Amidine als Zwischenprodukte bei Umamidierungsreaktionen. 9. Mitteilung über Umamidierungsreaktionen

Amidines as Intermediates in Transamidation Reactions By loss of water in the presence of p-toluenesulfonic acid/xylole N-aminoalkyllactames form bicyclic amidines. The corresponding N-alkylaminoalkyl-lactames' react to bicyclic amidinium salts or to transamidated products, ring-enlarged by the N-alkylamino residue, respectively (s. Scheme 1). The bicyclic amidines and amidinium salts are partially hydrolyzed by KOH/H₂O to lactames (s. Scheme 2). Which of the two possible isomeric lactames are formed is discussed.     

Multiresidue LC–MS/MS analysis of cephalosporins and quinolones in milk following ultrasound‐assisted matrix solid‐phase dispersive extraction combined with the quick,easy, cheap,effective, rugged,and safe methodology

A sensitive and selective confirmatory method for milk‐residue analysis of ten quinolones and eight cephalosporins by LC‐MS/MS has been developed herein. For the chromatographic separation of target analytes, a Perfectsil ODS‐2 (250 × 4 mm, 5 μm) analytical column was used and gradient elution was applied, using a mobile phase of 0.1% w/w TFA in water and 0.1% w/w TFA in ACN. Ultrasound‐assisted matrix solid‐phase dispersion procedure was applied for the extraction and clean‐up procedure of antimicrobials agents from milk matrix using a mixture of Bond Elut Plexa sorbent and QuEChERS. The method was validated meeting the European Legislation determining selectivity, linearity response, trueness, precision (repeatability and between‐day reproducibility), decision limit, detection capability, and ruggedness following the Youden approach. Recoveries of all antibiotics ranged from 81.7 to 117.9%, while RSD values were lower than 13.7%. Limits of quantification for all examined compounds ranged from 2.4 to 15.0 μg/kg, substantially lower than the maximum residue limits established by the European Union (30–100 μg/kg).     

Environmental Determination of Alkylphenol Polyethoxylate Refractory Residues Using Mass Spectrometric Techniques

Abstract

The use of methane chemical ionisation GC/MS gave satisfactory results when applied to environmental analysis of halogenated octylphenol polyethoxylates residues. In addition the selected ion monitoring GC/MS technique has been successfully applied for simulataneous qualitative and quantitative determination of some refractory metabolites of nonylphenol polyethoxylates in secondary sewage effluent and surface waters.     

Chemical ionization mass spectra of alkylphenol and linear alcohol polyethoxylates

The chemical ionization mass spectra of some tert-octylphenol ethoxylates and linear alcohol ethoxylates have been determined using methane and ammonia as reactant gases. Proton, [C₂H₅]⁺ and [C₃H₅]⁺ adducts were observed with attachment on the ring as well as on the oxyethylene chain for the tertiary octylphenol ethoxylates. Proton and [NH₄]⁺ addition reactions were also observed. Alkyl ion and olefin displacement reactions were also important fragmentations. Hydride abstraction and proton, [C₂H₅]⁺, [C₃H₅]⁺ and [NH₄]⁺ attachment were the most important reactions occurring for the linear alcohol ethoxylates.     

Umamidierungsreaktionen an cyclischen Amino-amid-Systemen. 3. Mitteilung über Umamidierungsreaktionen

Transamidation Reactions with Cyclic Amino-amides Lactames which are substituted at the nitrogen atom by a 3-aminopropyl residue are transformed under base catalysis to cyclic amino-amides enlarged by 4 ring atoms. The formed ring must be at minimum 12-membered. Scheme 2 illustrates this result: the 8-membered 7 is transamidated in 96% yield to the 12-membered ring 8 (in the presence of potassium 3-aminopropylamid in 1, 3-propanediamine), the 9-membered 10 to the 13-membered ring 11 (97%) and the 11-membered 14 to the 15-membered ring 15 . Furthermore, the 13-membered ring 27 (Scheme 5) is transformed to the 17-membered 28 . In the case of the 15-membered lactame 15 it is demonstrated that 14 is not formed back under the conditions of the transamidation. Large ring lactames which are substituted at the nitrogen atom by a 3-(alkylamino) propyl group lead under base catalysis to an equilibrium mixture, e.g. the 17-membered 26 is in equilibrium with the 21-membered 29 . This result is similar to the behavior of the corresponding open-chain amino-amides [2]. Because of transannular interactions, the 11-membered ring 2 is not stable: transamidation of the 7-membered 1 (Scheme 1) doesn't give the expected 2 , but its water elimination product 3 in small yield. The N-tosyl derivative of 2 , namely 20 , is synthesized by an independent route (Scheme 3). Detosylation of 20 yields the 7-membered 1 instead of 2 . Concerning the mechanism of this interesting reaction see Scheme 4.     

Optimization and application of high-resolution gas chromatography with ion trap tandem mass spectrometry to the determination of polychlorinated biphenyls in atmospheric aerosols

Optimization of the Finnigan GCQ ion trap mass spectrometry (ITMS) system and a clean-up procedure were carried out in order to apply high-resolution gas chromatography-tandem mass spectrometry for the analysis of polychlorinated biphenyls (PCBs) in aerosols. Six ITMS operating parameters, including isolation time, excitation voltage, excitation time, "q" value, ion source temperature and electron energy were adjusted in order to optimize the instrument analytical performance. The adjustment of all parameters substantially increased the sensitivity of ITMS in the MS-MS mode. Changes in isolation time did not particularly affect ITMS sensitivity while ion source temperature had the strongest influence. After optimization, a limit of detection of 600 fg/microl with S/N varying from 8 up to 91 was achieved. The application of the optimized ITMS parameters conjointly with the developed clean-up procedure resulted in method detection limits of 10-20 fg/m3 for the determination of PCBs, in the particulate and gas phase of the atmospheric aerosol of background areas in the Eastern Mediterranean and Sweden.     

Trace analysis of free and combined amino acids in atmospheric aerosols by gas chromatography–mass spectrometry

The analysis of amino acids by gas chromatography mass spectrometry (GC–MS) after their derivatization with N-(t-butyldimethylsilyl)-N-methyltrifluoroacetamide was investigated as an alternative approach for the determination of free (FAA) and combined amino acids (CAA) in aerosols. This technique showed excellent linearity with r² values ranging from 0.9029 to 0.9995 and instrumental limits of detection ranging from 0.3 to 46 pg for the different amino acids. The quality of water used for sample extraction was found to be of utmost importance for achieving low blank levels of FAA and CAA. The addition of isopropanol during the extraction of aerosols was also shown to minimize the coextraction of inorganic salts that interfered with the analysis of FAA, Moreover, the ascorbic acid was found to be the most effective reagent for preventing the oxidative destruction of CAA during the hydrolysis process. By the analysis of spiked aerosol samples, the average recoveries determined for FAA and CAA were higher than 60% and the associated relative standard deviation was lower than 10% for the majority of amino acids. The application of the adopted method in background aerosols of the eastern Mediterranean enabled the unambiguous identification and quantification of 20 amino acids. The total concentration of FAA and CAA in aerosols ranged from 13 to 34 ng m⁻³ and from 29 to 79 ng m⁻³, respectively. The GC–MS based method is proposed to overcome several analytical difficulties usually encountered with the conventional HPLC-fluoresence technique.