Methods Used For Magnesium - Essay Example

Methods Used For Magnesium 1.0 Analytical Chemistry of Magnesium Magnesium was discovered by a farmer at Epsom in England in 1618, the substance was then called Epsom salt due to its bitter taste and healing power. It was later recognised to be hydrated magnesium sulphate MgSO4. In 1808, Sir Humphry Davy produced magnesium in metal from by electrolysis of magnesia and mercury oxide. In 1831, Antoine Bussy produced magnesium in coherent form and suggested the name magnum, which later turned into magnesium (Avadesin& Baker, 1999). Magnesium is an alkaline earth metal, belongs to second group of s-block of periodic table and is on the left side of the table. Magnesium is represented by “Mg” and has an atomic number of 12. The atomic weight of magnesium is 24.3050(6) and atomic volume of 14.0 cm3/mol. The electronic configuration is s2 2s2 2p6 3s2. Generallyexhibits HexagonalClose-packed latticestructure. The lattice dimensions of Magnesium at 25C are Side length=0.32092 nm Height=0.52105 nm. At room temperature, actual c/a ratio reaches 1.6236 where magnesium becomes almost closely packed(Magnesium, 2000). It contains two electrons in the outer shell and being looses them in order to form a positive ion in closed shell such as Mg+2. The energy level of magnesium is 3 as: First energy level 2 Second energy level 8 Third energy level 2 Figure 1: Electronic configuration of magnesium Magnesium is silvery white or greyish, lightweight and strong metal. It is highly flammable metal and tarnished when in contact with air; therefore, it develops a thin layer of oxide. Magnesium is abundantly present on both earth crust and seawater due to its high solubility. However, magnesium is not present as free metal because of its reactive property (Gupta & Sharon, 2011). Magnesium has density of 1.738 g.cm-3 at 20C. The melting point of Mg is 650C and its boiling point is 1107C. It has a heat of fusion of 8.48 kJ·mol−1 and its heat of vaporisation is 128 kJ·mol−1, whilst its molar heat capacity is 24.869 J·mol−1·K−1. Magnesium is a strongly basic oxidant.Other atomic properties of Mg include its electronegativity of 1.31 (Pauling Scale), atomic radius of 160 pm, and covalent radius of 141±7 pm (Magnesium Facts, 2012). Moreover, magnesium is paramagnetic is nature and its other mechanical properties include Young’s Modulus of 45GPa, Shear Modulus of 17GPa and Bulk Modulus of 45GPa. The hardness value of Magnesium is 260MPa based on Brinell Scale. The oxidation number of magnesium is +2 and is been found in number of compounds. Magnesium Oxide, also called magnesia, is the second most abundant metallic oxide in the earth after Aluminium Oxide. Other forms of magnesium in compound state include hydrated magnesium sulphate (MgSO4.7H2O), also called Epsom Salt. Magnesium compounds also include Magnesium Carbonate and Magnesium Fluoride (Willett, 2007). Dolomite, magnesite, brucite, carnallite, talc and olivine are the main commercial sources of magnesium. Due to the presence of Mg+2 ions, seawater is considered another major source of magnesium. Magnesium hydroxide precipitates can be formed by adding calcium hydroxide in seawater for obtaining magnesium (Avedesian& Baker, 1999). MgCl2 + Ca(OH)2 → Mg(OH)2 + CaCl2 Brucite is insoluble in water and can be transformed into magnesium chloride when reacts with hydrochloric acid. Magnesium, then, can be extracted from magnesium chloride by electrolysis process. Mg(OH)2 + 2 HCl → MgCl2 + 2 H2O In electrolysis process, Mg+2 ion is transformed into magnesium metal by adding two electrons at cathode while chlorine ions are oxidised to chlorine gas by releasing two electrons at anode. Mg2+ + 2 e─ → Mg (Cathode Reaction) 2 Cl−→Cl2 (g) + 2 e─ (Anode Reaction) Magnesium has three isotopes (e.g. 24Mg, 25Mg and 26Mg) available in significant amounts with 24Mg comprising 79% of total magnesium. 28Mg is radioactive in nature; however, its usage in nuclear industry hs been limited due to its short life (21 hours). 2.0 Usage and Level of Magnesium in Different Types of Samples Silicate rocks compose a major portion of earth’s mantle that is sufficiently rich in magnesium. It is also present in oceanic crust along with silica, typically known as sima, commonly in the form of iron magnesium silicate rocks, lying 5-10km deep in ocean basins. Magnesium burns with a white flame, which usually has s temperature of 3100C and a flame height of 300mm. It is typically used in manufacturing of fireworks and marine flares in powdered form. One of the main applications of magnesium include, removal of sulphur during production of iron and iron alloys and as a component in die casting of aluminium and in producing titanium. Magnesium has a wide range of applications in automotive manufacturing industry. Magnesium