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Analytica Chimica Acta (v.768, #)
Ammonium chloride salting out extraction/cleanup for trace-level quantitative analysis in food and biological matrices by flow injection tandem mass spectrometry by Sergio C. Nanita; Nilusha L.T. Padivitage (pp. 1-11).
Display Omitted► A novel sample extraction/cleanup method for trace-level analysis in food and body fluids. ► NH4Cl salting out allows high-throughput part-per-billion analysis by FI/MS/MS. ► Flow injection tandem mass spectrometry improves pesticide residue analysis.A sample extraction and purification procedure that uses ammonium-salt-induced acetonitrile/water phase separation was developed and demonstrated to be compatible with the recently reported method for pesticide residue analysis based on fast extraction and dilution flow injection mass spectrometry (FED-FI-MS). The ammonium salts evaluated were chloride, acetate, formate, carbonate, and sulfate. A mixture of NaCl and MgSO4, salts used in the well-known QuEChERS method, was also tested for comparison. With thermal decomposition/evaporation temperature of <350°C, ammonium salts resulted in negligible ion source residual under typical electrospray conditions, leading to consistent method performance and less instrument cleaning. Although all ammonium salts tested induced acetonitrile/water phase separation, NH4Cl yielded the best performance, thus it was the preferred salting out agent. The NH4Cl salting out method was successfully coupled with FI/MS/MS and tested for fourteen pesticide active ingredients: chlorantraniliprole, cyantraniliprole, chlorimuron ethyl, oxamyl, methomyl, sulfometuron methyl, chlorsulfuron, triflusulfuron methyl, azimsulfuron, flupyrsulfuron methyl, aminocyclopyrachlor, aminocyclopyrachlor methyl, diuron and hexazinone. A validation study was conducted with nine complex matrices: sorghum, rice, grapefruit, canola, milk, eggs, beef, urine and blood plasma. The method is applicable to all analytes, except aminocyclopyrachlor. The method was deemed appropriate for quantitative analysis in 114 out of 126 analyte/matrix cases tested (applicability rate=0.90). The NH4Cl salting out extraction/cleanup allowed expansion of FI/MS/MS for analysis in food of plant and animal origin, and body fluids with increased ruggedness and sensitivity, while maintaining high-throughput (run time=30s/sample). Limits of quantitation (LOQs) of 0.01mgkg−1 (ppm), the ‘well-accepted standard’ in pesticide residue analysis, were achieved in >80% of cases tested; while limits of detection (LODs) were typically in the range of 0.001–0.01mgkg−1 (ppm). A comparison to a well-established HPLC/MS/MS method was also conducted, yielding comparable results, thus confirming the suitability of NH4Cl salting out FI/MS/MS for pesticide residue analysis.
Keywords: Tandem mass spectrometry; Flow injection analysis; Pesticide residue analysis; Multiresidue methods; Salting out; Ammonium chloride
Liquid chromatographic methods for the quantification of catecholamines and their metabolites in several biological samples—A review by Joana Bicker; Ana Fortuna; Gilberto Alves; Amílcar Falcão (pp. 12-34).
Display Omitted► HPLC methods for quantifying catecholamines and their metabolites are reviewed. ► The collection, handling and treatment of biological samples are analyzed. ► Chromatographic variables are discussed and detection systems are compared.The measurement of catecholamines and their metabolites in biological samples remains a current analytical challenge, in spite of the great diversity of methodologies that have been developed throughout the years. High-performance liquid chromatography is the standard method for their separation and quantification in biological samples, either coupled with electrochemical, fluorescence, chemiluminescence or mass spectrometry detection. This review summarizes the most important physicochemical properties of catecholamines, the wide panoply of sample preparation techniques and the main issues to consider during the development of chromatographic methods. The major difficulties encountered during the optimization of these procedures are related with the high tendency of catecholamines to oxidize and the very low quantities at which they exist in biological matrices. Herein, the most important aspects that ought to be considered during collection, treatment and storage of fluid and tissue samples intended for catecholamine analysis are underlined, the chromatographic conditions are compared and the technical advantages and limitations of each detection system are discussed.
