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At least 343 records · Page 19Linked to original sources
PubMed1996

Sample preparation with an automated robotic workstation for organic acid analysis by gas chromatography-mass spectrometry.

We attempted to automate sample preparation for analysis of organic acids by gas chromatography-mass spectrometry using a computer-controlled, automated robotic workstation that is integrated and connected to the gas chromatography-mass spectrometry (HP-5890/5971) system. Of the two methods developed, one employed solvent extraction, while the other utilized a silica, solid-phase extraction cartridge. Both automated methods were compared to a manual, solvent extraction procedure used routinely in our laboratory. Normal, spiked urine, and urine from patients with a variety of metabolic abnormalities were analyzed. The robotic workstation did not meet all our requirements for a rapid, reliable, laboratory device. Recoveries with the automated procedures were less than with the manual method, and some organic acids important in the diagnosis of inborn errors of metabolism were not detected. Additionally, the robotic device had mechanical and design problems that made it slower and less reliable than the manual procedure.

Automation↗
PubMed1999

Membrane-based sample preparation coupled on-line to chromatography or electrophoresis.

A review on the use of membranes for on-line sample preparation prior to chromatographic and electrophoretic analysis is provided. The current state-of-the-art of four membrane-based techniques (dialysis, electrodialysis, filtration and membrane extraction) is described by reviewing their principles and applications. Possible future developments are discussed.

Chromatography↗
PubMed2004

Photopolymerized microtips for sample preparation in proteomic analysis.

We demonstrate a novel method for the fabrication of disposable plastic microtips, which we name "EasyTip", by a photopolymerization technique. C18 reversed-phase (C18) and ion metal affinity chromatography (IMAC) beads were immobilized on a plastic pipette tip, made of polypropylene materials, by photo-initiated polymerization. The fabricated EasyTips can be manipulated using commercial pipettes for wash/elution of minute amount of biological samples (< 10 microL) and can be applied for mass spectrometry (MS)-based proteomic analysis, in which the detection sensitivity depends critically on the optimal sample preparation. The recovery of a sample of 25 fmol of tryptic hemoglobin digest loaded in a C18 EasyTip was near 100% and we estimated the loading capacity to be around 0.4-2.0 microg of total proteins or peptides, which is well above a sufficient quantity for MS analysis. The effectiveness of the C18 EasyTips in enhancing the detection sensitivity of matrix-assisted laser desorption/ionization (MALDI)-MS signal, and thus providing a greater sequence coverage, was also demonstrated by the analysis of hemoglobin digest and the in-gel digested epidermal growth factor receptor (EGFR) protein from A431 cell lysate. We also demonstrated the usefulness of the immobilized IMAC EasyTips in extracting the signal of tryptic phosphopeptides of beta-casein (10 pmol) having one and four phosphorylation sites by using an IMAC EasyTip prior to off-line analysis by MS. The combination of IMAC EasyTips and MALDI-MS allowed the unambiguous identification of phosphopeptides based on the phosphatase assay as well as the post-source decay. Compared to other miniaturized devices, this fabrication method is simple, cheap, and requires less human intervention. Moreover, the method of manipulating the EasyTips is straightforward and can be automated readily by a robotic system for high-throughput analysis.

Disposable Equipment↗
PubMed2004

Sample preparation optimization for assay of active pharmaceutical ingredients in a transdermal drug delivery system using experimental designs.

A simple but very effective sample preparation method is discussed for a matrix or drug-in-adhesive type of transdermal drug delivery system (TDS). The method is a one-step extraction using a methanol/water solvent system. Because of the unique design and physical property of the delivery system, special considerations were taken in selection of sample solvent, sample container and extraction enhancement device. The main focus of the article is on method optimization using experimental designs. A Plackett-Burman design was used to screen multiple method factors including extraction solvent strength, extraction solvent volume, shaking speed of a reciprocating shaker, and shaking time. Later, two of the factors were studied in more details using a 4 x 5 general factorial design. From the experimental results, the so-called main effects plots and interaction plots were generated using a statistical software. The plots are helpful in choosing the method conditions.

Administration, Cutaneous↗
PubMedDate not supplied

Sample preparation and liquid chromatographic determination of vitamin D in food products.

