Negative Atmospheric Pressure Chemical Ionization Research Articles

Negative atmospheric pressure chemical ionisation of NO2 by O2−·CO2·(H2O)n studied by ion mobility spectrometry

Negative atmospheric pressure chemical ionisation of NO2 by O2−·CO2·(H2O)n studied by ion mobility spectrometry

Negative Atmospheric Pressure Chemical Ionization of Chlorinated Hydrocarbons Studied by Ion Mobility Spectrometry (IMS) and IMS-MS Techniques

Negative polarity atmospheric pressure chemical ionization of selected chlorinated hydrocarbons (tetrachloromethane CCl4 and hexachloroethane C2Cl6, dichloromethane CH2Cl2, trichloromethane CHCl3, 1,1,1,2-tetrachloroethane 1,1,1,2-C2H2Cl4, 1,1,2,2-tetrachloroethane 1,1,2,2,-C2H2Cl4 1,1,2-trichloroethane 1,1,2-C2H3Cl3, and 1,1,2-trichloroethane 1,1,2-C2HCl3) was studied using ion mobility spectrometry (IMS) and IMS combined with time-of-flight mass spectrometer (IMS-TOF MS) techniques, in the dry air and at two different drift gas temperatures (323 and 373 K). The ionization was performed using the O2-CO2(H2O)0,1 reactant ions (RIs), and the dominant ionization reaction was the dissociative electron transfer. The ionization resulted in the appearance of Cl- ions for all substances and [O2H..Cl]- ions, which were absent in the case of perchlorinated substances. The quantum-chemical calculations at the density functional theory level of theory using the ωB97X-D/aug-cc-pVTZ method were performed to calculate the thermochemical data (heats of formations, electron affinities, reaction enthalpies) for RIs, neutral substances, neutral fragments, and the anionic fragments. The calculations supported the experimental observations regarding the endothermicity of the Cl- channel for all substances and the exothermicity of the [O2H..Cl]- channel for the tetrachloro- and trichloroethanes.

Oxidation of diethyl ether: Extensive characterization of products formed at low temperature using high resolution mass spectrometry

The oxidation of a stoichiometric diethyl ether-oxygen-nitrogen mixture containing 5000 ppm of fuel was studied in a jet-stirred reactor at 10 atm and a residence times of 1 s. Experimental temperatures varied stepwise for 440 to 740 K and products were quantified by gas chromatography with TCD and FID, gas chromatography-mass spectrometry, and FTIR. Other experiments in the temperature range 480 to 570 K were performed for characterizing elusive cool flame products. To this end, gas samples were trapped in acetonitrile for flow injection analyses and liquid chromatography-mass spectrometry (Orbitrap Q-ExactiveⓇ). For ionization, we used positive and negative atmospheric pressure chemical ionization (APCI). Among fuel-specific products, hydroperoxides and diols (C4H10O3), carbonyl hydroperoxides (C4H8O4), acetic acid, di-keto ethers (C4H6O3), cyclic ethers (C4H8O2) and highly oxygenated molecules, i.e., keto-dihydroperoxides (C4H8O6), keto-trihydroperoxides (C4H8O8), di-keto-hydroperoxides (C4H6O5), and diketo-dihydroperoxides (C4H6O7), were detected. To confirm the presence of –OH or –OOH groups in oxidation products, H/D exchange with D2O was used. DNPH derivatization was used to identify carbonyls present in samples, especially those with a molecular weight below 50 amu which cannot be detected directly by the mass spectrometer. Chemical kinetic modeling using a mechanism taken from the literature was performed. Although reasonable agreement between the data and the simulations was observed for several species, some discrepancies between experimental and computed mole fractions were observed.