Keywords: Catecholamine; Bioanalysis; High-performance liquid chromatography; Electrochemical detection; Fluorescence detection; Mass spectrometry detectionAbbreviations; AD; aldehyde dehydrogenase; AR; aldehyde reductase; BDS; base-deactivated silica; COMT; catechol-; O; -methyltransferase; CSF; cerebrospinal fluid; DHBA; 3,4-dihydroxybenzylamine; DHMA; 3,4-dihydroxymandelic acid; DHPG; 3,4-dihydroxyphenylglycol; DOPAC; 3,4-dihydroxyphenylacetic acid; DOPAL; 3,4-dihydroxyphenylacetaldehyde; DOPEGAL; 3,4-dihydroxyphenylglycolaldehyde; DOPET; 3,4-dihydroxyphenylethanol; DPBA; diphenylboronic acid; DPE; 1,2-diphenylethylenediamine; ECD; electrochemical detection; EDTA; ethylenediaminetetraacetic acid; FMOC-Cl; fluorenylmethyloxycarbonyl chloride; HILIC; hydrophilic interaction liquid chromatography; HLB; hydrophilic–lipophilic balance; HPLC; high-performance liquid chromatography; HVA; homovanillic acid; LC; liquid chromatography; L; -DOPA; L-3,4-dihydroxyphenylalanine; LLE; liquid–liquid extraction; LOQ; limit of quantification; MAO; monoamine oxidase; MHPG; 3-methoxy-4-hydroxyphenylglycol; MN; metanephrine; 3-MT; 3-methoxytyramine; MOPEGAL; 3-methoxy-4-hydroxyphenylglycolaldehyde; MRM; multiple reaction monitoring; MS; mass spectrometry; MS/MS; tandem mass spectrometry; NMN; normetanephrine; ODS; octadecylsilane; PBA; phenylboronic acid; PFOEI; 2-(perfluorooctyl)ethylisocyanate; PGC; porous graphitic carbon; POCL; peroxyoxalate chemiluminescence; RT; room temperature; SCX; strong-cation exchange; SPE; solid-phase extraction; SRM; selective reaction monitoring; TDPO; bis[2-(3,6,9-trioxadecanyloxycarbonyl)-4-nitrophenyl]oxalate; TFC; turbulent flow chromatography; THI; trihydroxyindol; TOABr; tetraoctylammonium bromide; UHPLC; ultra-fast high-performance liquid chromatography; VMA; vanillylmandelic acid
Determination of selenium using atomically imprinted polymer (AIP) and hydride generation atomic absorption spectrometry by Grazielle Cabral de Lima; Ayla Campos do Lago; Arley Alves Chaves; Pedro Sergio Fadini; Pedro Orival Luccas (pp. 35-40).
Display Omitted► Atomically imprinted polymers (AIP) was synthesized for the first time. ► The material exhibited adequate sensitivity expressed by high preconcentration factor. ► A method for on-line selenium determination by HG-AAS in food samples was developed.This paper describes selenium determination based on Se0 preconcentration in the imprinted polymer (synthesized with 2.25mmol SeO2, 4-vinylpyridine and 1-vinylimidazole) with subsequent detection on-line in HG-FAAS. During the synthesis, SeO2 is reduced to Se (0). Therefore, there are no MIP neither IIP in the present work, thus we denominated: AIP, i.e., atomically imprinted polymers. For the optimization of analytical parameters Doehlert design was used. The method presented limit of detection and limit of quantification of 53 and 177ngL−1, respectively, and linear range from 0.17 up to 6μgL−1 ( r=0.9936). The preconcentration factor (PF), consumptive index (CI) and concentration efficiency (CE) were 232; 0.06mL and 58min−1 respectively. The proposed method was successfully applied to determine Se in Brazil nuts (0.33±0.03mgkg−1), apricot (0.46±0.02mgkg−1), white bean (0.47±0.03mgkg−1), rice flour (0.47±0.02mgkg−1) and milk powder (0.22±0.01mgkg−1) samples. It was possible to do 12 analyzes per hour. Accuracy was checked and confirmed by analyzing certified reference material (DORM-2, dogfish muscle), and samples precision was satisfactory with RSD lower than 10%.
Keywords: Selenium; Imprinted polymer; Hydride generation flame atomic absorption spectrometry; Preconcentration
Statistical discrimination of steroid profiles in doping control with support vector machines by Pieter Van Renterghem; Pierre-Edouard Sottas; Martial Saugy; Peter Van Eenoo (pp. 41-48).
