Determination of acetone in seawater using derivatization solid-phase microextraction

Acetone plays an important role in the chemistry of both the atmosphere and the ocean, due to its potential effect on the tropospheric HO_x (= HO + HO₂) budget, as well as its environmental and health effects. We discuss the development of a mobile, sensitive, selective, economical and facile method for the determination of acetone in seawater. The method consists of derivatizing acetone to its pentafluorobenzyl oxime using 1,2,3,4,5-pentafluorobenzylhydroxylamine (PFBHA), followed by solid-phase microextraction (SPME) and analysis by gas chromatography/mass spectrometry (GC/MS). A detection limit of 3.0 nM was achieved. The buffering capacity of seawater imposes challenges in using the method’s optimum pH (3.7) on seawater samples, requiring calibration standards to be made in buffered salt water and the acidification of seawater samples and standards prior to extraction. We employed the technique for analysis of selected surface seawater samples taken on the Nordic seas during the ARK-XX/1 cruise (R.V. Polarstern). An upper limit of 5.5–9.6 nM was observed for acetone in these waters, the first acetone measurements reported for far North Atlantic and Arctic waters. Simplified schematic of transformations of organic compounds at the atmosphere–ocean interface     

Determination of oxygenated volatile organic compounds in ambient air using canister collection-gas chromatography/mass spectrometry.

This research attempts to establish a method to measure 11 kinds of oxygenated volatile organic compound (OVOC) in ambient air by using the canister collection-gas chromatography/mass spectrometry (GC/MS) method. Since several compounds such as acetone exhibited high blank concentrations due to their laboratory use, stringent quality control was conducted for the VOC-free added water and the VOC-free nitrogen gas. In order to prevent the decline of recovery rates due to lack of sufficient relative humidity, it is necessary to add VOC-free water when pressurizing and diluting the air samples. Thus, all the target compounds in ambient air were obtained from the canisters at high recovery rates without significant contamination. Furthermore, the canister collection-GC/MS method makes it possible to apply simultaneous air monitoring of OVOCs as well as volatile hazardous air pollutants without additional sampling.     

GC-MS analysis of ethanol and other volatile compounds in micro-volume blood samples—quantifying neonatal exposure

A static headspace gas chromatography coupled mass spectrometry (GC-MS) method was developed and fully validated for the quantitative measurement of acetaldehyde, acetone, methanol, ethanol and acetic acid in the headspace of micro-volumes of blood using n-propanol as an internal standard. The linearity of the method was established over the range 0.2–100 mg/L (R ²?>?0.99) and the limits of detection were 0.1–0.2 mg/L and lower limits quantification 0.5–1 mg/L. Precision and accuracies fell within acceptable limits (20 % for LLOQ and 15 %) for both intra- and inter-day analyses for all compounds except acetaldehyde which had inter-day variability of ≤25 %. The method was applied to analyse blood samples from neonatal patients receiving courses of ethanol excipient containing medications. Baseline levels of acetaldehyde, acetone, methanol and ethanol could be measured in patients before dosing commenced and an increase in levels of some volatiles were observed in several neonates after receiving ethanol-containing medications.     

Interaction of acetone, hydroxyacetone, acetaldehyde and benzaldehyde with the surface of water ice and HNO3·3H2O ice

Oxygenated volatile organic compounds (OVOCs) influence the oxidative properties of the atmosphere, and their transport from the ground may occur by scavenging by the HNO(3)-rich supercooled water droplets found in polluted convective air masses. With infrared spectroscopy, we have studied the interactions of four typical atmospheric OVOCs (acetone, hydroxyacetone, acetaldehyde and benzaldehyde) with model surfaces of water ice and of trihydrated nitric acid (NAT) ice. We show that these molecules weakly adsorb on water ice and NAT by hydrogen bonding. No chemical reaction occurs between the molecules and the NAT substrate, the OVOCs remaining intact when in contact with hydrated HNO(3) in atmospheric ice clouds.     

