Aerosol Dilution

To address the limitation of the TDS capability of ICP-MS, some vendors offer an aerosol dilution system, which introduces a flow of argon gas between the nebulizer and the torch to carry out aerosol dilution of the sample. This has the effect of reducing the sample s solvent loading on the plasma so it can tolerate much higher TDS levels than the 0.2%, which is typical for most ICP-MS instrumentation. However, 

FIGURE 3.13 The low-flow Cinnabar , a water-cooled cyclonic spray chamber for use with a microflow concentric nebulizer. (Courtesy of Glass Expansion, Inc.) 

FIGU RE 3.14 Principles of aerosol dilution. (From Performance Characteristics of the Agilent High Matrix Sample Introduction System (HMI), Agilent Technologies Application Note http // www.chem.agilent.com/Library/technicaloverviews/Public/5989-7737EN.pdf, January 2008.) 

Reducing oxide interferences to very low levels because less solvent/matrix is entering the plasma, providing better accuracy and more stable sampling conditions 

Eliminating the need for conventional liquid dilution of high-matrix samples prior to analysis 

---

Chapter 3 examines one of the most critical areas of the instrument—the sample introduction system. It discusses the basic principles of converting a liquid into a fine-droplet aerosol suitable for ionization in the plasma, and presents an overview of the different types of commercially available nebulizers and spray chambers. Although this chapter briefly touches upon some of the newer sampling components introduced in the past few years, such as microflow nebulizers and aerosol dilution systems, the new breed of desolvating nebulizers, chilled spray chambers, autodilution, and online chemistry systems, are specifically described in Chapter 17. 

More recently, a novel technique for the handling of high-matrix samples has been developed that introduces a make-up gas between the spray chamber and the torch. This technique, which has been termed aerosol dilution, does not require the introduction of more water into the system and protects the mass spectrometer components from the high levels of matrix components in the sample. This approach enables the ICP-MS system to directly aspirate 2-3% TDS, with the added benefit... 

Alternative Sample Introduction Techniques Nonstandard sampling accessories such as laser ablation systems, flow injection analyzers, cooled spray chambers, desolvation equipment, direct injection nebulizers, aerosol dilution techniques, and automated sample delivery systems and dilators are considered critical to enhancing the practical capabilities of the technique. Their use has increased significantly over the past few years as ICP-MS has been asked to solve more and more diverse applieation problems. Chapter 17 reflects the increased interest in sampling accessories, especially in the area of specialized sample introduction and desolvation devices to reduce the impaet of conunon interferences with complex sample matrices. 

Hexafluorophosphoric Acid. Hexafluorophosphoric acid (3) is present under ambient conditions only as an aqueous solution because the anhydrous acid dissociates rapidly to HF and PF at 25°C (56). The commercially available HPF is approximately 60% HPF based on PF analysis with HF, HPO2F2, HPO F, and H PO ia equiUbrium equivalent to about 11% additional HPF. The acid is a colorless Hquid which fumes considerably owiag to formation of an HF aerosol. Frequently, the commercially available acid has a dark honey color which is thought to be reduced phosphate species. This color can be removed by oxidation with a small amount of nitric acid. When the hexafluorophosphoric acid is diluted, it slowly hydrolyzes to the other fluorophosphoric acids and finally phosphoric acid. In concentrated solutions, the hexafluorophosphoric acid estabUshes equiUbrium with its hydrolysis products ia relatively low concentration. Hexafluorophosphoric acid hexahydrate [40209-76-5] 6 P 31.5°C, also forms (66). This... 

A third screening smoke-type is white phosphoms [7723-14-0] (WP), P (see Phosphorus and THE phosphides), which reacts spontaneously with air and water vapor to produce a dense cloud of phosphoms pentoxide [1314-56-3]. An effective screen is obtained as the P2O5 hydrolyzes to form droplets of dilute phosphoric acid aerosol. WP produces smoke in great quantity, but it has certain disadvantages. Because WP has such a high heat of combustion, the smoke it produces from bulk-filled munitions has a tendency to rise in pillarlike mass. This behavior too often nullifies the screening effect, particularly in stiU air. Also, WP is very brittle, and the exploding munitions in which it is used break it into very small particles that bum rapidly. 

