Chemical Ionization-ion Trap Mass Spectrometry Research Articles

Removal and degradation of sodium diclofenac via radical-based mechanisms using S. sclerotiorum laccase

The recently isolated Sclerotinia sclerotiorum laccase was used for the degradation of sodium diclofenac, a nonsteroidal anti-inflammatory drug widely found in the aquatic environment. The Michaelis-Menten parameters, half-life of diclofenac at different pH values in presence of this enzyme and potential inhibitors were evaluated. Diclofenac-based radicals formed in presence of laccase were spin-trapped and detected using EPR spectroscopy. Almost complete diclofenac degradation (> 96%) occurred after a 30-h treatment via radical-based generated oligomers and their rapid precipitation, thus ensuring an unprecedented green formula suitable not only for degradation but also for straightforward removal of the degradation products. High performance liquid chromatography coupled with atmospheric pressure chemical ionization-ion trap mass spectrometry (HPLC-APCI-MS) analyses of the degradation products of diclofenac in aqueous dosage revealed the presence of at least seven products while HR Orbitrap MS analysis showed that the enzymatic treatment produced high molecular weight metabolites through a radical oligomerization mechanism of diclofenac. The enzymatically formed products precipitated and its constituting components were also characterized using UV–vis spectroscopy, infrared spectroscopy (FTIR) and thermogravimetric analysis (TGA).

LC-PDA/APCIitMS identification of algal carotenoid and oxysterol precursors to fatty acid esters in hydrolyzed extracts of the freshwater mussel Dreissena bugensis

Carotenyl fatty acid esters (carotenyl-FAEs) were extracted in acetone from freeze-dried Dreissena bugensis (Lakes Erie and Ontario) and hydrolyzed to identify the carotenoid precursors. Analysis by liquid chromatography (LC) with photodiode array (PDA) and atmospheric pressure chemical ionization-ion trap mass spectrometry (APCIitMS) revealed the major hydrolysis products: fucoxanthinol (FOH) from fucoxanthin (FX, diatoms); mactraxanthin (MX) from violaxanthin (VX, chlorophytes); 4-fold higher levels of an unknown, tentatively identified as an adduct of two closely eluting C27H46O3 and C27H48O3 steryl triols. Enzymatic hydrolysis (Candida rugosa) of dreissenid extracts yielded FOH and MX, but residual carotenyl-FAEs remained. Alkaline hydrolysis yielded isoFOH, MX, and steryl triols, without residual carotenyl-FAEs: isoFOH decreased, but two FOH hemiketal by-products increased, when the dose of potassium hydroxide in methanol was too high. The PDA detector profiled carotenyl-FAEs and products of enzymatic and alkaline hydrolysis, without interference. The APCIitMS detector revealed carotenoid and oxysterol products of alkaline hydrolysis but was adversely affected by background from bile salts used for enzymatic hydrolysis. LC retention times and elution order were correlated to solubility parameters, calculated from the analyte structure, to cross-check MS interpretations. A multiple linear regression of LC retention times on solubility parameters for 12 carotenoid standards included FOH, isoFOH, and MX (r 2 0.97). The model revealed the close similarity of polar carotenoid metabolites to C27-steryl triols tentatively identified by APCIitMS, suggesting that further LC-MS analyses would be beneficial, to explicitly link oxysterols and the polar carotenoids, as metabolites of algal precursors in the dreissenid diet. Graphical abstract Methods of analysis and major neutral products of hydrolysis from fatty acid esters in D. bugensis.

Identification and quantification of oxidized organic aerosol compounds using derivatization, liquid chromatography, and chemical ionization mass spectrometry

ABSTRACTA systematic approach for identifying and quantifying molecular components of complex organic aerosol mixtures is presented. The approach combines methods developed previously for derivatizing carbonyl, hydroxyl, carboxyl, and ester functional groups, which are commonly present in oxidized organic aerosol, with liquid chromatography, UV detection, and chemical ionization-ion trap mass spectrometry. The original derivatization-spectrophotometric methods were modified for compatibility with liquid chromatography and then evaluated by analyzing a variety of standard compounds that contain one or more functional groups. Detection limits for carbonyl, hydroxyl, carboxyl, and ester analysis are approximately 0.003, 0.02, 0.01, and 1 nmole, respectively. Mass spectral analysis of derivatives using isobutane and ammonia as reagent gases for chemical ionization can be used to determine compound molecular weight, and characteristic fragmentation patterns provide structural information for use in compound id...

