On-line Atmospheric Pressure Chemical Ionization Research Articles

Dual-Sensitive Probe of 2-(Benzoacridin)ethyl-imidazole-1-carboxylate for Determination of Aliphatic Amine with Fluorescence and Online Atmospheric Pressure Chemical Ionization Mass Spectrometry Identification

Dual-Sensitive Probe of 2-(Benzoacridin)ethyl-imidazole-1-carboxylate for Determination of Aliphatic Amine with Fluorescence and Online Atmospheric Pressure Chemical Ionization Mass Spectrometry Identification

Dual-Sensitive Probe of 2-(Benzoacridin)ethyl-imidazole-1-carboxylate for Determination of Aliphatic Amine with Fluorescence and Online Atmospheric Pressure Chemical Ionization Mass Spectrometry Identification

Using three different derivatization methods to mark the amine compounds, we compared the difference of derivatization efficiency and gave the optimal method. 5-(2-Hydroxyethyl)benzoacridine reacts with coupling agent N,N′-carbonyldiimidazole (CDI) to form an activated amide intermediate 2-(benzoacridin)ethyl-imidazole-1-carboxylate (BAEIC). BAEIC, which is dual-sensitive probe, reacts preferably with amino compounds at 80 °C in the presence of 4-dimethylaminopyridine (DMAP) catalyst in N,N-dimethylformamide (DMF) solvent to give the corresponding sensitively fluorescent derivatives with an excitation maximum at 280 nm of λex and an emission maximum at 510 nm of λem. BAEIC-amine derivatives simultaneously exhibited high-ionization potential with percent ionization δ changing from 5.62% to 58.08% in aqueous acetonitrile and from 2.14% to 56.58% in aqueous methanol. Derivatives are not only sensitive to fluorescence but also to MS ionizable potential. The fluorescence detection limits are 0.12–0.59 ng mL？1 (at a signal-to-noise ratio of 3). The online Atmospheric Pressure Chemical Ionization Mass Spectrometry (APCI-MS) detection limits are 1.89–14.12 ng mL？1 (at a signal-to-noise ratio of 5).

Effect of Preparation Conditions on Release of Selected Volatiles in Tea Headspace

The release of volatile compounds from infused tea was monitored using on-line atmospheric pressure chemical ionization (APCI) mass spectrometry. Assignment of the APCI ions to particular compounds was achieved using gas chromatography of tea headspace with dual electron ionization and APCI-MS detectors. Six ions in the APCI spectrum could be assigned to individual compounds, five ions were associated with isobaric compounds (e.g., 2- and 3-methylbutanal and pentanal) or stereoisomers (e.g., heptenals or heptadienals), and a further four ions monitored were identified compounds but with some unknown impurities. Reproducibility of infusion preparation and the analytical system was good with percentage variation values generally below 5%. The analysis was used to study the effect of infusion and holding temperatures on the volatile profile of tea headspace samples, and this was found to be compound-dependent. Both the extraction of volatiles from leaf tea and the release of volatiles into the headspace play a role in creating the aroma profile that the consumer experiences.

Continuous Real-Time Analysis of Products from the Reaction of Some Monoterpenes with Ozone Using Atmospheric Sampling Glow Discharge Ionization Coupled to a Quadrupole Ion Trap Mass Spectrometer

An on-line technique has been demonstrated for the analysis of photochemical oxidation reaction products. The technique is based on the direct introduction of gas and particulate oxidation products into a custom-built atmospheric sampling glow discharge ionization source (ASGDI) coupled to a quadrupole ion trap mass spectrometer (QITMS). Operational parameters of the ASGDI system were investigated to determine their influence on the ion signal for the analysis of oxidation products in real time. These parameters include the discharge current, ion accumulation time, and type of reagent gas. Reference mass spectra from standards were generated for a variety of biogenic compounds and terpene reaction products containing keto, hydroxy, aldehyde, carboxylic acid, or epoxy groups to better understand the fragmentation that occurs in the glow discharge ion source. Results are presented for ozonolysis reactions of four biogenic monoterpenes (alpha-pinene, beta-pinene, D-limonene, Delta(3)-carene) monitored with the ASGDI quadrupole ion trap to demonstrate the ability to obtain real-time measurements. The reaction products identified with ASGDI-QITMS correspond to those products identified with other techniques, including on-line atmospheric pressure chemical ionization techniques. Efficient differentiation of multifunctional products including mono-/di-/hydroxy-/keto-carboxylic acid and keto-/hydroxy-aldehyde was possible by use of the MS/MS capability of the instrument.

On-line characterization of gaseous and particulate organic analytes using atmospheric pressure chemical ionization mass spectrometry

A modified atmospheric pressure chemical ionization ion source is applied for direct analysis of volatile or low volatile organic compounds in air. The method is based on the direct introduction of the analytes in the gas phase and/or particle phase into the ion source of a commercial ion-trap mass spectrometer. Two methods are employed for the production of primary ions at atmospheric pressure, photoionization and corona discharge. It is shown that in the presence of a dopant, photoionization can be a highly efficient ionization method also for real-time analysis with detection limits for selected analytes in the lower ppt-range. Using corona discharge for the production of primary ions, which is instrumentally easier since no additional chemicals have to be added to the sample flow, we demonstrate the analytical potential of on-line atmospheric pressure chemical ionization mass spectrometry for reaction monitoring experiments. To do so, an atmospherically relevant gas phase reaction is carried out in a 500 l reaction chamber and gaseous and particulate compounds are monitored in the positive and negative ion mode of the mass spectrometer.

