1,720,996 research outputs found
Occurrence of specific environmental risk factors in brain tissues of sudden infant death and sudden intrauterine unexpected death victims assessed with gas chromatography–tandem mass spectrometry
No full textAtmospheric Pressure Vaporization Mechanism for Coupling a Liquid Phase with Electron Ionization Mass Spectrometry
No full textA novel liquid chromatography-mass spectrometry (LC-MS) interfacing concept is presented and discussed. The new interface, called Liquid-EI (LEI), is based on electron ionization (EI) but, differently from any previous attempt, the vaporization of solutes and mobile phase takes place at atmospheric pressure into a specifically designed region, called “vaporization micro-channel”, before entering the high-vacuum ion source. The interface is completely independent from the rest of the instrumentation, and can be adapted to any gas chromatography-mass spectrometry (GC-MS) system, as an add-on for a rapid LC-MS conversion. Pressure drop and temperature gradient between LC and MS were considered to enhance the analyte response and reduce band broadening and/or solute carryovers. A fused silica liner, placed inside the vaporization micro-channel, acts as an inert vaporization surface speeding up the gas-phase conversion of large molecules while lessening possible memory effects. The liner is easily replaceable for a quick and extremely simple interface maintenance. Proof of concept and detailed description of the interface are here presented
The Rapid Measurement of Benzodiazepines in a Milk-Based Alcoholic Beverage Using QuEChERS Extraction and GC–MS Analysis
Full text linkBenzodiazepines (BDZs) are widely used as tranquilizers and antidepressive
drugs in common clinical practice. However, their ready
availability and their synergistic effects with alcohol make them
attractive for criminal intentions. To prove criminal action for legal
reasons, it is often necessary to analyze beverage residues from a
crime scene. Milk-based alcoholic drinks (whiskey creams) are gaining
popularity due to their lower alcohol content pleasant taste.
However, the complexity of this sample, containing proteins and
fatty acids, can mask the presence of drugs or other substances in
standard analysis methods. These characteristics make whiskey
creams highly suitable for illicit purposes. In this study, eight BDZs,
including diazepam, chlordiazepoxide, clobazam, flunitrazepam, bromazepam,
flurazepam, nitrazepam and clonazepam, were extracted
from whiskey cream using the Quick, Easy, Cheap, Effective,
Rugged and Safe (QuEChERS) method and analyzed using GC–MS.
The QuEChERS protocol can efficiently separate most of the matrix
from the target compounds while maintaining acceptable recoveries.
The presented method is simple and rapid and has been validated in
terms of precision, accuracy and recoveries. Limits of detection and
limits of quantitationwere in the range of 0.02–0.1 and 0.1–0.5 mg/mL,
respectively. Whiskey cream beverages, fortified with commercial
drugs at 20 mg/mL, were extracted and analyzed demonstrating the
applicability of the method in forensic analysis
Liquid chromatography-electron ionization tandem mass spectrometry with the Direct-EI interface in the fast determination of diazepam and flunitrazepam in alcoholic beverages
Full text linkThis is the first application based on electron ionization (EI) using a Direct-EI LC interface and MS/MS to detect unequivocally target compounds in a very small real sample. The determination and quantification of benzodiazepines (BDZ) in very small residues of beverages, collected at the scene of drug-facilitated crimes (DFC) are mandatory in legal procedures. A specific and sensitive analytical instrumentation is needed, involving little or no sample preparation. Here, a direct flow injection analysis (FIA) of alcoholic beverages spiked with commercially available drugs containing diazepam and flunitrazepam is presented. The method proposed is very fast and requires neither sample preparation nor chromatographic separation. Linearity (R(2) ) was between 0.9977 and 0.9992; LOD and LOQ spanned from 0.01 to 0.02 ng/μL and from 0.1 to 0.5 ng/μL, respectively; intra- and inter-day repeatabilities were between 1 and 8%. No matrix effects (ME) were observed from the comparison of the linear regression curves obtained in real fortified samples and in pure ethanol. Vodka, whisky and white wine specimens were fortified with commercial drugs, Valium(®) and Rohypnol(®) , at two different concentrations (20 and 50 ng/μL) to simulate the typical amounts found in adulterated real samples and analyzed to demonstrate the method applicability to forensic analyses. This article is protected by copyright. All rights reserved
Boosting the Detection Potential of Liquid Chromatography-Electron Ionization Mass Spectrometry Using a Ceramic Coated Ion Source
Full text linkDetection of target and non-target substances and their characterization in complex samples is a challenging task. Here we demonstrate that coating the electron ionization (EI) ion source of an LC-MS system with a sol-gel ceramic film can drastically improve the detection of high-molecular weight and high-boiling analytes. A new ion source coated with a ceramic material was developed and tested with a mixture of polycyclic aromatic hydrocarbons (PAH) with an increasing number of rings. Comparison of the results obtained with those for an uncoated stainless steel (SS) ion source shows a dramatic improvement in the MS signals, with a nearly 40-fold increase of the signal-to-noise ratio. We also demonstrate the ability of the new system to produce excellent chromatographic profiles for hard-to-detect hormones
A new liquid chromatography–mass spectrometry approach for generic screening and quantitation of potential genotoxic alkylation compounds without derivatization
No full textOne of the crucial tasks of pharmaceutical industry is to quantify the potential genotoxic impurities (PGIs)
coming from the process of drug production. The European Medicines Agency (EMEA) imposes analytical
testing limits in the order of g/g, depending on drug dosage and exposure period, that means the need of
a sensitive and selective method of analysis. Liquid chromatography coupled to electrospray ionization
mass spectrometry (LC–ESI-MS) has been demonstrated as the most versatile approach to detect PGIs in
complex matrices. However, time consuming derivatization processes are needed to enhance sensitivity