Quantitation of ultra-trace nitrated polycyclic aromatic hydrocarbons isomers in water by online solid-phase extraction coupled-liquid chromatography-mass spectrometry

An online solid-phase extraction (SPE)-coupled liquid chromatography-mass spectrometry (LC-MS) method was established for the determination of 10 nitrated polycyclic aromatic hydrocarbons (nitro-PAHs) in water. Water samples were mixed with methanol to generate 40% methanol solutions (v/v), and filtered by 0.45 μm membrane. The filtration with polytetrafluoroethylene(PTFE) membrane got higher recovery rates than nylon membrane, especially for 4-ring and 5-ring nitro-PAHs. 2.5 mL solution was directly injected into online SPE flow path to allow for online purification and enrichment of target analytes in the SPE column. The nitro-PAHs eluted from the SPE column were automatically transferred to the analytical flow path by a well-designed valve-switching system. With the optimization of LC and MS condition, ten nitro-PAH isomers was separated and detected from each other by LC-MS/MS with negative atmospheric pressure chemical ionization (APCI). It was firstly found that nitro-PAHs could produce strong [M-H]− precursor ions in the primary MS besides [M+e]− and [M+15]−. In the secondary MS, the precursor ions mainly lose NO neutral molecule (30 Daltons) to produce daughter ions. The online SPE and LC-MS analysis process was completed in 15.5 min. The linear correlation coefficients of 10 nitro-PAH standard curves were higher than 0.99. The detection limits of nitro-PAHs were about 1.2~22.2 ng/L (S/N=3). The intra-day and inter-day reproducibility (RSD, n=6) were 1.6%~8.4% and 5.3%~16.9%, respectively. The recoveries of 10, 40 and 200 ng/L in tap water were 71.7%~106.4%, 79.7%~100.9% and 73.0%~105.5%, with the corresponding RSD of 2.4%~10.5%, 2.1%~8.6% and 2.7%~6.2%, respectively.

Analysis of four parabens and bisphenols A, F, S in urine, using dilute and shoot and liquid chromatography coupled to mass spectrometry

A new strategy for the analysis of 4 parabens (methylparaben, ethyl paraben, propyl paraben and butyl paraben) and 3 bisphenols (A, F and S) in human urine has been developed. Dilute and shoot and liquid chromatography coupled to mass spectrometry (LC-MS/MS) determination was employed. Procedural matched calibration, certified materials and spiked samples were used for validation. The obtained recoveries varied between 85 and 104% with a precision lower than 20% for all analytes. The LOQ was 0.20 ng mL for all analytes. Negative atmospheric pressure chemical ionization in the selected reaction monitoring mode was used for MS detection. The proposed method was successfully applied for the determination of these compounds in 15 human urine samples from lactating women from the Valencian region (Spain). Methyl paraben (MP) and Bisphenol A (BPA) presented high detection frequency (93% for MP and 80% for BPA), BPS and BPF presented a detection frequency of 33 and 26% respectively. Methyl paraben was detected in a concentration range of 0.2–2952 ng mL−1, 0.2–12 ng mL−1 for bisphenol A, 0.5–39 ng mL−1 for BPF and 0.5–8.5 ng mL−1 for BPS.

Ionization mechanism in gel permeation chromatography mass spectrometry (GPC-MS) with atmospheric pressure chemical ionization (APCI) interface

The ionization mechanism in gel permeation chromatography (GPC) coupled with mass spectrometry (MS) using an atmospheric pressure chemical ionization (APCI) interface is explained when chloroform is used as GPC solvent. The even electron anions [CHCl3+Cl]− generated by thermal electrons in negative APCI mode are responsible for further ionization of the solute compounds as [M + Cl]− adducts. In positive APCI mode, the contaminants in chloroform generate a relatively high background noise. These cations can be suppressed by adding 10% of tetrahydrofuran (THF). Supporting the described mechanism are key experiments done in the absence of solvent, in GPC solvents and using a mixture of anionic polystyrene (PS) standards from dimer up to 12,000 g/mol, covering the molecular masses of great interest in studies related to Registration, Evaluation, Authorization, and Restriction of Chemicals (REACH) and Food and Drug Administration (FDA). Advantages of suppressing the oligomer signals for polymer additive analyses were presented using Irgafos® 168.

