explain the HP-SPAMS plot legend in the figure caption.

- Figure 9: The c & d x axis labels show “m/z (Da)”, but the figure caption suggests that the plot is showing m/z 206 relative peak area. Please fix.

- Line 496: Fix to 208Pb+ vs 206Pb+ to agree with figure.

Hide

RR by Anonymous Referee #5 (07 Jul 2023)

Suggestions for revision or reasons for rejection

General remarks:

I have received this manuscript in the revised version, after two reviewers commented on the manuscript. The comments of the reviewers have been addressed, but I did not check that in detail. I read the revised version without the tracked changes. Overall, the manuscript is informative and interesting. The improvements of the SPAMS are clearly shown and explained. However, I was surprised that after one round of revisions there are still so many (albeit relatively small) unclarities in the manuscript. I have listed these points below under “specific comments”.
Although I rate this as “minor revision”, I think that my comments listed below have to be considered before the manuscript can be published.

General comments:
I would prefer “detection efficiency“ over “scattering efficiency”. The expression “detection efficiency” has been used in previous SPMS papers (e.g. Clemen et al., 2020, Murphy 2007, Zelenyuk and Imre 2005). I have seen that you changed it during revision but I recommend to go back to “detection efficiency”.

Throughout the manuscript you use very often the word “could”. It is not clear to me if you mean this as past tense (referring to previous works) or as subjunctive (as in “it might be that…”). I suggest using “can” if you refer to processes and effects that are known to occur.

Specific comments: (line number refer to manuscript-version3):
Line 17 “The as-improved HP-SPAMS”: replace by “the improved HP-SPAMS”
Line 27: “In the case of atmospheric lead-containing particles”. This sentence is not complete
Line 31: remove “could”
Line 32-33: remove “an aerosol monitoring instrument” and add “e.g., “ before Murphy, 2007
Line 35: Move the full stop (colon) after the references, same in line 39, 41, 43, etc.
Line 47: change to “Cahill et al. (2014) developed…” and remove reference at end of the sentence
Line 54/55: I don’t understand the meaning of “The particles that could be transmitted to the instrument are not entirely measurable…”
Line 72-74: “To improve the accuracy of qualitative analysis, the identification of ions in the spectra is improved by organic fragment ions, metal oxide ions, and isotopic ions (Tan et al., 2002). However, these methods have reduced applicability for ions with mass deviations less than 1 Da.”:
Please be more precise here. Isotopes are separated by exactly one Da. To separate different ions on one nominal m/z value, a much better separation than one Da is required (as you later show in Table 2).
Line 74 “Ions delay extraction”: I think “delayed extraction” or “delayed ion extraction” is the common expression
Line 78: “Although there are many studies to improve one aspect of the performance of SPMS, the instrument's overall performance is insufficient.”: To which instrument do you refer here? This can’t be said in general with respect to all SPMS types. Do you refer specifically to the SPAMS?
Line 83: “Furthermore, the detection results of the as-configured system are shown”: replace by “Furthermore, the detection results of the system as it is configured are shown”
Line 102: “Fluent” software? Please give company name.
Line 102-103: Was the ADL newly designed or was the existing SPAMS lens optimized?
Line 108-110: As far as I understand, there are two mirrors and two photomultipliers, right? Or do you detect the scattered light from both laser beams on one PMT? But that’s not how it looks in Figure 1.
Line 115 “compensation model”: should read “mode”, right?
Line 142-143: “the SPMS was usually a single particle single acquisition,…” I think here is something wrong, I don’t get the meaning of this sentence.
Lines 158 -160: “In order to characterize the performance of the instrument, the scattering efficiency, hit rate associated with the instrument is defined. The scattering efficiency of particle is defined as the ratio of the response pulse count of the photomultiplier tube to the total number of injected particles”: change to “…the scattering efficiency and the hit rate associated…”
As I said before, I recommend to keep “detection efficiency”. It just needs to be defined properly. Later (Line 174 and Fig. 4) the reader learns that you defined two detection efficiencies, one for PMT1 and one for PMT2. That should be explained here already.
Line 163: How is N_sizing obtained?
Line 174: Ok, here (and in Fig. 4) it is clearly explained that there are two PMT and two detection efficiencies. This should be mentioned above in the definition of the detection efficiency.
Lines 182 -189: Can you separate the effects of the ADC and the new ADL? For example, sinf the ADC on the original SPAMS? It would be interesting to see the transmission curve of the ADC alone.
Line 194-195: “This is because the aerosol produced by the atomizer will be charged”.
What do you mean by this? I think it is the general widening of the particle beam with lower sizes, such that more particles miss the ablation laser spot. If it is only a charge effect, then HP-SPAMS should not show it due to the delayed extraction.
Line 196-197: “On the contrary, HP-SPAMS showed a better hit rate due to the use of DC-extraction (Chen et al., 2020; Clemen et al., 2020).”
Clemen et al. (2020) did not use the HP-SPAMS. Please correct (e.g. “a similar finding was reported by Clemen et al. (2020)”).
Furthermore: You defined “DC” as direct current in SPAMS, now you use “DC-extraction” for HP-SPAMS. Shouldn’t it read “pulse delay extraction” here?
Lines 201-212, Table 1 and Figure 6: PMT1-2 refers to particles detected at both PMTs?
Lines 214-219 and Figure 7: Dividing the SPAMS and HP-SPAMS curves by the SMPS curves should roughly correspond to the detection efficiency and it rate displayed in Figs 3 and 4, respectively. Did you test that?
Besides, I would choose a logarithmic scale for the diameter axis.
Line 228: “stratospheric cloud condensation nuclear”: there are not so many clouds in the stratosphere, except for polar stratospheric clouds. I suggest “upper tropospheric cloud nuclei”
Secton 3.2 and Figure 8: Fig 8 in this form is not very illustrative. I suggest to add a line showing averaged data (e.g. 10 m/z values averaged).
Table 2 and Figure 9: This is indeed a great improvement and the first time (to my knowledge) that a single particle instrument shows mass spectra that resolve such ions.
Lines 263-265 (Section 3.3):
What is m/z 202 (mercury?), why does it need to be excluded? If 206, 207 and 208 are present, doesn’t this confirm the presence of lead? If the particles additionally contain mercury, they are still “lead-containing”, right?

