Novel mass spectral fragmentation of heptafluorobutyryl derivatives of acyl analogues of platelet-activating factor

Direct derivatization of the acyl analogue of platelet-activating factor (acyl-PAF) with heptafluorobutyric anhydride results in replacement of the phosphocholine moiety with a heptafluorobutyryl (HFB) group. Electron capture (EC) mass spectrometric analysis of this compound that makes use of negative ion detection along with subsequent accurate mass measurement and tandem mass spectrometry studies revealed that in addition to expected fragmentation due to losses of elements of HF, ketene, and/or acetic acid, there is a rearrangement reaction between the HFB group and the substituent on carbon-2 of the glycerol backbone. For 2-acetyl isomers, this fragmentation yields a characteristic ion at m/z 237; for 1-acetyl isomers, the analogous ion is observed at [M-135]⁻, along with a corresponding carboxylate anion. The use of the HFB derivative is invaluable for analysis of PAF homologues and analogues because it provides detailed structural information in combination with the high sensitivity of a gas chromatography combined with EC-mass spectrometry assay.     

Mass spectrometric analysis of platelet-activating factor after isolation by solid-phase extraction and direct derivatization with pentafluorobenzoic anhydride

Platelet-activating factor is the term used to denote a class of extremely potent lipid mediators that consist predominantly of 1-O-alkyl- and 1-O-acyl-2-acetyl-sn-glycero-3-phosphocholines. A method has been devised for rapid isolation of these acetylated phospholipids by solid-phase extraction prior to direct derivatization with pentafluorobenzoic anhydride and analysis by gas chromatography (GC)/electron-capture mass spectrometry. Recovery through the entire method (lipid isolation, derivatization, and purification) typically ranged from 70% to 85%. Using the direct derivatization procedure described here, the practical limit of detection for each of the standard alkyl- and acyl-platelet-activating factor homologs was 1 fmol injected into the GC. Results from the application of the method to the analysis of alkyl and acyl homologs of platelet-activating factor isolated from stimulated human umbilical vein endothelial cells are presented, exhibiting excellent accuracy and precision for a wide range of tissue levels of this class of potent autacoids.     

Gas chromatographic-mass spectrometric profiling with negative-ion chemical ionization detection of prostaglandins and their 15-keto and 15-keto-13,14-dihydro catabolites in rat blood

A method was set up in which the primary prostaglandins (PGF2 alpha, PGD2, PGE2, thromboxane B2, 6-keto-PGF1 alpha and 6-keto-PGE1) and their catabolites (15-keto and 15-keto-13,14-dihydro) could be analyzed in the same sample at the same time. The method makes use of long capillary columns (60 m) to resolve the complex mixture during gas chromatography and mass fragmentography to provide the specificity of detection of these products. Selectivity and sensitivity is provided through use of appropriate derivatives (pentafluorobenzyl esters) which allow detection by negative-ion chemical ionization in which high-abundance fragments in the high end of the mass spectrum (M-pentafluorobenzyl) are observed. A purification procedure of whole blood is described involving diethyl ether extraction, C18 Sep-Pak chromatography, derivatization into the pentafluorobenzyl-O-methyloxime, C18 Sep-Pak and silicic acid chromatography followed by final derivatization into trimethylsilyl ethers for gas chromatographic-mass spectrometric analysis. Recovery of added [3H]PGF2 alpha was 73.8 +/- 2.2% (n = 10). Sample workup and analysis takes ten days for six samples. The method is sufficiently sensitive for the profiling of a 10-ml sample of whole blood (limit approximately 1 pg/ml; 1-pg injection on column).     

Structure and ambiphilic reactivity of indolizines. 2. 8(6)-Acetyl- and cyanoindolizines

Quaternization of 2-methyl-3(5)-acetyl and cyanopyridines with -bromoketones followed by cyclocondensation has given a number of 8(6)-acetyl- and cyanoindolizines.For Part 1, see [1].Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 2, pp. 209–213, February, 1987.     

Determination of disopyramide and its mono-N-dealkylated metabolite in blood serum and urine.

A rapid, precise and accurate assay for disopyramide and mono-N-dealkylated disopyramide concentrations in blood serum and urine is described. The method involves extraction of the drugs from a basic aqueous medium into chloroform, derivatization of the metabolite, purification of the extract and gas chromatographic analysis using an OV-17 liquid phase and flame ionization detection. Unique characteristics of the procedure, direct derivatization in the organic phase and the use of Florisil to separate the drugs from interfering materials, should be applicable to the analysis of other basic drugs in biological specimens.     

