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At least 127 records · Page 7Linked to original sources

A rapid sample preparation method for the HPLC determination of the opioid antagonist naltrexone in serum.

HPLC with UV and electrochemical detection has routinely been employed for the determination of the opioid antagonist naltrexone in serum. Sample preparation protocols range from liquid/liquid to solid phase extraction. The sample preparation described in this communication uses ultrafiltration as the mode of sample preparation prior to HPLC analysis. The method is accurate, precise and saves considerable time compared to previously published techniques.

Chromatography, High Pressure Liquid↗

Sampling and sample preparation for detection and quantitation of natural toxicants in food and feed.

The primary goal of a sampling plan for natural toxins, i.e., mycotoxins and seafood toxins, is to obtain a sample that accurately represents the concentrations of individual components of a given lot. Factors affecting the ability of the sampling plan to accomplish this goal include: (1) nature of the analyte of interest; (2) distribution of the analyte throughout the lot, (3) physical characteristics of the product, (4) accessibility of the product to random representative sampling, (5) sampling procedure, and (6) size of sample. Sampling plans are composed of 3 distinct components: (a) sampling, (b) sample preparation, and (c) analysis. Normally, sampling contributes the largest relative error while analysis comprises the least. Automatic, continuous stream samplers provide the most representative samples for commodities such as nuts, cottonseed, and cereal grains. Good sample preparation equipment is currently available for these commodities; the use of this equipment to obtain a representative test sample is discussed.

Animal Feed↗

Quantitative determination of alpha-, beta-, gamma- and delta-tocopherols in human serum by high-performance liquid chromatography and gas chromatography-mass spectrometry as trimethylsilyl derivatives with a two-step sample preparation.

Using a two-step sample preparation with Extrelut and silica gel extraction in Pasteur pipettes it is possible to quantify all tocopherols in human serum samples by means of normal-phase HPLC with fluorescence detection (lambda(ex) 295 nm, lambda(em) 330 nm) or by GC-MS of their trimethylsilyl (TMS) derivatives. The method has been used in pharmacoepidemiological studies concerning the exposition with vitamin E-containing drugs in Germany. The recovery for all tocopherols is 98% and the limit of detection is 50 pg for alpha-tocopherol in the HPLC and 40 pg for all TMS-tocopherols in the GC-MS method using the selected ion monitoring mode with a well-tuned GCQ system. Linearity of calibration is excellent for both methods over the full physiological relevant range. Due to the low sample amount needed, the method is suitable for epidemiological and paediatric research.

Chromatography, High Pressure Liquid↗

Sampling, sample preparation, and analytical variability associated with testing wheat for deoxynivalenol.

The variability associated with testing wheat for deoxynivalenol (DON) was measured using a 0.454 kg sample, Romer mill, 25 g comminuted subsample, and the Romer Fluoroquant analytical method. The total variability was partitioned into sampling, sample preparation, and analytical variability components. Each variance component was a function of the DON concentration and equations were developed to predict each variance component using regression techniques. The effect of sample size, subsample size, and number of aliquots on reducing the variability of the DON test procedure was also determined. For the test procedure, the coefficient of variation (CV) associated with testing wheat at 5 ppm was 13.4%. The CVs associated with sampling, sample preparation, and analysis were 6.3, 10.0, and 6.3%, respectively. For the sample variation, a 0.454 kg sample was used; for the sample preparation variation, a Romer mill and a 25 g subsample were used; for the analytical variation, the Romer Fluoroquant method was used. The CVs associated with testing wheat are relatively small compared to the CV associated with testing other commodities for other mycotoxins, such as aflatoxin in peanuts. Even when the small sample size of 0.454 kg was used, the sampling variation was not the largest source of error as found in other mycotoxin test procedures.

Algorithms↗

DNA isolation and sample preparation for quantification of adduct levels by accelerator mass spectrometry.

A protocol is described for the isolation of DNA and subsequent preparation of samples for the measurement of adduct levels by accelerator mass spectrometry (AMS). AMS is a highly sensitive technique used for the quantification of adducts following exposure to carbon-14- or tritium-labeled chemicals, with detection limits in the range of one adduct per 10(11)-10(12) nucleotides. However, special precautions must be taken to avoid cross-contamination of isotope between samples and to produce a sample that is compatible with AMS. The DNA isolation method described is based on digestion of tissue with proteinase K, followed by extraction of DNA using Qiagen DNA isolation columns. DNA is then precipitated with isopropanol, washed repeatedly with 70% ethanol to remove salt, and then dissolved in water. This method has been used to generate reliably good yields of uncontaminated, pure DNA from animal and human tissues for analysis of adduct levels. For quantification of adduct levels from 14C-labeled compounds, DNA samples are then converted to graphite, and the 14C content is measured by AMS.