Figures:

Figure 4: It is good that you kept “detection efficiency” in the graph. Please make it consistent in the caption.
Figure 5, Caption: “SPMAS” -> “SPAMS”
Figure 10:
Instead of the upper plots, I would prefer mass spectra that show the peaks at 206, 207, and 208 clearly separated.
Lower plots: check x-axis: should read m/z 206

References:

Clemen, H. C., Schneider, J., Klimach, T., Helleis, F., Köllner, F., Hünig, A., Rubach, F., Mertes, S., Wex, H., Stratmann, F., Welti, A., Kohl, R., Frank, F., and Borrmann, S.: Optimizing the detection, ablation, and ion extraction efficiency of a single-particle laser ablation mass spectrometer for application in environments with low aerosol particle concentrations, Atmos. Meas. Tech., 13, 5923-5953, 10.5194/amt-13-5923-2020, 2020.
Murphy, D. M.: The design of single particle laser mass spectrometers, Mass Spectrom. Rev., 26, 150-165, 10.1002/mas.20113, 2007.
Zelenyuk, A., and Imre, D.: Single particle laser ablation time-of-flight mass spectrometer: An introduction to SPLAT, Aerosol Sci. Technol., 39, 554-568, 10.1080/027868291009242, 2005.

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ED: Publish subject to minor revisions (review by editor) (17 Jul 2023) by Lucia Mona

AR by Lei Li on behalf of the Authors (03 Aug 2023) Author's response Author's tracked changes Manuscript

ED: Publish subject to minor revisions (review by editor) (09 Aug 2023) by Lucia Mona

AR by Lei Li on behalf of the Authors (19 Aug 2023) Author's response Author's tracked changes Manuscript

ED: Publish as is (09 Dec 2023) by Lucia Mona

AR by Lei Li on behalf of the Authors (16 Dec 2023)

Journal article(s) based on this preprint

13 Feb 2024

Development and characterization of a high-performance single-particle aerosol mass spectrometer (HP-SPAMS)

Xubing Du, Qinhui Xie, Qing Huang, Xuan Li, Junlin Yang, Zhihui Hou, Jingjing Wang, Xue Li, Zhen Zhou, Zhengxu Huang, Wei Gao, and Lei Li

Atmos. Meas. Tech., 17, 1037–1050, https://doi.org/10.5194/amt-17-1037-2024,https://doi.org/10.5194/amt-17-1037-2024, 2024

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Xubing Du, Qinhui Xie, Qing Huang, Xuan Li, Junlin Yang, Zhihui Hou, Jingjing Wang, Xue Li, Zhen Zhou, Zhengxu Huang, Wei Gao, and Lei Li

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Currently, the limitations of Single-particle mass spectrometry detection capabilities render it not yet well suited for analyzing complex aerosol components in low concentration environments. In this study, a new high-performance single-particle aerosol mass spectrometer (HP-SPAMS) is developed to enhance instrument performance regarding the number of detected particles, transmission efficiency, resolution, and sensitivity, which will help in aerosol science.


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