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PubMed1999

Direct injection versus liquid-liquid extraction for plasma sample analysis by high performance liquid chromatography with tandem mass spectrometry.

Direct injection versus liquid-liquid extraction for post-dose human plasma sample analysis by high performance liquid chromatography with tandem mass spectrometry (LC/MS/MS) have been studied using a drug candidate compound. For the direct-injection method, an Oasis(R) HLB column (1 x 50 mm, 30 micrometer) was used as the on-line extraction column and a conventional Waters symmetry C18 column (3.9 x 50 mm, 5 micrometer) was used as the analytical column. Each plasma sample (100 microL) was mixed with 100 microL of a working solution of the internal standard in aqueous 0.05 M ammonium acetate (pH 6.9), and portions (10 microL) of these samples were then injected into the LC/MS/MS system. For the liquid-liquid extraction method, a YMC Basic C18 column (2.0 x 50 mm, 5 micrometer) was used as the analytical column. Each sample (0.5 mL) was extracted with methyl tert-butyl ether and the extract was reconstituted and injected into the LC/MS/MS system. The total analysis time for both methods was 2.0 min per sample. The accuracy, inter-day precision and intra-day precision obtained from the quality control samples were within 8% for both methods. The analysis results of post-dose human plasma samples showed that the deviations of 91% of the concentrations obtained using the direct-injection method were within +/-20% from the concentrations obtained using the liquid-liquid extraction method, and the overall average percentage deviation was -1.5%. The results showed that the two methods were equivalent in terms of total chromatographic run time, accuracy and precision. However, for a batch of 100 samples, the sample preparation time for the direct-injection method was only about 25% of the time required for liquid-liquid extraction. This decrease in sample preparation time resulted in the doubling of the overall sample analysis throughput.

Chromatography, High Pressure Liquid↗
PubMed2002

Automation for continuous analysis on microchip electrophoresis using flow-through sampling.

Automation of electrophoretic microchips for sequential analysis of different samples is demonstrated. This system used an autosampler, which was on-line connected to the microchip and the whole process including sample loading and injection, analysis and data acquisition as well as washing were all automated. Rhodamin B at different concentrations was first loaded into a hydrodynamic flow stream by an autosampler, delivered to the microchip, and then sequentially injected into the electrophoretic microchannel for analysis and detection. Automation was achieved by running two independent programs, one for sample loading by an autosampler and the other one for electrophoretic injection by voltage switching, on the same computer. Using this sampling chip, each loaded volume (0.2-1 microL) can be injected for dozens of electrophoretic analyses (1-10 nL for each injection). The variances caused by the external connections, which did not affect the electrophoretic analysis but would cause band broadening of the loaded sample in the hydrodynamic flow stream, were theoretically deduced. Results indicate that the dead volume (approximately 300 nL) due to the connection fitting on the chip could lead to dilution of the loaded sample by a factor of one when 0.2 microL of sample was loaded. Such a design allows sequential analysis of a series of samples while the running buffer is continuously pumped into the connection capillary as well as microchannels for washing between two loaded samples to minimize cross contamination without human intervention. Using this sampling chip, the required sample amount and handling time can be greatly reduced compared to the manual method.

Automation↗
PubMed2004

Alcohol consumption and other maternal risk factors for fetal alcohol syndrome among three distinct samples of women before, during, and after pregnancy: the risk is relative.

Data were obtained from three samples of women of childbearing age. One sample of women is from prenatal clinics serving Plains Indian women. The second sample is of women from the Plains whose children were referred to special diagnostic developmental clinics, as their children were believed to have developmental issues consistent with prenatal alcohol consumption. The third sample is of women from South Africa, each of whom has given birth to a child diagnosed with full fetal alcohol syndrome (FAS). Data across samples conform to expected trends on many variables. For example, the maternal age at time of pregnancy, a major risk factor for FAS, ranged from a mean of 23.5 years for the prenatal clinic sample, to 23.8 years for the developmental clinic sample, to 27.6 for the sample of women who have delivered children with FAS. Other variables of maternal risk for FAS expected from the extant literature, such as high gravidity and parity, binge drinking, heavy intergenerational drinking in the mother's extended family and immediate social network, and length of drinking career, were compared across the three samples with variable results. However, normative measures of drinking problems are unreliable when reported across cultures. An unexpected finding from this three-sample comparison was the differential risk found when comparing U.S. women to South African women. Women in the U.S. Plains Indian samples report a high consumption of alcohol in a binge pattern of drinking, yet there is less detectable damage to the fetus than among the South African women. Body mass index (BMI) and lifelong and current nutrition may have a substantial impact, along with the above factors, in relative risk for an FAS birth. The level of risk for producing a child with FAS is influenced by environmental and behavioral conditions that vary between populations and among individual women. Also, because many syndromes are genetically based, there is a need for full behavioral and genetic histories of the mother, family, and child being studied. Collecting extensive behavioral information as well as genetic histories will provide the requisite information for making an accurate diagnosis of FAS.

