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At least 253 records · Page 14Linked to original sources

PubMed2001

Determination of residual solvents in pharmaceuticals by thermal desorption-GC/MS.

A novel method for the determination of residual solvents in pharmaceuticals by thermal desorption (TD)-GC/MS has been established. A programmed temperature pyrolyzer (double shot pyrolyzer) is applied for the TD. This method does not require any sample pretreatment and allows very small amounts of the sample. Directly desorbed solvents from intact pharmaceuticals (ca. 1 mg) in the desorption cup (5 mm x 3.8 mm i.d.) were cryofocused at the head of a capillary column prior to a GC/MS analysis. The desorption temperature was set at a point about 20 degrees C higher than the melting point of each sample individually, and held for 3 min. The analytical results using 7 different pharmaceuticals were in agreement with those obtained by direct injection (DI) of the solution, followed by USP XXIII. This proposed TD-GC/MS method was demonstrated to be very useful for the identification and quantification of residual solvents. Furthermore, this method was simple, allowed rapid analysis and gave good repeatability.

Adsorption↗

PubMedDate not supplied

Effects of nitrosation on the formation of cyanide in publicly owned treatment works secondary effluent.

Cyanide has been detected in the effluents of some publicly owned treatment works (POTWs) at levels exceeding the influent concentration. The presence of nitrite ion (NO2-) as a common constituent in domestic wastewater effluents may play an important role in the formation of cyanide through reaction with certain kinds of organic compounds, especially aromatic compounds. Laboratory studies with seven organic compounds (aniline. p-toluidine, phenol, 1,2,4-trihydroxybenzene, L-serine, glycine, and benzoic acid) revealed that cyanide can be formed by reaction of nitrite with some of these compounds. The most substantial free cyanide (HCN. CN-) production observed at 25 degrees C was 0.15 mg/L from reaction of 0.01 mM 1.2.4-trihydroxybenze with 5 mg/L nitrite for 72 hours. Substantial free cyanide formation was also observed at pH 2-4 in experiments with POTW effluents when reactive organics and nitrite were both added to wastewater. Formation of cyanide through nitrosation was strongly pH dependent, being most significant at low pH (2 to 4) and negligible at neutral-to-high pH. This result points to nitrous acid (HNO2) as being more reactive than the dissociated NO2- ion. The reaction of these nitrite species with organics also occurs in conventional analyses for total cyanide which involve distillation under strongly acidic conditions. Sufficient sample pretreatment with sulfamic acid at the time of sampling, not at the time of analysis. is highly recommended to prevent biasing analytical measurement of total cyanide in POTW effluents.

Cyanides↗

PubMedDate not supplied

In vitro effect of Escherichia coli on human sperm acrosome reaction.

Escherichia coli are known to reduce human sperm motility. The purpose of the present study was to examine whether these bacteria may also affect the acrosome reaction, which is another important sperm function. The acrosome reaction was determined in spermatozoa from 29 fertile men by triple stain after 3-h incubation at 37 degrees C with 2 x 10(6) E. coli/mL or without bacteria (control). Each sample was treated with 0.1% DMSO (spontaneous acrosome reaction) or calcium ionophore A23187 (induced acrosome reaction) for 1 h at 37 degrees C. The inducibility of the acrosome reaction was significantly lower in semen samples pretreated with E. coli than in the control samples (9.8 +/- 4.2% vs. 12.7 +/- 5.3%; p < .05). The results demonstrate that E. coli affect the inducibility of the acrosome reaction in vitro and may impair the fertilizing capacity of human spermatozoa.

Acrosome↗

PubMed1979

Colorimetric determination of poly(N-vinyl-2-pyrrolidone) in contact lens solutions.

A rapid colorimetric method is presented for the quantitative determination of poly(N-vinyl-2-pyrrolidone) in contact lens solutions. The method is simple, requires no sample pretreatment, and uses only a small volume of sample. The procedure is based on the measurement of the net absorbance of a poly(N-vinyl-2-pyrrolidone)- Congo red complex at 545 nm. An accuracy of greater than +/- 4% was obtained for the concetnration ranges usually found in contact lens solutions with a minimum detection level of 10 ppm. The method is useful as a screening procedure for solutions of unknown composition and as a quality assurance procedure for routine determinations.

Colorimetry↗

PubMed1981

Fully automated high-performance liquid chromatography. A new chromatograph for pharmacokinetic drug monitoring by direct injection of body fluids.

