Large-volume injection combined with gas chromatography/isotope ratio mass spectrometry for the analysis of polycyclic aromatic hydrocarbons.

Rationale: Compound-specific stable isotope analyses of carbon require relatively large amounts of sample for reliable analyses. Commonly applied injections of 1 μL may thus be insufficient for samples with low concentrations of pollutants (e.g.

Stable carbon isotopic ratio measurement of polycyclic aromatic hydrocarbons as a tool for source identification and apportionment--a review of analytical methodologies.

The measurement of the ratio of stable isotopes of carbon ((13)C/(12)C expressed as a δ(13)C) in the individual components of a sample may be used as a means to identify the origin of these components. This article reviews the approaches and reports on the successes and failures of source identification and apportionment of Polycyclic Aromatic Hydrocarbons (PAHs) with the use of compound-specific isotope analysis (CSIA). One of the conditions for a precise and accurate analysis of isotope ratios with the use of GC-C-IRMS is the need for well separated peaks, with no co-elutions, and reduced unresolved complex mixture (UCM).

Analysis of polycyclic aromatic hydrocarbons extracted from air particulate matter using a temperature programmable injector coupled to GC-C-IRMS.

Compound specific isotopic analysis (CSIA) can provide information about the origin of analysed compounds - in this case, polycyclic aromatic hydrocarbons (PAHs). In the study, PAHs were extracted from three dust samples: winter and summer filter dust and tunnel dust. The measurement was performed using the method validated in our laboratory using pure, solid compounds and EPA 610 reference assortment.

Use of a temperature-programmable injector coupled to gas chromatography-combustion-isotope ratio mass spectrometry for compound-specific carbon isotopic analysis of polycyclic aromatic hydrocarbons.

Compound-specific isotopic analysis (CSIA) can provide information about the origin of analysed compounds; for instance, polycyclic aromatic hydrocarbons (PAHs) in aerosols. This could be a valuable tool in source apportionment of particulate matter (PM) air pollution. Because gas chromatography-combustion-isotope ratio mass spectrometry (GC-C-IRMS) analysis requires an amount of at least 10 ng of an individual PAH, a high concentration of PAHs in the injected extract is needed.

Headspace solid phase microextraction--GC/C-IRMS for delta13CVPDB measurements of mono-aromatic hydrocarbons using EA-IRMS calibration.

This work aims at comparing the delta(13)C(VPDB) of mono-aromatic hydrocarbons benzene, toluene, ethylbenzene and xylene isomers (BTEX) measured by elemental analyser (EA)-isotope ratio mass spectrometer (IRMS) with the delta(13)C(VPDB) measured on the same compounds by headspace solid phase microextraction - GC/C-IRMS (hSPME - GC/C-IRMS) with the final goal of using these compounds as internal standards on the latter system. The EA-IRMS measurements were done using calcium and lithium carbonate isotopic reference materials: NBS19 and L-SVEC for establishing the delta(13)C(VPDB) scale. The EA-IRMS measurements with helium dilution of a set of five reference materials (USGS40, USGS41, IAEA-CH-6, IAEA-CH-3 and IAEA-601) show systematic bias of 1 per thousand relative to their assigned values.

Methods to reduce interference effects in thermal conversion elemental analyzer/continuous flow isotope ratio mass spectrometry delta18O measurements of nitrogen-containing compounds.

On-line determination of the oxygen isotopic composition (delta(18)O value) in organic and inorganic samples is commonly performed using a thermal conversion elemental analyzer (TC-EA) linked to a continuous flow isotope ratio mass spectrometry (IRMS) system. Accurate delta(18)O analysis of N-containing compounds (like nitrates) by TC-EA-IRMS may be complicated because of interference of the N(2) peak on the m/z 30 signal of the CO peak. In this study we evaluated the effectiveness of two methods to overcome this interference which do not require any hardware modifications of standard TC-EA-IRMS systems.

