Discrimination of grassland species and their classification in botanical families by laboratory scale NIR hyperspectral imaging: preliminary results

in Talanta (in press)

The objective of this study was to discriminate by a NIR line scan hyperspectral imaging, taxonomic plant families comprised of different grassland species. Plants were collected from semi-natural meadows ... [more ▼]

The objective of this study was to discriminate by a NIR line scan hyperspectral imaging, taxonomic plant families comprised of different grassland species. Plants were collected from semi-natural meadows of the National Apuseni Park, Apuseni Mountains, Gârda area (Romania) according to botanical families. Chemometric tools such as PLS-DA were used to discriminate distinct grassland species, and assign the different species to botanical families. Species within the Poacea family and Other Botanical Families could be distinguished (R2=0.91 and 0.90, respectively) with greater accuracy than those species in the Fabacea family (R2=0.60). A correct classification rate of 99% was obtained in the assignment of the various species to the proper family. Moreover a complete study based on wavelength selection has been performed in order to identify the chemical compound related to each botanical family and therefore to the possible toxicity of the plant. This work could be considered as a first step for the development of a complete procedure for the detection and quantification of possible toxic species in semi-natural meadows used by grazing animals. [less ▲]

Chemometrics and chromatographic fingerprints to discriminate and classify counterfeit medicines containing PDE-5 inhibitors.

in Talanta (2012), 100

Chromatographic fingerprints recorded for a set of genuine and counterfeit samples of Viagra® and Cialis® were evaluated for their use in the detection and classification of counterfeit samples of these ... [more ▼]

Chromatographic fingerprints recorded for a set of genuine and counterfeit samples of Viagra® and Cialis® were evaluated for their use in the detection and classification of counterfeit samples of these groups of medicines. Therefore several exploratory chemometric techniques were applied to reveal structures in the data sets as well as differences among the samples. The focus was on the differentiation between genuine and counterfeit samples and on the differences between the samples of the different classes of counterfeits as defined by the Dutch National Institute for Public Health and the Environment (RIVM). In a second part the revealed differences between the samples were modelled to obtain a predictive model for both the differentiation between genuine and counterfeit samples as well as the classification of the counterfeit samples. The exploratory analysis clearly revealed differences in the data for the genuine and the counterfeit samples and with projection pursuit and hierarchical clustering differences among the different groups of counterfeits could be revealed, especially for the Viagra® data set. For both data sets predictive models were obtained with 100% correct classification rates for the differentiation between genuine and counterfeit medicines and high correct classification rates for the classification in the different classes of counterfeit medicines. For both data sets the best performing models were obtained with Least Square-Support Vector Machines (LS-SVM) and Soft Independent Modelling by Class Analogy (SIMCA). [less ▲]

Comments on “Uncertainty profiles for the validation of analytical methods” by Saffaj and Ihssane

in Talanta (2012), 88

Saffaj et al., recently proposed an uncertainty profile for evaluating the validity of analytical methods using the statistical methodology of γ-confidence β-content tolerance intervals. This profile ... [more ▼]

Saffaj et al., recently proposed an uncertainty profile for evaluating the validity of analytical methods using the statistical methodology of γ-confidence β-content tolerance intervals. This profile assesses the validity of the method by comparing the method measurement uncertainty to a pre defined acceptance limit stating the maximum uncertainty suitable for the method under study. Several years earlier as stated by these authors a SFSTP (Société Française des Sciences et Techniques Pharmaceutique) commission has developed a similar profile called accuracy profile used to assess the validity of analytical methods. This accuracy profile also uses the methodology of statistical tolerance intervals, but β-expectation tolerance intervals. The uncertainty profile of Saffaj et al. and the accuracy profile of the SFSTP commission are both fulfilling the same final purpose. The core question is finally what statistical tolerance interval to use ? The aim of this letter to the editor is to discuss this question and provide arguments that β-expectation tolerance intervals should be prefered to assess the validity of the method as this type of interval give the guarantee that each future results has high probability to fall within pre-specified acceptance limits. [less ▲]

New approach to quantitative analysis of benzo[a]pyrene in food supplements by an immunochemical column test

in Talanta (2011), 85

Development and validation by accuracy profile of a method for the analysis of monoterpenes in indoor air by active sampling and thermal desorption-gas chromatography-mass spectrometry

in Talanta (2010), 82(4), 1230-1239

The technique of thermal desorption (TD)-GC/MS was evaluated for the measurement of monoterpenes in indoor air. The validation strategy was intentionally oriented towards routine use and the reliability ... [more ▼]

