Infrared Spectral Data Research Articles

Quality Assurance of Torrefied Biomass Using RGB, Visual and near Infrared (Hyper) Spectral Image Data

Visible and near infrared imaging techniques for analysing characteristics of torrefied biomass were evaluated for possible use in future online process control. The goal of such a control system is to identify products with the desired properties and reject products outside the specification. Two pushbroom hyperspectral cameras with different wavelength regions and a commercial digital colour camera were evaluated. The hyperspectral cameras, short wave infrared (SWIR) and visible–near infrared (VNIR), covered the ranges of 1000–2500 nm and 400–1000 nm, respectively. The biomass was produced according to an experimental design in a torrefaction pilot plant at different temperatures, residence times, and nitrogen and steam flow rates to obtain a wide range of different characteristics and qualities of torrefied material. Chemical characteristics, heating values and milling energy of the different torrefied materials were analysed or calculated using standardized procedures and were used for calibration. For the hyperspectral images, a principal-component analysis was performed on the absorbance spectra. The score plots and score images were used interactively to separate background, outlier pixels and shading effects from sample signal. Averaged spectra of individual torrefied woodchips were used. Partial least-squares regression was used to relate average spectra to heating values and chemical characteristics of the torrefied biomass. Owing to the small size of the data sets, cross-validation using leave-one-out validation was used for testing the models. The ratio of standard error of prediction to sample standard deviation ( RPD) values were used for comparing the imaging techniques. For RGB images, all RPD values were 4 or lower. The RPD values for the VNIR technique were all below 5, while the SWIR images produced RPD values above 5 for eight of the 13 properties. The promising results of the SWIR technique strongly suggested that the torrefied biomass undergoes changes to chemical structures, which are not necessarily manifested as changes to the colour of the material.

Sonified Infrared Spectra and Their Interpretation by Blind and Visually Impaired Students

To make the analysis of infrared (IR) spectra accessible to students who are blind and visually impaired (BVI), the visual information of the spectra was converted into nonspeech sounds using the open-source programs JDXview v0.2 and CSV to MIDI converter. In the sonified infrared spectra (SIRS), time is used as a spectral frequency indicator, and the range of the selected musical instrument frequencies is correlated with the intensity of the corresponding band absorptions. To simplify the identification of the absorption bands in the SIRS, seven audible distinguishable time markers were added: at the beginning, 3000, 2500, 2000, 1500, 1000 cm–1, and at the end. This approach allows the fast identification of typical functional groups, or a set of frequencies related to a particular structural pattern in a molecule. By conveying IR spectral data, SIRS will aid BVI students’ chemical education; SIRS can be used either for distance learning or in classroom activities.

MetOp-A/IASI Observed Continental Thermal IR Emissivity Variations

<?Pub Dtl=""?> Satellite thermal infrared (IR) spectral emissivity data have been shown to be significant for atmospheric research and monitoring the Earth's environment. Long-term and large-scale observations that are needed for global monitoring and research can only be supplied by satellite-based remote sensing. Presented here is the global surface IR emissivity data retrieved from the last five and half years of Infrared Atmospheric Sounding Interferometer (IASI) measurements observed from the MetOp-A satellite. Monthly mean surface properties (i.e., skin temperature <formula formulatype="inline" xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex Notation="TeX">$T_{\rm s}$</tex></formula> and spectral emissivity <formula formulatype="inline" xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex Notation="TeX">$\varepsilon_{\nu}$</tex></formula> ) with a spatial resolution of 0.5 <formula formulatype="inline" xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex Notation="TeX">$\times$</tex></formula> 0.5-degrees latitude-longitude are produced to monitor seasonal and inter-annual variations. Continental IR spectral emissivity derived from satellite ultraspectral IR measurements reveals its variation depending on surface weather and climate conditions. Variation behaviors of continental IR spectral emissivity, associated with the seasonal change as well as weather and climate conditions are initially captured by IASI measurements and will be continuously monitored as provided by the satellite measurements. Surface <formula formulatype="inline" xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex Notation="TeX">$\varepsilon_{\nu}$</tex></formula> retrieved with IASI measurements can be used to assist in monitoring surface weather and surface climate change. Surface <formula formulatype="inline" xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex Notation="TeX">$\varepsilon_{\nu}$</tex> </formula> together with <formula formulatype="inline" xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex Notation="TeX">$T_{\rm s}$</tex></formula> from current and future operational weather satellites can be utilized as a means of long-term and large-scale monitoring of Earth's surface weather environment and associated changes.