Assessment of age-related glucose oxidation rates of broiler chickens by using stable isotopes.

During their relatively short commercial lifespan of six weeks, broiler chickens undergo very pronounced age- or body weight-related changes in metabolic rate and body composition. The present study was aimed to assess the age-related changes in glucose oxidation rate of broiler chickens by using 13C-labeled glucose. The methodology for this breath test needed to be established first.

Influence of continuous isobaric rectal distension on gastric emptying and small bowel transit in young healthy women.

Patients with slow transit constipation frequently have delayed gastric emptying. In animals rectal distensions inhibit gastrointestinal motility. In healthy volunteers isovolumetric rectal distensions delay upper gut transit.

Influence of SDZ RAD vs. MMF on gastric emptying in renal transplant recipients.

SDZ RAD and mycophenolate mofetil (MMF) are increasingly used in the prevention of renal allograft rejection. SDZ RAD, having a macrolide structure, and MMF, known with gastrointestinal side-effects, may have gastric motility modifying properties. Gastric emptying was examined 1 yr after renal transplantation in eight patients taking corticosteroids (CS), cyclosporin A (CsA) and SDZ RAD and six patients treated with CS, CsA and MMF.

An inter- and intra-laboratory comparison of breath ¹³CO₂analysis.

Background: ¹³C breath test analysis requires accurate ¹³CO₂measurements.

Aim: To perform a multicentre study to evaluate the repeatability and reproducibility of breath ¹³CO₂analysis.

Methods: Two series of 25 paired randomly coded tubes (each consisting of 23 ¹³CO₂-enriched breath samples and two samples of standard reference pure CO₂with certified δ ¹³C(PDB)) were sent to participating centres for ¹³CO₂measurement.

In vivo influence of nicotine on human basal and NSAID-induced gut barrier function.

Background: Smoking reduces the non-steroidal anti-inflammatory drug (NSAID)-induced small intestinal permeability increase in healthy people. It also affects inflammatory bowel disease that is associated with a disturbed gut barrier function. To assess the role of nicotine on barrier function, its influence on basal and NSAID-induced intestinal permeability was studied in healthy volunteers.

Symptoms associated with impaired gastric emptying of solids and liquids in functional dyspepsia.

Objective: The relationship between functional dyspepsia and delayed gastric emptying of solids or liquids is still unclear. The aim of the present study was to investigate in dyspeptic patients the prevalence of delayed gastric emptying for solids or for liquids and to investigate the relationship to the dyspepsia symptom pattern.

Methods: In 392 and 330 patients with functional dyspepsia, the solid and liquid gastric emptying, respectively, was measured using breath tests, and the severity of eight dyspeptic symptoms was scored.

Oxidative breakdown of octanoic acid is maintained in patients with cirrhosis despite advanced disease.

As an octanoic acid 13CO2 breath test is frequently used to test gastric emptying of solid food, the purpose of the present study was to study whether oxidative breakdown of octanoic acid is affected by severe liver disease. The design of our study was twofold. First, cirrhotic patients (n = 82) of varying severity were compared with healthy controls (n = 17).

Erosive enterocolitis in mycophenolate mofetil-treated renal-transplant recipients with persistent afebrile diarrhea.

Background: Diarrhea is the most frequently reported adverse event in mycophenolate mofetil (MMF)-treated transplant patients. The aim of this study was to explore the gastrointestinal tract in MMF-treated renal transplant recipients with persistent afebrile diarrhea to characterize its nature and etiology.

Methods: Renal transplant recipients with persistent afebrile diarrhea (daily fecal output >200 g) were prospectively investigated for infections, morphologic, and functional (gastrointestinal motility and intestinal absorptive capacity) integrity of the gastrointestinal tract; 26 patients met the inclusion criteria.

Stable isotopes and 13CO2 breath tests for investigating gastrointestinal functions.

