A Salting-out Liquid-Liquid extraction (SALLE) for the analysis of caprolactam and 2,4-di-tert butyl phenol in water and food simulants. Study of the salinity effect to specific migration from food contact materials.

Caprolactam and 2,4-di-tert-butyl phenol (2,4-DTBP) are substances typically found in some food contact materials (FCMs). They are known to often migrate into food, and are difficult to analyse in liquid food simulants using GC. In this work a simple salting-out Liquid-Liquid Extraction (SALLE) for the analysis of both substances in water and the official food simulant A (10 % v/v ethanol, Regulation (EU) No. 10/2011) is presented. The method, which included analytical determination by GC-MS, was optimized and validated to ensure sufficient analytical quality. The method's LOQs allowed the proper quantification of caprolactam at its EU legislative limit (15 mg kg-1). For 2,4-DTBP the method also revealed good sensitivity, although no official limits have been established yet. Linear regression coefficients (R2) were in all cases higher than 0.999, and recoveries ranged from 87 % and 95% for caprolactam and 2,4-DTBP, respectively. Precision was also acceptable, with the RSDs (%) below 12 %. The method proved to be adequate to be used for routine analysis. The presence of salt during migration of caprolactam and 2,4-DTBP was also investigated in this work. Polyamide/polyethylene FCM multilayer films have been tested with water and simulant A, containing different amounts of NaCl (up to 15 % m/v), and applying different migration conditions (temperature and time). The results indicated that salinity plays an important effect on the migration of caprolactam, with the presence of salt reducing its migration in case of water and increasing it in case of simulant A. These preliminary results seem to indicate that migration testing should consider not only the well-known fatty content of a food, but also its salinity content, as it may end up affecting drastically the migration of polar substances.

Antibacterial and antifungal screening of natural products sourced from Australian fungi and characterisation of pestalactams D-F.

Eighteen natural products sourced from Australian micro- or macro-fungi were screened for antibacterial and antifungal activity. This focused library was comprised of caprolactams, polyamines, quinones, and polyketides, with additional large-scale isolation studies undertaken in order to resupply previously identified compounds. Chemical investigations of the re-fermented culture from the endophytic fungus Pestalotiopsis sp. yielded three caprolactam analogues, pestalactams D-F, along with larger quantities of the known metabolite pestalactam A, which was methylated using diazomethane to yield 4-O-methylpestalactam A. The chemical structures of the previously undescribed fungal metabolites were determined by analysis of 1D/2D NMR and MS data. The structure of 4-O-methylpestalactam A was confirmed following single crystal X-ray diffraction analysis. The antibacterial and antifungal activity of all compounds was assessed, which identified three compounds, (1S,3R)-austrocortirubin, (1S,3S)-austrocortirubin, and 1-deoxyaustrocortirubin with mild activity (100 µM) against Gram-positive isolates and one compound, 2-hydroxy-6-methyl-8-methoxy-9-oxo-9H-xanthene-1-carboxylic acid, with activity against Cryptococcus neoformans and Cryptococcus gattii at 50 µM.

Determination of caprolactam and residual vinyl caprolactam monomer in soluplus by mixed mode gel permeation chromatography.

Soluplus, a graft copolymer of polyethylene glycol, vinyl caprolactam and vinyl acetate, is designed to solubilize poorly soluble active pharmaceutical ingredients. A straightforward aqueous gel permeation chromatography method that exploits both size exclusion and adsorption modes of separation was used to separate and quantify the related residual vinyl caprolactam monomer and caprolactam impurity present in Soluplus. This methodology offers a single step analysis of caprolactam and the residual vinyl caprolacatam monomer, yielding similar results to reversed-phase chromatography measurements, which are time-consuming and may involve multi-step sample preparation. The results of this study demonstrate that gel permeation chromatography provides a viable option to traditional reversed-phase chromatography in the quantitative analysis of residual caprolactam and vinyl caprolactam monomers and can be extended to other monomer-polymeric systems.

Pestalactams A-C: novel caprolactams from the endophytic fungus Pestalotiopsis sp.

Chemical investigations of a fermentation culture from the endophytic fungus Pestalotiopsis sp. yielded three novel caprolactams, pestalactams A-C (). The structures of were determined by analysis of 1D and 2D-NMR, UV, IR, and MS data. The structure of pestalactam A was confirmed following single crystal X-ray diffraction analysis. Pestalactams A-C are the first C-7 alkylated caprolactam natural products to be reported. Pestalactams A () and B () were tested against two different strains of the malaria parasite Plasmodium falciparum (3D7 and Dd2), and the mammalian cell lines, MCF-7 and NFF, and showed modest in vitro activity in all assays.

Calpinactam, a new anti-mycobacterial agent, produced by Mortierella alpina FKI-4905.

Calpinactam, a new anti-mycobacterial agent, was isolated from the culture broth of a fungal strain Mortierella alpina FKI-4905 by solvent extraction, octadecyl silane column chromatography and preparative HPLC. Calpinactam was active only against Mycobacteria among various microorganisms, including Gram-positive and Gram-negative bacteria, fungi and yeasts. Calpinactam inhibited the growth of Mycobacterium smegmatis and Mycobacterium tuberculosis with MIC values of 0.78 and 12.5 microg ml(-1), respectively.

Preparation of polysulfone microcapsules containing 1-octanol for the recovery of caprolactam.