Determination of phytosterols in oenological matrices by liquid chromatography-atmospheric pressure chemical ionization and ion-trap mass spectrometry

The aim of the present study is the identification of plant sterols and the development of an analytical method that allows for the quantification of such family of compounds in oenological matrices. The application of liquid chromatography-atmospheric pressure chemical ionization ion-trap mass spectrometry (LC-APCI-ITMS) to sterol characterization is a useful tool and was selected to perform this research. Sterol separation was achieved using a C8 column with a mobile phase consisting of water and acetonitrile under gradient conditions and column temperature of 35°C, which leads to analyte elution in less than 25min. Retention times, precursor ions and MRM transitions of analytes allowed for the identification and sensitive quantitative determination of phytosterols in oenological matrices at trace levels. The method showed a dynamic linear range over the concentration ranges from 0.02 to 320mgkg−1 for the different parts of grapes and from 8 to 100ngmL−1 in case of wine. The most abundant phytosterol in all samples was β-sitosterol. The seeds are the richest source of phytosterols having a great amount of β-sitosterol, 314mgkg−1 fresh berry mass, followed by stigmasterol, fucosterol and campesterol at much lower concentrations (ranging from 3 to 10mgkg−1).

Secondary processes in atmospheric pressure chemical ionization-ion trap mass spectrometry: a case study of orotic acid

Atmospheric pressure chemical ionization is known for producing unusual artifacts of the ionization process in some cases. In this work, processes occuring in atmospheric pressure chemical ionization/MS of orotic acid that afforded ions accompanying protonated and deprotonated orotic acid molecules in the spectra were studied. Two processes ran in parallel in the ion source: decarboxylation of neutral orotic acid and collision-induced dissociation of its protonated or deprotonated form. A procedure discerning pre-ionization decomposition and post-ionization dissociation by manipulating ion source parameters was proposed. Experiments with isotopically labeled solvents confirmed ion-molecule reactions of the product of collision-induced dissociation of protonated orotic acid with solvent molecules in the ion source and even under vacuum in the ion trap.

Multi-component analysis (sterols, tocopherols and triterpenic dialcohols) of the unsaponifiable fraction of vegetable oils by liquid chromatography–atmospheric pressure chemical ionization–ion trap mass spectrometry

A simple and sensitive method for the analysis of sterols, tocopherols and triterpenic dialcohols from the unsaponifiable fraction from oil samples in a single analytical run using liquid chromatography coupled to mass spectrometry was developed. With this method, the compounds could be detected directly after dissolving the unsaponifiable fraction in acetonitrile without necessity of time-consuming sample pre-treatment or derivatization. Separation of the analytes was carried out at room temperature, by using a C18 column (5 μm i.d. 3.0 mm × 250 mm) with a linear gradient of acetonitrile/water (0.01% acetic acid) at a flow rate of 1.5 mL/min. The full scan mass spectra of the investigated compounds were measured by an ion trap mass spectrometer equipped with an APCI ion source. The optimized methodology was suitable for the identification of 23 compounds belonging to different families present in olive oil and other kinds of oils, as well as for the quantification of 15 analytes (vs. their commercial standards).

The Postmortem Distribution of Vardenafil (Levitra®) in an Aviation Accident Victim with an Unusually High Blood Concentration*

Vardenafil (Levitra) is one of the most widely prescribed treatments for erectile dysfunction. This report presents a rapid and reliable method for the identification and quantification of vardenafil in postmortem fluids and tissues, applies this method to a postmortem case, and describes the distribution of vardenafil in various fluids and tissues. This procedure utilizes sildenafil-d8, which is structurally closely related to vardenafil, as an internal standard for more accurate and reliable quantitation. The method incorporates solid-phase extraction and liquid chromatography-tandem mass spectrometry (MS) and MS-MS-MS utilizing an atmospheric pressure chemical ionization ion trap MS in the positive chemical ionization mode. Solid-phase extraction proved to be exceptionally efficient providing recoveries that ranged from 94% to 97%. The limit of detection for vardenafil was determined to be 0.19 ng/mL. The linear dynamic range for this compound was 0.39-200 ng/mL. This method was successfully applied to postmortem fluid and tissue specimens obtained from an aviation accident victim. The distribution of vardenafil in various fluids and tissues and the unusually high concentration of vardenafil in the victim's blood are examined.

