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PubMed1984

On the abiotic formation of amino acids. I. HCN as a precursor of amino acids detected in extracts of lunar samples. II. Formation of HCN and amino acids from simulated mixtures of gases released from lunar samples.

Two studies on the abiotic formation of amino acids are presented. The first study demonstrates the role of hydrogen cyanide as a precursor of amino acids detected in extracts of lunar samples. The formation of several amino acids, including glycine, alanine, aspartic acid, and glutamic acid, under conditions similar to those used for the analysis of lunar samples is demonstrated. The second study investigates the formation of hydrogen cyanide as well as amino acids from lunar-sample gas mixtures under electrical discharge conditions. These results extend the possibility of synthesis of amino acids to planetary bodies with primordial atmospheres less reducing than a mixture of methane, ammonia, hydrogen and water.

Amino Acids↗
PubMed1999

Polyatomics in zinc isotope ratio analysis of plasma samples by inductively coupled plasma-mass spectrometry and applicability of nonextracted samples for zinc kinetics.

Inductively coupled plasma-mass spectrometry (ICP-MS) is a powerful tool for both quantitative multielement analyses of inorganic elements and measurement of isotope ratios (IRs). The main disadvantage of this technique is the existence of polyatomic isobaric interferences at some key masses. Zinc has been investigated for such potential interferences in serum or plasma. The Zn isotopes, 66Zn and 68Zn, have no apparent interferences, but 32S1602 and 32S2 are isobaric with 64Zn. The possible effects of S and other major components of blood plasma-Na, K, Cl, P, Ca-on Zn IRs were investigated using a series of mineral solutions which simulated human plasma with respect to these elements. The mixture of all mineral elements interfered only with 64Zn (6.66 ng/mL) and 70Zn (8.51 ng/mL). Interferences to 66Zn, 67Zn, and 68Zn were minimal containing 0.90, 0.94, and 0.39 ng/mL, respectively. The copresence of Na or S shifted 35Cl16O2 (atomic mass 67 coming from Cl solution) to 35Cl2 which reduced the contribution to 67Zn. The hypothesis that Zn IRs obtained from plasma at various intervals after the intravenous administration of enriched 67Zn to humans would reflect those obtained after extraction of Zn was therefore tested. To compare the two pretreatment methods, "extraction" versus "nonextraction," specimens were collected from 10 human subjects at intervals of 5 min to 24 h postinjection, and in 4 subjects from 5 min to 9 d postinjection. Two separate aliquots of plasma from each time-point were dried and digested with hydrogen peroxide, and the residue dissolved in nitric acid. One specimen was subjected to zinc extraction using ammonium diethyldithiocarbamate chelate followed by back extraction into nitric acid. The matching aliquot received no further pretreatment. The normalized IRs obtained from 67Zn/66Zn and 67Zn/68Zn in both the "extracted" and "nonextracted" samples agreed well (r2 = 0.976 and r2 = 0.985, respectively) compared to those from other ratios (r2 = 0.838 for 67Zn/64Zn and r2 = 0.747 for 67Zn/70Zn). Considering the minimum possibility of isobaric interferences in plasma samples, 67Zn/68Zn obtained from "nonextracted" samples is sufficient for routine Zn kinetic analysis by ICP-MS.

Argon↗
PubMed2001

Sampling and processing of biopsy samples for speciation studies of cytosolic metalloproteins.

Studies to specify various metalloproteins in cell cytosol of tissues using chromatographic separation methods and plasma mass spectrometry for element detection require a careful step by step sample preparation. These steps involve (i) bioptic sample removal from tissue, (ii) extraction and preparation of the tissue supernatant, (iii) the chromatographic separation of the proteins, and finally (iv) the on-line transfer of the column eluate into the plasma mass spectrometer. Each of the analytical steps has to be carefully monitored to avoid undesired changes in the sample composition which could be caused by enzymatic and/or oxidative processes as well as by external element contamination. This presentation introduces a concept to ensure that environmental element contamination does not occur to bias the analytical results.

