Chromatographic Signals Research Articles

Implementation of multiobjective decision-making algorithms and image analysis in HPTLC-guided extraction optimization of natural products

A new, efficient, and low-cost approach for monitoring extraction optimization was proposed based on high-performance thin-layer chromatography (HPTLC) coupled with digital image analysis. Since HPTLC produces rich chromatographic signals corresponding to various analytes which may be differently affected by extraction conditions, four multicriteria decision-making (MCDM) techniques were compared for their ability to aggregate multiple chromatographic responses: Derringer's desirability approach, Technique for Order of Preference by Similarity to Ideal Solution (TOPSIS), Preference Ranking Organization Method for Enrichment Evaluations (PROMETHEE-2), and the Sum of ranking differences (SRD). Ultrasound-assisted extraction (UAE) of green tea leaves with ethanol-water mixtures was used as a model system. The amount of ethanol and extraction time were varied according to the central composite design. Ranking eleven extracts by Derringer's desirability approach, TOPSIS, and PROMETHEE-2 showed the same results. SRD analysis yielded slightly different results from previous methods. Response surface models based on the previous three MCDM approaches demonstrated that extraction conditions with moderate amounts of ethanol (73%) and extraction times (46 min) lead to optimal chromatographic profiles. Optimization performed on individual peaks tentatively corresponding to rutin, chlorophyll, and gallic acid may lead to different results. Aside from natural products, the proposed approach has the potential to be implemented in various extraction optimizations.

Multiobjective optimization of effect-directed planar chromatography as a promising tool for fast selection of polypotent natural products

A new method for efficiently selecting polypotent natural products is proposed in this study. The method involves using effect-directed HPTLC data and multiobjective optimization algorithms to extract chromatographic signals from HPTLC bioassay images. Three different multiobjective optimization methods, namely Derringer's desirability approach, Technique for order of preference by similarity to ideal solution (TOPSIS), and Sum of ranking differences (SRD), were applied to the chromatographic signals. In combination with jackknife cross-validation, Derringer's approach and TOPSIS demonstrated high similarity in finding the best (most polypotent), next to the best, next to the worst, and worst (least polypotent) extracts, while the SRD resulted in slightly different outcomes.Furthermore, a new method for identifying the chromatographic features that characterize the most polypotent extracts was proposed. This method is based on partial least square regression (PLS) and can be used in combination with HPTLC-chemical fingerprints to predict the desirability of new extracts. The resulting PLS models demonstrated high statistical performance with determination coefficients ranging from R2 = 0.885 in the case of Derringer's desirability, to 0.986 for TOPSIS. However, the PLS modeling of SRD values was not successful.

Study of the process of tetracycline absorption by soil and its transformation during acid desorption

Introduction. Currently, control over the soil entry of antibiotics used in agriculture is becoming an urgent problem of environmental hygiene. Tetracycline can enter the soil with the excrement of domestic animals and affect biological objects, both microbiological and plant. The chemical form of tetracycline in the soil and the options for its transformation, in particular during sample preparation for analysis, are factors that determine the intensity of this effect and the reliability of analytical control. The lack of information about the transformation of the drug under chemical influence determined the relevance of the research. Materials and methods. The studies were performed using the Stayer chromatographic system with a Shodex IC YS-50 150/4.6 cation column and a Kromasil C18 HPLC column with amperometric and conductometric detection. The objects of research were model soil samples with different tetracycline contents. When conducting research, soddy-podzolic soil from the «Nemchinovka» experimental field (Moscow region) and GSO No. chernozem were used. Results. Solutions obtained after acid-methanol desorption of tetracycline from soil samples were studied using HPLC and IC (Ionochromatographic methods). As a result of desorption, complex forms of substances, including both natural organic substances of the soil and tetracycline components, were established to pass into the aqueous phase. These forms of substances are fixed with a Shodex IC YS-50 cation exchange column and are not fixed by HPLC with a Kromasil C18 column. The possibility of isolating a chromatographic signal corresponding to the tetracycline component using ion chromatography has been demonstrated. Limitations. To create a method for measuring tetracycline in soil, it is necessary to test a larger number of soil species that differ in the content of organic matter to identify in detail the interfering effect of the organic matrix during chromatographic analysis. Conclusion. Research has shown tetracycline chemically to bind to soil matter, forming cationic complexes. After treating the soil with a mixture of concentrated hydrochloric acid and methanol, tetracycline is quantitatively extracted from the soil in combination with natural soil organic matter. These forms of substances are detected by a Shodex IC YS-50 cationic column and are not detected by HPLC with a Kromasil C18 column. Selective analysis of the cationic form containing the tetracycline moiety is possible.