Use of liquid chromatography–atmospheric pressure chemical ionization‐ion trap mass spectrometry for identification of oleanolic acid and ursolic acid in Anoectochilus roxburghii (wall.) Lindl

Oleanolic acid (OA) and ursolic acid (UA) are the two important bioactive compounds in Anoectochilus roxburghii (wall) Lindl (A. roxburghii), which has been used as a traditional Chinese medicine. So far, there has been no report to indicate that A. roxburghii contains these two bioactive compounds. It is necessary to develop an effective method to extract and analyze OA and UA in A. roxburghii. In this paper, a quantitative method, consisting of supercritical fluid extraction (SFE) followed by liquid chromatography-atmospheric pressure chemical ionization-ion trap mass spectrometry (LC-APCI-IT-MS) analysis, was developed for identification of OA and UA in A. roxburghii. The extraction was carried out by using CO(2) as the supercritical fluid and ethanol as the modifier before LC separation. The mobile phase used for LC separation consisted of acetic acid (1%, v/v), water (15%, v/v) and methanol (84%, v/v), and the elution was performed at a flow rate of 0.8 ml/min. The mass spectrometer was operated in APCI(+) mode with selected ion monitoring (SIM) to quantify OA and UA at m/z 439.4. Under optimum conditions, the linear responses of OA and UA were obtained in the concentration range of 0.5-80 (r = 0.9992) and 0.5-50 microg/ml (r = 0.9989) with the detection limits of 0.125 and 0.085 microg/ml, respectively. The proposed method has been used for the identification and quantitation of OA and UA in a real A. roxburghii sample.

Comparison of the Structures of Triacylglycerols from Native and Transgenic Medium‐Chain Fatty Acid‐Enriched Rape Seed Oil by Liquid Chromatography–Atmospheric Pressure Chemical Ionization Ion‐Trap Mass Spectrometry (LC–APCI‐ITMS)

The sn position of fatty acids in seed oil lipids affects physiological function in pharmaceutical and dietary applications. In this study the composition of acyl-chain substituents in the sn positions of glycerol backbones in triacylglycerols (TAG) have been compared. TAG from native and transgenic medium-chain fatty acid-enriched rape seed oil were analyzed by reversed-phase high performance liquid chromatography coupled with online atmospheric-pressure chemical ionization ion-trap mass spectrometry. The transformation of summer rape with thioesterase and 3-ketoacyl-[ACP]-synthase genes of Cuphea lanceolata led to increased expression of 1.5% (w/w) caprylic acid (8:0), 6.7% (w/w) capric acid (10:0), 0.9% (w/w) lauric acid (12:0), and 0.2% (w/w) myristic acid (14:0). In contrast, linoleic (18:2n6) and alpha-linolenic acid (18:3n3) levels decreased compared with the original seed oil. The TAG sn position distribution of fatty acids was also modified. The original oil included eleven unique TAG species whereas the transgenic oil contained sixty. Twenty species were common to both oils. The transgenic oil included trioctadecenoyl-glycerol (18:1/18:1/18:1) and trioctadecatrienoyl-glycerol (18:3/18:3/18:3) whereas the native oil included only the latter. The transgenic TAG were dominated by combinations of caprylic, capric, lauric, myrisitic, palmitic (16:0), stearic (18:0), oleic (18:1n9), linoleic, arachidic (20:0), behenic (22:0), and lignoceric acids (24:0), which accounted for 52% of the total fat. In the original TAG palmitic, stearic, oleic, and linoleic acids accounted for 50% of the total fat. Medium-chain triacylglycerols with capric and lauric acids combined with stearic, oleic, linoleic, alpha-linolenic, arachidic, and gondoic acids (20:1n9) accounted for 25% of the transgenic oil. The medium-chain fatty acids were mainly integrated into the sn-1/3 position combined with the essential linoleic and alpha-linolenic acids at the sn-2 position. Eight species contained caprylic, capric, and lauric acids in the sn-2 position. The appearance of new TAG in the transgenic oil illustrates the extensive effect of genetic modification on fat metabolism by transformed plants and offers interesting possibilities for improved enteral applications.