Ring transformation of 5-acylpyrimidines into 4-acylpyrazoles with hydrazine and phenylhydrazine in acidic medium

5-Benzoyl-4-methylpyrimidines 4a,b and 5-acetyl-4-phenylpyrimidines 5a,b reacted with hydrazines in alcoholic acidic medium to give respectively 4-acetyl-3-phenylpyrazoles 7, 9 and 10 and 4-benzoyl-3-methylpyrazoles 6, 8 and 11 . In the reaction with phenylhydrazine, 5-benzoyl-4-methyl-2-methylthiopyrimidine ( 4a ) led exclusively to 4-acetyl-1,3-diphenylpyrazole ( 10 ) as 5-acetyl4-phenyl-2-methylthiopyrimidine ( 5a ) led to 4-benzoyl-3-methyl-1-phenylpyrazole ( 11 ) via the initial formation of phenylhydrazones of pyrimidines 4a and 5a . However, 5-benzoyl-4-methyl-2-phenylpyrimidine ( 4b ) and 5-acetyl-2,4-diphenylpyrimidine ( 5b ) reacted with phenylhydrazine to afford, each of them, a mixture of two isomeric pyrazoles. The mechanism of these ring contraction reactions is discussed.     

Determination of dioxopiperazine metabolites of quinapril in biological fluids by gas chromatography-mass spectrometry.

The dioxopiperazine metabolites of quinapril in plasma and urine were extracted with hexane-dichloroethane (1:1) under acidic conditions. Following derivatization with pentafluorobenzyl bromide and purification of the desired reaction products using a column packed with silica gel, the metabolites were analysed separately by capillary column gas chromatography-electron-impact mass spectrometry with selected-ion monitoring. The limits of quantitation for the metabolites were 0.2 ng/ml in plasma and 1 ng/ml in urine. The limits of detection were 0.1 ng/ml in plasma and 0.5 ng/ml in urine, at a single-to-noise ratio of greater than 3 and greater than 5, respectively. The proposed method is applicable to pharmacokinetic studies.     

Isolation of doxycycline, 6-epidoxycycline and 2-acetyl-2- decarboxamidometacycline from commercial metacycline by preparative column liquid chromatography on silica gel.

Isolation of doxycycline, 6-epidoxycycline and 2-acetyl-2-decaboxamidometacycline from commercial metacycline was achieved by preparative column liquid chromatography on silica gel, previously impregnated with edetate (EDTA). Careful control of the pH of EDTA allowed fine tuning of the separation. The mobile phases were composed of dichloromethane, methanol and .1 mM EDTA at pH 9.0 or 6.0. Structures were confirmed with nuclear magnetic resonance spectroscopy. The presence of doxycycline and its 6-epimer in commercial metacycline has not previously been described. The presence of the 2-acetyl derivative was not surprising since analogous 2-acetyl derivatives have been identified in other tetracyclines.     

Quantitative gas chromatography using a new automated derivatizer

In the gas chromatographic analysis of complex biological samples, the most time-consuming and error-prone steps are the pretreatment required for isolation and purification of the compounds of interest and, for most analytes, the derivatization to chemically and thermally stable compounds with high volatility. These wet-chemical steps are usually carried out manually, and for routine analysis of large numbers of samples they are often rate-limiting. A dedicated automated derivatizer has been constructed, the employment of which significantly reduces the time required for manual labor and increases the reproducibility of derivatization and hence the accuracy of analysis.     

气相色谱-质谱技术分析香稻特征化合物2-乙酰基吡咯啉

建立了气相色谱-质谱技术(GC-MS)分析香稻特征化合物2-乙酰基吡咯啉的方法。在香稻中加入内标物2,4,6-三甲基吡啶,密闭,经无水乙醇-二氯甲烷(体积比为1:1)在80 ℃水浴中提取3 h。考察了温度和时间对2-乙酰基吡咯啉提取的影响。提取液经毛细管气相色谱柱HP-5MS(30 m×0.25 mm×0.25 μm)分离,全扫描监测模式GC-MS测定。以内标物计,方法的平均回收率为82.57%,相对标准偏差为5.09%,最低检出限为0.01 mg/kg。将该方法应用于11份香稻育种材料中2-乙酰基吡咯啉的测定,结果表明,清香米、泰香R207、Texmati、桂香丝糯和中健2号等5个品种中含有2-乙酰基吡咯啉,含量分别为0.097、0.098、0.699、0.045和0.047 mg/kg。该方法样品处理简单、快速、灵敏、样本和试剂消耗少,尤其适合于通过测定2-乙酰基吡咯啉含量进行香稻育种前的大批量品种筛选。     

Determination of low-molecular-weight carboxylic acids in aqueous samples by gas chromatography and nitrogen-selective detection of 2-nitrophenylhydrazides