Animals↗

MALDI-TOF mass spectrometry of insoluble giant polycyclic aromatic hydrocarbons by a new method of sample preparation

The insolubility of giant polycyclic aromatic hydrocarbons (PAHs) prevents their characterization by conventional analytical methods, which require a solubilization of the analyte. Laser desorption mass spectrometry may be used to analyze insoluble samples but is limited to relatively low molecular weights (approximately 2000), in the case of PAHs. To overcome this limitation, we applied MALDI-TOF mass spectrometry. Since MALDI sample preparation also requires solubility of analyte and matrix molecules, the sample preparation needed modification. The giant PAHs (>2000 Da) were investigated after using a new sample preparation, consisting of mechanically mixing analyte and matrix without any solubilization procedures. This solvent-free process allows insoluble compounds to be characterized. Furthermore, new organic molecules can be used as a matrix. Indeed, 7,7,8,8-tetracyanoquinodimethane, a new matrix with promising properties, has proven to be particularly suitable for the measurement of PAHs. Thanks to the successful characterization with MALDI-TOF mass spectrometry, the chemical design of giant PAHs, which was hindered until now for a lack of analytical methods, can now continue to develop.

Journal Article↗

Rapid sample preparation method for PCR-based detection of Escherichia coli O157:H7 in ground beef.

AIM: To develop an improved, rapid and sensitive sample preparation method for PCR-based detection of Escherichia coli O157:H7 in ground beef. METHODS AND RESULTS: Fresh ground beef samples were experimentally inoculated with varying concentrations of E. coli O157:H7. PCR inhibitors were removed and bacterial cells were concentrated by filtration and centrifugation, and lysed using enzymatic digestion and successive freeze/thaw cycles. DNA was purified and concentrated via phenol/chloroform extraction and the Shiga toxin 1 gene (stx1) was amplified using PCR to evaluate the sample preparation method. Without prior enrichment of cells in broth media, the detection limit was 103 CFU g-1 beef. When a 6 h enrichment step was incorporated, the detection limit was 1 CFU g-1 beef. The total time required from beginning to end of the procedure was 12 h. CONCLUSIONS: The sample preparation method developed here enabled substantially improved sensitivity in the PCR-based detection of E. coli O157:H7 in ground beef, as compared to previous reports. SIGNIFICANCE AND IMPACT OF THE STUDY: Superb sensitivity, coupled with quick turn-around time, relative ease of use and cost-effectiveness, makes this a useful method for detecting E. coli O157:H7 in ground beef.

Animals↗

Comparison of protein precipitation methods for sample preparation prior to proteomic analysis.

Protein samples should be free of salt and other disturbing agents and have an appropriate concentration to be suitable for two-dimensional (2D) electrophoresis, the principal step of proteomics. To find the most efficient method for sample preparation, we used human plasma and compared four widely applied precipitation methods, using trichloroacetic acid (TCA), acetone, chloroform/methanol and ammonium sulfate, as well as ultrafiltration. Precipitation with TCA and acetone and ultrafiltration resulted in an efficient sample concentration and desalting. We also found that ammonium sulfate fractionation can efficiently remove albumin, which represents more than 50% of plasma proteins.

Ammonium Sulfate↗

On-line sample preparation for the determination of riboflavin and flavin mononucleotides in foodstuffs.

An on-line sample preparation method is described for the determination of riboflavin and flavin mononucleotide (FMN) in milk and cereal samples by high-performance liquid chromatography (HPLC) with fluorescence detection. The on-line system consists of microwave extraction followed by dialysis and trace enrichment with a C18 mini-column. Sample preparation was minimal, with milk samples being directly introduced into the system and cereal only needing to be ground prior to analysis. Results were obtained for a range of samples and these were found to be in agreement with the Association of Official Analytical Chemists (AOAC) method and a previously reported HPLC method. Recoveries were between 94 and 106% for a range of different samples and the relative standard deviation for ten samples was in the range 1.2-2.0%. During the microwave extraction all the flavin adenine dinucleotide (FAD) was converted into FMN and 15% of FMN was converted into riboflavin. The full analysis time on the ground samples was about 20 min.

Animals↗

Sample preparation in matrix-assisted laser desorption/ionization mass spectrometry of whole bacterial cells and the detection of high mass (>20 kDa) proteins.

