Non-destructive Sample Preparation Research Articles

Progress of sample preparation and analytical methods of dried fruit foods

坚果、果脯等干果类食品含有丰富的营养成分,深受国内外广大消费者的喜爱。但这些食品在果实生产、加工、储运时会使用农药或产生霉变等,造成干果中农药、重金属、霉菌毒素或添加剂等有害成分残留,甚至超过国家限量要求,带来严重的食品安全问题。因此,加强干果类食品的质量监督具有重要的经济和社会意义。但干果类食品基质复杂,有害物质种类多,结构和性质差异大,含量低,其分析检测需要快速高效的样品前处理技术和准确灵敏的分析检测方法。该文主要综述了近十年来干果类食品中有害物质的样品前处理及分析检测方法研究进展。其中样品前处理方法主要包括各种场辅助萃取法、相分离法和衍生化萃取方法等。场辅助萃取法主要是借助超声波和微波场等外场(协同)作用加快干果中有害物质的溶出速度,提高其萃取效率。相分离法,包括固相(微)萃取、分散固相萃取和液相(微)萃取法等,具有溶剂消耗少、分离富集效率高的优势,是干果样品分析中较常使用的前处理方法。该文还重点介绍了干果中各类有害成分分析检测技术,主要包括色谱、原子光谱、无机质谱、电化学分析等常规实验室方法,以及一些适用于现场分析的快速检测技术,并以此为基础,展望了干果类食品中有害物质分析检测技术的发展趋势。

NMR in the Service of Wine Differentiation.

NMR is a swift and highly reproducible spectrometric technique that makes it possible to obtain spectra containing a lot of information about the sample analyzed. This approach helps major components be described in complex mixtures such as wine in just one analysis. Analysis of wine metabolites is very often used to understand the impact of geographical origin or variety on wine quality. NMR is often used for tracing the geographical origin of wine. Research on NMR metabolic effects of geographical origin is of great importance as the high added value of wines results from compliance with state legislation on the protected denomination of origin (PDO) and protected geographical indication (PGI) for the administration of the appellation of wines. A review of NMR with emphasis on SNIF-NMR in the analysis of wine authenticity is given. SNIF-NMR remains a method of choice for the detection of wine chaptalization as it is the only approach which provides position-specific information on the origin of sugar in wine. However, the sample preparation step, which lacks major improvements since its conception, is strenuous and expensive, and suffers from drawbacks in terms of low sample throughput. Mainstream 1D and 2D NMR experiments provide a fast and affordable way to authenticate wine based on the geographical origin, vintage, and variety discrimination, and include a simple and non-destructive sample preparation step. With this approach, spectral data processing often represents a crucial step of the analysis. With properly performed NMR experiments good to excellent differentiation of wines from different vintages, regions, and varieties was achieved recently.

Three-dimensional characterization of first instar horse and rhinoceros stomach bot fly larvae (Oestridae: Gasterophilinae:Gasterophilus,Gyrostigma): novel morphology and evolutionary implications

AbstractLarval characters are of importance in systematic and evolutionary studies of Diptera but lag behind characters of adults due to difficulties in obtaining relevant information. Larvae of stomach bot flies are obligate parasites completing development exclusively in the alimentary tract of equids and rhinoceroses. They possess diversified morphological adaptations, providing remarkable examples to further our understanding of larval evolution. Herein, three-dimensional structures of first instar Gasterophilus pecorum and Gyrostigma rhinocerontis are compared using confocal laser scanning microscopy (CLSM) and scanning electron microscopy (SEM). We suggest CLSM has a large potential for exploiting cryptic character systems of micro fly larvae, as spectral range and intensity of autofluorescence emitted by sclerotized structures and soft tissues are distinct, presenting a high-contrast mechanism for multistructural visualization with non-destructive sample preparation. Five new potential synapomorphies are proposed to corroborate the sister-group Gasterophilus and Gyrostigma. The upward curving mouth-hooks of first instar Gasterophilus and Gyrostigma are distinctive in Cyclorrhapha and possibly serve to facilitate the larval subcutaneous migration within the host. Three types of mouthhooks are recognized in first instar Oestridae, with the gently curved and gradually tapered type optimized as the ancestral state, from which the gasterophiline and hypodermatine types evolved independently.

