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At least 1,261 records · Page 70Linked to original sources
PubMed2001

A novel sample decomposition technique at atmospheric pressure for the determination of Os abundances in iron meteorites using isotope dilution inductively coupled plasma-mass spectrometry.

A safe and reliable analytical technique for the determination of Os abundances in ten iron meteorites of various chemical groups was developed using isotope dilution inductively coupled plasma-mass spectrometry coupled with a sample decomposition technique. A major advantage of the sample decomposition technique developed here is that the pressure inside the reaction flask is not increased through the decomposition reaction because the flask is a fully opened system, obviating the risk of explosion of the glass apparatus. Another advantage is that there is no restriction in the sample size being decomposed. In this study, about 2 g of metallic sample were decomposed safely, and this sample size, > 10 times larger than that typically used for the Carius tube technique, allows one to obtain more reliable Os data for heterogeneous samples. The metallic samples were decomposed in a glass flask purged with Ar. Since the O2 was purged from the reaction flask, Os was not oxidised to volatile OsO4, thereby preventing significant evaporation loss of Os. The typical recovery of Os throughout the sample decomposition and separation processes was > 80%, and the total Os blank through the decomposition of a 1 g amount of sample was less than 20 pg. Os abundances were determined by means of stable isotope dilution mass spectrometry using a 190Os-enriched isotopic tracer. Except for Sikhote-Alin, the measured Os abundances in almost all the iron meteorites exhibited a good agreement with the previously published Os abundance data, within the analytical uncertainty achieved in this study (2-5%). For the Sikhote-Alin meteorite, on the basis of a better correlation between Os and Ir abundances, we believe that our Os abundance data should be more reliable. The Os abundance data obtained in this work clearly demonstrated the suitability of the newly developed sample decomposition procedure for low level Os determinations.

Journal Article↗
PubMed2001

Influence of the procedure used to prepare the calibration sample set on the performance of near infrared spectroscopy in quantitative pharmaceutical analyses.

Calibrating near infrared diffuse reflectance spectroscopy (NIRS) methods usually involves preparing a set of samples with a view to expanding the analyte concentration range spanned by production samples. In this work, the performances of the two procedures most frequently used for this purpose in near infrared pharmaceutical analysis, viz., synthetic samples obtained by weighing of the pure constituents of the pharmaceutical and doped samples made by under- or overdosing previously powdered production samples, were compared. Both procedures were found to provide similar results in the quantification of the active compound in the pharmaceutical, which was determined with a relative standard error of prediction (RSEP) of < 1.6%. However, the two types of sample preparation provide different spectra, which precludes the accurate quantification of synthetic samples from calibrations obtained with doped samples and vice versa. None of the mathematical pre-treatments tested with a view to reducing this different scattering (viz., second derivative, standard normal variate and orthogonal signal correction) could effectively solve this problem. This hinders accurate validation of the linearity of the procedure and makes it advisable to use doped samples which are markedly less different to production samples.

Calibration↗
PubMed2004

Determination of arsenic species in fish, crustacean and sediment samples from Thailand using high performance liquid chromatography (HPLC) coupled with inductively coupled plasma mass spectrometry (ICP-MS).