Selected ion flow tube mass spectrometry of exhaled breath condensate headspace

Collection of exhaled breath condensate (EBC) is a relatively simple noninvasive method of breath analysis; however, no data have been reported that would relate concentration of volatile compounds in EBC to their gaseous concentrations in exhaled air. The aim of the study was to investigate which volatile compounds are present in EBC and how their concentrations relate to results of direct breath analysis. Thus, samples of EBC were collected in a standard way from several subjects and absolute levels of several common volatile breath metabolites (ammonia, acetone, ethanol, methanol, propanol, isoprene, hydrogen cyanide, formaldehyde and acetaldehyde) were then determined in their headspace using selected ion flow tube mass spectrometry (SIFT-MS). Results are compared with those from on-line breath analyses carried out immediately before collecting the EBC samples. It has been demonstrated that SIFT-MS can be used to quantify the concentrations of volatiles in EBC samples and that, for methanol, ammonia, ethanol and acetone, the EBC concentrations correlate with the direct breath levels. However, the EBC concentrations of isoprene, formaldehyde, acetaldehyde, hydrogen cyanide and propanol do not correlate with direct breath measurements. Copyright (c) 2008 John Wiley & Sons, Ltd.     

Monosaccharide compositional analysis of marine polysaccharides by hydrophilic interaction liquid chromatography-tandem mass spectrometry

A simple and sensitive method was developed using hydrophilic interaction liquid chromatography coupled to tandem mass spectrometry for determination of monosaccharides liberated from marine polysaccharides by acidic hydrolysis. Optimal separation of diastereomeric monosaccharides including hexoses, pentoses, and deoxyhexoses was achieved using an aminopropyl bonded column with mobile phase containing ternary solvents (acetonitrile/methanol/water) in conjunction with MS/MS in SRM mode. Mechanisms for fragmentation of deprotonated monosaccharides with regard to cross-ring cleavage were proposed. Matrix effects from coeluting interferences were observed and isotopic-labeled internal standard was used to compensate for the signal suppression. The method demonstrated excellent instrumental limits of detection (LOD), ranging from 0.7 to 4.2 pg. Method LODs range from 0.9 to 5.1 nM. The proposed method was applied to the analysis of polysaccharides in seawater collected from the open leads of the central Arctic Ocean in the summer of 2008.     

Determination of acetaldehyde in tobacco smoke using N-methyl-4-hydrazino-7-nitrobenzofurazan and liquid chromatography/mass spectrometry

A liquid chromatography/mass spectrometry (LC/MS) method for the determination of carbonyl compounds based on derivatization with N-methyl-4-hydrazino-7-nitrobenzofurazan (MNBDH) has been developed. Atmospheric pressure chemical ionization (APCI) in the positive mode proved the most versatile ionization technique for MNBD-hydrazones. APCI/MS spectra were recorded and the detection limits were determined for [M+H]+, 13C2 acetaldehyde MNBD-hydrazone has been synthesized and characterized. It is applied as internal standard for the quantification of acetaldehyde. Tobacco smoke has been investigated concerning its carbonyl content. Acetaldehyde was identified as main product and quantified by LC/MS using internal standardization. The result is in good agreement to quantification data obtained with UV/vis detection.     

MALDI‐FT‐ICR‐MS for archaeological lipid residue analysis

Soft‐ionization methods are currently at the forefront of developing novel methods for analysing degraded archaeological organic residues. Here, we present little‐used soft ionization method of matrix assisted laser desorption/ionization‐Fourier transform‐ion cyclotron resonance‐mass spectrometry (MALDI‐FT‐ICR‐MS) for the identification of archaeological lipid residues. It is a high‐resolution and sensitive method with low limits of detection capable of identifying lipid compounds in small concentrations, thus providing a highly potential new technique for the analysis of degraded lipid components. A thorough methodology development for analysing cooked and degraded food remains from ceramic vessels was carried out, and the most efficient sample preparation protocol is described. The identified components, also controlled by independent parallel analysis by gas chromatography‐mass spectrometry (GC‐MS) and gas chromatography‐combustion‐isotope ratio mass spectrometry (GC‐C‐IRMS), demonstrate its capability of identifying very different food residues including dairy, adipose fats as well as lipids of aquatic origin. The results obtained from experimentally cooked and original archaeological samples prove the suitability of MALDI‐FT‐ICR‐MS for analysing archaeological organic residues. Sample preparation protocol and identification of compounds provide future reference for analysing various aged and degraded lipid residues in different organic and mineral matrices.     