Animals↗
PubMed2005

Double-layer Tedlar bags: a means to limit humidity evolution of air samples and to dry humid air samples.

Tedlar bags, which are widely used to collect air samples, especially VOCs and odorous atmospheres, can allow humidity to diffuse when relative humidity levels differ between the inside and outside. Starting with dry air inside the bag and humid air outside, we monitored equilibrium times under several conditions showing the evolution and influence of collected volumes and exposed surfaces. A double-film Tedlar bag was made, to limit the impact of external humidity on a sample at low humidity level. With the addition of a drying agent between both films, the evolution of humidity of a sample can be stopped for several hours. When a VOC mixture was monitored in a humid atmosphere, humidity was decreased but no significant evolution of VOC concentrations was observed.

Journal Article↗
PubMed2000

Rapid determination of lead and cadmium in sewage sludge samples using electrothermal atomic absorption spectrometry with slurry sample introduction.

Lead and cadmium concentrations in sewage sludge samples are determined by suspending the ground samples in a solution containing 10% (v/v) concentrated hydrofluoric acid, 1% (v/v) concentrated nitric acid, 0.5% (m/v) dihydrogen ammonium phosphate and 0.1% (m/v) sodium hexametaphosphate. Aliquots of 20 microL of these suspensions (4 mg/mL) are diluted to 1000 microL with the same solution and then injected into the electrothermal atomizer. The drying stage is performed by programming a 400 degrees C temperature, a ramp time of 20 s and a hold time of 15 s on the power supply of the atomizer. No ashing step is used. Platform atomization is carried out at 1600 and 1800 degrees C for Pb and Cd, respectively. Calibration is performed using aqueous standards in the 5-75 and 0.2-5 microg/L Pb and Cd ranges, respectively. Results obtained for three certified reference materials and four samples demonstrate the reliability of the procedures described.

Cadmium↗
PubMed1983

A high-sampling-rate automated continuous-flow fluorometric technique for the analysis of nanogram levels of histamine in biological samples.

An automated continuous-flow technique of the modified fluorometric method of Shore was devised to obtain a high sampling rate (60/h) and a sensitive measurement of the histamine content of biological samples. The volumes of samples range from 50 to 500 microliter. A linear relationship is obtained from 0 to 5 micrograms/ml (histamine base) with a good specificity. The limit of detection is 25 pg (actual amount). The coefficient of variation is less than or equal to +/- 5% for concentrations of less than 2 ng/ml and from +/- 0.2 to +/- 2% for higher concentrations. With this technique more sensitive, more specific, and twice as fast as similar ones, histamine content in 350-400 unknowns can be measured routinely in a working day. It has been used for more than 4 years and has proven to be a reliable and useful tool for the numerous research studies in which histamine is involved: immunology, allergy, pharmacology, dermatology, cancer, nutrition.

Basophils↗
PubMed1993

Sampling and sample handling--crucial steps in process monitoring and control.

Sampling and sample handling are important considerations in the design of monitoring and control systems for bioreactors. Many factors must be considered in developing strategies for obtaining representative samples, thus ensuring that the status of the bioprocess can be evaluated rapidly, in a reproducible and reliable manner.

Biotechnology↗
PubMed2004

High sensitivity analysis of nitrite and nitrate in biological samples by capillary zone electrophoresis with transient isotachophoretic sample stacking.

Tissue level of nitrate and nitrite are established indicators of altered nitric oxide metabolism under various pathological conditions. Determination of these anions in biological samples, in the presence of high chloride concentration, using capillary zone electrophoresis suffers from poor detection sensitivity. Separation conditions providing excellent resolution and submicromolar detection sensitivity of nitrate and nitrite have been developed and validated. Simple sample preparation was applied that maintains nitrite stability in tissue extracts and at the same time allows transient isotachophoresis stacking of the analytes. Nitrate and nitrite concentrations in rat brain and liver tissue samples were determined in control and lipopolysaccharide treated animals.