The Impact of Water as an Additive on the Elution of Some Basic Organic Compounds in Supercritical Fluid Chromatography.

In this study, water was used as an additive in the methanol-modified carbon dioxide-based eluent for the elution of some basic organic compounds from a hybrid silica column via supercritical fluid chromatography (SFC). The experiments were applied to sulfonamides, propranolol, and other organic nitrogen compounds involving aromatic rings from different classes of amine, pyrimidine, and purine with different pKa values (the pKa values for the studied analytes range from 4.6 to 10.4). The results revealed different responses to the different percentages of water addition. Adding 1~2% of water to the modifier (methanol) led to a positive effect manifested by more symmetrical peak shapes and reduced retention times for most compounds. The key factor for this improvement in the properties of chromatographic peaks is due to the adsorption of water on the silanol groups of the stationary phase, consequently resembling the phenomena observed in hydrophilic interaction liquid chromatography (HILIC). Moreover, the availability of hydrogen bond acceptor and donor sites in the analyte structure is an important factor to be considered when adding water as an additive to the modifier for improving the chromatographic peaks. However, introducing water in an amount higher than 3% resulted in perturbed chromatographic signals. It was also found that water as an additive alone could not successfully elute propranolol from the hybrid silica column with an acceptable peak shape; thus, the addition of a strong base such as amine salts was also necessary. The proposed use of a particular amount of water in the mobile phase could have a positive effect compared to the same mobile phase without water, improving the chromatographic peak properties of the elution of some basic organic compounds from the hybrid silica column.

Assessment of adulteration of sage (Salvia sp.) with olive leaves using high‐performance thin‐layer chromatography, image analysis, and multivariate linear modeling

AbstractAccording to the study carried out at the University of Bristol, 60% of oregano spices present on the European Union (EU) market are adulterated with olive, myrtle, cistus, and hazelnut leaves. According to the same authors, the sage products are adulterated by similar bulking agents. The aim of this study was to assess possibilities for detection of sage adulteration by olive leaves using high‐performance thin‐layer chromatography (HPTLC) coupled with digital image analysis and multivariate linear regression/classification (partial least squares and partial least squares discriminant analysis). Twenty‐four samples (4 pure sage leaves, 4 pure olive leaves, and 16 mixtures of olive and sage leaves with content of added olive leaves varying in 5%, 10%, 20%, and 50%) have been prepared, extracted, and analyzed under normal‐phase conditions. Several derivatization methods were tested, and derivatized HPTLC plates were inspected under visible or ultraviolet light. Digital images of chromatograms were recorded. In order to minimize effects of intraplate and interplate peak shifts, background changes, and baseline drifts, correlation‐optimized warping, standard normal variate, and mean centering were applied to acquired signals. Partial least squares and partial least squares discriminant analysis models with moderate complexity (two to four latent variables) based on chromatographic signals obtained after derivatization by FeCl3, anisaldehyde–sulfuric acid, and 2,2‐diphenyl‐1‐picrylhydrazyl demonstrated good statistical performances with R2 ranging 0.894–0.998 and relative prediction error of 4–12%. Misclassification error <4% was obtained in the case of 2,2‐diphenyl‐1‐picrylhydrazyl and anisaldehyde–sulfuric acid derivatization. Therefore, HPTLC combined with multivariate image analysis, signal processing, and linear modeling proved to be promising, cost‐effective chromatographic tool for assessment of sage adulteration by olive leaves.