Determination of four parabens and bisphenols A, F and S in human breast milk using QuEChERS and liquid chromatography coupled to mass spectrometry

For the first time, a multiresidue, sensitive and high throughput method for determination of bisphenol A, F and S and 4 parabens (methyl paraben, ethyl paraben, propyl paraben and butyl paraben) in human breast milk was developed. The proposed method includes an extraction and clean-up procedure based on QuEChERS methodology followed by liquid chromatography coupled to triple quadrupole mass spectrometry determination. Negative atmospheric pressure chemical ionization in the selected reaction monitoring mode was used for mass detection. During the method validation the recoveries varied between 83 and 115% with a precision lower than 20% for all analytes using spiked levels from 0.1 to 50 ng mL−1. The LOQ was 0.10 ng mL−1 for most of the analytes. The proposed method was successfully applied for the determination of these compounds in 10 breast milk samples from volunteer lactating mothers from the Valencian region (Spain). Among parabens, methyl paraben presented the highest detection frequency (80%) with a concentration range of 0.11–7.00 ng mL−1, while bisphenol A was detected more frequently than BPF and BPS (80% of detection frequency) with concentrations ranging from 0.13 to 1.62 ng mL−1.

Profiling of Hura crepitans L. latex by ultra-high-performance liquid chromatography/atmospheric pressure chemical ionisation linear ion trap Orbitrap mass spectrometry.

The phytochemistry of the latex of Hura crepitans L. (Euphorbiaceae), a widespread tree in the Amazonian forest having many uses, is little known. Only huratoxin, a daphnane diterpene orthoester, has been described despite the high pharmacological potential of this kind of compounds. Glucosphingolipids (cerebrosides) are also known to be distributed in Euphorbiaceae latexes. To tentatively identify daphnanes diterpenes and cerebrosides in the latex of H. crepitans. An ethanolic extract of the lyophilised latex of H. crepitans was analysed by ultra-high-performance liquid chromatography (UHPLC) coupled with positive and negative atmospheric pressure chemical ionisation high-resolution mass spectrometry (APCI-HRMS) method using a quadrupole/linear ion trap/Orbitrap (LTQ-Orbitrap). Tandem mass spectrometry (MS/MS) spectra were recorded by two different fragmentation modes: collision induced dissociation (CID) and higher-energy collisional dissociation (HCD). The analysis of CID- and HCD-MS/MS spectra allowed to propose fragmentation patterns for daphnane esters and cerebrosides and highlight diagnostic ions in positive and negative ion modes. A total of 34 compounds including 24 daphnane esters and 10 cerebrosides have been tentatively annotated. Among them, 17 daphnane diterpenes bearing one or two acyl chains are new compounds and the cerebrosides are described in the genus Hura for the first time. This study revealed the chemical constituents of the latex of H. crepitans and particularly its richness and chemical diversity in daphnane diterpenes, more frequently encountered in the species of Thymelaeaceae.

Medium-Chain Chlorinated Paraffins (CPs) Dominate in Australian Sewage Sludge.

To simultaneously quantify and profile the complex mixture of short-, median-, and long-chain CPs (SCCPs, MCCPs, and LCCPs) in Australian sewage sludge, we applied and further validated a recently developed novel instrumental technique, using quadrupole time-of-flight high resolution mass spectrometry running in the negative atmospheric pressure chemical ionization mode (APCI-qTOF-HRMS). Without using an analytical column the cleaned extracts were directly injected into the qTOF-HRMS followed by quantification of the CPs by a mathematical algorithm. The recoveries of the four SCCP, MCCP and LCCP-spiked sewage sludge samples ranged from 86 to 123%. This APCI-qTOF-HRMS method is a fast and promising technique for routinely measuring SCCPs, MCCPs, and LCCPs in sewage sludge. Australian sewage sludge was dominated by MCCPs with concentrations ranging from 542 to 3645 ng/g dry weight (dw). Lower SCCPs concentrations (<57–1421 ng/g dw) were detected in the Australian sewage sludge, which were comparable with the LCCPs concentrations (116–960 ng/g dw). This is the first time that CPs were reported in Australian sewage sludge. The results of this study gives a first impression on the distribution of the SCCPs, MCCPs, and LCCPs in Australia wastewater treatment plants (WWTPs).

