Abstract
Crystallization of L-alanine crystals can be achieved through the use of Meta-assisted and Microwave Accelerated Evaporative Crystallization (MA-MAEC) process. This is a common industrial technique that has the capacity to produce crystals with different polymorphs within a very short time, unlike other preparation methods. MA-MAEC crystallization technique poses myriads of chemical properties and hence it becomes easy to measure and determine the temperature gradient for every compound. In an actual sense, it helps in determining the crystal growth rate and identifying necessary conditions for achieving a particular morphology. For instance, research has shown that some additives can be added to solutions to obtain a particular molecular size and structure. The paper offers a succinct literature review of the crystallization process.
Introduction
Crystallization is a process whereby solid compounds are purified (Alabanza, Mohammed & Aslan, 2012). It is a fundamental technique that chemists and industrialists use to separate compounds made up of solids and are more soluble in hot water. When the solute or compound is boiled in a hot solvent, it easily dissolves. Once the solution cools down after the loss of heat energy, pure compounds in form of crystals are recovered in the process. Research has shown that this method does not eliminate all impurities from crystals. Impurities can be removed through filtration or any other convenient technique (Pinard & Aslan, 2010). There is no actual scientific description of how crystallization occurs. Nevertheless, the entire process relies on a mixture of art and scientific skills. This process is natural and therefore widely used by chemical engineers to perform the Metal-assisted and Microwave Accelerated Evaporative Crystallization (MA-MAEC) procedure (Pinard & Aslan, 2010). The latter refers to a procedure whereby highly soluble proteins (L-leucine) are dissolved in a solution (L-alanine). The mixture is then heated by a microwave above room temperature. Alabanza, Mohammed, and Aslan (2013) compared such an experiment with another one carried out at room temperature (controlled procedure). Observations and research evidence revealed that the experiment carried out at a higher temperature led to the formation of large and pure crystals.
Literature Review
Crystallization is considered by scientists as an important tool useful in preparing and understanding the structure of a molecule. It is crucial to mention that crystallization technique ensures the production of high quality crystals that may also be pure to some extent. The use of metal-assisted and microwave-accelerated evaporative crystallization (MA-MAEC) technique is perhaps the best method in crystallization. MA-MAEC is a faster method of crystallizing substances. In addition, it is a selective method for preparing smaller molecules. Using the MA-MAEC method, a scientist can rapidly create a glycin model within a couple of seconds. However, the latter depends on the desired size of crystals being formed. Most importantly, glyciin crystals appear quite large when prepared on silver nanostructures even in the presence of moderate heating in a microwave.
Crystal engineers widely use crystallization technique to obtain molecular solids with specific chemical and physical properties (Alabanza et al., 2012). Mojibola, Dongmo-Momo, Mohammed and Aslan (2014) highlight that crystal engineers apply and design the technique in such a way that they are able to obtain molecular aggregates with the desired morphology. Therefore, it is important for such engineers to understand the growth kinetics and implications of crystallization in order to use the process for large-scale production of industrial materials. Pinard and Aslan (2010) confirm that in order to obtain the desired crystal morphology, it is fundamental to select an appropriate solvent. Mojibola et al (2014) elucidate that there are numerous solvents that can be used for MA-MAEC-based crystallization.
In a study conducted to examine how amino-acids crystals can be obtained from various chemicals, Alabanza et al (2013) concluded that the application of MA-MAEC technique increased the development of amino acid crystals. Pinard and Aslan (2010) admit that the MA-MAEC technique also reduces the time taken for crystals to grow. Mojibola, et al (2014) highlight that despite the differences in temperature and solvents used, the crystal anatomy or structure remains unaltered. In other words, the crystal structures for room temperature experiments are similar to those of experimental procedure carried out at higher temperatures. However, if the desired solvent is not available, other types of solvents can be used but with the inclusion of additives (Pinard & Aslan, 2010).
