Synthesis of an Organotin Specific Molecularly Imprinted Polymer for Organotin Passive Sampling in Seawater

Round 1

Reviewer 1 Report

Dear Authors,

The manuscript contains interesting and proper information with logical coherence. The work is generally well written but requires some corrections for better clarity of communication. Still, I consider that doesn’t sufficiently describe the scientific part. In the Introduction chapter, it is necessary to add more information about specific molecularly imprinted polymers (e.g., their characteristic properties for Marina water!! - or seawater). This part is too general and doesn’t entirely fit the topic. Also, provide better how the used synthesis ways (bulk, suspension, and mini-emulsion processes) represent progress in other similar studies. The study novelty must be well pointed. Moreover, the paper contains some typos and other mistakes. 

Please, add the specific chemical reactions or a flowchart for every used synthesis way. Please, add the instrumental information and data acquisition parameters of the used equipment (e.g., sensitivity or detection limits for butyl species analysis in water).

Please, add the formula for the constant kinetic computation.

Please, use English words instead of French in Table 2.

Please, indicate more the importance of your study (the strengths and weaknesses) in the Conclusions part.

Please, provide more data about what else needs to realize in the future and what is essential in the study.

Please, write the reference list in concordance with the author’s instructions.

In the manuscript, there are some typing errors:

R39 - one letter in the acronym EQS is missing;

R68 – log Kow instead of log(know) (It is well-known that is commonly used as a measure of hydrophobicity);

R152, 156 – mL instead of ml

R303 – firstly, use the organotin compounds and then the acronym OSn

R335, 360, 367 – assays instead of essays;

R339 – respectively instead of respectfully;

R375 – AG instead of Ag

Author Response

authors answers TO Reviewer’S COMMENTS

The authors thank the reviewers for their relevant comments and pertinent corrections.

The manuscript was corrected in agreement with their suggestions; the modifications and/or the supplementations are in red in the new version of the manuscript.

Please find below the respective response to the reviewers.

Reviewer 1

The manuscript contains interesting and proper information with logical coherence. The work is generally well written but requires some corrections for better clarity of communication. Still, I consider that doesn’t sufficiently describe the scientific part.

In the Introduction chapter, it is necessary to add more information about specific molecularly imprinted polymers (e.g., their characteristic properties for Marina water!! - or seawater).

We have completed this section and clarified the issues related to complex seawater matrices.

This part is too general and doesn’t entirely fit the topic. Also, provide better how the used synthesis ways (bulk, suspension, and mini-emulsion processes) represent progress in other similar studies.

The study novelty must be well pointed.

We have clarified this point by underlining the fact that polymers have never been used as a receptor phase for MIP

Moreover, the paper contains some typos and other mistakes. 

1. Please, add the specific chemical reactions or a flowchart for every used synthesis way.

Thank you for your comment. A diagram representing the different steps of MIP synthesis has been added to the manuscript. The conditions for the polymerization reaction to obtain the MIP samples by the three procedures (bulk, suspension, mini-emulsion) remain the same. The difference consists only in the size of the organic phases where the reaction takes place.

2. Please, add the instrumental information and data acquisition parameters of the used equipment (e.g., sensitivity or detection limits for butyl species analysis in water).

We have specified this point

3. Please, add the formula for the constant kinetic computation.

We have added the formula

4. Please, use English words instead of French in Table 2.

We have corrected this point (Table 3)

5. Please, indicate more the importance of your study (the strengths and weaknesses) in the Conclusions part.

We have added some precisions

6. Please, provide more data about what else needs to realize in the future and what is essential in the study.

We have added some precisions

7. Please, write the reference list in concordance with the author’s instructions.

Corrections were done as requested by the journal :

1. Author 1, A.B.; Author 2, C.D. Title of the article. Abbreviated Journal NameYear, Volume, page range.

Typing errors:

1. R39 - one letter in the acronym EQS is missing;
2. R68 – log Kow instead of log(know) (It is well-known that is commonly used as a measure of hydrophobicity);
3. R152, 156 – mL instead of ml
4. R303 – firstly, use the organotin compounds and then the acronym OSn
5. R335, 360, 367 – assaysinstead of essays;
6. R339 – respectivelyinstead of respectfully;
7. R375 – AG instead of Ag

All these corrections were done.

Author Response File: Author Response.pdf

Reviewer 2 Report

This manuscript is an interesting work on the synthesis of a molecularly imprinted polymer for sampling OTC in seawater. This type of passive sampler would be a great benefit for OTC analyses in seawater, but unfortunately it seems that this research has not been completed and therefore its significance is questionable.