Adolescent↗
PubMed2005

Evaluation of a nuclear score for p16INK4a-stained cervical squamous cells in liquid-based cytology samples.

BACKGROUND: The p16INK4a gene product is overexpressed strongly in abnormal cervical epithelia and may serve as a valuable biomarker to identify abnormal cells in cervical smears or liquid-based cytology samples. METHODS: The authors performed p16INK4a immunocytochemistry to locate cells that expressed p16INK4a in liquid-based cytology samples and used a nuclear scoring system based on several morphologic criteria to interpret the degree of abnormality of these cells. RESULTS: Among 108 samples that were scored as normal in Papanicolaou-stained, parallel slides, any p16INK4a-positive cells were observed in 13 samples (12%), but only 1 of 108 samples (1%) was scored abnormal after applying nuclear scoring criteria. In the group of 52 low-grade squamous intraepithelial lesion (LSIL) samples, 19 samples (37%) were positive for any p16INK4a reactivity, but only 5 of those samples (10%) were scored abnormal after applying the nuclear score. Among the 50 high-grade squamous intraepithelial lesion (HSIL) samples, 49 samples (98%) were positive for p16INK4a and were scored as abnormal. Comparison of the scoring results of independent observers revealed good reproducibility of the nuclear score. CONCLUSIONS: The current results suggested that p16INK4a enables the location of potentially abnormal cells on liquid-based cytology samples. The nuclear score facilitated interpretation of the degree of abnormality of p16INK4a-stained cells. Thus, locating potentially abnormal cells by p16INK4a immunocytochemistry and their interpretation based on the nuclear score described here may help to identify patients with HSIL in cytologic screening programs and may represent a new approach for reducing the number of equivocal or misinterpreted cytologic specimens.

Adolescent↗
PubMed2005

Ethnicity and sampling bias in binge eating disorder: Black women who seek treatment have different characteristics than those who do not.

OBJECTIVE: The current study investigated sampling bias as it affects recruited clinic samples of Black and White women with binge eating disorder (BED). METHODS: Clinical characteristics of a recruited clinic sample (35 Black and 302 White consecutively evaluated women) with BED were compared with a community sample of Black and White women with BED drawn from the New England Women's Health Project. The clinic and community groups met the same definition of BED and were assessed with identical methods. RESULTS: Among White women, the clinic and community samples differed on some features (higher body mass index [BMI], and greater eating concerns and shape concerns in the clinic sample) but these differences reflected small to moderate effects sizes. In contrast, among Black women, the clinic sample had substantially higher levels (large effect sizes) of several features of eating disorders (eating concerns, dietary restraint, and shape concern), higher (moderate effect size) BMI, but lower frequency of binge eating (moderate effect size) than the community sample. A comparison of Black and White women within the clinic sample revealed little difference in clinical presentation, except for the significantly higher BMI among Black women. CONCLUSION: A sampling bias appears to exist between both White and Black recruited clinic samples of women with BED, although the bias appears to be substantially greater for Black women. Black women with BED who seek treatment have significantly different characteristics than those who do not.

Adult↗
PubMed1997

Detection of Mycobacterium tuberculosis by PCR analysis of urine and other clinical samples from AIDS and non-HIV-infected patients.

