Droplet plume technique

Schematic diagram of hydrogen production by SMR process coupled with ocean C02 sequestration. C02 sequestration techniques (a) = L-C02 droplet plume option and (b) = liquid C02 lake option.

Thermospray and, more recently, electrospray ionization have found wide application as an interface technology between HPLC instruments and mass spectrometers. They represent powerful techniques for the analysis of complex lipids directly from solutions (Henion and Lee, 1990 Murphy, 1993). In most instances, the total HPLC eluant can be sent directly into the heated thermospray ion source. Here, the combination of heat and eluant velocity creates a plume of small-diameter particles suspended in a vapor (nebulization). A strong electric charge forms on the surface of the liquid particles and as the droplets evaporate the increase in charge ionizes analyte molecules that are discharged directly from the droplet into the gas phase. From here, they may enter the mass spectrometer directly. 

Several relatively new ionization techniques are derived from the canonical LDI approach. Some of them do not require the use of a vacuum [115-118]. For example, in the first step, neutral species can be desorbed from the condensed phase by a laser light beam, and in the second step, they can be mixed with the charged droplets present in an ESI plume. Several ionization schemes - which bear distinct names - are based on the same concept. For example, electrospray-assisted laser desorption/ionization (ELDI) (Figure 2.17) generally... 

Analyte ions can also be efficiently generated when sample vapor or finely dispersed sample droplets transported by a carrier gas stream are admixed to the expanding electrospray plume. This technique, simple yet effective, has been introduced as extractive electrospray ionization (EESI) [37]. It utilizes two separate sprayers, one conventional ESI sprayer to provide the electrostatically charged mist and another to supply the sample vapor or mist (Fig. 13.13). While this approach is suggested for API interfaces with the heated transfer capillary design, the sample carrier stream may alternatively be passed into the desolvation gas of interfaces employing the heated curtain gas design (Fig. 13.14) [6,38]. 

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