Deep learning-based high performance liquid chromatography for food analysis

Abstract This paper presents a study on the determination of synthetic pigments using high performance liquid chromatography (HPLC) method combined. A retention value qualitative approach, combined with an uncertainty assessment algorithm for the determination of pigment content, was used for the simultaneous determination of nine synthetic pigments, namely, lemon yellow, amaranthine red, indigo, carmine, sunset yellow, brilliant blue, seductive red, erythrosine, and seductive red, in foodstuffs by reversed-phase high-performance liquid chromatography (RP-HPLC). The sample pretreatment method was optimized, and the chromatographic conditions were set to investigate the UV determination wavelength, mobile phase, column temperature, and wavelength of synthetic pigments. Under the same mobile phase and column conditions, the results indicated that the components’ retention times did not significantly fluctuate with the change in column temperature. The results showed that the chromatographic response signals of lemon yellow, sunset yellow and seductive red were higher at the UV determination wavelength of 254 nm, so 254 nm was finally determined as the UV detection wavelength in this experiment. Mobile phase A: methanol, B: ammonium acetate (0.02mo/L) using gradient elution, the separation degree R>1.5, and the symmetry and stability of the chromatogram were better. The separation of the components was good, and the peak shape was sharp and symmetric when the column temperature was 35 ℃, so the column temperature was chosen to be 35 ℃, and the establishment of the chromatographic conditions was thus completed.

Impact of thermal desorption tubes on the variability of exhaled breath data

Due to the overall low abundance of volatile compounds in exhaled breath, it is necessary to preconcentrate the sample prior to traditional thermal desorption (TD) gas chromatography mass spectrometry analysis. While certain aspects of TD tubes, such as volatile storage, have been evaluated, many aspects remain uncharacterized. Two common TD tubes, Tenax TA and Biomonitoring 5TD tubes, were evaluated for background content and flow rate variability. The data illustrate that the Biomonitoring 5TD tubes have the highest number (23) and abundance of background contamination greater than 3x the mean noise when compared to Tenax TA (13) and empty tubes (9). Tentative identifications of the compounds in the background contamination experiment show that greater than 59% (16/27) of the compounds identified have been reported in the breath literature. The data illustrate the TD tube background abundance could account for more than 70% of the chromatographic signal from exhaled breath for these select compounds. Flow rate measurements of 200 Tenax TA and 200 Biomonitoring 5TD tubes show a large range in measured flow rates among the TD tubes (Tenax: 252.9–284.0 ml min−1, 5TD: 220.6–255.1 ml min−1). Finally, TD tubes of each type, Tenax TA and Biomonitoring 5TD, previously established to have high, medium, and low flow rates, show insignificant differences (p > 0.05) among the tubes of different flow rates, using both gas standards and an exhaled breath from a peppermint experiment. Collectively, these results establish overall background compounds attributed to each TD tube type tested. Additionally, while measured flow rate variability is present and plausibly impacts exhaled breath results, the data demonstrate no statistically significant difference was observed between tubes showing high, medium, and low flow rates from two separate sample types.

Tile-Based Random Forest Analysis for Analyte Discovery in Balanced and Unbalanced GC × GC-TOFMS Data Sets.