Optimization and application of atmospheric pressure chemical and photoionization hydrogen-deuterium exchange mass spectrometry for speciation of oxygen-containing compounds.

This paper presents a detailed investigation of the feasibility of optimized positive and negative atmospheric pressure chemical ionization (APCI) mass spectrometry (MS) and atmospheric pressure photoionization (APPI) MS coupled to hydrogen-deuterium exchange (HDX) for structural assignment of diverse oxygen-containing compounds. The important parameters for optimization of HDX MS were characterized. The optimized techniques employed in the positive and negative modes showed satisfactory HDX product ions for the model compounds when dichloromethane and toluene were employed as a co-solvent in APCI- and APPI-HDX, respectively. The evaluation of the mass spectra obtained from 38 oxygen-containing compounds demonstrated that the extent of the HDX of the ions was structure-dependent. The combination of information provided by different ionization techniques could be used for better speciation of oxygen-containing compounds. For example, (+) APPI-HDX is sensitive to compounds with alcohol, ketone, or aldehyde substituents, while (-) APPI-HDX is sensitive to compounds with carboxylic functional groups. In addition, the compounds with alcohol can be distinguished from other compounds by the presence of exchanged peaks. The combined information was applied to study chemical compositions of degraded oils. The HDX pattern, double bond equivalent (DBE) distribution, and previously reported oxidation products were combined to predict structures of the compounds produced from oxidation of oil. Overall, this study shows that APCI- and APPI-HDX MS are useful experimental techniques that can be applied for the structural analysis of oxygen-containing compounds.

Regulated bioanalysis of conformers - A case study with ASP2151 in dog plasma and urine.

We developed and validated bioanalytical methods for a potent helicase-primase inhibitor ASP2151 that has two conformers. These conformers elute as unseparated broad peaks under ordinary high-performance liquid chromatographic conditions, indicating discernable differences in hydrophobicity. We observed that column temperature and mobile phase pH have no effect on these peaks and that conformers form a single symmetrical peak when tetrahydrofuran is added to the mobile phase. In addition, we needed to develop semi-automated methods where inter-conversion of the conformers is unlikely to cause sample-to-sample extraction variability. Briefly, following the addition of deuterium-labeled ASP2151 as an internal standard (IS), dog plasma samples or acetonitrile-added urine samples were filtrated. The filtrates were then injected into a column-switching liquid chromatography-tandem mass spectrometry (LC-MS/MS) system and trapped onto an extraction column. Extracts were back-flushed onto an analytical C18 column (4.6×50mm, 3μm) with a mobile phase consisting of methanol, tetrahydrofuran, and 20mmol/L ammonium acetate (45:5:50, v/v/v). The eluent was monitored in the negative atmospheric pressure chemical ionization mode. The calibration curve was linear over a range of 5-1000ng/mL for plasma and 0.5-100μg/mL for urine. Validation data met the acceptance criteria in accordance with regulatory guidance and demonstrated that these methods were selective, accurate, and reproducible. In addition, the present methods were successfully applied to a pharmacokinetic study in dogs.

Exploring the complexity of oil sands process-affected water by high efficiency supercritical fluid chromatography/orbitrap mass spectrometry.

Approximately 1 billion m(3) of oil sands process-affected water (OSPW) is currently stored in tailings ponds in Northern Alberta, Canada. The dissolved organic compounds in OSPW have been termed a supercomplex mixture of bitumen-derived substances and continuing efforts to understand its underlying chemical composition are important for evaluating its environmental hazards. Packed column supercritical fluid chromatography (SFC) was applied to OSPW analysis for the first time. By combining four columns in series (each 25 cm × 4.6 mm I.D., 5.0 µm bare silica) approximately 80,000 plates were achieved on a 1 m column. Using a simple fixed restrictor, the SFC eluent was coupled directly to ultrahigh-resolution orbitrap mass spectrometry (SFC/Orbitrap-MS). SFC/Orbitrap-MS, with positive and negative atmospheric pressure chemical ionization (APCI +/-), revealed the partial or full chromatographic separation of isomers for a wide array of chemical species, including naphthenic acids (Cn H2n + Z O2 ) and unknown sulfur- and nitrogen-containing molecules. For smaller compounds (e.g. naphthenic acids where n ≤10), or for larger structurally constrained compounds (e.g. C16 naphthenic acid with 9 double-bond equivalents), apparent baseline resolution of many isomers was possible. Isomer-specific MS/MS experiments furthermore allowed characterization of functional groups in novel species. For example, in APCI+ mode, up to 16 isomers of C6 H11 ON were revealed to have amide and amino functionalities. This combination of high efficiency chromatography and ultra-high mass resolution detection resulted in a powerful method with capabilities for characterizing or 'fingerprinting' unknown species with little interference. The method has great promise for environmental monitoring and forensics in the oil sands region, as well as for further studies on the composition of dissolved organic compounds in OSPW.

