Mass Spectrometry In Scan Mode Research Articles

Selective and Simultaneous Solid Phase Extraction of Polar and Non–Polar Organophosphorus Pesticides Using Sol–Gel Hybrid Silica–Based Sorbent

A new sol–gel hybrid silica–based sorbent, methyltrimethoxysilane–cyanopropyltriethoxysilane (MTMOS–CNPrTEOS) produced in our laboratory was used for highly selective and simultaneous solid phase extraction (SPE) of two polar organophosphorus pesticides (OPPs) and four non–polar OPPs from water samples. The two polar OPPs used as test analytes are dicrotophos and methamidophos while the four non–polar OPPs are diazinon, malathion, methidathion, and chlorpyrifos. Analysis of OPPs was performed using gas chromatography–mass spectrometry in scan mode. Extraction efficiency (based on peak area response) of the new sol–gel hybrid MTMOS–CNPrTEOS was superior to commercial C18 SPE sorbent. The new sorbent showed higher selectivity towards the polar dicrotophos and methamidophos and it was also able to simultaneously extract the four non–polar OPPs with higher extraction efficiency. The limit of detection at S/N=3 for the new sol–gel hybrid sorbent is 5–9× lower and similar accuracy for the six OPPs compared to commercial C18 SPE sorbent. The new sol–gel hybrid material showed high potential as an alternative sorbent material for solid phase extraction of OPPs of wide polarity. It was successfully applied to the selective and simultaneous extraction the six OPPs from tap water and lake water samples.

Study of the antioxidant mechanisms of Trolox and eugenol with 2,2′-azobis(2-amidinepropane)dihydrochloride using ultra-high performance liquid chromatography coupled with tandem mass spectrometry

The study of antioxidant mechanisms is a difficult task that involves the monitoring and identification of unknown intermediate and final products. Most of the time, the lifetime of intermediates is too short to allow their isolation and subsequent identification by nuclear magnetic resonance (NMR). The developments of ultra-high performance liquid chromatography (UHPLC) coupled with the advances in the acquisition rates of mass spectrometry could facilitate the research on antioxidant mechanisms. This work is based on the reaction involved in the Oxygen Radical Antioxidant Capacity (ORAC) and Total Radical trapping Antioxidant Parameter (TRAP) assays. Hence, the reaction between 2,2'-azobis(2-amidinepropane)dihydrochloride (AAPH) radicals and an antioxidant was carried out in the thermostatized autosampler of a chromatographic device. Then, the reaction media were injected every six minutes, and the compounds were separated by UHPLC and detected by mass spectrometry in scan mode. Nine consecutive injections were registered in a unique file, then the evolution of the reaction for one hour in a single run was monitored. In this way, the reaction mechanisms of Trolox and eugenol with AAPH were studied, leading to the detection of nine and thirteen different compounds, respectively. An exhaustive analysis of the spectra obtained in product ion scan mode led to the identification of the compounds. Most of them were species previously found in the literature, but others have never been reported, so tentative structures were suggested. All this allowed the proposal of several steps within the antioxidant mechanisms of Trolox and eugenol, showing the great performance of UHPLC-MS/MS to complement the use of NMR in antioxidant mechanistic studies.

Quantification of low levels of organochlorine pesticides using small volumes (≤100 μl) of plasma of wild birds through gas chromatography negative chemical ionization mass spectrometry

A solid phase extraction and gas chromatography with negative chemical ionization mass spectrometry in scan mode (GC-NCI-MS) method was developed to identify and quantify for the first time low levels of organochlorine pesticides (OCs) in plasma samples of less than 100 μl from wild birds. The method detection limits ranged from 0.012 to 0.102 pg/μl and the method reporting limit from 0.036 to 0.307 pg/μl for α, γ, β and δ-hexachlorocyclohexane (HCH), heptachlor, aldrin, heptachlor epoxide, endosulfan I, 1,1-dichloro-2,2-bis( p-chlorophenyl)ethylene ( p, p′-DDE), dieldrin, endrin, endosulfan-II, endrin-aldehyde and endosulfan-sulfate. Pesticide levels in small serum samples from individual Falco sparverius, Sturnella neglecta, Mimus polyglottos and Columbina passerina were quantified. Concentrations ranged from not detected (n/d) to 204.9 pg/μl for some OC pesticides. All levels in the food web in and around cultivated areas showed the presence of pesticides notwithstanding the small areas for agriculture existing in the desert of Baja California peninsula.

