Study of fatty acid profiles in cancer cells grown in culture using gas chromatography--mass spectrometry

The determination of long-chain fatty acids in the phospholipid, triglyceride and free fatty acid fractions of HT29/219 colon cancer cells grown in a medium containing either foetal calf serum or horse serum, was carried out using gas chromatography - mass spectrometry. Several bonded-phase capillary columns were tested for the separation of the fatty acid methyl esters, and a 30-m poly(ethylene glycol) column was found to give optimum separation. The mass spectrometer was set to the multiple ion detection mode to increase the sensitivity of the recording of the characteristic ions, consisting of the molecular ion and the base peak. The phospholipid and triglyceride compositions of the cells were different when the cells were grown in media containing different sera. Differences were also found in the turnover of the acids in the different lipid fractions, the phospholipids being the most important, when the cells were grown in different media. The cellular metabolism and turnover of certain fatty acids differed from others in the same cell. These differences emphasise the importance of a precise knowledge of the lipid composition of the culture medium in in vitro studies of cancer cells.     

Analysis and kinetics of 2,4-dinitrophenol in tissues by capillary gas chromatography--mass spectrometry

Five groups of six ICR mice were orally dosed with 22.5 mg/kg 2,4-dinitrophenol. Groups were sacrificed at 1, 3, 6, 12, and 24 h post treatment, and serum, liver, and kidney tissues were collected for analysis of dinitrophenol content. Quantitation was performed via a capillary gas chromatography--mass spectrometry technique after liquid--liquid extraction of biological specimens spiked with a trideuterated dinitrophenol internal standard. Concentration versus time data for each tissue were subjected to pharmacokinetic analysis. Similar two-compartment open models were found to characterize most phases of the disposition of this compound. The kidney appears to maintain a more persistent low concentration of 2,4-dinitrophenol.     

Microdetermination of caffeine in blood by gas chromatography--mass spectrometry

A micromethod for the quantitative analysis of caffeine present in small quantities (100 microliter) of whole blood is described. It is based on the gas chromatographic--mass spectrometric analysis of chloroform extracts of biological samples. The method is relatively simple, rapid, specific and sensitive; as little as 20 ng of caffeine can be measured.     

Simple and unambiguous method for identifying urinary acylcarnitines using gas chromatography--mass spectrometry

Several inherited metabolic disorders, particularly the organic acidurias and acidemias, are often characterised by excretion of acylcarnitines, especially octanoylcarnitine, in the urine. Clinical investigation of such serious disorders ideally requires a rapid, simple and selective method for determining acylcarnitines in urine. Initial results are given here of a method that may approach this ideal. The procedure involves chemical derivatisation, in which the zwitterionic acylcarnitines are cyclised to volatile lactones, and analysis by gas chromatography and gas chromatography--mass spectrometry. Preparation of urine samples by ion-exchange purification and an illustrative application of the proposed method to a clinical sample are also outlined.     

Quantitation of a metal deactivator additive by derivatization and gas chromatography--mass spectrometry

The quantitative analysis of phenolic and amine-containing petroleum additives can be challenging. One such compound-N,N'-disalicylidene-1,2-propanediamine, a common metal deactivator additive (MDA)--is thought to inhibit fuel oxidation catalyzed by metals both in the fuel and on surfaces. The ability to measure the concentration of MDA in storage stability tests, thermal-stressing studies, and field samples is important. Quantitating low concentrations of MDA can be difficult because of surface adsorptivity due to the phenol and amine functional groups. This paper describes the shortcomings of direct-injection gas chromatography-mass spectrometry to quantitate MDA as well as a solution to the analytical problem using the common silylation agent BSA to derivatize the MDA. Results demonstrate that the silylation technique is suitable for the determination of MDA concentrations in aviation fuel samples and suggests that the MDA may be readily determined in other petroleum products with a lower detection limit for MDA of 0.5 mg/L. Measurements conducted in heated batch reactors indicate that MDA concentration is reduced as hydrocarbon fuels are stressed. In addition, only free or available MDA is measured by this technique, not MDA that is complexed with metals.     

