NMR and chemometric methods: a powerful combination for characterization of Balsamic and Traditional Balsamic Vinegar of Modena

This work presents the capability of NMR spectroscopy combined with Chemometrics in predicting the ageing of Balsamic and Traditional Balsamic Vinegar of Modena. The need of an analytical method is an important requirement for both research oriented and commercial evaluation of these very valuable products. ¹H NMR spectroscopy, based on the advantage of rapid sample analysis without any manipulation or derivatization, is here proposed as a valid tool to describe Balsamic and Traditional Balsamic Vinegar of Modena. For this purpose, 72 reliable samples, were divided into three different groups according to their ageing process: young (<12 years), old (>12 and <25 years) and extra old (>25 years). Hierarchical Projection to Latent Structures Discriminant Analysis (PLS-DA) allowed us to characterize the ageing process. Variables showing the largest VIP (Variable Importance in the Projection) were extracted from PLS-DA model, thus shedding lights onto the role played by specific compounds in this complex ageing process. Two robust classification models, were built by PLS-DA and Naïve Bayes classifier and compared to prove the accuracy of the representation on both training and test sets. The predictions obtained for 41 “unknown” vinegar samples with these both methods gave more than 80% agreement among them.     

NMR relaxation data for quality characterization of Balsamic vinegar of Modena

In this paper, 22 samples consisting of Balsamic vinegar of Modena and two Traditional Balsamic vinegar of Modena samples have been analyzed by means of ¹H NMR spectroscopy. Some selected resonances have been used for quantification and for T1 (spin-lattice relaxation time) measurements. Statistical protocols applied to NMR data for quantification of selected resonances revealed the possibility to differentiate the samples according to their ageing process. Additionally, T1 measurements revealed a strong correlation with the ageing process and these new data were added for improving the statistical model, which was used to predict T1 relaxation time of selected compounds for Balsamic vinegar samples. Our results indicate that the use of NMR data and statistical methods is a valid approach that can be successfully used for ageing characterization of Balsamic vinegar of Modena samples.     

Analytical method for the representation of atoms-in-molecules densities

We present analytic refinements and applications of the deformed atomic densities method [Fernández Rico, J.; López, R.; Ramírez, G. J Chem Phys 1999, 110, 4213-4220]. In this method the molecular electron density is partitioned into atomic contributions, using a minimal deformation criterion for every two-center distributions, and the atomic contributions are expanded in spherical harmonics times radial factors. Recurrence relations are introduced for the partition of the two-center distributions, and the final radial factors are expressed in terms of exponential functions multiplied by polynomials. Algorithms for the practical implementation are developed and tested, showing excellent performances. The usefulness of the present approach is illustrated by examining its ability to describe the deformation of atoms in different molecular environments and the relationship between these atomic densities and some chemical properties of molecules.     

中药质量控制与安全性评价中的分析化学

本文论述了中药现代化实施中进行质量控制的“5P”(GAP、GCP、GLP、GMP、GSP)系统工程 ;结合本实验室近年来以“5P”指导中药质量控制与安全性评价所做的一些工作 ,阐明了将分析化学应用于中药质量控制与安全性评价的策略与方法 ,提出了分析化学在中药现代化系统工程及重大科学问题的解决中所能发挥的重要作用。     

A coupled NMR and MS isotopic method for the authentication of natural vinegars

Summary The natural site-specific deuterium content and the overall ¹³C content of acetic acids, extracted from vinegars or obtained by chemical synthesis, were determined by NMR and mass spectrometries. The isotope ratios (D/H)_CH3 and the ¹³C deviation of these samples were compared to those of a series of ethanols of the same natural or synthetic origins. The different groups of natural and fossil acetic acids are represented in the ²H/¹³C isotopic plane and the discriminant function, which enables unknown samples to be assigned to a given group, is computed. A careful analysis of the repeatability of the entire analytical procedure and a study of known mixtures of natural and synthetic acids show that as low as 5% synthetic acid in a natural vinegar can be detected in a comparative analysis. A sensitivity level of 15% may be expected on an absolute basis when no information on the origin of the precursors is available, providing that a determination of the botanical family of the natural component can be carried out beforehand.     