Construction of the Fingerprints of Ginseng Stem and Leaf Saponin Reference Substances and Spiked Plasma Sample by LC-ESI/MS and Its Application to Analyzing the Compounds Absorbed into Blood after Oral Administration of Ginseng Stem and Leaf Saponin in Rat

Develop a simple and reliable assay method to detect ginseng stem and leaf saponins (GSLS) in methanol and rat plasma by liquid chromatography-electrospray ionization mass spectrometry in scan mode, and construct the fingerprints of GSLS reference substances and plasma samples. In order to screen the active constituents of GSLS, analysis and comparison were carried out between the LC/ESI-MS profiles of blank rat plasma and rat plasma samples obtained after oral administration of GSLS. Thirty-one compounds were detected and 10 of them were identified in the fingerprints of reference substances and spiked plasma sample. Furthermore, 12 compounds (C7, C8, C14, C15, C18, Re, C24, Rb(1), Rc, Rb(2), Rb(3), Rd) were absorbed easily and some new compounds were generated after oral administration of GSLS, which might be the metabolites of GSLS. These absorbed components and new compounds may be the main bioactive components of GSLS.

Development of a harmonised method for the profiling of amphetamines: III. Development of the gas chromatographic method

This study focused on gas chromatographic analysis of target compounds found in illicit amphetamine synthesised by the Leuckart reaction, reductive amination of benzyl methyl ketone, and the nitrostyrene route. The analytical method was investigated and optimised with respect to introduction of amphetamine samples into the gas chromatograph and separation and detection of the target substances. Sample introduction using split and splitless injection was tested at different injector temperatures, and their ability to transfer the target compounds to the GC column was evaluated using cold on column injection as a reference. Taking the results from both techniques into consideration a temperature of 250 °C was considered to be the best compromise. The most efficient separation was achieved with a DB-35MS capillary column (35% diphenyl 65% dimethyl silicone; 30 m × 0.25 mm, d f 0.25 μm) and an oven temperature program that started at 90 °C (1 min) and was increased by 8 °C/min to 300 °C (10 min). Reproducibility, repeatability, linearity, and limits of determination for the flame ionisation detector (FID), nitrogen phosphorous detector (NPD), and mass spectrometry (MS) in scan mode and selected ion monitoring (SIM) mode were evaluated. In addition, selectivity was studied applying FID and MS in both scan and SIM mode. It was found that reproducibility, repeatability, and limits of determination were similar for FID, NPD, and MS in scan mode. Moreover, the linearity was better when applying FID or NPD whereas the selectivity was better when utilising the MS. Finally, the introduction of target compounds to the GC column when applying injection volumes of 0.2 μl, 1 μl, 2 μl, and 4 μl with splitless injection respectively 1 μl with split injection (split ratio, 1:40) were compared. It was demonstrated that splitless injections of 1 μl, 2 μl, and 4 μl could be employed in the developed method, while split injection and splitless injections of 0.2 μl should be avoided.

Development of a capillary gas chromatographic method with flame ionisation detection for the simultaneous determination of sildenafil and itsN-demethylated metabolite in biological fluids

A simple, rapid, and sensitive method has been developed for the analysis of sildenafil (S) and its N-Demethylated metabolite UK-103,320 (UK) using capillary gas chromatography with a flame ionisation detector. Optimal conditions were investigated, achieving analysis times shorter than 12 minutes. Aspects such as stability of the solutions, linearity, accuracy (<91%), precision, specificity, and limits of detection (0.02 mg/L and 0.12 mg/L for S and UK respectively) were tested in order to validate the method. A solid-phase extraction (SPE) prior to the analysis allows quantification of S in serum and urine, and UK in serum at clinically relevant concentrations. Furthermore the specificity has been assessed by means of mass spectrometry in SCAN mode.

Determination of clenbuterol in horse hair by gas chromatography—Tandem mass spectrometry

To investigate drug detection in samples of horse hair from the coat (on the neck), mane, and tail, three clenbuterol studies were conducted on a total of four horses. The analytical procedure consisted in acid hydrolysis of the hair, solid-phase extraction, and quantification by gas chromatography—tandem mass spectrometry in scan mode on an ion-trap instrument. The calibration was linear in the range 4 to 60 pg mg−1. The limit of detection was 1 pg mg−1. The method enabled retrospective analysis-measurement of clenbuterol in the tail was possible for up to 13 months after the last administration of drug.