Iodine oxide homogeneous nucleation: An explanation for coastal new particle production

A series of laboratory experiments on the chemical composition of aerosol particles formed after photodissociation of CH2I2, a major volatile alkyl halide released from macroalgae, have been performed in a laboratory scale reaction chamber using on‐line atmospheric pressure chemical ionization mass spectrometry (APCI/MS). Based on the mass spectrometric results and the molecular properties of iodine oxides, we suggest that the self‐nucleation of iodine oxides provides an efficient source of natural condensable material in coastal environments and discuss this concept focusing on OIO as one potential key species for new particle formation. The presented hypothesis not only fits the measured enrichment of iodine species in submicrometer particles, but also can explain the frequently observed nucleation bursts in the coastal boundary layer.

Supercritical fluid extraction of nylon 6,6 oligomers and their characterization via liquid chromatography coupled with mass spectrometry

This research extends previous studies regarding the application of supercritical fluid extraction (SFE) for the analysis of oligomers from nylon 6,6 fibers. The effects of CO 2 pressure, extraction temperature, CO 2-modifier percentage, static extraction time and dynamic extraction time on the SFE efficiency of nylon 6,6 oligomers were examined. Results from the SFE methods for oligomer extractions were compared to results from conventional solvent extraction. The extracted oligomers were identified by high-performance liquid chromatography (HPLC) with coupled on-line atmospheric pressure chemical ionization mass spectrometry and HPLC fractionation coupled with off-line liquid secondary ion mass spectrometry.

HPLC/atmospheric pressure chemical ionization-mass spectroscopy of eight regulated sulfonamides

Reversed phase high performance liquid chromatography coupled with on-line atmospheric pressure chemical ionization mass spectrometry, HPLC/APCI-MS, has been applied to a mixture of eight sulfonamides. In full scan mode, extracted ion chromatograms produced minimum detectable quantities (MDQ) of 0.8 ng on column, for six of the eight regulated sulfonamides investigated. Selected ion monitoring yielded a 50 pg MDQ for sulfamerazine, sulfadiazine and sulfamethazine, while, the other compounds presented higher values. Analysis of supercritical fluid extracts of chicken liver containing sulfadimethoxine were found to be easily detected by HPLC/APCI-MS. In extracts of chicken liver spiked with 25 μg kg −1 (25 ppb) of sulfadimethoxine this compound could be detected in selected ion mode, while 100 pg μl −1 was detectable in either full scan or single ion modes. The analysis method for extracted sulfadimethoxine also demonstrated good linearity and reproducibility in both single ion and scan mode.

FUNGAL METABOLISM OF NITROFLUORANTHENES

Metabolism of 2-nitrofluoranthene (2-NFA), one of the most abundant and genotoxic environmental pollutants in air, and of a mixture of 2-nitrofluoranthene and 3-nitrofluoranthene (3-NFA) was studied using (1) the fungus Cunninghamella elegans ATCC 36112 and (2) rat liver microsomes. The fungal metabolites were separated by reversedphase high-performance liquid chromatography ( HPLC) and identified by 1H nuclear magnetic resonance ( NMR) spectrometry, ultraviolet (UV)-visible spectroscopy, and online atmospheric-pressure chemical ionization/ mass spectrometry ( APCI/MS) . The fungus metabolized 82% of 2-nitro-\\[3H]-fluoranthene to 2-nitrofluoranthene 8-sulfate and 2-nitrofluoranthene 9-sulfate. Metabolism of a mixture of 2- and 3-nitrofluoranthene by C. elegans similarly produced 2-nitrofluoranthene 8- and 9-sulfate and 3-nitrofluoranthene 8- and 9-sulfate as major metabolites. In addition, a glucoside conjugate of 3- hydroxy-2-nitrofluoranthene was tentatively identified by APCI/MS analysis. When rat liver microsomes were incubated with a mixture of 2- and 3-nitrofluoranthene for 1 h, in addition to the trans -7,8- and 9,10-dihydrodiols reported previously for 2-nitrofluoranthene, several novel metabolites were produced including 2-nitrofluoranthene trans -4,5- dihydrodiol and 2-nitrofluoranthene trans -8,9-dihydrodiol, the trans -4,5-dihydrodiol of 3-nitrofluoranthene, and phenolic products of both 2- and 3-nitrofluoranthene. The fungal metabolism of the 2- and 3-nitrofluoranthene mixture was similar to the metabolism of individual nitrofluoranthenes; however, the mammalian metabolism of the nitrofluoranthene mixture showed differences in regioselectivity at positions C4, C5, C8, and C9.

Determination of Steroids by Liquid Chromatography/Mass Spectrometry

On-line atmospheric pressure chemical ionization (APCI) and electrospray ionization (ESI) liquid chromatography/mass spectrometry (LC/MS) were evaluated for the analysis of a variety of steroids. Steroids were classified into three major groups based on the spectra and the sensitivities observed: (I) those containing a 3-one, 4-ene functional group, (II) those containing at least one ketone group without conjugation, and (III) those containing hydroxy group(s) only. In the APCI mode, the best sensitivity and the lowest detection limit for all three groups were obtained by using a mobile phase consisting of methanol and 1%–2% acetic acid in water. The APCI spectra were characterized by MH +, MH +-H 2O, MH +-2H 2O, etc., with the degree of H 2O loss being compound dependent: group I steroids produced stable MH + and group III steroids showed extensive water loss. In the electrospray mode the best sensitivity and the lowest detection limit for the first two groups were obtained when pure methanol and water were used as the mobile phase. This condition produced abundant stable MNa + due to ubiquitous sodium. Detection limits in the 5–15 pg range can be easily achieved using ESI LC/MS. Addition of ammonium acetate or use of acetonitrile in the mobile phase, common in the LC/MS analysis of steroids, decreased the sensitivity for the group I and II steroids and thus should be avoided. For group III steroids, the detection limit can be improved by the addition of acetic acid to the mobile phase.