Effect of processing conditions on the content of cis/trans carotene isomers as provitamin A carotenoids in Korean sweet potato varieties

The present investigation intends to evaluate the changes in the content of cis/trans carotene isomers as provitamin A carotenoids by steaming and roasting processes in the roots of four Korean sweet potato varieties viz. Shinzami, Younwhangmi, Chuwhangmi and Jinhongmi using a liquid chromatography with diode array detection and the negative ion atmospheric pressure chemical ionization mass spectrometric (LC-DAD-APCI/MS) method and UV spectral pattern library created from several reference data. Except Shinzami, the content of all trans β-carotenes was found to slightly decreased or remained constant when steamed or roasted. The content of cis α-/β-carotenes was potentially increased about 2-fold or greater when raw or steamed and the content was slightly decreased while roasted. In Chuwhangmi, the content of 13-cis α-carotene and all trans α-carotenes were rapidly increased when steamed and slightly decreased when roasted. Chuwhangmi exhibited 27.2 mg/100 g DW content of all trans β-carotenes when roasted and thus, it was considered as a relatively superior cultivar.

Development and Validation of Liquid Chromatography-Tandem Mass Spectrometry Method for Detection and Quantification of Flunisolide in Tissue Culture Medium

A robust, sensitive, and selective liquid chromatography-tandem mass spectrometry (LC-MS/MS) method capable of quantifying flunisolide in the tissue culture matrix was developed and validated. Both flunisolide and dexamethasone (internal standard) were extracted from tissue culture medium, with 5% fetal bovine serum, 1% nonessential amino acids, and 1% penicillin/streptomycin by simple liquid–liquid extraction. The analytes were chromatographically separated (10 ng/mL for flunisolide) using a C8 column (4.6 mm × 150 mm; 5 µm particle size). The mobile phase was comprised of methanol:water (80:20 v/v). The analytes were separated at baseline within 2.5 min. using a flow rate of 1 mL/min. Mass spectrometry detection was carried out in negative atmospheric pressure chemical ionization mode. The calibration curves for the analyte were linear over the range of 10–200 ng/mL (R2 ≥ 0.9968, n = 6). The inter and intra-batch mean percent accuracy ranged within 97.7–110.6% and the precision range was 3.5–10.4% (% coefficient of variation ≤15%). Stability studies revealed that the analyte was stable in the matrix for at least six hours at room temperature and at the end of three successive freeze and thaw cycles. The method reported here is specific for flunisolide quantification was also used in monolayer efflux assay using CaCo2 cell lines, which will eventually aid P- glycoprotein transport studies for flunisolide.

Separation and Detection of Smokeless Powder Additives by Ultra Performance Liquid Chromatography with Tandem Mass Spectrometry (UPLC/MS/MS),

A reversed phase gradient ultra performance liquid chromatography tandem mass spectrometry (UPLC/MS/MS) method has been developed for the analysis of smokeless powders. A total of 20 different components were separated by UPLC and detected by MS/MS in multiple reaction monitoring (MRM) mode. These compounds included diphenylamines, centralites, nitrotoluenes, nitroglycerin, and various phthalates. Simultaneous positive and negative electrospray ionization (ESI) was used along with negative atmospheric pressure chemical ionization (APCI) to detect all compounds in a single analysis. Analysis times were under 8min with a gradient of 10-73% organic at a flow rate of 0.500mL/min. With this method, ultraviolet and MRM limits of detection ranging from 0.08 to 2.6ng and 0.4-64ng injected were achieved. Commercially available smokeless powders were also extracted with methylene chloride and characterized using the developed UPLC/MS/MS method. The procedure permits the determination of compositional differences between different brands as well as lot-to-lot variations.

