Application of DNPH Derivatization with LC/MS to the Identification of Polar Carbonyl Disinfection Byproducts in Drinking Water

A qualitative method using 2,4-dinitrophenylhydrazine (DNPH) derivatization followed by analysis with liquid chromatography (LC)/negative ion-electrospray mass spectrometry (MS) was developed for analyzing and identifying highly polar aldehydes and ketones in ozonated drinking water. Using this method, aldehydes could be easily distinguished from ketones by differences in their mass spectra and chromatographic behavior. Results for many polar-substituted aldehyde and ketone standards are presented, as well as the identification of polar disinfection by-products (DBPs) in ozonated drinking water from full-scale plants and laboratory-scale ozonation of humic acid. One polar DBP identified has not been previously reported. This method could also potentially be used as a tool to identify carbonyl-containing DBPs from disinfectants other than ozone. However, the detection limits for the DNPH-LC/MS method are not as low as for the pentafluorobenzylhydroxylamine (PFBHA)-gas chromatography (GC)/MS method (LC/MS is typically not as sensitive as GC/MS). Therefore, it is not recommended that this method replace the PFBHA-GC/MS method, but be used as a supplement to enable the identification of highly polar carbonyl-containing DBPs that would not be possible by GC/MS.     

高效液相色谱-电喷雾串联质谱法测定水产品中14种喹诺酮类与磺胺类药物残留

建立了高效液相色谱-电喷雾串联质谱法测定水产品中恩诺沙星、环丙沙星、双氟沙星、沙拉沙星、氟甲喹、喹酸、磺胺嘧啶、磺胺甲唑、磺胺喹啉、磺胺甲基嘧啶、磺胺二甲氧嘧啶、磺胺二甲基嘧啶、磺胺间二甲氧嘧啶、甲氧苄胺嘧啶共14种常用喹诺酮类与磺胺类兽药的残留检测方法。样品制备后,采用1%乙酸-乙腈提取液提取,用正己烷净化处理后,采用LC/MS/MS电喷雾电离(ESI),多反应监测(MRM)正离子模式检测,外标法定量。在0～100μg/kg范围内14种兽药的线性相关系数均>0.99。在添加浓度5～50μg/kg范围内,14种药物的回收率在70.0%～110%,相对标准偏差(RSD)均在12%以内。方法的检出限为0.1～0.5μg/kg。     

Characterisation of end groups in poly(2-hydroxyethyl methacrylate) by means of electrospray ionisation-mass spectrometry/mass spectrometry (ESI-MS/MS)

Poly(2-hydroxyethyl methacrylate) (poly(HEMA)) has been characterised by means of electrospray ionisation-mass spectrometry/mass spectrometry (ESI-MS/MS), in order to evaluate this technique for the generation of end group information. Low energy collision-induced dissociation (CID) data from poly(HEMA) enabled information on both end groups of the polymer chain to be gleaned, in a similar fashion to that proposed previously for other methacrylate polymer systems. Exact-mass CID information was employed to aid the understanding of the dissociation mechanism of the polymer. Some additional fragmentation pathways, compared to other methacrylate polymer systems, are proposed. An example of how software can aid the interpretation of the MS/MS data is also shown.     

Screening of Aerosol Filter Samples for PAHs and Nitro-PAHs by Laser Desorption Ionization TOF Mass Spectrometry

Direct and selective screening of aerosol particulate matter for polycyclic aromatic hydrocarbons (PAHs) and nitrated polycyclic aromatic hydrocarbons (nitro-PAHs) is achieved using laser desorption ionization time-of-flight (LDI TOF) mass spectrometry. Desorption and ionization of collected aerosol particulate matter was accomplished using pulsed UV radiation at 266 nm. PAHs were detected in positive ion spectra, while nitro-PAHs were selectively detected in negative ion spectra. Direct laser desorption ionization circumvents extraction procedures necessary for HPLC or gas chromatography/mass spectrometry (GC/MS) analyses, and such screening offers potential cost saving by identifying samples which contain too little PAH for GC/MS analyses to be productive. Applicability of the LDI TOF method was demonstrated by collecting aerosol particles of less than 2.5 mu m aerodynamic diameter (PM 2 . 5) on Teflon filters from inside an urban bus terminal. Sampling of small air volumes (0.32-0.98 m3) was sufficient for LDI TOF analysis. Positive ion mass spectra of all collected aerosol samples exhibited peaks attributed to a wide range of PAHs. Of primary importance, selective ionization and detection of less abundant and more toxic nitro-PAHs is demonstrated in the negative ion spectra. GC/MS analyses of duplicate filters confirmed laser desorption ionization analyses and assisted identification of specific PAH isomers.     

