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At least 397 records · Page 22Linked to original sources
PubMed2001

Determination of aldehydes and ketones in air samples using cryotrapping sampling.

A cryotrapping sampling technique using glass traps cooled in liquid nitrogen for monitoring carbonyl compounds in air has been developed. Sampling was followed by derivatization by addition of acidified 2,4-dinitrophenyl hydrazine (DNPH) solution to the traps and an aliquot of the sample was analysed with a high performance liquid chromatograph system (HPLC), equipped with a diode array detector. The procedure was optimised concerning derivatization conditions and analytical parameters on formaldehyde, acetaldehyde, propanal, acetone, butanal and benzaldehyde. The technique was applied in monitoring their concentration in the urban atmosphere in Ljubljana.

Air Pollutants↗
PubMed1999

Fractional analysis of sequential induced sputum samples during sputum induction: evidence that different lung compartments are sampled at different time points.

BACKGROUND: The effect of the duration of sputum induction on markers of inflammation in induced sputum is unknown, and the optimal duration of sputum induction for research purposes in airway disease is uncertain. OBJECTIVE: We sought to determine whether the duration of sputum induction influences the cellular or biochemical characteristics of induced sputum. METHODS: Induced sputum was collected sequentially at 4-minute intervals during a 20-minute sputum induction in 12 subjects with mild and moderate asthma. Each 4-minute sample was collected and analyzed separately for total and differential cell counts and for levels of eosinophil cationic protein, fibrinogen, mucin-like glycoprotein, and surfactant protein SP-A. RESULTS: The percentages of eosinophils and neutrophils were significantly higher at the beginning of the 20-minute sputum induction than at the end, whereas the percentage of macrophages was significantly lower at the beginning than at the end. In addition, the levels of eosinophil cationic protein and mucin-like glycoprotein were significantly higher at the beginning of the 20-minute induction than at the end, whereas the level of surfactant protein SP-A was significantly lower. CONCLUSIONS: The duration of sputum induction significantly affects the cellular and biochemical composition of induced sputum in a manner suggesting that large airways are sampled at the beginning of sputum induction, whereas peripheral airways and alveoli are sampled at later time periods. Our data demonstrate the importance of standardizing the duration of sputum induction in clinical research studies, and on the basis of these data, we have chosen 12 minutes as the optimal duration for sputum induction in asthmatic subjects.

Adult↗
PubMed2003

Empathy and narcissism in a sample of child abuse perpetrators and a comparison sample of foster parents.

OBJECTIVE: The purpose of this research was to study the personality variables of empathy and narcissism in a sample of child abuse perpetrators and a comparison sample of foster parents, conceptualized as nonabusive parents, in order to gain further understanding of perpetrators and to provide clues for intervention. METHOD: The sample consisted of two groups: physically and emotionally abusive parents (n=52) and foster parents (n=101). Participants responded to three instruments: the Interpersonal Reactivity Index (IRI), an instrument measuring individual differences in empathy, and two instruments measuring narcissism: the Narcissistic Personality Inventory (NPI) and the Hypersensitivity Narcissism Scale (HSNS). RESULTS: Statistically significant differences were found between the two groups on three of the four subscales of the IRI: perspective-taking, empathic concern, and personal distress. Based on the definition of these subscales, the abusive parents as compared to the foster parents were not able to take the perspective of another or see things from another's viewpoint, showed less warmth, compassion and concern for others, and experienced difficulty in tense interpersonal situations. Statistically significant differences were found for the two groups on three of the six subscales of the NPI: authority, exhibitionism, and superiority, and on the HSNS. The abusive parents demonstrated less self-confidence, a greater lack of impulse control and were more narcissistic than their foster parent counterparts. CONCLUSIONS: The results suggest that it is how the perpetrators experience aversive behavior in their children that may provoke them to physically and emotionally abuse their children. Their self-centeredness in addition to their deficiencies in empathy may cause them to experience their children's misbehavior as an affront to their authority. Implications for treatment are made from this conceptualization of parental abuse.

Adult↗
PubMed2001

Simplified in-line sample preparation for amino acid analysis in carbohydrate containing samples.

