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PubMed2004

Application of solvent microextraction in a single drop for the determination of new antifouling agents in waters.

A new, rapid microextraction technique termed solvent microextraction (SME) has been developed for the simultaneous determination of new generation antifouling agents, in water samples. Chlorothalonil, dichlofluanid and Sea nine 211 were employed as model compounds to asses the extraction procedure and were determined by gas chromatography with electron capture detection. Experimental parameters which control the performance of SME, such as selection of solvent, exposure time, agitation, organic drop volume, and salt concentration were optimized. The new method provided good average enrichment factors of >10.7 for all analytes, good precision (RSD < 8.5%) and good linearity (r2 > 0.9880). The limits of detection (LODs) were in the range of 0.00025-0.003 microg/L (S/N = 3). The SME was performed in different type of natural water samples and acceptable recoveries were obtained for the tested analytes. The results demonstrated that SME is a rapid, accurate and effective preparation method and could be successfully performed for the determination of antifouling agents in water samples.

Aniline Compounds↗
PubMed1992

Environmental endotoxin measurement: the Kinetic Limulus Assay with Resistant-parallel-line Estimation.

A Limulus assay method was specifically designed for environmental endotoxin aerosols. Application of new statistical and sample preparation methods strengthened the validity and precision of the Limulus test. Statistically, the Kinetic Limulus Assay with Resistant-parallel-line Estimation (KLARE) differed from conventional analytic methods (as used in chromogenic assays and other kinetic methods) by routinely using a dilution series of the unknown sample as well as the standard to compute potency and an estimate of variance for each sample. Analysis of dose-response slopes for the standard and unknowns detected inhibition and enhancement effects--without multiple assay. Concentration-dependent interference and a more complex, concentration-independent interference with the Limulus assay were detected. Resistant regression and a standardized data analysis corrected for concentration-dependent interference. Sample preparation in a buffer eliminated concentration-independent interference and, thus, improved both the validity and the precision of potency measurements. The utility of a sample buffer and of parallel-line analysis, with both turbidimetric and chromogenic lysates, was demonstrated by assay of three control standard LPS and reference LPS (EC5). The limit of detection for endotoxin was less than 1 pg/ml in buffer. Samples containing greater than or equal to 10 pg/ml were measured with a coefficient of variation of approximately 6% in a single assay. Reproducibility of potency estimates for four samples over 3 days was compared on the basis of standard errors of the mean. The conventional method gave on average a CV of 65% while the resistant-parallel-line method gave, on average, a CV of 6%. Also, the conventional method failed to detect interference and, thus, included data from invalid assays. Conventional analysis of environmental aerosol samples was highly sensitive to the choice of dilution factor causing as much as 1000% variation in the result. By contrast, KLARE results changed by at most 30% with similar changes in initial dilution because KLARE was able to detect, and correct for, the influence of interferant compounds.

Aerosols↗
PubMed1999

Determination of homocysteine and its related compounds by solid-phase microextraction-gas chromatography-mass spectrometry.

The purpose of this study was to develop a simple and accurate analytical method to determine homocysteine (Hcy), cysteine (Cys), and methionine (Met) in aqueous samples. Until now, the most frequently used method for the assay of Hcy, Cys, and Met has been high-performance liquid chromatography with fluorescence detection after fluorescent tagging. The newly developed method involves the employment of the SPME (solid-phase microextraction) technique together with GC-MS. For application to a gas chromatographic system, alkyl formate derivatives were prepared in the form of N(O,S)-alkoxycarbonyl alkyl ester with the analytes in the aqueous samples. The optimum derivatizing regent for N(O,S)-alkoxycarbonyl alkyl ester was chosen by comparing the efficiency of the derivatized analytes in a GC through the SPME method and liquid-liquid extraction. The optimum conditions of the SPME system for the analytes derivatized with N(O,S)-ethoxycarbonyl propyl ester in the aqueous matrix were pH 3.0 and no salt, and 30 min equilibration time using an 85 microm PA (polyacrylate) fiber. The developed method is inexpensive, easy and rapid.