Analytical strategies to confirm Scotch whisky authenticity. Part II: Mobile brand authentication

Whilst the authentication of Scotch whisky brands using laboratory based gas chromatography is well established, there is a need for authentication methods for use under field test conditions. The UV/visible absorbance spectra of specific brands of Scotch whisky were found to produce consistent absorbance ranges which allowed the development of a faster, cheaper and more mobile test method. Test samples with spectra outside the acceptable ranges for genuine reference samples were therefore deemed suspect, enabling their authenticity to be later confirmed in the laboratory by GC. This novel application allowed brand authenticity analyses to be undertaken at remote sites where gas chromatography was unavailable and has also allowed the introduction of field testing using a small portable hand held spectrophotometer.     

梨醋半成品的超滤处理

用截留分子量不同的中空纤维超滤膜组件对梨醋半成品进行了处理.结果表明,使用截留分子量为1万的中空纤维超滤膜组件,在0.1 MPa压力差和室温下,将梨醋半成品超滤5 h,透过通量基本恒定在6 L/(m2.h).梨醋经过超滤,酸度保留率可达97.4%,糖度保留率88.3%,且风味不变,澄清透明,放置13个月无沉淀物.     

Determination of 5-hydroxymethylfurfural after Winkler and by the HPLC method for authentication of honey

The quality and authenticity of commercially available honey from Slovak market and the development of HPLC method for determination of hydroxymethylfurfural (HMF) content of honey with fine separation efficiency, sensitivity, applicability, and recovery was evaluated. Physicochemical parameters (moisture, total acidity, content of proline, saccharides, and value of electrical conductivity) have been determined.     

Analytical excited state forces for the time-dependent density-functional tight-binding method

An analytical formulation for the geometrical derivatives of excitation energies within the time-dependent density-functional tight-binding (TD-DFTB) method is presented. The derivation is based on the auxiliary functional approach proposed in [Furche and Ahlrichs, J Chem Phys 2002, 117, 7433]. To validate the quality of the potential energy surfaces provided by the method, adiabatic excitation energies, excited state geometries, and harmonic vibrational frequencies were calculated for a test set of molecules in excited states of different symmetry and multiplicity. According to the results, the TD-DFTB scheme surpasses the performance of configuration interaction singles and the random phase approximation but has a lower quality than ab initio time-dependent density-functional theory. As a consequence of the special form of the approximations made in TD-DFTB, the scaling exponent of the method can be reduced to three, similar to the ground state. The low scaling prefactor and the satisfactory accuracy of the method makes TD-DFTB especially suitable for molecular dynamics simulations of dozens of atoms as well as for the computation of luminescence spectra of systems containing hundreds of atoms.     

Analytical method for determination of dinitropyrenes using gas chromatography-high-resolution mass spectrometry

A gas chromatography-high-resolution mass spectrometry method has been developed for the determination of dinitropyrenes (DNPs). DNPs were reduced to the corresponding diaminopyrenes with sodium hydrosulfide, and the reduced DNPs were derivatized with N-methyl-bis(trifluoroacetamide). The sensitivity of this method was up to 10 times that of high-performance liquid chromatography with fluorescence detection. The detection limits for 1,3-, 1,6-, and 1,8-DNPs were in the 0.90-1.1 pg range. The concentrations were corrected with a correction factor determined from the recovery of an internal standard. The recovery of deuterium-labeled 6-nitrochrysene was at least 87%. This new method was utilized for quantitative determination of DNPs in Standard Reference Material (SRM) 1975 available from the US National Institute of Standards and Technology. Three DNP isomers were measured in SRM 1975 at 0.571-1.59 microg/g.     

Analytical method for atmospheric tritium with a portable tritium sampling system

A portable tritium sampler was developed for the stepwise collections of water vapour (HTO), hydrogen (HT) and hydrocarbons (CH₃T) in the atmosphere. First, water vapour was collected in an electronic cooler and an HTO collection column containing 400 g of molecular sieve. Next, dried air was introduced into an HT collection column containing 150 g of palladium catalyst. Hydrogen was then converted to water by catalytic oxidation at room temperature and the resultant water was immediately adsorbed on the molecular sieve bed supporting the catalyst. The remaining gas was finally introduced into a CH₃T collection column containing 100 g of molecular sieve through a platinum catalyst column, in which hydrocarbons were burnt at 400°C. The resultant water was adsorbed in the CH₃T collection column. The collection efficiencies of water in the HTO, HT and CH₃T collection columns were all estimated to be nearly 100%. This newly developed method was found to be useful for the routine tritium monitoring by applying it to actual air samples.     