A number of different clinical specimens, such as sputum, cerebrospinal fluid and blood, have been reported to be good substrates for the detection of Mycobacterium tuberculosis by PCR assay. We wanted to search for the presence of mycobacteria in other body fluids, such as urine. Urine samples and other samples obtained from AIDS patients and non HIV-infected patients were analysed by PCR. The results were compared with those obtained using conventional methods (Bactec 460 TB and AFB (acid fast bacilli strain)). We analysed 412 urine samples and 210 different other samples (sputum and cerebrospinal fluid) obtained from AIDS patients by PCR; almost identical levels of PCR-positive (14-17%) results were observed in all samples analysed. The results were then compared with those obtained with the Bactec 460 TB and AFB. PCR, Bactec 460 TB and acid fast stain were also used to analyse 190 urine samples and 230 other samples from non-HIV infected patients in the consumption ward of Sassari Hospital. The number of urine samples positive by PCR (6.3%) and Bactec 460 TB (2.1%) was half that obtained from samples taken from the AIDS patients. As expected, an increase in the number of positive sputum samples was observed with all methods. The results indicate that PCR analysis of urine samples represents a valid alternative for fast and sensitive detection of M. tuberculosis. This method can be routinely used in the clinical laboratory, especially in HIV-infected patients.

Acquired Immunodeficiency Syndrome↗
PubMed1995

At convenience and systematic random sampling: effects on the prognostic value of nuclear area assessments in breast cancer patients.

This study compares the influence of two different nuclear sampling methods on the prognostic value of assessments of mean and standard deviation of nuclear area (MNA, SDNA) in 191 consecutive invasive breast cancer patients with long term follow up. The first sampling method used was 'at convenience' sampling (ACS); the second, systematic random sampling (SRS). Both sampling methods were tested with a sample size of 50 nuclei (ACS-50 and SRS-50). To determine whether, besides the sampling methods, sample size had impact on prognostic value as well, the SRS method was also tested using a sample size of 100 nuclei (SRS-100). SDNA values were systematically lower for ACS, obviously due to (unconsciously) not including small and large nuclei. Testing prognostic value of a series of cut off points, MNA and SDNA values assessed by the SRS method were prognostically significantly stronger than the values obtained by the ACS method. This was confirmed in Cox regression analysis. For the MNA, the Mantel-Cox p-values from SRS-50 and SRS-100 measurements were not significantly different. However, for the SDNA, SRS-100 yielded significantly lower p-values than SRS-50. In conclusion, compared with the 'at convenience' nuclear sampling method, systematic random sampling of nuclei is not only superior with respect to reproducibility of results, but also provides a better prognostic value in patients with invasive breast cancer.

Biopsy↗
PubMed1989

Comparison of flagging, walking, trapping, and collecting from hosts as sampling methods for northern deer ticks, Ixodes dammini, and lone-star ticks, Amblyomma americanum (Acari:Ixodidae).

Ticks were sampled by flagging, collecting from the investigator's clothing (walking samples), trapping with dry-ice bait, and collecting from mammal hosts on Fire Island, NY, U.S.A. The habitat distribution of adult deer ticks, Ixodes dammini, was the same in simultaneous collections from the investigator's clothing and from muslin flags. Walking and flagging samples can both be biased by differences between investigators, so the same person should do comparative samples whenever possible. Walking samples probably give a more accurate estimate than flagging samples of the human risk of encountering ticks. However, ticks (such as immature I. dammini) that seek hosts in leaf litter and ground-level vegetation are poorly sampled by walking collections. These ticks can be sampled by flagging at ground level. Dry-ice-baited tick-traps caught far more lone-star ticks, Amblyomma americanum, than deer ticks, even in areas where deer ticks predominated in flagging samples. In comparisons of tick mobility in the lab, nymphal A. americanum were more mobile than nymphal I. dammini in 84% of the trials. Therefore, the trapping bias may result from increased trap encounter due to more rapid movement by A. americanum, although greater attraction to carbon dioxide may also play a role. Tick traps are useful for intraspecific between-habitat comparisons. Early in their seasonal activity period, larval I. dammini were better represented in collections from mouse hosts than in flagging samples. Apparently, sampling from favored hosts can detect ticks at low population levels, but often cannot be used to get accurate estimates of pathogen prevalence in questing ticks.

