Development of chemometrics in China*

Liang Yizeng , Yu Ruqin
(College of chemistry and Chemical Engineering, Hunan University, Institute of Chemometrics and Chemical Sensoring Technology, Hunan University, Changsha, 410082, China)

Received Aug. 15, 1999
*The Chinese version of this paper was published in Chemistry (Huaxue Tongbao), 1999, 62 (10): 14.

Abstract Recent development of chemometrics in China is reviewed in this paper, which includes multivariate calibration and resolution, robust methods, chemical pattern recognition, quantitative structure-activity relationship (QSAR), molecular modeling and optimization, chemical expert systems and databases. The new techniques recently developed in chemometrics, such as analysis methods for high-dimensional data, artificial neural networks, and wavelet transformation technique, are specially addressed.
Keyword chemometrics

Chemometrics has been developed more than 20 years in China. It is a new cross chemical branch which uses the theory and methods developed in statistics, mathematics and computer science and other related disciplines to optimize the procedure of chemical measurement, and to extract useful information from chemical measurements as much as possible^[1]. Chemometrics starts from chemical measurement which differs from the computational chemistry which is purely based on quantum chemistry. Thus, chemometrics is essentially the theory and methodology of chemical measurement.^[2]
    Because of the influence of "turmoil of ten years", the development of chemometrics in China was little bit late comparing with Europe and American. However, under sparkpluging of the grand old men in chemistry field and the strong support from the national natural science foundation committee (NSFC), the researches on chemometrics have been developed quickly since early of 80's. Now chemometrics in China has become a new independent chemical branch of international reputation. Several monographs and text books on chemometrics have been published in Chinese^[3], and also a lot of research groups on chemometrics in the institutes in Chinese science academy and the universities who made lots of achievements of international level have been established. We once reviewed the development of chemometrics in China 8 years' ago at the second Scandinavia conference on chemometrics^[4], here we only review the recent development of chemometrics in China after that time.
    Chemometrics provides theory and methodology for the chemical measurements, and analyzes the various spectral data from chemical measurements in order to solve the difficult problems in chemistry and chemical engineering. Its researches cover the whole process of chemical measuring, including sampling theory and methods, experimental design and optimization for chemistry and chemical engineering processes, chemical signal processing, multivariate calibration and resolution, chemical pattern recognition, simulation of chemistry and chemical engineering processes, quantitative structure and activity relationship (QSAR), chemical database and artificial intelligence and chemical expert systems. It is a new chemical branch of extensive contents, which provides lots of new idea, new way and new methods for solving the problems in many chemical branches, such as analytical chemistry, environmental chemistry, pharmaceutical chemistry, organic chemistry and chemical engineering and etc..
    Chemometrics has been becoming a new branch in chemistry and analytical chemistry, it was the two factors that promoted this development. Firstly, the appearance of lots of chemical instruments made the fact possible that chemists and analytical chemists could acquire chemical measurement data much easily than ever before. It was surprising for chemists to find at the first time that the most difficult problem was not the acquirement of chemical data, instead, how to extract the useful information from the huge amount of data was a really difficult problem faced by chemists. However, chemists were much more luckier, since the "period of knowledge exploding" for chemists to face was just the period of computer. This became the second condition of the quick development of chemometrics. In order to analyze the complex chemical measurement data, in which the molecular information of the matter was embedded, chemists had to use computer and the new methods developed in other disciplines, such as applied mathematics, statistics and computer science, to extract the useful chemical information. For the real complex samples, the classical analytical chemistry is first to separate the pure components by tedious and time-consuming chemical and/or physical methods, and then to determine qualitatively and quantitatively them step by step by single variable calibration methods. However, what the modern analytical chemists face is the huge high-dimensional data obtained from hyphenated instruments containing both information of chromatographic separation and spectral analysis. With the help of the techniques of multivariate calibration and resolution developed in chemometrics^[5], one can directly address simultaneously qualitative and quantitative analytical problems for the complex samples from environmental chemistry, pharmaceutical chemistry, petroleum chemistry and etc.. The great achievements have been reached for the analysis of complex samples in environmental chemistry and traditional Chinese medicines^[6]. To continue to do researches on the analysis of the high-dimensional data, especially for the chemometric methods for analyzing three-way data is still a hot-point problem in chemometrics, the research on this in China has now reached international level^[7]. The researches on multivariate calibration and resolution have been being the main part for analytical chemometrics in China. In respect of this aspect, the research groups in Science and Technology university of China, Tsing-Hua university, Science Academy of Petroleum Chemical Engineering, Pharmaceutical university of China, Tong-Ji university, Tian-Jin university, Xia-Men university, Lan-Zhou university, Nan-Can university, Northwest university and Hunan university have done a lot of works on this^[8]. Thus, building in the chemometric methods into the analytical instruments in order to construct the new generation of the intelligent instruments is an attractive research direction in analytical chemometrics. On the other hand, the recent quick developments of computer and information sciences gave some new opportunities to chemometrics. The new methods for signal processing, especially the methods of wavelet analysis, brought along the new ideas of data-compressing, de-noising and removing-background from instruments for chemometrics. From the recent review, one can easily see that the research on this aspect in China is quite developed. The research groups in Science and Technology university of China, Zhong-Shan university and Hong Kong Polytechnic university have done lots of high-level research works^[9]. In addition, the introduction of some new algorithms of artificial neural networks (ANN)^[10], simulated annealing (SA), genetic algorithm (GA)^[11], image analysis (IA) methods and robust methods^[12] also produced lots of very good results for chemometrics. Sampling theory is a very important aspect in chemometrics. The recent research work on sampling theory has been done by the research group in Nan-Kai university^[13].