This report describes a new, automated chromatographic procedure eliminating carbohydrates from amino acid samples prior to their analysis by anion-exchange chromatography and integrated amperometric detection. In the first step, a sample is brought onto a short cation-exchange column (trap column) in hydrogen form. Carbohydrates are passing through this column, while only amino acids are retained. Subsequently, the cation-exchange column, holding the amino acid fraction, is switched in-line with the gradient pump and separator column. The mobile phase used at the beginning of the separation (NaOH; pH 12.7) transfers amino acids from the trap column onto the anion-exchange column and the amino acid separation is completed without any interference by carbohydrates. All common amino acids are recovered following the carbohydrate removal step. The average value of their recovery is 88.1%. The calibration plots were tested between 12.5 and 500 pmol (amounts injected). The mean value of correlation coefficients of calibration plots was calculated as 0.99. The mean value of relative standard deviations from five replicates was 3.9%. The usefulness of the method is illustrated with two chromatograms of a carrot juice sample obtained before and after the in-line removal of carbohydrates.

Amino Acids↗
PubMed2003

Electrospray-atmospheric sampling glow discharge ionization source for the direct analysis of liquid samples.

Coupling electrospray with atmospheric sampling glow discharge ionization for the direct analysis of liquid-phase samples is demonstrated. Electrospray is utilized for nebulizing and transporting intact sample molecules into the glow discharge where ionization occurs through various pathways, including electron ionization and ion-molecule reactions with reagent ions. Reagent ions are formed through ionization of air molecules in an area of reduced pressure. The effects of discharge current, electrospray voltage, and solution flow rate on the absolute and relative ion intensities observed in the mass spectra are discussed. This technique is applicable to compounds containing various functional groups and encompassing a range of volatility. Analysis of organic compounds with varying volatility and polarity is discussed to illustrate the utility of this ionization technique.

Journal Article↗
PubMed2005

Equilibrium sampling through membranes of freely dissolved chlorophenols in water samples with hollow fiber supported liquid membrane.

The freely dissolved concentration (C(free)) of pollutants is generally believed to be bioavailable and thus responsible for toxic effects. The C(free) of organic weak acids and bases consists of a dissociated and a nondissociated fraction. By using chlorophenols as model compounds, a negligible-depletion extraction technique, equilibrium sampling through membranes (ESTM), was developed for the measurement of the nondissociated part of the C(free). Polypropylene hollow fiber membranes (280-microm i.d., 50-microm wall thickness, 0.1-microm pore size, 15-cm length) were impregnated with undecane in the pores in the fiber wall as liquid membrane and filled with buffer solution in the lumen as acceptor. Then, the hollow fiber membranes were placed into the sample (donor) for an equilibrium extraction after sealing the two ends. The chlorophenol concentrations in the acceptor were then determined by direct injection into a HPLC system. Finally, the C(free) of the nondissociated and the dissociated species of a chlorophenol were calculated based on its measured concentration in the acceptor, its pK(a) value, and the measured pH in sample and acceptor. Theoretically calculated distribution coefficients (D = 8-970) agree well with the experimental enrichment factors (E(e(max)) = 6-1124), and the equilibration time was observed to increase with increasing distribution coefficients (hours to days). The freely dissolved concentration of five chlorophenols, with a wide range of pK(a) (4.9-9.2) and log K(ow) (2.35-5.24), were successfully determined in model solutions of humic acids and at low-ppb levels in river and leachate water.

Buffers↗
PubMed2007

Selective sample cleanup by reusable sol-gel immunoaffinity columns for determination of deoxynivalenol in food and feed samples.

The paper describes the development of a simple and highly selective method for the determination of deoxynivalenol (DON) in food and feed samples. It combines sample cleanup with sol-gel immunoaffinity columns containing monoclonal anti-DON antibodies and quantification of DON by high-performance liquid chromatography with ultraviolet detection. The sol-gel immunoaffinity columns are as selective as commercial DON immunoaffinity columns but superior with regard to production costs, storage stability, and reusability. In applying the method for the analysis of maize, wheat, and spaghetti samples, it offers detection limits (LOD, S/N = 3) of 240, 200, and 207 ng/g, and recoveries of 83, 99, and 97%, respectively.

