Chemometrics with Perl & Pharmaceutical Applications

Abstract

An NIR spectrum of a chemical-sample is a multivariate data array of N-reflected intensities of light at discrete wavelengths (i.e. 1-by-N) across the wavelength range (approximately: 900 – 1,700 nm). With many variables (wavelengths) in a spectrum (between one and several hundreds of wavelengths), interpretation of one or more NIR spectra requires multivariate analysis (termed ”chemometrics”). This work illustrates the use of Perl twofold. The first application of Perl is for qualification of analyte (pharmaceutical active ingredient) from a chemical-sample’s NIR spectrum. A multivariate analysis model for a material is produced by applying principal components analysis to a set of representative spectra of the given material. One or more mathematical data pretreatments may be applied to the NIR spectra (to minimise spectral variability unrelated to chemical composition, such as spectral baseline curvature and baseline offset), in order to produce identification models with good classification accuracy. The second application of Perl is for control of the NIR spectrometer. A Perl/Tk developed GUI is used to control the handheld NIR spectrometer, enabling acquisition of background spectra of the reference reflectance standard, and then of spectra of chemical samples. The GUI facilitates interpretation of the acquired spectrum on-the-fly, for a qualitative (i.e. identification) chemometric model. It reports to the end-user a pass/fail result for the identification test. This therefore obviates the need for the end-user to perform chemometrics.