Light scattering from diatomaceous earth aerosol

The light scattering and extinction properties of mineral aerosol are strongly affected by dust particle shape. In this work, scattering phase function and polarization profiles of diatomaceous earth aerosol are measured at a wavelength of 550nm, and the results are compared to T-matrix theory based simulations using uniform spheroid models for the particle shape. The particle shape distribution is determined by spectral fitting of the experimental infrared (IR) extinction spectral line profile for diatomaceous earth dust. It is found that a particle shape model that peaks toward both extreme rod-like and disk-like shapes results in the best fits to the IR spectral data. This particle shape model is then used as a basis for modeling the visible light scattering properties. While the visible simulations show only modestly good agreement with the data, the fits are generally better than those obtained using more commonly invoked particle shape distributions.

The Identification of Spiromesifen, a Recently Introduced Pesticide, Using Approaches to Chemical Unknown Analysis

An unknown, viscous, opaque, white liquid with a strong, unpleasant odor was submitted with a request for identification. It was analyzed using infrared (IR) spectroscopy, gas chromatography-mass spectrometry, and X-ray fluorescence spectroscopy. It was found to contain glycerin as well as another compound. IR and mass spectral data were readily obtained for this second component, but it was not easily identified as common instrument libraries had no matching spectra. After an extensive literature search, the unknown compound was identified as spiromesifen, a recently introduced pesticide. The IR spectrum and electron impact mass spectrum of spiromesifen are presented here as these are not available in the published literature. This case report also provides useful approaches for searching for and identifying an unknown compound when it is not found in a laboratory's spectral libraries.

Heterocyclic substituted thiosemicarbazides and their Cu(II) complexes: synthesis, spectral characterization, thermal, molecular modeling, and DNA degradation studies

Four Cu(II) complexes of N 1-phenyl-N 2-(pyridin-2-yl)hydrazine-1,2-bis(carbothioamide) (H2PPS), N-phenyl-2-(2-(pyridin-2-ylcarbamothioyl)hydrazinyl)-2-thioxoacetamide (H2PBO), N-phenyl-2-(pyridin-2-ylcarbamothioyl)hydrazinecarboxamide (H2APO), and 1-(aminoN-(pyridin-2-yl)methanethio)-4-(pyridin-yl)thiosemicarbazide (H2PPY) have been prepared and characterized by elemental analyses, spectral (infrared (IR), UV-Visible, 1H NMR, and electron spin resonance (ESR)) as well as magnetic and thermal measurements. Varying the substituents on the thiosemicarbazide led to remarkable modifications of the mode of coordination. IR spectral data reveal that the ligands are SN bidentate, NON tridentate, or NSNS tetradendate chelates forming structures in which copper is square-planar or octahedral. ESR spectra of these complexes are quite similar and exhibit an axially symmetric g-tensor parameter with g| > g ⊥ > 2.0023 revealing an appreciable covalency with d( x 2 –y 2 ) as the ground-state. Bond lengths, bond angles, HOMO, LUMO, and dipole moments have been calculated to confirm the geometry of the thiosemicarbazide derivatives and their corresponding complexes. Proton-ligand dissociation and copper-ligand stability constants of all ligands were calculated pH-metrically. The effect of the compounds on calf thymus DNA was investigated.

Synthesis and optimization of polyacrylamide and gum arabic graft copolymer

Graft copolymerization of polyacrylamide onto gum arabic was carried out in aqueous medium at room temperature (30oC) using various initiator (ceric ion) and monomer (acrylamide) concentrations. The extent of graft copolymer formation was determined in terms of percentage graft yield. The results obtained showed that the percentage yield of the graft copolymer is a function of both the initiator and monomer concentrations. The grafted copolymer was characterized by infrared (IR) spectroscopy. The IR spectral data for pure Gum Arabic (GA) and that of Gum Arabic-grafted Polyacrylamide (GA-g-PAAM) indicate that grafting actually occurred. The successful grafting of polyacrylamide onto gum arabic will enhance the search for materials transformation through chemical derivatization with attendant expansion of their spectra of application.Keywords: Graft copolymerization, polyacrylamide, monomer, gum arabic, Chemical derivatization