Quantitative Analysis of Phytosterols in Edible Oils Using APCI Liquid Chromatography–Tandem Mass Spectrometry

Previous methods for the quantitative analysis of phytosterols have usually used GC–MS and require elaborate sample preparation including chemical derivatization. Other common methods such as HPLC with absorbance detection do not provide information regarding the identity of the analytes. To address the need for an assay that utilizes mass selectivity while avoiding derivatization, a quantitative method based on LC–tandem mass spectrometry (LC–MS–MS) was developed and validated for the measurement of six abundant dietary phytosterols and structurally related triterpene alcohols including brassicasterol, campesterol, cycloartenol, β-sitosterol, stigmasterol, and lupeol in edible oils. Samples were saponified, extracted with hexane and then analyzed using reversed phase HPLC with positive ion atmospheric pressure chemical ionization tandem mass spectrometry and selected reaction monitoring. The utility of the LC–MS–MS method was demonstrated by analyzing 14 edible oils. All six compounds were present in at least some of the edible oils. The most abundant phytosterol in all samples was β-sitosterol, which was highest in corn oil at 4.35 ± 0.03 mg/g, followed by campesterol in canola oil at 1.84 ± 0.01 mg/g. The new LC–MS–MS method for the quantitative analysis of phytosterols provides a combination of speed, selectivity and sensitivity that exceed those of previous assays.     

High-Molecular-Weight Polycyclic Aromatic Hydrocarbons in the Area and Vicinity of the Deza Chemical Plant,Czech Republic

Polycyclic aromatic hydrocarbons (PAHs) with molecular weight exceeding 278 amu were analyzed in air, water, and soils from the area and vicinity of the DEZA Chemical Plant (Vala w ské Mezi q í ) í, Czech Republic). Air and water were sampled using semipermeable membrane devices (SPMDs); grab sampling was applied for soils. Laser desorption/ionization-time-of-flight mass spectrometry (LDI-TOF MS) and liquid chromatography/ion trap mass spectrometry with atmospheric pressure chemical ionization (LC/APCI-ITMS) were employed for the quick assessment of PAH distribution and for the identification and quantification of some high-molecular-weight PAHs. Compounds with molecular mass up to 450 u were found. LDI-TOF mass spectra and selected LC/APCI-ITMS profiles (m/z 303, m/z 327, and m/z 351) were compared to identify potential source of contamination in this locality. High-molecular-weight PAHs were found in all environmental compartments in the area studied; their levels were quite high close to their source and decreased sharply with increasing distance from it.     

Measurement of Ether Phospholipids in Human Plasma with HPLC–ELSD and LC/ESI–MS After Hydrolysis of Plasma with Phospholipase A1

Ethanolamine ether phospholipid (eEtnGpl) and choline ether phospholipid (eChoGpl) are present in human plasma or serum, but the relative concentration of the ether phospholipids in plasma is very low as compared to those in other tissues. Nowadays, measurement of ether phospholipids in plasma depends on tandem mass spectrometry (LC/MS/MS), but a system for LC/MS/MS is generally too expensive for usual clinical laboratories. Treatment of plasma with phospholipase A₁ (PLA1) causes complete hydrolysis of diacylphospholipids, but ether phospholipids remain intact. After the treatment of plasma with PLA1, both eEtnGpl and eChoGpl are detected as independent peaks by high‐performance liquid chromatography with evaporative light scattering detection (HPLC–ELSD). The same sample used for HPLC–ELSD can be applied to detect eEtnGpl and eChoGpl with electrospray ionization mass spectrometry. Presence of alkylacylphospholipids in both eChoGpl and eEtnGpl in human plasma was indicated by sequential hydrolysis of plasma with PLA1 and hydrochloric acid.     

