Spray chambers double pass

A further study by the Olesik group [138] used an interface with a laminar flow in the direction of the detector. The interface was a stainless-steel tee with the capillary threaded through the colinear ends of the tee. A sheath electrolyte was delivered through the lower arm of the tee with a peristaltic pump. Both a high efficiency nebuliser (HEN) and a concentric glass nebuliser were used in the study the former was used with a conical spray chamber and the latter with a Scott double-pass spray chamber. Increasing the sheath electrolyte flow-rate enabled the laminar flow to be eliminated, therefore improv-... 

Three different spray chamber designs (Fig. 3.6) are most often used for ICP-MS the Scott [15] (double-barrel) chamber, a conical chamber with an impact bead, and a cyclonic chamber [14,16,17]. The cyclonic spray chamber typically provides a slightly (up to about a factor of 2 or 3) higher analyte transport efficiency as well as somewhat shorter washout times. In some cases the spray chamber is cooled (such as on the HP 4500 ICP-MS double-pass spray chamber, which is cooled to 4°C) to reduce the amount of water vapor that enters the ICP further so that signals from polyatomic ions containing oxygen are reduced. The cooled spray chamber also helps maintain a stable spray chamber temperature. 

Figure 7 Effect of nebulizer gas flow rate and sample uptake rate on primary and tertiary aerosol drop size distributions. A Meinhard TR-30 nebulizer was used with a double-pass spray chamber, (a) Primary aerosol produced by nebulizer as a function of nebulizer gas flow rate for a 1-mL/min sample uptake rate, (b) Tertiary aerosol exiting spray chamber as a function of nebulizer gas flow rate, (c) Primary aerosol as a function of sample uptake rate at a nebulizer gas flow rate of 0.8 L/min. (d) Tertiary aerosol exiting spray chamber as a function of sample uptake rate. (From Ref. 18.)...

Figure 8 Analyte transport rate (expressed as equivalent volume of sample solution) as a function of sample uptake rate. A Cetac microcentric nebulizer (MCN) was used in a double-pass spray chamber. (From Ref. 422.)...

Liquid chromatography (LC) is the most commonly used technique for trace element speciation with ICP-MS detection. The mobile phase flow rates used with most LC techniques (0.5-2.0 mL min-1) are compatible for ICP-MS introduction using conventional sample introduction systems (pneumatic nebulization with cross flow and concentric nebulizers and double-pass spray chambers). An interface, known as a transfer line, must be constructed to allow connection between the outlet of the LC column and the nebulizer of the ICP-MS. Inert plastic tubing is commonly used for this purpose with the inner diameter and length kept to 20-50 cm in order to minimize peak broadening. 

FIGURE 23.1 Isotope ratio results from a urine sample spiked with 1.0 pg/L uranium, diluted 1/10 with 5% nitric acid, and analyzed with a single collector magnetic sector ICP-MS instrument with a standard double-pass spray chamber and 100 pL/min low-flow nebulizer. AVG, average STD, standard deviation RSD, relative standard deviation. 

Figure 2.18 (a) Concentric nebulizer mounted on a Scott-type double-pass spray chamber. 

FIGURE 3.4 Simplified representation of the separation of large and fine droplets in a double-pass spray chamber. 

FIGURE 3.10 A Scott double-pass spray chamber with cross-flow nebulizer (copyright 2003-2007, all rights reserved, PerkinEhner Inc.). 

Generally, a liquid sample introduction system suitable for ICP-MS consists of two main components (i) a nebuliser that turns the liquid bulk into an aerosol and (ii) a spray chamber that selects the maximum drop size that will be introduced into the plasma. The most often used nebuliser-spray chamber combination for ICP-MS is depicted in Figure 5.1. It consists of a pneumatic concentric nebuliser coupled to a double pass spray chamber. 

Double pass spray chamber. This device consists of two concentric tubes (Figure 5.1). The aerosol is passed through the inner tube and then forced to change its path by 180°. The aerosol leaving the chamber (i.e. the tertiary aerosol) is introduced into the plasma base by means of the torch injector. The main processes taking place inside the spray chamber (Figure 5.1), called aerosol transport phenomena , are (i) solvent evaporation from the aerosol droplets (ii) droplet... 

Cyclonic chambers (Figure 5.4) exhibit better analytical performance than double pass spray chambers. The nebuliser is tangentially connected to the spray chamber body. In the early... 

Double pass spray chamber and (b) cyclonic spray chamber. 

A negative effect found when working at low hquid flow rates is an increase in wash-out times, leading to a subsequent drop in sample throughput In order to mitigate this problem, new low inner volume spray chambers have been developed and their performance has been tested in ICP-MS. For a mini cyclonic spray chamber, called the Cinnabar, wash-out times were found to be significantly shortened with respect to a double pass spray chamber for the analysis of iodine species. Due to its simplicity and the small dispersion provided by this spray chamber, it has also been successfully applied as part of a CE-ICP-MS interface. Low inner volume single pass spray chambers have also been used in various ways as aerosol transport devices for ICP-MS, namely with the nebuliser directly connected to them, with an impact surface (i.e. bead) inside them and as part of a CE-ICP-MS interface. ... 

Elution with organic matrices, such as methanol, has been made possible by employing sample introduction systems able to remove the solvent from the aerosol stream (i.e. desolvation systems) or through electrothermal vaporization (ETV). In the latter case it has been confirmed that the ETV technique is preferable to using a cross-flow nebulizer-double pass spray chamber combination in terms of sensitivity and limits of detection. Desolvation systems also eliminate some polyatomic interferences caused by inorganic eluents (e.g. nitric acid, hydrochloric acid). ... 

A VG PlasmaQuad ICP-MS was used with typical operating conditions and flows. Oxygen (<2%) was used in the nebulizer gas flow in order to minimize the amount of carbon build-up in the MS interface region. A Scott-type double pass spray chamber was cooled to -5°C to minimize the amount of solvent vapor reaching the plasma. 

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