Three sample preparation strategies commonly employed in matrix-assisted laser desorption/ionization mass spectrometry (MALDI-TOFMS) of whole bacterial cells were investigated for the detection of high mass signals; these included the dried droplet, the seed-layer/two-layer, and the bottom-layer methods. Different sample preparation approaches favoured the detection of high- or low-mass proteins. The low-mass peaks were best detected using the bottom-layer method. By contrast, the dried droplet method using a solvent with higher water content, and hence effecting a slower crystallization process, gave the best results for the detection of high-mass signals. Signals up to m/z 158 000 could be detected with this methodology for Bacillus sphaericus. Sodium dodecyl sulphate polyacrylamide gel electrophoresis (SDS-PAGE) analysis of the same extracts used for MALDI-TOFMS showed bands in the molecular weight range in which high-mass peaks were observed in MALDI-MS, suggesting that the high-mass signals are not polymeric adducts of low-mass protein monomers. In addition, one of the high molecular weight proteins (approximately 126 kDa) was putatively identified as an S-layer protein by an in-gel tryptic digest. The bacterial samples spotted on the target wells for MALDI-TOFMS, using the different sample preparation strategies, were examined under a scanning electron microscope and differences were observed between the different strategies, suggesting that the nature of the crystals and the distribution of the analytes amidst the crystals could influence the spectral pattern observed in MALDI-TOFMS of whole bacterial cells. Finally, evidence is presented to indicate that, although the determinants are intact cells, cell lysis occurs both before and during the MALDI process.

Bacterial Proteins↗

On-line dialysis as a sample preparation technique for ion chromatography.

The use of on-line dialysis as a sample preparation technique for ion chromatography is described. A fully automated sample preparation device coupled to an ion chromatographic system for the determination of anions and cations in various matrices is presented. The method was based on stopped-flow dialysis, where the samples were continuously dialyzed for 10 min while the acceptor solution was stationary within the recipient channel. The matrices examined, without additional sample treatment, included milk, untreated wastewater, fruit juice, engine coolant, and a multivitamin tablet. The analyte recoveries for anions and cations in various matrices ranged from 87 to 106%. In addition, multiple sample injections were performed and repeatabilities were found in the range of 0.2 to 4%.

Anions↗

Automated sample preparation and gas chromatographic-mass spectrometric analysis of urinary androgenic anabolic steroids.

This paper presents an automated method for extracting anabolic agents from urine samples for their GC-MS analysis by selected-ion monitoring. The sample preparation was carried out in a Hewlett-Packard 7686 SPE PrepStation system. Each 0.6-ml aliquot was hydrolyzed, extracted, dried and trimethylsilyl (TMS) derivatized in a 2-ml vial without any hands-on labor. When sample preparation was finished 2 microl of the extract was injected into the gas chromatograph by split (1:10) mode. Due to the small amount of free space in the 2-ml vials for handling the sample, parameters like time of hydrolysis, type of shaking, number of extractions and some TMS derivatization parameters had to be adjusted to achieve the best recovery for all of the compounds in the screening. Manual and automated sample preparation schemes were compared in terms of linearity, precision, accuracy, limit of detection and recovery data. When large concentrations were analyzed using the automated method no carry-over effect was observed.

Anabolic Agents↗

Effect of sample preparation methods on the analysis of dispersed polysaccharides by matrix-assisted laser desorption/ionization time-of-flight mass spectrometry.

Effect of sample preparation methods on the matrix-assisted laser desorption/ionization (MALDI) analysis of dispersed polysaccharides is reported. By using the conventional drop-drying method, the measured number-averaged molecular weights were found to differ significantly from the values obtained from gel-permeation chromatography (GPC). These discrepancies were found to increase as the average masses of the polysaccharides increased. To understand the impact of the sample preparation method on the MALDI measurement, a dispersed dextran sample was separated into ten narrow-distribution fractions. Mixtures of different mass fractions were prepared and analyzed by using different mixing and preparation methods. By using the ratio of the signal intensity for the low-mass fraction to that of the high-mass fraction as an indicator, the impact of sample preparation conditions on the enhancement of low-mass components (or suppression of high-mass components) was determined. From the results obtained, it is postulated that the difference in solubilities between the low-mass and high-mass components for dispersed polymers might be large enough to induce an enhancement of low-mass components (or suppression of high-mass components) at the surface of the crystals during sample crystallization in the drop-drying method.

Algorithms↗

Sample preparation for chromatographic analysis of food.

Sampling, homogenisation and sample preparation prior to chromatographic injection of food analytes are designed to enhance accuracy and precision. The reduction of inherent errors introduced by these steps requires the analyst's attention as a matter of course. Methods and examples of minimising errors in each step are reviewed.

Chromatography↗

Evaluation of 384-well formatted sample preparation technologies for regulated bioanalysis.

