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PubMed1985

Enhanced detection of drugs in complex mixtures by derivatization/secondary ion mass spectrometry.

Derivatization/secondary ion (SI) mass spectrometry is a sensitive surface analysis technique. It can detect ppm levels of selected compounds in complex mixtures, as can tandem mass spectrometry. However, unlike tandem mass spectrometry it uses simpler instrumentation, since chemistry is used to select the compound of interest instead of a mass spectrometer. The application of derivatization/SI mass spectrometry is discussed regarding the analysis of drugs in aqueous media, tablets or human urine.

Chemical Phenomena↗
PubMed2000

High-performance liquid chromatographic separation of a complex mixture of diuretics using a micellar mobile phase of sodium dodecyl sulphate. Application to human urine samples.

A systematic optimization of the HPLC separation of a complex mixture containing 19 diuretics by micellar liquid chromatography using sodium dodecyl sulphate (SDS), a Hypersil (150 mmx3.0 mm I.D., 5 microm) C18 column, a flow-rate of 0.5 ml min(-1) and UV absorbance detection has been carried out. Several mobile phases consisting of SDS and organic modifiers such as acetonitrile, tetrahydrofuran, propanol, butanol or pentanol, and the pH adjusted to 3.2, were tested. The effect of the organic modifier and SDS concentration on the retention behavior and separation of the diuretics was investigated. A mobile phase containing 40 mM SDS and 4% tetrahydrofuran was finally selected. Under these conditions, 14 out of 19 diuretics were separated in about 31 min. A bivariant optimization method for the mobile phase SDS-tetrahydrofuran corroborated the above results. The effect of temperature on the retention was also studied, and 50 degrees C was selected. The optimized method was applied to human urine samples of subjects administered Diurex (tablets containing 20 mg of the active ingredient xipamide) without sample preparation.

Calibration↗
PubMed2005

Complex mixture toxicity for single and multiple species: proposed methodologies.

Methods for the assessment of ecological risks associated with exposure to defined mixtures of toxicants are reviewed and formalized for single-species toxicity. Depending on the modes of action of toxicants in a mixture, these methods apply either the model for concentration additivity (CA) or the model for response additivity (RA). For complex mixtures, the present paper advocates the use of a new, two-step, mixed-model approach as a logical extension of model selection: Mixture toxicity for individual modes of action is evaluated with the CA model, and the toxicities of different modes of action are combined using the RA model. Using comparable mixture toxicity strategies in combination with the concept of species-sensitivity distributions, we develop a method to address and predict the risk for direct effects on the composition of species assemblages and biodiversity. The data needed for modeling can be obtained from existing databases, and lack of data can, in part, be addressed by the use of toxicity patterns in those databases. Both single- and multiple-species methods of mixture risk prediction are useful for risk management, because they allow ranking of polluted sites and affected species as well as identification of the most hazardous contaminants, at least in a comparative way. Validation of the proposed methods is feasible but currently limited because of a lack of appropriate data.

Animals↗
PubMed1989

Measurement of deoxyguanosine/thymidine ratios in complex mixtures by high-performance liquid chromatography for determination of the mole percentage guanine + cytosine of DNA.

The ratio of deoxyguanosine and thymidine can be determined in a complex mixture containing the major ribonucleosides and deoxynucleosides, the minor deoxynucleosides, and the nucleotide monophosphates by high-performance liquid chromatography. The isocratic procedure utilizes a C18 column and a solvent of methanol-triethylamine phosphate (pH 5.1). A single analysis requires 15 min. Within the range of 0.5-1.5 micrograms of total deoxynucleosides per sample, the determination is very precise and the relative standard deviation is about 0.1%. From the deoxyguanosine/thymidine ratio, a precise determination of the mole percentage guanine + cytosine of double-stranded DNA is calculated.

Archaea↗
PubMed1996

High-resolution anion-exchange and partition thin-layer chromatography for complex mixtures of 32P-postlabeled DNA adducts.