Analysis of low molecular mass organic acids in natural waters by ion exclusion chromatography tandem mass spectrometry

A sensitive and selective method for the analysis of aliphatic low molecular mass organic acids (LMMOAs) in natural waters is presented. The method is based on separation with ion exclusion chromatography and detection with electrospray ionization tandem mass spectrometry (LC-MS/MS). The extra selectivity gained by applying MS/MS allows for a minimum of sample preparation and the use of a sub-optimal mobile phase regarding chromatographic resolution. Instead the mobile phase, comprising aqueous formic acid with methanol as organic modifier, was mainly optimized for maximum sensitivity and long term MS stability. Detection limits for malonic, fumaric, maleic, succinic, citraconic, glutaric, malic, alpha-ketoglutaric, tartaric, shikimic, trans-aconitic, cis-aconitic, isocitric and citric acid were in the range 1-50 nM, while the detection limits for pyruvic, oxalic and lactic acid were around 250 nM for an injection volume of 100 microL. Due to their metal-chelating properties, these LMMOAs are all considered to affect the bioavailability of metals and to be involved in soil forming processes. It is thus of interest to be able to monitor their presence in natural waters, and the method developed within this work was successfully applied for the analysis of LMMOAs in soil solution and stream water samples.     

Analysis of cypermethrin residues and its main degradation products in soil and formulation samples by gas chromatography-electron impact-mass spectrometry in the selective ion monitoring mode

A fast, simple and inexpensive sample preparation method based on the matrix solid-phase extraction (SPE) technique is proposed for the isolation of cypermethrin and its metabolite residues from soils. Both the extraction and clean-up procedures were carried out in two steps and target compounds were determined by gas chromatography coupled with electron-impact mass spectrometry (GC-EI/MS). The characteristic ions and fragmentation mechanism of cypermethrin were evaluated by electron impact ionization mass spectrometry (EI/MS). After the optimization of different parameters, such as the extraction solvent, the pesticide was extracted from the matrix with methanol/acetone in a Soxhlet extractor, cleaned up on a Florisil column by elution with a mixture of 30% ethyl acetate in n-hexane and analyzed by gas chromatography-electron impact ionization mass spectrometry (GC-EI/MS) in the selected ion-monitoring mode (SIM) with permethrin as internal standard. Recovery was in the range 77–118% with relative standard deviations (RSD) between 2.5% and 10.2%. The limit of detection (LOD) was 6.5?µg/kg for cypermethrin. The developed method was linear in the injection range 6–30?ng, with correlation coefficients greater than 0.9957.     

Extraction and purification procedures for simultaneous quantification of phenolic xenoestrogens and steroid estrogens in river sediment by gas chromatography/ion trap mass spectrometry

A sensitive and simple method based on ultrasonication extraction with a hexane/acetone (2:1, v/v) mixture, followed by clean up of the extract by solid-phase extraction (SPE) and gas chromatography/mass spectrometry (GC/MS) detection, has been developed and validated for the analysis of 20 estrogenic endocrine-disrupting chemicals (EEDCs) including phenolic xenoestrogens, synthetic and natural estrogens in river sediment. After extraction and purification, analytes are derivatised with a BSTFA/TMCS/pyridine (49:1:50, v/v/v) mixture and quantified by GC/MS. The GC/MS method involves switching between electron ionisation (EI) and chemical ionisation (CI); it also switches between selected ion storage and tandem mass spectrometry detection. The applicability of the method has been demonstrated by analysing extracts of French river sediments for which bioanalytical tests (in vitro) had already shown that they were impacted by estrogenic endocrine disrupters. The biological contribution of all the products detected in each sediment extract was compared to the estrogenic activity measured by bioassays.     