The authors have described three different synthesis procedures and investigated the efficiency of OTC adsorption on the synthesised polymers. However, this study lacks: 1) the optimisation of the washing process that will completely remove the residues of OTC remaining after the synthesis (even the removal of 99% of OTC may not be satisfactory for the analysis of a very low concentrations in seawater (<0.5 ng(Sn)/L)), ii) the evaluation of the retention efficiency of OTC for all three types of synthetised polymers (not only for bulk synthetised MIP), and iii) the testing of the applicability of the synthesised polymers to real environmental samples i.e. seawater (low environmental levels of OTC, matrix effects, etc..).

Although the authors are aware of these shortcomings, as they have mentioned some of them in the paper itself, I think this paper should be published only after the above experiments are carried out.

Specific comments:

- describe more clearly (in the introduction or in the discussion section) what the advantage of this study is compared to the works on passive samplers for OTC published by Gallego-Gallegos et al. and Zamora-Galvez et al.

- what is the main conclusion of this study regarding the comparison of three synthetised polymers for sampling and analysis of OTC?

- too much ˝introduction˝ in the abstract, and too little ˝results and conclusion˝. The abstract should be rewritten to clearly highlight the results of the study conducted

- check the word order in the title

- line 226 - CRM for OTC in sediments is not suitable for validation of the method for OTC analyses in water

- table 2 – column ˝mode de synthese˝ write in English

 

Author Response

authors answers TO Reviewer’S COMMENTS

The authors thank the reviewers for their relevant comments and pertinent corrections.

The manuscript was corrected in agreement with their suggestions; the modifications and/or the supplementations are in red in the new version of the manuscript.

Please find below the respective response to the reviewers.

Reviewer 2

Although the authors are aware of these shortcomings, as they have mentioned some of them in the paper itself, I think this paper should be published only after the above experiments are carried out.

Specific comments:

- describe more clearly (in the introduction or in the discussion section) what the advantage of this study is compared to the works on passive samplers for OTC published by Gallego-Gallegos et al. and Zamora-Galvez et al.

Clarifications were added in the introduction underlining in particular the fact that Gallegos Gallegos tested the PIMs only upstream of the analytical part to preconcentrate the compounds for their analysis and not to capture these compounds in situ in the framework of passive samplers. Concerning the study of Zamora, about sensor for tributyltin, detection which does not allow to reach the EQS required for the WFD and only tested and validated for filtered seawater matrices.

- what is the main conclusion of this study regarding the comparison of three synthetised polymers for sampling and analysis of OTC?

Some précisions were added : Retention efficiency of MIP doesn’t seem to depend on the type of synthesis chosen, consequently, bulk polymerization is recommended because of its achievement simplicity.

- too much ˝introduction˝ in the abstract, and too little ˝results and conclusion˝. The abstract should be rewritten to clearly highlight the results of the study conducted

Corrections were done

- check the word order in the title

Corrections were done

- line 226 - CRM for OTC in sediments is not suitable for validation of the method for OTC analyses in water

We fully agree with the reviewer comment. However, no certified reference samples in aqueous form are marketed because of their instability. Extracts in methanol to be diluted with water exist but are, in our opinion, of little relevance.

- table 2 – column ˝mode de synthese˝ write in English

Correction was done

 

 

Author Response File: Author Response.pdf

Reviewer 3 Report

Title is not clear.  The title may be modified as " Synthesis of an organotin specific molecularly imprinted polymer for passive sampling of butyltin compounds in the marine environment" 

The authors clearly justified the need for the study.  

The authors used suitable methods including MIP synthesis, kinetics experiments, and butyltin derivatives analysis.

The authors may indicate whether swelling has occurred during the extraction of 8 hours.  Comparison of SIM at the cross-sectional area before and after washing MIP by soxhlet extraction using solvents.  Because some polymer (poly(methylmethacrylate)) -swelling has occurred when you use organic solvent.  Therefore, free volume increases and therefore, size of the imprinted will be different.  

Calculation of partition coefficient between water and MIP (Kpw) and comparison  of log Kow and log Kpw:

Since the authors measured concentrations of OSn in water (Cwater) and MIP (Cmip), I suggest them to calculate  log Kpw for MBT, DBT and TBT using Kpw= Cimp (ngSn/g) / Cwater (ng Sn/mL).  If Kow and Kpw  are not similar, then the compounds did not reach equilibrium yet and did not accumulate enough in MIP.  In this case, the authors need to increase exposure time - more than 8 hours.  In addition, butyltins are hydrophobic compounds that persist in the environment.  Therefore, in my opinion exposure time of 8 hours is short. 