32P-Postlabeling has emerged as a major tool for detecting DNA adducts resulting from exposure to complex carcinogen mixtures. An integral component of this assay is multi-directional PEI-cellulose TLC in which lipophilic 32P-adducts are resolved in high-salt, high-urea solvents following removal of the bulk of non-adduct radioactivity. This TLC system is very effective for adducts formed following exposure to individual carcinogens; however, adducts resulting from exposure to complex mixtures (e.g. cigarette smoke) generally appear in the form of the so-called diagonal radioactive zones. By using mixtures of polycyclic aromatic hydrocarbon- and aromatic amine-DNA adducts as well as adducts in mouse skin treated with cigarette smoke condensate, we have demonstrated that a combination of 0.3-0.4 M NH4OH and isopropanol-4 M NH4OH (1-1.4:1) solvents can provide more sharply defined adduct spots than the commonly used urea solvents. The non-urea solvents also result in excellent resolution of many adducts which otherwise may remain buried in diagonal radioactive zones when using the urea solvents. In addition, the signal-to-noise ratio is increased 2- to 5-fold over the urea solvents enabling detection of discrete adducts at < or = 3 adducts per 10(10) nucleotides. These partition TLC solvents also involve fewer manipulations (e.g. no water washes to remove salt and urea), and are likely to be more informative with regards to the type of individual adducts detected in the biomonitoring of humans than has hitherto been possible.

Animals↗
PubMed2006

The design of a multi-dimensional LC-SPE-NMR system (LC(2)-SPE-NMR) for complex mixture analysis.

In this communication, we describe the design of an online multi-chromatographic approach to the routine NMR analyses of low-level components ( approximately 0.1%) in complex mixtures. The technique, termed LC(2)-SPE-NMR, optimally combines multi-dimensional liquid chromatography with SPE technology for isolating, enriching and delivering trace analytes to the NMR probe. The fully automated LC(2)-SPE-NMR system allows for maximal loading capacity (in the first, preparative LC dimension), close to optimal peak resolution (in the second, analytical LC dimension) and enhanced sample concentration (through SPE). Using this system, it is feasible to conveniently conduct a wide range of NMR experiments on, for example, drug impurities at the low microgram per milliliter level, even for components poorly resolved in the first dimension. Such a sensitivity gain significantly elevates the analytical power of online NMR technology in terms of the level at which substances of pharmaceutical significance can be structurally characterized.

Chromatography, Liquid↗
PubMed2004

Comprehensive two-dimensional separations of complex mixtures using reversed-phase reversed-phase liquid chromatography.

A comprehensive two-dimensional reversed-phase reversed-phase liquid chromatographic system for the separation of a complex mixture of oligostyrenes was developed using results from a previous theoretical assessment of the informational similarity, percent synentropy, orthogonality and peak capacity of hypothetically coupled systems. The degree of sample attribute order in the first separation dimension was also used in the development of the experimental two-dimensional system. A C18(methanol)/CCZ(acetonitrile) two-dimensional system was chosen for the comprehensive analysis of the oligostyrene mixtures because this system had the lowest solute crowding, highest orthogonality and was observed to have order with respect to a sample attribute in the first separation dimension. The separations achieved were in full agreement with the results from information theory and (a geometric approach to) factor analysis assessments. High sampling rates in the first liquid chromatographic dimension were shown to be impossible or inefficient when the peak capacity and separation time of the second dimension was high or when the aim of the exercise was to isolate individual sample constituents in high yield.

Chromatography, Liquid↗
PubMed2006

NMR diffusion measurements in complex mixtures using constant-time-HSQC-IDOSY and computer-optimized spectral aliasing for high resolution in the carbon dimension.