The technique of thermal desorption (TD)-GC/MS was evaluated for the measurement of monoterpenes in indoor air. The validation strategy was intentionally oriented towards routine use and the reliability of the method rather than extreme performance. For this reason, validation by accuracy profile was chosen. The accuracy profile procedure, which is based on the concept of total error (bias + standard deviation), guarantees that a known proportion of future results obtained with the method will be within acceptance limits. For all the compounds tested in the present study, α-pinene, α-terpineol, β-pinene, d-limonene, Δ3-carene, camphene, 1,8-cineole, p-cymene, linalool, but not in the case of carvone, the accuracy profile procedure established that at least 95% of the future results obtained would be within the ±15% acceptance limits of the validated method over the whole defined concentration range. Other parameters, such as selectivity, recovery, repeatability, stability of the molecules of interest and the effect of temperature, were also determined. The performance of the described method was finally evaluated by the analysis of indoor air from new timber frame constructions. [less ▲]

Building the quality into pellet manufacturing environment - feasibility study and validation of an in-line quantitative near infrared (NIR) method

in Talanta (2010), 83

The present study focuses on the implementation of an in-line quantitative near infrared (NIR) spectroscopic method for determining the active content of pharmaceutical pellets. The first aim was to non ... [more ▼]

The present study focuses on the implementation of an in-line quantitative near infrared (NIR) spectroscopic method for determining the active content of pharmaceutical pellets. The first aim was to non-invasively interface a dispersive NIR spectrometer with four realistic particle streams existing in the pellets manufacturing environment. Regardless of the particle stream characteristics investigated, NIR together with principal component analysis (PCA) was able to classify the samples according to their active content. Further, one of these particle stream interfaces was non-invasively investigated with a FT-NIR spectrometer. A predictive model based on Partial Least Squares (PLS) regression was able to determine the active content of pharmaceutical pellets. The NIR method was finally validated with an external validation set for an API concentration range from 80 to 120 % of the targeted active content. The prediction error of 0.9 % (root mean standard error of prediction, RMSEP) was low, indicating the accuracy of the NIR method. The accuracy profile on the validation results, an innovative approach based on tolerance intervals, demonstrated the actual and future performance of the in-line NIR method. Accordingly, the present approach paves the way for real-time release-based quality system. [less ▲]

Isotope coded protein label quantification of serum proteins--comparison with the label-free LC-MS and validation using the MRM approach.

in Talanta (2010), 80(4), 1487-95

Protein quantification based upon mass spectrometry is gaining ground in diverse applications of biological and clinical relevance. The present article focuses on one of the most complex biological fluids ... [more ▼]

Protein quantification based upon mass spectrometry is gaining ground in diverse applications of biological and clinical relevance. The present article focuses on one of the most complex biological fluids - serum - and provides a novel ICPL based quantification protocol. The results are compared to a label-free (data independent alternate scanning) absolute quantification method. The validation is performed using MRM based protein quantification technique. Regarding the ICPL approach, serum samples used in this study were depleted of high abundant proteins, labeled with ICPL and fractionated according to their respective pI (3-5, 5-7 and 7-12). The samples were further subjected to tryptic digestion followed by treatment with the Glu-C enzyme. The peptides were analyzed on a 2D-nano-LC system using four different concentrations of salt injections (45, 75, 150 and 500 mM ammonium acetate). The LC system was connected on-line with the electrospray ion-trap mass spectrometer. For the label-free quantification the serum samples were depleted and digested with trypsin. A proteome-wide comparison was performed using highly reproducible LC and data independent alternate scanning in conjunction with a high mass accuracy orthogonal time-of-flight mass spectrometer. Selected proteins, found by both methods, were validated using the MRM approach. For this purpose non-depleted tryptically digested serum samples were analyzed by LC coupled with a triple-quadrupole MS. The relative protein quantification using ICPL and mass spectrometry allowed for the detection of approximately 200 proteins, whereas about 2/3 of those contained the ICPL label and could therefore be quantified. Label-free approach used no fractionation, less sample and was able to identify and quantify over 110 proteins. The identified proteins covered generally 3-4 orders of magnitude of protein concentration in human serum. Changes in relative abundance of eight proteins were validated using MRM. This study, for the first time, shows the ability of the relative protein quantification based upon ICPL and 2D-LC-MS/MS to quantify serum biomarkers. It provides two additional label-free approaches that could validate and bring additional value to the label-based results, offering a starting point for comprehensive proteomics studies aiming at revealing biomarkers of clinical relevance. [less ▲]

A new statistical method for the automated detection of peaks in UV-DAD chromatograms of a sample mixture

in Talanta (2009), 79

One of the major issues within the context of the fully automated development of chromatographic methods consists of the automated detection and identification of peaks coming from complex samples such as ... [more ▼]