Animals↗
PubMed1993

Influence of blood sampling from venipunctures and catheter systems on serial determinations of prothrombin activation fragment 1 + 2 and thrombin-antithrombin III complex.

To evaluate the influence of different blood sampling techniques on test results of thrombin-antithrombin III complex (TAT) and prothrombin fragment 1 + 2 (F1 + 2) serial determinations were performed. In six groups of nonrandomized patients (ten patients each) the concentrations of the coagulation markers of blood samples from central catheters (internal jugular, caval, Shaldon, pulmonary artery) and peripheral cannulas (17G and 18G) were compared with those of blood samples obtained simultaneously from direct venipunctures of the contralateral arm. Medians and 25th-75th percentiles of TAT and F1 + 2 concentrations of plasmas obtained from central catheters were not different from those taken from venipunctures. When delta mean values (catheter - venipuncture) were calculated negative results were obtained, indicating lower concentrations measured from blood sampled through central catheters with the exception of blood that taken from Shaldon catheters. Only for TAT concentrations significantly were lower values measured in blood samples taken from internal jugular catheters when compared with blood samples obtained from direct venipunctures. Significantly higher TAT concentrations were determined in blood samples obtained from Shaldon catheters. For both coagulation markers correlations were found between concentrations in blood samples from central catheters and venipunctures. In blood samples taken from peripheral venous cannulas only F1 + 2 concentrations correlated with the concentrations found in samples from direct venipuncture. In contrast to F1 + 2, TAT concentrations measured from blood samples via peripheral cannulas were determined significantly higher than those taken from direct venipunctures.(ABSTRACT TRUNCATED AT 250 WORDS)

Antithrombin III↗
PubMed1995

Detection of Legionella DNA in human and guinea pig urine samples by the polymerase chain reaction.

A detection system for Legionella DNA in urine samples based on the polymerase chain reaction (PCR) was developed and tested on infected guinea pigs and patients suffering from pneumonia. Results were compared with standard methods for diagnosis of Legionnaires' disease. A primer system was selected which amplifies a 108 bp DNA fragment of the 5S rRNA gene. The sensitivity of the PCR system was one femtogram of extracted Legionella DNA. Three methods were tested for pretreatment of urine samples. Of these, the Geneclean II kit (Bio 101, USA) gave the best results for artificially contaminated urine samples as well as those from infected guinea pigs or patients. Thirty-seven urine samples from 15 guinea pigs intraperitoneally infected with either Legionella pneumophila serogroup 1, 3 and 6 or Legionella micdadei, 26 urine samples of 21 patients suffering from pneumonia, and 30 control samples of patients with urinary tract infection (UTI) were tested. Legionella DNA was detected in 29 of the guinea pig urine samples; whereas, urinary antigen detection using EIA was positive in only 20 of the samples. PCR was also positive in the samples of 11 patients with pneumonia, 9 of which were confirmed by other microbiological methods, such as culture, direct fluorescent antibody test, urinary antigen detection and antibody testing. However, of the 30 control samples from patients with UTI, three samples yielded positive results. The results demonstrate that Legionella DNA is excreted in the urine of infected individuals and that the PCR shows a higher degree of sensitivity than EIA to the detection of soluble Legionella antigen in urine.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed2004

Air sampling of organophosphate triesters using SPME under non-equilibrium conditions.

Solid phase micro-extraction (SPME) was used to collect air samples of semi-volatile organophosphate triesters, a group of compounds that are commonly used as flame retardants/plasticisers and have therefore become ubiquitous indoor air pollutants. SPME is a simple sampling technique with several major advantages, including time-efficiency and low solvent consumption. Analyte losses also tend to be relatively low. In quantitative SPME, measurements are normally taken after the analyte has reached partitioning equilibrium between the fibre and the sample matrix. However, equilibrium sampling of semi-volatile compounds in air with SPME often takes several hours. Clearly, time-weighted average (TWA) sampling using SPME under non-equilibrium conditions could be considerably faster. So, in this study, the possibility of sampling organophosphate triesters under non-equilibrium conditions was tested. The most important variables proved to be the fibre coating and the air velocity during sampling. The highest uptake rate was obtained with polydimethylsiloxane (PDMS, 100 microm). The rate for this fibre was 150-fold higher than obtained with PDMS/DVB and Carbowax/DVB, both 65 microm. Contrary to theoretical expectations, the uptake rate appeared to be constant for all tested air velocities over the fibre surface >7 cm/s. These findings suggest that the uptake rate for non-equilibrium SPME sampling is independent of the sampling flow above this flow rate, which would considerably enhance the robustness and flexibility of the method. Applying this method for TWA sampling, with sampling periods of 1 h, detection limits lower than 2 ng/m(3) for individual organophosphate esters were obtained.