In this study, we introduce a new nontargeted tile-based supervised analysis method that combines the four-grid tiling scheme previously established for the Fisher ratio (F-ratio) analysis (FRA) with the estimation of tile hit importance using the machine learning (ML) algorithm Random Forest (RF). This approach is termed tile-based RF analysis. As opposed to the standard tile-based F-ratio analysis, the RF approach can be extended to the analysis of unbalanced data sets, i.e., different numbers of samples per class. Tile-based RF computes out-of-bag (oob) tile hit importance estimates for every summed chromatographic signal within each tile on a per-mass channel basis (m/z). These estimates are then used to rank tile hits in a descending order of importance. In the present investigation, the RF approach was applied for a two-class comparison of stool samples collected from omnivore (O) subjects and stored using two different storage conditions: liquid (Liq) and lyophilized (Lyo). Two final hit lists were generated using balanced (8 vs Eight comparison) and unbalanced (8 vs Nine comparison) data sets and compared to the hit list generated by the standard F-ratio analysis. Similar class-distinguishing analytes (p < 0.01) were discovered by both methods. However, while the FRA discovered a more comprehensive hit list (65 hits), the RF approach strictly discovered hits (31 hits for the balanced data set comparison and 29 hits for the unbalanced data set comparison) with concentration ratios, [OLiq]/[OLyo], greater than 2 (or less than 0.5). This difference is attributed to the more stringent feature selection process used by the RF algorithm. Moreover, our findings suggest that the RF approach is a promising method for identifying class-distinguishing analytes in settings characterized by both high between-class variance and high within-class variance, making it an advantageous method in the study of complex biological matrices.

Study of Selected Parameters of Analytical Methods to Control the Contamination of Propolis Tincture

Analysis of honeybees and their products can provide crucial information about the degree of environmental contamination by pesticide residues. One of the promising products is propolis tincture which is a complex mixture. It is essential to modify the procedure in order to reduce the potential contamination of the analytical instrument used to determine pesticides. QuEChERS sample preparation method (acronym of Quick, Easy, Cheap, Effective, Rugged and Safe) for the extraction of pesticides from the propolis tincture was proposed. Satisfactory extraction recoveries in the range of 70–120 % for 43 out of 47 pesticides have been obtained using C18, PSA and Florisil cleaning sorbents in the second step of QuEChERS procedure. Matrix effects and influence of interferences on the chromatographic signal were studied in detail.

Exploring the Effect of Different Storage Conditions on the Aroma Profile of Bread by Using Arrow-SPME GC-MS and Chemometrics.

In the present feasibility study, SPME Arrow-GC-MS method coupled with chemometric techniques, was used for investigating the impact of two different storage conditions, namely freezing and refrigeration, on volatile organic compounds (VOCs) of different commercial breads. The SPME Arrow technology was used as it is a novel extraction technique, able to address issues arising with traditional SPME fibers. Furthermore, the raw chromatographic signals were analysed by means of a PARAFAC2-based deconvolution and identification system (PARADISe approach). The use of PARADISe approach allowed for an efficient and rapid putative identification of 38 volatile organic compounds, including alcohols, esters, carboxylic acids, ketones, and aldehydes. Additionally, Principal Component Analysis, applied on the areas of the resolved compounds, was used to investigate the effects of storage conditions on the aroma profile of bread. The results revealed that the VOC profile of fresh bread is more similar to the one of bread stored in the fridge. Furthermore, there was a clear loss of aroma intensity in frozen samples, which could be explained by phenomena related to different starch retrogradation that occurs during freezing and refrigeration. However, considering the limited number of investigated samples, this study must be considered as a proof of concept; a more statistically representative sampling and further examinations of other properties, such as bread texture, need to be performed to better understand whether samples destined for eventual analysis should be frozen or refrigerated.

