Chromatographic methods for the determination of toxicants in faeces.

Modern chromatographic techniques and their application in the determination of toxic compounds in faeces are reviewed. Faecal analysis may be of importance in toxicokinetic studies of xenobiotics in order to determine factors such as metabolism, body burden and major routes of elimination. Compounds of interest include various food constituents, drugs and occupational or environmental factors. Further, various mutagenic or carcinogenic compounds which are excreted by faeces have been indicated to represent risk factors for colorectal cancer. In this context, the chromatographic determination of the endogenously generated fecapentaenes and bile acids, both postulated etiological factors in colorectal carcinogenesis, is reviewed. For fecapentaene determination, several high-performance liquid chromatographic (HPLC) methods are available; however, the applicability of some of these methods is limited owing to insufficient separation of various isomeric forms or discrimination between fecapentaenes and their precursors. For the determination of bile acids in faeces, many chromatographic procedures have been reported, and the characteristics of the most relevant methods are compared and discussed. It is concluded that separation by gas chromatography (GC) in combination with mass spectrometry provides the highest selectivity and sensitivity. A relatively rapid alternative analysis for the determination of total and aqueous faecal bile acids is proposed. Further, methods for the determination of polycyclic aromatic hydrocarbons (PAHs) are reviewed. Although the use of radiolabelled PAHs in animal studies has many advantages, it cannot be applied for human biological monitoring and HPLC and GC provide sensitive alternatives. An HPLC method for the determination of non-metabolized PAHs in faeces is described.     

Separation and identification of some common isomeric plant triterpenoids by thin-layer chromatography and high-performance liquid chromatography

Chromatographic separation of 10 triterpenoids (α-amyrin, β-amyrin, δ-amyrin, lupeol, lupenon, lupeol acetate, cycloartenol, cycloartenol acetate, ursolic acid, oleanolic acid) and 2 sterols (stigmasterol and β-sitosterol) was studied. The chromatographic techniques included silica gel and reversed-phase (C₁₈ RP) thin-layer chromatography (TLC) and C₁₈ RP high-performance liquid chromatography (HPLC) using UV and mass spectrometric (MS) detection with atmospheric pressure chemical ionization (APCI). The TLC separation of the isomeric triterpenols lupeol, α-amyrin, β-amyrin and cycloartenol was achieved for the first time using C₁₈ RP-HPTLC plates. Cycloartenol could be separated from related compounds only on C₁₈ RP-TLC but not on the C₁₈ RP-HPLC. δ-Amyrin isolated from the tomato fruit surface extract could be separated from other amyrins only by HPLC. Tandem mass spectrometry allowed discrimination between the isomers lupeol, α-amyrin, β-amyrin, δ-amyrin, cycloartenol and between lupeol acetate and cycloartenol acetate. The combination of 3 TLC methods and 2 HPLC methods enables qualitative determination of all 12 compounds and proves to be useful for the analysis of plant extracts. It is recommended that TLC screening on silica gel and C₁₈ RP be performed before HPLC analysis.     

Behaviour of some organic micropollutants in river sediments and groundwater

Summary Organic micropollutants can reach the ground-water zone by various routes including direct contact with the surface water. River sediments play a substantial role, not only as a concentrating medium but also in their elimination of these substances. The behaviour of polycyclic aromatic hydrocarbons and halogenated compounds is investigated in laboratory experiments, filter plants, sediments and in the ground water. For analyses, Chromatographic methods (GC, TLC, HPLC) and mass spectrometry are employed. Statistical techniques such as principal component analysis and time series analysis are employed for data reduction and evaluation. The application of these methods together with empirical sorption and degradation experiments allow the influence of organic micropollutants on the ground water to be estimated.

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Verhalten einiger organischer Schadstoffe in Flußsedimenten und Grundwasser

Zusammenfassung Organische Schadstoffe können auf vielfache Art in den Grundwasserbereich gelangen, unter anderem durch unmittelbaren Kontakt mit Oberflächengewässern. Flußsedimente spielen in diesem Zusammenhang eine wesentliche Rolle als Medien zur Anreicherung, aber auch zur Eliminierung dieser Substanzen. Es wird berichtet über das Verhalten polycyclischer aromatischer Kohlenwasserstoffe und halogenhaltiger Schadstoffe in Laborversuchen, Filtereinrichtungen, Sedimenten und im Grundwasserbereich. Als Analysenverfahren werden chromatographische Methoden (GC, TLC, HPLC) sowie die Massenspektrometrie verwendet. Zur Datenauswertung werden statistische Verfahren wie die Hauptkomponentenanalyse und die Zeitreihenanalyse herangezogen. Diese Methoden ermöglichen es, gemeinsam mit empirischen Versuchen zum Sorptions- und Abbauverhalten, die Beeinflussung des Grundwassers mit organischen Schadstoffen abzuschätzen.