Animals↗
PubMed2006

Instability of calcium channel antagonists during sample preparation for LC-MS-MS analysis of serum samples.

1,4-Dihydropyridines calcium channel antagonists (1,4-DHP CCAs) are photolabile and the products of their photodecomposition have no pharmaceutical activity. In our previous work we have presented a screening procedure for eleven 1,4-DHPs in plasma by LC-MS-MS using multiple reaction motoring. The laboratory process includes preparation and storage of stock solutions, plasma storage, solid-phase extraction, reconstitution of extracts and storage time in an autosampler for LC-MS-MS analysis. Prior to validation of the analytical procedure, we have tested the stability of these compounds by exposure to light. Methanolic solutions have been exposed to laboratory and UV light and the stability of the compounds in plasma was tested by exposure of spiked plasma samples to laboratory light at room temperature. Stability during freeze-thaw cycles and stability during 2 month storage at -20 degrees C have been tested as well. Products of photodecomposition have been identified after forced degradation and the degree of degradation has been quantified using LC-UV-DAD and LC-MS-MS, respectively. A 96% degradation after only 2h has been observed when solutions of nifedipine or nisoldipine were exposed to laboratory light in clear glass vials. In plasma samples degradation was 25% in only 2h for both compounds. The main degradation product was produced by oxidation of the dihydropyridinic ring resulting in the pyridine analogue that has been described as the first metabolite in the metabolic pathway. Only minor degradation was found for the other tested compounds after 2h light exposure in methanolic solutions. Furthermore, lercanidipine and nicardipine were also degradated by esterhydrolysis. Several additional minor degradation products were found for the other tested 1,4-DHPs, however, some of them could not be identified. Preconditions for storage and handling of plasma samples prior to and during analysis for 1,4-DHP CCAs are suggested in order to avoid photodecomposition of the analytes.

Calcium Channel Blockers↗
PubMed2004

Determination of dihydroergocryptine in human plasma and urine samples using on-line sample extraction-column-switching reversed-phase liquid chromatography-mass spectrometry.

A rapid and sensitive assay for the determination of dihydroergocryptine (DHEC) in human plasma and urine samples with dihydroergotamine (DHET) as the internal standard was developed. The procedure employs on-line sample preparation using an extraction pre-column and an octadecylsilylsilica (ODS) analytical column. After centrifugation human plasma or urine were injected onto the pre-column, concentrated and extracted, back-flushed onto the analytical column and eluted with a binary methanol--aqueous formic acid gradient. Either determination of DHEC as well of its mono- and dihydroxy-metabolites was performed by measurement of the signal responses from MS detection in the selected reaction monitoring (SRM) mode using the transition of the respective parent ions to the common daughter ion at m/z=270.2 amu. The limit of quantitation (LOQ) for determinations of DHEC in both plasma and urine were 25 pg/ml for injected sample volumes of 400 microl. Proportionality of signal responses versus concentration was accomplished within the range of 25-1000 pg/ml. Recovery of target analyte from plasma was 99%. Mean values of the coefficients of variation (CV) for the target analyte in plasma ranged from 1.7 to 13.8% (within-day) and 5.0 to 9.1% (between-day) and accuracy from 91.7 to 102.6% for the within-day and from 95.8 to 98.8% for the between-day measurements. The corresponding values for determinations in urine were 1.7-14.5% (within-day) and 5.3-11.8% (between-day) for CV and 95.8-110.7% (within-day) and 100.1-104.6% (between-day) for accuracy.

Chromatography, High Pressure Liquid↗
PubMed2006

Determination of the DNA methylation level of the marbled crayfish: an increase in sample throughput by an optimised sample preparation.

Using a previously described capillary electrophoretic method with laser-induced fluorescence detection the genomic methylation level can be determined exactly. We present a sample preparation that eliminates the surplus of fluorescence marker used for coupling resulting in an increase of sample throughput from 75 to 250 analyses per week. The sensitivity of the method was also increased, which allows the determination of methylation levels under 1%. With these changes in sample preparation a methylation level of 1.64+/-0.03% in hepatopancreas DNA of the recently discovered marbled crayfish could be determined.