Since the majority of the elements in surface dust arise from deposited aerosol and added soil it is not surprising to find strong linear relationships between the concentrations of the elements in an atmospheric dust and street or house dust. This is illustrated by the two examples given in Fig. 8 for remote house dust vs urban atmospheric dust and street dust vs rural atmospheric dust. As discussed above crustal/soil material is a major component of atmospheric dust and the soil based elements in the atmospheric dust are Al, Ca, Fe, Mg, Mn, Ni, K, Si and Ti. The elements As, Br, Cd, Cl, Co, Cu, Pb, Rb, Se, V, and Zn are, on the other hand, enriched in atmospheric dust. The same elemental distribution applies to surface dust, but in this case their concentrations (compared on a mass basis) are reduced presumably due to dilution with soil. However, the elements enriched in the atmosphere remain enriched in the surface dusts. 

Atropine, epinephrine, and lidocaine can be administered through the tracheal tube before venous access is achieved at 2-2.5 times the recommended intravenous dose diluted with 10 mL of normal saline or sterile water. Stop CPR, administer beyond the tip of the endotracheal tube, follow with five quick insufflations to aerosolize the drug, and then resume CPR. 

Note that this simple treatment assumes that the soil and sediment phases are entirely solid, i.e., there are no air or water phases present to dilute the solids. Later in the Level III calculation these phases and aerosols are included (see Table 1.5.4). 

Only selective ft-agonists are recommended for optimal delivery, dilute aerosols to minimum of 4 mL at gas flow of 6-8 L/min... 

Decontamination Soap and water, or diluted sodium hypochlorite solution (0.5 percent). If contamination of foodstuffs is suspected, boil for ten minutes to kill toxin. Botulism is not dermally active and secondary aerosols do not endanger medical personnel. 

Decontamination Soap and water, or diluted sodium hypochlorite solution (0.5 percent). Removal of potentially contaminated clothing should be done by people in full protective clothing in an area away from non-contaminated persons. For victims with bubonic plague, drainage, and secretion procedures need to be employed. Careful treatment of buboes is required to avoid aerosolizing infectious material. For victims with pneumonic plague, strict isolation is absolutely necessary. Heat, disinfectants and sunlight renders bacteria harmless. 

The principal laws for the fluorination of polymeric hydrocarbons are the same as those described above for the simple case. Direct fluorination has been used extensively in organic chemistry (but only since the early 1970s) in low-temperature methods, where the fluorine is strongly diluted with some inert gas (helium, argon, nitrogen, krypton). One can note the La Mar, aerosol-based, and liquid-phase fluorination methods. 

Examples of such procedures are making dilutions (not all components of the mixture may be equally soluble or miscible with the vehicle) and generating either vapors or respirable aerosols (not all the components may have equivalent volatility or surface tension, leading to a test atmosphere that contains only a portion of the components of the mixture). 

Compo- site Tablet/ capsule Powder/ Granule Cream/ Paste Viscous liquid Dilute liquid Aerosol ... 

By 1963, we had done considerable testing of LSD by the oral route, but we knew the military was more interested in the effectiveness of the respiratory route. Our first study of aerosolized LSD made use of an ancient Devilbiss nebulizer, a glass device relied on for decades by asthma sufferers. We partially filled its glass chamber with a very dilute solution of LSD in distilled water. 

The first aerosol experiments in this series utilizing quantitative techniques were performed by the writer in 1954. Two types of delivery were employed (a) powdered LSD diluted with talc, administered by means of a simple inertia device (Fig. la) (b) aqueous solutions of LSD administered intranasally by means of the nebulizer illustrated in Fig. lb. When a talc-LSD powder was administered intranasally, very severe reactions occurred rapidly. With a maximum dose of 256 meg delivered intranasally in the form of LSD-talc powder, subject J.M. had a most severe reaction, withdrawing to one part of my home in which the experiment took place and refusing to cooperate in his usual fashion. The data on Subject J.M. in this experiment are available. In order to study liquid aerosols, aqueous solutions of LSD-25 were administered intranasally to Subject J.M. The questionnaire was again used to estimate the severity of the reaction. The following technique of comparison was employed. 

---