Suitable techniques have been developed for the extraction of arsenic species in a variety of biological and environmental samples from the Pak Pa-Nang Estuary and catchment, located in Southern Thailand, and for their determination using HPLC directly coupled with ICP-MS. The estuary catchment comprises a tin mining area and inhabitants of the region can suffer from various stages of arsenic poisoning. The important arsenic species, AsB, DMA, MMA, and inorganic arsenic (As III and V) have been determined in fish and crustacean samples to provide toxicological information on those fauna which contribute to the local diet. A Hamilton PRP-X100 anion-exchange HPLC system employing a step elution has been used successfully to achieve separation of the arsenic species. A nitric acid microwave digestion procedure, followed by carrier gas nitrogen addition- (N2)-ICP-MS analysis was used to measure total arsenic in sample digests and extracts. The arsenic speciation of the biological samples was preserved using a Trypsin enzymatic extraction procedure. Extraction efficiencies were high, with values of 82-102%(As) for fish and crustacean samples. Validation for these procedures was carried out using certified reference materials. Fish and crustacean samples from the Pak Pa-Nang Estuary showed a range for total arsenic concentration, up to 17 microg g(-1) dry mass. The major species of arsenic in all fauna samples taken was AsB, together with smaller quantities of DMA and, more importantly, inorganic As. For sediment samples, arsenic species were determined following phosphoric acid (1 M H3PO4) extraction in an open focused microwave system. A phosphate-based eluant, pH 6-7.5, with anion exchange HPLC coupled with ICP-MS was used for separation and detection of AsIII, AsV, MMA and DMA. The optimum conditions, identified using an estuarine sediment reference material (LGC), were achieved using 45 W power and a 20 minute heating period for extraction of 0.5 g sediment. The stability and recovery of arsenic species under the extraction conditions were also determined by a spiking procedure which included the estuarine sediment reference material. The results show good stability for all species after extraction with a variability of less than 10%. Total concentrations of arsenic in the sediments from the Pak Pa-Nang river catchment and the estuary covered the ranges 7-269 microg g(-1)and 4-20 [micro sign]g g(-1)(dry weight), respectively. AsV was the major species found in all the sediment samples with smaller quantities of AsIII. The presence of the more toxic inorganic forms of arsenic in both sediments and biota samples has implications for human health, particularly as they are readily 'available'.

Animals↗
PubMed2005

Determination of extractable perfluorooctanoic acid (PFOA) in water, sweat simulant, saliva simulant, and methanol from textile and carpet samples by LC/MS/MS.

Methods were developed to quantify the amount of perfluorooctanoic acid (PFOA) extracted from textile and carpet samples through contact with water, methanol, and sweat and saliva simulants using LC/MS/MS. The limit of quantitation (LOQ) for samples extracted in water and sweat simulant is 1 ppb (ng PFOA (g sample)(-1)) while the limits of quantitation for samples extracted in saliva simulant and methanol were 3 ppb and 2.5 ppb, respectively. Method validation results are provided for a polyester control textile sample that was extracted in water on two different days by different analysts, which gave an overall recovery of 103% and standard deviation of 5.3% for 30 analyses. However, for routine application of these methods to a large number of sample sets differing in chemical and physical compositions, a complete validation for each sample type is not practical or possible since control samples for fortifications are often not available. Instead, suitable analytical methods and acceptance criteria are described which ensure accurate PFOA quantitation in each of the solvent extract types. During routine use of these methods, post-extraction spike recoveries for the different sample types and solvents are 100 +/- 15% using a dual isotopically labeled (13)C-PFOA internal standard to correct for matrix effects. A comparison of extraction solvent versus time using a wrist action shaker for textile and carpet samples demonstrates that the total extractable amount of PFOA is similar for each of the solvent types. However, as expected the rate of extraction in water and simulants is significantly less than that of methanol. Finally, a comparison of 2 h and 24 h wrist action shaker extractions with a 1.5 h pressurized fluid extraction (PFE) in methanol reveals that the 24 h wrist action shaker yields the highest results. The 2 h wrist action shaker results are similar to those of the 1.5 h PFE extraction.

Caprylates↗
PubMed2005

Extraction, interpretation and validation of information for comparing samples in metabolic LC/MS data sets.

LC/MS is an analytical technique that, due to its high sensitivity, has become increasingly popular for the generation of metabolic signatures in biological samples and for the building of metabolic data bases. However, to be able to create robust and interpretable (transparent) multivariate models for the comparison of many samples, the data must fulfil certain specific criteria: (i) that each sample is characterized by the same number of variables, (ii) that each of these variables is represented across all observations, and (iii) that a variable in one sample has the same biological meaning or represents the same metabolite in all other samples. In addition, the obtained models must have the ability to make predictions of, e.g. related and independent samples characterized accordingly to the model samples. This method involves the construction of a representative data set, including automatic peak detection, alignment, setting of retention time windows, summing in the chromatographic dimension and data compression by means of alternating regression, where the relevant metabolic variation is retained for further modelling using multivariate analysis. This approach has the advantage of allowing the comparison of large numbers of samples based on their LC/MS metabolic profiles, but also of creating a means for the interpretation of the investigated biological system. This includes finding relevant systematic patterns among samples, identifying influential variables, verifying the findings in the raw data, and finally using the models for predictions. The presented strategy was here applied to a population study using urine samples from two cohorts, Shanxi (People's Republic of China) and Honolulu (USA). The results showed that the evaluation of the extracted information data using partial least square discriminant analysis (PLS-DA) provided a robust, predictive and transparent model for the metabolic differences between the two populations. The presented findings suggest that this is a general approach for data handling, analysis, and evaluation of large metabolic LC/MS data sets.