A rapid method for screening and determination test of methanol content in ethanol-based products using portable Raman spectroscopy

Raman spectroscopy is nondestructive sample preparation and suitable for use in quality control-related field inspections, particularly on ethanol-based products. The influence of laser power density (PD) and exposure time (ET) on the Raman spectra similarity, specificity, selectivity, and accurate measurements for screening and determination of methanol content were carried out in this study.Raman spectra of samples were measured using a Raman handheld instrument. Measuring scales of PD and ET were varied from 50 to 300 milliWatt (mW) and 1000–5000 ms (ms), respectively. The similarity of Raman-spectra of those samples was statistically analysed with the help of hierarchical cluster analysis (HCA) and cross-correlation function (Ccorrel). The subtracted Raman spectra and pure ethanol spectra were implemented to identify methanol content in samples of ethanol-based products specifically.The Raman spectra measured at PD of 200–300 mW and clustered in one group by ward linkage method showed a similarity level of 99.98%. The variation of ET between 1000 and 5000 ms on fix PD of 300 mW showed high precision (RSD <2%) with more than 99% similarity of Raman spectra. Rinsing of PD was found to increase the signal: noise ratio, while prolonged exposure time reduced the signal: noise ratio. The precision and accuracy measurements were obtained by setting the PD and ET values of 300 mW and 4000 ms, respectively. The subtracted Raman spectra with the spectra of absolute ethanol introduced a simultaneous screening of methanol containing alcohols and determination of both substances.

Quantification of collagen fiber structure using second harmonic generation imaging and two-dimensional discrete Fourier transform analysis: Application to the human optic nerve head.

Second harmonic generation (SHG) microscopy is widely used to image collagen fiber microarchitecture due to its high spatial resolution, optical sectioning capabilities and relatively nondestructive sample preparation. Quantification of SHG images requires sensitive methods to capture fiber alignment. This article presents a two-dimensional discrete Fourier transform (DFT)-based method for collagen fiber structure analysis from SHG images. The method includes integrated periodicity plus smooth image decomposition for correction of DFT edge discontinuity artefact, avoiding the loss of peripheral image data encountered with more commonly used windowing methods. Outputted parameters are as follows: the collagen fiber orientation distribution, aligned collagen content and the degree of collagen fiber dispersion along the principal orientation. We demonstrate its application to determine collagen microstructure in the human optic nerve head, showing its capability to accurately capture characteristic structural features including radial fiber alignment in the innermost layers of the bounding sclera and a circumferential collagen ring in the mid-stromal tissue. Higher spatial resolution rendering of individual lamina cribrosa beams within the nerve head is also demonstrated. Validation of the method is provided in the form of correlative results from wide-angle X-ray scattering and application of the presented method to other fibrous tissues.

Characterization of Kimchi Flavor with Preconcentration by Head Space Solid-Phase Microextraction and Stir Bar Sorptive Extraction and Analysis by Gas Chromatography-Mass Spectrometry

Kimchi is a traditional fermented vegetable, known for its complex flavor. Herein, we compared compounds related to the kimchi flavor, identified by gas chromatography-mass spectrometry (GC-MS) with the developed solid phase microextraction (SPME) and stir bar sorptive extraction (SBSE) techniques. Although headspace-solid phase microextraction (HS-SPME) detected more volatile compounds than nondestructive-headspace-solid-phase microextraction (ND-HS-SPME), those identified by ND-HS-SPME were considered closely related to the flavor of the intact kimchi. Furthermore, direct immersion-stir bar sorptive extraction (DI-SBSE) detected more volatile and nonvolatile compounds than headspace-stir bar sorptive extraction (HS-SBSE), while more sulfur compounds were identified by HS-SBSE. Therefore, we recommend the use of the HS-SPME method using a divinylbenzene/carboxen/polydimethylsiloxane fiber for identifying compounds related to the kimchi flavor. In addition, principal component analysis showed ND-HS-SPME and HS-SBSE to be closely clustered. Overall, we estimated that the samples obtained via the nondestructive sample preparation emits fewer polar volatile flavor compounds than those obtained using the destructive sample preparation. Considering the findings presented herein, we believe that this study contributes to optimizing the flavor analysis of kimchi and other fermented vegetables.

