Quantitative Analysis of Heavy Metals in Water Based on LIBS with an Automatic Device for Sample Preparation

Abstract Heavy metals in water can be deposited on graphite flakes, which can be used as an enrichment method for laser-induced breakdown spectroscopy （LIBS） and is studied in this paper. The graphite samples were prepared with an automatic device, which was composed of a loading and unloading module, a quantitatively adding solution module, a rapid heating and drying module and a precise rotating module. The experimental results showed that the sample preparation methods had no significant effect on sample distribution and the LIBS signal accumulated in 20 pulses was stable and repeatable. With an increasing amount of the sample solution on the graphite flake, the peak intensity at Cu I 324.75 nm accorded with the exponential function with a correlation coefficient of 0.9963 and the background intensity remained unchanged. The limit of detection （LOD） was calculated through linear fitting of the peak intensity versus the concentration. The LOD decreased rapidly with an increasing amount of sample solution until the amount exceeded 20 mL and the correlation coefficient of exponential function fitting was 0.991. The LOD of Pb, Ni, Cd, Cr and Zn after evaporating different amounts of sample solution on the graphite flakes was measured and the variation tendency of their LOD with sample solution amounts was similar to the tendency for Cu. The experimental data and conclusions could provide a reference for automatic sample preparation and heavy metal in situ detection.

Sample Preparation for Monolithic Refractories Part 1:Refractory Castables

1 Scope This standard specifies the definition and test methods of flowability of dense and insulating refractory castables, and moulding equipment, moulding methods, curing and drying conditions of castables samples.

Prediction to the Efficiency of Soft Clay Sample Preparation with Vacuum Loading

Vacuum loading has been examined as a way of preparing uniformly consolidated soft clay samples. The facility and loading procedure are described in this paper. An analytical solution to the three dimensional consolidation equation is derived for estimating the degree of consolidation of the soil sample with vacuum loading. The given example shows that the predicted degree of consolidation of a soft clay bulk with vacuum loading is close to that measured in the consolidation process.

Sample preparation for the analysis of membrane proteomes by mass spectrometry

The low abundance and highly hydrophobic nature of most membrane proteins make their analysis more difficult than that for common soluble proteins.Successful membrane protein identification is largely dependent on the sample preparation including the enrichment and dissolution of the membrane proteins.A series of conventional and newly developed methods has been applied to the enrichment of low-abundance membrane proteins at membrane and/or protein levels and to the dissolution of hydrophobic membrane proteins.However,all the existing methods have inherent advantages and limitations.Up to now,there has been no unique method that can universally be employed to solve all the problems and more efforts are needed in improving sample preparation for the analysis of membrane proteomes.

Applied Study on Magnetic Nanometer Beads in Preparation of Genechip Samples

A protocol for enrichment and adsorption of karyocyte from whole blood by using magnetic nanometer beads as solid phase absorbents was presented. The PCR amplification could be accomplished by using the nanobeads with karyocyte as template directly and the PCR products were applied on an oligonucleotide array to do gene typing. The HLA A PCR amplification system and a small HLA A oligonucleotide microarray were applied as the platform and an experiment protocol of separating karyocyte from whole blood using the magnetic nanometer beads (Fe 2O 3) were set up. The experimental conditions were also discussed. It showed that pH level of PBS eluent, Taq enzyme quantity and fragment length of products could influent the amplification results, and the magnetic nano beads could succeed in sample preparation in microarray to provide a promising way in automatic detection and lab on a chip.

Review on analytical technologies and applications in metabolomics

Over the past decade,the swift advancement of metabolomics can be credited to significant progress in technologies such as mass spectrometry,nuclear magnetic resonance,and multivariate statistics.Currently,metabolomics garners widespread application across diverse fields including drug research and development,early disease detection,toxicology,food and nutrition science,biology,prescription,and chinmedomics,among others.Metabolomics serves as an effective characterization technique,offering insights into physiological process alterations in vivo.These changes may result from various exogenous factors like environmental conditions,stress,medications,as well as endogenous elements including genetic and protein-based influences.The potential scientific outcomes gleaned from these insights have catalyzed the formulation of innovative methods,poised to further broaden the scope of this domain.Today,metabolomics has evolved into a valuable and widely accepted instrument in the life sciences.However,comprehensive reviews focusing on the sample preparation and analytical methodologies employed in metabolomics within the life sciences are surprisingly scant.This review aims to fill that gap,providing an overview of current trends and recent advancements in metabolomics.Particular emphasis is placed on sample preparation,sophisticated analytical techniques,and their applications in life science research.