is used to manufacture magnesium alloy car wheels called mag wheels, which are generally known as aluminium alloy rims and wheel (Wei, 2005). Magnesium is also used extensively in making body parts and frames of high speed racing cars as an attempt to reduce weights of racing cars; however, risk of flammability and fire is still associated with this metal since this metal is highly flammable in its pure form. With the accelerated advancements in manufacturing technology, magnesium is becoming an integrated part in design and manufacturing of car engine blocks due to its light weight. For instanve, magnesium alloy AE44 and Corvette Z06,which are characterised by standing high temperature and low creep alloys, are widely used in manufacturing industry. Also, use of magnesium has tremendously increased in aviation industry due the reduced weight, resulting in saving fuel (Bray, 1989). Moreover, magnesium alloy (Elektron 21) has undergone a number of trial tests for its utilisation in engine and airframe parts. Another major use of magnesium is in alloying with aluminium in making beverage cans (Gupta & Sharon, 2011).In addition, magnesium is also used in sporting goods, nuclear industry, electronics, photography material and different types of tooling. Magnesium sulphate and magnesium hydroxide are mostly used as laxatives whileMagnesium borate, magnesium salicylate, and magnesium sulphate are mainly used as antiseptics (Nishizawaet al., 2007). On the other hand, magnesium stearate is used in pharmaceutical industry to prevent tablets from sticking to equipment during compression processes. Coating of magnesium phosphate is applied to woods for protection from fire,whereas, magnesium sulphite and magnesium hexaflourosilicate are widely used in paper industry and textile industry, respectively. Magnesium is present in lower proportions (0.03-3.2%) in terrestrial plants; however, its presence is usually associated with limiting the growth. Lately, (e.g. in late 19th century), Mg has been used as fertiliser;however,its present use is limited to maintaining the values of the pH in soil. Even though magnesium is sufficiently abundant in both plants and animals; yet half of world population is deficient in magnesium intake. In adults, human body contains 25g of magnesium (Widdowson et al., 1951), of which 60 percent is in hard tissues, 40 percent in soft tissues and one percent in blood under homeostatic control. Magnesium plays a vital role in over 300 enzyme reactions like protein synthesis and fatty acid metabolism necessary for ionic balance of human cells (Sareenet al., 2009). In fact, the human body has to work extremely hard to produce such a low proportion of magnesium for proper functioning. Dietary magnesium is digested and absorbed in small intestine, while it is excreted through kidneys in human body.Thus, gastrointestinal disorders like Crohn’s disease may limit the body’s ability to absorb magnesium. Spinach and other green vegetables are a major source of magnesium contained in centre of chlorophyll. Legumes, such as beans and peas, nuts, seeds, halibuts and cod fish, whole grains and unrefined grains are also a good source of magnesium in diet (Boyle & Long, 2010). List of selected source of magnesium in food is given below. Table 1: Sources of Magnesium in food. Source Milligrams per 100g Almonds 260 Spinach 60 Beef 22 Ham 20 Bran flakes cereal, ¾ cup 64 Peanuts 130 Potato 20 Hazel Nuts 60 Banana 40 Milk 27 Hypertension, heart problems and diabetes are usually linked to magnesium deficiency in human body. Magnesium plays a vital role in carbohydrate metabolism influencing the release of insulin in human body. Low levels of magnesium are mostly associated with Type 1 diabetes and hypomagnesaemia. Hypomagnesaemia may increase the resistance to insulin in diabetes patients. Thus, individuals with such condition need higher quantity of insulin to regulate and maintain body sugar level. During hyperglycemia, kidneys loose much of their ability to contain magnesium. This loss in magnesium results in or lowers levels of sugar in human body (Cohen, 2007). Furthermore, magnesium is very important for blood pressure regulationin parallel with insulin management in human body. This phenomenon increases the likelihood of cardiovascular disease in humans, increasing the probability of heart attack, as low proportion of magnesium is associated with the risk of abnormal heart rhythm. The risk of toxicity due to magnesium increases with the kidney failure conditions, as kidneys lose their ability to excrete excess magnesium from the body. Magnesium toxicity can also result from abnormally high intake doses of laxatives and antacids. Signs of magnesium toxicity are quite similar to those for magnesium deficiency and may include abnormal mental