Journal Article↗
PubMed2006

Function approximation and documentation of sampling data using artificial neural networks.

Biodiversity studies in ecology often begin with the fitting and documentation of sampling data. This study is conducted to make function approximation on sampling data and to document the sampling information using artificial neural network algorithms, based on the invertebrate data sampled in the irrigated rice field. Three types of sampling data, i.e., the curve species richness vs. the sample size, the curve rarefaction, and the curve mean abundance of newly sampled species vs.the sample size, are fitted and documented using BP (Backpropagation) network and RBF (Radial Basis Function) network. As the comparisons, The Arrhenius model, and rarefaction model, and power function are tested for their ability to fit these data. The results show that the BP network and RBF network fit the data better than these models with smaller errors. BP network and RBF network can fit non-linear functions (sampling data) with specified accuracy and don't require mathematical assumptions. In addition to the interpolation, BP network is used to extrapolate the functions and the asymptote of the sampling data can be drawn. BP network cost a longer time to train the network and the results are always less stable compared to the RBF network. RBF network require more neurons to fit functions and generally it may not be used to extrapolate the functions. The mathematical function for sampling data can be exactly fitted using artificial neural network algorithms by adjusting the desired accuracy and maximum iterations. The total numbers of functional species of invertebrates in the tropical irrigated rice field are extrapolated as 140 to 149 using trained BP network, which are similar to the observed richness.

Algorithms↗
PubMed1988

Bronchoalveolar lavage sampling of airway and alveolar cells.

Bronchoalveolar lavage (BAL) cell counts are used to assess 'alveolitis' in patients with interstitial lung diseases (ILD) but inflammatory cells from airways can contribute to the differential cell count. To determine what BAL volume samples airway cells in patients with ILD we measured the proportion of bronchial epithelial cells (BECs) in four successive 25 ml aliquots in a single lung subsegment in 23 patients with ILD (cryptogenic fibrosing alveolitis (CFA) four, rheumatoid lung (RL) three, asbestosis (ASB) 11, sarcoidosis (SARC) five). Cells recovered from the first two 25 ml lavages exhibited higher proportions of BECs (15 +/- 4% and 9 +/- 2% respectively) than those from the remaining two aliquots (3 +/- 1%, 3 +/- 1%, each P less than 0.01), suggesting that the first 50 ml BAL preferentially samples airway cells compared to the second 50 ml BAL. To evaluate airway and alveolar inflammatory cell proportions in ILD we performed two separate 50 ml BALs (samples I and II) in a single subsegment in 38 patients with ILD (CFA seven, RL five, ASB 19, SARC seven) and measured the proportions of recovered cells in each sample separately and combined. Seven control individuals were also studied. Sample I contained 1-67% (mean 26 +/- 3%) of the total recovered cells. Neutrophil (PMN) proportions were higher in sample I compared to sample II in CFA (20 +/- 6 vs 8 +/- 2%), RL (30 +/- 9 vs 8 +/- 2%) and ASB (12 +/- 2 vs 7 +/- 1%), P less than 0.05 for each, but were similar in samples I and II in patients with SARC (3 +/- 1 vs 2 +/- 1%) and controls (2 +/- 1 vs 2 +/- 1%). In combined samples (I + II), absolute PMN proportions were up to 8% higher than in sample II alone whereas absolute lymphocyte proportions were up to 8% less than in sample II alone. These data suggest that separate processing of the fluid recovered from the first 50 ml BAL in ILD patients provides information on the location of inflammatory cells and improves the accuracy of BAL cell counts.

Adult↗
PubMed1995

Stability of 1-nitropyrene and 1,6-dinitropyrene in environmental water samples and soil suspensions.