Antibodies, Monoclonal↗
PubMed1996

On-line microdialysis sample cleanup for electrospray ionization mass spectrometry of nucleic acid samples.

A major limitation of electrospray ionization mass spectrometry (ESI-MS) for oligonucleotide analysis arises due to sodium adduction, a problem that increases with molecular weight. Sodium adduction can preclude useful measurements when limited sample sizes prevent off-line cleanup. A novel and generally useful on-line microdialysis technique is described for the rapid (approximately 1-5 min) DNA sample cleanup for ESI-MS. Mass spectra of oligonucleotides of different size and sequence showing no significant sodium adduct peaks were obtained using the on-line microdialysis system with sodium chloride concentrations as high as 250 mM. Signal-to-noise ratios were also greatly enhanced compared to direct infusion of the original samples. By using ammonium acetate as the dialysis buffer, it was also found that the noncovalent association of double-stranded oligonucleotides could be preserved during the microdialysis process, allowing analysis by ESI-MS.

Base Sequence↗
PubMed1985

Decision making under uncertainty: a comparison of simple scalability, fixed-sample, and sequential-sampling models.

The purpose of this article is to investigate the learning and memory processes involved in decision making under uncertainty. In two different experiments, subjects were given a choice between a certain alternative that produced a single known payoff and an uncertain alternative that produced a normal distribution of payoffs. Initially this distribution was unknown, and in the first experiment it was learned through feedback from past decisions, whereas in the second experiment it was learned by observing sample outcomes. In the first experiment, a response deadline was used to limit the amount of time available for making a decision. In the second experiment, an observation cost was used to limit the number of samples that could be purchased. The mean and variance of the uncertain alternative and the value of the certain alternative were factorially manipulated to study their joint effects on choice probability, choice response time (Experiment 1), and number of observations purchased (Experiment 2). Algebraic-deterministic theories developed for decision making with simple gambles fail to explain the present results. Two new models are developed and tested--fixed- and sequential-sampling models--that attempt to describe the learning and memory processes involved in decision making under uncertainty.

Adult↗
PubMed1999

Air sampling of fungal spores on filters. An investigation on passive sampling and viability.

In this study, glycerol was tested as a collection substrate for passive bioaerosol sampling. Filters (mixed cellulose acetate and nitrate) were soaked in glycerol and exposed for an aerosol from three different fungal species: Penicillum commune, Aspergillus versicolor and Paecilomyces variotii. The passive sampling method was compared with a closed-face polycarbonate filter sampling method. Exposure was performed in an exposure chamber. The total number of spores was determined by microscopic techniques, and the cultivable number was determined by cultivation on Malt Extract Agar dishes. The glycerol soaked filter demonstrated a good correlation with the closed-face sampler with regard to the total count. Spores stored in a pumped filter cassette were not affected by storage for up to 7 days. On the other hand, the culturability of the spores was markedly decreased after 1 day when stored on glycerol soaked filters.

Aerosols↗
PubMed1998

Direct assessment of peripheral pharmacokinetics in humans: comparison between cantharides blister fluid sampling, in vivo microdialysis and saliva sampling.

AIMS: Skin blister fluid sampling, in vivo microdialysis and saliva sampling are commonly employed as surrogates for the measurement of drug concentrations in peripheral compartments. Although expected to exhibit comparable results, data derived from these techniques have never been directly compared. Thus, the aim of the present study was to evaluate the comparability of these techniques. METHODS: Paracetamol, a model drug with low protein binding, was administered to seven healthy volunteers at an oral dose of 2000 mg. Subsequently, tissue kinetics were measured simultaneously in cantharides induced skin blisters, microdialysates of subcutaneous- and skeletal muscle-tissue and saliva and compared to serum concentrations. RESULTS: Mean ratio (AUCblister/AUCserum) was 0.88 (95% CI, 0.50-1.26), mean ratio (AUCmuscle/AUCserum) was 1.08 (0.67-1.49), mean ratio (AUCsubcutaneous/AUCserum) was 0.96 (0.41-1.51) and mean ratio (AUCsaliva/AUCserum) was 1.83 (1.39-2.27). In this study the concentration profiles after single oral administration differed among the three methods. The time course of the concentration (peripheral compartment)/concentration (serum)-ratios showed that cantharides blister and microdialysate concentrations closely paralleled serum levels. An equilibration period of less than 2 h had to be taken into account for blister measurements. In contrast, saliva concentrations were significantly higher than corresponding serum concentrations. CONCLUSIONS: Skin blister sampling and microdialysis closely mirrored corresponding serum concentrations and, thus, proved to be suitable techniques for the assessment of peripheral compartment pharmacokinetics. In contrast, saliva data overestimated the corresponding serum concentrations.