A flow-injection mass spectrometry fingerprinting method for authentication and quality assessment of Scutellaria lateriflora-based dietary supplements

Scutellaria lateriflora, commonly known as skullcap, is used as an ingredient in numerous herbal products. However, it has been occasionally adulterated/contaminated with Teucrium canadense and/or Teucrium chamaedrys, commonly known as germander, due to the morphological similarities between the two genera. The latter contains hepatotoxic diterpenes. Despite the potential hepatotoxicity introduced by germander contamination, analytical methodologies for the authentication and quality assessment of S. lateriflora-based dietary supplements have not been reported. In this study, a flow-injection/mass spectrometry fingerprinting method in combination with principal component analysis was used to survey S. lateriflora-based dietary supplements sold in the USA.     

Analytical second-order geometrical derivatives of energy for the self-consistent-charge density-functional tight-binding method

Analytical formulation of the second-order geometrical derivatives of energy for the self-consistent-charge density-functional tight-binding (SCC-DFTB) method is presented. To test its quality and numerical performance, the derived formalism has been coded and applied for calculation of harmonic vibrational frequencies for a set of 17 small and medium size molecules. For this set, the average absolute deviation from experiment is 99 cm(-1) for SCC-DFTB vs 62 cm(-1) for the M?ller-Plesset second-order perturbation theory with the cc-pVDZ basis set (MP2/cc-pVDZ) and 32 cm(-1) for the B3LYP density functional method with the same basis set (B3LYP/cc-pVDZ), while the maximal deviation is 465 cm(-1) vs 1,741 cm(-1) for MP2/cc-pVDZ and 112 cm(-1) for B3LYP/cc-pVDZ. The SCC-DFTB results are in reasonable agreement with experiments as well as with ab initio and density-functional results, and are better than other semiempirical methods. The SCC-DFTB method allows for considerable computational time saving when compared to other methods while retaining similar overall accuracy. Data for a series of conjugated polyenes show that an analytical formulation of SCC-DFTB is noticeably faster than its numerical formulation.     

Analytical QbD-based systematic bioanalytical HPLC method development for estimation of quercetin dihydrate

The current work entails development of rapid, sensitive, and inexpensive high-performance liquid chromatographic method of quercetin dihydrate using the quality by design approach. Quality target method profile was defined and critical analytical attributes (CAAs) were earmarked. Chromatographic separation was accomplished on a C₁₈ column using acetonitrile and ammonium acetate buffer (35:65) %v/v (containing 0.1% acetic acid, pH 3.5) as mobile phase at 0.7?mL/min flow rate with UV detector at 237?nm. Screening studies using fractional factorial design revealed that organic modifier, injection volume, column temperature, and buffer strength have significant influence on method CAAs, namely, peak area, retention time, and peak tailing. The critical method parameters were systematically optimized using Box–Behnken design. Response surface mapping was used along with numerical optimization and desirability function for identifying the optimal chromatographic conditions. Linearity was observed in the drug concentration ranging between 2 and 50?µg/mL. Accuracy analysis revealed mean % recovery between 93.6 and 96.2%, while precision study revealed mean % recovery between 93.7 and 96.5%. Limits of detection and quantification of the developed method were found to be 12.1 and 36.6?ng/mL. Overall, the studies construed successful development of chromatographic method of quercetin with enhanced method performance.     

Analytical method for determining colour intensities based on Cherenkov radiation colour Quenching

In the present work a study was made for determining colour intensities using as luminous non-monochromatic source the Cherenkov emission produced in the walls of a glass capillary which acts as luminous source itself inside of a coloured solution to be evaluated. The reproducibility of this method has been compared with the spectrophotometric assay; the relative errors of both analytical methods have been calculated for different concentrations of congo red solution in the range of minimal error, according to Ringbom's criterion. The sensitivity of this analytical method has been studied for the two β-emitters employed:⁹⁰Sr/⁹⁰Y and²⁰⁴Tl.     