Outcompeting GC for the detection of legacy chlorinated pesticides: online-SPE UPLC APCI/MSMS detection of endosulfans at part per trillion levels

Endosulfan, the last remaining organochlorine pesticide, has been the subject of a number of international regulations and restriction/banning action plans worldwide. Occurrence of endosulfan residues in South Florida environments has been widely described in the literature for more than two decades. This work describes a selective, sensitive, and fast online solid-phase extraction (SPE) method coupled with liquid chromatography separation and tandem mass spectrometry (LC-MS/MS) for the determination of endosulfan isomers and endosulfan sulfate in water samples at low part per trillion levels with very little sample preparation. A negative atmospheric pressure chemical ionization source was carefully optimized to produce reproducible spectra of the target compounds with no adduct ion formation. Selected reaction monitoring transitions were monitored and quantitation was performed against a per-deuterated internal standard β-endosulfan (d4). The automated online SPE clean-up was performed using only 20mL of untreated water sample prior to LC-MS/MS analysis. The method was capable of separating and quantifying endosulfan within a 24-min run using acetonitrile and water as mobile phases and presenting statistically calculated method detection limits of 3, 10, and 7ng/L for endosulfan sulfate, α-endosulfan, and β-endosulfan, respectively. In addition, a QuEChERS method was successfully developed and applied for endosulfan determination in sediments/soils, floating and submerged algal mats, and small fish. Minimal matrix effects were observed in all matrices analyzed and recoveries for all analytes ranged from 50-144%. The developed methodology was applied to monitor the occurrence and to assess the potential transport of endosulfan in the Loveland Slough watershed, an area adjacent to Everglades National Park showing long-term contamination with endosulfans.

Analysis of bisphenol A and its chlorinated derivatives in sewage sludge samples. Comparison of the efficiency of three extraction techniques

This paper presents a comparison of three extraction techniques—ultrasound-assisted extraction, microwave-assisted extraction and pressurized liquid extraction—in order to evaluate their efficiency in the determination of bisphenol A and its chlorinated derivatives in sewage sludge samples. Extraction parameters for each technique were accurately optimized to achieve the highest recoveries. The selected compounds were detected and quantified using liquid chromatography–tandem mass spectrometry (LC–MS/MS), operating in negative atmospheric pressure chemical ionization (APCI) and in multiple reaction monitoring (MRM) mode. The analytes were separated in less than 6min. BPA-d16 was used as internal standard. Three selective, sensitive, robust and accurate analytical methods were developed. The limits of detection (LODs) of the methods ranged from 2 to 9ngg−1 and the limits of quantification (LOQs) from 8 to 26ngg−1, while inter- and intra-day variability was under 6% in all cases. Given the absence of certified reference materials (CRMs), the methods were validated separately by using matrix-matched calibration and recovery assays with spiked samples. Recovery rates ranged from 97.7% to 103.1%. The sewage sludge samples used for experiments were collected from two different wastewater treatments plants (WWTPs) located in the province of Granada (South-East Spain). The statistical comparison of the methods demonstrated no statistically significant differences between the extraction techniques for the determination of BPA and chlorinated derivatives in sludge samples.