Multiple-stage mass spectrometric analysis of six pesticides in oranges by liquid chromatography–atmospheric pressure chemical ionization–ion trap mass spectrometry

Six pesticides were determined by liquid chromatography (LC) with positive ion (PI) atmospheric pressure chemical ionization quadrupole ion-trap tandem mass spectrometry (APCI–MS–MS). Ion fragmentation was studied by MS, MS 2 and MS 3. Fragmentation of the pesticides produced ions formed by various losses from the side-chains and through heterocyclic ring opening, but without any common fragmentation pathway. Multiple reaction monitoring (MRM) of MS, MS 2 and MS 3 was used to identify and quantify the pesticides. The samples were extracted with ethyl acetate and dried over anhydrous sodium sulfate. Comparison of the three MS modes showed that MS 3 is slightly less sensitive but much more selective. Recoveries from oranges were 72–94% at the limit of quantification (LOQ) level for all MS modes. The LOQs were 0.001–0.3 mg kg −1 quantifying by means of the MS 3 product ion. The method was used to analyse a number of orange samples. This is the first report on using MS 3 product ions for quantification of pesticide residues.

Stability studies of propoxur herbicide in environmental water samples by liquid chromatography–atmospheric pressure chemical ionization ion-trap mass spectrometry

Liquid chromatography–atmospheric pressure ionization ion-trap mass spectrometry has been investigated for the analysis of polar pesticides in water. The degradation behavior of propoxur, selected as a model pesticide belonging to the N-methylcarbamate group, in various aqueous matrices (Milli-Q water, drinking water, rain water, seawater and river water) was investigated. Two interfaces of atmospheric pressure ionization, atmospheric pressure chemical ionization (APCI) and electrospray ionization (ESI), were compared during the study. Propoxur and its transformation product ( N-methylformamide) were best ionized as positive ions with both APCI and ESI, while another transformation product (2-isopropoxyphenol) yielded stronger signals as negative ions only with APCI. In addition, the effects of various pH, matrix type and irradiation sources (sunlight, darkness, indoor lighting and artificial UV lamp) on the chemical degradation (hydrolysis) were also assessed. From the kinetic studies of degradation, it was found that the half-life of propoxur was reduced from 327 to 161 h in Milli-Q water with variation of irradiation conditions from dark to sunlight exposure. Degradation rates largely increased with increasing pH. The half-life of the target compound dissolved in Milli-Q water under darkness decreased from 407 to 3 h when the pH of Milli-Q water was increased from 5 to 8.5. These suggest that hydrolysis of propoxur is light-intensity and pH-dependent. In order to mimic contaminated natural environmental waters, propoxur was spiked into real water samples at 30 μg/l. The degradation of propoxur in such water samples under various conditions were studied in detail and compared. With the ion trap run in a time-scheduled single ion monitoring mode, typical limits of detection of the instrument were in the range of 1–10 μg/l.

Determination of the double bond position in functionalized monoenes by chemical ionization ion-trap mass spectrometry using acetonitrile as a reagent gas

Acetonitrile may be used as a chemical ionization reagent gas in ion-trap mass spectrometry for the location of double bonds in functionalized long-chain monoenes. [C3H4N]+, derived from acetonitrile, reacts with carbon–carbon double bonds, generating one or a pair of fragment ions characteristic of the position of the double bond in the chain. Tolerance of a range of functional groups is achieved by isolating [C3H4N]+ from the other acetonitrile ions before reaction with the alkene. Under these conditions, competing processes such as protonation are minimized, and a different mode of fragmentation from that previously observed with unfunctionalized alkenes11 is obtained. The technique is highly sensitive (<0.5 ng), allowing its use in the identification of insect pheromones. Copyright © 1999 John Wiley & Sons, Ltd.

Rapid target analysis of microcontaminants in water by on-line single-short-column liquid chromatography combined with atmospheric pressure chemical ionization ion-trap mass spectrometry

The applicability of trace enrichment and separation of microcontaminants on a single 10×2 mm I.D. high-pressure-packed liquid chromatography (LC) column, combined on-line with an atmospheric pressure chemical ionization (APCI)–ion-trap tandem mass spectrometry (MS–MS) instrument was studied for the target analysis of herbicides in river water. The total analysis time was 15–20 min. With the on-line short-column LC–MS–MS method, detection limits of 0.1–1 μg/l can be achieved using only 4 ml of river water. However, the results obtained for a mixture of six triazines were considerably better than those for a mixture of eight phenylureas. An attempt is made to explain this difference on the basis of various processes that occur within the ion trap and the measurement procedure itself.