Determination of acetaldehyde in tobacco smoke using N-methyl-4-hydrazino-7-nitrobenzofurazan and liquid chromatography/mass spectrometry

A liquid chromatography/mass spectrometry (LC/MS) method for the determination of carbonyl compounds based on derivatization with N-methyl-4-hydrazino-7-nitrobenzofurazan (MNBDH) has been developed. Atmospheric pressure chemical ionization (APCI) in the positive mode proved the most versatile ionization technique for MNBD-hydrazones. APCI/MS spectra were recorded and the detection limits were determined for [M+H]⁺. ¹³C₂ acetaldehyde MNBD-hydrazone has been synthesized and characterized. It is applied as internal standard for the quantification of acetaldehyde. Tobacco smoke has been investigated concerning its carbonyl content. Acetaldehyde was identified as main product and quantified by LC/MS using internal standardization. The result is in good agreement to quantification data obtained with UV/vis detection.     

Assessment of acetone as an alternative to acetonitrile in peptide analysis by liquid chromatography/mass spectrometry

Acetonitrile as a solvent used in liquid chromatography/mass spectrometry (LC/MS) of peptides and proteins is a relatively toxic solvent (LD₅₀ oral; rat; 2,460 mg/kg) compared to alternatives like methanol (LD₅₀ oral; rat; 5,628 mg/kg) and acetone (LD₅₀ oral; rat; 5,800 mg/kg). Strategies to minimize its consumption in LC are either to reduce the inner diameter of the column or replace acetonitrile with a suitable alternative. Methanol is often recommended to replace acetonitrile in peptide analysis. In this study however, the main focus lies on another alternative solvent for LC/MS of peptides; acetone. A number of model proteins were tryptically digested and the peptide solutions were analyzed on a linear trap quadrupole (LTQ) mass spectrometer. The performances of acetonitrile, methanol and acetone were compared according to the quality of the chromatograms obtained and identification of the peptides using the BioWorks? software developed by Thermo Scientific. In accordance to the elutropic series, acetone was found to significantly reduce the retention times of peptides separated by C18 column material with regard to acetonitrile while methanol led to increased retention times. Acetone was the superior solvent to methanol for most of the tested model proteins reaching similar sequence coverage and numbers of identified peptides as acetonitrile. We therefore propose acetone as an alternative to acetonitrile in LC/MS of peptides. Copyright © 2009 John Wiley & Sons, Ltd.     

A simple and robust LC-MS/MS method for quantification of free 3-nitrotyrosine in human plasma from patients receiving on-pump CABG surgery

We have developed a simple, sensitive, and robust liquid chromatography-mass spectrometry/mass spectrometry (LC-MS/MS) method to determine free 3-nitrotyrosine concentrations in human plasma of patients receiving on-pump coronary artery bypass grafting surgery. A one-step solid-phase extraction protocol was optimized to enrich the analyte at low nanomolar concentrations. The processed samples were analyzed by LC-MS/MS with a 2.1 × 100 mm Kinetex PFP column and a triple quadrupole mass spectrometer. The method was validated for 3-nitrotyrosine concentrations close to real patient plasma levels. The relative standard deviations or relative errors of the intraday and interday determinations were all within 10%. Limit of detection and limit of quantitation were determined to be 0.034 nM and 0.112 nM, respectively, while lower limit of quantitation was below 0.625 nM. No deterioration of the column performance was noticed after running a large number of patient samples. The results showed that the 3-nitrotyrosine concentrations in coronary sinus plasma samples were elevated after cardiopulmonary bypass (CPB) procedure. The pre-CPB and post-CPB concentrations of 3-nitrotyrosine in patient plasmas were 1.494 ± 0.107 nM and 2.167 ± 0.177 nM (mean ± SEM), respectively. Application of this method to more patients in clinical studies may help validate 3-nitrotyrosine as a meaningful biomarker for nitrosative stress and link patient characteristics, clinical outcomes, and cardioprotective treatments to endogenous nitrosative stress levels.     