Selective determination of mono- and dihydroxylated analogs of polybrominated diphenyl ethers in marine sponges by liquid-chromatography tandem mass spectrometry

A number of bioactive brominated secondary metabolites, including hydroxylated polybrominated diphenyl ethers, have been isolated from algae, sponges, and bacteria. In the present study, a screening method using liquid-chromatography tandem mass spectrometry was developed for the identification and selective determination of dihydroxy (diOH), hydroxy-methoxy (OH-MeO), and dimethoxy (diMeO) analogs of tetra- to hexa-BDEs in marine biota. In negative atmospheric pressure chemical ionization (APCI) mode, diOH and OH-MeO analogs provided intense [M-H](-) ions, whereas diMeO analogs provided characteristic [M-Br+O](-) and [M-CH(3)](-) ions. This enabled the diOH-, OH-MeO-, and diMeO-PBDEs to be distinguished using selected reaction monitoring transitions in the APCI source. Recoveries of 2'-OH-6-MeO-2,3',4,5'-tetra-BDE in spiked marine samples were 84 ± 5 %, with a limit of quantification at 9.1 ng mL(-1) (signal-to-noise ratio = 10). The developed method was used to analyze two sponge species collected from Palau, Micronesia; the concentration ratio of diOH-tetra-BDE:OH-MeO-tetra-BDE was 10:1 for the Lamellodysidea sp., whereas it was 1:30 for the Callyspongia sp.

An LC/MS method for d8-β-carotene and d4-retinyl esters: β-carotene absorption and its conversion to vitamin A in humans

The intestinal absorption and metabolism of β-carotene is of vital importance in humans, especially in populations that obtain the majority of their vitamin A from provitamin A carotenoids. MS has provided a better understanding of the absorption of β-carotene, the most potent provitamin A carotenoid, through the use of stable isotopes of β-carotene. We report here an HPLC-MS method that eliminates the need for complicated sample preparation and allows us to detect and quantify newly absorbed d8-β-carotene as well as its d4-retinyl ester metabolites in human plasma and chylomicron fractions. Both retinoids and β-carotene were recovered in a single simple extraction that did not involve saponification, thus allowing subsequent quantitation of individual fatty acyl esters of retinol. Separation of d8-β-carotene and its d4-retinyl ester metabolites was achieved using the same C30 reversed-phase liquid chromatography followed by mass spectrometry in selected ion monitoring and negative atmospheric pressure chemical ionization modes, respectively. Total time for the two successive runs was 30 min. This HPLC-MS method allowed us to quantify the absorption of intact d8-β-carotene as well as its extent of conversion to d4-retinyl esters in humans after consumption of a single 5 mg dose of d8-β-carotene.

HPLC–DAD–MS analysis of dyes identified in textiles from Mount Athos

Organic colorants contained in 30 textiles (16th to early 20th century) from the monastery of Simonos Petra (Mount Athos) have been investigated using high-performance liquid chromatography equipped with diode-array detection and mass spectrometry (HPLC-DAD-MS). The components of natural dyes identified in samples treated by the standard HCl dyestuff extraction method were: alizarin, apigenin, butein, carminic acid, chrysoeriol, dcII, dcIV, dcVII, ellagic acid, emodin, fisetin, flavokermesic acid, fustin, genistein, haematein derivative (Hae'), indigotin, indirubin, isoliquiritigenin, isorhamnetin, kaempferide, kaempferol, kermesic acid, luteolin, naringenin, purpurin, quercetin, rhamnazin, rhamnetin, sulfuretin, and type B and type C compounds (last two are markers for Caesalpinia trees). Early, semi-synthetic dyes, for example indigo carmine, fuchsin components, and rhodamine B were identified in objects dated late 19th to early 20th century. A dyestuff extraction method which involves use of TFA, instead of HCl, was applied to selected historical samples, showing that the mild method enables efficient extraction of weld (Reseda luteola L.) and dyer's broom (Genista tinctoria L.) glycosides. The marker compound (Hae') for logwood (Haematoxylum campechianum L.) identification after treatment with HCl was investigated by liquid chromatography coupled to mass spectrometry (LC-MS) in negative electrospray ionization (LC-MS-ESI(-)) mode. LC-MS in negative atmospheric pressure chemical ionization (LC-MS-APCI(-)) mode was used, probably for the first time, to investigate cochineal (Dactylopius coccus Costa) samples. Positive electrospray ionization (LC-MS-ESI(+)) mode was used for identification of fuchsin components. Detailed HPLC-DAD studies were performed on young fustic (Cotinus coggygria Scop.) and Persian berries (Rhamnus trees).