Chromatography, Liquid↗
PubMed2006

Negative pressure pinched sample injection for microchip-based electrophoresis.

A simple method for injecting well-defined non-biased sample plugs into the separation channel of a microfluidic chip-based capillary electrophoresis system was developed by a combination of flows generated by negative pressure, electrokinetic and hydrostatic forces. This was achieved by using only a single syringe pump and a single voltage supply at constant voltage. In the loading step, a partial vacuum in the headspace of a sealed sample waste reservoir was produced using a syringe pump equipped with a 3-way valve. Almost instantaneously, sample was drawn from the sample reservoir across the injection intersection to the sample waste reservoir by negative pressure. Simultaneously, buffer flow from the remaining two buffer reservoirs pinched the sample flow to form a well-defined sample plug at the channel intersection. In the subsequent separation stage, the vacuum in headspace of the sample waste reservoir was released to terminate all flows generated by negative pressure, and the sample plug at the channel intersection was electrokinetically injected into the separation channel under the potential applied along the separation channel. The liquid levels of the four reservoirs were optimized to prevent sample leakage during the separation stage. The approach considerably simplified the operations and equipment for pinched injection in chip-based CE, and improved the throughput. Migration time precisions of 3.3 and 1.5% RSD for rhodamine123 (Rh123) and fluorescein sodium (Flu) in the separation of a mixture of Flu and Rh123 were obtained for 56 consecutive determinations with peak height precisions of 6.2% and 4.4% RSD for Rh123 and Flu, respectively.

Electrophoresis, Microchip↗
PubMed2002

Lopromide one-sample clearance as a measure of glomerular filtration rate.

OBJECTIVE: The pharmacokinetics of iopromide were analysed using a two-compartment model. The optimal point of time for blood withdrawal for calculation of a one-sample clearance was determined. METHODS: Plasma concentration of iodine was measured up to 8 h postinjection (p.i.) in 62 adult patients who received 120 ml iopromide for computed tomography (CT). A two exponential function was fitted by a weighted least error square method. As reference method, clearance was calculated from this function and the injected amount of iodine. Empirical parameters for calculation of one-sample clearance were determined. This one-sample clearance was compared with one-sample clearance calculated according to formulas developed for Tc99m-DTPA by Jacobsson as well as a two sample method. RESULTS: Total distribution volume of iopromide was calculated as 0.242 Lkg(-1)+/- 5.9%. A high correlation of all one-sample method and the two-sample method with reference to clearance was found. Best estimation of iopromide plasma clearance was achieved by determining one-sample clearance 270 or 285 min p. i. with SD(y.x) of 5.8 ml min(-1). CONCLUSIONS: After administration of 120 ml iopromide, one-sample plasma clearance can be calculated with low estimation error taking one blood sample at an appropriate time point. Late phase pharmacokinetics of iopromide found in the present study showed to be virtually identical to results published for iohexol and Tc99m-DTPA.

Adult↗
PubMed2000

Non-uniform systematic sampling in stereology.

Non-uniform systematic sampling designs in stereology are studied. Various methods of constructing non-uniform systematic sampling points from prior knowledge of the measurement function are presented. As an example, we consider area estimation from lengths of linear intercepts. The efficiency of two area estimators, based on non-uniform sampling of parallel lines, is compared to that of the classical 2D Cavalieri estimator, based on uniform sampling, in a sample of planar profiles from transverse sections of 41 small myelinated axons. The comparison is based on simulations. It is concluded that for profiles of this type one of the non-uniform sampling schemes is more efficient than the traditional uniform sampling scheme. Other examples where non-uniform systematic sampling may be used are in area estimation from lines emanating from a fixed point, area estimation from concentric circles or spirals and curve length estimation from sweeping lines. It is shown that proportional-to-size sampling is a special case of non-uniform systematic sampling. Finally, the effect of noise in the observations is discussed.