A new fully automated high-performance liquid chromatography is described which detects drugs from directly injected plasma (urine, saliva) without sample pretreatment. The apparatus consists of a programmable automatic sampling unit, which is connected via two alternating working pre-columns to an analytical column ("alternating pre-column sample enrichment"). The new device is able to operate with directly injected body fluids like an auto-analyzer and is especially useful for pharmacokinetic and clinical studies, where drug concentrations have to be determined from plasma, urine or saliva.

Body Fluids↗

PubMed2006

Coupling of acetonitrile deproteinization and salting-out extraction with acetonitrile stacking for biological sample clean-up and the enrichment of hydrophobic compounds (porphyrins) in capillary electrophoresis.

A new sample pretreatment approach in CE was developed for concurrent biological sample clean-up and the concentration of hydrophobic compounds based on the combination of ACN deproteinization with salting-out extraction. Further enhancement in concentration detection sensitivity was achieved by coupling (offline) salting-out extraction with an online CE sample enrichment technique known as "ACN stacking". By optimizing the pH of salting-out extraction, a number of model compounds (hydrophobic porphyrins with clinical significances), i.e. zinc-protoporphyrin, protoporphyrin, and coproporphyrin (CP) III and I, can be efficiently extracted from the aqueous sample into a smaller volume organic solvent (ACN) phase and an enrichment factor of ca. 100 can be obtained. The pressure injection of the enriched ACN phase (containing ca.1% NaCl) into the CE capillary at 10% capillary volume resulted in additional concentration of the various hydrophobic porphyrins, allowing for a combined enrichment factor of ca.1000 to be obtained. Calibration curves obtained for the determination of a pair of positional isomers with significant diagnostic value, urinary CPIII and CPI, were found to be linear between 10-300 ng/mL (with R2 = 0.999), and LODs (absorbance detection at 400 nm) were ca. 0.8 ng/mL (1.1 nmol/L of CPIII or CPI). Based on a single salting-out extraction, intraday precisions (nine consecutive injections) for both CPIII and CPI (at spiked concentrations of 10-300 ng/mL into urine) in terms of migration time and peak area were found to be within the range of 0.2-0.5 and 0.8-2.9%, respectively.

Acetonitriles↗

PubMed2004

Simultaneous determination of arginine and seven metabolites in plasma by reversed-phase liquid chromatography with a time-controlled ortho-phthaldialdehyde precolumn derivatization.

In an attempt to simultaneously detect molecules generated through the metabolism of l-arginine, a high-performance liquid chromatography method with on-line time-controlled preinjection reaction of ortho-phthaldialdehyde derivatization was developed. Plasma concentrations of citrulline, N(G)-hydroxy-l-arginine, N(G)-monomethyl-l-arginine, asymmetric N (G), N (G)-dimethyl-l-arginine, symmetric N (G), N (G')-dimethyl-l-arginine, ornithine, and agmatine were analyzed within 35min, using only 20microl of sample, pretreated by a simple cold ethanol cleanup procedure. Plasma samples of 35 healthy human volunteers were analyzed and results were comparable to other published data. All detection parameters of the method demonstrate that it is a reliable and efficient means for the comprehensive determination of arginine and its metabolites, making this approach suitable for routine clinical applications.

Arginine↗

PubMed2000

Solid-phase extraction for multiresidue analysis of organic contaminants in water.

To overcome the limitations of the detection systems associated with gas or liquid chromatography, a sample pretreatment is required with the objective to provide a sample fraction enriched with all the target analytes and as free as possible from other matrix components. There is now no doubt that solid-phase extraction (SPE) has now become the method of choice for carrying out simultaneously the extraction and concentration of many compounds in aqueous samples. Many recent applications of SPE to multiresidue analysis are reviewed with an emphasis on the importance of the choice of the sorbent and of the sample volume. SPE is particularly well adapted to multiresidue analysis including compounds from a wide range of polarity or characterized by various physico-chemical properties. However, SPE is not completely free from practical problems inherent to the nature of the compounds or to the coupling to the chromatographic systems. Many examples are reported to illustrate these problems which can in most cases be circumvented. New developments in SPE are also reviewed.

Chromatography, Liquid↗

PubMed1998

Determination of doxorubicin and metabolites in murine specimens by high-performance liquid chromatography.

