Mass Spectrometer Design - Essay Example

al affiliation This research paper reports the fundamental design process of a mass-spectrometer for use in detecting/uncovering/ identifying illegally trafficked drugs in airports. In the report, specific design as well as its rationale is described meticulously such that an experienced technician, without more allusion to the design engineers themselves can build the machine for the above-mentioned purpose as well as gain insight into the design as well as the function of a mass spectrometer. The mass spectrometer is projected to identify smuggled drugs by perceiving ion concentrations of shared elements for all the drugs as well as, once detected these chemical elements will be matched with a catalogue of chemical compounds; an illustration of this process is described in the report as well as an assessment on the limitations, design specifications, besides recommendations for enhanced dependability. Keywords: Mass spectrometer, Design 1. Introduction Basically, a mass spectrometer performs three important roles (Figure 1). Initially, it bombards the molecules to be analyzed with a stream of high-energy electrons, transforming a number of the molecules to ions, which are then fast-tracked in an electric field by a sequence of polarized fast-tracking plates, a huge potential difference (p.d), oscillating from 1 to 10 kV (kilovolts), applied across these fast-tracking plates yields a beam of briskly roaming positive ions. Moreover, one or more focusing slits subject the ions into a uniform beam. What is more, majority of the sample molecules do not undergo ionization, nonetheless, are incessantly drawn off by vacuum pumps which are linked to the ionization chamber; whereas some of the molecules are changed to negative ions by the absorption of electrons. Consequently, the repeller plates engross these negatively charged ions. Besides, a number of the positively charged ions which are produced can possess a charge greater than one (a loss of in excess of a single electron). These are fast-tracked in a similar way as the singly charged positive ions. Secondly, the fast-tracked ions are isolated consistent with their mass-to-charge ratios in an electric or magnetic field by a deflection that transpires through an applied magnetic field. Finally, the ions that have a specific mass-to-charge ratio are identified by a detector device which can tally the number of ions reaching it that have negotiated the static-curved radius of arc because of the applied magnetic field (Figure 2). Additionally, particles with mass-to-charge ratios which are both too large as well as too small hit the sides of the analyzer tube; hence do not reach the detector device. For that reason, either the fast-tracking voltage or the magnetic flux is constantly changed so that all of the ions formed in the ionization chamber can be identified/ detected. The detector’s yield is magnified and fed to a recorder and reliant on the ions’ angle of deflection it ultimately defines the mass of the ions and plotted proportionally with the number of ions that strike the detector in a graph to define the chemical formulae of the inserted sample compound. The trace from the recorder is a graphical representation of the number of particles identified in terms of mass-to-charge ratio i.e. a mass spectrum. In contemporary instruments, the yield of the detector is fed to a computer through an interface. The computer can afford the output in both graphic as well as tabular forms, store the data, as well as match the data to standard spectra, which are located in spectra libraries also stored in the computer. Mass spectrometers are as a result frequently used in functions involving evaluation of unidentified compounds, identification of molecules within in a sample, quantification of known compounds, as well as determination of the amount of specific molecules by evaluating the mass-to-charge ratio of charged particles. The particulars of the mass-spectrometer as designed here are provided in section 2. The final design is given in section 3. That counts the diagrams of the whole instrument with labels indicating all measurements, a catalogue of all main parts needed, particulars of all main electrical parts counting the currents as well as voltages needed, specifics of the magnetic as well as electric fields used and of every subsystems utilized to produce those fields. Section 4 comprises the illustration of calculations showing the operation of the device for two diverse atomic species. In addition, transitional outcomes are given at strategic points in the calculations so that the mode of calculation can be effortlessly verified. A table of all formulae applied in the calculations is provided in appendix A together with an explanation of the rationale for which each is used. Section 5 comprises a list linking the performance as well as characteristics of the device alongside the original provisions. Section 6 comprises a deduction stipulating how meticulously the specifications were met or by how far they were surpassed. Figure 1: Diagram illustrating the basic functions as well as parts of a Mass Spectrometer Figure 2: Diagram displaying the curvature obtained from a magnetic field as well as its resultant scatter pattern to the detector reliant on mass-to-charge ratio 2. Specifications To establish the specifications of the mass spectrometer it is essential to ponder what chemical substances need to be detected/ identified, in this mass spectrometer’s instance; the illegal drugs that are frequently smuggled into the country. Upon inspection it can be established that all illegal drugs share common elements whether they be substances including or within: opiates, cannabis, modafinil, cocaine, MDPV, amphetamines, tryptamine (LSD), MDMA, tranquilizers, psilocybin mushrooms, as well as more contain elements Carbon (C), Nitrogen (N) Hydrogen (H), as well as Oxygen (O). As a result, the mass spectrometer will be designed to principally sense these elements. Furthermore, a crucial limitation to contemplate is that when an electric field, E, is bombarded to an insulating material, it might bear conduction of current until enough voltage is applied to facilitate conduction; i.e. the dielectric interruption of air (air, being the insulation inside the acceleration chamber of the mass spectrometer). Consequently, air is thought of as a good insulator having a resistance to interrupt at an electric field strength of 3*106 V/m nonetheless, it is imperative to consider as enormous voltages may be applied in this instrument as well as keep the electric field well below this value (keeping in mind that this value also is reliant on the distance between plates in the acceleration phase); the electric field applied to this device’s design was 8000V/m which is inside what is needed to fast-track ions in a mass spectrometer: 1000-10000V/m. Still, at the deflection phase of the mass spectrometer there is a solenoid utilized to generate a magnetic field; implying that the saturation at which the magnetic material (coil) transpires ought to be deliberated. Magnetic saturation is a state that is reached when an increase in applied magnetic field, H, cannot increase the magnetization of the material anymore, therefore, the sum magnetic flux density, B levels off and is tracked by a swift drop in H. For that reason, as this is unwanted for the part as the solenoid; the copper wire to be utilized in the design will be eliciting magnetic flux intensity well below the 1.6T that is the capacity (saturation point) for copper. Likewise, central to the mass spectrometer design process is utmost compact dimensions conceivable, which is additionally analyzed in the report as it depends mostly on the calculations comprising the specifications defined above. A suggested design for form factor is that of 0.70m * 0.55m * 0.30m (length*width*depth correspondingly). 3. Design Figure 3: Diagram illustrating the approximate internal design of important components for building the mass spectrometer and relevant sections Figure 4: Table of basic design specifications for the particular design of the mass spectrometer in this report Mass Spectrometer component Proposed specification(s) Power requirements 240VDC Current required for system 1-7.5A Number of plates 2 Plates Accelerator plate distance 0.03m Electric field, E 8000V/m Magnetic flux density 0.0299-0.1771T Radius value, r 0.1m Type of solenoid Air-Core Solenoid height 200 turns Ion chamber dimensions 0.01m Mass analyzer box(with electromagnet) 0.40m *0.45m * 0.20m Entire system dimensions 0.70m * 0.55m * 0.30m Number of turns of solenoid 200 turns 4 Calculations The following formulae rearranged, show how a relationship was derived that can be used to predict the mass/charge ratio of ions arriving at the; using Lorentz’ force equation, Newtonian laws of motion and Cyclotron theory in relation to the ionization/acceleration/deflection stages of the mass spectrometer: By combining Lorentz’ equation and Newton’s centripetal force equation: Read More