Analytical Quality by Design (AQbD)-oriented RP-UFLC method for quantification of lansoprazole with superior method robustness

A reversed-phase ultrafast liquid chromatography method was developed for quantification of lansoprazole in pharmaceutical dosage form using analytical quality by design approach. Systematic planning and experimentation using design of experiment approach were used for method development and optimization studies. A central composite design was used for optimizing the chromatography, by choosing organic phase proportion and flow rate as the critical method variables for evaluating their effect on critical analytical attributes like resolution, plate number, and tailing factor. The optimal chromatography was accomplished on a C-18 column (250?×?4.6?mm, 5?µm) using methanol:water (70:30, v/v) as mobile phase at a flow rate of 1.0?mL/min. Photo diode array (PDA) detection was performed at 284?nm. Caffeine was used as the internal standard. Method validation studies revealed that the calibration curve was linear over 1.0–300?µg/mL. The method was found accurate with average recovery between 98.99 and 102.87%. The percent relative standard deviation values obtained for precision were as per ICH guideline and within the acceptance limits (<2%). Results of system suitability indicated superior method robustness. In a nutshell, the method was found to be highly suitable for its applicability in the determination of lansoprazole in bulk and tablet dosage form.     

Application of capillary isotachophoresis for fruit juice authentication

A method using capillary isotachophoresis (ITP) was developed and applied for the determination of the anionic profile of orange juices with the aim to obtain some useful information on the authenticity or adulteration of imported and native beverage products. An EA 100 electrophoretic analyser (Villa-LABECO, Slovak Republic) was used for capillary isotachophoretic determination of anions in tested samples. More systems of leading and terminating electrolytes were used. Detection conductivity and UV detection at 254 nm were used. Sample injection volume was 30 microl. These systems allow one to determinate inorganic anions, organic acids and some additives--adulterants in anionic forms in orange juices. By capillary isotachophoretic determination the lengths or areas of characteristic zones were established and compared to authentic orange juices of different species and origin and with RSK reference values (Code of Practice). Special emphasis was placed on D-isocitric acid ITP determination as a reliable fruit juice authentication marker. The presented multicomponent analysis of orange juice authenticity according to ITP anionic profiles obtained by capillary isotachophoresis presents an alternative information source necessary for deciding about authenticity of the products.     

Trace element ink spiking for signature authentication

Signature authentication is a critical question in forensic document examination. Last years the evolution of personal computers made signature copying a quite easy task, so the development of new ways for signature authentication is crucial. In the present work a commercial ink was spiked with many trace elements in various concentrations. Inorganic and organometallic ink soluble compounds were used as spiking agents, whilst ink retained its initial properties. The spiked inks were used for paper writing and the documents were analyzed by a non destructive method, the energy dispersive X-ray fluorescence. The thin target model was proved right for quantitative analysis and a very good linear relationship of the intensity (X-ray signal) against concentration was estimated for all used elements. Intensity ratios between different elements in the same ink gave very stable results, independent on the writing alterations. The impact of time both to written document and prepared inks was also investigated.     

Analytical application of the urease method for determination of urea in the presence of biuret

Biuret does not interfere in the urease-catalysed hydrolysis of urea.     

Analytical Method Performance Evaluation (AMPE)--a software tool for analytical method validation

A Windows-based software tool [Analytical Method Performance Evaluation (AMPE)] was developed to support the validation of analytical methods. The software implements standard statistical approaches commonly adopted in validation studies to estimate analytical method performance (limits of detection and quantitation, accuracy, specificity, working range, and linearity of responses) according to ISO 5725. In addition, AMPE proposes the application of innovative and unique approaches for the assessment of analytical method performance. Specifically, AMPE proposes the use of difference-based indexes to quantify the agreement between measurements and reference values, the use of pattern indexes to quantify methods bias with respect to specific external variables, and the application of fuzzy logic to aggregate into synthetic indicators the information collected independently via the different performance statistics traditionally estimated in validation studies. Aggregated measures are particularly useful for methods comparison, when more than one method is available for a specific analysis and it may be of interest to identify the best performing one taking into account, simultaneously, the information available from different performance statistics. Illustrative examples of the type of outputs expected from AMPE-based validation sessions are given. The extensive data handling capabilities and the wide range of statistics supplied in the software package makes AMPE suitable for specific needs that may arise in different validation studies. The installation package, complete with a fully documented help file, is distributed free of charge to interested users along with input files exemplary of the type of entry data required to run validation data analyses.