A sensitive and selective reversed-phase high-performance liquid chromatographic method for the quantification of doxorubicin and its metabolites doxorubicinol, 7-deoxydoxorubicinone and 7-deoxydoxorubicinolone was developed and validated for a variety of murine specimens. Daunorubicin was used as internal standard. Sample pretreatment involved liquid-liquid extraction of 200 microl sample with 1 ml of chloroform-1-propanol (4:1, v/v). Chromatographic separation was achieved isocratically on a LiChrosorb RP-8 analytical column at ambient temperature. The mobile phase consisted of acidified water (pH 2.05)-acetonitrile-tetrahydrofuran (80:30:1, v/v/v). The column effluent was monitored fluorimetrically at an excitation wavelength of 460 nm and an emission wavelength of 550 nm. The lower limits of quantitation were in the range 1.8-2.4 nM. Spiked murine specimens and samples from treated mice were subjected to stability studies. The results demonstrated the importance of validation in all relevant specimens, since the accuracy and precision were highly matrix-dependent. Accuracies and precisions of measured drug concentrations in liver, spleen, muscle, gastrointestinal tissues, diluted bile, feces and urine were lower than in the other matrices. Doxorubicin was unstable in diluted bile, but not in the other specimens. The method is suitable for studying the pharmacokinetics of doxorubicin and its metabolites in mice.

Animals↗

PubMed2006

Direct determination of rare earth elements at the subpicogram per gram level in antarctic ice by ICP-SFMS using a desolvation system.

A method, based on inductively coupled plasma sector field mass spectrometry coupled with a microflow nebulizer and a desolvation system, has been developed for the direct determination of rare earth elements (REE) (La, Ce, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, Lu) down to the subpicogram per gram level (1 pg/g = 10(-12) g g(-1)) in approximately 1 mL of molten Antarctic ice. Contamination problems were carefully taken into account by adopting ultraclean procedures during the sample pretreatment phases. The use of a desolvation system for sample introduction during the analysis greatly reduced spectral interferences from oxide formation; the residual interfering contributions were calculated and subtracted whenever necessary. A matched calibration curve method was used for the quantification of the analytes. Instrumental detection limits ranged from 0.001 pg/g for Ho, Tm, and Lu to 0.03 pg/g for Gd. The precision, in terms of relative standard deviation on 10 replicates, ranged from 2% for La, Ce, Pr, and Lu, up to 10% for Er, Tm, and Yb. This methodology allowed the direct determination of REE in a 1-mL sample of ancient Antarctic ice with concentration ranges between 0.006 and 0.4 pg/g for Tm and 0.9-60 pg/g for Ce.

Journal Article↗

PubMed2003

Measurement of As, P, and S in the waste gases and water emitted from semiconductor processes by high-temperature hydrogen reduction gas chromatography.

A quick, sensitive, and accurate method, high-temperature hydrogen reduction gas chromatography (GC) (1,2), for measuring arsenic (As), phosphorus (P), and sulfur (S) in the waste gases and water emitted from semiconductor processes is proposed in this paper. A high-temperature hydrogen reduction system that changes As, P, S, and their compounds into hydrides by atomic hydrogen has been designed. It is convenient to detect these elements in solid, liquid, and gaseous samples by high-temperature hydrogen reduction GC without pretreating samples. The lower detection limits of As, P, and S by this method are 0.01, 0.003, 0.02 mg/L, respectively, and the values of relative standard deviation are 6.2%, 8.6%, and 0.3%, respectively. Results determined by high-temperature hydrogen reduction GC are primarily accordant to those by conventional methods such as colorimetry and ion chromatography. The error statistics of this analysis method also show that high-temperature hydrogen reduction GC can be successfully used to determine trace As, P, and S in waste gases and wastewater emitted from semiconductor processes.

Journal Article↗

PubMed2005

Simultaneous multi-species determination of trimethyllead, monomethylmercury and three butyltin compounds by species-specific isotope dilution GC-ICP-MS in biological samples.

