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1 DEVELOPMENT OF MEASUREMENT AND CHEMOMETRIC METHODS IN THE FOURIER TRANSFORM INFRARED AND RAMAN SPECTROSCOPY PhD Theses Written by: Brunó Hren Chemical engineer Supervisor: Prof. Dr. János Mink Made in the Environmental Sciences Doctoral School University of Pannonia Veszprém 2008

2 INTRODUCTIONS, AIMS In the past ten years, the increasing of the sensitivity, the brightness, the throughput and stability of the Fourier transform infrared (FTIR) spectrometers has been opened the possibility to investigate gaseous samples with low concentration. The main advantage of the infrared method is that, in the spectrum appear the spectral lines characteristic for all investigated molecules. In this way, with this method in-situ multicomponent (10-30) analysis becomes possible without destruction or difficult sample preparation. In some cases of industrial samples, even alone the sophisticated high sensitive FTIR spectrometers can not supply suitable spectra for quantitative analysis. Only the chemometric treatments of the digital spectra can assist able to solve this problem. According to the above considerations, the aim of my work can be summarised as follows: Installation of a brand new Fourier transform infrared spectrometer in our special laboratory with optional high sensitive two detectors, a long path gas cell, and a special sample compartment to meet a condition of particular measurements. Laboratory development of high-level FTIR spectroscopic measurement methods adequate to in-situ quantitative and qualitative analyse for industrial gas samples. Development of a new FTIR gas spectroscopic technique to replace the usually more expensive industrial measurement methods with the elimination their disadvantages. Development of brand new gas spectroscopic chemometric methods, which able to expand the physical limits of the performance of the spectrometer system. Investigation of the universal adaptability of the developed chemometric method to enhancement of condensed phase spectrometry. EXPERIMENTAL A Digilab (Bio-Rad) FTS-185 series Fourier transform spectrometer equipped with KBr beam splitter and high sensitivity liquid nitrogen cooled InSb or HgCdTe detectors and PAPA type of photolysis assisted long-path gas cell was used to collect the spectra in the mid infrared region, at resolution of 0.5 cm -1. The quantitative and qualitative analysis was assist with the use of reference library spectra. Mathworks MatLab program was adopted for development of the new chemometric procedure. A Digilab (Bio-Rad) Fourier transform Raman spectrometer equipped with Nd:Yag laser and liquid nitrogen cooled Ge semiconductor detector was used to obtain Raman spectra.

3 THESES I. THE FIRST AND UNIQUE FTIR GAS SPECTROSCOPIC SYSTEM HAS BEEN INSTALLED IN HUNGARY. (a) In the gas spectroscopic laboratory a new FTS-185 (Bio-Rad) infrared spectrometer has been installed with two high sensitive detectors and coupled to a PAPA type of photolysis assisted long path (32.1 meters) gas cell. With the new special equipment, determination of the gas composition of the industrial gas samples has been performed. II. DETECTION OF INDUSTRIAL AIR POLLUTANT GASES BY FOURIER TRANSFORM INFRARED SPECTROMETRY USING LONG PATH GAS CELL. (a) A new, useful, industrial, and automated procedure has been developed for multicomponent detection and quantitative analysis of the long chain aliphatic hydrocarbons. (b) Nowadays the gas compositions are detected with use of unique, molecule specific methods, and instruments. The suggested method, perfectly suitable to perform multicomponent analysis, instead of using above mentioned single component methodologies. (c) It was established, that the method, based on an auto-subtraction algorithm using individual spectral features of the gases, is more reliable to estimate the concentration of the long chain aliphatic hydrocarbons. Further advantage of this procedure is the visual observation possibility and monitoring of the process during spectral subtraction.

4 III. GAS COMPOSITION FTIR ANALYSIS OF LOW-VOLUME LIGHT BULBS. (a) It has been demonstrated, that the high sensitivity FTIR spectroscopy is a very useful method for non-destructive in-situ gas composition analysis of low-volume light bulbs. (b) It has been showed, that the interference fringes originated from the parallel quartz walls of the bulbs can be eliminated by mathematical treatment of the infrared spectra. In the frequency domain, the characteristic of the interference noise is sinusoidal, so it could be eliminate in the time domain. The Principal Component Analysis based on the NIPALS algorithm yielded better efficiency for the methods applied to determination of the concentration values. (c) The CH 3 Br, HBr and the CO concentrations have been determined using reference library spectra. The CO and HBr showed a maximum concentration value during the burning period. Later, the CO has been practically burned out, while the HBr concentration has been stabilized at a ppm permanent level. The presence of CH 3 Br is confirmed by the spectra of the original (unused) bulbs, but its concentration becomes undetectable after 5 sec of burning time. (d) It has been confirmed that, due to the reason of interference noise, it was not possible to determine the concentration changes close to the detection limits without the use of the developed chemometric procedure. (e) Furthermore it has been obtained that, the suggested new method is very useful for reduction of the residual spectral lines originated from the atmospheric carbon monoxide and water vapour spectral subtraction from the original spectra of air samples. The efficiency of the procedure has been showed by several spectral features. (f) With the use of the developed measurement technique and analytical procedure, the continuous, non-destructive investigation of the bulbs became possible, even along the production line.