status, diarrhoea, losing appetite, breathing problems, low blood pressure and abnormal heart rhythm (Prasad &Oberleas, 1975). The pie chart below (Fig 3) presents analysis of different types of techniques reported during the period 2010-2012 for determination of magnesium. For this purpose, information was. Figure 3: Pie Chart Of Different Types of Techniques Used For The Determination of Magnesium (2010-2012). Where, in above pie chart (Fig 3) ICP-MS stands for Inductively Coupled Plasma Mass Spectrometry, LIBS for Atomic Emission Laser- Induced Breakdown Spectrometry, AAS for Atomic Absorption Spectrometry, ICP-AES for Inductively Coupled Plasma Atomic Emission Spectrometry, PIXEfor Particle Induced X-Ray Emission Spectroscopy, XRF for X-ray Fluorescence Spectrometry, NAA for Neutron Activation Analysis, IEC for Ion Exchange Chromatography, and AES stands for Atomic Emission Spectrometry. From the above chart, it can be seen that ICP MS(Inductively Coupled Plasma Mass Spectrometry) is the most commonly employed methods, followed by ICP AES (Inductively Coupled Plasma Atomic Emission Spectrometry), XRF (X-ray Fluorescence Spectrometry) and AAS(Atomic Absorption Spectrometry)for determination of magnesum. The main reasons for these methods being prefered by researchers is because of their efficiency and benefts of vis-à-vis cost associated. Similarly, the next pie chart presented in Figure (4) shows different type of matrices used for the determination of magnesium during the period 2010-2012. Figure 4: Pie Chart of Different Types of Matrices Used For The Determination of Magnesium (2010-2012) From the above pie chart figure, it can be seen thatthe majority of the studies focused on determination of magnesium in sample obtained from human blood followed by leaves and water; whereas, studies conducted in other areas compromise over 50 percentage of investigations conducted. 3.0 Determination of Magnesium in Biological and Environmental Samples The aim of this section was to discuss the analytical methods employed for quantitatively determining the magnesium in biological and environmental samples. The most commonly methods employed for biological samples are ICP MS, ICP AES and AAS, for instance, for detection of magnesium in blood serum, Inductively Coupled Plasma Mass Spectrometry and Inductively Coupled Plasma Atomic Emission Spectrometry has been mostly used. ICP AES has a detection limit of 4 μg L−1 and a percentage recovery of 97 percent, whilst ICP MS can detect magnesium in blood up to 0.007 μg L−1, a technique in which stable isotopes are used for better detection of the elements. Another technique, which is used for Mg determination in blood, is Atomic Absorption Spectrometry (Analytical Abstracts, 2012). Review of related literature and research articles revealed that both UV-VIS (Ultraviolet Visible Spectroscopy) and ICP AES (Inductively Coupled Plasma Atomic Emission Spectrometry) have detection limits of 0.06 ng mL−1 and 0.8 mg L−1, respectively. For detection of Mg in milk, Ion Exchange Chromatography, which has a detection limit in the range of 0.4-0.92 μg L−1, has been a preferable technique. Table (2) below presents a summary of methods used for detection and analysis of magnesium in biological samples. Table 2 : Summary of methods used for detection of Magnesium in biological samples Sample Matrix Preparation Method Analytical Method Detection Limit of Sample Percentage Recovery Blood Mg2+ and Zn-EDTA (Ethylenediaminetetraacetic acid disodium salt) in NH4Cl-NH3 buffer solutions ICP AES 4 μg L-1 97% Blood Chemicals enriched in one or more stable isotopes of an element are added ICP MS 0.007 μg L−1 No Data Urine 6 M HCl (40 of acid per 10 ml of IZS injection) and was diluted with water 10-fold UV VIS 0.06 ngmL−1 92% and 107% Urine Conditioned in Nitric Acid ICP AES 0.8 mg L−1 95% Blood 1 mg/L sodium dodecyl benzene sulfonate (SDBS) and 0.060 mol/L HCl AAS No Data 95.2% to 98.7% Milk Cation-exchange coating for stir bar sorptive extraction (SBSE) based on poly (acrylic acid-ethylene dimethacrylate) monolithic material IEC 0.4-0.92 μg L−1 71.1% to 102.8% Where, ICP-MS stands for Inductively Coupled Plasma Mass Spectrometry, AAS for Atomic Absorption Spectrometry, ICP-AES for Inductively Coupled Plasma Atomic Emission Spectrometry, IEC for Ion Exchange Chromatography, and UV VIS for Ultraviolet Visible Spectroscopy. Furthermore, the most commonly used methods for detection of magnesium in air are ICP AES and ICP MS, which have detection limits of 0.0047 - 1.2 ng.g-1 and 0.1 μg.m-3,respectively. Similarly, Ion Exchange Chromatography and Inductively Coupled Plasma Mass Spectrometry methods have been used to determine magnesium in water samples. Generally, Ion Exchange Chromatography has a detection limit of 0.89 μg.L-1, which is higher