An accurate and sensitive multi-species species-specific isotope dilution GC-ICP-MS method was developed for the simultaneous determination of trimethyllead (Me3Pb+), monomethylmercury (MeHg+) and the three butyltin species Bu3Sn+, Bu2Sn2+, and BuSn3+ in biological samples. The method was validated by three biological reference materials (CRM 477, mussel tissue certified for butyltins; CRM 463, tuna fish certified for MeHg+; DORM 2, dogfish muscle certified for MeHg+). Under certain conditions, and with minor modifications of the sample pretreatment procedure, this method could also be transferred to environmental samples such as sediments, as demonstrated by analyzing sediment reference material BCR 646 (freshwater sediment, certified for butyltins). The detection limits of the multi-species GC-ICP-IDMS method for biological samples were 1.4 ng g(-1) for MeHg+, 0.06 ng g(-1) for Me3Pb+, 0.3 ng g(-1) for BuSn3+ and Bu3Sn+, and 1.2 ng g(-1) for Bu2Sn2+. Because of the high relevance of these heavy metal alkyl species to the quality assurance of seafood, the method was also applied to corresponding samples purchased from a supermarket. The methylated lead fraction in these samples, correlated to total lead, varied over a broad range (from 0.01% to 7.6%). On the other hand, the MeHg+ fraction was much higher, normally in the range of 80-100%. Considering that we may expect tighter legislative limitations on MeHg+ levels in seafood in the future, we found the highest methylmercury contents (up to 10.6 microg g(-1)) in two shark samples, an animal which is at the end of the marine food chain, whereas MeHg+ contents of less than 0.2 microg g(-1) were found in most other seafood samples; these results correlate with the idea that MeHg+ is usually of biological origin in the marine environment. The concentration of butyltins and the fraction of the total tin content that is from butyltins strongly depend on possible contamination, due to the exclusively anthropogenic character of these compounds. A broad variation in the butylated tin fraction (in the range of <0.3-49%) was therefore observed in different seafood samples. Corresponding isotope-labeled spike compounds (except for trimethyllead) are commercially available for all of these compounds, and since these can be used in the multi-species species-specific GC-ICP-IDMS method developed here, this technique shows great potential for routine analysis in the future.

Animals↗

PubMed1991

High-performance liquid chromatographic determination of clenbuterol and cimaterol using post-column derivatization.

A general high-performance liquid chromatographic method for the simultaneous and rapid determination of cimaterol and clenbuterol is described. Solid samples, such as animal tissues, faeces and feeding-stuffs, are extracted with dilute acid saturated with ethyl acetate. The resulting extracts or liquid samples, such as urine, plasma, blood and bile, are purified via Chem Elut columns. Separation is achieved by ion-pair chromatography on a Nova-Pak C18 column, and highly specific detection is obtained with an adapted version of the post-column derivatization described previously for the determination of clenbuterol in urine and animal tissues. Detection limits for liquids and solids are 0.1 ng/ml and 0.2 ng/g, respectively. The results are in complete agreement with analysis by high-performance thin-layer chromatography and gas chromatography-mass spectrometry, applied for confirmation after the same sample pretreatment. With this simple method, complete analysis of a liquid sample needs about 30 min and, even without an automatic sampler, 40 samples can be completely analysed in one day. This method has been used on a routine scale for nearly two years.

Adrenergic beta-Agonists↗

PubMed2026

A rare and atypical case of long-distance indirect DNA transfer: Contamination from an investigator never present at the scene.

To maximize the usefulness of DNA obtained from biological samples in forensic genetics, it is crucial to avoid DNA contamination throughout all procedures, from sample collection at crime scenes to STR profile generation in DNA laboratories. This study reports a rare and atypical case of DNA contamination in a forensic setting. During the analysis of biological evidence from a cold case preserved for 18 years, the STR profile obtained from the surface of a plastic bag matched that of an investigator, identified through the DNA elimination database. Case reconstruction confirmed that the investigator-who was located 80 km from the DNA laboratory and had never entered the crime scene or the sample storage room-was not a suspect and that the obtained STR profile originated from contamination. The most plausible explanation for the contamination was indirect transfer: investigator's DNA had adhered to a colleague's clothing and was subsequently dislodged and deposited onto the surface of the plastic bag as the colleague approached the sample pretreatment area. This study integrates trace DNA profiling of challenged samples with rapid contamination investigation and proposes prevention and control measures. This case underscores that, although DNA is widely regarded as the "gold standard" in forensic genetics, its interpretation must be considered within the context of the entire case. Conclusions should not be drawn based solely on a single DNA result.

Humans↗

PubMed2003

Simultaneous determination of six urinary porphyrins using liquid chromatography-tandem mass spectrometry.

A liquid chromatographic-tandem mass spectrometric (LC-MS-MS) method without sample pretreatment was developed and validated for determination of porphyrins in samples of canine urine. Acidified urine samples were directly injected into the LC-MS system and a gradient elution program was applied. The mass spectrometer was operated in the multi-reaction monitoring (MRM) mode and six porphyrins were detected with excellent sensitivity and selectivity. The lower limits of quantification were 0.014 nmol/mL for mesoporphyrin IX, coproporphyrin I, 5-carboxylporphyrin, 6-carboxylporphyrin and 7-carboxylporphyrin, and 0.029 nmol/mL for uroporphyrin I. Good ln-quadratic responses of calibration standards over the range 0.01 to 1.0 nmol/mL for mesoporphyrin IX, coproporphyrin I, 5-carboxylporphyrin, 6-carboxylporphyrin and 7-carboxylporphyrin, and 0.02 to 1.0 nmol/mL for uroporphyrin I were demonstrated. This method should be easily adapted through cross-validation for use in determining the effects of chemicals and pharmaceuticals on the urinary excretion profile of porphyrins in preclinical studies with other species, and in assisting the diagnosis of porphyria in clinical studies.