Vitamin D in different fortified foods is determined by using liquid chromatography (LC). Sample preparation is described for fortified skim milk, infant formulas, chocolate drink powder, and diet food. The procedure involves 2 main steps: saponification of the sample followed by extraction, and quantitation by LC analysis. Depending on the sample matrix, additional steps are necessary, i.e., enzymatic digestion for hydrolyzing the starch in the sample and cartridge purification before LC injection. An isocratic system consisting of 0.5% water in methanol (v/v) on two 5 microns ODS Hypersil, 12 X 0.4 cm id columns is used. Recovery of vitamin D added to unfortified skim milk is 98%. The results of vitamin D determination in homogenized skim milk, fortified milk powder, fortified milk powder with soybean, chocolate drink powder, and sports diet food are given.

Animals↗
PubMed2006

Application of dual counter-current chromatography for rapid sample preparation of N-methylcarbamate pesticides in vegetable oil and citrus fruit.

Dual counter-current chromatography (dual CCC) has been successfully applied to rapid sample preparation for the simultaneous determination of residual carbaryl, fenobucarb and methomyl in vegetable oil and citrus fruit. The citrus fruit samples were extracted with n-hexane solution containing stable isotopically labeled internal standards (methomyl-d3, fenobucarb-d3 and carbaryl-d9), and applied to dual CCC using a two-phase solvent system of n-hexane-acetonitrile to purify the carbamate pesticides from aliphatic sample matrix. The coiled column was rotated at 420 rpm, the lower mobile phase was introduced through the head toward the tail, and the upper mobile phase in the opposite direction. Due to the high partition efficiency of dual CCC, the lower phase fraction collected from 2 to 5 min after injection could be subjected to flow-injection tandem mass spectrometry directly after concentration. Repetitive sample injection can be performed at high reproducibility without a risk of contamination from the compounds retained in the column.

Carbamates↗
PubMed2004

Improved sample preparation to determine acrylamide in difficult matrixes such as chocolate powder, cocoa, and coffee by liquid chromatography tandem mass spectroscopy.

An improved sample preparation (extraction and cleanup) is presented that enables the quantification of low levels of acrylamide in difficult matrixes, including soluble chocolate powder, cocoa, coffee, and coffee surrogate. Final analysis is done by isotope-dilution liquid chromatography-electrospray ionization tandem mass spectrometry (LC-MS/MS) using d3-acrylamide as internal standard. Sample pretreatment essentially encompasses (a) protein precipitation with Carrez I and II solutions, (b) extraction of the analyte into ethyl acetate, and (c) solid-phase extraction on a Multimode cartridge. The stability of acrylamide in final extracts and in certain commercial foods and beverages is also reported. This approach provided good performance in terms of linearity, accuracy and precision. Full validation was conducted in soluble chocolate powder, achieving a decision limit (CCalpha) and detection capability (CCbeta) of 9.2 and 12.5 microg/kg, respectively. The method was extended to the analysis of acrylamide in various foodstuffs such as mashed potatoes, crisp bread, and butter biscuit and cookies. Furthermore, the accuracy of the method is demonstrated by the results obtained in three inter-laboratory proficiency tests.

Acrylamide↗
PubMedDate not supplied

Sample preparation for determination of macrocyclic lactone mycotoxins in fish tissue, based on on-line matrix solid-phase dispersion and solid-phase extraction cleanup followed by liquid chromatography/tandem mass spectrometry.

A new method based on matrix solid-phase dispersion (MSPD) on-line with a solid-phase extraction (SPE) cleanup process followed by liquid chromatography with tandem mass spectrometry (LC/MS/MS) is presented for the determination of 3 macrocyclic lactone mycotoxins in fish tissues: zearalenone, alpha-zearalenol, and beta-zearalenol. The sample was prepared in a device that used a reversed-phase material (C18) or a normal-phase material (neutral alumina) as a matrix dispersing agent, and a graphitized carbon black cartridge was used for sequential cleanup by SPE. LC/MS/MS was used for selective determination. Isocratic elution with acetonitrile-methanol-water was used for LC separation; for MS/MS, 2 types of interfaces (a pneumatically assisted electrospray ionization interface or an atmospheric pressure chemical ionization interface) were evaluated and compared in terms of the intensity of the total ion current produced by each analyte. The use of highly selective MSPD on-line with SPE for sample preparation before analysis allowed the removal of interfering matrix compounds present in tissue extracts that would otherwise cause severe ionization suppression of zearalenone and its metabolites during the ionization process. Average recoveries at 100 ng/g were between 83 and 103% with C18 and > or = 67% with neutral alumina; the relative standard deviations were < 11% with C18 and < 18% with alumina. The limits of detection ranged from 0.1 to 1.0 ng/g. Sample preparation is simple to perform, no special technical equipment is required, and solvent volumes are minimal.