A gas chromatographic method was developed for the determination of low-molecular-weight carboxylic acids in aqueous samples based on a derivatization procedure compatible with aqueous solutions. The technique uses nitrogen-selective detection with a thermionic-specific detector after derivatization of carboxylic acids as 2- nitrophenylhydrazides. The hydrazides were extracted with ethyl acetate prior to injection into the gas chromatograph. The derivatives appear to be stable in ethyl acetate at 0–5° C for long periods and, therefore, can be stored for analysis at a later date. The detection limits of different short-chain acids are in the range 0.8–1.4 pmol per injected sample. The relative standard deviation is less than 10% at the 1 μM level. Examples of the use of the method are given for the determination of carboxylic acids in anoxic marine sediment pore waters, coastal sea water and Black Sea water samples.     

Determination of residual solvents in isobutylboronic acid: Masking derivatization improves stability of GC column

Masking derivatization was introduced for the determination of residual solvents in samples containing a volatile reactive matrix component(s). Isobutylboronic acid, used in the last step of Bortezomib synthesis, represents a compound passing to the gas phase and deteriorating a chromatographic column during a headspace analysis. The masking derivatization with 1,8‐diaminonaphthalene allowed a simple and straightforward conversion of isobutylboronic acid to a stable nonvolatile derivative and thus prevented gas chromatography column deterioration. The method was successfully validated according to the guidelines of International Committee for Harmonization (Q3C (R6) Guideline for Residual Solvents) and international pharmacopoeias (Ph. Eur., USP) and approved by Teva Czech Industries for routine application.     

气相色谱-质谱方法检测磺酸类阴离子表面活性剂

使用K I/DMF/(CF3CO)2O还原衍生方法,结合气相色谱-质谱(GC/MS)联用技术对磺酸类化合物进行了结构鉴定和成分分析。实验结果表明,这种新的还原衍生方法不仅方便快速、条件易控,而且产物稳定,具有良好的气相色谱-质谱行为,可以很好地解决磺酸类阴离子表面活性剂有效成分分析鉴定的难题。     

N-Acetyl-5-arylidenetetramic acids: synthesis,X-ray structure elucidation and application to the preparation of zinc(II) and copper(II) complexes

A new route to N-acetyl-3-acyl-5-arylidenetetramic acids was developed and applied to the synthesis of a small library of compounds with diversity at carbon 3 of the heterocyclic ring. The 3-acetyl derivative was used as ligand for complexation with zinc(II) and copper(II) acetates. Both the ligand and the zinc complex were studied by X-ray single crystal structure analysis, the zinc complex forms ribbons by H-bonding from the ethanol to a neighbouring molecule.     

Improved derivatization technique for gas chromatography-mass spectrometry determination of 3-chloro-4-(dichloromethyl)-5-hydroxy-2(5H)-furanone in drinking water

The quantification of 3-chloro-4-(dichloromethyl)-5-hydroxy-2(5H)-furanone (Mutagen X or MX) in drinking water is difficult due to the low concentration of MX in drinking water, its high sensitivity to pH change, and matrix effects that interfere with the derivatization and analysis. Typically, the quantification of MX involves derivatization by methylation. We present a one-step derivatization procedure for MX using N-methyl-bis-trifluoroacetamide (MBTFA) and analysis by ion trap GC/MS/MS. The new method resulted in a significant reduction in analysis time, and improved detection limits. The abundant and selective ions in the mass spectrum of the trifluoroacylated MX (trifluoroacetic acid-4-chloro-3-dichloromethyl-5-oxo-2-hydro-furan-2-yl ester) allowed for a clear identification and quantification of the compound, with a method detection limit of 7.7 ng L⁻¹, and a limit of quantitation of 24.4 ng L⁻¹. The trifluoroacylated MX was shown to be stable for 30 days in an excess of the derivatization reagent. The new method was applied for the determination of MX in several drinking water samples, with a concentration range from not-detected to 517 ng L⁻¹; these values are comparable to those obtained in previous studies. The development of this new simplified analytical method for MX is an important step forward in the field of disinfection by-product (DBP) research, particularly in light of the recent scientific recognition of halogenated furanones as emerging drinking water contaminants. Increased analytical ability may well be a decisive factor in the monitoring of these disinfection by-products.     