Quantitative determination of acetylcholine in microdialysis samples using liquid chromatography/atmospheric pressure spray ionization mass spectrometry

A fast, simple and sensitive liquid chromatography/tandem mass spectrometry (LC/MS/MS) method was developed for the determination of acetylcholine in rat brain microdialysis samples. The chromatographic separation was achieved in 3 min on a reversed-phase column with isocratic conditions using a mobile phase containing 2% (v/v) of acetonitrile and 0.05% (v/v) of trifluoroacetic acid (TFA). A stable isotope-labeled internal standard was included in the analysis and detection was carried out with a linear ion trap mass spectrometer using selected reaction monitoring (SRM). Analyte ionization was performed with an atmospheric pressure chemical ionization (APCI) source without applying discharge current (atmospheric pressure spray ionization). This special ionization technique offered significant advantages over electrospray ionization for the analysis of acetylcholine with reversed-phase ion-pairing chromatography. The lower limit of quantification was 0.15 nM (1.5 fmol on-column) and linearity was maintained over the range of 0.15-73 nM, providing a concentration range that is significantly wider than that of the existing LC/MS methods. Good accuracy and precision were obtained for concentrations within the standard curve range. The method was validated and has been used extensively for the determination of acetylcholine in rat brain microdialysis samples.     

Ion–molecule reactions of methoxymethyl cations with some organic substrates studied by ion cyclotron resonance spectrometry

The reactions of methoxymethyl cations generated from dimethyl ether with propene, butene-2, vinyl methyl ether, acetaldehyde and acetone have been studied. The collision complexes, generated with the olefines, may eliminate an olefine, a methanol and a formaldehyde molecule as shown by double resonance experiments. From deuterium labelling it is found, that in the cases of propene and butene-2 the elimination of an olefine is accompanied by an extensive H/D interchange in the collision complexes, which has been shown not to occur in the long-lived reactant methoxymethyl cations if the internal energy of the methoxymethyl cations is less than 2.3 eV. The H/D interchange in these collision complexes is reduced in the elimination of methanol and is almost completely suppressed in the elimination of formaldehyde. In reactions with vinyl methyl ether, however, the eliminations of methanol and formaldehyde from the corresponding collision complexes appear to proceed with extensive H/D interchange. These observations point to acyclic collision complexes rather than 4-membered ring complexes. The collision complexes generated with acetaldehyde and acetone decompose by elimination of formaldehyde only. Deuterium labelling has shown that the formaldehyde molecule contains the original methylene group of the reactant methoxymethyl cations. In addition, ¹⁸O labelling in acetone has shown that the original oxygen atom of the methoxymethyl cations is retained completely in the eliminated formaldehyde. These observations exclude any formation of 4-membered ring collision complexes and can only be explained by acyclic complexes. Possible mechanisms of all reactions mentioned are discussed in the light of these results.     

Validated Method to Determine Quetiapine and Norquetiapine in Microsomal Matrix by LC MS–MS: Implication in Quetiapine Metabolism

A sensitive and selective LC–MS/MS method for the quantification of the atypical antipsychotic agent quetiapine and its metabolite norquetiapine (N-desalkyl quetiapine) was developed and validated. Following the protein precipitation technique, the analytes were separated using a reversed phase column with gradient elution. The compounds were ionized in the electrospray positive ionization (ESI+) ion source tandem MS detection in multiple reaction monitoring (MRM) mode. Calibration curves were generated by plotting the peak area ratio of quetiapine and norquetiapine to the IS clozapine for each calibration concentration. The method provides a linear response from a quantitation range of 2.3–452.9 nM (0.9–173.7 ng/mL) and 2.7–543.0 nM (1.0–200.0 ng/mL) for quetiapine and norquetiapine, respectively. Regression analysis showed a correlation coefficient greater than 0.999 and 0.991 for quetiapine and norquetiapine, respectively. To evaluate the metabolism of quetiapine by the cytochrome P450 in microsomes, the method has been subsequently employed. LC–MS/MS procedure has been carried out to determine increasing concentrations of both drugs in microsomal matrix obtained by a pool of mammalian liver microsomes BD UltraPool^TM Human Liver Microsomes (HLM 150).     

