Combination of FTIR Spectroscopy and Chemometric Method on Quantitative Approach - A Review

Review Article

Austin J Anal Pharm Chem. 2021; 8(1): 1128.

Combination of FTIR Spectroscopy and Chemometric Method on Quantitative Approach - A Review

Verma K¹, Akhtar MJ² and Anchliya A¹*

¹Department of Pharmaceutical Analysis, Indo-Soviet Friendship College of Pharmacy, India

²Department of Pharmaceutical Chemistry, Indo-Soviet Friendship College of Pharmacy, India

*Corresponding author: Anchliya A, Department of Pharmaceutical Analysis, Indo-Soviet Friendship College of Pharmacy, Ferozepur GT. Road, Moga-142001, Punjab, India

Received: August 07, 2020; Accepted: February 24, 2021; Published: March 03, 2021

Abstract

Fourier transform infrared spectroscopy is an effectual and noncritical approach for quantitative study of different types analytes present in pharmaceutical and foodstuffs. The present review describes the basic principles and the instrumentation of FTIR spectroscopy along with its sample preparation techniques, sample handling techniques and advancements. FTIR spectroscopy in combination with chemometrics techniques has been followed over long times. The main objective of this review is to assemble the data linked to application of FTIR spectroscopic and chemometrics techniques for the quantitative study of varieties of analytes like API, adulterants, caffeine, cocaine, lipids, fats & oils, sugar and others. The FTIR spectroscopy with chemometrics techniques proved to be a beneficial methodology for quantitative study to routine analysis of these analytes.

Keywords: Quantification; FTIR spectroscopy; Applications; Chemometrics

Introduction

Infrared spectroscopy has been proposed as a potent device and also consider as a green technique for analysis [1,2] because it only reagent requires is potassium bromide, promoting benefit as cost-efficient, low production of lethal waste product, less time require for analysis, no utilization of organic solvents and also provide opportunity for the analysis of material which is insoluble in commonly utilized solvents [3]. Fourier Transform Infrared Spectroscopy (FTIR) is an advanced approach for the analysis and detection of chemical compounds (i.e. organic and inorganic) according to their functional group [5]. It presents a significant knowledge of molecular structure [5], chemical composition, physical condition [6], energy state and chemical bonds of an analyte, when it absorbs infrared radiation, with the help of the IR spectrum [7].

A spectrum of IR can be split into 3 major regions: the first one is far-infrared (below 400 cm-1), second is Mid-Infrared (MIR) in range of 4000 to 400 cm-1, and the last is Near-Infrared (NIR) in the range of 13,000 to 4000 cm-1. MIR region is mainly utilized for numerous applications by employing IR spectroscopy, however, NIR and farinfrared regions were too offer significant data concerning materials [8]. In MIR spectroscopy, absorption of photons takes place and molecular vibrations get excited in the spectral regime of 2-20 μm which results in achieving an unambiguous absorption pattern that may aid as molecular fingerprints for the detection and quantification of analytes [9]. Chemical and biochemical reactions can be identified by this technique from IR spectrum on the basis of appearance or disappearance of specific band of functional group or by observing the shift in band if structure involve change in structure of end product [10]. FTIR spectrometer is high demand in laboratories for its rapid functioning, better signal to noise ratio [11] non-destructive and easy tools for analysis, with least sample preparation is required [12,13]. In quality control laboratories, this technique can be utilized for qualitative along with quantitative determination [14]. As the intensities of the absorption band in the spectrum are directly proportional to concentration i.e. it obeys Beer’s law and when coupled with chemometric techniques, FTIR spectroscopy serves as a means for quantitative study [12]. As per this law, the area under the absorption band or intensity of signal provides information regarding the concentration of an analyte [15] and calibration curve against band intensity and concentration can be constructed from standard analyte and this help us to know the concentration of an analyte under examination present in the sample [16].

Photon transfer into molecule occurs when it absorbs IR radiation and get excites jump to higher energy state which results in vibration of bond in molecules, they are:- 1) Stretching Vibration: symmetric & asymmetric and 2) Bending Vibration: scissoring, twisting, rocking & wagging, arising at different wavenumber/frequencies of light spectrum in infrared region [17]. The amount of light absorbed by sample in different frequencies relates to vibrational frequencies of bonds present in the test sample. Alteration in dipole moment between functional is a necessary criteria for the molecules to be IR active [18]. It add a plus point of real-time process and maintenance requirements is quite low, a contrast to gas chromatography, and also cost-efficient and provide detailed or specific information regarding structure as compared with mass spectroscopy [19]. The wavenumber range between 4000-1500 cm-1 and 1500-500 cm-1 are signified as functional group region and fingerprint region, respectively [20]. Absorption band in the functional group region typically arises from molecular vibrations of fundamental transitions and produces a highly characteristic pattern of absorption band. It operates at a very low energy light wave so damage in a sample due to ionization is not a concern [21]. Based on literature survey, we reviewed the research on application of FTIR spectroscopic and chemometrics techniques for the quantitative study of varieties of analytes like API, adulterants, caffeine, cocaine, lipids, fats & oils, sugar and others.

Instrumentation

FTIR instrumentation is quite simple except when the source employed is the synchrotron, and produce highly accurate and precise data having high spatial resolutions [22]. For the IR region, the light source is like tungsten filament which is heated and radiates polychromatic light. Then the light beam is focused on the Michelson interferometer, containing a beam splitter to slight light source into two i.e. 50% transmits and 50% reflects. Further these both split beams. The split beams stick two different mirrors, the first one is motionless and the other continuously oscillate backward and forward direction with definite frequency and amplitude. After that, these two beams merge again at a beam splitter and interfere due to the difference in optical path length then move towards sample [23] (Figure 1). Wavelength of emitted light is measured by interferometer through interference patterns, aid to enhance accuracy. Total scans can increased as per the quality required for analysing the sample [24]. The x and y-axis of the spectrum signifies the wavenumber and absorbance or transmittance respectively [25].