Using Interlaboratory Proficiency Data to Guide NIR/MIR Calibrations

There is growing interest in the use of near-range and/or midrange infrared (IR) diffuse reflectance spectroscopy (NIR and MIR) as nondestructive alternatives to chemical testing of soils. This trend is supported by research on how best to correlate IR spectral data with results obtained by conventional laboratory measurements. While for soils there is growing interest in developing local and national calibrations using “legacy” data, the proven analytical performance of provider laboratories now and earlier, the moisture status of reported results, and the method of soil preparation warrant greater attention. Examples for soil carbon (C) and total soil nitrogen (N) from Australasian interlaboratory proficiency testing across multiple years from 1993 are provided to demonstrate the magnitude of past and present measurement uncertainties, including the effects of method and different concentrations. The evidence is sufficient to require those commissioned to develop NIR and MIR calibrations to subject their prototype calibrations to external peer review by participating in credible, independent interlaboratory proficiency testing programs for ≥12 months, including checks on soil moisture status and possible effects of sample preparation. To rate as credible for most uses, the prototype results should be within the interquartile range for each sample and ideally there should be no outliers and few stragglers. Across the period of assessment (1993–2008), users of Walkley and Black organic C and Kjeldahl digestion for total soil N (Kjeldahl method does not measure total N, but most of the organic N plus an undetermined proportion of nitrate and nitrate present in the sample; quantitative inclusion of both requires a modification of the Kjeldahl procedure) declined as use of furnace technologies for soil C and N increased linearly. There is a strong case to commission two or three well-performing and experienced laboratories to reanalyze samples in “legacy” soil collections prior to finalizing predictive relationships with NIR/MIR spectra for the same samples.

Microspheres based on mannosylated lysine-co-sodium alginate for macrophage-specific delivery of isoniazid

Abstract The present investigation reports coupling of ɛ- and α-amino groups of lysine (LS) with mannose (m-LS) and sodium alginate (SA), respectively, to reduce its toxicity. Prepared conjugate, m-LS-co-SA, was characterized through infra-red spectroscopy and differential scanning calorimetry. Cell viability studies were undertaken to assess the safety profile of the prepared conjugate. Microspheres, based on the conjugate, were prepared using spray drying technique and studied for targeting of isoniazid to alveolar macrophages (AMs). Pharmacokinetic studies of the optimized formulation batch were performed in Charles Foster rats. Infra-red spectral data of the synthesized conjugate were in agreement to the presumptive sequence of the conjugation process. Dispersibility, thermal stability and safety of the conjugate were conducive to its biomedical application. Microspheres, formulated from the conjugate, were of uniform size and offered satisfactory drug loading efficiency and in vitro release characteristics. X-ray diffraction studies established that drug was entrapped within the microspheres rather than being adsorbed on to the surface. Pharmacokinetic studies revealed that the conjugate could be a potential vehicle towards both active targeting of isoniazid to AMs and controlling its release rate.

Studies on Bis(Para Anisidine Acetylacetonato) Nickel (II) Complex

Schiff base was prepared from the reaction of para anisidine and acetylacetone. Bis(para anisidineacetylacetonato)nickel(II) complex was synthesized by the reaction of the prepared para anisidineacetylacetone ligand and nickel(II) chloride. The prepared Schiff base is orange yellow, has a yield of 61.90% and melting point of 86 o C. The complex prepared is red, has a yield of 71% and decomposition temperature of 270 o C. The para anisidineacetylacetone ligand is soluble in water and most organic solvents, similarly, its nickel(II) complex compound is soluble in most solvents except water and methanol, in which it slightly soluble. The molar conductance of bis(para anisidineacetylacetonato)nickel (II) complex compound determined is 4.70 ohm -1 cm 2 mol -1 , suggesting that the complex is non-electrolyte. The infra-red spectral data of para anisidine and acetylacetone base showed a medium size band in the range 1595 – 1630cm -1 , attributable to v(C=N) stretching vibrations, the same band is observable in the nickel(II) complex, indicating coordination of the ligand to the nickel(II) ion. The broad band in the range 3257 - 3420 cm -1 observed in para anisidineacetylacetone ligand is assigned to v(O-H) stretching vibrations, which is absent in anisidineacetylacetonato)nickel(II) complex, as a result of deprotonation of the para anisidineacetylacetone on coordination to the nickel(II) ion. The dissociation constant (pKa) of para-anisidine acetylacetone determined is 12.66. The stability constant of anisidineacetylacetonato)nickel (II) complex compound determined is 1.29x106 and the corresponding Gibb’s free energy of complex is -3.48 x10 4 KJ per mole. The average number of para anisidine ligand coordinated to nickel(II) ion determined using potentiometer is 2, suggesting a four coordinate complex compound. Keywords: Anisidineacetylacetone, complex compound, stability constant, potentiometry.