气相色谱-串联质谱法测定土壤中的邻苯二甲酸酯

建立了土壤中6种邻苯二甲酸酯的气相色谱-串联质谱(GC-MS/MS)分析方法。土壤样品用超声提取,以二氯甲烷-丙酮(1:1, v/v)混合溶液为提取溶剂,提取液经Florisil小柱净化后,经HP-5MS色谱柱(30 m×0.25 mm×0.25 μm)分离,利用MS/MS的多反应监测(MRM)模式进行定性和定量。结果表明本方法可对样品中的邻苯二甲酸酯进行分析,在10～1000 μg/L质量浓度范围内,线性关系良好,相关系数为0.9973～0.9976;6种邻苯二甲酸酯的相对标准偏差(RSD)不大于14.3%, 2 μg/kg和10 μg/kg两个加标水平的回收率为72.9%～106.2%; 6种目标化合物的检出限为0.1～0.5 μg/kg。该方法快速准确、背景干扰较少、分析灵敏度较高,适用于土壤样品中邻苯二甲酸酯的分析。     

Syntheses of new C2-symmetric,optically active 1,2-diols bearing tertiary alkyl groups

New C₂-symmetric chiral 1,2-diols, 1,2-bis(1-adamantyl)-1,2-ethanediol and 3,3,6,6-tetramethyl-1,2-cyclohexanediol, were synthesized by the use of a new resolution method.     

Rapid identification of fatty acid methyl esters using a multidimensional gas chromatography-mass spectrometry database

A multidimensional approach for the identification of fatty acid methyl esters (FAME) based on GC/MS analysis is described. Mass spectra and retention data of more than 130 FAME from various sources (chain lengths in the range from 4 to 24 carbon atoms) were collected in a database. Hints for the interpretation of FAME mass spectra are given and relevant diagnostic marker ions are deduced indicating specific groups of fatty acids. To verify the identity of single species and to ensure an optimized chromatographic resolution, the database was compiled with retention data libraries acquired on columns of different polarity (HP-5, DB-23, and HP-88). For a combined use of mass spectra and retention data standardized methods of measurement for each of these columns are required. Such master methods were developed and always applied under the conditions of retention time locking (RTL) which allowed an excellent reproducibility and comparability of absolute retention times. Moreover, as a relative retention index system, equivalent chain lengths (ECL) of FAME were determined by linear interpolation. To compare and to predict ECL values by means of structural features, fractional chain lengths (FCL) were calculated and fitted as well. As shown in an example, the use of retention data and mass spectral information together in a database search leads to an improved and reliable identification of FAME (including positional and geometrical isomers) without further derivatizations.     

Simple synthesis of esters of methylenecyclopropanecarboxylic acid from alkyl diazoacetates and allene gas

Conclusions The thermal and thermocatalytic reaction of alkyl diazoacetates with allene gas at 125–280° in a reactor of the flow type proceeds to give the esters of methylenecyclopropanecarboxylic acid in up to 50% yield, whose saponification with aqueous alcoholic alkali solution gives 2-methylenecyclopropanecarboxylic acid in up to 80% yield.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 10, pp. 2405–2408, October, 1983.     

Enantiomeric excess of 1,2-diols by formation of cyclic boronates: an improved method

A reliable method for determining the enantiomeric composition of 1,2-diols by the formation of diastereomeric cyclic esters with boronic acid is described. Starting from a previously reported structure of boronic chiral derivatizing agent (CDA), seven structurally related racemic CDAs were synthesized and their discriminating ability towards diols measured. The most promising amongst these was synthesized in its enantiomerically pure form according to Matteson’s protocol for the stereoselective homologation of pinanediol boronates; this CDA quantitatively and rapidly reacts with 1,2-diols in very mild conditions affording a couple of diastereoisomers, whose composition can be determined via ¹H NMR analysis. In particular, an attractive feature is that the resonance used for the analysis originated from the CDA as a couple of baseline-separated singlets (Δδ up to 0.3 ppm) is useful for integration.     

Identification of low chlorinated biphenyls in human milk by gas chromatography--mass spectrometry.

Trichlorobiphenyl and tetrachlorobiphenyls in human milk were analysed by gas chromatography--mass spectrometry and mass fragmentography using silicone OV-1 and Apiezon L grease as stationary phases. Low-chlorinated biphenyls had been considered to be excreted rapidly from the body, but in this work quantities of tri- and tetrachlorobiphenyls amounting to approximately 30% of the total of polychlorinated biphenyls (PCBs) accumulated in the milk were identified. This result is important in relation to the quantification of PCBs and in studies of the mechanism of biological degradation.     