Fabrication of a Composite Monolithic Column of Poly (IL@MOF) for Adsorption of Acacetin in Medicinal and Food Homologous Plants

AbstractIn this study, a poly (IL@MOF) composite monolithic column was synthesized using a simple and easy method. By adjusting the ratio of monomers, porogenic agents and cross‐linking agents, a macroporous composite monolith composed of metal organic framework (MOF) and ionic liquids (IL) was constructed. It was used as a high‐performance solid phase extraction (SPE) sorbent for the extraction of acacetin from medicinal and food homologous plants. The proposed SPE‐HPLC method for determination of acacetin had the advantages of high precision (0.06∼1.00 %), wide linear range (0.01∼250 μg mL−1) and low detection limits (3.26 ng mL−1). The poly (IL@MOF) monolithic column had excellent repeatability as an adsorbent. After 300 adsorption/desorption cycles, the corresponding chromatographic signal had no obvious change. These results indicated that the poly (IL@MOF) composite monolithic column was an ideal adsorbents and that the proposed method had potential for the enrichment and purification of flavonoids from medicinal and food homologous plants.

The Mineral Oil Hydrocarbon Paradox in Olive Pomace Oils.

The aim of this work was to understand the actual content of mineral oil hydrocarbons (MOH) in olive pomace oil in order to contribute to the monitoring requested by EFSA for the food groups making a relevant impact on human background exposure. Such information will complement both the information inferred from the limits established by the EU and the interpretation of the coming toxicological risk assessment. At the same time, the origin of such a group of compounds is discussed. From the raw material to the commercial product, olive pomace oils were sampled and analyzed at different points and/or conditions. Through the ultimate online HPLC-GC-FID system, we gathered information on the MOH concentrations and molecular mass profiles (C-fractions), and through GCxGC-TOF/MS, we identified the key structures that prove the innocuousness of the mineral oil aromatic hydrocarbon (MOAH) fraction. Our approaches provided chromatographic signals on the C10-C50 range, rendering 33-205 mg/kg mineral oil saturated hydrocarbon (MOSH) and 2-55 mg/kg MOAH in the commercial product. The results confirmed that the C25-C35 cut is the main fraction to which humans are exposed via olive pomace oil, showing concentrations highly dependent on the extraction process. Moreover, the identification of the main MOAH groups showed that in olive pomace oil, mainly 1- and 2-ring species were present, being virtually free of the carcinogenic 3-7 ring aromatics.

Development of an LC/MS/MS Method for Simultaneous Detection of 11 Polyphenols in Rat Plasma and Its Pharmacokinetic Application after Oral Administration of Coreopsis tinctoria Extract.

Eleven polyphenols, classified as flavonoid glycosides, flavonoid aglycones, and phenolic acids, are important bioactive components in the capitula of Coreopsis tinctoria (CCT). Nevertheless, their full pharmacokinetic profiles have not been demonstrated simultaneously. Therefore, a liquid chromatography - tandem mass spectrometry (LC/MS/MS) method was developed in the present work and used it to study the pharmacokinetics of these 11 compounds. We performed LC/MS/MS with a gradient mobile phase composed of water containing 0.1 % formic acid and acetonitrile containing 0.1 % formic acid on a Proshell 120 SB C18 column (2.1 mm×100 mm, 2.7 μm). We achieved a good chromatographic peak shape, resolution, and mass signal response, and multiple reaction monitoring facilitated the simultaneous detection of 11 analytes. In addition, we validated the selectivity, correlation coefficient, precision, extraction recovery, matrix effects, and stability of the LC/MS/MS method to be acceptable for 11 analytes in rat plasma. Subsequently, rats were orally administered with 50 % ethanol eluent of CCT (ECCT). Nine of 11 polyphenols were absorbed quickly (except for QCD and TCA), and their plasma levels peaked within 40 min. The exposure and Cmax values of flavonoid glycosides and phenolic acids were lower than those of flavonoid aglycones. This is the first report to demonstrate the pharmacokinetics of 11 polyphenols in ECCT, which may play an important role in future studies of the bioactive components of ECCT and their bioactive mechanisms.

Instrument-Agnostizing Methodology for Liquid Chromatography-Mass Spectrometry Systems.