Tracking InfraRed signatures of drugs in cancer cells by Fourier Transform microspectroscopy

Aimed at developing accurate, reliable and cost-saving analytical techniques for drugs screening we evaluated the potential of Fourier Transform (FT) InfraRed (IR) microspectroscopy (microFTIR) as a quantitative pre-diagnostic approach for the rapid identification of IR signatures of drugs targeting specific molecular pathways causing Chronic Myeloid Leukemia (CML). To obtain reproducible FTIR absorbance spectra at the necessary spatial resolution we optimized sample preparation and acquisition parameters on a single channel Mercury-Cadmium-Telluride (MCT) detector in the spectral interval of frequencies from 4000 to 800 cm(-1). Single K562 cells were illuminated by Synchrotron Radiation (SR) and a number of ~15 K562 cells spread in monolayer were illuminated by a conventional IR source (Globar), respectively. Combining IR spectral data with the results of complementary biochemical investigations carried out in samples by different analytical methods we identified and cross-validated IR signatures of drugs targeting the oncogenic protein BCR/ABL and its associated abnormal tyrosine kinase activity in K562 cell line. Unsupervised pattern recognition performed by Hierarchical Cluster Analysis (HCA) clustered the spectra of single K562 cells in two distinct groups roughly corresponding to living and to apoptotic cells, respectively. The corresponding IR spectral profiles were assumed to represent drug-resistant and drug-sensitive cells. Significant variations with increasing percentages of apoptotic cells were observed after the treatment of K562 cells with drugs that directly or indirectly target BCR/ABL. In conclusion, we suggest that microFTIR associated with multivariate data analysis may be useful to assess drug compounds in ex vivo cancer cell models and possibly peripheral blast cells from CML patients.

English

&nbsp; As part of the ongoing research for more effective antimalarial drug, Fe (III) complex of mefloquine hydrochloride (antimalarial drug) was synthesized using template method. Mefloquine was tentatively found to have coordinated through the hydroxyl and the two nitrogen atoms in the quinoline and piperidine in the structure, respectively. Characterization has been done on the basis of analytical, conductance, atomic absorption, magnetic measurement, electronic and Infra-red spectrometry. From analytical data, the stoichiometry of the complex has been found to be 1:1. Infra-red spectral data also suggest that the ligand (mefloquine) behaves as a tridentate ligand with N:N:O donor sequence towards the metal ion. On the basis of the above physico-chemical data it is proposed that the complex is assigned octahedral geometry. The antimicrobial activities of mefloquine metal complex exhibited greater inhibition than the parent ligand. The ligand and metal complex were screened for their toxicological activities at the dose of 6.66 mg/kg body weight twice daily for seven days on the alkaline phosphatase (ALP), alanine aminotranferase (ALT) and aspartate aminotransferase (AST) activities of rat serum, liver and kidney. Overall, it was revealed that both mefloquine and its metal complex might show mild toxicity particularly on the liver and kidney. &nbsp; Key words:&nbsp;Fe(III) complex, synthesis, anti-malarial drug, antimicrobial, toxicology.