The capabilities and limitations of 384-well formatted sample preparation technologies applied to regulated bioanalysis were evaluated by developing two assays for the simultaneous quantitation of lopinavir and ritonavir, the active ingredients of Kaletra. One method used liquid-liquid extraction (LLE), and the other used solid-phase extraction (SPE). The steps and apparatuses employed by the two methods covered most of those used for bioanalysis. Briefly, the previously validated 96-well formatted assays were adapted to the 384-format with minor modifications. Because the wells of a 384-well plate are clustered together, cross-contamination between adjacent wells was evaluated critically, along with sensitivity, assay throughput, and ruggedness. Samples (35 microL) containing plasma samples (15 microL), internal standard (10 microL), and sodium carbonate (0.5 M, 10 microL to basify the sample) were placed in a 384-well microtiter plate that may contain saquinavir or amprenavir as contamination markers. For LLE preparation, the samples were placed in a deep 384-well plate (300-microL well volume) and extracted with 150 microL of ethyl acetate. Approximately 50 microL of the extracts were removed from each well after phase separation for analysis. For SPE preparation, the fortified samples were transferred to a 384-formatted SPE plate (C18, 5 mg packing). The extracts were eluted from the plate with basified 2-propanol. The LLE or SPE extracts were dried and reconstituted for column-switching high-performance liquid chromatography with tandem mass spectrometric detection (HPLC/MS/MS). The lower limit of quantitation and the assay range were the same as the 96-well formatted assay. If combined with appropriate automation, sample preparation in the 384-well format would be up to five times more efficient than the 96-well format.

Anti-HIV Agents↗

Improved chip design for integrated solid-phase microextraction in on-line proteomic sample preparation.

A recently introduced silicon microextraction chip (SMEC), used for on-line proteomic sample preparation, has proved to facilitate the process of protein identification by sample clean up and enrichment of peptides. It is demonstrated that a novel grid-SMEC design improves the operating characteristics for solid-phase microextraction, by reducing dispersion effects and thereby improving the sample preparation conditions. The structures investigated in this paper are treated both numerically and experimentally. The numerical approach is based on finite element analysis of the microfluidic flow in the microchip. The analysis is accomplished by use of the computational fluid dynamics-module FLOTRAN in the ANSYS software package. The modeling and analysis of the previously reported weir-SMEC design indicates some severe drawbacks, that can be reduced by changing the microextraction chip geometry to the grid-SMEC design. The overall analytical performance was thereby improved and also verified by experimental work. Matrix-assisted laser desorption/ionization mass spectra of model peptides extracted from both the weir-SMEC and the new grid-SMEC support the numerical analysis results. Further use of numerical modeling and analysis of the SMEC structures is also discussed and suggested in this work.

Miniaturization↗

Optimization of cellular nucleotide extraction and sample preparation for nucleotide pool analyses using capillary electrophoresis.

Cell extraction and further sample preparation for nucleotide pool analysis using capillary electrophoresis was faster and simpler using volatile extraction solvents (e.g. organic solvents and de-ionized water) compared to the commonly applied acids dissolved in water (e.g. perchloric acid and trichloracetic acid). Temperature had to be controlled during the whole sample preparation process to prevent degradation, and extracts had to be cleaned from proteins and other large molecules prior to capillary electrophoretic analysis to improve reproducibility. Capillary electrophoresis using borate and cyclodextrins in the background electrolyte was used for determining 11 cellular nucleotides simultaneously. In order to optimize the assay, 0-100% acetonitrile, 0-100% ethanol, and 0-100% methanol in de-ionized water were applied to extract nucleotides from mouse lymphoma cells, and nucleotide yields, recovery, and reproducibility were compared. The assay met the commonly accepted validation limits for biological fluids, if 20-80% acetonitrile in water and 40-60% ethanol in water were used as extraction solvents.

Acyclovir↗

New trend in sample preparation: on-line microextraction in packed syringe for liquid and gas chromatography applications. I. Determination of local anaesthetics in human plasma samples using gas chromatography-mass spectrometry.

A new technique for sample preparation on-line with LC and GC-MS assays was developed. Microextraction in a packed syringe (MEPS) is a new miniaturised, solid-phase extraction technique that can be connected on-line to GC or LC without any modifications. In MEPS approximately 1mg of the solid packing material is inserted into a syringe (100-250 microl) as a plug. Sample preparation takes place on the packed bed. The bed can be coated to provide selective and suitable sampling conditions. The new method is very promising. It is very easy to use, fully automated, of low cost and rapid in comparison with previously used methods. This paper presents the development and validation of a method for microextraction in packed syringe MEPS on-line with GC-MS. Local anaesthetics in plasma samples were used as model substances. The method was validated and the standard curves were evaluated by the means of quadratic regression and weighted by inverse of the concentration: 1/x for the calibration range 5-2000 nM. The applied polymer could be used more than 100 times before the syringe was discarded. The extraction recovery was between 60 and 90%. The results showed close correlation coefficients (R>0.99) for all analytes in the calibration range studied. The accuracy of MEPS-GC-MS was between 99 and 115% and the inter-day precision (n=3 days), expressed as the relative standard deviation (R.S.D.%), was 3-10%.

Anesthetics, Local↗