Organic Ion-Associate Phase Microextraction/Back-Microextraction for Preconcentration: Determination of Nickel in Environmental Water Using 2-Thenoyltrifluoroacetone via GF-AAS

Round 1

Reviewer 1 Report

The manuscript entitled “Organic Ion-associate Phase Microextraction/Back-microextraction for Preconcentration: Determination of Nickel in Environmental Water Using 2-Thenoyltrifluoroacetone via GF-AAS” is presented as a microextraction/back microextraction method do detect Ni in water samples.

Although the overall content is interesting, I found issues that must be addressed to be suitable for publication.

The manuscript entitled “Organic Ion-associate Phase Microextraction/Back-microextraction for Preconcentration: Determination of Nickel in Environmental Water Using 2-Thenoyltrifluoroacetone via GF-AAS” is presented as a microextraction/back microextraction method do detect Ni in water samples.

Although the overall content is interesting, I found issues that must be addressed to be suitable for publication.

English:

There are many odd particles that makes the English confusing, it could be improved:

• Line 12: “qua a”
• Line 172: act qua
• Lines 174,175 and 187: qua
• Line 277: cum

Other sentences that must be corrected or clarified:

Line 140-141: Thus, the HTTA solution with 100% acetone (without diluting it with water) was used in this study.

Line 246: “ is effective than the dissolution” what does this means?

References:

The general reference selection seems acceptable, however there are some errors:

• Reference 7 is in different format than the others
• What is reference 26? If the information is included in a tablet, original source must be properly referenced
• Format of web page citation must include date of access
• Regarding reference 12, there are newest articles regarding HLLME, specifically with switchable solvents for trace metal determination

Specific Comments:

Section 3.1: What is the concentration level of Ni used for the experiment? And in general, for the procedure optimization/variable evaluation

Section 3.2: Authors stated the C12BzDMA+ is the best choice because the resulting recovery is the highest. However, according to figure 3, the three cations have similar (not significantly different) values. Furthermore, considering standard deviation Ben+ seems a better option, can the author detail their choice?

Figures 2, 4, 5 and 6 has the error bars hidden behind the graph, it could be better if the choice for the graph matches the style of Figure 1, BzA series. This is not crucial since the error is very small. Other option is use smaller symbols.

Section 3.3 Back extraction:

• HNO3 concentration: If 1 and 2 mol L-1 are similar and recovery is 100%, why select 2 mol L-1 instead of 1?
• Shaking time: if there is no difference between 0 and 6 minutes, why is shaking necessary? Also, in the paragraph authors refers as “maximum absorbance” to analyze the results, however the graph is for recovery values.

Section 3.4

• I find a better fit for this section (or at least Fig.7) early in the paper.
• Line 269, how does the coefficients be “nearly equal”?

Section 3.5

• When authors referred the “concentration factor of 400”, this is the initial and final volume ratio, but is this the preconcentration factor as we are used in microextraction?
• Is 0.1 ugL-1 the LOQ? Shouldn´t be 0.06 according to the LOQ?
• Why there is no precision study? Inter and intraday.

Section 3.6

• Recovery study must be carried out at three levels, and at least one of them must be the LOQ.
• I found difficult to understand the recovery calculation, since the blanks has analyte (0.24 ugL-1), can the authors include the values for relative and absolute recovery? If the samples contain analyte (not spiked), a calibration curve by standard addition is necessary.
• Authors analyze seawater, but there is no study of Ionic strength effect during optimization, although recovery of added analyte is 100%.
• Why there are n=2, 3 and 5?
• What is the subindex in the values of the section final paragraph? I believe is an editing typo.

Author Response

Dear Dr

Thank you very much for your valuable comments and suggestions concerning our manuscript entitled " Organic Ion-associate Phase Microextraction/Back-microextraction for Preconcentration: Determination of Nickel in Environmental Water Using 2-Thenoyltrifluoroacetone via GF-AAS (Manuscript ID: appliedchem-1443094)".

We found the referees' comments most helpful and have revised the manuscript accordingly.

In addition, some misunderstandings have been removed. Some parts have been added. Section 3.4 has been moved after section 3.2.

*****

English:

There are many odd particles that makes the English confusing, it could be improved:

Line 12: “qua a”

Line 172: act qua

Lines 174,175 and 187: qua

Line 277: cum

Other sentences that must be corrected or clarified:

"qua" and "cum" have been replaced with "as" and "and". (It was a painstaking effort to reduce the similarity. I've changed it back.)

Line 140-141: Thus, the HTTA solution with 100% acetone (without diluting it with water) was used in this study.