Display Omitted► Support vector machines classifies steroid profiles in doping analysis. ► A general detection model was developed with satisfying detection windows. ► Good diagnostic performance was achieved. ► In combination with the concept of the biological passport, this model is a promising anti-doping strategy.Due to their performance enhancing properties, use of anabolic steroids (e.g. testosterone, nandrolone, etc.) is banned in elite sports. Therefore, doping control laboratories accredited by the World Anti-Doping Agency (WADA) screen among others for these prohibited substances in urine. It is particularly challenging to detect misuse with naturally occurring anabolic steroids such as testosterone (T), which is a popular ergogenic agent in sports and society.To screen for misuse with these compounds, drug testing laboratories monitor the urinary concentrations of endogenous steroid metabolites and their ratios, which constitute the steroid profile and compare them with reference ranges to detect unnaturally high values. However, the interpretation of the steroid profile is difficult due to large inter-individual variances, various confounding factors and different endogenous steroids marketed that influence the steroid profile in various ways.A support vector machine (SVM) algorithm was developed to statistically evaluate urinary steroid profiles composed of an extended range of steroid profile metabolites. This model makes the interpretation of the analytical data in the quest for deviating steroid profiles feasible and shows its versatility towards different kinds of misused endogenous steroids. The SVM model outperforms the current biomarkers with respect to detection sensitivity and accuracy, particularly when it is coupled to individual data as stored in the Athlete Biological Passport.
Keywords: Statistical discrimination; Support vector machines; Steroid profiling; Doping analysis
Use of the bootstrap and permutation methods for a more robust variable importance in the projection metric for partial least squares regression by N.L. Afanador; T.N. Tran; L.M.C. Buydens (pp. 49-56).
Display Omitted► A more robust variable importance in the projection metric (VIP) is explored. ► Bootstrap and permutation methods in relation to VIP robustness are presented. ► The selective performance of the VIP vs. the proposed method is assessed.Bio-pharmaceutical manufacturing is a multifaceted and complex process wherein the manufacture of a single batch hundreds of processing variables and raw materials are monitored. In these processes, identifying the candidate variables responsible for any changes in process performance can prove to be extremely challenging. Within this context, partial least squares (PLS) has proven to be an important tool in helping determine the root cause for changes in biological performance, such as cellular growth or viral propagation. In spite of the positive impact PLS has had in helping understand bio-pharmaceutical process data, the high variability in measured response ( Y) and predictor variables ( X), and weak relationship between X and Y, has at times made root cause determination for process changes difficult. Our goal is to demonstrate how the use of bootstrapping, in conjunction with permutation tests, can provide avenues for improving the selection of variables responsible for manufacturing process changes via the variable importance in the projection (PLS-VIP) statistic. Although applied uniquely to the PLS-VIP in this article, the generality of the aforementioned methods can be used to improve other variable selection methods, in addition to increasing confidence around other estimates obtained from a PLS model.
Keywords: Partial least squares; Bootstrapping; Permutation; Variable importance
Parsimonious and robust multivariate calibration with rational function Least Absolute Shrinkage and Selection Operator and rational function Elastic Net by P. Teppola; V.-M. Taavitsainen (pp. 57-68).
Display Omitted► A unique approach using rational functions and Elastic Net. ► Chemometric preprocessing not needed when using rational functions. ► Building parsimonious models in an automated way. ► Automated variable selection. ► A full continuum of feasible solutions with parsimony and/or smoothness.This paper presents new methods for multivariate calibration. A unique aspect is that this approach uses rational functions with either Least Absolute Shrinkage and Selection Operator (LASSO) or Elastic Net (ENET), and builds parsimonious models in an automated way via cross-validation. Rational function modeling provides robustness, as will be briefly demonstrated. Interestingly, rational function models are also flexible, in that occasionally they are reduced to ordinary linear models based on cross-validation. Thus, model complexity is not forced to take the form of rational functions.Additional benefits arise from the use of LASSO and ENET. While LASSO uses only ℓ1 norm on regression coefficients, ENET combines the best of both worlds by using ℓ1 and ℓ2 norms. The former (ℓ1) provides variable selection while the latter (ℓ2) handles collinearity via shrinkage of regression coefficients. Rational functions are highly collinear if full rank is used and, thus, not necessarily robust unless either ℓ1 or ℓ2 norm is used on the regression coefficients. The use of ℓ1 norm allows for a more parsimonious model that can potentially be more robust. This is contrary to the use of a broadband spectrum that is likely to be contaminated at some point in the future by unknown spectral interferences. The real benefits seem to originate from the combination of rational functions and ENET. Note that LASSO solutions form a subset of ENET solutions and are thus included in ENET.