Fe (III) complex of mefloquine hydrochloride: Synthesis, antimicrobial and toxicological activities

As part of the ongoing research for more effective antimalarial drug, Fe (III) complex of mefloquine hydrochloride (antimalarial drug) was synthesized using template method. Mefloquine was tentatively found to have coordinated through the hydroxyl and the two nitrogen atoms in the quinoline and piperidine in the structure, respectively. Characterization has been done on the basis of analytical, conductance, atomic absorption, magnetic measurement, electronic and Infra-red spectrometry. From analytical data, the stoichiometry of the complex has been found to be 1:1. Infra-red spectral data also suggest that the ligand (mefloquine) behaves as a tridentate ligand with N:N:O donor sequence towards the metal ion. On the basis of the above physico-chemical data it is proposed that the complex is assigned octahedral geometry. The antimicrobial activities of mefloquine metal complex exhibited greater inhibition than the parent ligand. The ligand and metal complex were screened for their toxicological activities at the dose of 6.66 mg/kg body weight twice daily for seven days on the alkaline phosphatase (ALP), alanine aminotranferase (ALT) and aspartate aminotransferase (AST) activities of rat serum, liver and kidney. Overall, it was revealed that both mefloquine and its metal complex might show mild toxicity particularly on the liver and kidney.

Comparison of Calibration Models Based on Near Infrared Spectroscopy Data for the Determination of Plant Oil Properties

The aim of this study was to compare the prediction efficiency of different type of linear calibration models using near infrared (NIR) absorbance spectral data of vegetable oils. The applied model types were the PCA-MLR (principal component analysis-multiple linear regression), the PLS (partial least squares regression), the PCA-ANN (principal component analysis-artificial neural network) and the GA-ANN (genetic algorithm-artificial neural network). The calibrations were executed on the models for the determination of the concentration of oleic acid of vegetable oils and the performances of the different models were determined using external validation. During external validation the built models were tested with vegetable oil samples of which oleic acid content was known and was not included in the calibration sample set. The comparison of the models was executed on the basis of the accuracy of the prediction.

Detailed characterisation of sulphur and nitrogen components in a multifunctional, ashless lubricant additive by spectroscopic and chromatographic techniques

AbstractThe work reported here used infrared (IR), multinuclear nuclear magnetic resonance (NMR), and chromatographic techniques to identify and characterise a commercial sulphur‐ and nitrogen‐containing ashless multifunctional additive. The proper assignment of signals in the 1H/13C NMR and IR spectra of the sample has facilitated the identification of different types of sulphur‐ and nitrogen‐containing components. The methodology involves investigation by NMR and IR spectroscopies, thin‐layer chromatography (TLC) and high‐performance liquid chromatogaphy (HPLC) techniques to elucidate the types of components present. This requires the generation of NMR and IR spectral data for standard compounds of alkyl sulphides with different sulphur content and alkyl chain, and nitrogen and sulphur components such as thiadiazole, imidazoline, triazole, etc., and spectral comparison with the spectra of the unknown sample. Further, these components have been separated by silica/alumina column chromatographic and preparative TLC techniques and subsequently analysed for their exact chemical structure by spectroscopic techniques. The combined spectroscopic and chromatographic analyses have yielded the presence of four types of components: di‐t‐octyl polysulphide, di‐t‐octyl thiadiazole, a component containing amine ether functionality, and alkyl amine salts of mono/dialkyl phosphoric acid.

Characteristics of Hydroxypropyl Methylcellulose Influencing Compactibility and Prediction of Particle and Tablet Properties by Infrared Spectroscopy

Particle characteristics, chemical substitution, compaction behavior, and tablet properties of hydroxypropyl methylcellulose powders from two different suppliers were related using multivariate data analysis. By Principal Component Analysis it was shown that the the degree of substitution of the HPMC powders did not correlate to the particle and compaction properties as strongly as anticipated. Particle shape and powder surface area seem to be more important for the compaction behaviour of the powders than the degree of substitution. In addition, particle and tablet properties were predicted from infrared spectral data. Fourier transform infrared (FTIR) and near infrared (NIR) spectral data of the powders were combined with measured values of the particle characteristics, compaction behavior, and tablet properties using the multivariate data analysis program SIMCA 7.1. Properties like density, particle shape, tablet tensile strength, and drug release characteristics of the HPMC powders and corresponding tablets in this study could be predicted using Partial Least Squares models. In conclusion, the particle shape and powder surface area of HPMC powders seem to be important factors for the quality of tablet attained. Further, this study confirms that NIR and FTIR analysis used in combination with multivariate analysis are powerful tools for predicting the properties of materials and the quality of the end product.