Evaluation of geochemical data by two different XRF spectrometers in sediments from the Santiaguillo Basin (state of Durango, Mexico)

XRF spectrometry is one of the commonly used methods to measure geochemical data and it involves both destructive and non-destructive sample preparation techniques. We evaluated data quality of 12 different regularly used elements in sedimentary research by calculating precision and accuracy of data generated in a portable ED-XRF (Niton FXL 950) and by applying a non-destructive sample preparation method. Different measuring modes of the spectrometer and matrix of the samples did not significantly influence the precision but influenced the accuracy. In sediments of variable matrix collected from the Santiaguillo Basin (state of Durango, Mexico), concentrations of Si, Ti, Al, Fe, Mn, Ca, K, Sr and Zr measured using the portable ED-XRF showed strong and positive correlations (r?0.8) with concentrations obtained using a conventional WD-XRF. The matrix-effect possibly caused lower correlations (r?0.7) for Mg, P and Rb. Concentrations of elements with stronger correlations were corrected using the linear regression equations generated after comparing results of both spectrometers.

Analysis of Structural Variability in Pharmaceutical Excipients Using Solid-State NMR Spectroscopy

Polysaccharide-based excipients comprise the majority of most solid dosage forms and can vary dramatically in terms of structural and functionally related properties. Analytical methods for characterizing these important formulation components are crucial. Solid-state NMR spectroscopy (SSNMR) can provide a wealth of information on these materials while offering the advantages of non-destructive sample preparation and selectivity. The overall objective of this work is to identify SSNMR parameters that can be used to detect differences among these excipients. Excipients were obtained from a wide range of suppliers and analyzed as received; (13)C SSNMR spectra were acquired using a Chemagnetics CMX-300 spectrometer operating at approximately 75 MHz. The resolution of SSNMR signals of many excipients allows for positive identification of the major form present. Alginic acid and sodium alginate can be differentiated based on carbonyl peak position. Analysis of relative peak intensities provides insight into the purity of a carrageenan sample compared to known standards. The SSNMR spectrum of starch can be used to identify the source and to quantitate the amorphous and crystalline content. Relaxation values and peak areas of starch derivatives can be related to the degree of hydrolysis, providing an alternative method for determining dextrose equivalent. Differences in peak intensities and relaxation time values of HPMC samples can be correlated to the amount of methoxy subsituent groups. Important characteristics of excipients such as form identification, structural differences, crystalline and amorphous content, and water content variations can be detected using SSNMR spectroscopy.

Culture-independent quantification of Salmonella enterica in carcass gauze swabs by flotation prior to real-time PCR

To facilitate quantitative risk assessment in the meat production chain, there is a need for culture-independent quantification methods. The aim of this study was to evaluate the use of flotation, a non-destructive sample preparation method based on traditional buoyant density centrifugation, for culture-independent quantification of intact Salmonella in pig carcass gauze swabs (100 cm 2) prior to quantitative PCR (qPCR). A novel approach was investigated, excluding the homogenization step prior to flotation, to improve the detection limit and speed up the quantification procedure. The buoyant density of two Salmonella strains in different growth conditions was determined to be 1.065–1.092 g/ml. Based on these data, an optimal discontinuous flotation with three different density layers, ~ 1.200, 1.102 and 1.055 g/ml, was designed for extracting intact Salmonella cells from pig carcass swabs. The method allowed accurate quantification from 4.4 × 10 2 to at least 2.2 × 10 7 CFU Salmonella per swab sample using qPCR (without preceding DNA extraction) or selective plating on xylose lysine deoxycholate agar. Samples with 50 CFU could be detected occasionally but fell outside the linear range of the standard curve. The swab samples showed a broad biological diversity; for seven samples not inoculated with Salmonella, the microbial background flora (BGF) was determined to 5.0 ± 2.2 log CFU/ml sample withdrawn after flotation. It was determined that the proceeding PCR step was inhibited by BGF concentrations of ≥6.1 × 10 8 CFU/swab sample, but not by concentrations ≤6.1 × 10 6 CFU/swab sample. By using the gauze swabs directly in the flotation procedure, the homogenization step normally used for preparation of food-related samples could be excluded, which simplified the culture-independent quantification method considerably.