than that for ICP MS (e.g. 17μg.L-1). Once more, ICP MS is beingused for direct elemental detection of magnesium in leaves and plants (detection limit 0.04 and 26 μg g−1).inorder to detect magnesium and other elements in soil samples, ICP AES methods has commonly been used. In this method, sample is mixed with 4 ml HNO3/HClO4 (4:1) and 0.2-2 ml 40% HF to achieve a better detection limit of 0.3-45 μg.L-1 (Analytical Abstracts, 2012). Table (3) presents a summary of methods for detection and analysis of Magnesium in environmental samples. Table 3 : Summary of methods used for detection of Magnesium in environmental samples Sample Matrix Preparation Method Analytical Method Detection Limit of Sample Percentage Recovery Air Alkali melting to dissolve Si in atmospheric particles diaphragm ICP AES 0.0047 - 1.2 ng.g-1 96% Air Oxidized by UV irradiation (low-pressure mercury lamp), dissolved in nitric acid mist ICP MS 0.1 μg.m-3 No Data Water Ion chromatography with IonPac CS12A separation column and 16.8 mmol/L of HCl as eluent IEC 0.89 μg.L-1 No Data Water Tandem preconcentration method integrating chelating resin adsorption and La coprecipitation ICP MS 17 μg mL−1 Leaves Direct elemental analysis of green leaves ICP MS 0.04 and 26 μg g−1 No Data Leaves Based on special features of HR-CS-AAS AAS No Data 82-112% Soil Sample mixed with 4 ml HNO3/HClO4 (4:1) and 0.2-2 ml 40% HF ICP AES 0.3-45 μg.L-1 87.8-105% Where, ICP-MS stands for Inductively Coupled Plasma Mass Spectrometry, AAS for Atomic Absorption Spectrometry, ICP-AES for Inductively Coupled Plasma Atomic Emission Spectrometry and IEC for Ion Exchange Chromatography. 4.0 Review of Analytical Methods for Determining Magnesium Several methods have been discussed in the relevant literature for determination of magnesium. The most preferable analytical methods that are more frequently used in conducting research, as been observed from the analytical abstracts include: ICP-MS (Inductively Coupled Plasma Mass Spectrometry), AAS (Atomic Absorption Spectrometry) and ICP-AES f(Inductively Coupled Plasma Atomic Emission Spectrometry). Other methods include Ion Exchange Chromatography, and Ultraviolet Visible Spectroscopy, will be discussed later in thisassay. ICP methods have been employed to determine traces of magnesium in environmental samples. ICP techniques are basically initiatedby measuring wavelength that is specific to a particular element. Major advantages of this technique include its ability to measure a broad ranges and concentrations of elements except Argon, range of detection limit (1-100 g.L-1), rapid analysis in short time and requirement of very slight quantities of samples. Requirements of special facilities for handling radioactive plasma is stresses in many literature sites;yet, ICP can be effectively used to analyse sample of air, water and soil. ICP is mostly used with other analytical methods like atomic emission spectroscopy (AES) and mass spectroscopy (MS). By applying thesecombinations, the time required to prepare samples has been reduced significantly (Montaser, 1998). Mass spectrometry is an indispensable technique which been employed very frequently in chemistry, medicines and other related fields of sciences. The purpose of this technique is to identify a substance from the molecular or atomic mass of its elements. This information can be, then, used to calculate the mass of element present and the molecular formula of the compound. Major components of mass spectrometry include ion source, mass analyser and a detector. The basic principle is to produce ions from, either organic or inorganic samples, and to segregate these ions based on their mass to charge ratio (m/Q) to determine each element quantitatively and qualitatively. The mass to charge ratio is a physical quantity used in electrodynamics. It suggests that two particles having same mass to charge ratio would move along the same path in vacuum when subjected to same electric and magnetic field. Some literatures use charge to mass ratio (Q/m) instead which is a multiplicative nverse of mass to charge ratio (m/Q). Unlike nuclear magnetic resonance and infrared spectroscopy, mass spectrometry is a destructive method and consumes sample during the examination process (Hoffman &Stroobant, 2007). However, the amount of sample consumed is being ignored,as this technique is most effective when others fail to analyse sample amounts of nanograms.ICP MS, an advanced form of MS, is a sensitive technique that can determine elements particles in ranges of parts per trillion. It is a combinative approach to inductively coupling plasma for ionisation with mass spectrometer for detecting particles. Inductively coupled plasma contains sufficient amount of ions and electrons for making gas electrically conductive. The plasma, used in