Ion-Selective Electrodes in the Food Industry: Development Trends in the Potentiometric Determination of Ionic Pollutants

Round 1

Reviewer 1 Report

Comments and Suggestions for Authors

This review article summarized the ion selective electrode for the food industry. This review article is important to improve ion-selective sensors for food industries and other sectors. However major revision is needed before accepting the manuscript. Please address the points below.

 

1. Figure 1 needs to be revised. There is no description of Figure 1c.

 

2. The quality of Figure 2 needs to be improved as some words inside the figure are difficult to read.

 

3. Please improve English writing and grammar in the manuscript.  A lot of sentences are written in complex or compound forms, which could make it difficult for readers to understand the meaning properly. So, the English should be revised through the English proofreading service.

 

4. Please add a reference for page 5 line 176.

 

5. Sensitivity is a crucial parameter for sensor development. What is the sensitivity of the electrodes described in all the tables? And also please add the pH of the solution in all cases. Describe the importance of the pH of the solution for detection.

 

6. There is no description of Reference 49 and 50 in Table 1. It seems that the performance of the electrode in reference 49 is better. What is the mechanism to improve such low LOD in reference 49 ?

 

7. Please add the reference “Electrochimica Acta 225 (2017) 105–113: https://doi.org/10.1016/j.electacta.2016.12.055” in the Arsenic detection section and discuss the importance of the pH of the solution for arsenite oxidation.

 

8. Please remove additional space in lines 490, 701, 720. Please correct the cation word in line 510. Please add space in line 628 ref [4]. Write Figure 6. c in line 789.

 

9. How about the summary of ref. 136 to 138 into Table 6?

 

10. There is no description of Figure 4. Please add discussion.

 

11. Please add the reference “Results in Chemistry 5 (2023) 100702: https://doi.org/10.1016/j.rechem.2022.100702 ”  in the Nitrite and nitrate section as this group found good sensitivity and LOD for nitrate sensing.

 

12. Figure 5 needs to be improved. What is the description of the black box membrane-based sensor? 3^rd image (ion imprinting) description is non-readable. Please improve the quality.

Comments on the Quality of English Language

English grammar needs to improve. Please avoid writing long sentences as it may cause problems during reading.

Author Response

I would like to thank the reviewer for the positive comments on the manuscript, especially regarding the importance of ion-selective electrodes in the food industry. I have reviewed the comments provided, and highlighted changes in the main manuscript. I hope the manuscript is up for publication. A detailed description on the revisions is provided below:

 

1. Figure 1 needs to be revised. There is no description of Figure 1c.

 

 I would like to apologise for this mistake. Figure description for Figure 1c has now been included (P3. L.126) as “By contrast, in all-solid-state ion-selective electrodes the inner solution is replaced by a capacitive film, typically conductive polymers with redox capacitance.”

 

2. The quality of Figure 2 needs to be improved as some words inside the figure are difficult to read.

I agree that the quality of Figure 2 needs improvement. This figure has now been replaced for a more readable version (P. 7, L.279).

 

 

3. Please improve English writing and grammar in the manuscript. A lot of sentences are written in complex or compound forms, which could make it difficult for readers to understand the meaning properly. So, the English should be revised through the English proofreading service.

I agree that English should be improved. The manuscript has been thoroughly reviewed, and sentences have been simplified to improve readability. Comments from the other reviews on the style have also been incorporated.

 

 

4. Please add a reference for page 5 line 176.

Reference has been incorporated (P.5, L.217).

 

5. Sensitivity is a crucial parameter for sensor development. What is the sensitivity of the electrodes described in all the tables? And also please add the pH of the solution in all cases. Describe the importance of the pH of the solution for detection.

The sensitivity of ion-selective electrodes operating under potentiometry is typically ~60 mV per decade of concentration for monovalent ions, and ~30 mV per decade of concentration for bivalent ions. This is the standard for sensitivity in these devices, and most of reported sensors reah this value. This has been explained within section 2 (P 4., L. 167), and sensitivity values have been incorporated to all tables. In the case of 1-methyl-2-butylthioimidazolium bis(trifluoromethane sulphonyl)imide applied to phosphate sensing, the sensitivity of the final device varied significantly with respect to the standard Nernst sensitivity. This has been indicated within the main case, and in the table (P.13, L.425).

Similarly, the pH of the samples studied have been indicated for those manuscripts where this was measured. For completion of this study, and to describe the importance of pH detection, the working pH range for each sensors have also been indicated in the tables and discussed in the main text. The importance of of pH measurements have also been added to section 5: Limitations of ion-selective electrodes in food and future trends (P.30, L.881).

 

 

6. There is no description of Reference 49 and 50 in Table 1. It seems that the performance of the electrode in reference 49 is better. What is the mechanism to improve such low LOD in reference 49 ?