This study examined the stability of mutagenic 1-nitropyrene (1-NP) and (1,6-dinitropyrene (1,6-diNP) in environmental water samples and various soil suspensions containing 0.1% peptone and in water samples containing no peptone. The water samples or the soil suspensions were mixed with NPs and incubated at 30 degrees C. The stability of NPs was expressed as mutagenic activity remaining in the test solutions. The mutagenicity decreased rapidly when 1-NP or 1,6-diNP was incubated in unautoclaved test solutions containing 0.1% peptone but not when incubated in autoclaved test solutions. The mutagenicity in the soil suspensions, especially in the sludge, decreased faster than in the water samples. This was due to the large number of colony-forming units (CFU) in the soil suspensions. In the water samples containing 0.1% peptone, the mutagenicity of NPs in the polluted Tamiya River water decreased faster than in the unpolluted Yoshino River water. The rate of decrease was dependent on the number of CFU in the water samples. A large number of CFU decreased the mutagenicity more rapidly than did a small number of CFU in samples. The disappearance of mutagenicity was dependent on the initial concentrations of NPs. The periods required for a 50% decrease in the mutagenicity of 1-NP at the low concentration (0.2 microgram/ml) was shorter than that at the high concentration (3 micrograms/ml). 1-Aminopyrene was detected in the 1-NP test solution after incubation when it was analyzed by high-pressure liquid chromatography. In the water samples containing no peptone, the mutagenicity of 1-NP (0.2 microgram/ml) decreased gradually during 30 days of incubation. After incubation for 1540 days, the remaining mutagenicity of 1-NP in the water samples was almost the same as that in autoclaved water samples. On the other hand, the mutagenicity of 1,6-diNP (10 ng/ml) decreased and the remaining mutagenicity, except in the Yoshino River water, was less than 20% after 30 days of incubation and was completely lost during the 1540-day incubation. However, the mutagenicity of 1,6-diNP in autoclaved water samples was very stable and almost all mutagenicity, except in sea water, remained after 1540 days of incubation at 30 degrees C. These results suggest that the microflora in the environment plays an important role in the primary degradation and decontamination of relatively low concentrations of NPs.

Biodegradation, Environmental↗
PubMed1996

Accuracy of the one-sample method for determination of antipyrine clearance in elderly subjects.

The purpose of this study was to evaluate the validity of the one-sample abbreviated method for determination of the pharmacokinetic parameters of antipyrine in the elderly. Antipyrine pharmacokinetics were studied in 15 elderly women (mean age 86 years). Antipyrine (1 g) was administered orally and pharmacokinetic parameters were determined by the one-sample (24 h) and multiple-sample (3, 6, 9, 12 and 24 h) methods. Mean antipyrine clearance for the one-sample study (19.72 +/- 1.51) was almost identical to that obtained with the multiple-sample approach (20.73 +/- 1.57), and the two methods were very well correlated (r = 0.989). Relative standard deviations between individual clearances values for multiple-sample vs. one-sample studies averaged 1.6%. Values of elimination half-life were likewise very similar for the abbreviated (17.41 +/- 1.21) and complete (17.99 +/- 1.09) methods, with a significant correlation (r = 0.857). Although values were underestimated by 10% in the one-sample approach, no difference in the volume of distribution with the multiple-sample study was observed. When the unbiased volume of distribution value was determined from the total elimination curve against time, the influence of biased volume of distribution resulted in a 5.1% deviation in antipyrine clearance in the one sample method. The findings indicate that antipyrine pharmacokinetic parameters can be estimated with reasonable precision and accuracy in the elderly using a simplified one-sample procedure.

Administration, Oral↗
PubMed2006

Operator experience and sample quality in genetic amniocentesis.