Calibration↗
PubMed2000

Solid-phase microextraction in biomedical analysis.

Chromatographic methods are preferred in the analysis of organic molecules with lower molecular mass (<500 g/mol) in body fluids, i.e., the assay of drugs, metabolites, endogenous substances and poisons as well as of environmental exposure by gas chromatography (GC) and liquid chromatography (LC), for example. Sample preparation in biomedical analysis is mainly performed by liquid-liquid extraction and solid-phase extraction. However, new methods are investigated with the aim to increase the sample throughput and to improve the quality of analytical methods. Solid-phase microextraction (SPME) was introduced about a decade ago and it was mainly applied to environmental and food analysis. All steps of sample preparation, i.e., extraction, concentration, derivatization and transfer to the chromatograph, are integrated in one step and in one device. This is accomplished by the intelligent combination of an immobilized extraction solvent (a polymer) with a special geometry (a fiber within a syringe). It was a challenge to test this novel principle in biomedical analysis. Thus, an introduction is provided to the theory of SPME in the present paper. A critical review of the first applications to biomedical analyses is presented in the main paragraph. The optimization of SPME as well as advantages and disadvantages are discussed. It is concluded that, because of some unique characteristics, SPME can be introduced with benefit into several areas of biomedical analysis. In particular, the application of headspace SPME-GC-MS in forensic toxicology and environmental medicine appears to be promising. However, it seems that SPME will not become a universal method. Thus, on-line SPE-LC coupling with column-switching technique may be a good alternative if an analytical problem cannot be sufficiently dealt with by SPME.

Body Fluids↗
PubMed1995

[Intake of folic acid in the total daily diet--effect of food preparation on its folic acid content].

The folic acid content of total daily diet was determined by means of high-performance liquid chromatography (HPLC). The contents of tetrahydrofolic acid (THF), 5-methyl-THF and 5-formyl-THF were differentiated. The mean of the folic acid content of the total daily diet samples determined analytically was 205 +/- 60 micrograms and the mean of the individual ingredients of the samples was 401 +/- 78 micrograms, which implies that about 50% of folic acid is destroyed by common household food preparation methods. If the contents of pteroylglutamic acid (PteGlu) and 10-formyl-PteGlu (which cannot be determined analytically) are added, it can be assumed that the folic acid content with only be reduced by about 40%. THF and 5-methyl-THF proved to be less stable than 5-formyl-THF. The monoglutamate portion of the total folat content was higher in the total diet samples than in the individual foodstuffs as a consequence of the action of the enzyme "deconjugase" which is released when the matrix of food-stuffs is destroyed.

Chromatography, High Pressure Liquid↗
PubMed2000

Use of microwave-assisted evaporation for the complete recovery of volatile species of inorganic trace analytes

Solutions must often be evaporated prior to analysis either to preconcentrate the analyte or to eliminate an incompatible matrix component. Elimination of the halogen-based acids HCI and HF using traditional evaporation methods poses recovery problems because of volatilization of the target analyte as the chloride or fluoride species. A new sample preparation chemistry for trace analysis, where losses of analyte due to volatilization during the evaporation process are minimized, is explored using the unique heating mechanisms of the microwave-assisted evaporation process. The heating mechanisms of hot plate evaporation and microwave-assisted evaporation are compared, and temperatures throughout the evaporation process using each method are predicted and experimentally verified. Because the solution actually cools during microwave-assisted evaporation, volatilization due to overheating at dryness is minimized. Elemental standard solutions and SRM soil and tissue digestates were evaporated using a hot plate method and a newly developed reduced-pressure microwave-assisted evaporation apparatus. Redissolution and analysis of the residue by ICPMS showed that complete recovery was achieved using microwave-assisted evaporation while losses of several classically volatile analytes occurred using hot plate evaporation.

Journal Article↗
PubMed1993

Isotachophoresis of nucleic acid constituents.