Axons↗
PubMed1999

Quest for postdialysis urea rebound-equilibrated Kt/V with only intradialytic urea samples.

BACKGROUND: Postdialysis urea rebound (PDUR) is a cause of Kt/V overestimation when it is calculated from predialysis and the immediate postdialysis blood urea collections. Measuring PDUR requires a 30- or 60-minute postdialysis sampling, which is inconvenient. Several methods had been devised for a reasonable approach to determine PDUR-equilibrated Kt/V in short dialysis without the need for a delayed sample. The aim of our study was to compare these different Kt/V methods during the longer eight-hour hemodialysis sessions, and to determine the optimum intradialytic urea sample time that fits best with PDUR. METHODS: The study included 21 patients (mean age 71.9 years) who were hemodialyzed for 60+/-60 months at three times eight hours weekly, using bicarbonate dialysate and cellulosic membranes. Blood urea samples were obtained at onset, and then at 17, 33, 50, 66, 75, 80, 85, and 100% of the dialysis session times, after 30 seconds of low flow, and then at 60-minutes postdialysis. All patients had a meal during dialysis. We compared four different formulas of Kt/V [(a) Kt/V-Smye with a 33% dialysis time urea sample, (b) two-pool equilibrated eKt/V, (c) Kt/V-std (Daugirdas-2) obtained with an immediate postdialytic sample, and (d) the different intradialytic urea samples for Kt/V (50, 66, 75, 80, and 85% of dialysis time)] with the equilibrated 60-minute PDUR Kt/V (Kt/V-r-60) formula as the reference method. RESULTS: The mean PDUR was 17.2+/-9%, leading to an overestimation of Kt/V-std by 12.2%. Kt/V-r-60 was 1.68+/-0.34. Kt/V-std was 1.88+/-0.36 (Delta = 12.2+/-4.8%, r = 0.8). eKt/V was 1.77+/-0.3 (Delta = 5+/-5%, r = 0.96), and Kt/V-Smye was 1.79+/-0.47 (Delta = 5.2+/-14%, r = 0.9). The best time for the intradialytic sampling was 80% (that is, at 6 hr and 24 min). The Kt/V-80 was 1.64+/-0.3 and was best fitted with Kt/V-r-60 (Delta = -1.8+/-8%, r = 0.91). The mean intradialytic urea evolution showed a three-exponential rate, in discrepancy with the two-exponential rate theoretical model. CONCLUSIONS: These results confirm that a significant postdialysis rebound exists in an eight-hour dialysis. An intradialytic urea sample taken at 80% of the total session time permits an estimation of the 60-minute Kt/V-rebound without the necessity of taking a delayed sample, with better accuracy than eKt/V or especially Kt/V-Smye. This may be related to a particular urea kinetics curve on the longer dialysis duration, which needs to be studied further.

Aged↗
PubMed2005

Rosenbluth-sampled nonequilibrium work method for calculation of free energies in molecular simulation.

We present methods that introduce concepts from Rosenbluth sampling [M. N. Rosenbluth and A. W. Rosenbluth, J. Chem. Phys. 23, 356 (1955)] into the Jarzynski nonequilibrium work (NEW) free-energy calculation technique [C. Jarzynski, Phys. Rev. Lett. 78, 2690 (1997)]. The proposed hybrid modifies the way steps are taken in the NEW process. With it, each step is selected from a range of alternatives, with bias given to steps that contribute the least work. The definition of the work average is modified to account for the bias. We introduce two variants of this method, lambda-bias sampling and configuration-bias sampling, respectively; a combined lambda- and configuration-bias method is also considered. By reducing the likelihood that large nonequilibrated work values enter the ensemble average, the Rosenbluth sampling aids in remedying problems of inaccuracy of the calculation. We demonstrate the performance of the proposed methods through a model system of N independent harmonic oscillators. This model captures the difficulties involved in calculating free energies in real systems while retaining many tractable features that are helpful to the study. We examine four variants of this model that differ qualitatively in the nature of their phase-space overlap. Results indicate that the lambda-bias sampling method is most useful for systems with entropic sampling barriers, while the configuration-bias methods are best for systems with energetic sampling barriers. The Rosenbluth-sampling schemes yield much more accurate results than the unbiased nonequilibrium work method. Typically the accuracy can be improved by about an order of magnitude for a given amount of sampling; this improvement translates into two or more orders of magnitude less sampling required to obtain a given level of accuracy, owing to the generally slow convergence of the NEW calculation when the inaccuracy is large.

