A note on the application of commercial surface-enhanced Raman scattering substrates in trace analysisResponse to reviewersAs noted, we observed the presence of the impurity during our study of deposits of MBA. The preliminary identification of BPEs was carried out after comparison with literature data and BPEs appeared in our laboratory (and also throughout the department) only after this step. The absence of BPE in the EtOH used was proven by a simple experiment, described in Supplementary material: Klarite chips from batch 2009 and batch 2012 were dipped separately in EtOH in new (unused) weighing glasses and Raman spectra were measured without a lid. (i.e. indefinite thickness and EtOH evaporation during the experiment). No Teflon cell, no tubes, no reuse of solvent or chips. A development of BPE Raman bands was only observed in the case of the 2009 batch. Please note, without having the Klarite chips from the 2012 batch, it would be very difficult to prove the contamination of the 2009 batch (we believe that the SERS response corresponds to a BPE concentration of around 10-14 mol/L!). We have, like the two reviewers, been in contact with Dr Eustace of Renishaw Diagnostics to resolve the issue of the impurity, but unfortunately we have been unable to obtain a sample of the photoresist used in production or any other assistance. We agree that there is no big science behind this note. Our idea comes from communicating the problem, because probably every producer will exclude the possibility that the contamination comes from their products. Some problems with background spectra have been documented earlier (see ref.). To reviewer 2's response: There are several important reasons why the article "A note on the application of ...... in the middle of the article ...... of my articles, articles collaboratives that used Klarite substrates but I think they didn't look at the data presented. I have had frequent conversations with Dave Eustace and Alastair McInroy (renishaw diagnostics, formerly D3 technologies who manufacture Klarite substrates) regarding the manufacturing of Klarite substrates, they do not have BPE pervasive in the production process. Additionally, BPE track record has never been discussed, referred to, or measured by myself or colleagues in academia (UMBC) or other government establishments (ARL, ECBC). Typically, authors rightly argue that it is necessary to understand the background of your substrate (this is true for all analytical techniques), but they completely fail to understand that they are contaminating their own material. We present good data showing that the contamination is on the Klarite chip.