     

The Use of Thin-Layer Chromatography in Experimental Xenobiology

Abstract

Studies of the metabolism and disposition of most drugs or other xenobiotics share one common feature: the need for an analytical method to measure the xenobiotic and/or its biotransformation products in biosamples. Although chromatographic methods such as GC and HPLC are important and preferred by some laboratories, initial investigations of new xenobiotic entities are often conducted using radiolabeled compounds, and, in such instances, TLC assay methods are frequently selected.

TLC is utilized in xenobiotic metabolism and disposition studies to evaluate the radiochemical purity of labeled xenobiotics, the extent of metabolism, the profile of metabolites in blood and excreta, the concentrations of the xenobiotic and specific metabolites in blood and other biosamples, the stability of the xenobiotic and its metabolites in biosamples, and the relative behavior of metabolites and reference compounds. Preparative TLC is frequently used to isolate specific metabolites. Thin-layer radiochromatography (TLRC) has been utilized to study the pharma-cokinetics of drugs and other xenobiotics in man and in animals. Especially where radiolabeled compounds are used, TLC provides an attractive chromatographic alternative to GC and HPLC in research in experimental xenobiology.     

Chromatography of Trichothecene Mycotoxins

Abstract

Trichothecene mycotoxins occur in agricultural commodities and can cause problems from feed refusal to death in animals. This paper describes chromatographic methods for selective analysis for trichothecene mycotoxins. These methods include gas chromatography (GC), thin layer chromatography (TLC), and high pressure liquid chromatography (HPLC). The trichothecene analysis methods by GC and TLC are shown to have a greater sensitivity than in HPLC for the underivatized mycotoxins.     

Analysis of polycyclic aromatic hydrocarbons in solid sample material using a desorption device coupled to a GC/MS system

Summary Polycyclic aromatic hydrocarbons (PAH) today are ubiquitous detectable constituents of recent sediments. The compounds are adsorbed on particulate emissions and are thus transferred to the environment. To date the analysis of PAH in sediments, dust samples and plant material is based mainly on the application of solvent-extraction methods followed by liquid chromatography and/or gas chromatographic separation of the extracts.An alternative approach for the analysis of PAH in solid samples such as coal, sediments, dust samples and plant waxes is shown in this contribution. A commercially available device for the analysis of volatile compounds present in solid matter is connected on-line to a GC/MS system. The device enables the thermal desorption of hydrocarbons at a temperature of 320°C. Subsequently, the hydrocarbons trapped on the initial part of the capillary column are analyzed by GC/MS. The application of mass chromatography provides the possibility of detection and quantitation of PAH in complex mixtures even when they coelute with other compounds. The sample amount required varies between 1 and 10 mg depending on the hydrocarbon content.     

Arzneimittel- und Drogenscreening aus Urin mittels DC unter besonderer Berücksichtigung von Reagentien mit geringer toxischer Belastung für Laborpersonal und Umwelt

Summary A technique is presented for the extraction of free and conjugated drugs and related compounds out of small quantities of urine. The method is designed in such a way that many samples can be tested for a great number of substances at the same time. Furthermore, we tried to achieve a high quality analysis using when ever possible chemicals with relatively low toxicity to men and environment. Therefore we avoided e.g., halogenated hydrocarbons. The detection of the substances is only performed by thin-layer chromatography (TLC) using well known reagents, like ninhydrin, Dragendorff, iodoplatinate and ferric chloride solutions. If necessary, the extracts can also be used with other Chromatographic techniques, particularly with GC/MS, if a substance has to be clearly identified. Approximately 500 authentical urines have been analyzed in a 1 year period using the method described. We found about 75 different substances. These results are presented in a table.     

Fast determination of tetracycline antibiotics in different media by high-performance liquid chromatography

Summary The use of high-performance liquid chromatography (HPLC) for the identification and determination of tetracycline antibiotics is reviewed. HPLC chromatograms provide fast identification by retention time, t_R, and precise quantitation by measurement of peak height or peak area. For separation of tetracycline compounds, most HPLC methods use reversed-phase C₁₈ or C₈ columns and UV detection. The HPLC solvent system should have a pH of about 6 to prevent steric changes in the tetracycline molecule. For accurate quantitation it is necessary to avoid tailing and this is accomplished by adding a zwitter ion to the solvent system. Methanol and acetonitrile are frequently used as organic modifiers in these solvent systems. In a single analysis, HPLC methods can be used to separate as many as nine or ten commercially used tetracycline compounds and to determine four to five tetracyclines in commercial tetracycline preparations or in biological fluids.     