Algorithms↗
PubMed2007

Accuracy of HPV testing of vaginal smear obtained with a novel self-sampling device.

BACKGROUND: Most of women diagnosed as having cervical cancer have not participated in organized cytological screening. Aim. A study was conducted to evaluate the accuracy of human papilloma virus testing by self-collected vaginal samples in comparison to regular cytological screening. The agreement of hybrid capture 2 assay and polymerase chain reaction assay for detection of human papilloma virus DNA in self-collected vaginal samples and clinician-obtained cervical smears was investigated. METHOD: Forty-three women aged 23-58 years admitted for further examination due to previous positive cytology in the organized screening participated in self-collecting of vaginal samples with a novel self-sampling device. During the visit a clinician also collected a cervical smear using a cytobrush. The vaginal samples collected with the self-sampling device were analyzed for high-risk human papilloma virus with the hybrid capture 2 assay technique and the cervical smears were Pap-stained, examined cytologically and after that reanalyzed for human papilloma virus DNA using a polymerase chain reaction assay. RESULT: The vaginal samples were positive for high-risk human papilloma virus in 37% of the cases using hybrid capture 2 assay. Twelve of the 43 Pap smears showed positive cytology (ASCUS-CIN 3), of which 4 showed CIN 2-3. When polymerase chain reaction assay was performed, human papilloma virus DNA was detected in 40% of the glass slides. The agreement between cytology and the two human papilloma virus testing techniques was 67-74% (kappa 0.27-0.45) and the agreement between the two human papilloma virus tests was 70% (kappa 0.36). CONCLUSION: Testing for high-risk human papilloma virus can identify more women at risk of developing cervical cancer than cytology irrespective of the sampling method. Furthermore, offering a self-sampling device for collection of vaginal smear seems to be a useful screening tool for cervical cancer among women not responding to an invitation for smear sampling.

Adult↗
PubMed1997

Development of an ileal amino acid digestibility assay for the growing chicken--effects of time after feeding and site of sampling.

1. The study aimed to establish the optimum time after ingestion and optimum sampling site for the development of an ileal amino acid digestibility assay for broiler chickens. 2. To establish the optimal sampling time, 4-week-old broiler chickens were given one of 6 protein sources (meat-and-bone, soyabean, cottonseed, fish, maize and wheat meals) as the sole source of protein in a test diet. The diets contained chromic oxide as an indigestible marker. The birds were starved for 24 h, fed and subsequently killed for sampling of ileal digesta (terminal 15 cm) at 2, 3, 4, 5 and 6 h after the start of feeding. 3. For the soyabean, fish, wheat and maize meal diets, sampling time had no significant effect on apparent ileal nitrogen digestibility, whereas for the meat-and-bone and cottonseed meal diets there was a significant quadratic effect of sampling time. The amount of digesta collected was maximised and the mean apparent ileal nitrogen digestibility had the lowest variation around the 4 h sampling time. 4. To establish the optimum sampling site, 4-week-old chickens were given either a meat-and-bone, a soyabean or a wheat bran meal-based diet. The birds were killed 4 h after the start of feeding, and digesta were sampled from 0-10, 0-15, 0-20 or 0-25 cm of terminal ileum. 5. There was no significant effect of sampling site on the apparent ileal digestibility of dietary nitrogen. The terminal 15 cm of ileum was considered a preferred site for sampling ileal digesta from broiler chickens.

Amino Acids↗
PubMed1991

Use of flagellin-enriched antigens in a rapid, simple and specific quantitative enzyme immunoassay for Lyme disease antibodies in human serum samples.