    Chemical pattern recognition can provide very useful information for decision making and optimization of chemical processing. It has brought along lots of new ideas for solving the difficult problems in petroleum chemical engineering and material chemistry in China. The introduction of ANN techniques provided a new opportunity for the researches on chemical pattern recognition. On both of the theoretic and application researches of chemical pattern recognition, China has gained great achievements. The research group in Shanghai institute of metallurge of Chinese academy of Science have solved more than 50 difficult problems in optimization of the petroleum chemical engineering and designs of new chemical materials. Chemical pattern recognition applied to analytical chemistry, physical chemistry, inorganic and organic chemistry, pharmaceutical chemistry, food chemistry and environmental chemistry has also achieved great successes. In this aspect, the chemometric research groups in Zhe-Jiang university, Science and Technology university of China, Shen-Yang pharmaceutical university, Pharmaceutical university of China, Tong-Ji university, Chang-Chun applied chemistry institute of Chinese academy of science and Hunan university have done lots of works^[14]_.
    The research on the chemical quantitative structure-activity relationship (QSAR) is a basic problem in chemistry. Because of the development of pharmaceutics, the combination of the molecular modeling and QSAR provided quite a new way for finding efficiently the leading compounds of medicine and biology activity. Chemometricians in China together with the quantum chemists have also gained a great achievements in the recent years^[15]. For instance, the introduction of global optimization algorithms, such as simulated annealing and genetic algorithms, into molecular modeling was the original contribution from chemometrics. QSAR uses the regression methods and pattern recognition methods to establish the quantitative relationship between the chemical measurement data (properties of the chemical compounds) and molecular topologic index (chemical structure) developed by chemists in order to predict the properties of other materials without knowing their chemical properties. Using the ANN techniques, recently developed in chemometrics, to conduct the QSAR researches is an attractive direction in chemometrics. Nan-Kai university, Beijing university, Shanghai pharmaceutical institute of Chinese academy of Science, Shanghai institute of metallurge of Chinese academy of Science, Chang-Chun applied chemistry institute of Chinese academy of science and Hunan university have done lots of works on this subject. They combined techniques of molecular modeling and QSAR, and also used the obtained model through QSAR research to further direct the chemical experiments. Some exciting results has been obtained^[16]. In QSAR research, how to use the graphic and numeric methods to express the molecular structures is also an important problem in chemometrics. Some meaningful works on this subject have also been done in China^[17].
    Spectral chemistry is very important in both analytical chemistry and organic chemistry. How to use the available spectral databases, such as mass spectral database, infrared spectral database, MNR spectral database and etc., to directly qualifying the complex samples has been a dream of analytical chemists. Moreover, how to use the spectral databases to clarify the chemical structure of the new synthetic compound is also concerned by the organic chemists. The computer techniques, especially the techniques for intelligent database management and expert system, have provided a complete new way to solve the problems. The chemometricians in China have also contributed a lot on this subject. The chemometric research groups in the Shanghai organic chemistry institute of Chinese academy of Science, Da-Lian institute of chemical physics of Chinese academy of Science, Chang-Chun applied chemistry institute of Chinese academy of science, Nan-Kai university, Nan-Jing university, Northeast Normal university, Xia-men university and Hunan university have established several spectral databases and chemical expert systems^[18], such as ¹³C-NMR spectral database and expert system (ESESOC) , HPLC expert system, IR and Mass spectral database and expert system, ICP emitting spectral expert system and etc.. They used the databases and chemical expert system to do the research on data mining, to mimic various spectra, to elucidate the structure of unknown chemical compounds, and to optimize the performance condition of the instruments and etc.. The work on database in internet have also been started in China^[19].
    In 1997, under support of national natural science foundation committee (NSFC), Hunan university and Bergen university in Norway have successfully held the first international conference on chemometrics in China. More than 120 representatives come from 14 countries in Europe and American attended the conference. The subjects cover almost every research branch in chemometrics, especially, a session on industrial application was also held. The special issue for the conference has been published on the journal of "Chemometrics and Intelligent Laboratory Systems"^[20], in which 44 papers were included, among them 28 were from Chinese chemometricians.
    From now on, chemometrics has its 30 years' history. From the relationship between analytical chemistry and chemometrics, one can see that chemometrics may provide the fundamental basis of analytical chemistry, since analytical chemistry is essentially a chemical measurement science. Furthermore, the development of chemometrics will also provide new theory and methods for analysts to construct the new generation of the intelligent analytical instruments. It may be the point of break-through in analytical chemistry in next century. In addition, with the development of internet techniques and micro-computer, the techniques related to chemical databases will be also developed quickly. Using the technique of data mining, combining the numeric methods (the main part of chemometrics) and logic induction methods will result in lots of new opportunities for chemometricians to solve the difficult problems in chemistry. The future of chemometrics in analytical chemistry is promising. However, the relationships of chemometrics with other chemical branches, such as environmental chemistry, pharmaceutical chemistry, agricultural chemistry, food chemistry and chemical engineering and etc., will also become more closed, the application of chemometrics in thsee chemical branches will be more extensive. We believe that chemometrics will develop even quicker than last century.

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