5 IV. INVESTIGATION OF THE APPLICABILITY OF THE DEVELOPED CHEMOMETRIC METHODS TO THE FT RAMAN SPECTROSCOPY OF CONDENSED SAMPLES. (a) The developed algorithm for the infrared gas spectra on the based of the Principal Component Analysis has been modified with the use of the Savitzky-Golay smoothing filter. In this way, it was shown that the method can be used for qualitative and quantitative analysis of another type of spectra exhibiting significant noise level. (b) The modified smoothing algorithm has been used for evaluation of Raman spectra. It was obtained that, the first and second derivatives of the noisy Raman spectra can not be interpreted without a pre-treatment procedure of the spectra. This problem has been solved with the use of the new chemometric procedure, which offers the possibilities of further evaluations, e.g. derivations, band deconvolutions and structural interpretations.

6 PUBLICATIONS RELATED TO THE DISSERTATION [S1] B. Hren, K. Katona, J. Mink, J. Kohán and Gy. Isaák: Log-path FTIR spectroscopic studies of air pollutants in the Danube refinery plant; Analyst, 2000, 125, [S2] B. Hren, J. Mink and L. Balázs: Fourier Transform Infrared Analysis of Gas Composition in Low-Volume Light Bulbs; Anal. Chem., 2002, 74, [S3] E. Horváth, L. Kocsis, R. L. Frost, B. Hren, L. P. Szabó: Investigation of Enantiomer Bonding on a Chiral Stationary Phase by FT-Raman Spectroscopy; Anal. Chem. 1998, 70,

7 PRESENTATIONS RELATED TO THE DISSERTATION [1] B. Hren, L. Nagy, J. Mink: FT-IR Spectroscopic Feasibility Study for Gas Composition Analysis; 23 th European Congress on Molecular Spectroscopy, August 25-30, 1996, Balatonfüred, Hungary. (poster) [2] B. Hren, J. Mink: Air Pollution Trace Gas Analyses Using a Long-Path Infrared Gas Cell; EUROANALYSIS IX, September 1-7, 1996, Bologna, Italy. (poster) [3] B. Hren and J. Mink: The FT-IR Spectroscopy for Composition Analysis of Low Volume Gas System; The 11 th International Conference on Fourier Transform Spectroscopy, August 10-15, 1997, Athens, Georgia, U.S.A. (poster) [4] B. Hren, K. Katona, J. Mink: Investigation of Photochemical Reactions of Air Pollutant Gases Using FT-IR Spectroscopy; 2 nd Mediterranean Basin Conference on Analytical Chemistry, November 23-28, 1997, Rabat, Morocco. (poster) [5] K. Katona, B. Hren, J. Mink, J. Kohán, Gy. Isaák: Long-path FT-IR Spectroscopic Studies of Air Pollutants in Danube Pattern; 3 rd International Symposium on Advanced Infrared and Raman Spectroscopy, July 5-9, 1998, Vienna, Austria. (poster) [6] A. Herczeg, B. Hren, J.Mink: Detection of Ambient Air Pollutants by Long Path FT- IR Gas Spectroscopy; EUROANALYSIS X, September 6-11, 1998, Basel, Switzerland. (poster) [7] B. Hren, K. Katona, J. Mink: Investigation of Photochemical Reactions of Air Pollutant Gases Using FT-IR Spectroscopy; EUROANALYSIS X, September 6-11, 1998, Basel, Switzerland. (poster) [8] Hren Brunó: Kistérfogatú gázrendszerek összetétel analízise FT-IR spektroszkópiával; Analitikai Kémia Tanszék, Veszprémi Egyetem, január 29. [9] Hren Brunó, Mink János: Gázok nagyérzékenységű FT-IR spektroszkópiája; MTA Anyag- és Molekulapektroszkópiai Bizottsági Ülés, ELTE, Budapest, február. [10] Hren B., Mink J., Balázs L.: FTIR gázösszetétel folyamatos analízise kistérfogatú halogén izzókban; 46. Magyar Spektrokémiai Vándorgyűlés, Szeged, június 30 július 2.

Fourier Transform Infrared. Spectrometry

Fourier Transform Infrared. Spectrometry Second Editio n PETER R. GRIFFITH S JAMES A. de HASETH PREFACE x v CHAPTER 1 INTRODUCTION TO VIBRATIONAL SPECTROSCOPY 1 1.1. Introduction 1 1.2. Molecular Vibrations