Nebulizer optimization

These factors make it necessary to reduce the amount of solvent vapor entering the flame to as low a level as possible and to make any droplets or particulates entering the flame as small and of as uniform a droplet size as possible. Desolvation chambers are designed to optimize these factors so as to maintain a near-constant efficiency of ionization and to flatten out fluctuations in droplet size from the nebulizer. Droplets of less than 10 pm in diameter are preferred. For flow rates of less than about 10 pl/min issuing from micro- or nanobore liquid chromatography columns, a desolvation chamber is unlikely to be needed. 

Using Poiseuille s formula, the calculation shows that for concentric-tube nebulizers, with dimension.s similar to those in use for ICP/MS, the reduced pressure arising from the relative linear velocity of gas and liquid causes the sample solution to be pulled from the end of the inner capillary tube. It can be estimated that the rate at which a sample passes through the inner capillary will be about 0.7 ml/min. For cross-flow nebulizers, the flows are similar once the gas and liquid stream intersection has been optimized. 

Promoting an Optimal Response to Therapy When the mucolytic acetylcysteine is administered by nebulization, the nurse explains the treatment to the... 

This chapter describes use of solid-surface room temperature phosphorimetry (SSRTP) as a detection technique in the liquid chromatographic (LC) analysis of caffeine, theophylline, and theobromine. Measurements were made in a continuous mode, using a 2-nebulizer automatic system for SSRTP analysis (previously optimized for LC detection). Use of SSRTP and UV absorption detection was compared under identical experimental conditions.38... 

Coupling of CE with MS is a difficult task, because of the incompatibility of the EOF (100 500 nl min ) and optimal ESI ionization conditions. Moreover, a stable current for reproducible electrophoretic separations must be ensured. Fortunately, both these problems can be solved by adding make-up solution (10 100 g min ), which also ensures an electric connection between the nebulizer and the tip of a capillary. 

The multiple reaction monitoring (MRM) conditions for each analyte were optimized by infusing 0.1 jxglmL of analyte in mobile phase. The Ionspray needle was maintained at 4.0 kV and the turbo gas temperature was 650°C. Nebulizing gas, auxiliary gas, curtain gas, and collision gas flows were set at 35, 35,40, and 4, respectively. In the MRM mode, collision energies of 17,16, and 15 eV... 

The FIA valve is connected after the pump, approximately 25 cm from the nebulizer to minimize dispersion (this is the shortest distance attainable between the valve and the DCP jet). When attempting a new procedure, a IS s wash-out period should be allowed between injections this was found to be adequate to minimize any memory effects . However, the time can be shortened to 1—2 s for most applications, once the optimal experimental conditions have been established. 

Dams et al. [19] determined seven different opium alkaloids and derivatives in seized heroin using fast LC-MS analysis. Analytes were separated in 5 min on a monolithic silica column with a gradient elution system and an optimized flow of 5 mL/min. Detection was carried out using a sonic spray ion source [20] a modified ESI source were ionization is achieved using a nebulizer gas at sonic speed instead of applying an electrical field. 

The nebulizer capillary position may be adjustable on a screw thread to permit optimization of sample uptake and drop size. Alternatively or additionally, an impact bead may be placed in the path of the initial aerosol to provide a secondary fragmentation and so improve the efficiency of nebulization. Such a device is illustrated in Fig. 2.9. 

Adjusting the nebulizer. Measure the sample uptake rate using a 10 ml measuring cylinder and stop-watch. Report the result in ml min-i Compare this with your previous reading. Note that the sample uptake rate and flame conditions are interdependent and that adjusting one will require re-optimization of the other. Therefore, do not adjust the sample uptake rate once the fuel/air ratio has been optimized. 

Solution-based systems are common to both nebulizers and nasal formulations. In general, water will form the greatest fraction of the formulation, but, in some cases, cosolvents such as ethanol and propylene glycol may be added for increased stability. Acidifying and alkalizing excipients may also be added to optimize pH from the perspective of the drug stability as well as the physiological effect on the airways. Similarly, iso-osmotic and iso-tonic solutions are preferred. 

Arnoldsson and Kaufman optimized the response of the ELSD with a full factorial design evaluating the influence of evaporator temperature and air inlet pressure (70). As indicated in Fig. 10, the optimum conditions for both peak height and low baseline were achieved at high drift tube temperature and low-to-moderate nebulizer air pressure. The conditions chosen were 96°C and 1.6 bar. 

Eastman, S.J., Tousignant, J.D.,Lukason, M.J., Chu, Q., Cheng, S.H. andScheule, R.K. (1998) Aerosolization of cationic lipid pDNA complexes In vitro optimization of nebulizer parameters for human clinical studies. Hum. Gene Then, 9, 43-52. 

---