Animals↗
PubMed2006

Pneumatic tube delivery system for blood samples reduces turnaround times without affecting sample quality.

STUDY OBJECTIVES: In this study, blood samples from ED patients that were delivered to the laboratory by a pneumatic tube delivery system and by a human courier were compared for timeliness and quality of results. METHODS: We studied all consecutive measurements of serum hemoglobin and potassium ordered from 2 emergency departments of a multisite tertiary care hospital system, one with a pneumatic tube system and the other using human couriers. Turnaround time was measured from the time that the test was ordered by the physician to the time the result was reported on the hospital information system. Hemolysis was measured with use of a standardized, validated method. ANALYSIS: Times were normalized by log transformation (ln [minutes + 1]), and a comparison of sites was conducted using analysis of variance. Hemolysis rates of the 2 delivery systems were compared by chi2. RESULTS: There was no significant difference in hemolysis rate between the 2 methods of delivery (7/121 [5.79%] with a pneumatic tube system and 20/200 [10%] with a human courier). When delivered with a pneumatic tube system, the mean turnaround times (with ranges) for both hemoglobin (33 minutes [4-230]) and potassium (64 [34-208]) were shorter than those delivered by a human courier (43 minutes [3-150] and 72 [28-213], respectively). CONCLUSION: The use of a pneumatic tube delivery system for transporting blood samples from the emergency department to the laboratory can significantly reduce the turnaround times of results without a reduction in sample quality.

Blood Specimen Collection↗
PubMed2006

The use of slurry sampling for the determination of manganese and copper in various samples by electrothermal atomic absorption spectrometry.

Manganese and copper in multivitamin-mineral supplements and standard reference materials were determined by slurry sampling electrothermal atomic absorption spectrometry. Slurries were prepared in an aqueous solution containing Triton X-100. The effects of different parameters such as ratio of solid to liquid phase volume, total slurry volume and addition of Triton X-100 as a dispersant on the analytical results were investigated. The graphite furnace programs were optimized for slurry sampling depending on the analytes and their concentrations in the samples. The linear calibration method with aqueous standard solutions was used for the quantification. At optimum experimental conditions, R.S.D. values were below 5%. The analytes were determined in the limits of 95% confidence level with respect to certified values in coal and soil standard reference materials and to those found by wet-digestion in multivitamin-mineral supplements. Detection limits (3delta) for Mn and Cu were 0.10 microg L(-1) and 1.82 microg L(-1) for 10 microL coal standard reference material slurry, respectively.

Copper↗
PubMed2005

Monitoring air sampling in operating theatres: can particle counting replace microbiological sampling?

Microbiological contamination of air in the operating room is generally considered to be a risk factor for surgical site infections in clean surgery. Evaluation of the quality of air in operating theatres can be performed routinely by microbiological sampling and particle counting, but the relationship between these two methods has rarely been evaluated. The aim of this study was to determine whether particle counting could be predictive of microbiological contamination of air in operating rooms. Over a three-month period, air microbiological sampling and particle counting were performed simultaneously in four empty operating rooms belonging to two surgical theatres equipped with conventional ventilation via high-efficiency particulate air filters. Correlation between the two methods was measured with Spearman's correlation coefficient. The ability of particle counting to discriminate between microbiological counting values higher and lower than 5 colony-forming units (CFU)/m3 was evaluated using receiver-operating characteristic (ROC) analysis. Microbiological counting ranged from 0 to 38CFU/m3, while the particle counts ranged from 0 to 46 262/m3. Methods of microbiological and particle counting did not correlate (Spearman correlation coefficient=0.06, P=0.6). Using the ROC curve, no particle count value could be predictive of a microbiological count higher than 5CFU/m3. The results of the current study suggest that there is no reason to replace microbiological sampling with particle counting for routine evaluation of microbiological contamination in conventionally ventilated operating theatres.