Numerous experimental studies have been done to examine the effects of additives on crystallization process. Alabanza et al (2013) used a crystallization procedure whereby L-alanine (solvent) was altered with additives. After careful analysis of the outcome, Mojibola et al (2014) noted that crystals that were grown without additives appeared smaller in size with several and well-developed faces. On the other hand, large-size crystals were obtained when additives were made part and parcel of the ingredients during the preparation process. Upon thorough review of the experimental analysis, it is evident that though the crystals portrayed differences in size, they had similar peaks (Pinard & Aslan, 2010). This implies that MA-MAEC can widely be used for multiplexed development of Amino acids crystal whereby additives are added to obtain the desired morphology (Alabanza et al., 2012).
Evaporative crystallization has widely been used in industrial processes to purify molecules. However, it has been overtaken by MA-MAEC technique. Research has shown that due to advancement in science and technology, there are newly synthesized molecules and drugs that require highly sophisticated methods of purification (Pinard & Aslan, 2010). This explains why MA-MAEC has been widely used bearing in mind that it allows chemical engineers to obtain the desired size of crystals within the required timeline. In actual sense, MA-MAEC is a more efficient and innovative method of crystal growth and characterization. As a matter of fact, this technique can be carried out within seconds. Crystals made up of compounds such as L-alinine and glycine can be made pure using the latter method.
Mohammed et al (2014) observe that there has been an increasing interest by industry players to implement a controlled-crystallization technique that can facilitate crystal polymorphisms. The key idea is to ensure that industries are able to synthesize crystallized drugs with the desired forms such as tablets or pills (Pinard & Aslan, 2010). Moreover, there has been a desire to synthesize drugs for animals, plants and human beings in the purest forms possible. In order to achieve this initiative, some industries have been using the polarized laser light irradiation in synthesizing diverse forms of glycine polymorphs (Pinard & Aslan, 2010). Other manufacturers apply the Assembled Monolayer’s (SAMs) technique to obtain thin films of glycine. These techniques have collectively been referred to as the proof-of-principle crystallization (Mojibola et al., 2014). However, all the identified methods have eventually been replaced by MA-MAEC since they are not able to effectively produce the desired shapes of biological and organic molecules.
Crystallization is indeed a valued technique of preparing crystals. The scientific world values the process as an important process that can be sued to study and understand molecules and their structures. For example, Mohammed, Syed, Bhatt, Hoffman and Aslan (2012) point out that primary molecules necessary for this process include both amino acids and protein molecules. It is imperative to highlight that all molecular crystals are significant in biological process. However, Pinard, Grell, Pettis, Mohammed and Aslan (2012) posit that the stabilizing and solubility properties increase the importance of both proteins and amino acids in recognizing their biological significances. Additionally, proteins and amino acids in biological functions can serve as final products as well as intermediate materials crucial in the crystallization process. Moreover, both substances can be used in several processes that take place in the pharmaceutical, cosmetic, food and chemical industries.
Grell, Pinard, Pettis and Aslan (2012) are emphatic that developing an understanding of in-vitro and in-vivo behavior of biological molecules is prudent in determining the structure of a crystal. They analyze various techniques which scientists employ in crystallization. The researchers also link the functional contribution of organic and biological molecules in the process of crystallization. Furthermore, they point out that in order to crystallize amino acids in solutions, it is crucial to restrict the process towards the production of high quality and large crystals. On the same note, Mohammed et al (2012) affirm that polarized laser light irradiation is one of the most reliable techniques that may be used for the desired process. This method is indeed effective in crystallizing amino acids in a solution. Another method suggested by Alabanza and Aslan (2011) is the use of micro-droplet solvent evaporation on self-assembled monolayers (SAMs). In this case, polymorphs can be prevented from forming on specific surfaces through the application of Nanoscale cylindrical pores.
