L. L. Mack

By means of electrospraying a dilute polymer solution into an evaporation chamber, negative macroions can be produced and a molecular beam formed by sampling the gaseous mixture of macroions, solvent, and nitrogen molecules with a nozzle-skimmer system of the Kantrowitz–Gray type. The macroion current can be detected by a Faraday cage after the light ions have been repelled from the beam by negative voltages on a repeller grid. Theoretical repeller voltages which best agree with the observed are those calculated by assuming a macroion velocity within 2% of the estimated supersonic beam velocity of 743 m sec−1. Polystyrene macroions of 51 000 weight-average amu tend to form dimers and trimers in the beam while larger polystyrene macroions of 411 000 weight-average amu appear mostly to be multiply charged single species. The results demonstrate that definite mass/charge states can be formed by the electrospray technique, that a considerable monochromatization of macroion velocities in the beam takes place, and that the macroions become highly concentrated relative to low-molecular-weight solvent and nitrogen ions during the transit time in the supersonic beam.

Using the electrospray technique and nozzle–skimmer system previously described, the influence of polystyrene concentration in the sprayed solution on the magnitude and substructure of the macroion current in the molecular beam has been investigated. Other variables studied include polarity of the beam, needle–nozzle and nozzle–skimmer distances, shape of spray, etc. Attempts to produce isolated macroions in the beam by carrier gas atomization were not successful; operation at reduced pressures and elevated temperatures was not found to be advantageous. In the case of positive macroions the current–repeller-voltage curves had less substructure than in the case of negative beams, and the first stopping potential was more dependent upon the solution concentration, especially when using a relatively large nozzle–skimmer distance. For molecular weights of the polystyrene from 600 to 97 200 the relative macroion positive charge was roughly proportional to the surface area of the macroions, assuming the latter to be spheres and as calculated from the first measured stopping potential. In the case of negative beams the current at zero repeller voltage and at a solution concentration of 2.2 × 10−6 Mw was proportional to the third power of the molecular weight at the lower solute molecular weights, as is predicted for a diffusional charging process.

Macroions of lysozyme and polystyrene produced by the electrospraying of dilute solutions of these macromolecules into nitrogen gas at atmospheric pressure have been studied by means of the measurement of their mobilities in nitrogen by means of an ion-drift spectrometer. In the case of polystyrene mainly clusters of negative macroions have been detected and studied, but in the case of lysozyme macroions containing one, two or three positive charges can be identified. The effect of change of solution concentration, temperature and pressure in the ion-drift tube on the data obtained in the case of polystyrene has been observed.

ADVERTISEMENT RETURN TO ISSUEPREVArticleNEXTGas Phase MacroionsMalcolm Dole, R. L. Hines, L. L. Mack, R. C. Mobley, L. D. Ferguson, and M. B. AliceCite this: Macromolecules 1968, 1, 1, 96–97Publication Date (Print):January 1, 1968Publication History Published online1 May 2002Published inissue 1 January 1968https://pubs.acs.org/doi/10.1021/ma60001a017https://doi.org/10.1021/ma60001a017research-articleACS PublicationsRequest reuse permissionsArticle Views460Altmetric-Citations44LEARN ABOUT THESE METRICSArticle Views are the COUNTER-compliant sum of full text article downloads since November 2008 (both PDF and HTML) across all institutions and individuals. These metrics are regularly updated to reflect usage leading up to the last few days.Citations are the number of other articles citing this article, calculated by Crossref and updated daily. Find more information about Crossref citation counts.The Altmetric Attention Score is a quantitative measure of the attention that a research article has received online. Clicking on the donut icon will load a page at altmetric.com with additional details about the score and the social media presence for the given article. Find more information on the Altmetric Attention Score and how the score is calculated. Share Add toView InAdd Full Text with ReferenceAdd Description ExportRISCitationCitation and abstractCitation and referencesMore Options Share onFacebookTwitterWechatLinked InRedditEmail Other access optionsGet e-Alertsclose Get e-Alerts