Analytical quality-by-design approach for sample treatment of BSA-containing solutions

The sample preparation of samples conlaining bovine serum albumin（BSA）,e.g..as used in transdermal Franz diffusion cell（FDC） solutions,was evaluated using an analytical qualily-by-design（QbD）approach.Traditional precipitation of BSA by adding an equal volume of organic solvent,often successfully used with conventional HPLC-PDA,was found insufficiently robust when novel fused-core HPLC and/or UPLC-MS methods were used.In this study,three factors（acetonitrile（%）.formic acid（%） and boiling time（min）） were included in the experimental design to determine an optimal and more suitable sample treatment of BSAcontaining FDC solutions.Using a QbD and Derringer desirability（D） approach,combining BSA loss,dilution factor and variability,we constructed an optimal working space with the edge of failure defined as D〈0.9.The design space is modelled and is confirmed to have an ACN range of 83 ± 3% and FA content of 1 ±0.25%.

Distribution and Accumulation of Major and Trace Elements in Gypsum Samples from Lignite Combustion Power Plant

Flue gas containing volatile elements, fine fly ash particulates not retained by particle control devices, and limestone are the most important sources of trace and major elements (TMEs) in wet flue gas desulphurization (WFGD) gypsum. In this study, samples of gypsum slurry were separated into fine and coarse fractions. Multi-elemental analysis of 45 elements in the different size fractions of gypsum, slurry waters and lignite were performed by k0-INAA (k0-instrumental neutron activation analyses). The study found that the volatile elements (Hg, Se and halogens) in the flue gas accumulate in the fine fractions of gypsum. Moreover, the concentrations of most TMEs are considerably higher in the fine fractions compared to the coarse fractions. The exceptions are Ca and Sr that primarily originate from the limestone. Variations of TMEs in the finer fractions are dependent on the presence of CaSO4·2H2O that is the main constituent of the coarse fraction. Consequently, the content of TMEs in the fine fraction is highly dependent on the efficiency of separating the fine fraction from the coarse fraction. Separation of the finer fraction, representing about 10% of the total gypsum, offers the possibility to remove effectively TMEs from WFGD slurry.

Solid-phase microextraction of endogenous metabolites from intact tissue validated using a Biocrates standard reference method kit

Improved analytical methods for the metabolomic profiling of tissue samples are constantly needed.Currently,conventional sample preparation methods often involve tissue biopsy and/or homogenization,which disrupts the endogenous metabolome.In this study,solid-phase microextraction(SPME)fibers were used to monitor changes in endogenous compounds in homogenized and intact ovine lung tissue.Following SPME,a Biocrates AbsoluteIDQ assay was applied to make a downstream targeted metabolomics analysis and confirm the advantages of in vivo SPME metabolomics.The AbsoluteIDQ kit enabled the targeted analysis of over 100 metabolites via solid-liquid extraction and SPME.Statistical analysis revealed significant differences between conventional liquid extractions from homogenized tissue and SPME results for both homogenized and intact tissue samples.In addition,principal component analysis revealed separated clustering among all the three sample groups,indicating changes in the metabolome due to tissue homogenization and the chosen sample preparation method.Furthermore,clear differences in free metabolites were observed when extractions were performed on the intact and homogenized tissue using identical SPME procedures.Specifically,a direct comparison showed that 47 statistically distinct metabolites were detected between the homogenized and intact lung tissue samples(P<0.05)using mixed-mode SPME fibers.These changes were probably due to the disruptive homogenization of the tissue.This study's findings highlight both the importance of sample preparation in tissue-based metabolomics studies and SPME's unique ability to perform minimally invasive extractions without tissue biopsy or homogenization while providing broad metabolite coverage.

Detection and quantification of Pb and Cr in oysters using laser-induced breakdown spectroscopy

The quantitative determination of heavy metals in aquatic products is of great importance for food security issues.Laser-induced breakdown spectroscopy(LIBS)has been used in a variety of foodstuff analysis,but is still limited by its low sensitivity when targeting trace heavy metals.In this work,we compare three sample enrichment methods,namely drying,carbonization,and ashing,for increasing detection sensitivity by LIBS analysis for Pb and Cr in oyster samples.The results demonstrate that carbonization can remove a significant amount of the contributions of organic elements C,H,N and O;meanwhile,the signals of the metallic elements such as Cu,Pb,Sr,Ca,Cr and Mg are enhanced by3–6 times after carbonization,and further enhanced by 5–9 times after ashing.Such enhancement is not only due to the more concentrated metallic elements in the sample compared to the dried ones,but also the unifying of the matter in carbonized and ashed samples from which higher plasma temperature and electron density are observed.This condition favors the detection of trace elements.According to the calibration curves with univariate and multivariate analysis,the ashing method is considered to be the best choice.The limits of detection of the ashing method are 0.52 mg kg-1 for Pb and0.08 mg kg-1 for Cr,which can detect the presence of heavy metals in the oysters exceeding the maximum limits of Pb and Cr required by the Chinese national standard.This method provides a promising application for the heavy metal contamination monitoring in the aquatic product industry.