The role of electric interaction in the retention index cencept. Universal interaction indices for GLC,HPLC and TLC

Summary New electric interaction indices are proposed which can universally be used in GLC, HPLC and TLC. These indices can easily be calculated from a variety of the commonly used retention parameters, such as Kováts' retention indices, relative retention times, capacity factors, or R_F values, and the average molecular polarizabilities of the reference compounds. Calculation examples for polycyclic aromatic hydrocarbons and n-alkanes are given. Application of the electric interaction indices for studying the retention mechanism is demonstrated.     

Characterization of fuel samples by on-line LC-GC with automatic group-type separation of hydrocarbons

Characterization of fuels by LC-GC is possible by use of automatic successive transfer (multiple transfer) of HPLC fractions to a GC via an on-column interface. This paper describes the instrumentation and the methodology for the HPLC separation of the hydrocarbons (aliphatic and aromatic) into separate groups and the on-line transfer of these groups to a capillary GC column. Two HPLC methods were used with the same valve configuration: single column (silica) with column back-flush to detector; and double column (silica and amino-bonded silica) with multiple fraction transfer and back-flush. The first method was used for the analysis of total saturated compounds and total aromatic compounds; the second was used for the separation of the one-, two-, three-, and four-ring aromatic compounds present in diesel fuels. Examples are shown of the characterization of diesel fuels, and the repeatability of the data.     

Compound-specific stable isotope analysis of organic contaminants in natural environments: a critical review of the state of the art,prospects, and future challenges

Compound-specific stable isotope analysis (CSIA) using gas chromatography-isotope ratio mass spectrometry (GC/IRMS) has developed into a mature analytical method in many application areas over the last decade. This is in particular true for carbon isotope analysis, whereas measurements of the other elements amenable to CSIA (hydrogen, nitrogen, oxygen) are much less routine. In environmental sciences, successful applications to date include (i) the allocation of contaminant sources on a local, regional, and global scale, (ii) the identification and quantification of (bio)transformation reactions on scales ranging from batch experiments to contaminated field sites, and (iii) the characterization of elementary reaction mechanisms that govern product formation. These three application areas are discussed in detail. The investigated spectrum of compounds comprises mainly n-alkanes, monoaromatics such as benzene and toluene, methyl tert-butyl ether (MTBE), polycyclic aromatic hydrocarbons (PAHs), and chlorinated hydrocarbons such as tetrachloromethane, trichloroethylene, and polychlorinated biphenyls (PCBs). Future research directions are primarily set by the state of the art in analytical instrumentation and method development. Approaches to utilize HPLC separation in CSIA, the enhancement of sensitivity of CSIA to allow field investigations in the µg L^–1 range, and the development of methods for CSIA of other elements are reviewed. Furthermore, an alternative scheme to evaluate isotope data is outlined that would enable estimates of position-specific kinetic isotope effects and, thus, allow one to extract mechanistic chemical and biochemical information.Abbreviations BTEX benzene, toluene, ethylbenzene, xylenes - MTBE methyl tert-butyl ether - PAHs polycyclic aromatic hydrocarbons - VOCs volatile compounds - PCBs polychlorinated biphenyls - CSIA compound-specific (stable) isotope (ratio) analysis - GC-IRMS, GC/IRMS or GCIRMS gas chromatography-isotope ratio mass spectrometry - GC-C-IRMS, GC/C/IRMS or GCC-IRMS gas chromatography-combustion-isotope ratio mass spectrometry - irmGC/MS isotope ratio monitoring gas chromatograph-mass spectrometry - GC/P/IRMS gas chromatography-pyrolysis-isotope ratio mass spectrometry (used for D/H) - KIE kinetic isotope effect - PSIA position-specific isotope analysis (for intramolecular isotope distribution) - SNIF-NMR site-specific natural isotopic fractionation by nuclear magnetic resonance spectroscopy     

Improving the selectivity of non-polar alkanes, alkenes, and aromatic hydrocarbon compounds by the application of acetonitrile as a Cl reagent

The selective enhancement of membrane introduction mass spectrometry for non-polar alkanes, alkenes, and aromatic hydrocarbon compounds by the application of acetonitrile as a chemical ionization reagent was investigated. Acetonitrile Cl is able to produce specific fragment ions for many of the compounds test and this can be used to identify and quantify the parent neutrals. This method provided relatively high detection limits of the test compounds. This method could potentially be useful for analytical applications such as the detection of non-polar hydrocarbons for environmental studies if CH₃CN Cl/MIMS is coupled with a preconcentration method.     