Optimization of solid-phase extraction and liquid chromatography–tandem mass spectrometry for the determination of domoic acid in seawater,phytoplankton, and mammalian fluids and tissues

We previously reported a solid-phase extraction (SPE) method for determination of the neurotoxin domoic acid (DA) in both seawater and phytoplankton by liquid chromatography–tandem mass spectrometry (LC–MS/MS) with the purpose of sample desalting without DA pre-concentration. In the present study, we optimized the SPE procedure with seawater and phytoplankton samples directly acidified with aqueous formic acid without addition of organic solvents, which allowed sample desalting and also 20-fold pre-concentration of DA in seawater and phytoplankton samples. In order to reduce MS contamination, a diverter valve was installed between LC and MS to send the LC eluant to waste, except for the 6-min elution window bracketing the DA retention time, which was sent to the MS. Reduction of the MS turbo gas temperature also helped to maintain the long-term stability of MS signal. Recoveries exceeded 90% for the DA-negative seawater and the DA-positive cultured phytoplankton samples spiked with DA. The SPE method for DA extraction and sample clean-up in seawater was extended to mammalian fluids and tissues with modification in order to accommodate the fluid samples with limited available volumes and the tissue extracts in aqueous methanol. Recoveries of DA from DA-exposed laboratory mammalian samples (amniotic fluid, cerebrospinal fluid, plasma, placenta, and brain) were above 85%. Recoveries of DA from samples (urine, feces, intestinal contents, and gastric contents) collected from field stranded marine mammals showed large variations and were affected by the sample status. The optimized SPE–LC–MS method allows determination of DA at trace levels (low pg mL⁻¹) in seawater with/without the presence of phytoplankton. The application of SPE clean-up to mammalian fluids and tissue extracts greatly reduced the LC column degradation and MS contamination, which allowed routine screening of marine mammalian samples for confirmation of DA exposure and determination of fluid and tissue DA concentrations in experimental laboratory animals.     

Analysis of anabolic steroids in hair by GC/MS/MS

A simple and sensitive gas chromatography/tandem mass spectrometry (GC/MS/MS) method is described for the detection of anabolic steroids, usually found in keratin matrix at very low concentrations. Hair samples from seven athletes who spontaneously reported their abuse of anabolic steroids, and in a single case cocaine, were analyzed for methyltestosterone, nandrolone, boldenone, fluoxymesterolone, cocaine and its metabolite benzoylecgonine. Anabolic steroids were determinate by digestion of hair samples in 1 m NaOH for 15 min at 95 degrees C. After cooling, samples were purificated by solid-phase and liquid-liquid extraction, then anabolic steroids were converted to their trimethylsilyl derivative and finally analyzed by GC/MS/MS. For detection of cocaine and benzoylecgonine, hair samples were extracted with methanol in an ultrasonic bath for 2 h at 56 degrees C then overnight in a thermostatic bath at the same temperature. After the incubation, methanol was evaporated to dryness, and benzoylecgonine was converted to its trimethylsilyl derivative prior of GC/MS/MS analysis. Results obtained are in agreement with the athletes' reports, confirming that hair is a valid biological matrix to establish long-term intake of drugs.     

Determination of ofloxacin, norfloxacin, and ciprofloxacin in sewage by selective solid-phase extraction, liquid chromatography with fluorescence detection, and liquid chromatography--tandem mass spectrometry

A solid-phase extraction (SPE) and liquid chromatographic (LC) method was developed for the determination of selected fluoroquinolone (FQ) drugs including ofloxacin, norfloxacin, and ciprofloxacin in municipal wastewater samples. Extraction of the FQs was carried out with a weak cation exchanger SPE cartridge, the Oasis WCX. The cartridge was washed with water and methanol as a cleanup before the FQs were eluted by a mixture of methanol, acetonitrile, and formic acid. Separation of the FQs was achieved by using a Zorbax SB-C8 column under isocratic condition at a flow rate of 0.2mL/min. Recoveries of the FQs in spiked final effluent samples were between 87 and 94% with a relative standard deviation of less than 6%. Several techniques have been evaluated for the detection of FQs in sewage extracts; they included fluorescence detection and electrospray ionization (ESI) mass spectrometry using either mass-selective detection or tandem mass spectrometry (MS/MS). When they were applied to sewage influent and effluent samples, the LC-MS/MS technique operating in the multiple reaction monitoring (MRM) mode proved to be best suited for the determination of FQs in sewage samples as it provided the highest sensitivity (limit of quantification 5ng/L) and selectivity. The observation of signal suppression (matrix effect) for some FQs in ESI LC-MS and LC-MS/MS is discussed and a solution is proposed. The three FQs were detected in all the sewage samples tested in this work, with median concentrations between 34 and 251ng/L.