Determination methods for purine and pyrimidine bases, nucleosides, nucleotides and related compounds using analytical capillary isotachophoresis are reviewed. First, the isotachophoretic characterization of these compounds, as well as methods for sample preparation prior to analysis, and the different ways of detecting unknown substances in complex biological systems are described. Then applications of isotachophoretic analysis in medical diagnosis and biomedical research are reviewed. In particular, the analysis of purines, pyrimidines, nucleosides and related compounds in blood and serum for the diagnosis and treatment of inherited diseases and cancer is described. Selected applications of nucleotide analysis in biomedical research using different tissue extracts are also reviewed, and some examples of nucleotide-dependent enzymic reactions, which were performed by means of analytical isotachophoresis, are presented.

Animals↗
PubMed1992

Application of preparative liquid chromatography to the isolation of enantiomers of a benzodiazepinone derivative.

The isolation of milligram amounts of the enantiomers of a benzodiazepinone derivative was performed on an analytical cellulose tribenzoate-based column by multiple repetitive injections. An enantiomeric purity greater than 98% was required. First, an analytical method was developed to maximize the resolution by adjusting the mobile phase composition, flow-rate and most importantly the column temperature. Then the preparative separation was optimized by adjusting the sample size and detecting the sample where its UV absorbance was low. The locations of the cut points were determined by use of detector response levels. The method development, preparative separations and analytical assays of the fractions obtained were all performed on analytical columns.

Benzodiazepinones↗
PubMed1999

Systematic toxicological analysis of drugs and poisons in biosamples by hyphenated chromatographic and spectroscopic techniques.

The introduction of hyphenated chromatographic-spectroscopic techniques represented a substantial step-forward for Systematic Toxicological Analysis (STA), increasing the amount and quality of information obtainable from the analysis of a biological sample, and enhancing the possibilities of identifying unknown drugs and poisons. STA methods based either on GC-MS or on HPLC-UV published in the last decade are reviewed in this paper. The different analytical phases, i.e. sample preparation (pretreatment, extraction, derivatisation), chromatographic separation and detection/identification are examined in detail in order to emphasise the complementarity of the two approaches. In addition, the first STA method based on HPLC-MS is illustrated and some applications of TLC-UV to drug screening are also described. Finally, an overview of semi- and fully-automated STA methods is given.

Chromatography↗
PubMed2006

Method development for the determination of residual fluorotelomer raw materials and perflurooctanoate in fluorotelomer-based products by gas chromatography and liquid chromatography mass spectrometry.

The methodology for the determination of perfluorooctanoate (C(7)F(15)COO-, PFO), fluorotelomer alcohols (FTOHs: 6-2, 8-2, and 10-2), perfluorooctyl iodide (PFOI), and 8-2-8 fluorotelomer alcohol ester in complex fluorotelomer-based commercial products has been demonstrated and validated. Sample preparation procedures allowing determination of residual levels of these compounds were developed. The analytes were detected either by LC/MS/MS (PFO), LC/MS (FTOHs), or GC/MS (PFOI, 8-2-8 ester). The methods were validated by investigating the recoveries of analytes spiked at multiple levels to authentic sample matrices. The recoveries generally were between 70 and 130%. The limits of detection were in sub-microg/g range and the limits of quantitation were in the mug/g range. The methods were applied to fluorotelomer-based raw materials and fluorotelomer-based surfactants and polymeric products and represent methods useful for the determination of higher carbon chain length homologs as well.

Alcohols↗
PubMed2006

Influence of hemolysis on routine clinical chemistry testing.