Multidimensional mass spectrometry methods for the structural characterization of cyclic polymers

Several synthetic methods have been developed for the tailored preparation of cyclic macromolecules due to their unique physical and chemical properties. Unequivocal characterization of the macrocyclic architectures has remained challenging, however, because isomeric linear structures often exist, or the spectral features of linear vs. cyclic chains are similar. To address this problem, multidimensional mass spectrometry (MS) techniques have been evaluated for the separation and identification of polymeric macrocycles. Tandem mass spectrometry (MS²) is found to be ideally suitable for the differentiation of linear and cyclic architectures whose molecular ions exhibit distinct fragmentation characteristics. Conversely, differences in macromolecular sizes and shapes can be exploited to identify the correct architecture by ion mobility mass spectrometry (IM-MS). A third option, chromatographic separation (LC) before MS analysis, is available for the detection of cyclics in complex mixtures. The capabilities of these techniques and combinations thereof are demonstrated with specific covalent or supramolecular (co)polymers.     

Analyzing molecular weight distribution of whey protein hydrolysates

Process parameters on enzymatic hydrolysis and molecular weight (MW) distribution of whey protein hydrolysates were investigated. Whey protein hydrolysates were first gained by the alkaline protease alcalase for 7 h at temperature (50 °C), pH (8.0) and E/S (3%). The diversification of the hydrolysis degree and dissociative amino acid content was investigated during the whey hydrolysis. The dissociative amino acid content was 56.09 μmol/mL with the hydrolysis degree of 20.04%. The results of Sephadex G25 washing and high performance liquid chromatography–electrospray ionization–mass spectrometry (HPLC–ESI–MS) indicated the molecular weight distribution of whey protein hydrolysates ranged from 300 to 1400 Da, and most of whey peptide was under 1000 Da.     

笼型倍半硅氧烷环氧树脂的合成与表征

以3-缩水甘油丙氧基三甲氧基硅烷(GTMS)为原料在异丙醇(IPAP)中水解缩合制成笼型倍半硅氧烷环氧树脂(POSSEP),用红外光谱(FTIR)、~1H-NMR、热重分析(TGA)和液相色谱-质谱联用仪(LC/MS)对其结构进行了表征。LC/MS分析结果表明,合成的笼型倍半硅氧烷环氧树脂以T_(10)为主,另外还含有一定量的T_8以及少量的T_9。热重分析结果表明,笼型倍半硅环氧树脂具有良好的耐热性。在失重5%时的温度为364．5℃,在444．7℃时降解速率最快,800℃以后笼型硅环氧树脂质量基本不变,900℃时的剩余质量为40%。     

Acrylamide in heated potato products – analytics and formation routes

Acrylamide is a highly polar, water‐soluble molecule with low, but significant volatility. Most common methods for determination of acrylamide are high performance liquid chromatography‐tandem mass spectrometry (LC‐MS‐MS), gas chromatography‐mass spectrometry (GC‐MS) after bromination, GC‐MS without and LC‐MS after derivatisation with mercaptobenzoic acid. The different clean‐up procedures used are presented and the advantages and disadvantages of the individual methods are discussed. Acrylamide is formed during food preparation if free asparagine and reducing sugars are present, water activity is low and the product temperature exceeds 100 °C. The influence of different parameters on acrylamide formation in model systems is discussed. In fried potatoes the greatest amount of acrylamide is formed from asparagine and reducing sugars. Alternative routes of formation, as for example via acrolein and acrylic acid are much less important.     

Direct Analysis in Real Time (DART) of an Organothiophosphate at Ultrahigh Resolution by Fourier Transform Ion Cyclotron Resonance Mass Spectrometry and Tandem Mass Spectrometry

Direct analysis in real time (DART) is a recently developed ambient ionization technique for mass spectrometry to enable rapid and sensitive analyses with little or no sample preparation. After swab-based field sampling, the organothiophosphate malathion was analyzed using DART-Fourier transform ion cyclotron resonance (FT-ICR) mass spectrometry (MS) and tandem mass spectrometry (MS/MS). Mass resolution was documented to be over 800,000 in full-scan MS mode and over 1,000,000 for an MS/MS product ion produced by collision-induced dissociation of the protonated analyte. Mass measurement accuracy below 1 ppm was obtained for all DART-generated ions that belonged to the test compound in the mass spectra acquired using only external mass calibration. This high mass measurement accuracy, achievable at present only through FTMS, was required for unequivocal identification of the corresponding molecular formulae.     