this instrument, is essentially neutral as they contain equal amounts of ions and electrons in a unit volume. In order to couple this inductive plasma to mass spectrometer, ions from plasma are introduced into mass spectrometer through a series of cones. These ions, then, are being segregated on the basis of mass to charge ratio and signal produced (specific to the element and its concentration), which is then received by a detector. For magnesium,its detection limits associated with ICP based techniques is 0.1 ppb. ICP MS has the ability to segregate gas-ionised atoms and molecules on the basis of mass charge ratio. Another advantage of this method is its ability to detect broad range of elements at a very low detection limit (i.e. at part per billion level where majority elements can be traced to parts per trillion using this technique). However, disadvantages of ICP MS include its inability to detect non-metallic element and that oxygen, hydrogen, argon and nitrogen may combine during this application (Montaser, 1998). AES technique uses light from a flame, arc or spark source at a specified wavelength to determine elements quantitatively in a sample. The identity of the element is determined by wavelength of the emitted spectra; whereas,its quantity is a function of intensity of light emitted. In this method, heat is required to break chemical bonding and produce free atoms, which are excited by absorption of light energy. When these atoms return to ground states they emit light at a specific wavelength, dispersed by a prism and detected by spectrometer. This technique has been mainly employed in alkaline-based metals and in pharmaceutical industry. Another approach to this method uses inductively coupled plasma to excite atoms, whichhas improvedthe detection limits, multi element determination ability and reduced interference (Miller et al., 2010). On the contrary, disadvantages of this technique are spectral interferences, restriction sample in solution and high associated costs. ICP AES (Inductively Coupled Plasma Atomic Emission Spectrometry) is aimed to improve detection of elements by resolving limitations associated with AES alone. It uses inductively coupled plasma to excite atoms and ions that emit radiations at wavelengths specific to an element in the sample. It is combinative approach to ICP and AES (Hiller, 2006). Moreover, ICP AES has a good ability to detect structure of elements in the sample with greater precision. In this technique, high energy is used to burn analyte, which emits light of colour and wavelength specific to an element. In contrast, as mentioned earlier, major disadvantages of this technique include high possibility of interference, inability to analyse oxygen, hydrogen, nitrogen and carbon, and high costs associated with this technique. Another technique UV-VIS (Ultraviolet Visible Spectroscopy) is also used for determination of magnesium in environmental samples. This techniques employs use of light in visible, near ultraviolet and near infrared spectrum range for adsorption purpose. The absorption or reflectance of certain colour in the visible range of spectrum is specific to chemical composition of the sample under analysis. This technique is different from fluorescence since it involves absorption measures from ground to excited state as compared to the later. The underlying principle is that molecules containing electrons can absorb light in visible and ultraviolet range and to move to higher orbits. The more easily the electrons are excited, the longer the wavelength light they can absorb. UV-VIS Spectrometry can be used to determine the magnesium quantitatively in organic compounds such as DNA, RNA and protein as these compounds exhibit high degree of conjugation and can absorb ultraviolet and visible light in electromagnetic spectrum (Workman & Springsteen, 1998). Ion Exchange Chromatography is also been used to analyse samples of proteins and other charged molecules for presence of magnesium and other elements. In cation exchange chromatography, positively charged molecules are attracted to negatively charges solid support where as anion exchange chromatography is vice versa. An important aspect of this technique is its ability to concentrate a bound component by reducing the sample volume and increasing the sample concentration. Salt concentration, salt type, pH value and selection of appropriate resin mode would allow to control both binding and elution selectivity (Small, 1989). This technique is more effective with samples containing charged molecules of magnesium and any other element. AAS (Atomic Absorption Spectrometry) has the capacity to measure concentrations of about 70 elements in a detection limit range from ppb to ppm. It is mainly used to determine concentration of elements using