Thin-layer chromatography (TLC) as pilot technique for HPLC. Utilization of retention database (R F) vs. eluent composition of pesticides

Summary TLC and HPLC are frequently unjustly regarded as competitive methods. Using the advantages of both methods, a combination of TLC and HPLC leads to a considerable saving of time and expense in analysis. Experimental data are presented aslog k (HPLC) vs.R _M (TLC) correlations; high correlation coefficients indicate that TLC using octadecyl silica, wettable with water (RP-18W) can be applied as a pilot technique for HPLC (RP-18).     

Evaluation of clean-up agents for total petroleum hydrocarbon analysis in biota and sediments

Petroleum hydrocarbons (oil) are common environmental contaminants. For risk assessment purposes, their concentrations in environmental matrixes, such as biota and soils/sediments are frequently determined by solvent extraction and subsequent analysis with gas chromatography (GC) equipped with flame ionization detection (FID) or mass spectrometry (MS). Because the total GC detector response is labeled as total petroleum hydrocarbon (TPH) concentration and matrix compounds (lipids, organic matter) will contribute to this response, proper extract clean-up is crucial. Still, the choice for a specific clean-up material during open column chromatography often seems arbitrary, since no comparative study on clean-up agents for TPH analysis is available. Here, such a study is described and it is demonstrated that none of the commonly used agents fulfills the requirements of complete matrix compound removal and TPH recovery. A novel column filled with (top-down) 1 g of 33% (w/w) 1 M NaOH-impregnated and 2.2 g of 7% (w/w) H₂SO₄-impregnated silica gel is recommended for cleaning-up biota extracts, as it fully removes extracted lipids and yields acceptable TPH recoveries of around 90%, based on a certified oil reference standard. For sediment extracts, most columns tested resulted in a negligibly low contribution of matrix compounds to the overall detector response, but 5% deactivated Florisil or 10% deactivated aluminum oxide are preferable, because these materials yield the highest (∼95%) TPH recoveries.     

Chromatographic methods as tools in the field of mycotoxins

Achievements in the applications of chromatographic techniques in mycotoxicology are reviewed. Historically, column chromatography (CC) and paper chromatography (PC) were applied first, followed by thin-layer chromatography (TLC), high-performance liquid chromatography (HPLC) and gas chromatography (GC). Although PC techniques are no longer used in the analysis of mycotoxins, selected applications of PC are included to underline historical continuity. The most important achievements published from 1980 onwards are described. They include clean-up methods, TLC, CC, HPLC and GC of mycotoxins in environmental samples, foods, feeds, body fluids and in studies on biosynthesis and biotransformations of mycotoxins. Advantages and disadvantages of chromatographic techniques used in mycotoxicology are also evaluated.     

药物分析 (Ⅰ)

对国内药物分析在2005~2006年的主要进展进行评述。内容包括高效液相色谱法、气相色谱法、毛细管电泳法、薄层色谱法、分光光度法和其它分析方法等。另外,对高效液相色谱法和气相色谱法的不同联用技术进行分别评述。共引用文献3294篇。     

药物分析 (Ⅱ)

对国内药物分析在2005~2006年的主要进展进行评述。内容包括高效液相色谱法、气相色谱法、毛细管电泳法、薄层色谱法、分光光度法和其它分析方法等。另外,对高效液相色谱法和气相色谱法的不同联用技术进行分别评述。共引用文献3294篇。     

GC/IMS and GC/MS analysis of pre-concentrated medical and biological samples

Ion mobility spectrometry (IMS) is a well-known analytical method for the detection of CWAs and explosives since many years. Coupling IMS to GC pre-separation, new application fields in medicine and biology could be opened, dealing with complex and humid mixtures. However, identification of unknowns in such a complex sample is challenging and can only be achieved by parallel GC/MS analysis, thus obtaining a proposal for the responsible compound for validation via reference substances by GC/IMS again. The available adsorption tools for such accompanying GC/MS analysis have their particular drawbacks (e.g. problematic quantification for SPME, high sample volumes for adsorption tubes). Therefore miniaturised adsorption needles (NeedleTrap) were applied to both GC/IMS and GC/MS for validation of their reproducibility. It could be demonstrated that the needles can even be used for appropriate quantification when the adsorbent and the sample volume are adapted properly to the concentration range, the compounds of interest and humidity of the sample. The method is very flexible with regard to the concentration range by variation of the sample volume (e.g. 20 mL for ppt_V, 10 mL for lower ppb_V or 1 mL for ppm_V) and with regard to the compounds of interest by application of common adsorption materials optimised for the relevant substance group. Such materials are available commercially in a broad variability. Therefore, the miniaturised adsorption needles are a helpful complementary sampling method for any GC/MS or GC/IMS investigations.