Comparison of Liquid Chromatography with Fluorescence Detection and Gas Chromatography/Mass Spectrometry for the Determination of Polycyclic Aromatic Hydrocarbons in Environmental Samples

Liquid chromatography (LC) with fluorescence detection and gas chromatography/mass spectrometry (GC/MS) have been compared for the determination of polycyclic aromatic hydrocarbons (PAHs) in a variety of environmental samples. Three sets of data are presented in this paper in which LC/fluorescence and GC/MS were used for the analysis of the same samples. These three data sets include the comparison of results from: (1) certification measurements for three natural matrix Standard Reference Materials (SRM's), (2) an international round robin for the determination of PAHs in air and diesel particulate samples, and (3) the analysis of four marine sediment reference materials. The results from these studies indicate that the two techniques generally provide comparable results for the measurement of PAHs in environmental samples (in the range of 0.1 to 300 ng/g), with differences in the two techniques between 5–20%. However, at low levels, anthracene and perylene are best measured using LC/fluorescence because of their selective and sensitive fluorescence detection characteristics. In contrast, GC/MS provides more accurate results for the determination of benzo[ghi]perylene because of its low fluorescence sensitivity.     

LC-MS (/MS) in clinical toxicology screening methods

Toxicological screening is the analysis of biological samples to detect and identify unknown compounds. The high selectivity and sensitivity of liquid chromatography (LC) coupled to mass spectrometry (MS) or tandem mass spectrometry (MS/MS) technology provide an attractive alternative to the current methods (LC-UV, GC/MS, etc.). For these reasons, an increasing number of applications are being published. This paper is a brief overview of LC-MS(/MS) screening methods developed for clinical toxicology in recent years. Various sample treatments, chromatographic separations and detection by mass spectrometry can be combined to obtain screening methods adapted to the constraints and needs of clinical toxicology laboratories. Currently the techniques are in the hands of specialists, mainly in academic institutions. However, the evolution in technology should allow application of these techniques as a tool in toxicology laboratories, thus allowing a more widespread exploitation of their potential.     

Lipid methodology — Chromatography and beyond. Part I. GC/MS and LC/MS of glycerolipids

This paper reviews recent examples of the application of combined high temperature gas-liquid chromatography (GLC) and reversed phase high pressure liquid chromatography (HPLC) with electron impact and chemical ionization mass spectrometry for structural studies of natural diacyl and triacylglycerols. It was concluded that the combination of reversed phase HPLC with direct liquid inlet chemical ionization mass spectrometry provides the most complete resolution and most reliable identification of natural acylglycerols, far exceeding the capabilities of either technique alone. The LC/MS method is suitable for quantitative analysis following appropriate calibration of the total or fragment ion response.     

Identification of a TBHQ-Interfering Peak in Crude Canola Oil Using AOCS Official Method Ce 6-86 and its Chromatographic Resolution

AOCS Official Method Ce 6-86 “Antioxidants, Liquid Chromatographic Method” was originally developed to confirm the correct antioxidant was added at the specified concentration to refined oils. Today, this method is increasingly utilized to validate that antioxidants are absent from oil products. False positive results can have a significant impact on the ability to sell products in specific markets and can impart additional business expenditures for conclusive secondary analyses. In the current work, quantification of tert-butylhydroquinone (TBHQ) in crude canola/rapeseed oil using liquid chromatography (LC) with ultraviolet (UV) detection was compromised by an interfering peak. Analyses using liquid chromatography-mass spectrometry (GC–MS) and high-resolution accurate mass LC–MS identified the interferent as 2,6-dimethoxy-4-vinylphenol (canolol), an endogenous compound present in crude canola/rapeseed oil. Resolution of canolol and TBHQ using LC-UV can be achieved via minor modification of the chromatographic conditions.     

