Identification of phenols of 7,12-dimethylbenz[a]anthracene by conversion into their methyl ethers

The compound 7,12-dimethylbenz[a]anthracene (DMBA), a powerful chemical carcinogen, undergoes enzymatic oxidation to a variety of metabolites. Phenols, the monohydroxylated derivatives of DMBA, are an electrophilic species capable of binding covalently with DNA. Although phenols may play a role in carcinogenesis, little information is available regarding these metabolites, many of which are chemically unstable and elusive to quantitative analysis. In this study, a method is described for the methylation of phenolic products to their chemically stable methyl ether derivatives. Application of this procedure to in vitro incubations of DMBA with rat liver microsomes resulted in the isolation and identification of 4-hydroxy DMBA, 8-hydroxy DMBA and 3-hydroxy DMBA.     

Determination of [S,S']-ethylenediaminedisuccinic acid by high-performance liquid chromatography

A new high-performance liquid chromatography (HPLC) method for the determination of ethylenediaminedisuccinic acid (EDDS) is presented. Free EDDS(4-) and EDDS complexes with divalent metals undergo conversion to the Fe(III) complex in the presence of Fe(III)Cl(3). Fe(III)EDDS is separated by HPLC on an ion exchange column using (NH(4))(2)SO(4) eluent with detection at 258 nm. The detection limit is 0.01 microM. The method is applied to natural waters and soil solution samples. A background of natural water results in a reduction in EDDS peak area. The method is suited for EDDS analysis in samples with well-defined, simple matrices such as those used in laboratory experiments or biodegradation studies.     

Determination of airborne particle-associated benz[a]anthracene-7,12-quinone using high-performance liquid chromatography with in-line reduction and fluorescence detection

A simple and sensitive method for measuring airborne particle-associated benz[a]anthracene-7,12-quinone (BaAQ) based on two-dimensional high-performance liquid chromatography (HPLC) with fluorescence detection was established. The system involves an ODS column for sample clean up, a 6-port switching valve, an ODS column for trapping the fraction containing BaAQ, an ODS column for sample separation, and a Pt-Rh catalytic column for reduction of BaAQ to a corresponding fluorescent compound. The accuracy of the assay, as applied to airborne particulate sample extracts spiked with known amounts of BaAQ was 94–108%. The detection limit was 97 fmol per injection (signal-to-noise ratio = 3), and the calibration range was from 1 to 100 pmol with excellent proportionality (R² = 0.9995). BaAQ in airborne particles collected in Osaka, Japan every 3 h was successfully measured using the established analytical method with simple sample preparation steps: ultrasonic extraction in organic solvent and concentration under reduced pressure and/or nitrogen stream.     

Determination of aprotinin by high-performance liquid chromatography

Summary A highly accurate and reproducible method for the determination of aprotinin (bovine pancreatic trypsin inhibitor) by HPLC is described. In the experiments, the relative standard deviation was 1.2% and detection limit 1 FIP-U cm^–3. Also, the method is quick and selective and active ingredients from difference source correlate well with enzymatic method. Analyses at different laboratories can be compared directly.     

Determination of thiamine by high-performance liquid chromatography

High-performance liquid chromatographic methods for the determination of thiamine (vitamin B1) in foodstuffs or biological tissues and fluids are outlined and discussed. The methods are often similar and interchangeable, sample extraction and clean up procedures being the major difference. Most of the methods use either ultraviolet or fluorescence detection. Fluorescence detection requires either precolumn or postcolumn oxidation of thiamine to thiochrome. A number of methods are recommended and problems with standardization are emphasized.     

Determination of beta-carbolines in foodstuffs by high-performance liquid chromatography and high-performance liquid chromatography-mass spectrometry

A high-performance liquid chromatographic method combined with fluorimetric detection is described for the determination of beta-carboline (norharman) and 1-methyl-beta-carboline (harman). The analysis of foodstuffs for the identification of beta-carbolines is facilitated by clean-up samples using Bond Elut PRS cartridges. Recoveries were excellent. Further, a high-performance liquid chromatographic-mass spectrometric method was also developed for their identification. The concentration of beta-carboline among the foodstuffs and alcoholic beverages varied greatly. Also, norharman and harman were observed in uncooked foodstuffs, whereas acetaldehyde was found in most fermented food. The toxicological implication of beta-carbolines in foodstuffs is discussed.     

Determination of a new orally active cephalosporin in human plasma and urine by high-performance liquid chromatography using automated column switching

Analytical procedures have been investigated for the separation, detection, identification and quantitation of some metabolites of N-benzyl-4-substituted anilines. Techniques based on gas-liquid chromatography were investigated and found to be unsatisfactory. By the use of reversed-phase high-performance liquid chromatography with gradient and ion-pairing techniques, methods were devised for the simultaneous analyses of a variety of metabolites. The method involves minimum sample work-up (acetonitrile precipitation) and allows easy and prompt analysis in biological media avoiding undue decomposition of unstable metabolites.     

Determination of ephedra alkaloids by high-performance liquid chromatography

Summary Two simple methods were developed for the simultaneous determination of six alkaloids (ephedrine, pseudoephedrine, norephedrine, norpseudoephedrine, methylephedrine and methyl-pseudoephedrine) inEphedrae Herba by high-performance liquid chromatography. The first method was carried out by using a Cosmosil 5C₁₈-MS column with a gradient solvent system consisting of a phosphate buffer and acetonitrile, and detection at 210 nm. The contents of alkaloids in non-pretreated ephedra herb extracts could be determined easily in 50 min. Alternatively, the alkaloids could be determined within 35 minutes by using a Cosmosil 5C₁₈-MS column with an isocratic solvent system of a sodium dodecyl sulfate-acetonitrile solution. The two methods are compared and discussed.     

Determination of sulfur anions by high-performance liquid chromatography

Sulfite, sulfate, sulfide and thiosulfate ions are separated by high-performance liquid chromatography under acidic conditions on commercial low-capacity silica-based and resin-based anion-exchange columns with potassium hydrogenphthalate as the eluent. The ions are detected by using indirect ultraviolet absorption or conductivity detectors. The effects of concentration, pH and flow rate of the eluent on the retention times of sulfur anions are reported. The resin-based column is preferable to the silica-based column for separations of sulfur anions.