"Thus, in this study, the HTTA acetone solution was stored and used as is without diluting it with water." Changed to.

Line 246: “ is effective than the dissolution” what does this means?

Corrected lines 240-242.

The detection limits of the two methods were wrong, so they have been corrected.

References:

The general reference selection seems acceptable, however there are some errors:

Reference 7 is in different format than the others

Corrected.

What is reference 26? If the information is included in a tablet, original source must be properly referenced

Corrected.

Format of web page citation must include date of access

I added the date of access.

Regarding reference 12, there are newest articles regarding HLLME, specifically with switchable solvents for trace metal determination

HLLE has been studied for a long time, but I believe that it was Professor Igarashi who developed the substantial HLLME. I respected the first research and chose one of his studies.

I searched the Web of Science for "homogeneous liquid liquid microextraction switchable" to add it to the references, but all I found were organic compounds, and I could not find any references that measured metals (metal and atomic spectrometry).

Specific Comments:

Section 3.1: What is the concentration level of Ni used for the experiment? And in general, for the procedure optimization/variable evaluation

       I added it.

• Section 3.2: Authors stated the C12BzDMA+ is the best choice because the resulting recovery is the highest. However, according to figure 3, the three cations have similar (not significantly different) values. Furthermore, considering standard deviation Ben+ seems a better option, can the author detail their choice?

In Figure 3, the calculation of the recovery was different from Equation (1), so I recalculated it. The standard deviation of the recoveries for Ben+ happened to be lower due to offsetting. I changed the error bars from the standard deviation of the recovery to the relative standard deviation of the absorbance obtained by the first extraction. We chose C12BzDMA+ with the highest recovery.

Figures 2, 4, 5 and 6 has the error bars hidden behind the graph, it could be better if the choice for the graph matches the style of Figure 1, BzA series. This is not crucial since the error is very small. Other option is use smaller symbols.

Corrected

Section 3.3 Back extraction:

HNO3 concentration: If 1 and 2 mol L-1 are similar and recovery is 100%, why select 2 mol L-1 instead of 1?

For safety reasons, we choose the middle value.

Shaking time: if there is no difference between 0 and 6 minutes, why is shaking necessary? Also, in the paragraph authors refers as “maximum absorbance” to analyze the results, however the graph is for recovery values.

In Figure 7 (changed from Figure 6), the vertical axis was changed from               “recovery” to “normalized absorbance”. This resulted in a maximum of 2-4 min, so we rewrote it as such.

Section 3.4

I find a better fit for this section (or at least Fig.7) early in the paper.

Section 3.4 has been moved after section 3.2.

Line 269, how does the coefficients be “nearly equal”?

Added. (the concentration of TTA and PS in the IAP was 1 M each.)

Section 3.5

When authors referred the “concentration factor of 400”, this is the initial and final volume ratio, but is this the preconcentration factor as we are used in microextraction?

At least, in “switchable homogeneous liquid liquid microextraction", most of the enrichment factors were several tens of times higher, which means that the enrichment factor is high enough.

Is 0.1 ugL^-1 the LOQ? Shouldn´t be 0.06 according to the LOQ?

I don't know where it is.

Why there is no precision study? Inter and intraday.

I can't make it because of the deadline. I can't find it..

Section 3.6

Recovery study must be carried out at three levels, and at least one of them must be the LOQ.

I can't make it because of the deadline.

I found difficult to understand the recovery calculation, since the blanks has analyte (0.24 ugL-1), can the authors include the values for relative and absolute recovery?

I can't make it because of the deadline.

If the samples contain analyte (not spiked), a calibration curve by standard addition is necessary.

Figure 8, please.

Authors analyze seawater, but there is no study of Ionic strength effect during optimization, although recovery of added analyte is 100%.

It is my intention that the ionic strength of seawater levels will be fine.

Why there are n=2, 3 and 5?

The data for n=2 is shown in Figure 8.

What is the subindex in the values of the section final paragraph? I believe is an editing typo.

The numbers in the superscripts used to indicate less than significant digits, but have been removed.

Author Response File: Author Response.pdf

Reviewer 2 Report

The authors have conducted in-depth studies on the possibilities for pre-concentration and determination of nickel in environmental samples, which deserves to be published after a minor revision in accordance with the comments given in the attached file. 

Comments for author File: Comments.pdf

Author Response

Dear Dr

Thank you very much for your valuable comments concerning our manuscript entitled " Organic Ion-associate Phase Microextraction/Back-microextraction for Preconcentration: Determination of Nickel in Environmental Water Using 2-Thenoyltrifluoroacetone via GF-AAS (Manuscript ID: appliedchem-1443094)".

