Development and Validation of a Near Infra-Red (NIR) Hand-held Spectrophotometric Method Using PCA Approaches and Chemometric Tools: Application for Qualitative and Quantitative Determination of Tadalafil Marketed in Kinshasa—D.R. Congo

Round 1

Reviewer 1 Report

Comments and Suggestions for Authors

The authors present a method based on the use of NIR spectroscopy for the determination of taladafil in tablets. Although the idea of this work has a genuine interest as well as a practical point of view, there are several points that need to be explained in a more rigorous manner. Please find my review attached in PDF form. 

Other points of consideration

1. Apart from the evaluation given in the PDF, i would like to point out that the number of the cited references is particularly low (14 references used), considering the development of a spectroscopic analytical method. Also, the authors may need to use brackets instead of parentheses to cite the references inside the text to avoid confusion. 

2. There is no discussion of the presented data in the broader context of the existing results on the development of similar analytical methods based on spectroscopy. A comparative study with literature would be helpful to understand the success of the current work. 

 

Comments for author File: Comments.pdf

Comments on the Quality of English Language

Minor revisions needed in the text and figures. Some rephrasing would improve the readability of the manuscript.

Author Response

Dear colleague,

First of all, we would like to thank you a lot for your impressive remarks, then we invite you to see the attached file to find answers to your major questions and recommendations.

Moreover, you will find additional references and some novel inputs given in the text based on your remarks. We would also like to adress some of your questions within this field by answering them directly below:

Line 291: for SG(1,2,15) explanation, see the legend given in the buttom of the table.

Line 312: keep that as it is. that is right.

Line 313: that is the best way, we would like it to be presented instead of bringing modifications. 

Line 325: for calibration, we used simple medium made of the reference substance and solvent whereas the test medium is complex in terms of constituents due to the large number of components taken together. A part from the active ingredient, there are in the test sample excipients and additives that can significantly modify analytical environment; also impact the obtained data such as spectra.

Author Response File: Author Response.docx

Reviewer 2 Report

Comments and Suggestions for Authors

I recommend the paper Development and Validation of a Hand Held  Spectrophotometric Method by Near Infra-Red (NIR) Using PCA Approaches and Chemometric Tools: Application for Qualitative and Quantitative Determination of Tadalafil Marketed in Kinshasa-D.R. Congo, having authors: Jocelyn Mankulu Kakumba, Patient Ciza Hamuli, Merdie Mpemba Luyinama, Freddy Mugisho Kasago, Malachie Tembo Monyele, Dadit Ive Kitenge, trésor Bayebila Menanzambi, Trésor Kimbeni Malongo, Didi Mana Kialengila and Jérémie Mbinze Kindenfor being published in the Spectroscopy Journal. The data presented in this paper are very carefully selected and presented. The data are scientifically explained, and the authors underline the advantages of the methods presented in the paper.

Author Response

This is to thank you for your observations.

Best regards.

Reviewer 3 Report

Comments and Suggestions for Authors

1. Figures 5,6,7,8 need to be provided in a better quality

2. More references are needed

Comments on the Quality of English Language

3. Proofreading is needed

Author Response

Dear colleague,

Thank you very much for remarks.

To fix all the issues you mentioned, we provided the best quality figures and added references into our paper. And the language editing was also improved.

Reviewer 4 Report

Comments and Suggestions for Authors

The proposed study is well done, and the results are clearly presented.

Nevertheless, some minor issues should be clear before publication. 

Line 126-130 - why methods developed based on PCA and valid by PLS. It is not clear. 

Line 131 - 207 

Should there be materials and methods before Results and discussion?

Line 228 - A short intro to PCA should be given

Line 294 - similar to PLS 

 

 

 

 

 

Author Response

Thank you for your remarks.

Can you please take a look into the revised paper as uploaded to find more about changes you requested.

According to the presentation of material and methods point before results and discussion, it is logical as we followed the normal recommendation in terms of article papers writing that should be done following IMRAD in which results and discussion can not come before material and method.

Kind regards.

Author Response File: Author Response.docx

Round 2

Reviewer 1 Report

Comments and Suggestions for Authors

The authors have attempted to provide a revised version of the manuscript based on the given feedback, but it seems that only minor points have been addressed (e.g. typos and short explanations). There are still some important unanswered questions and errors that really need to be tackled. In particular: 1. In the graphs where they show the spectra (e.g. Fig 1, 2 etc), they present the x-axis in wavenumbers, which i do not understand based on the range shown (900-1700).....in such a case they would be performing mid-IR and not near-IR!! Near-IR spectroscopy refers to wavenumbers >4000, so in this case the x-axis must be in wavelengths (this is also seen in Table III)! 2. They still did not provide any answer on how they performed the NIR measurements! Did they do any background measurements and how? I did not see any answer or modification in the text for this. 3. In lines 237-238 of the revised version, they write: ''The figure 3 shows the calibration model recorded using the....''. What is this exactly? Figure 3 shows no calibration model....it shows NIR spectra. You need to be precise in the figure legend, otherwise it gets misleading. 4. In section 3.2.1 where they show the PCA results, they did not answer to my original question whether they performed any pre-processing of the data and what kind....They need to provide answers! 5. I am sorry but Table III MAKES NO SENSE.....It is very confusing and they need to find an alternative way to present it. In any case, do they really need to show all these info? For what reason? I have the impression that the current representation is what you get directly from the instrument, which is not necessarily proper for a publication. 6. In line 340 of the revised version, i had made a comment regarding the impact of the environmental and instrumental variability on the spectra and it seems that the authors have avoided to answer....At least, an argument/response is needed. 7. I also made a comment regarding some of the recovery rates that seem to be higher than 100%....Is there any response on this?  

OVERALL REMARK: The authors need to go through all the points of my initial feedback and provide proper response, which i could not see at the moment.

 

Comments on the Quality of English Language

English is ok

Author Response

Dear Colleague,

First of all, we would like to thank you for your impressive comments and contribution to improve our paper quality.

Can you please the attachement according to the revised document based on your comments whcih helped us to ameliorate our work quality for all.

However, with regard to your question about data pre-processing, we would like to assure you that it was carried out following the procedure described between lines 293-295 and summarized in table 2. 

About the environmental impact, see the line 349 of the revised document. And about some of the recovery rate over 100%, there is not comment because they are related to the observed results from the experiments.

With best regards,
Jocelyn MANKULU

Author Response File: Author Response.pdf

Round 3

Reviewer 1 Report

Comments and Suggestions for Authors

The authors have addressed several of the corrections that were suggested. However, questions 6 and 7 from my previous report (report 2) are not truly addressed. Question 6: Why did the authors use instruments that do not have waterproof shells, which can cause problems in spectra acquisition? Question 7: I am not doubting that what you are showing reflects your measurements, but recovery rates exceeding 100% shows that you are creating additional material....do you have an explanation for this? In addition, the authors do not mention if they performed any background measurements during spectra acquisition and how this was done. 

Author Response

Dear colleague,

Thank you very much for your contribution in helping us to present a better quality paper. And we will never cease to be grateful to you for this.

So, we invite you to see attached to this, our responses according to your comments.

 

Looking forward to seeing our article moved for the next step to its final publishing.

 

Best regards,

Jocelyn MANKULU

Author Response File: Author Response.docx