The characterization of alcohol ethoxylates (AE) to determine ethylene oxide (EO) adduct distribution has been studied in our laboratory for many years by using high-performance liquid chromatography-mass spectrometry (LC-MS). This paper describes the LC-MS approach being used to analyze both nonderivatized and derivatized AE. We conclude that the best way to determine EO adduct distribution is by first converting the AE to alcohol ethoxy sulfates (AES) and then by using LC-MS with electrospray ionization in the negative ion mode. A convenient laboratory technique for converting small-scale samples of AE to AES has been discovered and is reported herein. Several examples of EO adduct distributions determined by this method are presented for both linear and isomeric AE samples. A method has been described to characterize the major anionic surfactant linear alkylbenzene sulfonate after derivatization by gas chromatography-mass spectrometry (GC-MS) (1). That method also has been applied to the analysis of sulfoxylated methyl esters (2). In this paper, the development of analytical methods to characterize surfactants is continued with the characterization of alcohol ethoxylates (AE). Aliphatic AE are widely used in household and industrial applications. They are produced by the catalytic addition of ethylene oxide (EO) to mixtures of aliphatic alcohols of oleochemical or petrochemical origin and have the general formula C x H 2x+1 O(CH 2 CH 2 O) y H. Commercially available AE are complex mixtures of linear and/or branched alkyl chains with the number of carbons ranging from 6 to 18 and the degree of ethoxylation varying from 1 to >25 mol. Numerous chromatographic methods, such as GC (3,4) supercritical fluid chromatography (5-8), thin-layer chromatography (9), high-performance liquid chromatography (HPLC) (10-18), HPLC-light-scattering detection (19), HPLC-nuclear magnetic resonance spectrometry (20), and capillary electrophoresis (21), have been published for AE characterization. A paper evaluating the efficiency and reliability of different chromatographic techniques was recently published by Trathnigg et al. (22). All these techniques produce suitable results for AE with linear alkyl chains; however, for branched-chain AE they yield unreliable data. Separation is the critical issue with these techniques. Owing to the complexity of branchedchain alcohol structures, it is difficult to imagine any analytical technique able to separate all AE components by alkyl carbon number and by ethoxy units (ethoxymers). Only MS coupled with HPLC, which combines chromatographic separation with ion detection, can produce the data for a detailed AE characterization. Earlier publications provide few examples of liquid chromatography-mass spectrometry (LC-MS) applied to the characterization of AE as pure sample or as detergent formulations (23-26). Other publications are mainly based on biodegradation studies (27-32). Most publications are evaluations of AE exposure in environmental compartments (33)(34)(35)(36)(37)(38)(39)(40)(41)(4...
A total reflection X-ray fluorescence (TXRF) procedure was developed for the determination of metal traces in petrochemical end products or intermediates for surfactant synthesis. The method combines a fast and straightforward sample preparation, i.e. deposition on the sample holder and evaporation of the sample matrix, with an efficient quantification method based on internal standardization (organic gallium standard). The method developed showed detection limits below 0.05 μg g(-1) and in most cases below 0.005 μg g(-1). Fifteen elements (Ca, Cd, Co, Cr, Cu, Fe, Mn, Mo, Ni, Pb, Rh, Sn, Sr, V and Zn) were determined in matrices such as paraffins, n-olefins, linear alkylbenzenes, long-chain alkyl alcohols and esters: typical metal contents were below 1 μg g(-1). The results were compared with the reference method ASTM D5708 (test method B) based on inductively coupled plasma optical emission spectroscopy: advantages and drawbacks of the two procedures were critically evaluated. The TXRF method developed showed comparable precision and absence of bias with respect to the reference method. A comparison of the performances of the two methods is presented.
A new analytical procedure for the determination of alcohol ethoxylates (AE) in environmental samples such as influents, effluents and sludge from waste water treatment plants (WWTPs) was developed. Although some work had been previously published on the detection of AE in water samples, this is the first paper that deals with AE in sludge. Alcohol ethoxylates were removed from water samples by sorption on polymeric discs followed by extraction with methanol. The methanol extracts were cleaned up with two alumina solid-phase extractions (SPE) at different conditions of solvent polarity, one before and the other after derivatization with naphthoyl chloride. A final polishing step was carried out on a Florisil SPE column. Liquid chromatography/mass spectrometry with electrospray ionization was used to quantify AE as naphthoyl derivatives. The detection limits for AE ethoxymers range from 0.07 to 0.005 lg/L in water samples. The method was applied to an Italian WWTP in order to follow the fate of AE during treatment, AE concentrations of 839 lg/L, 0.46 lg/L and 10.6 mg/kg were respectively found in the inlet, outlet and sludge samples. AE removals of each ethoxymer in the plant were in the range 99.6-100% and no difference was observed between high or low-mole ethoxymers and between AE with odd or even carbon chain lengths. An overall 99.7% removal was also determined on the mass balance of AE in the inlet, the outlet, and sludge of the plant.
The number of mobile hydrogens in biomolecules can be determined by fast atom bombardment (FAB) and desorption chemical ionization (DCI) mass spectrometry in association with, respectively, condensed-phase and gas-phase H/D exchange reactions. From the difference of molecular Ion masses recorded before and after D labeling, the number of mobile hydrogens could be easily determined on a variety of macrocyclic antibiotics, carrying up to 20 mobile hydrogens, as well as on some peptides and saccharides. In FAB experiments a new procedure has been developed which involves an In situ deuteration of both sample and matrix by repeated treatment with D20 directly on the FAB probe tip. This versatile procedure achieves high levels of deuterium substitution (94%-96%), avoids the risk of H/D back-exchange with atmospheric water, and allows the use of any water-soluble FAB matrix. In the DCI method the sample Is instantly evaporated in the cold Ion source filled with a rather high pressure of deuterated ammonia (ND3). Under such conditions, both molecular and fragment ions leaving the Ion source have undergone an almost complete (90%-98%) H/D exchange process with ND3. The presence of D-labeled fragment ions In DCI mass spectra significantly helps the comprehension of molecular structures and fragmentation mechanisms. Experimental parameters Influencing the extent of H/D exchange are discussed In detail.
Screening for fungicidal activity carried out on culture broths of soil Streptomyces strains resulted in the isolation of two new macrolide polyene antibiotics. AB021‐a and AB021‐b, endowed with good protective activity against some plant diseases. These compounds had no effect on seed germination or seedling development, while they strongly inhibited the growth of rice, carrot and periwinkle cells in liquid suspension culture. This inhibition may be ascribed to the lack of the cuticular barrier in these materials. Within a short period of incubation, some parameters connected with membrane permeability of rice, carrot and periwinkle cells were affected. An increase of oxygen consumption also occurred. Incubation of beetroot discs with AB021 led to increased conductivity of the external medium. In addition, a leakage of betacyanin occurred, suggesting a modification of transport processes, also at the tonoplast.
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