Animals↗
PubMed2003

A simple rapid method of sample preparation for LC analysis of retinoyl beta-glucuronide and retinoic acid in water-based creams.

A simple method of sample preparation for LC analysis of retinoic acid (RA) and retinoyl beta-glucuronide (RAG) in creams has been developed. Water-based cream of all trans-RAG, devoid of side effects but efficacious in the treatment of acne vulgaris, was found to be hydrolyzed to RA in a temperature dependant manner. The potential benefits of water-based RAG cream stored at room temperature for the treatment of acne and wrinkle is discussed.

Calibration↗
PubMedDate not supplied

One-step sample preparation technique for broad spectrum gas chromatographic/mass spectrometric determination of organic priority pollutants in water.

A rapid and cost-effective sample preparation technique is described for the qualitative and quantitative determination of a broad spectrum of organic contaminants in water. The technique involves simultaneous-in-situ acetylation of phenols with acetic anhydride and one-step extraction of phenol acetates and basic and neutral organic compounds from water. The extract is concentrated and analyzed by gas chromatography/mass spectrometry. The recovery and precision data of selected base, neutral, and phenolic compounds are given. The advantages and disadvantages of the in-situ acetylation/extraction technique are discussed.

Acetylation↗
PubMed1993

Sample preparation techniques for conventional and high resolution scanning electron microscopy of the central nervous system.

In the present paper some basic sample preparation techniques for scanning electron microscopy of nervous tissue are described. These basic preparative methods include conventional scanning electron microscopy or slicing technique, ethanol-cryofracturing technique, freeze-fracture method using either liquid nitrogen (slow freezing) or Freon 22 cooled by liquid nigrogen (fast freezing), improved freeze-fracture method with delicate specimen preparation and chromium coating, ultrasonic microdissection, and "creative tearing" technique. Some basic principles, advantages and limitations are critically considered. In addition, some specific applications in neurobiological research are reported. Emphasis is placed upon understanding the sources and nature of artifacts that are likely to be produced in each preparatory step. Examples are given of the results obtained with the different types of nerve tissue preparation, using the cerebellar cortex as a model of the central nervous system. According to the author's experience, the slicing technique is recommended for studying cytoarchitectonic arrangement of gray centers, the ethanol-cryofracturing technique for tracing short intracortical circuits, and the freeze-fracture methods for analysis of nerve cell cytoplasmic and nuclear compartments. An attempt is made to explain results obtained in relation with nerve cell biology.

Animals↗
PubMed1987

Rapid sample preparation methods for analysis of residues of sulfamethazine and its N4-acetyl and desamino metabolites in swine tissue by HPLC.

Rapid sample preparation methods for the determination of sulfamethazine (SMZ) and its N4-acetyl and desamino metabolites in swine tissues at the 0.1 mg kg-1 level are presented. The methods use sonication-aided extraction with dichloromethane. For SMZ and N4-acetyl SMZ analysis extracts are cleaned up and concentrated on a silica disposable column followed by HPLC on a CP Spher C8 column using acetonitrile-sodium acetate buffer as the mobile phase. For desamino-SMZ analysis the extract was cleaned up and concentrated on a Florisil disposable column, followed by HPLC on a Nucleosil 5-CN column after formation of an ion-pair complex with 1-heptanesulfonic acid. For desamino SMZ peak identification by diode-array UV/VIS detection is also described. Mean recoveries from spiked tissue samples were about 87% (muscle) and 76% (kidney) for SMZ and N4-acetyl SMZ and about 70% for desamino SMZ.

Animals↗
PubMed1998

Aqueous two-phase partitioning sample preparation prior to liquid chromatography of hydrophilic drugs in blood.

The technique of aqueous two-phase partitioning is investigated as a sample preparation procedure prior to LC determination of drugs in blood. In the extraction 500 microl of whole blood is added to 2.00 g of PEG 300 and 18.0 g of phosphate buffer. The phases are mixed by stirring and allowed to separate before the clear lower salt phase is drained out using a specially designed glass adapter. After filtration 20 microl is injected into the LC system. When validated for the X-ray contrast medium iohexol R.S.D. was 2.0% and 1.2% at 10 microg/ml and 100 microg/ml of iohexol in blood, respectively.

Acetaminophen↗
PubMed2005

On-probe sample preparation without washes for matrix-assisted laser desorption/ionization mass spectrometry using an anion exchange medium.