The authors may consider referring the following article to give some background information about the butyltin compounds and their environmental behavior. 

Loganathan, B.G., Kannan, K., Sajwan, K.S. and Owen, D.A. 2001. Butyltin compounds in freshwater ecosystems. In:  Persistent, Bioaccumulative and Toxic Chemicals I: Fate and Exposure. (Eds. R.L. Lipnick, J. Hermens, K. Jones and D. Muir ). American Chemical Society, Washington, DC. ACS Monograph Series vol. 772. 308pp.

 

This is a well planned and executed study, this manuscript may be accepted for publication after minor revision.  

 

Author Response

authors answers TO Reviewer’S COMMENTS

The authors thank the reviewers for their relevant comments and pertinent corrections.

The manuscript was corrected in agreement with their suggestions; the modifications and/or the supplementations are in red in the new version of the manuscript.

Please find below the respective response to the reviewers.

Reviewer 3

Title is not clear.  The title may be modified as " Synthesis of an organotin specific molecularly imprinted polymer for passive sampling of butyltin compounds in the marine environment"

Modification is done in the title

1. The authors may indicate whether swelling has occurred during the extraction of 8 hours. Comparison of SIM at the cross-sectional area before and after washing MIP by soxhlet extraction using solvents.  Because some polymer (poly(methylmethacrylate)) -swelling has occurred when you use organic solvent.  Therefore, free volume increases and therefore, size of the imprinted will be different. 

Indeed, this is an important factor. This precision has been added in the text. No swelling was observed during the experiment which lasted up to 8 hours.

2. Calculation of partition coefficient between water and MIP (Kpw) and comparison of log Kow and log Kpw: Since the authors measured concentrations of OSn in water (Cwater) and MIP (Cmip), I suggest them to calculate  log Kpw for MBT, DBT and TBT using Kpw= Cimp (ngSn/g) / Cwater (ng Sn/mL).  If Kow and Kpw  are not similar, then the compounds did not reach equilibrium yet and did not accumulate enough in MIP.  In this case, the authors need to increase exposure time - more than 8 hours.  In addition, butyltins are hydrophobic compounds that persist in the environment.  Therefore, in my opinion exposure time of 8 hours is short.

This remark is very interesting and we will be able to calculate this coefficient when the polymers have been completely washed.

3. The authors may consider referring the following article to give some background information about the butyltin compounds and their environmental behavior.

Loganathan, B.G., Kannan, K., Sajwan, K.S. and Owen, D.A. 2001. Butyltin compounds in freshwater ecosystems. In:  Persistent, Bioaccumulative and Toxic Chemicals I: Fate and Exposure. (Eds. R.L. Lipnick, J. Hermens, K. Jones and D. Muir ). American Chemical Society, Washington, DC. ACS Monograph Series vol. 772. 308pp.

The authors thank the reviewer for this reference, but it concerns data in fresh water whereas we work in sea water. Nevertheless, we follow this recommendation and have enriched the manuscript by adding a reference, Okoro, H. K.; Fatoki, O. S.; Adekola, F. A.; Ximba, B. J.; Snyman, R. G. Sources, Environmental Levels and Toxicity of Organotin in Marine Environment-A Review. Asian Journal of Chemistry 2011; 23(2), pp.473-482.

Author Response File: Author Response.pdf

Round 2

Reviewer 1 Report

The authors adequately addressed most of my comments in the revised manuscript. Therefore, I recommend the publication of this manuscript in the Water journal.

Author Response

The authors thank the reviewer for his comments and  recommendation to publish the article

Reviewer 2 Report

The authors only responded to my specific and minor comments, but did not address any of the three main complaints I had about this study (written in the first part of my letter). Therefore, my opinion about this manuscript could not be changed. I think that this study still needs to be worked on before it is published.

Author Response

Thank you for your remark.

We add some complement in conclusion. This study is a first step for using MIPs for specific passive sampling for organotin compounds. We highlighted the potential of MIPs for OSn retention and therefore in passive sampling of these compounds. Comparison of three synthesis ways of MIPs tends to highlight a good retention of OSn with a mean retention kinetic. Retention efficiency of MIP doesn’t seem to depend on the type of synthesis chosen, consequently, bulk polymerization is recommended because of its achievement simplicity. Our study demonstrates the possibility of synthesizing mips for use in the fabrication of specific phases for passive sampling of organotin compounds. Tests were performed for the first time with these MIPs in powder form and not in cartridge form used to preconcentrate organotin compounds before an analytical technique. The kinetics achieved using powder form under conditions close to those it could be implement in natural ecosystems testify to the promising character of the use of MIPs.

Best regards