An enzyme immunoassay (EIA, ELISA) using microwells coated with a flagellin-enriched fraction of B. burgdorferi and absorbent-containing sample diluent for the quantitative determination of Lyme disease (LD) IgG and IgM antibodies in human serum samples was described. This LD EIA required three 15-minute incubations at room temperature, followed by a 1-step normalization of photometer readings to EIA units (EU/ml). Compared with tests using the whole bacterial extract as antigens and a sample diluent containing 6% BSA, this new LD EIA revealed lower values for 20 syphilis (SS) and 21 normal serum samples (NS) but about the same for 21 Lyme disease (LD) samples, allowing lower cut-off points which would place almost all these SS and NS samples below while almost all LD samples above the positive cut-off point. The LD EIA results of larger numbers (67 to 291) of mixed samples correlated with results of four reference EIA. However, the LD EIA gave lower (2 to 4 fold) reactivities (index values) with SS and NS samples but higher values with positive serum samples than reference EIA. Thus, this LD EIA showed improvements in both specificity and sensitivity over other tests compared.

Adjuvants, Immunologic↗
PubMed1976

Residues of 2, 4-D in air samples from Saskatchewan: 1966-1975.

Residues of 2,4-D (2,4-dichlorophenoxyacetic acid) in air samples from several sampling sites in central and southern Saskatchewan during the spraying seasons in the 1966-68 and 1970-75 periods were determined by gas-liquid chromatographic techniques. Initially, individual esters of 2,4-D were characterized by retention times and confirmed further by co-injection and dual column procedures. Since 1973, however, only total 2,4-D acid levels in air samples have been determined after esterification to the methyl ester and confirmed by gc/ms techniques whenever possible. Up to 50% of the daily samples collected during the spraying season at any of the locations and during any given year contained 2,4-D, with butyl esters being found most frequently. The daily 24-hr mean atmospheric concentrations of 2,4-D ranged from 0.01 to 1.22 mug/m3, 0.01 to 13.50 mug/m3, and 0.05 to 0.59 mug/m3 for the iso-propyl, mixed butyl and iso-octyl esters, respectively. Even when the samples were analysed for the total 2,4-D content, i.e. from 1973 onwards, the maximum level of the total acid reached only 23.14 mug/m3. In any given year and at any of the sampling sites, about 30% of the samples contained less than 0.01 mug/m3 of 2,4-D. In another 40% of the samples, the levels of 2,4-D ranged from 0.01 to 0.099 mug/m3. Only about 30% of the samples contained 2,4-D concentrations higher than 0.1 mug/m3, with only 10% or less exceeding 1 mug/m3. None of the samples, obtained with the high volume particulate sampler, showed any detectable levels of 2,4-D, indicating little or no transport of 2,4-D adsorbed on dust particles or as crystals of amine salts.

2,4-Dichlorophenoxyacetic Acid↗
PubMed2006

Umbilical artery catheter blood sampling volume and velocity: impact on cerebral blood volume and oxygenation in very-low-birthweight infants.

AIM: Blood sampling from umbilical artery catheters decreases cerebral blood volume and cerebral oxygenation. The aim of this study was to assess the impact of sampling volume and velocity. METHODS: Forty-eight infants, median birthweight 965 g (480-1500 g), median gestational age 27 wk (23-34 wk), were studied during routine blood sampling from umbilical artery catheters. The sampling procedure was performed following a strict protocol for draw-up volume (1.6 ml), sampling volume (1.7 ml or 0.2 ml), re-injection volume (1.6 ml) and flushing volume (0.6 ml), time of aspiration (40 s or 80 s), re-injection (30 s) and flushing (6 s). In each infant, sampling volume and aspiration time were subject to sequential variation in a randomized fashion (1.7 ml/40 s, 1.7 ml/80 s, 0.2 ml/30 s). Using near-infrared spectroscopy, changes in concentrations of cerebral oxygenated and deoxygenated haemoglobin were measured, and changes in cerebral blood volume and cerebral oxygenation were calculated. RESULTS: During all three sampling procedures, oxygenated haemoglobin decreased significantly from baseline, whereas deoxygenated haemoglobin did not change. Correspondingly, a decrease in cerebral blood volume and cerebral oxygenation occurred. This decrease was not affected significantly by extending the sampling time from 40 s to 80 s, whereas it was blunted by reducing the amount of blood withdrawn. CONCLUSION: Blood sampling from umbilical artery catheters induces a decrease in cerebral blood volume and cerebral oxygenation. The magnitude of the decrease depends on the blood volume withdrawn but not on sampling velocity.