The synthesis of some purine nucleosides from 4,6-di-O-acetyl-3-deoxy-3-(ethoxycarbonylamino)-D-glucal

The acid catalyzed reaction of 4,6-di-O-acetyl-3-deoxy-3-(ethoxycarbonylamino)-D-glucal and 6-chloropurine in nitrometliane solution gave 6-ehloro-9-(4′,6′-di-O-acetyl-2′,3′-dideoxy-3′-ethoxy-carbonylamino-α- and β-D-arafemohexopyranosyl)purine. These were converted to the corresponding deblocked 6-dimetliylaminopurine nucleosides by treatment with ethanolic dimethylamine; acetylation of these gave the respective 4′,6′-di-O-acetyl derivatives. The anomeric assignments for the nucleosides were based on their nmr spectral data.     

Glass capillary gas chromatography-mass spectrometry at high temperatures. direct analysis of free base porphyrins and metal porphyrin complexes extracted from the serpiano oil shale

This contribution describes GC/MS analysis of natural petroporphyrin extracts containing alkylporphyrins either as vanadyl complexes or as demetalated free bases. The combination of high temperature glass capillary gas chromatography with mass spectrometry allows, for the first time, direct determination of electron impact mass spectra of separated alkylporphyrins, making additional purification and derivatization unnecessary. The separation is carried out on glass capillary columns coated with the high temperature-stable medium polar, OH-terminated, polysiloxane phases PS 086 and OV-225-OH. The paper gives detailed working directions for the preparation of the high temperature GC/MS-interface, and of the high temperature stable OV-225-OH columns (max. working temperature 390°C).     

Analysis of heterocyclic aromatic amines in foods by gas chromatography-mass spectrometry as their tert.-butyldimethylsilyl derivatives

A derivatization method for the analysis of 12 heterocyclic aromatic amines (HAs) in food, by gas chromatography-electron impact mass spectrometry, was developed. The amines are derivatized in a one-step reaction with N-methyl-N-(tert.-butyldimethylsilyl)trifluoroacetamide. The derivatives are characterized by easy-to-interpret mass spectra due to the prominent ion [M-57]+ by loss of a tert.-butyldimethylsilyl group, allowing quantification in the selected-ion monitoring mode at the picogram level. The effect of temperature, time, and reagents on the formation of the derivatives was monitored in detail. Quality parameters were evaluated in the optimum working conditions. This derivatization method is not applicable to the pyridoimidazoles Glu-P-1 and Glu-P-2 and to the beta-carboline harman due to incompletely derivatization. The instability of the imidazolquinoline and imidazoquinoxaline derivatives, requiring their injection on the same working day, is a further drawback. This simple, rapid and accurate derivatization procedure is suitable for routine analysis, as illustrated by the analysis of some common foods.     

Investigation of combwax of honeybees with high-temperature gas chromatography and high-temperature gas chromatography-chemical ionization mass spectrometry. I. High-temperature gas chromatography.

The combwaxes of the honeybee species Apis mellifera, Apis cerana, Apis dorsata, Apis laboriosa, Apis florea and Apis andreniformis have been examined by high-temperature gas chromatography. Combwax consists of a complex mixture of homologous neutral lipids. These compounds containing up to 64 carbons were chromatographed intact on a 10 m x 0.2 mm high-temperature stable SOP-50-PFD (50%-diphenyl/50%-1H,1H,2H,2H-perfluorodecylmethylpolysiloxane)-co ated Duran glass capillary column. The use of this stationary phase results in lower retention values and, at last, in lower thermal stress of the analytes. In order to minimize the discrimination effect due to adsorption and/or degradation, a two-step derivatization was performed resulting in the formation of tert.-butyldimethylsilyl esters of the long chain fatty acids and trimethylsilyl ethers of complex hydroxyesters, respectively. The derivatization procedure was optimized using a modification of the extended Donike test. In addition this test allows the quantification of the thermal stability of the derivatives performed. The derivatization procedure was applied for combwax analysis. More than 80 compounds were separated and their peak areas semiquantitatively exploited.     

HPLC determination of acetaminophen in saliva based on precolumn fluorescence derivatization with 12-(3,5-dichloro-2,4,6-triazinyl)benzo[d]benzo[1',2'-6,5]isoindolo[1,2-b][1,3]thiazolidine.

A high-performance liquid-chromatographic method for the determination of acetaminophen in saliva has been developed. This method is based on the precolumn derivatization of acetaminophen with 12-(3,5-dichloro-2,4,6-triazinyl)benzo[d]benzo[1',2'-6,5]isoindolo[1,2-b][1,3]thiazolidine, a new fluorescence derivatization reagent for phenolic compounds. The resulting derivative of acetaminophen is separated by isocratic elution on a reversed-phase column, and is fluorometrically detected at an emission wavelength of 560 nm with an excitation wavelength of 540 nm. The detection limit (signal-to-noise ratio = 3) was 0.1 microg/mL in saliva. The proposed method permits a highly sensitive and simple determination of acetaminophen in a small amount of saliva without any sample purification.