OBJECTIVE: We sought to relate the frequency of maternal cell contamination in amniotic fluid samples that were submitted to a single laboratory for cytogenetic analysis to the experience and training of the physician who performed the amniocentesis. STUDY DESIGN: We reviewed the database of a single cytogenetics laboratory to compare the number of amniocenteses that were performed annually per physician to the rate of maternal cell contamination in genetic amniocentesis samples. Only samples that resulted in a 46 XY male karyotype were studied so that maternal cell contamination could be identified as having occurred when the karyotype revealed > or = 1 cell with 2 X chromosomes. Samples were categorized as being submitted by a physician who submitted > or = 50 or more samples annually versus < 50 samples to this laboratory. The frequency of maternal cell contamination was compared with annual operator volume with 2 x 2 tables and analyzed by chi-squared testing. RESULTS: Between 2000 and 2004, the laboratory received 6332 mid-trimester amniotic fluid samples that generated a male karyotype result. Fourteen of 2081 samples (0.67%) that were submitted by physicians who submitted < 50 samples grew > or = 1 46 XX cells, compared with 8 of 4251 samples (0.19%; chi-squared, 9.47; degrees of freedom, 1; P = .0021). CONCLUSION: Maternal cell contamination occurs more frequently in genetic amniocentesis samples that are obtained by physicians who perform < 50 genetic amniocenteses annually.

Amniocentesis↗
PubMed2006

Characterization and classification of complex PAH samples using GC-qMS and GC-TOFMS.

The aim of this study was to compare the polycyclic aromatic hydrocarbon (PAH) contents in a number of complex samples, including soil samples from industrial sites, anti-skid sand, urban dust and ash samples from municipal solid waste incinerators. The samples were characterized by routine analysis of PAHs (gas chromatography-quadrupole mass spectrometry) and gas chromatography-time of flight mass spectrometry (GC-TOFMS). Classification of the samples by principal component analysis (PCA) according to their composition of PAHs revealed that samples associated with traffic and the municipal incinerator formed homogeneous clusters, while the PAH-contaminated soils clustered in separate groups. Using spectral data to resolve co-eluting chromatographic peaks, 962 peaks could be identified in the GC-TOFMS analysis of a pooled sample and 123-527 peaks in the individual samples. Many of the studied extracts included a unique set of chemicals, indicating that they had a much more diverse contamination profile than their PAH contents suggested. Compared to routine analysis, GC-TOFMS provided more detailed information about each sample and in this study a large number of alkylated PAHs were found to be associated with the corresponding unsubstituted PAHs. The possibility to filter peaks according to different criteria (e.g. to include only peaks that were detected in the analysis of another sample) was explored and used to identify unique as well as common compounds within samples. This procedure could prove to be valuable for obtaining relevant chemical data for use in conjunction with results from various biological test systems.

Gas Chromatography-Mass Spectrometry↗
PubMed2006

Multiwalled carbon nanotubes coated fibers for solid-phase microextraction of polybrominated diphenyl ethers in water and milk samples before gas chromatography with electron-capture detection.

Determination of polybrominated diphenyl ethers (PBDEs) in environmental samples has raised great concerns due to the widespread use of PBDEs and their potential risk to humans. Solid-phase microextraction (SPME) is a fast, simple, cost-effective, and green sample preparation technique and is widely used for environmental analysis, but reports on the application of SPME for determination of PBDEs are very limited, and only a few publications dealing with commercial SPME fibers are available for extraction of PBDEs. Herein, we report a novel SPME method using multiwalled carbon nanotubes (MWCNTs) as the SPME fiber coating for gas chromatography with electron-capture detection (GC-ECD) of PBDEs in environmental samples. The MWCNTs coating gave much higher enhancement factors (616-1756) than poly (5% dibenzene-95% dimethylsiloxane) coating (139-384) and activated carbon coating (193-423). Thirty-minute extraction of 10 mL of sample solution using the MWCNTs coated fiber for GC-ECD determination yielded the limits of detection of 3.6-8.6 ng L(-1) and exhibited good linearity of the calibration functions (r(2)>0.995). The precision (RSD%, n=4) for peak area and retention time at the 500 ng L(-1) level was 6.9-8.8% and 0.6-0.9%, respectively. The developed method was successfully applied for the analysis of real samples including local river water, wastewater, and milk samples. The recovery of the PBDEs at 500 ng L(-1) spiked in these samples ranged from 90 to 119%. No PBDEs were detected in the river water and skimmed milk samples, whereas in the wastewater sample, 134-215 ng L(-1) of PBDEs were found. The PBDEs were detected in all whole fat milk samples, ranging from 13 to 484 ng L(-1). In a semiskimmed milk sample, only BDE-47 was found at 21 ng L(-1).

Animals↗