This has comments on the paper entitled ''Determination of low B/Ca ratios in carbonates using ICP-QQQ.'' The authors present an interesting new development and have demonstrated the determination of low B/ Ca amount ratios in carbonates in the mmol/mol range using Agilent ICP-QQQ in the MS/MS mode. It is an interesting piece of work with most of the problems of isobaric interferences, tail contribution etc. taken care by MS/MS mode in QQQ. However, we have a few observations on the data presented by the authors and would be happy if the authors' reply to the same.The authors have used 46 Ca and 11 B to determine B/Ca ratio. As mentioned by authors, it is a nice idea to use low abundant Ca isotope so that both Ca and B can be measured in the ion counting mode, instead of measuring one isotope in the analog mode. 46 Ca is the lowest abundant isotope of Ca with its abundance as 0.004 atom%. However, there is also a very large uncertainty on its abundance. NIST data base [Brand et al., 2014] quotes an uncertainty of 75% on this abundance {atom fraction of 46 Ca 5 0.00004(3)}.Thus, the data presented by authors by assuming atom % of 46 Ca as 0.004% must be given a relook and the large uncertainty of 75% on 46 Ca abundance has to be included in all the data presented in the paper. The data presented by authors in Tables 1 and 2 show that B/Ca amount ratios obtained by them using ICP-QQQ are significantly lower compared to those reported previously using TIMS as well as SIMS. As mentioned by authors, the B/Ca ratios obtained by them for CARRARA and OKA samples are factors of 2-3 lower than those reported by TIMS. However, these are 2.6% and 7.1% lower for JCT and JCP samples, respectively. The B/Ca ratios in CARRARA ad OKA samples are low by two orders of magnitude compared to those in JCT and JCP. The authors state ''one interpretation is that TIMS isotope dilution determinations overestimated the B content due to potential contribution of B blank and perhaps, to the incomplete isolation of the 11 B signal from the 12 C tail.'' First, there is no question of 12 C tail since in TIMS, B is not measured as B 1 ion but as an alkali metal borate ion and also one does not get C 1 ions in TIMS due to the fact that the first ionization potentials of both C and B are quite high. Of course, if the boron blank is not taken care of (which the labs. would have controlled and checked), then one cannot compare the data by any technique.The data presented in Table 2 are a comparison of the results obtained using ICP-QQQ and those obtained by SIMS previously. Again the results of ICP-QQQ are significantly lower compared to those of SIMS, for 6 out of 8 samples, with factors of 1.6 to about 6. The authors agree that the higher values by SIMS cannot be explained due to the abundance sensitivity effects of 12 C tail. If these differences are due to sample-beam interaction effects in SIMS, data on at least a few samples can be checked by LA-ICPMS or preferably by ID-TIMS.It is difficult to digest that the two independent techniques v...