Shotr-wave Near Infrared Detection Technology Under Complex Conditions

Near infrared spectroscopy (NIR) is a fast and non-destructive analytical method forqualitative and quantitative analysis. It has been widely used in petroleum,agriculture and pharmaceutical industry et al. The NIR technology is quitecomplicated, which involves optical sensing technology, computer technology andchemometric methods. Recently the short-wave NIR (SW-NIR,780-1100nm)technology has drawn researchers' attention, due to the significantly low cost. TheSW-NIR, which originates from the2or3overtone of molecular vibration, cantransfer more deeply into the sample with less heat effect. Moreover, theinterference from intense water absorbance can be diminished. Instrumentationworking on this region is a sort of important process analytical technology, which isof low cost, compact and fast scanning. However, improvement is still need in termsof instrumentation and application technology in order to meet the new demands.Firstly, to determine the low content analyte, the signal-to–noise ratio of SW-NIRinstruments need to be further improved. Secondly, the electrics in the instrumentsneed to be designed more flexible and smarter. A more flexible electronic circuitwhich can drive more than one kind of light sensor should be helpful to reduce thecost. And a smarter instrument which can regulate the parameters automatically isuseful for the long-term stability and consistent of the SW-NIR spectra. Since theSW-NIR spectra are originated from the over tone of molecular vibration, the spectraare quite overlapped and complicated. Thus, the extreme application conditionsoften lead to the shift, rotation of the spectra which lead to more complicatedanalysis of the spectra. The extreme conditions include low content analyte,influence of external variable and complicated analytical matrix et al. Therefore, theapplication field of SW-NIR is limited and need to be expended by simultaneouslyusing other technologies.In this dissertation research was done in terms of the SW-NIR instrumentaltechnology, multivariable calibration methods and new applications. The objective was to use this low-cost technology in complicated conditions and new applicationfields. And this was achieved through development in the instrumentation andcalibration method as well as the applying some new extraction technology. A newmultichannel SW-NIR spectrometer was designed by using the charge-coupled device(CCD) as the detector. A signal-to-noise ratio of500:1in the whole wavelength regionwas achieved by the compound light source design and using the self-adaptive lightintense regulation strategy. The light source was designed using a halogen lampenhanced by two single wavelength light emitting diodes centered at920nm and1020nm respectively. The electronic circuit designed can drive two different CCDs,which need only change the program in the microcontroller. This electronic circuitwas quite flexible and can be used for different demands with a very low cost. Themultivariate detection limit (MDL) was calculated and the relation between MDL andpartial least squares (PLS) calibration was researched to find a calibration strategy fordetermination of low analyte using the SW-NIR technology. This was done by analysisof the glucose injection using the designed SW-NIR spectrometer. PLS models werebuilt in different concentration ranges. It was found that a narrow concentrationrange which included the concentration of target analyte should be selected in orderto obtain a lower MDL. This conclusion was further proved by determining thesulfonamides additives in pig feed using FT-NIR spectroscopy. Furthermore, it wasfound that the optimal calibration sample number can be determined by comparingthe MDL. The influence of external variable can be diminished by appropriatecalibration methods. And this was approved by determining the alcohol content inaqueous solution at different temperature using the SW-NIR spectra. A significantsystematic error was found when using the direct transfer method which indicated atemperature correction was necessary. For this purpose, global modeling, orthogonalsignal correction (OSC) and generalized least squares weighting (GLSW) were utilizedand compared. It was found that all the three methods can reduce the temperatureinfluence. But the OSC and GLSW methods used less calibration samples that theglobal modeling and could be used as spectra pretreatment. The GLSW method provided the best predictions at all the four temperatures requiring less latentvariables. Thus, the GLSW method was superior to the OSC method. The possibilityof using the SW-NIR method to analyze the target analyte in complicated matrix wasapproved by determining sulfonamides in the pharmaceutical wastewater incombination with magnetic molecular imprinted polymers (MMIP). The MMIP wassynthesized and had good selective adsorption ability towards sulfonamides andstructurally related molecular. By using this MMIP with a designed auto-samplingdevice, sulfonamides in complicated matrix, wastewater, were separated andtransferred to a simple matrix-acetonitrile. Then the extractions were analyzed byusing the FT-NIR and SW-NIR spectroscopy. The SW-NIR did not provide goodpredictions due to the weak absorbance. However, good results were obtained byusing the FT-NIR spectroscopy, which approved the possibility of using this newapproach to fast determine the sulfonamides in pharmaceutical wastewater. Theweakness of NIR spectroscopy, such as relatively high detection limit and poorresolution, can be avoided by simultaneously using the MMIP technology. Theconclusions made in the research of the current dissertation are useful and helpfulfor using the SW-NIR technology in complicated conditions. And by using MMIPtechnology, the application field of SW-NIR was further expended.