Air Microbiology↗
PubMed2005

Effects of intraoperative fluid infusions, sample storage time, and sample handling on unbound propofol assay in human blood plasma.

Free drug assay in physiological fluids is getting more and more attention nowadays. The principal reason is the fact that the unbound drug form is responsible for the therapeutic or toxic effects of its application. Unbound drug concentration significantly depends on the extent of its binding by plasma. This article describes the influence of different factors on unbound propofol concentration. These factors are presence of infusion fluids in blood, type of anticoagulant, sample storage time and plasma freezing. The following conclusions result from the experiments carried out: 1. The lowest free drug fractions are observed in samples containing carbohydrate infusion fluids. The free drug percentage is virtually independent of its total concentration in the range of clinically relevant concentrations. 2. There is no evident anticoagulant influence (heparin, citrate, EDTA and oxalate) on free propofol level in plasma samples. 3. Longer storage of plasma at 4 degrees C causes a slight rise of free propofol concentration in heparinised plasma and no evident changes in plasma containing citrate. 4. Plasma freezing induces the increase of free drug concentration both for citrate and heparin. These findings are valuable both for clinicists and pharmacologists, and important for chemical analysts.

Drug Storage↗
PubMed2002

New sample preparation technique for the determination of avoparcin in pressurized hot water extracts from kidney samples.

A new approach is presented for the determination of avoparcin in tissue. Complete recovery from spiked swine kidney was achieved with hot water modified with 30% ethanol (v/v). The samples were extracted at 75 degrees C and 50 atm by accelerated solvent extraction. In situ sample clean-up was achieved by using matrix solid-phase dispersion utilizing the acrylic polymer XAD-7 HP, and by adding triethylammonium phosphate (TEAP) to the extraction solvent. The aqueous extracts were concentrated by solid-phase extraction (SPE) on the hydrophilic interaction chromatography (HILIC) material polyhydroxyethyl aspartamide. Complete analyte retention was possible during SPE when the kidney extracts were modified with 70% ethanol. A 200 A, 5 microm HILIC column with UV225 detection was used for the separation of avoparcin. The retention time was less than 15 min with 47% aqueous component in acetonitrile and 15 mM TEAP as eluent. The average recovery of avoparcin from kidney samples was 108%.

Animals↗
PubMed1998

Assessment of the sample handling procedures in a labor-saving method for the analysis of organochlorine compounds in a large number of fish samples.

A rapid single step clean-up procedure with sulphuric acid oxidation for lipid removal has been assessed by a step-by-step recovery approach for its performance in the analysis of organochlorinated compounds in large numbers of fish samples (muscle). Recovery decreases are essentially due to losses by evaporation but their effect is compensated by correction of the recovery factor of tetrabromobenzene that is used as surrogate. Sample grounding with sodium sulphate provides significant higher concentrations than freeze-drying. Soxhlet extraction for 18 h is sufficient to draw most organochlorine compounds from the samples. Repeatability and reproducibility is smaller than the dispersion between fish of similar length and age from the same lake for all compounds except alpha-hexachlorocyclohexane.

Animals↗
PubMed1999

Visualization of sample introduction in liquid chromatographic columns. Contribution of a flow distributor on the sample band shape.

The contributions to the radial distribution of the sample concentration across the column inlet and to the axial band dispersion resulting from a column header containing a distributor were evaluated using a band-visualization process entailing matching the refractive indices of the stationary and mobile phases in a glass column. This study illustrates graphically how a distributor fitted to the column can increase the axial dispersion of the sample band compared to an inlet containing only a frit. The distributor did not provide a uniform sample distribution across the column. In fact, for 17-mm inner diameter columns and high-porosity frits, the distribution was no better than with the frit having no distributor. However, when low-porosity frits were employed, improved peak shapes were obtained with a distributor. In addition, we observed that the inlet header configuration influenced dramatically the flow stream established along the column. The radial distribution of the efficiency of the columns was nearly homogeneous for those having only a frit but not for those having also a distributor. For the latter, the efficiency decreased from the column axis to its wall.

Chemical Phenomena↗