BACKGROUND: Preanalytical factors are the main source of variation in clinical chemistry testing and among the major determinants of preanalytical variability, sample hemolysis can exert a strong influence on result reliability. Hemolytic samples are a rather common and unfavorable occurrence in laboratory practice, as they are often considered unsuitable for routine testing due to biological and analytical interference. However, definitive indications on the analytical and clinical management of hemolyzed specimens are currently lacking. Therefore, the present investigation evaluated the influence of in vitro blood cell lysis on routine clinical chemistry testing. METHODS: Nine aliquots, prepared by serial dilutions of homologous hemolyzed samples collected from 12 different subjects and containing a final concentration of serum hemoglobin ranging from 0 to 20.6 g/L, were tested for the most common clinical chemistry analytes. Lysis was achieved by subjecting whole blood to an overnight freeze-thaw cycle. RESULTS: Hemolysis interference appeared to be approximately linearly dependent on the final concentration of blood-cell lysate in the specimen. This generated a consistent trend towards overestimation of alanine aminotransferase (ALT), aspartate aminotransferase (AST), creatinine, creatine kinase (CK), iron, lactate dehydrogenase (LDH), lipase, magnesium, phosphorus, potassium and urea, whereas mean values of albumin, alkaline phosphatase (ALP), chloride, gamma-glutamyltransferase (GGT), glucose and sodium were substantially decreased. Clinically meaningful variations of AST, chloride, LDH, potassium and sodium were observed in specimens displaying mild or almost undetectable hemolysis by visual inspection (serum hemoglobin < 0.6 g/L). The rather heterogeneous and unpredictable response to hemolysis observed for several parameters prevented the adoption of reliable statistic corrective measures for results on the basis of the degree of hemolysis. CONCLUSION: If hemolysis and blood cell lysis result from an in vitro cause, we suggest that the most convenient corrective solution might be quantification of free hemoglobin, alerting the clinicians and sample recollection.

Artifacts↗
PubMed2004

Optimization strategies for the analysis and purification of drug discovery compounds by reversed-phase high-performance liquid chromatography with high-pH mobile phases.

Careful selection of both high-pH mobile phase as well as organic modifier, was performed in order to develop and optimize HPLC conditions for the separation of drug discovery compounds. High-pH mobile phases provide excellent chromatographic resolution and increased mass loading of basic compounds. The analytical methods so defined have been successfully transferred to preparative automated UV-directed purification, an important fact due to the increasing number of samples requiring purification. It should be noted that, the single prerequisite for this approach is an analytical LC-UV-MS run, therefore the system has the ability to collect only fractions likely to contain the target product. A cost-effective strategy for maximizing the purification of drug discovery compounds is proposed.

Chromatography, High Pressure Liquid↗
PubMed2005

Analysis of macrolide antibiotics by liquid chromatography.

A compilation of the most representative single and multianalyte HPLC methods for the analysis of macrolide antibiotics published during the last two decades is presented in this paper. Its scope is the coverage of two main areas which require the determination of macrolide antibiotics at a low concentration level, i.e. pharmacokinetic studies and residue analysis. Both of these areas involve the treatment of biological and foodstuff matrices, respectively. A detailed explanation of the different sample preparation procedures as well as the experimental conditions and the main analytical features are provided for each referred method in order to allow the reader to select the most suitable conditions for their particular purpose.

Animals↗
PubMed2004

Determination of arginine and asymmetric dimethylarginine (ADMA) in human plasma by liquid chromatography/mass spectrometry with the isotope dilution technique.

Arginine (ARG) is a substrate for endogenous nitric oxide (NO) production whereas its metabolite, asymmetric dimethylarginine (ADMA), acts as an inhibitor. Sufficient NO production is essential for cardiovascular key functions, thus elevated concentration levels of ADMA are related to a range of cardiovascular diseases. Owing to the lack of reliable methods for the measurement of ARG and ADMA in human plasma, concentration values determined with these methods can differ considerably. We present here a simple and very robust liquid chromatographic/mass spectrometric method for the determination of ARG and ADMA utilizing isotope-labeled internal standards. Sample preparation requires only protein precipitation; the analytes were derivatized with o-phthalaldehyde-mercaptoethanol and separated on a reversed-phase C(18) column with gradient elution. The analytes were detected with an electrospray ionization ion trap instrument working in the full-scan single mass spectrometry mode. Concentration values obtained with this method for healthy controls were ARG = 63.9 +/- 23.9 microM and ADMA = 0.355 +/- 0.066 microM, with a normal range for ADMA from 0.225 to 0.485 microM. The corresponding values for end-stage chronic renal failure patients are ARG = 48.1 +/- 18.5 microM, p < 0.01 and ADMA = 0.673 +/- 0.134 M, p < 0.001.

Adult↗
PubMed1999

Assessment of polycyclic aromatic hydrocarbon content of smoked fish by means of a fast HPLC/HPLC method.