I would like to apologise for the confusion, references 49 and 50 (now references 71 and 72) refer to silica-based devices that work under colorimetry and voltammetry, not potentiometry. This has now been explained within the main text, and the differences in their composition that lead to a lower limit of detection have been highlighted (P.8, L.305).

 

 

7. Please add the reference “Electrochimica Acta 225 (2017) 105–113: https://doi.org/10.1016/j.electacta.2016.12.055” in the Arsenic detection section and discuss the importance of the pH of the solution for arsenite oxidation.

Reference has been now included, including the role of pH on the oxidation of arsenic, and the importance of pH measurements to achieve accurate ion measurements (P.10., L.326).

 

 

8. Please remove additional space in lines 490, 701, 720. Please correct the cation word in line 510. Please add space in line 628 ref [4]. Write Figure 6. c in line 789.

I would like to apologise for these typos in the text. They have now been corrected.

 

9. How about the summary of ref. 136 to 138 into Table 6?

Apologies for the confusion, the summary of both references (now 168-170) have been included in the table. Reference 169 describes the interactions between between a thiourea derivative and phosphate, but it does not report a sensor. As such, this study has not been included (P. 21).

 

10. There is no description of Figure 4. Please add discussion.

Description of Figure 4 have been included in the text (P.23, L696, and P.24, L706).

 

11. Please add the reference “Results in Chemistry 5 (2023) 100702: https://doi.org/10.1016/j.rechem.2022.100702 ” in the Nitrite and nitrate section as this group found good sensitivity and LOD for nitrate sensing.

As requested by the reviewer, this reference has been included in the nitrite and nitrate section (P.23, L.666). For completion of the section, I have also expanded the discussion to include other voltammetric sensors for nitrite detection (P.23, L.670).

 

12. Figure 5 needs to be improved. What is the description of the black box membrane-based sensor? 3rd image (ion imprinting) description is non-readable. Please improve the quality.

Figure 5 have now been improved, so the ion imprinting figure is readable (P. 31, L.898). This figure has also been modified to include the importance of pH in food analysis.

Reviewer 2 Report

Comments and Suggestions for Authors

Dear Authors, 

Major revisions are needed

Comments for author File: Comments.pdf

Comments on the Quality of English Language

Moderate revisions

Author Response

We would like to thank the reviewer for the positive comments on the manuscript, and the thorough reviews provided. Changes have been highlighted in the main text. Below is a detailed description of the revisions. I hope the manuscript is now up for publication:

Improvement of the introduction: please report also other electrochemical methods for pollutant detection, voltammetric such as quinone or nitrites (doi.org/10.1039/D3GC01103H, doi.org/10.3390/nano12101779) or AI-integrated sensors (doi.org/10.3389/fenvs.2024.1336088m, doi.org/10.3390/s22208032).

We agree that introduction should be expanded, especially regarding other electrochemical techniques and pollutants. A complete overview of voltammetric and amperometric sensors have now been provided within the main text (P3-L63), and relevant references suggested by the review have been incorporated. The role of AI in sensing have also been added as a future perspective in the field (P.31-L903). Current work on quinones have been included in the introduction, where other food pollutants are discussed (P.1-L.41).

 

Please improve the ion-selective electrodes developed for lead detection in the food and beverages section, too few works reported.

 

We agree that section on lead ion-selective electrodes should be expanded. More reent work in the field have now been included, and discussed within the main text (P6-L233, and P.8lL320). For completion, other sections on heavy metal sensors have also been expanded (Hg²⁺, As, Cd²⁺), and additional performance parameters have been analysed in all cases as suggested by reviewer#1 (pH working range).

 

Also, the review should be a criƟcal revision and not only a summary.

We agree with the reviewer that a more critical discussion should be included. Sensors have now been critically reviewed in all sections, including advantages and limitations of each technology. For completion, a more thorough revision of electrodes, and the application in food have been added to section 5: Limitations of ion-selective electrodes in food and future trends (P.29-L837).

 

It is not well discussed quinone-based pollutants, please improve it: doi.org/10.1021/acssensors.9b02523, DOI: 10.2533/000942905777676614)

The description of quinone-based pollutants have been expanded in the introduction (P.1-L.41), and an overview of the prospects of detecting these components using AI have been provided in section 5, as suggested by the reviewer (P.31-L903).

 

Enhance the language and correct any typographical errors.

We agree that English should be improved. The manuscript has been thoroughly reviewed, and sentences have been simplified to improve readability. Comments from the other reviews on the style have also been incorporated.

 

What about polymer membrane sensing? Please improve not only talking about analytes but also the different types of elecrodes involved.