Chromatography, High Pressure Liquid↗

PubMed2004

New method for the determination of benzoic and sorbic acids in commercial orange juices based on second-order spectrophotometric data generated by a pH gradient flow injection technique.

Two widely employed antimicrobials, benzoic and sorbic acids, were simultaneously determined in commercial orange juices employing a combination of a flow injection system with pH gradient generation, diode array spectrophotometric detection, and chemometric processing of the recorded second-order data. Parallel factor analysis and multivariate curve resolution-alternating least-squares were used for obtaining the spectral profiles of sample components and concentration profiles as a function of pH, including provisions for managing rank-deficient data sets. An appropriately designed calibration with a nine-sample set of binary mixtures of standards, coupled to the use of the second-order advantage offered by the applied chemometric techniques, allowed quantitation of the analytes in synthetic test samples and also in commercial orange juices, even in the presence of unmodeled interferents (with relative prediction errors of 8.7% for benzoic acid and 2.5% for sorbic acid). No prior separation or sample pretreatment steps were required. The comparison of results concerning commercial samples with a laborious reference technique yielded satisfactory statistical indicators (recoveries were 99.0% for benzoic acid and 101.4% for sorbic acid).

Benzoic Acid↗

PubMed2002

Method for the determination of sub-ppm concentrations of perfluoroalkylsulfonate anions in water.

The determination of sub-ppm concentrations of aqueous perfluoroalkylsulfonate (PFSt) anions, including perfluorooctylsulfonate (PFOS), has been accomplished with a relatively simple mass spectrometric procedure that does not require extraction of the analytes into an organic solvent or a chromatographic separation prior to injection into the negative-ion electrospray ionization mass spectrometer. Sample pretreatment was minimized and consisted of dilution of the aqueous samples of groundwater, surface water, tap water, and distilled water with acetonitrile, addition of dodecylsulfate (DDS) as an internal standard, and, in some cases, addition of known amounts of perfluorobutylsulfonate (PFBS) or PFOS for standard-addition experiments. The linear-response range for PFOS is 25.0 microg L(-1) to 2.5 mg L(-1). The lower limit of this range is three orders of magnitude lower than an equally straightforward chromatographic method. The relative errors for standard aqueous solutions containing only 25.0 microg L(-1) and 2.5 mg L(-1) PFOS are +/- 14% and +/- 7%, respectively, with 133 microg L(-1) DDS as the internal standard. The detection limit and quantification limit for PFOS in these standards are 5.0 microg L(-1) and 25.0 microg L(-1), respectively. Six different PFS anions, containing three to eight carbon atoms, were identified and quantified in an aqueous film-forming foam (AFFF) formulation using the method of standard additions. Two alkylsulfate anions and two perfluoroalkylcarboxylate anions were also identified in the AFFF formulation.

Alkanesulfonates↗

PubMed2000

Two-stage dilute-acid pretreatment of softwoods.

Whole tree chips obtained from softwood forest thinnings were pretreated via single- and two-stage dilute-sulfuric acid pretreatment. Whole-tree chips were impregnated with dilute sulfuric acid and steam treated in a 4-L steam explosion reactor. In single-stage pretreatment, wood chips were treated using a wide range of severity. In two-stage pretreatment, the first stage was carried out at low severity to maximize hemicellulose recovery. Solubilized sugars were recovered from the first-stage prehydrolysate by washing with water. In the second stage, water-insoluble solids from first-stage prehydrolysate were impregnated with dilute sulfuric acid, then steam treated at more severe conditions to hydrolyze a portion of the remaining cellulose to glucose and to improve the enzyme digestibility. The total sugar yields obtained after enzymatic hydrolysis of two-stage dilute acid-pretreated samples were compared with sugar yields from single-stage pretreatment. The overall sugar yield from two-stage dilute-acid pretreatment was approx 10% higher, and the net enzyme requirement was reduced by about 50%. Simultaneous saccharification and fermentation using an adapted Saccharomyces cerevisiae yeast strain further improved cellulose conversion yield and lowered the enzyme requirement.

Cellulase↗