Biological sample collection and preparation for trace element analysis

Great efforts have been expended on developing analytical procedures for trace element measurements and improving their sensitivity and specificity. Curiously enough, the fact that the results might be affected by sample collection and manipulation was slow to emerge. A substantial body of experimental evidence now suggests that inappropriate sampling may be responsible for inconsistencies between the results of different investigators.     

Method for the collection and analysis of volatile compounds in the breath

A new method is described for the collection and assay of volatile compounds in the breath. Subjects expired into a pump-assisted collecting apparatus in which the breath was drawn through a water trap and then through an adsorptive trap where the volatile compounds were captured on graphitized carbon and molecular sieve. The sample was subsequently eluted from the trap by thermal desorption, concentrated by two-stage cryofocusing, then assayed by gas chromatography with flame ionization and flame photometric detection. Several compounds were regularly observed in the breath of normal human volunteers, including peaks eluting with the same retention times as isoprene, ethanol, acetone, acetaldehyde and carbon disulfide. As a quantitative assay for endogenous isoprene in the breath, the method was sensitive, linear, accurate and reproducible. This method provided a number of advantages: the collection technique was acceptable to volunteers and could be used at sites remote from the laboratory. The automated assay allowed isoprene and several other volatile compounds in the breath to be observed consistently and with improved sensitivity.     

A computer program for the collection,reduction and analysis of echelle spectra

This article is an electronic publication in Spectrochimica Acta Electronica (SAE), the electronic section of Spectrochimica Acta Part B (SAB). The hardcopy text, comprising the main article and an appendix, is accompanied by a disk containing the compiled program, a manual, the source code and tutorial in ASCII format, and data files. The work presented is a result of the need to facilitate collection, calibration, and extraction of data from an echelle spectrometer employing charge coupled array detection (CCD). A computer program, written using Microsoft's BASIC Professional Development System version 7.1 under MS DOS, is explained and demonstrated. Wavelength calibration requires critical spectrometer dimensions, grating counter settings, and the identification of a single spectral line. Calibration accuracies are better than ± 1 pixel across a 576 × 384 pixel array. Extraction of intensity-normalized spectra for all detected orders requires less than 3 min on a 33 MHz 80386 personal computer with an 80387 math coprocessor.     

Influence of operational background emissions on breath analysis using MCC/IMS devices

Multi-Capillary Column coupled to an Ion Mobility Spectrometer (MCC/IMS) is widely used for Breath Analysis. During this analysis a part of room air variations, also operational background emissions have to be considered. In the study reported here we analyze the background emissions of two different intubation methods, an endotracheal tube and a laryngeal mask used in anesthesia. Also a straight connector used to collect the patients breath is studied. Laboratory measurements have been carried out with MCC/IMS and also with a Gas Chromatograph—Mass Selective Detector (GC/MSD), showing different plastic compositions and MCC/IMS chromatographs. Patients breath measurements were carried out while the patients were anesthetized and intubated. In the breath analysis of patients under anesthesia one specific peak of the endotracheal tube has been found, and also two specific peaks from the laryngeal mask. Nonspecific peak due to the straight connector has also been found, showing its suitability for sampling collection.     

Comparison of sample preparation methods for analysis of isoflavones in foodstuffs

Due to the lack of one universally applicable and commonly used reference method, sample preparation in isoflavone (IF) analysis has been performed by many different methods which renders comparison and quality assessment of published IF contents in foodstuffs difficult.In the present work, the impact of different experimental parameters on the IF concentrations determined in soybeans, tofu, soy drink and textured vegetable protein by different extraction and hydrolysis methods was assessed and IF contents obtained by optimized orthogonal methods were compared. Chromatographic analysis was performed by HPLC-UV-ESI-MS. If possible sources of error - which are also pointed out in this work - are avoided, IF contents obtained by extraction, acid-, base- and enzymatic hydrolysis are similar. However, these sample preparation methods differ in the amount of time, standard compounds and instruments required, ruggedness, and in their applicability to analysis of complex composite samples containing soy as minor ingredient. Enzymatic hydrolysis with Helix pomatia juice after extraction by sonication with first 50, then 80% aqueous acetonitrile in the presence of zinc sulfate heptahydrate and after adjustment to ≤10% organic solvent turned out to be the method of choice if only aglucone equivalent contents are required. The advantages of this method are short chromatographic run times, smallest danger of coelution, lowest achievable limits of quantitation and therefore best suitability for work-up of complex composite samples and that only aglucone standards are needed for quantitation.     