气相色谱-串联质谱法测定婴儿奶粉中16种邻苯二甲酸酯类化合物

建立了气相色谱-串联质谱（GC-MS/MS）测定复杂基体婴儿奶粉中16种邻苯二甲酸酯类塑化剂的分析方法。奶粉样品以水溶解均质,乙腈提取,乙二胺-N-丙基硅烷（PSA）类型玻璃固相萃取柱净化,DB-5 MS UI气相色谱柱（30 m×0.25 mm×0.25 μm）分离,同位素稀释质谱法（IDMS）定量。比较了氧化铝/PSA和PSA两种固相萃取柱在不同洗脱条件下萃取16种塑化剂的回收率。最终选择PSA固相萃取柱,以正己烷-丙酮（60：40,v/v）作为洗脱溶剂,实现奶粉基体中16种塑化剂的净化。采用基质匹配同位素内标法定量,16种塑化剂在0.01~2.0 mg/kg范围内线性良好,线性相关系数（R²）大于0.9996,检出限和定量限分别是0.15~2.50 μg/kg和0.50~8.33 μg/kg,加标回收率为96.1%~104.0%,相对标准偏差（RSD）小于3.3%（n=5）,该方法灵敏度好、精密度高,适用于婴儿奶粉基体中16种塑化剂的痕量分析。     

Fluoride anion binding by cyclic boronic esters: influence of backbone chelate on receptor integrity

A systematic investigation of fluoride anion binding properties as a function of chelate backbone has been carried out for ferrocene functionalised boronic esters of the types FcB(OR)2 and fc[B(OR)2]2 [Fc = ferrocenyl = (eta5-C5H5)Fe(eta5-C5H4); fc = ferrocendiyl = Fe(eta5-C5H4)2]. Cyclic boronic esters containing a saturated five- or six-membered chelate ring are readily synthesized from ferrocene, and selectively bind fluoride via Lewis acid/base chemistry in chloroform solution. The resulting complexes are characterized by relatively weak fluoride binding (e.g.K = 35.8 +/- 9.8 M(-1) for FcBO2C2H2Ph2-S,S), and by cathodic shifts in the ferrocene oxidation potential that form the basis for electrochemical or colorimetric fluoride detection. The fluoride selectivity of these systems is attributed to relatively weak Lewis acidity, resulting in weak F- binding, and essentially no binding of potentially competitive anions. By contrast, more elaborate Lewis acid frameworks based on calix[4]arene (calixH4), such as (FcB)2calix or fcB2calix, do not survive intact exposure to standard fluoride sources (e.g. [nBu4N]F.xH2O solutions in chloroform or acetonitrile). Instead B-O bond cleavage occurs yielding the parent calixarene; the differences between alkoxo- and aryloxo-functionalised derivatives can be rationalised, at least in part, by consideration of the differences in electron donating capabilities of RO- (R = alkyl, aryl).     

Identification of the nitrosation reaction products of alkyl esters of 1,2-benzisoxazole-3-acetic acid by chemical and crystallographic methods

The reaction between methyl or ethyl esters of 1, 2-benzisoxazole-3-acetic acid and iso-amyl nitrite is reported. The main product is identified as 4-(2′-hydroxyphenyl)furazan-3-carboxylic acid ( 4 ) by chemical and X-ray crystal structure analyses. The synthesis of esters of E- and Z-α-(hydroxyimino)-1, 2-benzisoxazole-3-acetic acid is also reported.     

Synthesis of non-proteinogenic phenylalanine analogues by Suzuki cross-coupling of a serine-derived alkyl boronic acid

Protected serine-derived boronic acids have been prepared as β-anionic alanine equivalents, and undergo efficient Suzuki cross-coupling with a variety of aryl halides to give, after elaboration, non-proteinogenic phenylalanine analogues.     

Synthesis of alkyl-H-phosphinic acid alkyl esters from red phosphorus and alkyl bromides

Alkyl-H-phosphinic acid alkyl esters are synthesized in 65–71% yield via chemoselective reaction of alkyl bromides with available alkyl-H-phosphinic acids (60–65 °C, Et3N). The latter are prepared, in turn, by direct phosphorylation of alkyl bromides with red phosphorus under phase-transfer conditions.