Keywords: Chemometrics; Multivariate calibration; Rational function; LASSO; Elastic Net; RF-ENET; Multi-point; NIR
Preparation of cobalt-tetraphenylporphyrin/reduced graphene oxide nanocomposite and its application on hydrogen peroxide biosensor by Longzhen Zheng; Dan Ye; Leyan Xiong; Jingpeng Xu; Kun Tao; Zhijun Zou; Danlin Huang; Xiaowei Kang; Shaoming Yang; Jian Xia (pp. 69-75).
Display Omitted► CoTPP/RGO nanocomposite was prepared by a π–π stacking interaction. ► CoTPP/RGO showed electrocatalytic activity for both oxidation and reduction of H2O2. ► The high sensitivity was due to the synergy effect between CoTPP and RGO. ► The CoTPP/RGO electrode showed good anti-interfering ability.A novel cobalt-tetraphenylporphyrin/reduced graphene oxide (CoTPP/RGO) nanocomposite was prepared by a π–π stacking interaction and characterized by ultraviolet–visible absorption spectroscopy (UV–vis), Fourier transform infrared spectroscopy (FTIR) and electrochemical impedance spectroscopy (EIS). The CoTPP/RGO nanocomposite exhibited high electrocatalytic activity both for oxidation and reduction of H2O2. The current response was linear to H2O2 concentration with the concentration range from 1.0×10−7 to 2.4×10−3molL−1 ( R=0.998) at the reductive potential of −0.20V and from 1.0×10−7 to 4.6×10−4molL−1 ( R=0.996) at the oxidative potential of +0.50V. The H2O2 biosensor showed good anti-interfering ability towards oxidative interferences at the oxidative potential of +0.50V and good anti-interfering ability towards reductive interferences at the reductive potential of −0.20V.
Keywords: Cobalt-tetraphenylporphyrin; Reduced graphene oxide; Nanocomposite; Hydrogen peroxide biosensor; Anti-interfering ability
Electrochemical strategy for sensing DNA methylation and DNA methyltransferase activity by Gang Lin Wang; Long Yin Zhou; Hong Qun Luo; Nian Bing Li (pp. 76-81).
A novel and highly sensitive signal-off electrochemical method to monitor DNA methylation and DNA adenine methylation methyltransferase activity is proposed.Display Omitted► An electrochemical strategy for sensing DNA methylation and DNA methyltransferase activity was proposed. ► A methylation-responsive DNA biosensor was fabricated. ► This assay was based on electrostatic adsorption of [Ru(NH3)6]3+ on the anionic DNA biosensor. ► A low detection limit (0.18UmL−1) was obtained without any amplification. ► This strategy can be applied to qualification of activity of other methyltransferases.The present work demonstrates a novel signal-off electrochemical method for the determination of DNA methylation and the assay of methyltransferase activity using the electroactive complex [Ru(NH3)6]3+ (RuHex) as a signal transducer. The assay exploits the electrostatic interactions between RuHex and DNA strands. Thiolated single strand DNA1 was firstly self-assembled on a gold electrode via Au–S bonding, followed by hybridization with single strand DNA2 to form double strand DNA containing specific recognition sequence of DNA adenine methylation MTase and methylation-responsive restriction endonuclease Dpn I. The double strand DNA may adsorb lots of electrochemical species ([Ru(NH3)6]3+) via the electrostatic interaction, thus resulting in a high electrochemical signal. In the presence of DNA adenine methylation methyltransferase and S-adenosyl-l-methionine, the formed double strand DNA was methylated by DNA adenine methylation methyltransferase, then the double strand DNA can be cleaved by methylation-responsive restriction endonuclease Dpn I, leading to the dissociation of a large amount of signaling probes from the electrode. As a result, the adsorption amount of RuHex reduced, resulting in a decrease in electrochemical signal. Thus, a sensitive electrochemical method for detection of DNA methylation is proposed. The proposed method yielded a linear response to concentration of Dam MTase ranging from 0.25 to 10UmL−1 with a detection limit of 0.18UmL−1 (S/N=3), which might promise this method as a good candidate for monitoring DNA methylation in the future.
