Process sample inlet

To examine a sample by inductively coupled plasma mass spectrometry (ICP/MS) or inductively coupled plasma atomic-emission spectroscopy (ICP/AES) the sample must be transported into the flame of a plasma torch. Once in the flame, sample molecules are literally ripped apart to form ions of their constituent elements. These fragmentation and ionization processes are described in Chapters 6 and 14. To introduce samples into the center of the (plasma) flame, they must be transported there as gases, as finely dispersed droplets of a solution, or as fine particulate matter. The various methods of sample introduction are described here in three parts — A, B, and C Chapters 15, 16, and 17 — to cover gases, solutions (liquids), and solids. Some types of sample inlets are multipurpose and can be used with gases and liquids or with liquids and solids, but others have been designed specifically for only one kind of analysis. However, the principles governing the operation of inlet systems fall into a small number of categories. This chapter discusses specifically substances that are normally liquids at ambient temperatures. This sort of inlet is the commonest in analytical work. 

A mass spectrometer consists of four basic parts a sample inlet system, an ion source, a means of separating ions according to the mass-to-charge ratios, ie, a mass analyzer, and an ion detection system. AdditionaUy, modem instmments are usuaUy suppUed with a data system for instmment control, data acquisition, and data processing. Only a limited number of combinations of these four parts are compatible and thus available commercially (Table 1). 

Such conformational dependence presents challenges and an opportunity. The challenges he in properly accounting for its consequences. In many cases, exact conformational energetics and populations in a sample may be unknown, and the nature of the sample inlet may sometimes also mean that a Boltzmann distribution cannot be assumed. Introducing this uncertainty into the data modeling process produces some corresponding uncertainty in the theoretical interpretation of data... 

Figure 11.2 A schematic of the electrospray process, showing the release of charged droplets from the Taylor cone and the Z-spray arrangement with respect to the sample inlet, sample cone, and the subsequent path of the ions into the analyzer.

The coupling of a GLC column with the sample inlet system of a mass spectrometer is relatively easy, as the effluents are already in gaseous form. The main problem is the relatively high pressure at which these effluents reach the spectrometer and the excess of carrier gas in the stream. Several experimental devices now allow separation of the sample from the carrier gas, either by an effusion process or with the help of a thin, semi-permeable membrane222,353. The use of capillary columns permits direct insertion of the GLC effluent into the ion source without overtaxing the pumping capacity of the mass spectrometer 311 3 5 5 >3 5 6. 

The overall diagram of a fast atom bombardment ion source is fairly simple. It consists of three main elements i) an atom gun, ii) a sample inlet, and iii) an ion extraction system. The atom gun is made up of an evacuated chamber that encloses a plate to which a high voltage potential (nominally 8 kV) is apphed. The gas to be used for the "bombardment" is allowed into the chamber, through an appropriate inlet, where it is ionised by the high potential plate (see equation (22)). The ion beam so created is repelled by the same plate (at 8 kV) and, to a certain extent, regains its neutral character by electron-capture or by charge-resonance processes such as those exemplified by equations (23) and (24). 

Measure entrained air - Use a portable EOT to sample inlet/outlet of key process equipment. 

Figure 19.1 is a block diagram of a typical process analyzer system, consisting of a sample collection and conditioning system, sample manifold, sample inlet, ion source, mass analyzer, detector, and a data analysis and output system that interfaces with the process control system. The dashed line indicates the parts of the overall system that are considered to comprise the analyzer itself (i.e., what is normally included when one purchases a process MS). Figure 19.2 is a photograph of a commercial process MS that incorporates these components. Aspects of these various components are described below, with emphasis on how they are applied in a process mass spectrometer. 

The process of choosing the type of mass spectrometer (including the sample inlet system) and operational conditions (experiments) to be undertaken to analyze a sample is based on several factors, including the molecular mass and polarity of the analyte(s) and the complexity of the sample mixture. The information sought, be it structural or quantitative (or both), also influences the selection of instrument and experimental setups. 

Plant engineers shall not use very long sampling lines for fluids. Truly representative sample shall be drawn from process/from inlet and exit of effluent treatment plant for correct results in real time ... 

Process sampling campaigns were focused on inlet gas streams, mercury removal unit outlets, treated gas, acid gas and sales gas. The results were used to identify process areas with increased potential for mercury exposure during maintenance events. Sampling methods used for the determination of total mercury (THg) in gas phase streams, were based on the USEPA Methods 30B and EPA 1631 and EPA 1669. 

The selection of process sample points in each facility was based on a review of the plant process flow diagrams, P IDs, and field verification of the presence of appropriate sample probe insertion valves. In general, samples were collected at the inlet to the plant and from downstream points as deemed necessary based on plant operations and processes. 

Results from the analysis of personal exposure samples during the inlet filter change out event indicated that mercury concentrations in worker breathing zones exceeded the AL and the TLV. Results from the analysis of samples collected during the pipeline scrapper receiving event and the area monitoring of the evaporation ponds indicated all mercury concentrations that were below the AL. Results from the analysis of process samples are presented in the following table ... 

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