absorption of optical radiation by free atoms in gaseous form. It can be used to determine the elements in solutions and in solid state. The technique uses absorption spectrometry to analyse the concentration of an element in the sample. The electrons in a sample are energised to move to higher orbits thus releasing certain amount of energy, which exhibits wavelength specific to an element (i.e. each element in nature have its own wavelength). The radiation flux in the equipment, generally called atomiser, is measured before and after placing sample through a detector, and the ratio between two values called absorbance is used to determine the concentration of each element present (Cantle, 1982). Beer-Lambert Law forms the basis of this technique. Atomic absorption spectroscopy is used to measure total concentration of magnesium in any biological sample. It is mainly a destructive method and requires breaking the sample in acids to prevent clogging. For optimum accuracy, limitations for determination of magnesium include volume of at least 2ml and concentration range of 0.1 - 0.4 mol/litre (Dean, 1997). A limitation of this method is its inability to distinguish between Mg+2 already present in the cell and the one consumed during experimentation. This is mainly due to chemical interference resulting from lack of absorption atoms when the flame is not sufficiently hot enough to decompose the molecule as in case of phosphate interfering magnesium which can be overcame by adding lanthanum. Instead, mass spectrometry and atomic emission spectrometry are methods that can be employed to measure total quantities of magnesium; however, these are quite expensive than the above discussed techniques. Advantages of AAS include its greater detection limits and the ability to detect elements that do not interfere with absorption wavelength of analyte. However, major disadvantages include limitation of detection of one element at one time, inability to directly analye solid and gas samples and the non-linearity of the calibration curves when absorbance becomes higher than 0.5 to 1. In the following section, the latest developments in application of above discussed techniques in determination of magnesium in environmental, biological and metallurgical samples are discussed. 5.0 Recent Developments Techniques for detection of magnesium have developed in recent part so as to support research application in areas of environment and biological research. AAS, ICP MS, ICP AES and IEC (the above-discussed techniques)have been widely utilised to determine magnesium quantitatively and qualitatively. Studies conducted by many researchers show how these techniques are under continuous process of evolution and development, which improved applicability of these techniques in varying fields and experimental conditions (Theophanides and Anastassopoulou, 1997) The majority of calcium and magnesium is stored in human bones and only meagre proportion (e.g. less than 1%) is present in blood. Balanced amount of magnesium in body is essential or human body to survive. Nuclear Magnetic Resonance in which electromagnetic radiations are absorbed and re-emitted from magnetic nuclei is used for this purpose. These electromagnetic radiations are at resonance frequency specific to an element and depend upon strength of magnetic field and isotopic properties. Latest developments include multi-dimensional Nuclear Magnetic Resonance Spectroscopy, where pulses of varying shapes, frequencies and durations are used to extract diverse information about molecules. Neutron Activation Analysis is one of the techniques used in Nuclear Magnetic Resonance Spectroscopy. In a recent study, Zambooniet al.(2012) used neutron analysis technique to determine calcium and magnesium in human body indicative of sex and age to investigate heart diseases in Brazil.In a different study, Xiao et al. (2012) used the NAA technique in combination with PIXE (Particle Induced X-ray Emission Spectrometry) to study the sources of air pollution. They sued on nucleopore films using a Gent stacked filter unit. Black carbon was detected by using a reflectometer, while magnesium was determined using by Particle Induced X-ray Emission Spectrometry technique in combination with NAA. Su et al. (2012) studied brain metals using an online microdialysis-in-loop solid phase extraction-inductively coupled plasma mass spectrometry system. In this study, non-functionalised small-bore polytetrafluoroethylene (PTFE) sample loop was used as preconcentrator. An online automatic in-loop microdialysis system together with Solid Phase Extraction and Inductively Coupled Plasma Mass Spectrometry was developed. Selective polymer ion interaction was employed to extract salt matrix after pH value was adjusted. The next phase required no preconditioning