A new 3D pulse sequence for NMR diffusion measurements in complex mixtures is presented. It is based on the constant-time (CT) HSQC experiment and combines diffusion delay with the carbon evolution time. This combination has great potential to obtain high resolution in the carbon dimension. When using classical sampling of the carbon dimension, maximal resolution would require a large number of time increments, leading to unrealistically long acquisition times. The application of computer-optimized spectral aliasing allows one to reduce the number of time increments and the total acquisition time by 1-2 orders of magnitude by taking advantage of the information content of 1D carbon spectra, HSQC experiments, or both. With the new CT-HSQC-IDOSY experiment, the diffusion rates of the six anomers present in a 0.1 M D2O solution of glucose, maltose, and maltotriose could be obtained at natural abundance in 8 h with standard deviations below 5%.

Carbon↗
PubMed1979

Toxaphene, a complex mixture of polychloroterpenes and a major insecticide, is mutagenic.

Toxaphene, the most widely used chlorinated insecticide, is mutagenic in the Salmonella test without requiring liver homogenate for activity. This insecticide is a complex mixture (more than 177 polychloroterpenes) with carcinogenic activity in rodents. Some but not all of the mutagenic components are easily separated from the insecticidal ingredients.

Dose-Response Relationship, Drug↗
PubMed1991

A high-yield sampler for toxicological characterization of complex mixtures in combustion effluents.

Combustion sampling for toxicological assessment often requires that large (greater than 100 mg) lots of complex organic mixtures of wide volatility range be rapidly recovered from high temperature gases without contamination. A new sampler, meeting these criteria for studies of public health interest, has been developed and demonstrated. The device provides high sampling rates and intimate contacting of the samples stream with large volumes of a well-cooled, liquid solvent, dichloromethane (DCM). This promotes rapid organics dissolution from carrier gas and particulates and prompt dilution and quenching of the resulting solution, resulting in high organics collection efficiencies with minimal DCM losses. Solvent separation then remits large quantities of concentrated organics for chemical analysis and toxicological testing. One- to seven-hour interrogations of in-flame, post-flame, and flue gas regions gave 50- to 250-mg yields of complex organic mixtures. In side-by-side sampling of combustion exhaust, the DCM sampler provided higher yields of DCM solubles (identified with complex organic mixtures) and of S. typhimuirim mutagens (active without exogenous metabolizing agents) than did a filter/polymeric sorbent bed sampling train. The new sampler also collects polar and high volatile hydrocarbons such as benzaheyde, pentadiyne, m- and p-diethynyl-benzene, and 1-hexen-3,5-diyne. Nitration of naphthalene and pyrene in DCM solution (1 mg/mL each) was less than 1 part in 10(7) after a 345-min exposure to a bubbling flow of moist N2/air mixture (1:1 v/v) containing 107 ppm NO and 1.5 ppm NO2, indicating that for these condition a DCM sampler should resist artifactual nitration of aromatics. However, because of the very high bacterial mutagenicity of some nitroaromatics and the wide range of sampling conditions of environmental interest, nitration and all artifacts must still be scrutinized when using the DCM sampler. The DCM sampler is expected to contribute to public health impact assessments by facilitating detailed determinations of the identities, compositions, concentrations, sources, formation mechanisms, and biological activity of environmental toxicants in gaseous atmospheres.

Atmospheric Pressure↗
PubMed2001

Analysis of complex mixtures recovered from space missions statistical approach to the study of Titan atmosphere analogues (tholins).

To study Titan, the largest moon of Saturn, laboratory simulation experiments have been performed to obtain analogues of Titan's aerosols (named tholins) using different energy sources. Tholins, which have been demonstrated to represent aerosols in Titan's haze layers, are a complex mixture, resulting from the chemical evolution of several hydrocarbons and nitriles. Their chromatographic analysis yields complex chromatograms, which require the use of mathematical procedures to extract from them all the information they contain. Two different chemometric approaches (the Fourier analysis approach and the statistical model of peak overlapping) have been successfully applied to pyrolysis-GC-MS chromatogram of a tholin sample. Fundamental information on the mixture's chemical composition (number of components, m) and on the separation system performance (separation efficiency, sigma) can be easily estimated: the excellent correspondence between the data calculated by the two independent procedures proves the reliability of the statistical approaches in characterizing a tholin chromatogram. Moreover, the plot of autocorrelation function contains, in a simplified form, all the information on the retention pattern: retention recursivities can be easily singled out and related to specific molecular structure variations. Therefore, the autocorrelation function (ACF) plot constitutes a simplified fingerprint of the pyrolysis products of tholins, which can be used as a powerful tool to characterize a tholin sample.

