V. K. Unnikrishnan

Bio: V. K. Unnikrishnan is an academic researcher from Manipal University. The author has contributed to research in topics: Laser-induced breakdown spectroscopy & Spectroscopy. The author has an hindex of 15, co-authored 49 publications receiving 663 citations.

Elemental analysis of liquid samples by laser induced breakdown spectroscopy (LIBS): Challenges and potential experimental strategies

Abstract: Despite the growing interest of research in the trace element detection in liquids via laser-induced breakdown spectroscopy (LIBS), the measurement of the ultra-low concentration of trace elements remains a challenge due to splashing, plasma cooling which in turn leads to shorter plasma lifetime. However, due to the promising emerging applications of this technique in environmental and biomedical sciences, researchers are exploring various strategies to improve the detection limits in liquid sample studies. This work is an overview of potential experimental strategies used for liquid LIBS studies and serves to describe the progress made in adopting different experimental configurations to implement the said studies for trace element detection in various application fields. Further, the development in the various sampling techniques to achieve a higher limit of detection with reproducible results are addressed here. The challenges and benefits related with various experimental schemes and sampling approaches as well as some innovative approaches that have been established recently to improve sensitivity and detection limits are highlighted using examples from the literature. The problems that remain in the liquid LIBS analysis are also discussed and an outlook for the future is featured at the end of the article.

Elemental analysis of liquid samples by laser induced breakdown spectroscopy (LIBS): Challenges and potential experimental strategies

Abstract: Despite the growing interest of research in the trace element detection in liquids via laser-induced breakdown spectroscopy (LIBS), the measurement of the ultra-low concentration of trace elements remains a challenge due to splashing, plasma cooling which in turn leads to shorter plasma lifetime. However, due to the promising emerging applications of this technique in environmental and biomedical sciences, researchers are exploring various strategies to improve the detection limits in liquid sample studies. This work is an overview of potential experimental strategies used for liquid LIBS studies and serves to describe the progress made in adopting different experimental configurations to implement the said studies for trace element detection in various application fields. Further, the development in the various sampling techniques to achieve a higher limit of detection with reproducible results are addressed here. The challenges and benefits related with various experimental schemes and sampling approaches as well as some innovative approaches that have been established recently to improve sensitivity and detection limits are highlighted using examples from the literature. The problems that remain in the liquid LIBS analysis are also discussed and an outlook for the future is featured at the end of the article.

Evaluation of high-performance liquid chromatography laser-induced fluorescence for serum protein profiling for early diagnosis of oral cancer

Abstract: The present work deals with the evaluation of a high-performance liquid chromatography laser-induced fluorescence (HPLC-LIF) technique developed in our laboratory for early detection of oral cancer from protein profiles of body fluids. The results show that protein profiles of serum samples from a given class of samples, say, normal, premalignant, or malignant, are statistically very close to each other, while profiles of members of any class are significantly different from other classes. The performance of the technique is evaluated by the use of sensitivity and specificity pairs, receiver operating characteristic (ROC) analysis, and Youden's Index. The technique uses protein profile differences in serum samples, registered by the HPLC-LIF technique. The study is carried out using serum samples from volunteers diagnosed as normal or premalignant clinically, and as malignant by histopathology. The specificities and sensitivities of the HPLC-LIF method at an ideal threshold (M-distance = 2) for normal, malignant, and premalignant classes are 100, 69.5, and 61.5%, and 86.5, 87.5, and 87.5% respectively.

Spectroscopy: A Promising Tool for Plastic Waste Management

Abstract: 1. The properties of plastics make them highly useful for various purposes in modern life. But the impact of waste produced from the same is raising serious environmental concerns because most of the plastic in use are non-biodegradable. Though there are attempts to develop plastics that are eco-friendly, the production of the same is in the initial stages only. There is thus an urgent need for efficient methods for retrieval and reprocessing of different plastic types from the domestic and industrial waste to be recycled for further use. This review focuses on four major spectroscopic methods, infrared (IR) spectroscopy, Laser induced breakdown spectroscopy (LIBS), Laser Induced Fluorescence spectroscopy (LIF), and Raman spectroscopy, highly suitable for the plastic identification and sorting because of their speed, specificity and need of only minimal human involvement for routine use. The present status of the application of these spectroscopic methods and their scope in developing an industry-oriented plastic sorting system for recycling of plastic waste is discussed.

Laser-induced breakdown spectroscopy-Raman: An effective complementary approach to analyze renal-calculi.

Abstract: Presence of renal-calculi (kidney stones) in human urethra is being increasingly diagnosed over the last decade and is considered as one of the most painful urological disorders. Accurate analysis of such stones plays a vital role in the evaluation of urolithiasis patients and in turn helps the clinicians toward exact etiologies. Two highly complementary laser-based analytical techniques; laser-induced breakdown spectroscopy (LIBS) and micro-Raman spectroscopy have been used to identify the chemical composition of different types of renal-calculi. LIBS explores elemental characteristics while Raman spectroscopy provides molecular details of the sample. This complete information on the sample composition might help clinicians to identify the key aspects of the formation of kidney stones, hence assist in therapeutic management and to prevent recurrence. The complementarity of both techniques has been emphasized and discussed. LIBS spectra of different types of stones suggest the probable composition of it by virtue of the major, minor and trace elements detected from the sample. However, it failed to differentiate the crystalline form of different hydrates of calcium oxalate stone. This lacuna was overcome by the use of Raman spectroscopy and these results are compared with conventional chemical analysis.

Laser-Induced Breakdown Spectroscopy (LIBS), Part I: Review of Basic Diagnostics and Plasma–Particle Interactions: Still-Challenging Issues Within the Analytical Plasma Community

Abstract: Laser-induced breakdown spectroscopy (LIBS) has become a very popular analytical method in the last decade in view of some of its unique features such as applicability to any type of sample, practically no sample preparation, remote sensing capability, and speed of analysis The technique has a remarkably wide applicability in many fields, and the number of applications is still growing From an analytical point of view, the quantitative aspects of LIBS may be considered its Achilles' heel, first due to the complex nature of the laser–sample interaction processes, which depend upon both the laser characteristics and the sample material properties, and second due to the plasma–particle interaction processes, which are space and time dependent Together, these may cause undesirable matrix effects Ways of alleviating these problems rely upon the description of the plasma excitation-ionization processes through the use of classical equilibrium relations and therefore on the assumption that the laser-induced

Chapter 12 – Laser-Induced Breakdown Spectroscopy: Advanced Analytical Technique

Abstract: Laser induced breakdown spectroscopy (LIBS) is basically an emission spectroscopy technique where atoms and ions are primarily formed in their excited states as a result of interaction between a tightly focused laser beam and the material sample. The interaction between matter and high-density photons generates a plasma plume, which evolves with time and may eventually acquire thermodynamic equilibrium. One of the important features of this technique is that it does not require any sample preparation, unlike conventional spectroscopic analytical techniques. Samples in the form of solids, liquids, gels, gases, plasmas and biological materials (like teeth, leaf or blood) can be studied with almost equal ease.LIBS has rapidly developed into a major analytical technology with the capability of detecting all chemical elements in a sample, of real- time response, and of close-contact or stand-off analysis of targets. The present book has been written by active specialists in this field, it includes the basic principles, the latest developments in instrumentation and the applications of LIBS. It will be useful to analytical chemists and spectroscopists as an important source of information and also to graduate students and researchers engaged in the fields of combustion, environmental science, and planetary and space exploration. It features: recent research work, possible future applications and LIBS Principles.