Acetaminophen↗
PubMed1999

Comparison of blood ionized calcium and acid-base variables in samples obtained from different sampling sites in dairy cows.

Ionized calcium (Ca2+) concentrations, pH, blood gas tensions (pCO2 and pO2), base excess (BE), and bicarbonate (HCO3-) concentrations were determined and standard ionized calcium (stCa2+) concentrations were calculated (Ca2+ corrected to pH 7.4) for the blood withdrawn from the jugular vein, the coccygeal vein or coccygeal artery and the milk vein in 29 clinically healthy post-partum dairy cows. The blood withdrawal site had no significant effect on the blood ionized calcium and standard ionized calcium (mean differences among the blood samples varied between 0.01 and 0.05 mmol/l), or on bicarbonate concentrations or base excess. pH, pCO2 and pO2 were significantly lower or higher in samples taken from the coccygeal vein compared to other venous blood samples.

Acid-Base Equilibrium↗
PubMed1985

Determination of assay parameters for RNA analysis in bacterial and duodenal samples by spectrophotometry. Influence of sample treatment and preservation.

A simple analytical procedure derived from that described by Zinn and Owens (1980), based on the determination of nucleic purine bases (RNA eq), was carried out to measure microbial nitrogen flow in the ruminant duodenum. Several procedures for sample preservation were tested; the efficiency of each step of the analytical method was also determined using high performance liquid chromatography (HPLC). The proposed method (RNA eq) was compared with two other methods considered as references (2-6 diaminopimelic acid and 35S incorporation) and microbial nitrogen flow was measured in defaunated sheep. The recovery of purine bases analysed by the Zinn and Owens method was generally good (101% pure bases; 90% when bases were added to bacterial samples; 96% when added to yeast RNA). The HPLC measurements allowed us to conclude that this spectrophotometric method is specific for purine bases, all pyrimidine bases being eliminated. Moreover, it was found that the method must be used on freeze-dried samples; storage at + 4 degrees C, defatting or freezing gave incorrect results. Using the described assay, we observed that microbial nitrogen flow at the duodenum of defaunated sheep was not significantly different from that obtained using more traditional markers such as sulphur-35 incorporation or diaminopimelic acid.

Adenine↗
PubMed1984

Sampling for formaldehyde in workplace and ambient air environments--additional laboratory validation and field verification of a passive air monitoring device compared with conventional sampling methods.

Results of three extensive plant field tests using both area and personal sampling and involving 51 sets of comparison samples show the Du Pont Pro-Tek Formaldehyde Badge to have excellent correlation with three commonly used formaldehyde monitoring methods. In addition, comprehensive laboratory validation tests are reported which confirm an overall accuracy of +/- 9.6 to +/- 11.6% for the badge over an exposure range of 0.12-6.8 ppm. Laboratory test data are also included showing that the badge: (1) meets NIOSH and OSHA accuracy requirements of less than or equal to +/- 25% down to 1.6 ppm-hours (200 ppb) for an 8-hour TWA exposure; (2) is capable of accurately sampling for 15-minute exposures; and (3) is not affected by pressure or relative humidity variations.

Air Pollutants, Occupational↗
PubMedDate not supplied

Traditional sampling with laboratory analysis and solid phase microextraction sampling with field gas chromatography/mass spectrometry by military industrial hygienists.