Recent studies have conformed l-Alanine as one of the most significant amino acids contained in most proteins. It plays a very important role in developing the structure of proteins (Mohammed et al., 2012). According to Pinard et al (2012), the chemical protein has numerous applications in the chemical, pharmaceutical and food industries. As a result, the chemical enjoys a relatively high market demand. Initially, scientists used traditional methods of evaporative crystallization for crystallization process. However, the conventional method was finally ruled out as a time-consuming process. Scientists further indicated that traditional methods failed to yield usable crystals coupled with consumption of extra time and poor results after the experiments. These challenges necessitated the application of MA-MAEC methodology. The technique is deemed to be cost-effective because the prevailing immediate temperature may be used to prepare crystals. This technique is highly effective because it generates l-alanine crystals that are larger and properly shaped. As it stands now, industries are using the same technique to produce large amounts of molecular crystals. According to Pinard et al (2012), the technique can be used in different processes including preparing large crystals using organic molecules.
The knowledge on crystallography has facilitated thorough understanding of molecular structure. Protein and amino acids alongside other molecular crystals have been vital towards successful understanding of molecular structures. According to Grell et al (2012), the latter can be attributed to the unique properties such as high stabilizing and solubility properties. These properties aid in creating proteins that are more distinctive. Metal-assisted and microwave-assisted evaporative crystallization (MA-MAEC) is a platform through which technology functions by combining both microwave heating and the application of silver nanoparticles in a crystallization process.
In particular, the MA-MAEC technique is a faster method of crystallization and quite selective when there is need to prepare smaller molecules. Mohammed et al (2012) is emphatic that by using MA-MAEC method, a scientist can rapidly create a glycin model after a short while. In other words, one of the positive attributes of this technique is minimal time consumption. However, it will depend on the size of structures being formed. It is also vital to reiterate that glyciin crystals appear quite big when grown on silver nanostructures even without the application of heat from a microwave. This implies that the process or technique is also cost effective and can significantly benefit large-scale manufacturers of crystals. According to the illustration in the diagram below, glycins that have been grown in blank glass slides appear to be quite smaller than the heated ones. This explains why both Mohammed et al (2012) and Alabanza and Aslan (2011) concur that MA-MAEC technique is crucial in determining the size of a crystal and time needed for the formation of desired polymorphs. It is more effective than the conventional evaporative crystallization.
In their publication, Alabanza, Pozharski and Aslan (2012) comprehensively articulate the process of forming crystals using the MA-MAEC technique. They assert that it is possible to make specific shapes of l-Alanine through this process. The method entails crystallization the compound through an intensive heating process. The method is relatively effective when carried out on surface-engineered materials. Better still, sites targeted for the growth of crystals must be set up in advance. These are found on the selective nucleation sites. They are made using modified silver island films (SIFs). In concurrence, Grell et al (2012) mentions that during the formation process, creation of a thermal gradient is critical. As a result, microwave transparent medium is necessary so that a reliable source of heat can be available throughout the process. After heating the microwave, silver nanostructures and other solutions remain warm bearing in mind that this medium is important in the creation of thermal gradient.
Furthermore, it is pertinent to note that in the process of developing crystals, 11-mercaptoundecanoic acid (MUDA, 1-undecanethiol (UDET) and hexamethylenediamine (HMA) are used to modify or alter the functional nature of SIFs. This ensures that important elements such as the COOH functional groups and -NH2, -CH3 are introduced.
Conclusion
To recap it all, research studies have shown that crystallization process are continually evolving into a crucial industrial process. The process is currently being used to meet the demand for pure and diverse forms of biological and organic molecules used to synthesize drugs. From the above discussion, it is evident that additives play a vital role in crystallization bearing in mind that they facilitate the formation of different sizes and structures of molecules. Using sophisticated technology such as MA-MAEC to obtain crystals saves time and equally facilitates the formation of pure compounds.
The MA-MAEC technique crystallizes l-Alanine. Besides, the crystallization process can be accomplished at room temperature and engineered surfaces. Adhering to the whole process ensures the production of quality crystals.
References
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