Polycyclic aromatic hydrocarbon (PAH) concentrations in smoked food can reach levels hazardous for the human health, especially when the smoking procedure is carried out under uncontrolled conditions. In this work a simple and rapid method for the determination of PAHs in smoked fish samples is described. PAHs were extracted from the insoluble samples (together with fat substances) by homogenization with acidified chloroform. The fat extract was then submitted to a first LC sample preparation step (performed on a large silica column) to isolate PAHs from triglycerides. After reconcentration, the PAH fraction was finally injected into the reverse-phase analytical column. The proposed method, which presents good characteristics of recoveries and repeatability, was also used to analyze PAH content of some smoked trout samples packed under vacuum.

Animals↗
PubMed1998

Structure of water, proteins, and lipids in intact human skin, hair, and nail.

Raman spectroscopy is a nondestructive analytical method for determining the structure and conformation of molecular compounds. It does not require sample preparation or pretreatment. Recently, near-infrared Fourier transform Raman spectroscopy has emerged as being specially suited for investigations of biologic material. In this study, we obtained near-infrared Fourier transform Raman spectra of intact human skin, hair, nail, and stratum corneum. We disclosed major spectral differences in conformational behavior of lipids and proteins between normal skin, hair, and nail. The amide I and III band location indicated that the majority of proteins in all samples have the same secondary alpha-helix structure. Positions of (S-S) stretching bands of proteins revealed a higher stability of the disulfide bonds in the hair and the nail. Analysis of vibrations of protein -CH groups showed that in the hair and the nail the proteins are apparently highly folded, interacting with the surroundings only to a small degree. The position of lipid specific peaks in spectra of hair, nail, and stratum corneum suggested a highly ordered, lamellar crystalline lipid structure. A greater lipid fluidity was found in whole skin. Assessment of the structure of water clusters revealed that mainly bound water is present in the human skin, stratum corneum, and nail. In conclusion, structural changes of water, proteins, and lipids in intact skin and skin appendages may be analyzed by Raman spectroscopy. This technique may be used in the future in a noninvasive analysis of structural changes in molecular compounds in the skin, hair, and nail associated with different dermatologic diseases.

Adolescent↗
PubMedDate not supplied

Thermal analyser and micro FT-IR/DSC system used to determine the protective ability of microencapsulated squid oil.

Squid oil was microencapsulated by spray drying method. Gelatin, sodium caseinate, maltodextrin were contained in spray drying formulation with or without lecithin and microcrystalline cellulose (Avicel). The thermal stability of the unencapsulated and encapsulated squid oils was determined by pressure differential scanning calorimetry (PDSC), Fourier transform infrared (FT-IR) microscopic photometer with DSC system and themogravimetric analysis (TGA). The results indicate that the above analytical apparatus is an easy and reliable method to investigate the samples and that the microcapsule prepared by spray-dried formulation with lecithin as an emulsifier and Avicel as a stabilizer exhibits more stable thermal stability and longer shelf-life.

Animals↗
PubMedDate not supplied

A review of analytical methods for the determination of sulfolane and alkanolamines in environmental studies.

Sulfolane and alkanolamines are used extensively in the processing of sour natural gases. Over many years of operation, there have been inadvertent leaks of these chemicals to groundwater and wetlands surrounding gas processing facilities, leading to uptake by vegetation. Because sulfolane and alkanolamines are extremely water-soluble, their analysis has presented challenges, particularly requirements for suitable extraction from biological matrixes and soil, along with sensitive detection using commonly available instrumentation. Analytical methods usually use gas chromatography or liquid chromatography with a variety of detector systems. Sample preparation techniques may include extraction with organic solvents, water, or a combination of these. In some cases, direct aqueous injections have been used. Derivatization of alkanolamines has been used to improve the chromatographic separations and detection. More recent procedures, using positive-ion electrospray ionization mass spectrometry (MS), have been useful for the confirmation of uptake of the alkanolamines and transformation products by wetland vegetation. Future developments will likely center on further MS analyses for identification of metabolites and transformation products in aquatic environments.

Amines↗