Keywords: Methyltransferase; Electrochemical strategy; Hexaammineruthenium(III) ion; Differential pulse voltammetry
Direct analysis of formate in human plasma, serum and whole blood by in-line coupling of microdialysis to capillary electrophoresis for rapid diagnosis of methanol poisoning by Pavel Kubáň; Petr Boček (pp. 82-89).
Display Omitted► In-line coupling of microdialysis to CE-C4D is presented ► Formate is directly analyzed in plasma, serum and whole blood samples ► Electrokinetic injection across dialysis membrane ensures efficient sample clean-up ► Formate, as a marker of methanol intoxication, is determined in less than 4min ► Significant formate levels were found in serum of a methanol poisoned patient.A simple method using direct injection of human blood samples and quantitative analysis of formate was developed for rapid diagnosis of methanol poisoning. A sample pretreatment device including a 500Da molecular weight cut-off dialysis membrane was in-line coupled to capillary electrophoresis with capacitively coupled contactless conductivity detection (CE-C4D). 50μL of 1:9 diluted blood samples and 50μL of DI water were filled into the donor and the acceptor chamber, respectively, and small ionic species in blood samples were electrokinetically injected across the dialysis membrane directly into the separation capillary. Matrix components, such as red blood cells, proteins, lipids and other high molecular weight compounds, were retained by the dialysis membrane and did not interfere with subsequent CE separation. Formate was separated from other small anions in an optimized background electrolyte solution consisting of 20mMl-histidine and 25mMl-glutamic acid at pH 4.8. The method showed excellent analytical parameters in terms of repeatability and linearity; RSD values for migration times and peak areas at a formate concentration typical for methanol poisoning were below 0.3% and 7.4%, respectively, and linear calibration curves with correlation coefficients better than 0.999 were obtained. Limit of detection and limit of quantification were 15 and 50μM formate in original (undiluted) blood samples, respectively. The method was applied to determination of formate in serum samples of a patient diagnosed with acute methanol poisoning.
Keywords: Capacitively coupled contactless conductivity detection; Capillary electrophoresis; Formate; Methanol poisoning; Microdialysis; In-line sample treatment
Sensitive ergotamine determination in pharmaceuticals and biological samples using cloud point preconcentration and spectrofluorimetric detection by Chien C. Wang; Liliana P. Fernández; María Roxana Gómez (pp. 90-95).
Display Omitted► A highly efficient cloud point extraction method was developed for ergotamine. ► Direct gel-state fluorescence determination was performed after extraction. ► Emission advantages of undiluted surfactant rich phase were explored for the first time. ► A total enhancement factor of 1325 was achieved for ergotamine determination. ► The simple, low cost, non-toxic methodology was successfully applied to real samples.A new cloud point extraction (CPE) method for ergotamine analysis using fluorimetric detection is described. Ergotamine from an aqueous solution was preconcentrated into a smaller surfactant-rich phase using nonionic surfactant polyoxyethylene(7.5)nonylphenylether (PONPE 7.5). Differently from the conventional CPE procedure in which the resulting surfactant-rich phase is diluted by a fluidificant before its analysis, in this method the fluorescence measurements were carried out directly onto the undiluted surfactant-rich phase. The high viscosity provided by the undiluted surfactant rich phase greatly improved the fluorescence emission of ergotamine, leading to a total enhancement factor of 1325. This spectral advantage plus the preconcentration factor achieved, contributed to the method sensitivity allowing the ergotamine determination at trace level concentration. Under optimal experimental conditions, a linear calibration curve was obtained from 3.81×10−7 to 1.10μgmL−1, with detection and quantification limits of 0.11 and 0.38pgmL−1, respectively. The accuracy and versatility of the present methodology were proved by analyzing ergotamine in real samples of different natures such as pharmaceuticals, urine and saliva.
Keywords: Ergotamine; Cloud point extraction; Spectrofluorimetry; Pharmaceuticals; Urine; Saliva
Automated high performance liquid chromatography with on-line reduction of disulfides and chemiluminescence detection for determination of thiols and disulfides in biological fluids by Shouli Bai; Qingshuo Chen; Chao Lu; Jin-Ming Lin (pp. 96-101).