In medical investigation there is a need for non-invasive methods. Moreover, patients ask for easy methods that are simple to perform and medical doctors demand reliable techniques. With the advent of stable isotopes a new area of tracer technology became available.

Anti-tumor necrosis factor treatment restores the gut barrier in Crohn's disease.

Objectives: A primary defect of the tight junctions and, hence, increased intestinal epithelial permeability has been proposed as a basic pathogenic event in Crohn's disease. Challenge of the mucosal immune system by the commensal gut flora would then result in chronic inflammation. Alternatively, increased permeability could be the result of inflammation.

Magnesium chloride slows gastric emptying, but does not affect digestive functions.

Background: An inverse relationship has been established between serum magnesium and serum lipid levels. By means of breath tests, we tested the hypothesis that magnesium inhibits intraluminal lipid digestion and subsequently causes changes in lipid metabolism. We also investigated the influence of the administration of magnesium chloride on protein digestion and gastric emptying.

Anti-Saccharomyces cerevisiae antibodies (ASCA), phenotypes of IBD, and intestinal permeability: a study in IBD families.

Background: Serologic markers anti-Saccharomyces cerevisiae antibodies (ASCA) and antineutrophil cytoplasmic antibodies with perinuclear staining (pANCA) have been proposed to study the immunopathogenesis of IBD. Their measurement may allow better phenotyping of the disease and the detection of subclinical disease.

Aims: To test the hypothesis that serological markers identify an immunologic trait related to disease susceptibility.

Lactose-[13C]ureide breath test: a new, noninvasive technique to determine orocecal transit time in children.

Background: The lactose-[13C]ureide breath test (LUBT) is a novel, noninvasive test to determine orocecal transit time. Lactose ureide resists the action of brush border enzymes and is metabolized by colonic bacteria. The purpose of the present study was to adapt this breath test for children of various age groups and to determine whether it can be applied in infants, newborns, and preterms to study the development of small intestinal motility.

13C-methacetin breath test: isotope-selective nondispersive infrared spectrometry in comparison to isotope ratio mass spectrometry in volunteers and patients with liver cirrhosis.

The 13C-methacetin breath test (MBT) has been proposed for the noninvasive evaluation of the hepatic mixed function oxidase activity. Up to now, stable isotope analysis of carbon dioxide of the MBT has been carried out with isotope ratio mass spectrometry (IRMS). The aim of the present study was to test a recently developed isotope-selective nondispersive infrared spectrometer (NDIRS) in comparison to IRMS in healthy volunteers and patients with liver cirrhosis.

Evaluation of small-bowel transit for solid and liquid test meal in healthy men and women.

Evaluation of severe functional gastrointestinal motility disorders requires an investigation of the entire gastrointestinal tract. This should be possible with a single radionuclide imaging study. The purpose of this study was (1) to define normal values of small-bowel transit in men and women and (2) to assess a possible difference between gender or test meal, since it has been shown that women have slower gastric emptying than men, and gastric emptying of solids is slower than liquids.

13C-egg white breath test: a non-invasive test of pancreatic trypsin activity in the small intestine.

Background: The recent availability of egg white protein highly enriched with (13)C has allowed breath test technology to be adapted for the study of protein digestion and absorption. Pancreatic trypsin is considered to be the key enzyme in the proteolytic cascade.

Aim: To evaluate trypsin activity in the small intestine of healthy volunteers and patients with pancreatic disease by a recently developed (13)C-egg white breath test.

13C mixed-triglyceride breath test: isotope selective non-dispersive infrared spectrometry in comparison with isotope ratio mass spectrometry in volunteers and patients with chronic pancreatitis.

Background: The 13C mixed-triglyceride breath test (MTB) has been proposed for the non-invasive assessment of duodenal pancreatic lipase activity. Until now, stable isotope analysis of CO2 of the MTB has been carried out with isotope ratio mass spectrometry (IRMS). The aim of the present study was to compare MTB results by using the new non-dispersive infrared spectrometry (NDIRS) and the IRMS.