An electrospray element produces an electrospray jet, e.g. fine mist of ionized liquid droplets. One application for an electrospray jet is Within the ion-source chambers of mass spectrometers. The fine mist is produced at the outlet of a spray nozzle. In operation, the quality of the electrospray jet is effected by the cleanliness of the spray nozzle and the evenness of the mist generation.
An electrospray jet is often used in an environment where it is difficult for the operator to detect whether it is operating within its designed tolerance. One detection technique includes visual inspection of the electrospray jet using video imaging. This requires trained personnel and constant operator attention.
An automated method of evaluating an electrospray jet includes: capturing image information about the electro spray jet, enhancing the image information to provide a clearer image when needed, comparing the captured image information, and generating a signal to indicative of the electrospray jet operation.
The electrospray jet may be illuminated by a source to improve the contrast between the electrospray jet and the background. Sequential images are captured at user-defined intervals by an image processor. An optional lens may be used to focus the image of the electrospray jet prior to image capture. A comparator compares the sequential images and generates a signal indicative of the operation of the electrospray jet. The signal may be used as a control signal for the electrospray jet.
The focusing element 18, e.g. lens, is applied to the light, which may be polarized by an optional polarizing filter (not shown).
A jet “image patterns” consists of shape and reflectivity characteristics of the jet. If the jet moves away from an ideal position, the intensity of light or luminosity reflected by the jet will change. When the jet moves (sputters), the geometrical shape changes. Hence changes in brightness of the recorded image and shape changes of jet can be used to determine that a not optimal spraying condition is present. This can also be a gradual change that requires the system to calculate a score, e.g. difference between brightness between newly recorded frames and the reference frame(s), to determine whether or not the jet has issues that can impact ion generation.
The image information can be integrated by the controller with the total ion current (TIC) measured by the mass spectrometer (not shown). When the brightness changes and at the same times the TIC drops significantly, it is very likely that the drop in signal is related to the quality of the spray jet and adjustments must be done to avoid continued signal drop.
The spray diagnostic may be used in any mass spectrometer system with an electrospray source, e.g. quadrupole, time-of-flight, ion trap, orbitrap, magnetic sector, and Fourier transform-ion cyclotron resonance (FT-ICR) mass analyzers or a tandem mass spectrometer system, e.g. multi-stage multipoles, orthogonal multipole MS, QTOF, Trap-TOF. Alternatively, the mass spectrometer system may include multiple sources, e.g. electrospray ionization and an additional ion source. The additional ion source may be an atmospheric pressure chemical ionization (APCI) or atmospheric pressure photoionization (APPI) source.