Aerosols↗
PubMed1989

Carcinogenic risk assessment of complex mixtures.

Although procedures for assessing the carcinogenic risks associated with exposure to individual chemicals are relatively well developed, risk assessment methods for mixtures of chemicals are still in the developmental stage. In this paper, we examine the difficulties in assessing the risks of exposure to complex mixtures, with special reference to the potential for synergistic effects among the components of the mixture. Statistical models for describing the joint action of multiple exposures are reviewed, and their implications for low-dose risk assessment are examined. The potential use of pharmacokinetic models to describe the metabolism of mixtures is also considered. Application of these results in regulating mixtures of carcinogenic substances is illustrated using examples involving multiple contaminants in drinking water and polycyclic aromatic hydrocarbons produced from combustion sources.

Carcinogenicity Tests↗
PubMed1990

[Analysis of methodological approach to the evaluation of toxicity of complex mixtures of relatively constant composition used in industry (review of the literature)].

Basing on literature data and the author's personal experience, the article displays current approaches to the toxicological assessment of industrial complex mixtures with permanent compositions. These include two main approaches to the detection of major components: a) the establishment of the individual substances ratio in the toxicological parameters, and b) the application of the regression coefficients and their derivatives. Toxicity assessment against the toxicological parameters of individual substances is also substantiated.

Air Pollutants, Occupational↗
PubMed2000

Signature-peptide approach to detecting proteins in complex mixtures.

The objective of the work presented in this paper was to test the concept that tryptic peptides may be used as analytical surrogates of the protein from which they were derived. Proteins in complex mixtures were digested with trypsin and classes of peptide fragments selected by affinity chromatography, lectin columns were used in this case. Affinity selected peptide mixtures were directly transferred to a high-resolution reversed-phase chromatography column and further resolved into fractions that were collected and subjected to matrix-assisted laser desorption ionization (MALDI) mass spectrometry. The presence of specific proteins was determined by identification of signature peptides in the mass spectra. Data are also presented that suggest proteins may be quantified as their signature peptides by using isotopically labeled internal standards. Isotope ratios of peptides were determined by MALDI mass spectrometry and used to determine the concentration of a peptide relative to that of the labeled internal standard. Peptides in tryptic digests were labeled by acetylation with acetyl N-hydroxysuccinimide while internal standard peptides were labeled with the trideuteroacetylated analogue. Advantages of this approach are that (i) it is easier to separate peptides than proteins, (ii) native structure of the protein does not have to be maintained during the analysis, (iii) structural variants do not interfere and (iv) putative proteins suggested from DNA databases can be recognized by using a signature peptide probe.

Amino Acid Sequence↗
PubMedDate not supplied

Overview, conclusions, and recommendations of the IPCS collaborative study on complex mixtures.