One of the major issues within the context of the fully automated development of chromatographic methods consists of the automated detection and identification of peaks coming from complex samples such as multi-component pharmaceutical formulations or stability studies of these formulations. The same problem can also occur with plant materials or biological matrices. This step is thus critical and time-consuming, especially when a Design of Experiments (DOE) approach is used to generate chromatograms. The use of DOE will often maximize the changes of the analytical conditions in order to explore an experimental domain. Unfortunately, this generally provides very different and “unpredictable” chromatograms which can be difficult to interpret, thus complicating peak detection and peak tracking (i.e. matching peaks among all the chromatograms). In this context, Independent Components Analysis (ICA), a new statistically based signal processing methods was investigated to solve this problem. The ICA principle assumes that the observed signal is the resultant of several phenomena (known as sources) and that all these sources are statistically independent. Under those assumptions, ICA is able to recover the sources which will have a high probability of representing the constitutive components of a chromatogram. In the present study, ICA was successfully applied for the first time to HPLC–UVDAD chromatograms and it was shown that ICA allows differentiation of noise and artifact components from those of interest by applying clustering methods based on high-order statistics computed on these components. Furthermore, on the basis of the described numerical strategy, itwas also possible to reconstruct a cleaned chromatogram with minimum influence of noise and baseline artifacts. This can present a significant advance towards the objective of providing helpful tools for the automated development of liquid chromatography (LC) methods. It seems that analytical investigations could be shortened when using this type of methodologies. [less ▲]

Direct determination of tagitinin C in Tithonia diversifolia leaves by on-line coupling of supercritical carbon dioxide extraction to FT-IR spectroscopy by means of optical fibres

in Talanta (2007), 71(2), 911-917

Supercritical fluid extraction (SFE) with carbon dioxide as extraction medium was on-line coupled to a FT-IR spectrometer equipped with a Mercury Cadmium Telluride (MCT) detector using a tailor-made high ... [more ▼]

Supercritical fluid extraction (SFE) with carbon dioxide as extraction medium was on-line coupled to a FT-IR spectrometer equipped with a Mercury Cadmium Telluride (MCT) detector using a tailor-made high-pressure fibre optic flow cell. This method was optimised and developed for the monitoring in real time and the quantification of dynamic extractions of tagitinin C from Tithonia.diversifolia leaves. In order to demonstrate the method ability to allow the direct quantification of tagitinin C in the extract medium the standard addition method was used. The area integration Of Curves obtained by plotting the absorbance of the highly specific C=O stretching vibration at 1668 cm(-1) versus time (i.e. extractograms) was used as instrumental response. The SFE/FT-IR process was successfully validated using the accuracy profile as decision tool. On this basis, a linear regression model was chosen for the calibration curve. The relative standard deviation for repeatability and intermediate precision were between 0.8 and 3.1 %, respectively. Moreover, the method was found to be accurate as the two-sided 95% beta-expectation tolerance interval did not exceed the acceptance limits of 85 and 115% on the analytical range investigated (500-2500 mu g of added amount of tagitinin Q. The proposed method allowed the non-destructive extraction of tagitinin C and its on-line quantitative determination in less than 25 min thus facilitating the subsequent experiments or the pharmacological studies performed on this compound. [less ▲]

LC method for the determination of R-timolol in S-timolol maleate: Validation of its ability to quantify and uncertainty assessment.

in Talanta (2006), 68(4), 1166-75

This article presents the validation results of a chiral liquid chromatographic (LC) method previously developed for the quantitative determination of R-timolol in S-timolol maleate samples. A novel ... [more ▼]

This article presents the validation results of a chiral liquid chromatographic (LC) method previously developed for the quantitative determination of R-timolol in S-timolol maleate samples. A novel validation strategy based on the accuracy profiles was used to select the most appropriate regression model, to assess the method accuracy within well defined acceptance limits and to determine the limits of quantitation as well as the concentration range. The validation phase was completed by the investigation of the risk profiles of various acceptable regression models in order to ensure the risk of obtaining the future measurements outside the acceptance limits fixed a priori. On the other hand, the present paper also shows how data used in this validation approach can be used to estimate the measurement uncertainty. The uncertainty derived from beta-expectation tolerance interval (sigma(Tol)(2)), which is equal to the uncertainty of measurements as well as the expanded uncertainty (U(x)) using a coverage factor k=2 was estimated. The uncertainty estimates obtained from validation data were finally compared with those obtained from interlaboratory and robustness studies. [less ▲]