Display Omitted► An on-line Zn(II)-TCEP reduction column for disulfides is fabricated. ► This reduction column is coupled with HPLC-CL system for assay of thiols and disulfides. ► The optimum pH for disulfides reduction is compatible with that of the HPLC mobile phase. ► The proposed method has been applied to analyze real samples.In general, the reduction of disulfide bonds with tris(2-carboxyethyl)phosphine (TCEP) is performed using off-line operation, which is not only time-consuming but also vulnerable to the spontaneous re-oxidation of thiols during sample preparation and subsequent analysis procedures. To the best of our knowledge, there has been not any case on the on-line reduction for biological disulfides coupled with high performance liquid chromatography (HPLC). In this study, these obstacles are overcome by packing Zn(II)-TCEP complexes into a home-made column. The as-synthesized Zn(II)-TCEP complexes enable efficient reduction of disulfide bonds at pH 3.0. This acidic pH value was compatible with that of the mobile phase for HPLC separation of thiols and disulfides. Therefore, using fluorosurfactant-prepared triangular gold nanoparticles as HPLC postcolumn specific chemiluminescence (CL) reagents for thiols, the feasibility of the established on-line reduction column has been confirmed for the direct identification of both thiols and disulfides by incorporating this reduction column into a single chromatographic separation. Detection limits for these analytes range from 8.3 to 25.4nM and the linear range in a log–log plot can comprise three orders of magnitude. Finally, the utility of this automated on-line reduction of disulfides-HPLC-CL system has been demonstrated for the reliable determination of thiols and disulfides in human urine and plasma samples.
Keywords: On-line reduction; Thiols; Disulfides; Chemiluminescence; High performance liquid chromatography
Performance of the linear ion trap Orbitrap mass analyzer for qualitative and quantitative analysis of drugs of abuse and relevant metabolites in sewage water by Lubertus Bijlsma; Erik Emke; Félix Hernández; Pim de Voogt (pp. 102-110).
Display Omitted► A methodology was developed for the determination of 24 drugs of abuse in sewage waters. ► Quantitative analyses were performed using liquid chromatography–HR Orbitrap mass spectrometer. ► Compared to QqQ results, Orbitrap is almost equally sensitive. ► Accurate mass full scan data allowed retrospective analysis.This work illustrates the potential of liquid chromatography coupled to a hybrid linear ion trap Fourier Transform Orbitrap mass spectrometer for the simultaneous identification and quantification of 24 drugs of abuse and relevant metabolites in sewage water. The developed methodology consisted of automatic solid-phase extraction using Oasis HLB cartridges, chromatographic separation of the targeted drugs, full-scan accurate mass data acquisition under positive electrospray ionization mode over an m/ z range of 50–600Da at a resolution of 30,000 FWHM and simultaneous MS n measurements to obtain information of fragment ions generated in the linear ion trap. Accurate mass of the protonated molecule, together with at least one nominal mass product ion and retention time allowed the confident identification of the compounds detected in these complex matrices. In addition to the highly reliable qualitative analysis, Orbitrap analyzer also proved to have satisfactory potential for quantification at sub-ppb analyte levels, a possibility that has been very little explored in the literature until now. The limits of quantification ranged from 4 to 68ngL−1 in influent sewage water, and from 2 to 35ngL−1 in effluent, with the exception of MDA, morphine and THC that presented higher values as a consequence of the high ionization suppression in this type of samples. Satisfactory recoveries (70–120%) and precision (<30%) for the overall procedure were obtained for all compounds with the exception of meta-chlorophenylpiperazine, methylphenidate and ketamine. Isotope-labelled internal standards were added to sewage samples as surrogates in order to correct for matrix effects and also for possible losses during sample treatment. The methodology developed was applied to sewage water samples from the Netherlands (influent and effluent), and the results were compared with those obtained by LC–MS/MS with triple quadrupole. Several drugs of abuse could be identified and quantified, mainly MDMA, benzoylecgonine, codeine, oxazepam and temazepam. Orbitrap also showed potential for retrospective investigation of ketamine metabolites in the samples without the need of additional analysis.
Keywords: Drugs of abuse; Accurate mass; Orbitrap analyzer; High resolution mass spectrometry; Quantitative analysis; Sewage water
A new strategy for the discovery of epimedium metabolites using high-performance liquid chromatography with high resolution mass spectrometry by Ying Jin; Cai-Sheng Wu; Jin-Lan Zhang; Ying-Fei Li (pp. 111-117).