We agree that the description on the electrodes provided should be discussed. On each table, the ligand or material used for sensing for each analyte have been indicated. The membrane composition for each electrode have also been detailed within the main text, and advantages and limitations of each electrode composition have been highlighted on each section (P.7-L289). For completion, a more detailed discussion have been included in section 5, and summarised in Figure 5 (P.31-L897).

 

More concise and critical conclusion

We agree with the reviewer that conclusions should be shortened, and be more critical. Conclusions have now been reviewed (P.33-L.959).

Reviewer 3 Report

Comments and Suggestions for Authors

In the manuscript the author presents a review related to the current advances in the electrochemical quantification of heavy metals (lead, arsenic, mercury, and cadmium) and toxic anions (fluoride, phosphate, nitrite and nitrate, sulphides and perchlorates) in the food industry using potentiometric sensors. Various current challenges and future directions in this field are also presented.

After carefully reading the manuscript, my opinion is that the information provided in this paper is significant to a certain extent and is presented in a well-structured manner.

However, I have different comments, questions and recommendations.

First of all, the English language must be improved. There are sentences or paragraphs that require grammar corrections and/or changes for a better understanding of the meaning or/and of the scientific information. Therefore, many sentences / phrases / paragraphs must be corrected / reformulated.

Taking into consideration that the purpose of this review is to present current advances in the potentiometric quantification of ionic pollutants the references must be updated: from a total of 208 references ~ 15 % were published more than 20 years ago. In addition, the references are not written consistently. For example, in some cases the title of the journal is written, while in other cases the abbreviation of the journal’s title is given. More than that, in many cases the journal in which the article was published is not written at all.

My suggestions, comments and questions are found in the pdf format of the reviewed manuscript, being added like sticky notes.

Comments for author File: Comments.pdf

Comments on the Quality of English Language

English language must be improved. There are sentences or paragraphs that require grammar corrections and/or changes for a better understanding of the meaning or/and of the scientific information. Therefore, many sentences / phrases / paragraphs must be corrected / reformulated.

Author Response

I would like to thank the reviewer for the positive comments on the manuscript, and the thorough reviews provided. Changes have been highlighted in the main text. Below is a detailed description of the revisions. I hope the manuscript is now up for publication:

First of all, the English language must be improved. There are sentences or paragraphs that require grammar corrections and/or changes for a better understanding of the meaning or/and of the scientific information. Therefore, many sentences / phrases / paragraphs must be corrected / reformulated.

 

The manuscript has been thoroughly reviewed, and sentences have been simplified to improve readability. Comments provider by the reviewer on the manuscript have also been revised, and sentences have been reformulated (P.1-L24, P.2-L52, P3.-L102, P10-L326, P.19-L571, P.20-L603, P.23-L673, P.29-L853, P33-L963). Suggestions provided by the other reviewers have also been incorporated throughout the manuscript.

 

Taking into consideration that the purpose of this review is to present current advances in the potentiometric quantification of ionic pollutants the references must be updated: from a total of 208 references ~ 15 % were published more than 20 years ago. In addition, the references are not written consistently. For example, in some cases the title of the journal is written, while in other cases the abbreviation of the journal’s title is given. More than that, in many cases the journal in which the article was published is not written at all.

I agree with the reviewer that more recent references should be included in the manuscript. More recent work in potentiometric ion sensors have been included in all sections and tables, and some of the old references have been replaced. I also agree that references should be amended. All references have been reviewed to include the full journal title.

 

My suggestions, comments and questions are found in the pdf format of the reviewed manuscript, being added like sticky notes.

I would like to thank the reviewer for the thorough revisions. All comments provided on the sticky notes have been addressed and highlighted in the main text.

Round 2

Reviewer 1 Report

Comments and Suggestions for Authors

The authors updated the manuscript according to the reviewer's comments. The manuscript can be accepted.

Author Response

I would like to thank you the reviewer for the acceptance, and for the previews reviews that have helped to enhance the manuscript quality.

Reviewer 2 Report

Comments and Suggestions for Authors

Dear Authors, 

the manuscript is suitable for the publication

Comments on the Quality of English Language

English is fine

Author Response

I would like to thank you the reviewer for the acceptance, and for the previews reviews that have helped to enhance the manuscript quality.

Reviewer 3 Report

Comments and Suggestions for Authors

Dear Editor,

After carefully reading the revised manuscript my opinion is that the authors took into consideration most of my suggestions / comments: corrections were made and different comments and discussion were added in the manuscript. The references were updated and corrected in terms of the writing style. Thus, it is obvious that the manuscript was significantly improved.

However, there are some details that still need to be corrected, such as table numbering.

 

Comments on the Quality of English Language

Minor editing of English language required.

Author Response

I would like to thank you the reviewer for the acceptance, and for the previews reviews that have helped to enhance the manuscript quality. The manuscript have been reviewed, and table numbering have been amended. The text has also been revised, including reference numbering, and figures.