Blood Pressure↗
PubMed2001

Significance of platelet aggregability immediately after blood sampling and effect of cigarette smoking.

A novel type platelet aggregometer, a WBA Analyzer, has enabled us to obtain the platelet aggregability data immediately after blood sampling, which is considered to closely reflect in vivo platelet function. Using this analyzer, we measured the platelet aggregatory threshold index (PATI) 5 min after blood sampling and compared it with that 60 min after blood sampling in 20 healthy male volunteers (10 smokers and 10 non-smokers). In the non-smokers, PATI was 10.3+/-2.3 microM 5 min after blood sampling, and it decreased to 4.7+/-1.5 (P<0.001) 60 min after blood sampling. In the smokers, the PATI was 7.7+/-2.9 microM 5 min after blood sampling, and it decreased to 3.8+/-1.5 (P<0.001) at 60 min after blood sampling. In the smokers, the PATI 5 min after blood sampling increased after a 4-week cessation of smoking (10.4+/-2.9, P<0.01), although the PATI 60 min after blood sampling did not change (4.2+/-1.6 microM). The measurement of platelet aggregability immediately after blood sampling using a WBA Analyser may be useful to evaluate not only platelet function in various thrombotic disorders, but also the effects of various anti-platelet drugs. Cessation of smoking should also be encouraged in the light of the adverse effects on platelet function.

Adult↗
PubMed2003

Prototype sampling system for measuring workplace protection factors for gases and vapors.

A prototype sampling system for measuring respirator workplace protection factors (WPFs) was developed. Methods for measuring the concentration of contaminants inside respirators have previously been described; however, these studies have typically involved continuous sampling of aerosols. Our work focuses on developing an intermittent sampling system designed to measure the concentration of gases and vapors during inspiration. This approach addresses two potential problems associated with continuous sampling: biased results due to lower contaminant concentrations and high humidity in exhaled air. The system consists of a pressure transducer circuit designed to activate a pair of personal sampling pumps during inspiration based on differential pressure inside the respirator. One pump draws air from inside the respirator while the second samples the ambient air. Solid granular adsorbent tubes are used to trap the contaminants, making the approach applicable to a large number of gases and vapors. Laboratory testing was performed using a respirator mounted on a headform connected to a breathing machine producing a sinusoidal flow pattern with an average flow rate of 20 L/min and a period of 3 seconds. The sampling system was adjusted to activate the pumps when the pressure inside the respirator was less than -0.1 inch H(2)O. Quantitative fit-tests using human subjects were conducted to evaluate the effect of the sampling system on respirator performance. A total of 299 fit-tests were completed for two different types of respirators (half- and full-facepiece) from two different manufacturers (MSA and North). Statistical tests showed no significant differences between mean fit factors for respirators equipped with the sampling system versus unmodified respirators. Field testing of the prototype sampling system was performed in livestock production facilities and estimates of WPFs for ammonia were obtained. Results demonstrate the feasibility of this approach and will be used in developing improved instrumentation for measuring WPFs.

Environmental Monitoring↗
PubMed2003

Analysis of sampling line bias on respirable mass measurement.

This study investigated the bias introduced by an inlet sampling line on a respirable mass monitor. The 1.5-m electrically conductive, flexible sampling line conducts aerosol at a flow rate of 2.2 Lpm from a helmet-mounted inlet to a waist-mounted sensor for mass concentration measurement. Particulate transport was modeled for each section of the sampling line and considered the effects of diffusion, gravitational settling, and inertial impaction. An estimate of respirable mass concentration measured with the sampling line was determined by integrating assumed workplace aerosols with the transport curves. The bias introduced by the sampling line was then calculated by dividing the difference between the respirable mass concentration with and without the sampling line by that without the sampling line. For the current sampling line, in which the inner diameter is 4.83 mm, bias was calculated as -0.3 percent, -2.4 percent, -4.6 percent, and -6.7 percent for four test aerosols with mass median aerodynamic diameters of 0.6 microm, 4 microm, 12 microm, and 30 microm, respectively. Optimization studies suggest that increasing the sampling line with a larger inner diameter by a factor of 1.25 to 1.75 will minimize bias to below -3.0 percent. An experimental study confirmed that bias due to the presence of the sampling line is small.

Aerosols↗