We found the referees' comments most helpful and have revised the manuscript accordingly.

In addition, some misunderstandings have been removed. Some parts have been added. Section 3.4 has been moved after section 3.2.

*****

Why the Ni(II) compounds with TTA– are represented as Ni/TTA2 and [Ni/TTA3 ]– instead of Ni(TTA)2 and [Ni(TTA)3]–? In my opinion the formulae Ni(TTA)2 and [Ni(TTA)3]– are more appropriate.

Corrected.

Line 215. The equation should be renumbered (9 instead of 6). It should be balanced.

Corrected.

Please, check the text related to Fig. 6 (lines 235-237). In my opinion Fig. 6 should be removed, and the text improved if necessary.

In Figure 7 (changed from Figure 6), the vertical axis was changed from               “recovery” to “normalized absorbance”. This resulted in a maximum of 2-4 min, so we rewrote it as such.

Line 267-268. The equation should be renumbered: 10 instead of 9.

Changed.

Please, check Ref. 26.

Corrected.

Author Response File: Author Response.pdf

Round 2

Reviewer 1 Report

I appreciate author´s response to my previous queries, however I still believe that the manuscript requires some ammendments.

Author´s response to references about HLLME-SHS:

I appreciate the honesty about author´s reference selection, however here are some examples about SHS based methods in homogeneous phase for metals:

DOI: 10.1134/S1061934819110054

https://doi.org/10.1007/s10661-019-7252-3

http://dx.doi.org/10.1016/j.talanta.2016.03.018

doi: 10.1016/j.molliq.2017.07.043

And there are many others. SHS based techniques takes place in homogeneous format, therefore they worth to be mentioned in my opinion.

Is 0.1 ugL^-1 the LOQ? Shouldn´t be 0.06 according to the LOQ?

I don't know where it is.

According to the linear range in line 299, LOQ is 0.1 ug/L. However LOD is 0.02 ug/L (Line 300). If LOD=3S a/b and LOQ=10S a/b, LOQ should be 0.06 not 0.1. Therefore this is wrong.

Precision study, proper recovery study (relative and absolute values) 

Authors declare that these important studies were not carried out because of "the deadline", therefore the paper was not ready and shouldn´t be submitted until properly finished. These are important studies from the analytical chemistry point of view for a method development.

Authors analyzed seawater, but there is no study of Ionic strength effect during optimization, although recovery of added analyte is 100%.

It is my intention that the ionic strength of seawater levels will be fine.

The point is still missing, if ionic strength is a variable, its effect must be evaluated during optimization.

Why there are n=2, 3 and 5?

The data for n=2 is shown in Figure 8.

Still n=2 is not representative enough, minimum n=3.

I believe my queries have not been addressed properly, I consider the manuscript still requires improvement.

Author Response

Dear Dr

Thank you very much for your valuable comments and suggestions concerning our manuscript entitled " Organic Ion-associate Phase Microextraction/Back-microextraction for Preconcentration: Determination of Nickel in Environmental Water Using 2-Thenoyltrifluoroacetone via GF-AAS (Manuscript ID: appliedchem-1443094)"

Last time, I could not respond to all of them because of the deadline.

I think I answered your comment pretty well this time.

Thank you very much.

Author Response File: Author Response.pdf

Round 3

Reviewer 1 Report

The paper in its present form has been improved in comparison to previous version. Therefore I recommend publication.

A couple of english edits are recomendable:

Line 308 and table 1 heads: replace "number of runs" by "replicates or number of replicates"

And line 309, samplestt is a typo of samples I believe.

Author Response

Dear Dr

Thank you very much for your valuable comments and suggestions concerning our manuscript entitled " Organic Ion-associate Phase Microextraction/Back-microextraction for Preconcentration: Determination of Nickel in Environmental Water Using 2-Thenoyltrifluoroacetone via GF-AAS (Manuscript ID: appliedchem-1443094)"

We found the reviewer's comments helpful and have revised the manuscript accordingly.

     Yours sincerely,

---------------------

Comments and Suggestions for Authors

The paper in its present form has been improved in comparison to previous version. Therefore I recommend publication.

A couple of english edits are recomendable:

Line 308 and table 1 heads: replace "number of runs" by "replicates or number of replicates"

     Replaced them.

And line 309, samplestt is a typo of samples I believe.

     Thank you very much. Corrected.

Author Response File: Author Response.pdf