A new approach for liquid chromatography mass spectrometry (LC-MS) is described, based on achieving soft thermal vaporization followed by supersonic expansion and direct sample compound ionization, while in a supersonic molecular beam (SMB). The soft molecular vaporization step utilizes spray formation that is continued by fast thermal vaporization inside a channel supersonic nozzle, followed by ultrafast supercooling in a supersonic expansion. The short time (several microseconds) spent by the vaporized compound in the heated nozzle prior to its expansion cooling may result in incomplete vibrational equilibrium and thus reduced degree of dissociation. In addition, even if vibrational equilibrium at the nozzle temperature is obtained, the sample compounds have significantly reduced time for their dissociation, which is thus further minimized (kinetic consideration). As soon as the molecules expand and form a SMB, they are supercooled and any further dissociation is avoided. While in the SMB, the sample molecules can be ionized either by electron ionization as described in this paper or by hyperthermal surface ionization. The major goal of this method is to obtain high quality library searchable electron ionization mass spectra, for a broad range of thermally labile compounds, with higher sensitivity than that achievable by particle beam LC-MS. The soft thermal vaporization nozzle is described and mass spectral results with corticosterone are demonstrated. The potential advantageous features of this new method are discussed.
Modeling and experimental studies of quadrupole excitation of ions in linear quadrupole traps with added octopole fields are described. An approximate solution to the equations of motion of ions trapped in a quadrupole with added octopole and dodecapole fields, with quadrupole excitation and damping is given. The solutions give the steady-state or stationary amplitudes of oscillation with different excitation frequencies. Trajectory calculations of the oscillation amplitudes are also presented. The calculations show that there can be large changes in the amplitude of ion oscillation with small changes in excitation frequency, on both the low and high-frequency sides of a resonance. Results of experiments with quadrupole excitation of reserpine ions in linear quadrupole traps with 2.0%, 2.6%, and 4.0% added octopole fields are given. It is found that as the excitation frequency is changed, two resonances are generally . For tandem mass spectrometry, where ions are excited at their resonant frequencies in the presence of a collision gas to induce fragmentation, the addition of field distortions, described by the addition of higher multipoles to the potential, can increase the fragmentation efficiency, particularly at low pressures [2,3]. The spatial part of the potential in a linear quadrupole with field distortions can be written as a superposition of multipoleswhere Re[func] is the real part of the complex function func and A N is the dimensionless amplitude of a 2N-pole field. If no dc voltages are applied between the rods, the time-dependent potential iswhere V rf V V is the zero to peak rf voltage pole to ground, r 0 the field radius, x r , y r , are Cartesian coordinates, and t r time. The addition of higher multipoles can lead to nonlinear dynamics, giving sudden changes in the amplitude of ion oscillation with small changes in excitation frequency. These effects have been described in detail for dipole excitation of ions in a linear quadrupole trap with a 4% added octopole field [2a].Trapped ions can also be excited by quadrupole excitation, sometimes called parametric excitation [4]. With quadrupole excitation, the excitation electric field strength is proportional to the distance off axis. In a pure quadrupole field, ions are excited when the excitation angular frequency ex iswhere n ϭ 0, Ϯ1, Ϯ2 . . ., K ϭ 1, 2, 3, . . ., ⍀ is the angular frequency of the trapping radiofrequency field, and  is a function of the Mathieu parameter q given bywith e the charge of an electron, and z the number of charges on an ion. The effects of nonlinear dynamics can also be seen with quadrupole excitation. Werth and coworkers have reported large changes in oscillation amplitude and strongly asymmetric resonances with parametric excitation of ions in 3D Paul traps [5][6][7] and electrons in Penning traps [8,9]. These effects were attributed to the higher order fields of the traps.Address reprint requests to Dr.
Gas-phase oxidation of air-sensitive organometallic compounds does not proceed to a significant extent in mass spectrometric analysis unless a vacant coordination site is generated, making nitrogen generators a suitable source of desolvation gas.
Castration is among the most common management procedures performed in the dairy and beef cattle industries and is mainly performed by surgery or elastic banding. Despite the various benefits of castration, all methods produce pain and distress. Castration by banding is simple, inexpensive, produces fewer complications, and can be performed in a high-throughput manner. Because lidocaine, a local anesthetic, can be delivered to trauma sites topically, we have formulated lidocaine-loaded castration bands (LLBs) to deliver local pain relief to calves during banded castration. The initial lidocaine content of three band types developed was between 80 and 200 mg per band. The transfer kinetics of lidocaine into tissue was determined in vitro, indicating a rapid release for the first 30 min, followed by a slow release lasting at least 48 h. Furthermore, the lidocaine delivery and pain mitigation effects of these LLBs were compared to standard lidocaine injections in vivo. Field studies indicated that LLBs performed at least as well as lidocaine injections for short-term lidocaine delivery into tissues and pain mitigation. Moreover, LLBs significantly outperformed lidocaine injections for long-term delivery and pain mitigation. The concentrations of lidocaine in the LLB-treated tissue samples were generally in the range of 0.5–3.5 mg of lidocaine per gram of tissue and were overall highest after 6 h. Lidocaine-loaded elastration bands deliver therapeutic quantities of lidocaine into scrotal tissues over a period of at least seven days in cattle. This approach would provide long-term pain mitigation to the animals and, by avoiding surgery or the administration of injections, would also decrease the time and handling costs for the producer.
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