Mass spectrometry is a powerful analytical technique used to identify unknown compounds, to quantify known compounds, and to elucidate the structure and chemical properties of molecules. Nevertheless, the transfer of data from one instrument to another is one of the main problems, and obtaining the same or similar information from an analogous instrument but from a different manufacturer or even with the same instrument after carrying out the analyses in different times spacing is not possible. Hence, a general methodology to provide a chromatographic signal (or chromatogram) independent of the instrument is needed. In this sense, this book chapter describes the standardization procedure of chromatographic signals obtained from mass spectrometry platforms to obtain instrument-agnostic chromatographic signals for the determination of standard retention scores. This parameter may be used for the quantification of compounds when different mass spectrometry platforms coupled to ultrahigh-performance liquid chromatography are employed.

Development of a new SPE UPLC-MS/MS method for extraction and quantitation of toluene diamine on gloves following toluene diisocyanate exposure.

Toluene diisocyanate (TDI) is a highly reactive isocyanate commonly used as a mixture of 2,4- and 2,6- isomers in the production of flexible foams. Exposure to TDI occurs primarily through vapour inhalation in workplaces where TDI is produced or used, but dermal exposure is also possible during some tasks. To ensure workplace safety, accurate monitoring of TDI and toluene diamine (TDA) levels is required. Methods of quantifying field effectiveness of gloves in preventing dermal exposure have not been established. Therefore, there is a need to develop a new practical method for assessing glove effectiveness for TDI/TDA. A new offline SPE UPLC-MS/MS method for the quantitation of TDA isomers from TDI-exposed gloves was developed. Gloves were dipped in a solution of 1% acetic acid leading to a full conversion to TDA. TDA-free amine compounds were derivatized with acetic anhydride to increase chromatographic retention and signal intensity. 2,4-Diaminotoluene-α, α, α-d3 (2,4-d3 -TDA) was selected as a surrogate standard to minimise the variability in sample preparation and instrumental sensitivity. The choice of UPLC-MS/MS operated in multiple reaction monitoring (MRM) mode allowed to reach much lower limits of detection (LOD). The LOD of the method was 6.86 and 2.83 ng/mL (0.03 and 0.01 μg) for 2,6-TDA and 2,4-TDA, respectively. The limit of quantitation (LOQ) was 22.85 and 9.42 ng/mL (0.11 and 0.05 μg) for 2,6-TDA and 2,4-TDA, respectively. A new UPLC-MS/MS analytical method has been developed to determine field effectiveness of gloves for preventing dermal exposure to TDI/TDA. The new technique overcomes some limitations for measuring putative dermal exposure to isocyanates and may be useful in exposure monitoring and future research on isocyanate health risks.

Smoothing of chromatographic signals by their approximation in the basis of Chebyshev-Hermite functions

The paper deals with assessing the scope of the approximation algorithm for smoothing chromatographic signals. The algorithm is based on Chebyshev-Hermite functions. For approximation, an algorithm is used that implies the calculation of the shift and scale factors for the basis functions, as well as the division of the signal into fragments. The smoothing error of the model signal is considered when it is approximated in the selected basis in comparison with the digital moving average filter. The error of smoothing the derivative of the signal and the position on the derivative of extremums is also investigated, a comparison is made, as in the previous case, with a digital moving average filter. As part of an experimental study, the nine most characteristic chromatographic peaks extracted from real chromatograms are processed in the work. To assess the quality of smoothing, the standard deviation of the noise and the residual are compared, and the distribution law of the residual is determined. According to the results of the study, restrictions are set on the maximum allowable value of the asymmetry coefficient of the processed chromatographic peaks. Thanks to the use of the chosen approximation approach, it is possible to solve the problem of smoothing chromatographic signals without attenuating the useful component. The computer algebra system Wolfram Mathematica 11.3 was used for calculations and graphical presentation of the simulation results.