Biological sample preparation and data reduction concepts in pharmaceutical analysis

This paper describes strategies to rapidly develop sensitive and selective preparations using manual and robotic liquid-solid isolation (LSI) methods. LSI procedures offer selective isolation of drug or metabolites from complex matrices and are applicable to many pharmaceutical compounds. The beneficial effect of weighted linear regression is described, and several data reduction techniques are contrasted.     

Comparison of protein precipitation methods for sample preparation prior to proteomic analysis

Protein samples should be free of salt and other disturbing agents and have an appropriate concentration to be suitable for two-dimensional (2D) electrophoresis, the principal step of proteomics. To find the most efficient method for sample preparation, we used human plasma and compared four widely applied precipitation methods, using trichloroacetic acid (TCA), acetone, chloroform/methanol and ammonium sulfate, as well as ultrafiltration. Precipitation with TCA and acetone and ultrafiltration resulted in an efficient sample concentration and desalting. We also found that ammonium sulfate fractionation can efficiently remove albumin, which represents more than 50% of plasma proteins.     

食品安全分析样品前处理-快速检测联用方法研究进展

综述了近年来传感器、可视化分析、便携光谱、酶联免疫检测及便携气相色谱等食品安全快速检测技术的研究现状,以及食品安全分析中样品前处理-快速检测联用技术的研究进展,为发展选择性好、准确度高、可定量的新型食品安全快速检测技术提供参考。     

Laser ablation sample transfer for localized LC‐MS/MS proteomic analysis of tissue

We have developed a mid‐infrared laser ablation sampling technique for nano‐flow liquid chromatography coupled with tandem mass spectrometry proteomic profiling of discrete regions from biological samples. Laser ablation performed in transmission geometry was used to transfer material from 50‐µm thick tissue sections mounted on a glass microscope slide to a capturing solvent. Captured samples were processed using filter‐aided sample preparation and enzymatically digested to produce tryptic peptides for data‐dependent analysis with an ion trap mass spectrometer. Comparison with ultraviolet laser capture microdissection from neighboring regions on the same tissue section revealed that infrared laser ablation transfer has higher reproducibility between samples from different consecutive sections. Both techniques allowed for proteomics investigation of different organelles without the addition of surfactants. Copyright © 2016 John Wiley & Sons, Ltd.     

Application of pressurized sample preparation methods for the analysis of steels and copper alloys

Pressurized sample preparation devices (High Pressure Asher, Pressurized Microwave Digestion system, compared with a PTFE decomposition vessel) were used to dissolve certified metal alloy samples (steel, copper) for ICP analysis. Based on the results of the analysis it was established that both up-to-date devices can be advantageously applied to quickly and quantitatively dissolve metal alloy samples. To dissolve the samples, two different kinds of acid mixtures (A: nitric and hydrochloric acid; B: nitric and hydrochloric and sulphuric and phosphoric acid) were used. The sample preparation is simpler and less time-consuming than the earlier commonly used methods, sample loss and degree of contamination are also reduced. Steel samples containing tungsten, titanium and niobium (less than 0.5%) can only be analyzed using a mixture of the four acids. By dissolving steel samples in the nitric and hydrochloric acid mixture, the concentration of their most common elements (Cr, Ni, Mn, V, Cu) as well as their S and P content can be determined. Copper alloy samples can be dissolved quickly by the pressurized microwave decomposition device using hydrochloric acid and diluted (1:1) nitric acid.     

Solid-state gas sensors for breath analysis: A review

The analysis of volatile compounds is an efficient method to appraise information about the chemical composition of liquids and solids. This principle is applied to several practical applications, such as food analysis where many important features (e.g. freshness) can be directly inferred from the analysis of volatile compounds.     