AFM for diagnosis of nanocrystallization of steels in hardening processes

The aim of this study is to investigate the nanocrystallization of steels caused by the transformation from the austenitic to the martensitic phase induced by a severe plastic deformation (SPD) treatment. In this framework, we applied an air blast shot peening treatment, which is a simple protocol widely used for industrial purposes. AISI 286 and AISI 316 specimens were peened for different times and polished using diamond pastes in order to remove corrugations higher than 1 mum. The characterization of the steel surfaces was performed by atomic force microscopy (AFM) operating in contact mode. Additional EDXD measurements were performed to confirm the phase transition. An AFM-based characterization at nanometric level of the steel surfaces is provided. When the peening exceeds a threshold time that, as expected, depends on the steel composition, a uniform nanostructuration is detected. It is well known that such rearrangement is associated to the growth of a martensitic phase. To date, AFM has been employed in this field only for few applications and to solve specific problems. On the other hand, our results demonstrate that this is a useful technique for the characterization of hardened surfaces, especially when non-destructive sample preparation treatments are required. Moreover, we show that AFM can be a useful tool also for in situ industrial diagnostics of metallic parts.

Diffuse reflectance fourier transform infrared studies of the reinforcement/coupling agent interface of composites

Diffuse-reflectance FTIR spectroscopy is a powerful technique to study the surfaces of solids by nondestructive sample preparation. Its potential is here demonstrated with reference to the characterization of glass powder coated with increasing amounts of a silane coupling agent.

Precision measurement of Fe concentration in dolomites using radioisotope X-ray fluorescence

A series of dolomite bore hole samples have been analyzed for their iron content using radioisotope X-ray fluorescence. A precision of ±0.1%, as specified for oil and gas exploration, has been met using a non-destructive sample preparation technique, energy dispersive detector,109Cd source and a micro-computer based data acquisition and reduction system. Sample and standard preparation procedures are discussed.

Further Developments in the Methodology of Surface Analysis by FT-IR: Quantitative Aspects of Diffuse Reflectance Methods

The quantitative aspects of diffuse reflectance FT-IR are explored for standard E-glass/AAPS ( N-2-aminoethyl-3-aminopropyltrimethoxysilane) treated samples. Nondestructive sample preparation procedures are used. One generates calibration curves by plotting the normalized integrated intensity of the coupling agent bands in the 2990–2800 and 1700–1500 cm−1 regions vs. the concentration of the treatment solution. The data are derived by DRIFT spectroscopy, and the above results are plotted for the overlayer technique as well as for no overlayer. The scatter in the quantitative data due to fiber orientation effects has been measured and is found to be significant (20–30%). However, averaging over several orientations of the fibers results in a linear dependence of the integrated intensities of the coupling agent bands on solution concentration. The well-known breakpoint that has been observed for other coupling agent systems does not appear in the curve derived from the averaged spectra. The above-mentioned scatter is eliminated by the use of KBr overlayers on the samples. Linear calibration curves relating band intensity to concentration can be constructed. When the overlayer procedure is used, breakpoints do occur in the calibration curves. The position of these breakpoints agrees well with observations for the similar coupling agent γ-APS.

Fourier Transform Diffuse Reflectance Infrared Study of Polymer Films and Coatings: A Method for Studying Polymer Surfaces

Diffuse reflectance FT-IR (DRIFT) is described as a tool for the study of polymer surfaces. The high sensitivity (particularly to surfaces) and nondestructive sample preparation procedure used for DRIFT experiments are valuable characteristics of the technique. By the use of an overlayer of a nonabsorbing powder such as KBr, the quality of the spectra of coatings and surface species on absorbing substrates is improved. We performed a model study using multilayer polymer films in order to understand the optimal applicability of DRIFT to these measurements. The relative contribution of the surface to the spectra can be adjusted by varying the amount and/or particle size of the KBr powder overlayer. Correlations between particle size, overlayer amount, and nature of the spectra of the “model” system are discussed. Practical examples of the application of this novel approach are presented.