after treatment with nitric acid. This method exhibited very low detection limits in range of 0.003 to 0.5 μg L−1 and percentage recovery of 90 to 98 percent. Takatsu et al. (2011) developed another method for introducing sample in ICP MS technique. The method included an inert loop injection unit, a high performance concentric nebuliser (HPCN) attached to a temperature controllable cyclone chamber. The injection loop is washed with 0.1M nitric acid solution. In a different study, Carvalhoet al. (2011) used Captivity Coupled Contactless Conductivity (C4D) for detection of metals in mineral and phytotherapeutic formulations. In this technique, electrolytes based on 30 mmol L−1 2-N-morpholinoethanesulfonic acid (MES)/histidine, 1.5 mmol L−1 18-crown-6 ether, and 1mmol L−1 citric acid (pH 6.0) were used as additives for migration of cations. In a similar recent study, Huang et al. (2011) used Stir-bar Sorptive Extraction based on poly (acrylic acid-ethylene dimethacrylate) monolithic method in ion exchange chromatography. Most recently, Vaggelliet al. (2012) used μ-XRF technique to detect elements in archaeological materials. The method was based on non-destructive approach for the analysis using commercial μ-XRF Eagle III-XPL. The method improved accuracy for elements having concentration greater than 100ppm by weight. For a rapid determination of magnesium concentration in drinking water, Gurkanet al. (2009) employed a complex spectrophotometric method. The proposed method included using of Erichrome Black T (EBT) in presence of N-cetyl-N,N,N-trimethylammonium Bromide (CTAB). The complex reaction occurs between EBT and magnesium in presence of NH3/NH4Cl is being stable for more than six hours. In this technique, N-cetyl-N,N,N-trimethylammonium Bromide and Triton X-100 are used as cationic and nonionic surfactants, respectively. This method can effectively be employed to determine the magnesium even at trace level in drinking water. Recently, a new method called Raman Spectroscopy has been devised for the same purpose (e.g. determination of magnesium chloride concentration in water). In this method, laser is focused on electron cloud, which creates a short lived unstable state; as a result radiations are emitted immediately. In this technique, spectrum called Raman Spectrum is achieved by separating the scattered energy from laser energy, and can be seen as a shift from exciting energy. This spectrum is used to determine the concentration of each element present in the compound. Marques et al. (1990) used this technique to determine the concentration of magnesium and aluminium in water and deuterium oxide. They obtained Raman spectra of aqueous solutions of AlCl3 and MgCl3 in water and were able to relate the shapes of Raman bands to cation hydrates oscillations with more accuracy. Recent developments in mass spectrometry has led to a new advanced method called Desorption Electrospray Ionisation, which is performed at atmospheric pressure and ionises gases, liquids and solids in open air. It is combination of desorption and electrospray ionization methods. 6.0 Conclusions As discussed earlier, a number of methods can be employed to determine magnesium qualitatively and quantitatively. Each method has its own specificity and can be best utilised under a certain set of experimental conditions; like environmental, metallurgical and biological samples. Mass spectrometry and atomic emission spectroscopy are the most widely used methods. It has also been noted that concerns about applicability of analytical methods focus on the areas of detection limit, sensitivity, multi elemental detection and interference. Future studies may be enabled to improvise better techniques to improve detection limit and sensitivity and decrease or eliminate interference of other elemental spectrum with that of magnesium. Very little information is currently available on the activity of magnesium, thus concentration of free magnesium has been determined in order to approximate the magnesium activity. It has been noted that the majority of the reported studies have dealt with total magnesium rather than their states in any compound samples. Thus,future studies ought to be enabled to determine the concentration of each state of magnesium (e.g. liquid, solid and gas) in any sample under investigation. References Avedesian, M. and Baker, H. (1999).Magnesium and Magnesium Alloys. New York: ASM Press. Boyle, M. and Long, S. (2010).Personal Nutrition. New York: WadsWorthCengage Learning. Bray, D. (1989).Magnesium Alloy Technology for Aerospace Applications. Great Britain: Defense Technical Information Centre. Cantle, J. (1982).Atomic Absorption Spectrometry. New York: Elsevier Scientific Publishing Company. Carvahlo, M. (2012). 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