Display Omitted► A new metabolite discovery strategy was established using HPLC–HRMS and MTSF technique. ► Metabolites of epimedium extract, a well-known TCM were successfully discovered and identified by the new strategy. ► A total of 115 metabolites with 11 structural skeletons were reported. ► The MTSF technique showed superior efficiency and selectivity than NLF, PIF and MDF.In this paper, a new strategy of drug metabolite discovery and identification was established using high-performance liquid chromatography with high resolution mass spectrometry (HPLC–HRMS) and a mass spectral trees similarity filter (MTSF) technique. The MTSF technique was developed as a means to rapidly discover comprehensive metabolites from multiple active components in a complicated biological matrix. Using full-scan mass spectra as the stem and data-dependent subsequent stage mass spectra to form branches, the HRMS and multiple-stage mass spectrometric data from detected compounds were converted to mass spectral trees data. Potential metabolites were discovered based on the similarity between their mass spectral trees and that known compounds or metabolites in a mass spectra trees library. The threshold value for match similarity scores was set at above 200, allowing approximately 80% of interference to be filtered out. A total of 115 metabolites of five flavonoid monomers (epimedin A, epimedin B, epimedin C, icariin, and baohuoside I) and herbal extract of epimedium were discovered and identified in rats via this new strategy. As a result, a metabolic profile for epimedium was obtained and a metabolic pathway was proposed. In addition, comparing to the widely used neutral loss filter (NLF), product ion filter (PIF), and mass defect filter (MDF) techniques, the MTSF technique was shown superior efficiency and selectivity for discovering and identifying metabolites in traditional Chinese medicine (TCM).
Keywords: Epimedium; Mass spectral trees similarity filter; High-performance liquid chromatography with high resolution mass spectrometry; Metabolite discovery
UPLC-ESI-QTOF/MS and multivariate data analysis for blood plasma and serum metabolomics: Effect of experimental artefacts and anticoagulant by Thaer Barri; Lars Ove Dragsted (pp. 118-128).
Display Omitted► We studied metabolite profiles in blood serum and different plasma preparations. ► Interferences in serum and plasma samples and anticoagulant effects were identified. ► Serum samples showed features of polymeric material, peptides, and xanthines. ► Formate ion clusters and effect of anticoagulants were observed in plasma samples. ► Heparin plasma is advised and serum is a second choice for LC-ESI/MS metabolomics.Clotting and anticoagulation of blood samples may give rise to different metabolic profiles of serum and plasma samples, respectively. The anticoagulant used for blood plasma preparation may affect the resulting metabolic profile due to different mechanisms involved in anticoagulation by various agents, e.g. heparin, EDTA and citrate. In the present study, we looked into metabolite and other differences in matched serum and plasma samples and different plasma preparations by using untargeted UPLC-ESI-QTOF/MS profiling and multivariate data analysis (PCA and OPLS-DA). Metabolite differences between serum and plasma samples were mainly related to small peptides reflecting presence or absence of coagulation. Only subtle metabolite differences between the different plasma preparations were noticed, which were primarily related to ion suppression or enhancement caused by citrate and EDTA anticoagulants. For the first time, we also report that anticoagulant counter cation (Na+ or K+) in Na-citrate and K-EDTA plasma can make some metabolites more dominant in ESI-MS. Polymeric material residues originating from blood collection tubes for serum preparation were observed only in serum samples. Hypoxanthine and xanthine were found at higher levels in serum than in plasma samples, possibly due to release from the clot. Mass spectral features of sodium formate and potassium formate ion clusters were detected in citrate and EDTA plasma samples, respectively, originating from formate in mobile phase and Na+ (in Na-citrate tubes) and K+ (in K-EDTA tubes). Among the anticoagulants, heparin is recommended for plasma samples used for LC-ESI/MS-based metabolomics of hydrophilic compounds because no plasma interferences or matrix effects were noticed for this polarity range. Citrate and EDTA should be avoided since interferences and serious matrix effects were encountered on some co-eluting polar metabolites. Serum is recommended as a second choice and an alternative to plasma. In conclusion, heparin plasma or serum should be the order of best choice for LC-ESI/MS-based metabolomics research.