Fast GC E-Nose and Chemometrics for the Rapid Assessment of Basil Aroma

The aim of this work is to assess the potentialities of the synergistic combination of an ultra-fast chromatography-based electronic nose as a fingerprinting technique and multivariate data analysis in the context of food quality control and to investigate the influence of some factors, i.e., basil variety, cut, and year of crop, in the final aroma of the samples. A low = level data fusion approach coupled with Principal Component Analysis (PCA) and ANOVA—Simultaneous Component Analysis (ASCA) was used in order to analyze the chromatographic signals acquired with two different columns (MXT-5 and MXT-1701). While the PCA analysis results highlighted the peculiarity of some basil varieties, differing either by a higher concentration of some of the detected chemical compounds or by the presence of different compounds, the ASCA analysis pointed out that variety and year are the most relevant effects, and also confirmed the results of previous investigations.

Vacuum-assisted headspace solid-phase microextraction and gas chromatography coupled to mass spectrometry applied to source rock analysis

Abstract Vacuum-assisted headspace solid phase microextraction (Vac-HSSPME) with high temperature of extraction was used for source-rock analysis. Optimization of extraction conditions was performed by Doehlert experimental design (DD) in gas chromatography coupled to mass spectrometer detector (GC–MS). Samples from the same oil well were mixed to obtain a mean stratigraphic characteristic for extraction optimization. Source-rock samples were analyzed in the DD optimal conditions and the proposed Vac-HSSPME+GC–MS method was compared to the classical procedure (SARA). The identification of important biomarkers like steranes and pentacyclic terpanes was possible. Fingerprint comparison between both methods shows similarity for steranes profile of overall chromatographic signal and compounds distribution. Also, it was possible to assess theoretical kinetic considerations for the system, as it differs from most conditions reported in literature. Furthermore, no organic solvent was used during the extraction or analysis with Vac-HSSPME. Classifying the procedure as a green methodology, while being faster and cheaper for oil bearing source-rock analyses.

Impact of Cymbopogon flexuosus (Poaceae) essential oil and primary components on the eclosion and larval development of Aedes aegypti

The current study describes the effects of sub-lethal concentrations and constituent compounds (citral and geranyl acetate) of Cymbopogon flexuosus essential oil (EO) on the development of Aedes aegypti. We treated eggs with 6, 18, or 30 mg L−1 and larvae with 3 or 6 mg L−1 of EO and its major compounds (citral and geranyl acetate). Citral and geranyl acetate were evaluated at 18, 30, and 42 mg L−1 and compared with commercial growth inhibitors (diflubenzuron and methoprene). We measured larval head diameter, siphon length, and larval length. Finally, we examined concentrations of molt hormone (MH) and juvenile hormone III (JH III) using high-performance liquid chromatography coupled to mass spectrometry. All geranyl acetate concentrations decreased egg hatching, while EO altered molting among larval instars and between larvae and pupae, with an increase in the larval length (3 mg L−1: 6 ± 0.0 mm; 6 mg L−1: 6 ± 0.7 mm) and head width (3 mg L−1: 0.8 ± 0 mm; 6 mg L−1: 0.8 ± 0.0 mm) compared with the control group. We did not detect chromatographic signals of MH and JH III in larvae treated with C. flexuosus EO or their major compounds. The sub-lethal concentrations C. flexuosus EO caused a similar effect to diflubenzuron, namely decreased hormone concentrations, an extended larval period, and death.

Autoregressive modelling of chromatographic signals from urine samples for prostate cancer diagnosis

This article evaluates autoregressive modeling as a feature extraction method in a database of chromatographic signals from urine samples for non-invasive diagnostic support of prostate cancer in response to the research question: Can chromatographic signals from urine be characterized and used as a non-invasive method for cancer diagnosis? For this purpose, a database of 18 patients, 9 diagnosed with prostate cancer and 9 control patients, is consolidated, statistical methods are implemented to generate autoregressive coefficients from the data signals, and finally, the principal component analysis technique is applied for cross-class classification. As a result, a correct classification was obtained in the total number of samples validating the autoregressive modelling as a feature extraction method in contrast to the conventional methodology usually followed in chromatographic signal processing.