Mr. Banhegyi,

Under ''plasama'' I hope that you have understood ICP.

ICP is hard ionization method, and, in general it is not suitable for organics, because of there is a lack of information at a molecular level. It provides atomistic knowledge. Thus, it is suitable studying inorganics, metal-organics, etc.

MALDI allows to examine bulks, because of the repetition of the laser shot over the surface is controlled. Simply speaking you can repeat the position of the laser shot per surface point. As far as, however, the later procedure leads to an increasing of the time of the measurements there is frequently used solid films.

Dear Bojidarka,

By plasma ioniozation I meant a soft ionozation technique, but I did not find the proper acronym, see e.g. the following references

Article Characteristics of Low-Temperature Plasma Ionization for Amb...

Article Plasma-based ambient ionization mass spectrometry in bioanal...

Thank you for your answer anyway

Mr. Banhegyi,

I have focused attention on the shown in your posting publications, however, several things should be concerned with in using these papers:

First, the authors (Anal. Chem. 84 (2012) 10657-10664) have used MS low-temperature plasma (LTP) ionization method seeking to study nonpolar compounds at low temperature, minimum looking first at the graphical abstract, and accounting for highlights associated with ‘analysis of explosives’ and development of ‘portable MS instrumentation’ (p. 10657). The authors have studied, in fact, only 2 nonpolar compounds (acenaphtene and pyrene, Table 1), however. And thus claims for any capability of a method studying 2 compounds is completely unreliable. The study must be able to integrate all aspects of the chemometric tests, but in the published form the experimental design does not meet the requested criterion.

Third, the graphical abstract of paper ‘Anal. Chem. 2012, 84, 10657-10664’ reflects wrongly the capability and the limitations of ESI and APCI MS methods, as well. You should pay attention to one of our more recent contributions devoted to a parallel quantification by ESI and APCI methods (Ref. [5]). In particular, talking about nonpolar compounds our experimental spectra (Figs. 1 and 2) explicitly provide evidence that ESI and APCI exhibit almost comparable capability as ionization efficiency. We employ Orbitrap analyzer, as well. The latter method rather promotes a large number of additional MS reactions with participation of the analyte, which can serve as independent MS characteristics determining complex as molecular structure analytes, depending on the experimental conditions. The major reason is that it causes for a formation of radicals of the analytes, having different chemical reactivity. Thus even small difference in the molecular structure and subtle electronic effects cause for a different chemical reactivity. And thus, the increasing, in the number of parallel processes, there is able to distinguish unambiguously between molecular structures of large molecules in mixture having small differences of the molecular substituents (functional groups like –OH, NH2, -CH3, etc.). However, towards the common MS ions both ESI and APCI methods produce equal to information, furthermore in quantitative terms. You should bear in mind that in work [5] we have developed, in fact, quantitative model equations connecting important to physico–chemical parameters. And these data have been verified independently of using current monitoring method (CMM) (equation 9a ref. [5]). So that the claims for that ESI and APCI produce equal to analytical information towards nonpolar compounds are unambiguously evidenced experimentally, furthermore, using independent of method (CMM as shown above). It is validated, in fact. In this context the information about a limitation of the application of ESI to analysis of only polar compounds (work ‘Anal. Chem. 2012, 84, 10657-10664’) is wrong. It might seem reasonably even to mention that the abstract assumes a rather lack of experience neither towards ESI nor APCI methods.

Moreover, I should mention that we operate with additional independent of quantitative model as well as which shows correspondence with CMM r = 0.99944, however. Currently it is under consideration and on this base there is unable to show you the quantitative relations. But there are described more than 10 000 MS ions and reactions, so that our description, by contrast work ‘Anal. Chem. 2012, 84, 10657-10664’, represents a statistically significant analysis, which makes the models reliable from the perspective of the quantitative analytical chemistry and the chemometrics. The data in reference [5] can be evidenced additionally using completely independent of methodology approach applicable to a quantitative treatment of physico–chemical MS parameters, moreover, applicable to ESI, APCI, CID and MALDI methods, respectively.

Finally, the work ‘Anal. Chem. 84 (2012) 10657-10664’ provides statistically unrepresentative datasets and any claims for capability of ESI are unreliable, as well. Figure S1 (s.i.) reflects calibration data of LTP revealing a sigificant standard deviation comparing with ESI or APCI data. There is a lack of experimental MS spectra of the 3 methods which prevent their qualitatively evaluation. But even Fig. S1 is enough illustrative of the superior accuracy and precision of both ESI and APCI, which underlines the limits of LTP approach from the perspective of the analytical chemistry, rather than to show its ‘’superior’’ instrumental features.

With regard to the topic of your question, the LTP exhibits drawback towards accuracy, precision, and concentration limits of detection/quantitation. But, there is a lack of other statistical parameters associated with the validation of the protocol in work Anal. Chem. 2012, 84, 10657-10664. On the other hand, as mentioned above, the latter workdoes not provide reliable data from the perspective of the analytical chemistry.

Perhaps, MALDI would be more useful as a method according to the topic of your question, or DESI, for instance.

[1] Plasma Induced Oxidative Cleavage of Disulfide Bonds in Polypeptides during Nanoelectrospray Ionization, Anal. Chem. 82 (2010) 2856–2864

[2] Desorption Electrospray Ionization in a Small Pressure-Tight Enclosure, Anal. Chem., 79 (2007) 6398–6403.

[3] A Parallel Miniature Cylindrical Ion Trap Array, Anal. Chem. 72 (2000) 3291–3297.

[4] Mini 12, Miniature Mass Spectrometer for Clinical and Other Applications, Introduction and Characterization, Anal. Chem. 86 (2014) 2909-2916.

[5] B. Ivanova, M. Spiteller, Quantitative correlations between collision induced dissociation mass spectrometry coupled with electrospray ionization or atmospheric pressure chemical ionization mass spectrometry – Experiment and theory, J. Mol. Struct. 1157 (2018) 492-512.

Than you for the note. Meanwhile I managed to get the right acronym. I am talking about DART-MS spectrometry.

Article Effect of glow discharge plasma on step-index polymer optica...