Highlights in Coupled Electrochemical Flow Cell-Mass Spectrometry,EC/MS

Probing electrochemical processes by mass spectrometry (EC/MS) is a developing field that benefits from the unmatched identification power of mass spectrometry and from the rapid transfer of electrochemical cell products to the mass spectrometer. Most of the current EC/MS efforts are directed towards the development of differential electrochemical mass spectrometry (DEMS) using the electro-ionization source for identification of volatile compounds, and towards the application of electrospray mass spectrometers for determination of semivolatile and nonvolatile products. The challenges in coupling mass spectrometry and electrochemistry are described, and different approaches to using the coupled system for diverse applications are reviewed, with emphasis on electrospray mass spectrometry. Reaction mechanism studies, diagnostic applications, and activity imaging of electrodes are demonstrated based on approaches that were devised in our laboratory.     

MALDI‐TOF‐CID for the microstructure elucidation of polymeric hydrolysable tannins

High molar mass wood tannin extracts are complex mixtures that are distributed in both molar mass and chemical composition. Hydrolysable tannins from tara, Turkey gall, and chestnut woods were analyzed and compared using matrix‐assisted laser desorption/ionization time‐of‐flight (MALDI‐TOF) mass spectrometry. Although MALDI‐TOF MS reveals the oligomer structure of the tannins, this method cannot distinguish between isomers with isobaric masses and, therefore, ambiguous structural assignments were made in a number of cases. To determine the actual microstructures present, MALDI‐TOF‐CID (collision induced dissociation) experiments were conducted. MALDI‐TOF‐CID enables monomer sequence determination and positive assignments of isobaric structures can be made. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013     

Microstructure elucidation of polyflavonoid tannins by MALDI‐TOF‐CID

High molar mass wood tannin extracts are complex mixtures that are distributed in both molar mass and chemical composition. Condensed tannins from quebracho and mimosa woods were analyzed and compared with cacao tannins using matrix‐assisted laser desorption/ionization‐time of flight (MALDI‐TOF) mass spectrometry. Although MALDI‐TOF MS reveals the oligomer structure of the tannins, this method cannot distinguish between isomers with isobaric masses, and therefore, ambiguous structural assignments were made in a number of cases. To determine the actual microstructures present, MALDI‐TOF collision‐induced dissociation (CID) experiments were conducted. MALDI‐TOF‐CID enables monomer sequence determination, and positive assignments of isobaric structures can be made. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013     

Structural Characterization of Daunomycin-Peptide Conjugates by Various Tandem Mass Spectrometric Techniques

The use of peptide-drug conjugates has generated wide interest as targeted antitumor therapeutics. The anthracycline antibiotic, daunomycin, is a widely used anticancer agent and it is often conjugated to different tumor homing peptides. However, comprehensive analytical characterization of these conjugates via tandem mass spectrometry (MS/MS) is challenging due to the lability of the O-glycosidic bond and the appearance of MS/MS fragment ions with little structural information. Therefore, we aimed to investigate the optimal fragmentation conditions that suppress the prevalent dissociation of the anthracycline drug and provide good sequence coverage. In this study, we comprehensively compared the performance of common fragmentation techniques, such as higher energy collisional dissociation (HCD), electron transfer dissociation (ETD), electron-transfer higher energy collisional dissociation (EThcD) and matrix-assisted laser desorption/ionization–tandem time-of-flight (MALDI-TOF/TOF) activation methods for the structural identification of synthetic daunomycin-peptide conjugates by high-resolution tandem mass spectrometry. Our results showed that peptide backbone fragmentation was inhibited by applying electron-based dissociation methods to conjugates, most possibly due to the “electron predator” effect of the daunomycin. We found that efficient HCD fragmentation was largely influenced by several factors, such as amino acid sequences, charge states and HCD energy. High energy HCD and MALDI-TOF/TOF combined with collision induced dissociation (CID) mode are the methods of choice to unambiguously assign the sequence, localize different conjugation sites and differentiate conjugate isomers.