The opinions or assertions contained herein are the private ones of the authors and are not to be construed as official or reflecting the views of the United States Department of Defense or the Uniformed Services University of the Health Sciences. Rapid on-site detection and identification of environmental contaminants to which personnel may be exposed is often needed during military deployment situations. The availability of military industrial hygienists with capabilities for "complete" on-site exposure assessment of chemical species should allow detection and identification of a number of important stressors almost immediately following sample collection. Portable gas chromatography/mass spectrometry (GC/MS) provides a rapid and efficient separation of volatile and semivolatile organic analytes, accompanied by sensitive electron impact ionization-mass spectrometry (EI-MS) detection. The use of GC/MS in the field is limited, however, by equipment cost, complexity of the equipment, and the analytical process. Additionally, a skilled operator is needed to obtain useful separations and to interpret mass spectral data. To demonstrate benefits and limitations of "complete" exposure assessment capabilities, a previously unidentified complex mixture, produced by thermal dispersion of riot control agents, was examined. Established active sampling methods were used with laboratory analyses. Solid phase microextraction, a passive sampling method that simplifies preparation for GC/MS analysis, also was used with a field-portable GC/MS system. Both sampling/analysis methods were used to detect CS riot control agent-derived air contaminants dispersed from riot control type canisters through oxidizer-supported combustion of a chemical fuel.

Chemistry Techniques, Analytical↗
PubMed1989

Eddy current distributions in cylindrical samples: effect on equivalent sample resistance.

We present a general technique for the determination of eddy current distributions within an irregularly shaped conducting sample in the uniform field of an NMR RF coil. Also presented is a general expression for the sample-induced coil resistance. The technique is applied specifically to a conducting cylindrical solid. Unlike previous descriptions of cylindrical samples in solenoidal coils where the induction is parallel to the axis of the cylinder and eddy current streamlines are circular, we treat the case where the induction is perpendicular to the cylindrical axis and where consequently eddy current streamlines take on an irregular shape.

Electric Conductivity↗
PubMed2006

Assessment of microsatellite instability in very small microdissected samples and in tumor samples that are contaminated with normal DNA.

Microsatellite instability (MSI) testing is important for the management of young patients with colonic adenocarcinoma. Biopsies can be small and can be contaminated by normal cells. It is not known how sample size or contamination by non-neoplastic cell populations affects the interpretation of MSI assays. Serial microdissection targets (0.75 to 5.5 mm) were obtained from cases with high-level MSI. Polymerase chain reaction was performed for the standard National Cancer Institute recommended markers and products were analyzed by capillary electrophoresis. DNA from a patient with a BAT25 polymorphism was used to determine the sensitivity of detecting an aberrant allele in otherwise normal DNA. In small targets, MSI was seen sporadically in the setting of low DNA concentration. The results for small targets ranged from 1/4 to 5/5 loci with MSI, secondary to allelic dropout. In the sensitivity study, the aberrant allele was detected only when present at a concentration of above 10%. Allelic dropout can lead to under-estimation of the presence of MSI in small tissue samples or samples with low DNA concentration. Contaminating normal cell DNA can mask the presence of MSI. MSI testing on tissue fragments that are <5.5 mm can lead to a false-negative MSI test.

Alleles↗
PubMed2006

Minimum detectable activity concentration in direct alpha spectrometry from outdoor air samples: continuous monitoring versus separate sampling and counting.

Rapid method for identifying the presence of alpha particle emitting radionuclides in outdoor air is of paramount importance should a nuclear or radiological incident occur. Minimum detectable activity concentrations of U, U, Pu, and Pu in outdoor air are calculated for two direct alpha spectrometry methods: continuous air monitoring is compared with separate sampling and subsequent alpha particle counting in a vacuum chamber. The radon progeny activity concentration typical for outdoor air and the effects for the alpha particle spectra caused by the properties of the filter and the aerosol particles are taken into account using measurements and Monte Carlo simulations. Continuous air monitoring is a faster method for identifying the presence of (trans)uranium elements when their activity concentration is considerably higher than the typical detection limit. Separate sampling and counting in a vacuum chamber is a more sensitive method when concentrations are close to the detection limit and when the duration of the sampling-counting cycle is greater than approximately 2 h. The method may serve as a tool for rapid field measurements.

Air Pollutants, Radioactive↗