A Graphene-Based Aerogel Was Prepared as Solid Adsorbent for the Enrichment of Platinum (IV) at Trace Concentration

A three-dimensional graphene-based composite was prepared by a simple one-step in-site reduced-oxide method under atmospheric pressure. The obtained hydrogel was modified with 4-amino-benzenesulfonic acid and connected with ethylenediamine, and freeze-dried into an aerogel, which was characterized. Then the surface interaction with platinum (Pt, IV) was explored. The obtained aerogel showed good adsorption for Pt (IV) at acid conditions, giving a rising to the adsorption rate > 98% while pH ≥ 6. Using hexadecyl trimethyl ammonium bromide of 2% (m/V) as an eluent to desorb the Pt (IV) from the surface of the aerogel, a desorption rate of 81.1% was obtained in this process. Urea, buffer aquation and other surfactants were used in the desorption experiment to understand the adsorption mechanism between the aerogel and Pt (IV). In this work, hydrogen bond, van der Waals force and electronic interaction force mainly drove the adsorption process. For obtaining more purified Pt (IV), we used 0.5% CTAB to desorb Pd (II). A new three-dimensional graphene-based composite was prepared and the surface interaction between Pt (IV) and composite was experimented for understanding the adsorption mechanism and exploring its potential application in sample preparation in low concentration.

气相色谱-质谱分析气体样品的制备方法和技术

现代GC-MS仪器虽然具有较高的分辨能力和较高的灵敏度,但是对欲分析样品的要求也比较严格.诸如:进样量大小、组成组分的浓度范围、样品的物理状况、样品中的基体干扰等问题都是必须在进样之前调查清楚,才能选择正确的样品处理方法和技术并处理成GC-MS仪器能够直接进样测定的样品形式,获得正确的GC-MS分析测定结果.……

GC-MS测定中的小体积样品浓缩技术

New preparation methods for the GC-MS analytical sample are reviewed in this paper.There are MT,SH-MT,PMT,ME-MT,MCT,and so on mainly.

Survey Techniques of Grassland Plant Resources

Based on years of practice and survey methods of grassland resources at home and abroad, the technical problems that may occur in the survey process are analyzed, the preparatory work before survey, specific content of field survey and sample processing and analysis and specimen preparation are elaborated. Moreover, the announcements of major technical methods are also described in details.

Mechanisms of antimicrobial peptides as characterized by solid-state NMR

Antimicrobial peptides(AMP)are small proteins that play critical roles in host defense against microbe invasion.Many AMPs disrupt the cellular membrane of microbe,while the mechanism of action of AMPs can be very sophisticated.Solid-state NMR(SSNMR)technique is powerful in characterizing the mechanism of AMPs in vivo and in vitro.This review summarizes the recent advance of SSNMR technique in AMP mechanisms characterization.We highlight the sample preparation approaches,the SSNMR spectroscopic methods,and a number of outstanding examples of AMP mechanisms elucidated via SSNMR spectroscopy.

Modifying current thin-film microextraction(TFME)solutions for analyzing prohibited substances:Evaluating new coatings using liquid chromatography

For identifying and quantifying prohibited substances,solid-phase microextraction(SPME)continues to arouse interest as a sample preparation method.However,the practical implementation of this method in routine laboratory testing is currently hindered by the limited number of coatings compatible with the ubiquitous high-performance liquid chromatography(HPLC)systems.Only octadecyl(C18)and polydimethylsiloxane/divinylbenzene ligands are currently marketed for this purpose.To address this situation,the present study evaluated 12 HPLC-compatible coatings,including several chemistries not currently used in this application.The stationary phases of SPME devices in the geometry of thin filmcoated blades were prepared by applying silica particles bonded with various functional ligands(C18,octyl,phenyl-hexyl,3-cyanopropyl,benzenesulfonic acid,and selected combinations of these),as well as unbonded silica,to a metal support.Most of these chemistries have not been previously used as microextraction coatings.The 48 most commonly misused substances were selected to assess the extraction efficacy of each coating,and eight desorption solvent compositions were used to optimize the desorption conditions.All samples were analyzed using an HPLC system coupled with triple quadrupole tandem mass spectrometry.This evaluation enables selection of the best-performing coatings for quantifying prohibited substances and investigates the relationship between extraction efficacy and the physicochemical characteristics of the analytes.Ultimately,using the most suitable coatings is essential for trace-level analysis of chemically diverse prohibited substances.