Variable Selection in near Infrared Spectroscopy Based on Significance Testing in Partial Least Squares Regression

A jack-knife based method for variable selection in partial least squares regression is presented. The method is based on significance tests of model parameters, in this paper applied to regression coefficients. The method is tested on a near infrared (NIR) spectral data set recorded on beer samples, correlated to extract concentration and compared to other methods with known merit. The results show that the jack-knife based variable selection performs as well or better than other variable selection methods do. Furthermore, results show that the method is robust towards various cross-validation schemes (the number of segments and how they are chosen).

Organosolv pretreatment for enzymatic hydrolysis of poplars: isolation and quantitative structural studies of lignins

Lignins could become important sources of chemical feedstocks and fuels if fractionation of the polymeric constituents of lignocellulosic materials could be improved. To utilize these polymeric components, it is important to understand their composition, chemical characteristics, and properties as a function of how the separation of the polymers is conducted. This paper presents characterization of several lignins as a function of fractionation method and isolation. Organosolv lignins were isolated from pulping liquors obtained by pulping Populus tremuloides (aspen) at 165 °C for 1–2.5 h with methanol: water (70 : 30 by volume). Pulping catalysts were various concentrations of mineral acids (H2SO4 or H3PO4) or salts (NaHSO4). Lignins were isolated by: (1) precipitation through the addition of water of the major lignin fraction (water–insoluble lignin) and (2) solubilization in acetone to yield a small fraction of acetone-soluble lignin. The characterization of these materials was performed through extensive quantitative 13C-NMR and by use of the Distortionless Enhancement by Polarization Transfer (DEPT) NMR sequence to assess the major types of structures formed under these conditions. In addition infra-red spectral data obtained using the DRIFT technique were employed to investigate a few of the structural characteristics. Simple functional groups were also analyzed by chemical methods for comparison. Correlation of differences in the structures of the organosolv lignins was made with the severities of the organosolv pretreatments which were expressed in terms of combined severity factors that incorporated time, temperature, and catalyst effects (pH of the pulping liquor). At low severity, the alkyl aryl ether bonds, the predominant bonds in native lignin, were hydrolyzed leading to materials with low ether bond content, high phenolic hydroxyl content, some methanol incorporation at the side chain, and a small amount of carbon-carbon condensed structures. Quantitation of minor structures such as syringaresinol and p-hydroxybenzoate is given, and the key types of structures present. As the severity increases, a higher extent of carbon-carbon condensation and side-chain degradation was observed while the ether bonding content was decreased. These lignins have low apparent weight-average molecular weights and low polydispersities. The lignins isolated from high severity organosolv pretreatments were completely different from native lignins. The degree of side chain degradation was high, and the number of carbons conventionally employed to describe a lignin repeating unit was substantially decreased from nine to eight or less.

The star plot: an alternative display method for multivariate data in the analysis of food and drugs

The star plot (SP) is a method of displaying multivariate data. It can be used to display data with more than two variables. Combined with principal component analysis (PCA), more than two PCs can be displayed in one plane. Different variants of this method are applied to an atomic absorption spectrometry (AAS) data set and to three near infra-red (NIR) spectral data sets. The results show that SP offers an easy way of visualising the multivariate data for food and drugs in a plane, and it is able to help the analyst to identify and to detect different qualities of food and drug composition. Moreover, when an object is added or removed, the PC's must be computed all over again, which is not the case for the SP-plot. The application of SP to the examples presented in the text suggests that the SP approach can be applied as an alternative method for displaying multivariate chemometric data in place of PCA or, to improve visualisation of the results already obtained with PCA.

Determination of Cholinesterase in Human Blood Using near Infrared Spectroscopy

The level of cholinesterase in the human blood is a very good indicator of liver function. In this study we desrcibe the relationship between cholinesterase values obtained with routine laboratory methods and near infrared (NIR) spectral data of 72 individuals with a wide range of cholinesterase levels. NIR spectra were measured with a SPECTRALYZER 10–25 (PMC) computerised research analyser. The relationship of laboratory data and values of the second derivative of the log (1/ TF) spectra measured at different wavelengths was determined with multiple linear regression (MLR) analysis using three-term linear summation equations. A correlation coefficient ( r) of 0.89 and a standard error of calibration ( SEC) of 987 units L−1 (U/L) of the enzyme were obtained. Our results indicate that NIR measurements of cholinesterase in the human blood serum can be related to the analytical data obtained with routine laboratory methods. NIR spectroscopy is a rapid, accurate, and inexpensive method for determining various constituents in the human blood.