废弃线路板化学分析采样、制样及检测方法

介绍废弃线路板中有回收价值元素和有害物质分析的采样、制样及检测技术。样品经过分类采样、剪切破碎和高温灰化制样,采用样品全分析或副批混合样分析。通过提高称样量、多次测定求平均值的办法,火试金富集-重量法测定贵金属金、银。湿法王水溶解样品,碘量法测定主体元素铜。电感耦合等离子体发射光谱(ICP-AES)法测定其它杂质元素,被测元素质量浓度在0~10μg/mL范围内与光谱强度呈良好线性关系,相关系数均大于0.9998。测定结果的相对标准偏差小于10%(n=5),加标回收率为97.0%~102.5%。该方法简单、快速,有效地解决了线路板样品不均匀而难采样,以及硬度、韧性强制样难,金属易包裹难分解的技术瓶颈,测定结果准确,具有代表性。该方法适用于废弃线路板化学成分分析,其它废弃电子产品检测可参考此方法。     

Evaluation of sample extraction methods for proteomics analysis of green algae Chlorella vulgaris

Many protein extraction methods have been developed for plant proteome analysis but information is limited on the optimal protein extraction method from algae species. This study evaluated four protein extraction methods, i.e. direct lysis buffer method, TCA‐acetone method, phenol method, and phenol/TCA‐acetone method, using green algae Chlorella vulgaris for proteome analysis. The data presented showed that phenol/TCA‐acetone method was superior to the other three tested methods with regards to shotgun proteomics. Proteins identified using shotgun proteomics were validated using sequential window acquisition of all theoretical fragment‐ion spectra (SWATH) technique. Additionally, SWATH provides protein quantitation information from different methods and protein abundance using different protein extraction methods was evaluated. These results highlight the importance of green algae protein extraction method for subsequent MS analysis and identification.     

Large sample activation analysis: Monitoring of photovoltaic module recycling using radioanalytical methods

Photovoltaic modules are the most promising sources of renewable energy. According to respective EU Directives both the glass carrier material and the photo-active layer (CdTe in this study) shall be re-used. Analyses for process surveillance and control have to be carried out, primarily for monitoring of the separation efficiency and the enrichment level of CdTe. For on-site measurement and process control energy-dispersive X-ray fluorescence spectrometry was used. Instrumental photon activation analysis using an electron linear accelerator as activating bremsstrahlung source is intended to be used later for iterative intermediate analysis of random samples for quality control. In this work, the feasibility of both methods for this task was studied.     

A review of sample preparation methods for the pesticide residue analysis in foods

The pesticide residues in foods have received increasing attention as one of the most important food safety issues. Therefore, more strict regulations on the maximum residue limits (MRLs) for pesticides in foods have been established in many countries and health organizations, based on the sensitive and reliable analysis methods of pesticide residues. However, the analysis of pesticide residues is a continuing challenge mainly because of the small quantities of analytes as well as the large amounts of interfering substances which can be co-extracted with them, often leading to experimental errors and damage to the analytical instruments. Thus, extensive sample preparation is often required for the pesticide residue analysis for the effective extraction of the analytes and removal of the interferences. This paper focuses on reviewing the recent development in the sample preparation methods for the pesticide residue analysis in foods since 2006. The methods include: liquid-liquid extraction (LLE), supercritical-fluid extraction (SFE), pressurized-liquid extraction (PLE), microwave-assisted extraction (MAE), ultrasound-assisted extraction (UAE), gel permeation chromatography (GPC), solid-phase extraction (SPE), molecularly imprinted polymers (MIPs), matrix solid-phase dispersion (MSPD), solid-phase micro-extraction (SPME), QuEChERS, cloud point extraction (CPE) and liquid phase micro-extraction (LPME), etc. Particularly their advantages, disadvantages and future perspectives will be discussed.     