The International Programme on Chemical Safety (IPCS) sponsored an international collaborative study to examine the variability associated with the extraction and bioassay of standard reference materials (SRMs) that are complex environmental mixtures provided by the U.S. National Institute of Standards and Technology (NIST). The study was also intended to evaluate the feasibility of establishing bioassay reference values and ranges for the SRMs. Twenty laboratories from North America, Europe, and Japan participated in the study. As part of the mandatory core protocol, each laboratory extracted the organic material from two particulate samples and bioassayed these extracts. A coal tar polycyclic aromatic hydrocarbon (PAH) solution and two mutagenic control compounds were also subjected to bioassay without prior extraction by the participating laboratories. The bioassay used was the Salmonella/microsomal plate incorporation assay. For the optional portion of the study, a laboratory was free to use the SRMs for any type of exploratory research. The primary purpose of the required portion of the study was to estimate the intra- and inter-laboratory variability in mutagenic potencies of the test materials and to determine whether or not the NIST mixtures could be used as reference materials by others performing the Salmonella assay. Repeatability (intra-laboratory variance) of the bioassay results ranged from 16% to 88% depending on the SRM and the bioassay conditions (tester strain and metabolic activation), whereas reproducibility (inter-laboratory variance) ranged from 33% to 152%. Between-laboratory variability was the main source of variation accounting for approximately 55-95% of the total variation for the three environmental samples. Variation in the mutagenic potency of the control compounds was comparable, with the exception of 1-nitropyrene for which the reproducibility ranged from 127% to 132%. In summary, NIST SRMs provided useful materials for an international inter-laboratory study of complex mixtures. By establishing both intra- and inter-laboratory variance for the mutagenicity results for these materials, the usefulness of these SRMs as reference materials for the Salmonella bioassay was established, critical procedures within the bioassay protocol were identified, and recommendations for future efforts were delineated.

International Cooperation↗
PubMed1999

Affinity mass spectrometry-based approaches for the analysis of protein-protein interaction and complex mixtures of peptide-ligands.

Combined applications of affinity purification procedures and mass-spectrometric analyses (affinity mass spectrometry or affinity-directed mass spectrometry) have gained broad interest in various fields of biological sciences. We have extended these techniques to the purification and analysis of closely related peptides from complex mixtures and to the characterization of binding motifs and relative affinities in protein-protein interactions. The posttranslational modifications in the carboxy-terminal region of porcine brain tubulin are used as an example for the applicability of affinity mass spectrometry in the characterization of complex patterns of related peptides. We also show that affinity mass spectrometry allows the mapping of sequential binding motifs of two interacting proteins. Using the ActA/Mena protein-protein complex as a model system, we show that we can selectively purify Mena-binding peptides from a tryptic digest of ActA. The results from this assay are compared to data sets obtained earlier by classical methods using synthetic peptides and molecular genetic experiments. As a further expansion of affinity mass spectrometry, we have established an internally standardized system that allows comparison of the affinities of related ligands for a given protein. Here the affinities of two peptide ligands for the monoclonal tubulin-specific antibody YL1/2 are determined in terms of half-maximal competition.

Amino Acid Sequence↗
PubMed2001

Molecular characterisation of a complex mixture of viruses in garlic with mosaic symptoms in China.

Degenerate primers were used to detect and amplify cDNA of viruses of the genera Carlavirus, Allexivirus and Potyvirus from garlic plants with mosaic symptoms growing in Zhejiang province, China. Plants contained a complex mixture of viruses and strains. Three distinct stains of Garlic latent virus were detected; the most frequent one was completely sequenced and partial sequences were obtained for the other two. The complete sequence (8363 nt) was 76.4% identical to a Korean isolate. Two allexiviruses were detected and completely sequenced. One (8319 nt) was identified as Garlic virus X and comparisons showed that a published Korean isolate (which had 90.2% identical nucleotides) had an N-terminal deletion in the serine-rich ORF4. The other isolate (8451 nt), tentatively named Garlic virus E, appeared to be a new member of the genus. Phylogenetic analyses of the different viral proteins and distinctive conserved sequence motifs within the genus are discussed. This is the first report of allexiviruses from China. Using potyvirus primers, three distinct isolates of Onion yellow dwarf virus and one of Leek yellow stripe virus were detected and the 3'-terminal sequences of their genomes were determined. In a coat protein phylogenetic analysis, the new isolates were most closely related to other published isolates from Japan and China.

Amino Acid Sequence↗