When the mass spectra of biological samples (proteins, peptides, and so on) are obtained routinely by matrix-assisted laser desorption/ionization mass spectrometry (MALDI-MS), a serious problem is the reduction of the ionization efficiency by impurities, such as buffer salts and detergents. We focused our attention on devising a method to maintain the ionization efficiency of protein samples, even in the presence of sodium dodecyl sulfate (SDS), without any extra purification step. Although no protein ion peaks are observed in the presence of 2.5% SDS with the usual methods, the addition of a granular anion exchange silica gel to the matrix solution allowed the protein ion peaks to be obtained with an excellent signal-to-noise ratio. Together with other supporting experiments, we suggest that the positively charged surface (the basic environment derived from the anion exchange groups) and the roughness of the particles were important for good ionization in the presence of a high SDS concentration. For a very uneven surface, the SDS might be absorbed into the particle interiors during the process of cocrystallization with the matrix and analytes, which is known as the molecular sieve effect, and the SDS concentration in the surface crystalline film might be reduced. As a result, we developed an on-probe sample preparation method without washes for MALDI, using a strong anion exchange silica gel. This method is applicable even in the presence of 2.5% SDS, and is not only very simple but also inexpensive, because it can be used with the standard MALDI target plates.

Anions↗
PubMed1984

Effects of sample preparation on concentrations of cyclosporin A measured in plasma.

Because cyclosporin A rapidly changes its distribution in blood with changes in temperature, sample preparation affects results for it as measured in plasma. If whole blood is stored at either 4 degrees C or room temperature, results for cyclosporin A in the plasma are lower than in whole blood stored at 37 degrees C and centrifuged at this temperature. Re-equilibration of the former to 37 degrees C before cells are removed increases the analytical recovery of cyclosporin A in plasma; the optimal equilibration interval is 30 min. Use of such re-equilibration, followed by immediate centrifugation at room temperature, increases values obtained for cyclosporin in plasma by 60 to 65% over those determined after non-temperature-standardized collection procedures, but does not significantly improve the correlation between values for plasma and whole blood. Hematocrit and concentrations of cyclosporin A in plasma are inversely related. Correction for hematocrit improves the correlation between results for plasma and whole blood.

Centrifugation↗
PubMed2005

Detection limits of matrix-assisted laser desorption/ionisation mass spectrometry coupled to chromatography--a new application of solvent-free sample preparation.

The detection limits of matrix-assisted laser desorption/ionisation mass spectrometry (MALDI-MS) by semi-online coupling with chromatography were investigated using various mixtures of polyethylene oxides (PEOs) with different end groups. In contrast to the common 'dried-droplet' sample preparation technique, which results in an inhomogeneous sample-to-matrix ratio within the MALDI spot, the used coupling technique offers a very high reproducibility combined with surpassing sensitivity of a few femtograms over a broad range of sample-to-matrix ratios. These results are in correlation with the results of the recently established solvent-free MALDI-TOFMS method utilising the grinding approach and are also of assistance towards the more theoretical aspect of MALDI that suggests that there is no necessity for an analyte incorporation into a matrix crystal for excellent matrix-assistance.

Journal Article↗
PubMed1998

Automated sample preparation for the determination of budesonide in plasma samples by liquid chromatography and tandem mass spectrometry.

An automated bioanalytical method for the determination of the glucocorticosteroid drug budesonide in plasma samples at pM levels was investigated. The method was built using three separate automated analytical steps with manual transfer of samples between them. In the first step, a Tecan RSP150 (Genesis) pipetting robot was used to transfer 1 ml of centrifuged plasma samples and deuterated budesonide internal standard solutions into tubes and to homogenise the resulting admixture. In the second step, a solid-phase extraction was performed using an ASPEC Xli (Gilson) with 100 mg Isolute C18 columns. In order to avoid conventional time-consuming evaporation and reconstitution steps, the solid-phase extraction was coupled on-line to a trace enrichment system for further purification and concentration of the sample extracts. The concentrated samples were eluted in 300 microliters ethanol into injection vials, which were capped and transferred to the autosampler in the detection system. In the third step, the pre-treated samples were chromatographed in a gradient LC system and detected using a tandem MS system (Finnigan TSQ 7000), with an atmospheric pressure chemical ionisation interface. The described Analytical System consisting of one Tecan robot, two ASPEC systems and one LC-MS-MS system may analyse up to about 800 samples a week with less routine work for the analyst. The concentration range studied was 15 to 2500 pM in 1 ml spiked plasma samples and the limit of quantitation for the described method was determined as 15 pM, as defined by accuracy and precision better than 20%.

Administration, Topical↗
PubMed2001

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

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

Amino Acids↗