Comparison of QuEChERS sample preparation methods for the analysis of pesticide residues in fruits and vegetables

This article describes the comparison of different versions of an easy, rapid and low-cost sample preparation approach for the determination of pesticide residues in fruits and vegetables by concurrent use of gas and liquid chromatography (GC and LC) coupled to mass spectrometry (MS) for detection. The sample preparation approach is known as QuEChERS, which stands for “quick, easy, cheap, effective, rugged and safe”. The three compared versions were based on the original unbuffered method, which was first published in 2003, and two interlaboratory validated versions: AOAC Official Method 2007.01, which uses acetate buffering, and European Committee for Standardization (CEN) Standard Method EN 15662, which calls for citrate buffering. LC–MS/MS and GC–MS analyses using each method were tested from 50 to 1000 ng/g in apple–blueberry sauce, peas and limes spiked with 32 representative pesticides. As expected, the results were excellent (overall average of 98% recoveries with 10% RSD) using all 3 versions, except the unbuffered method gave somewhat lower recoveries for the few pH-dependent pesticides. The different methods worked equally well for all matrices tested with equivalent amounts of matrix co-extractives measured, matrix effects on quantification and chemical noise from matrix in the chromatographic backgrounds. The acetate-buffered version gave higher and more consistent recoveries for pymetrozine than the other versions in all 3 matrices and for thiabendazole in limes. None of the versions consistently worked well for chlorothalonil, folpet or tolylfluanid in peas, but the acetate-buffered method gave better results for screening of those pesticides. Also, due to the recent shortage in acetonitrile (MeCN), ethyl acetate (EtOAc) was evaluated as a substitute solvent in the acetate-buffered QuEChERS version, but it generally led to less clean extracts and lower recoveries of pymetrozine, thiabendazole, acephate, methamidophos, omethoate and dimethoate. In summary, the acetate-buffered version of QuEChERS using MeCN exhibited advantages compared to the other tested methods in the study.     

Increased speed of steroid analysis by capillary GC and GC-MS; effects of sample pretreatment and sample introdution

Quantitative analysis of steroids and their metabolites in urine samples calls for increased speed of sample clean-up, of the derivatization procedure, and of separation. A fast procedure for sample pretreatment, which can be performed within 8 hours, is introduced and evaluated. It is shown that use of fast pretreatment in combination with narrow bore columns, which are compatible with existing instrumentation, can considerably increase, laboratory throughput. The effect of different sample introduction techniques (e.g. splitless, on-column, and moving needle) on column efficiency and resolution is demonstrated and discussed.     

Determination of sample size for validation of allergen-screening methods

For various levels of confidence (i.e., 80 and 90%) and ratios (K = sigmap2/sigmaN2, where sigmap2 and sigmaN2 are the analyte variances for the positive and negative distributions, respectively), sample sizes sufficient to test the requirements that a given method detects > or = 90% of the positives (> or = 5 ppm of a given analyte) while misclassifying < or = 10% of the negatives (implying a specificity rate, true negatives that will be correctly classified, of 90%) were estimated by using a rationale that minimizes the cost of sampling.     

Highly localized charges control electrostriction: reaction volumes for the reduction of mononuclear and bridged ruthenium complexes

Changes in electrostriction caused by the reduction of metal centers in monomeric Ru and bridged Ru/Fe complexes reported in this work are highly localized in a polar solvent such as water. In mononuclear complexes, such as [(edta-H)Ru(III)(H2O)], where the pendant carboxylate is protonated or not depending on pH, the charge that determines electrostricted solvent behavior is defined within distances encompassed by the first coordination sphere of the redox center (DeltaV(complex) = 1.4 +/- 0.6 cm3 mol(-1) (pH 4) or 0.9 +/- 0.6 cm3 mol(-1) (pH 1.1)). Furthermore, in dinuclear complexes, even differences in the ligand charge around the second metal center have insignificant effects on electrostrictive interaction with the solvent. Reduction of the Fe center in the systems [(NH3)5Ru(III)(mu-NC)Fe(III)(CN)5] and [(edta)Ru(III)(mu-NC)Fe(III)(CN)5]4- is virtually unaffected (-21.8 +/- 1.8 cm3 mol(-1) and -21.7 +/- 2.8 cm3 mol(-1), respectively) when the Ru center is changed from formally cationic (3+) to anionic (1-).