LC–UV/MS quality analytics of paediatricartemether formulations

A highly selective and stability-indicating HPLC-method, combined with appropriate sample preparation steps, is developed for β-artemether assay and profiling of related impurities, including possible degradants, in a complex powder for oral suspension. Following HPLC conditions allowed the required selectivity： a Prevail organic acid （OA） column （250 mm＆#215;4.6 mm, 5μm）, flow rate set at 1.5 mL/min combined with a linear gradient （where A ？ 25 mM phosphate buffer （pH 2.5）, and B ？ acetonitrile） from 30% to 75% B in a runtime of 60 min. Quantitative UV-detection was performed at 210 nm. Acetonitrile was applied as extraction solvent for sample preparation. Using acetonitrile-water mixtures as extraction solvent, a compartmental behaviour by a non-solving excipient-bound fraction and an artemether-solubilising free fraction of solvent was demonstrated, making a mobile phase based extraction not a good choice. Method validation showed that the developed HPLC-method is considered to be suitable for its intended regulatory stability-quality characterisation of β-artemether paediatric formulations. Furthermore, LC-MS on references as well as on stability samples was performed allowing identity confirmation of the β-artemether related impurities. MS-fragmentation scheme of β-artemether and its related substances is proposed, explaining the m/z values of the in-source fragments obtained.

Lysophosphatidylcholine Biomarkers of Lung Cancer Detected by Ultra-performance Liquid Chromatography Coupled with Quadrupole Time-of-flight Mass Spectrometry

Centrifugal ultrafiltration after methanol extraction of whole plasma was used as an optimal condition for the preparation of blood plasma before metabonomic studies. The plasma samples from 102 lung cancer patients and 34 healthy volunteers were prepared with this approach. With ultra-performance liquid chromatography（UPLC） coupled with quadrupole time-of-flight mass spectrometry（Q-TOF MS） analysis, the samples were investigated in order to find potential disease biomarkers. After data acquisition, orthogonal signal correction partial least squares models were built to differentiate the healthy volunteers from lung cancer patients and to identify metabolites that showed significantly different expression between the two groups. Several metabolite ions were identified as potential biomarkers according to the variable importance in the project（VIP） value in both ion modes. Five lysophosphatidylcholines were further identified as specifically lysoPC 16：0, isomer of lysoPC 16：0, lysoPC 18：0, lysoPC 18：1 and lysoPC 18：2. These results suggest that UPLC coupled with Q-TOF MS is an effective technique for the analysis of plasma metabolites in metabonomic studies.

AN EFFICIENT AND TARGET-ORIENTED SAMPLE ENRICHMENT METHOD FOR PREPARATIVE SEPARATION OF MINOR ALKALOIDS BY PH-ZONE-REFINING COUNTER-CURRENT CHROMATOGRAPHY

A sample enrichment method focusing on the minor targeted components was established to help them to be successfully separated by pH-zone refining CCC.Seven minor indole alkaloids in Uncaria rhynchophylla(Miq.)Miq.ex Havil(UR)were chosen to show the advantage of this method.The sample enrichment and separation were

Responsive switchable deep eutectic solvents:A review

Deep eutectic solvents(DESs)have drawn considerable attention as a new type of green solvent since they were reported.Subsequent studies have shown that DESs have the potential to be used as“designable”solvents,which means that the precursors of DESs with different structures and properties can be screened to customize DESs for specific functions.Researchers have found that during the sample preparation process involving DESs,the specific properties of some“smart”DESs can be switched by directing external driving forces,leading to a reversible phase transition of the target solution.These"smart"DESs are called switchable deep eutectic solvents(SDESs).The advent of SDES simplifies the sample pretreatment steps,reduces the use of organic solvents,and makes solvents easy to recycle,which matches the concept of green and sustainable chemistry.Compared with the number of previous experimental studies,the reviews and summaries on SDESs are rare.Therefore,this review made a summary of the concept and research progress of SDESs based on some related works in the past decade,including composition and type,characterization,switching mechanism,etc.It is expected to provide a certain reference and guidance for the subsequent in-depth research of SDESs in the analytical sample pretreatment.