and selectivity, and to overcome matrix effects (ME) that may arise from active pharmaceutical ingredients
(APIs) or excipients. We propose the use of the Direct-EI LC–MS as an alternative approach to detect
and quantify PGIs in drug formulations. The Direct-EI LC–MS interface is based on electron ionization (EI)
which is well suited for the detection of low molecular weight compounds of different polarity, without
derivatization and with no sign of ME. The method has been successfully applied to the detection of PGIs
belonging to the class of alkylation agents. Calibration experiments show satisfactory linearity and precision
data. Recoveries in low enriched samples spanned from 55 to 82%, and were not affected by ME. The
method limits of detection (LODs), varying from 0.13 to 1.5 g/g, were satisfactory for the quantitation
of the target PGIs at the level required by regulatory agencies
The history of electron ionization in LC-MS, from the early days to modern technologies: A review
Full text linkThis review article traces the history of the use of liquid chromatography coupled with mass spectrometry (LC-MS) using electron ionization (EI) from the first attempts up to the present day. At the time of the first efforts to couple LC to MS, 70 eV EI was the most common ionization technique, typically used in gas chromatography-mass spectrometry (GC-MS) and providing highly reproducible mass spectra that could be collated in libraries. Therefore, it was obvious to transport this dominant approach to the early LC-MS coupling attempts. The use of LC coupled to EI-MS is challenging mainly due to restrictions related to high-vacuum and high-temperature conditions required for the operation of EI and the need to remove the eluent carrying the analyte before entering the ion source. The authors will take readers through a journey of about 50 years, showing how through the succession of different attempts it has been possible to successfully couple LC with EI-MS, which in principle appear to be incompatible
Single-Step LC/MS Method for the Simultaneous Determination of GC-Amenable Organochlorine and LC-Amenable Phenoxy Acidic Pesticides.
No full textWater pollution by organochlorine pesticides (OCPs) is considered as an analytical challenge, since these persistent and nonbiodegradable pollutants are not amenable by liquid chromatography coupled to atmospheric pressure ionization mass spectrometry (LC/API-MS). This represents a significant constraint in multiresidue analysis of real samples, when high polar, poorly volatile compounds are present as well. This paper reports the development of an innovative single-step method for the simultaneous determination of OCPs and polar pesticides belonging to the class of phenoxy acids in water samples. The method is based on an off-line solid-phase extraction (SPE) procedure with Carbograph 4 followed by liquid chromatography coupled to a direct electron ionization mass spectrometer (LC/direct-EI-MS). The direct-EI capability of acquiring high-quality EI spectra and operation in selected ion monitoring mode allowed a precise quantification of OCPs and phenoxy acids in a single chromatographic run without derivatization. The instrumental response was characterized by excellent sensitivity, linearity, and precision. The SPE recovery rates in river water gave values equal or better than 80% for most of the compounds. The method limits of detection (LODs) span from 0.002 to 0.052 μg/L, allowing the detection of the selected pesticides at the limits required by the European Union (EU) legislation for drinking water
Rapid LC-MS method for the detection of common frangrances in personal care products without sample preparation
No full textAn LC-MS method for the analysis of personal care and household products without sample
preparation is presented. The method takes advantage of the Direct-electron ionization
(EI) LC-MS interface for the quantitation of principal components, as well as for the identification
of unknown or undeclared ingredients. The technique has proven its inertness
toward matrix effects and the electron ionization allows quantitation and library identification.
Commercially available products (shower gel, perfume, and hand cream) were
diluted with methanol and injected directly into a nano-LC column. Limonene, linalool,
and citral were selected as target compounds because of their use as fragrances in toiletry
and detergent products. These and all other fragrances are commonly determined with
GC-MS analysis, prior to sample cleanup, a procedure that can lead to analytes loss. The
selected compounds are not detected with ESI because of their poor or very low response.
Figures of merit and validation studies were executed and special attention was devoted
to matrix-effects evaluation, because a sample preparation procedure is not involved. No
matrix effects were observed, and the repeatability was excellent even after several weeks
of operation. Products composition was investigated in full scan mode to determine the
presence of unknown or not listed ingredients
Profiling of non-esterified fatty acids in human plasma using liquid chromatography-electron ionization mass spectrometry
No full textThis paper focuses on the development of a
novel approach to analyze underivatized fatty acids in
human plasma. The method is based on liquid–liquid
extraction followed by reversed phase liquid chromatography
coupled to direct-electron ionization mass spectrometry
(LC-Direct-EI-MS). The assay is validated. Calibrations
show satisfactory linearity and precision in the investigated
range of linearity. Recoveries span from 75% to 104%. The
method limits of detection, varying from 0.53 to 5.35 μM,
are satisfactory for the quantitation of non-esterified fatty
acids (NEFAs) in plasma at physiological levels. The
method has been successfully applied to the NEFAs
profiling of plasma samples from healthy adult volunteers
and subjects affected by diabetes mellitus. Compared with
published protocols based on gas chromatography–mass
spectrometry and liquid chromatography coupled to electrospray
ionization mass spectrometry, this method does not
require derivatization and does not show matrix effects,
thus simplifying sample preparation procedure and reducing
the total time of analysis to approximately 90 min. In
addition, Direct-EI-MS allows the acquisition of highquality
NIST library-matchable EI spectra, allowing an
easy-to-obtain identification of the target NEFAs
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