Polysulphone (PSF) microcapsules containing 1-octanol were prepared with solvent extraction method for the recovery of caprolactam. One-step and two-step processes were, respectively, applied to prepare microcapsules. In order to get high extractant loading, a loading method with the assistance of ultrasound has been developed. With the two-step preparation process the extractant loss can be avoided. A very high extractant loading ratio of 5.96 g g(-1) and the maximum uptake to caprolactam of 65.6 mg g(-1) were achieved. Under the action of ultrasound the extractant loading efficiency is greatly intensified. With the one-step process 1-octanol loading ratio is highly limited. Only 1.74 g g(-1) loading ratio and 29.9 mg g(-1) uptake to caprolactam were realized. Meanwhile the extractant loss in the one-step process is serious. Considering extraction capacity and extractant loss in the preparation process, it is suggested that PSF microcapsules containing 1-octanol should be prepared with the two-step process. To fasten mass transfer rate, microcapsules with relatively smaller size are desired.

Molecular mechanism of dielectrically controlled optical resolution (DCR).

We have recently found the first example of dielectrically controlled optical resolution (DCR). By adjusting the dielectric constant of the solvent used in the resolution process, each optical isomer of (R,S)-alpha-amino-epsilon-caprolactam can be selectively obtained using N-tosyl-(S)-phenylalanine as a chiral selector. The molecular mechanism of DCR has been investigated by comparing the molecular and crystal structures of the optical selector, its target substrate and their diastereomeric salts. Strong hydrophobic interactions between the phenyl rings of the optical selector govern the molecular aggregation of the selectors and form a hydrophilic layer in which molecular recognition takes place. The recognition site in the hydrophilic layer can inherently identify both of the isomers. The dielectric constant of the solvent used in the discrimination process controls the intermolecular interaction which determines the isomer to be selected. The molecular mechanism of DCR disclosed in this study strongly suggests that DCR is not a specific but a general phenomenon. This method can be applicable to a large variety of optical resolution processes.

Endgroup-based separation and quantitation of polyamide-6,6 by means of critical chromatography.

Polyamide-6,6 is a polycondensation product from the two monomers adipic acid and 1,6-hexamethylenediamine. Depending on the reacted amount of these monomers, different ratios of amine and carboxylic acid endgroups can be formed. Besides linear chains, cyclic polyamides will also be formed. Using critical chromatography, polyamide-6,6 can be separated independently of molar mass. Retention is based solely on endgroup functionality. It is demonstrated that high-molecular-mass polyamide-6,6 (Mw approximately 20,000-30,000) can be separated using this approach. The separation was optimized by using different parameters, such as percentage modifier, temperature and pressure. The concentration of phosphoric acid was used for selective retention of the different endgroup functionalities. Using this property, a new method called critical gradient chromatography was performed where the mobile phase changes from a weak to a strong solvent with respect to the endgroup functionality, while retaining the critical conditions of the backbone unit. Quantification using UV detection is discussed.

Headspace solid-phase microextraction--a tool for new insights into the long-term thermo-oxidation mechanism of polyamide 6.6.

Low-molecular-mass products formed during thermo-oxidation of polyamide 6.6 at 100 degrees C were extracted by headspace solid-phase microextraction and identified by GC-MS. A total of 18 degradation products of polyamide 6.6 were identified. In addition some low-molecular-mass products originating from the lubricants were detected. The identified degradation products were categorized into four groups where compounds within each group contain the same structural feature. In groups A, B and C several new thermo-oxidation products of polyamide 6.6 were identified including cyclic imides, pyridines and structural fragments from the original polyamide chain. 1-Pentyl-2,5-pyrrolidinedione (pentylsuccinimide) showed the largest increase in abundance during oxidation. The cyclopentanones in group D were already present in the un-aged material. Their amounts decreased during ageing and they are thus not formed during thermo-oxidation of polyamide 6.6 at 100 degrees C. The identified thermo-oxidation products can be formed as a result of extensive oxidation of the hexamethylenediamine unit in the polyamide backbone. The degradation products pattern shows that the long-term thermo-oxidative degradation, just like thermal degradation and photo-oxidation of polyamide 6.6, starts at the N-vicinal methylene groups.

Separation and quantification of the linear and cyclic structures of polyamide-6 at the critical point of adsorption.

The linear and cyclic structures of polyamide-6 were separated by liquid chromatography at critical conditions (LCCC) and identified with different mass spectrometric (MS) techniques and quantitated by LCCC with evaporative light-scattering detection (ELSD). Electrospray ionization MS was not suitable to identify the higher cyclic structures. For this purpose, matrix-assisted laser desorption ionization time-of-flight MS performed better and cyclic and linear structures were oligomerically resolved and separately identified in the mass spectrometer. The highest cyclic structure present and detected was the cyclic pentacontamer. It could be demonstrated that cyclic and linear oligomers follow different ionization and fragmentation routes/patterns. Quantification with ELSD of the components separated by LCCC using a universal calibration curve or an iterative procedure was developed. An area correction to account for different peak widths of coeluting components improves precision and accuracy of the calibration curve and improves quantitation accuracy for the samples analyzed. With these corrected values, no molecular mass dependency was observed for the cyclic and linear structures. Under critical conditions, the linear and cyclic structures of polyamide-6 were separated, identified and quantified.

Identification of caprolactam as a potential contaminant in parenteral solutions stored in overwrapped PVC bags.

Semipreparative liquid chromatographic separation and subsequent off-line mass spectrometry have revealed caprolactam as a new contaminant in intravenous solutions. The content of the lactam was found to be 1.2-15.0 mg l-1 determined by liquid chromatography. Contamination is attributed to migration of caprolactam from the protecting plastic envelope through the PVC barrier and into the intravenous solution. Migration occurs during the final heat sterilization process.