TiO₂ Decorated Low-Molecular Chitosan a Microsized Adsorbent for a ⁶⁸Ge/⁶⁸Ga Generator System

Round 1

Reviewer 1 Report

All raised questions have been addressed and the manuscript quality has improved considerably.

Interest for scientific community and relevance would benefit from a comparision with existing Generators and not only with former work by the authors.

Author Response

Thank you for considering our article for publication in Molecules. I am grateful to you and the reviewers for the valuable suggestions provided.

Reviewer 2 Report

The article: TiO₂ decorated low-molecular chitosan micro-sized adsorbent for ⁶⁸Ge/⁶⁸Ga generator system is an interesting and fits the subject of Molecules. Reported the column material for the ⁶⁸Ge/⁶⁸Ga generator with acid resistance and excellent adsorption and desorption capacity of ⁶⁸Ge and ⁶⁸Ga, respectively. Despite being a core element of the ⁶⁸Ge/⁶⁸Ga generator system, research on this has been insufficient. Therefore, we synthesized a low molecular chitosan-based TiO₂ (LC-TiO₂) adsorbent via a physical trapping method as a durable ⁶⁸Ge/⁶⁸Ga generator column material. The adsorption/desorption studies exhibit a higher separation factor of ⁶⁸Ge/⁶⁸Ga in the concentration range of HCl examined (0.01 M to 1.0 M). The prepared LC-TiO₂ adsorbent showed acid resistance capabilities with > 93% of ⁶⁸Ga elution yield and 1.6 x 10-4% of ⁶⁸Ge breakthrough. In particular, the labeling efficiency of DOTA and NOTA by using the generator eluted ⁶⁸Ga was quite encouraging and confirmed to be 99.65 and 99.69%, respectively. Accordingly, the resulting behavior of LC-TiO₂ towards the ⁶⁸Ge/⁶⁸Ga adsorption/desorption capacity and stability with aqueous HCl exhibited a high potential for ion-exchange solid phase extraction for ⁶⁸Ge/⁶⁸Ga generator column material. The result analysis is accurate and adequate. The authors, using the appropriate equipment, have thoroughly investigated the issue. Therefore, the manuscript can be recommended for publication in Molecules.

The following points should be taken into account:

1. It would be necessary to unify units according to the Si system
2. Incorrect order of publication parts, e.g.: Materials and Methods
3. What was the specific surface area and pore size of the starting TiO₂ used for synthesis?
4. Novelty elements should be better highlighted in the introduction. Papers should be cited in Introduction section; for example:

Effects of the adsorption of Ba²⁺ ions on the electrical double layer at the 4^th group metal oxide/electrolyte interface. Adsorption Science &Technology 22 (10) (2004).

Electokinetic and adsorption properties of different titanium dioxide at the solid/solution interface. Central European Journal of Chemistry 12 (11) (2014) 1194-1205

Structure of electrical double layer at the metal oxide with proteins/NaCl electrolyte solution interface. Adsorption Science & Technology 33(6-8) (2015) 567–574

Author Response

Comments from the reviewers:
Thank you for considering our article for publication in Molecules. I am grateful to you and the reviewers for the valuable suggestions provided.
Here are responses to the reviewer comments:

Reviewer
Comments: The article: TiO² decorated low-molecular chitosan micro-sized adsorbent for ⁶⁸Ge/⁶⁸Ga generator system is an interesting and fits the subject of Molecules. Reported the column material for the ⁶⁸Ge/⁶⁸Ga generator with acid resistance and excellent adsorption and desorption capacity of ⁶⁸Ge and ⁶⁸Ga, respectively. Despite being a core element of the ⁶⁸Ge/⁶⁸Ga generator system, research on this has been insufficient. Therefore, we synthesized a low molecular chitosan-based TiO₂ (LC-TiO₂) adsorbent via a physical trapping method as a durable ⁶⁸Ge/⁶⁸Ga generator column material. The adsorption/desorption studies exhibit a higher separation factor of ⁶⁸Ge/⁶⁸Ga in the concentration range of HCl examined (0.01 M to 1.0 M). The prepared LC-TiO₂ adsorbent showed acid resistance capabilities with > 93% of ⁶⁸Ga elution yield and 1.6 x 10^-4% of ⁶⁸Ge breakthrough. In particular, the labeling efficiency of DOTA and NOTA by using the generator eluted ⁶⁸Ga was quite encouraging and confirmed to be 99.65 and 99.69%, respectively. Accordingly, the resulting behavior of LC-TiO₂ towards the ⁶⁸Ge/⁶⁸Ga adsorption/desorption capacity and stability with aqueous HCl exhibited a high potential for ion-exchange solid phase extraction for ⁶⁸Ge/⁶⁸Ga generator column material. The result analysis is accurate and adequate. The authors, using the appropriate equipment, have thoroughly investigated the issue. Therefore, the manuscript can be recommended for publication in Molecules.
The following points should be taken into account:
1. It would be necessary to unify units according to the Si system

- This paper was written by referring to the 9th edition SI brochure.
2. Incorrect order of publication parts, e.g.: Materials and Methods

- Corrected (Manuscript line No.: 222, 234, 241, 253, 261, 265, and 270)
3. What was the specific surface area and pore size of the starting TiO₂ used for synthesis?

- TiO₂ (P25) is sold in the market, and it is confirmed to have a specific surface area of 35-65 m²/g. However, pore size measuring isn't easy to meet the reservation of the measuring equipment withinfive days. We ask for understanding regarding this matter.

4. Novelty elements should be better highlighted in the introduction. Papers should be cited in Introduction section;

- Inserted (Manuscript line No.: 58, Reference No.: 23, 24)