Keywords: Metabolomics; Mass spectrometry; Blood plasma; Serum; Anticoagulant; Matrix effect
A disposable blood cyanide sensor by Yong Tian; Purnendu K. Dasgupta; Sari B. Mahon; Jian Ma; Matthew Brenner; Jian-HuaWang; Gerry R. Boss (pp. 129-135).
Display Omitted► Cyanide in blood is determined in ∼4min by an inexpensive sensor. ► As little as 20μL sample can be used. ► The recommended sample volume, 50μL, can be obtained by finger prick. ► 50μL blood sample provides for an LOD of 2.2μM and upper linear limit of 60μM. ► With 1mL sample, baseline cyanide levels in blood can be measured.Deaths due to smoke inhalation in fires are often due to poisoning by HCN. Rapid administration of antidotes can result in complete resuscitation of the patient but judicious dosing requires the knowledge of the level of cyanide exposure. Rapid sensitive means for blood cyanide quantitation are needed. Hydroxocyanocobinamide (OH(CN)Cbi) reacts with cyanide rapidly; this is accompanied by a large spectral change. The disposable device consists of a pair of nested petri dish bottoms and a single top that fits the outer bottom dish. The top cover has a diametrically strung porous polypropylene membrane tube filled with aqueous OH(CN)Cbi. One end of the tube terminates in an amber (583nm) light emitting diode; the other end in a photodiode via an acrylic optical fiber. An aliquot of the blood sample is put in the inner dish, the assembly covered and acid is added through a port in the cover. Evolved HCN diffuses into the OH(CN)Cbi solution and the absorbance in the long path porous membrane tube cell is measured within 160s. The LOD was 0.047, 1.0, 0.15, 5.0 and 2.2μM, respectively, for water (1mL), bovine blood (100μL, 1mL), and rabbit blood (20μL, 50μL). RSDs were<10% in all cases and the linear range extended from 0.5 to 200μM. The method was validated against a microdiffusion approach and applied to the measurement of cyanide in rabbit and human blood. The disposable device permits field measurement of blood cyanide in <4min.
Keywords: Porous membrane; HCN; Cobinamide; Liquid core waveguide
Micelle-induced multiple performance improvement of fluorescent probes for H2S detection by Haiyu Tian; Junhong Qian; Hongyan Bai; Qian Sun; Lingyi Zhang; Weibing Zhang (pp. 136-142).
Two colorimetric and turn-on fluorescent probes for the selective recognition of H2S were designed and synthesized. Rapid response and high sensitivity (the detection limit as low as 20nM) were realized in CTAB micelles. The probes could measure H2S levels in fetal bovine serum without any sample pretreatment.Display Omitted► Two new H2S probes based on its reducing property were synthesized. ► Rapid response and high sensitivity (the detection limit as low as 20nM) towards H2S were realized in CTAB micelle. ► The probes could measure H2S levels in fetal bovine serum without any prior sample processing.In this paper, two colorimetric and turn-on fluorescent probes N-[2-(2-hydroxy)-ethoxy] ethyl-4-azido-1,8-naphthalimide (SS1) and N-butyl-4-azido-1,8-naphthalimide (SS2) for selective recognition of H2S were designed and synthesized. The probes were constructed by incorporating an azido group into the naphthalimide fluorophore as a specifical reaction group for sulfide utilizing its reducing property. Once treated with H2S, the azido groups of the probes were converted to amino groups and the solutions’ color changed from colorless to yellow companied with a strong yellow-green fluorescence. Rapid and sensitive responses of the probes towards H2S were achieved in the presence of cationic surfactant cetyltrimethyl ammonium bromide (CTAB): the reaction was completed within 10min in CTAB compared to more than 4h in buffer solution, and the detection limit decreased from 0.5μM to 20nM. High selectivity and good competition of both probes towards H2S over other 11 ions and 2 reducing agents were realized in CTAB micelle. An overall linear concentration range of 0.05μM to 1mM was achieved with the assistance of differently charged surfactants CTAB and sodium dodecyl sulfate (SDS). The probes were applied to rapidly and sensitively detect H2S levels in fetal bovine serum without any pretreatment of the sample.
Keywords: Fluorescent probe; Naphthalimide; H; 2; S; Cetyltrimethyl ammonium bromide (CTAB); Fetal bovine serum