Mass spectrometric behaviour of carboxylated polyethylene glycols and carboxylated octylphenol ethoxylates

Parallel pathways of ethoxylated alcohol biodegradation under aerobic conditions

Non-ionic surfactants (NS) are a major component of the surfactant flux discharged into surface water, and alcohol ethoxylates (AE) are the major component of this flux. Therefore, biodegradation pathways of AE deserve more thorough investigation. The aim of this work was to investigate the stages of biodegradation of homogeneous oxyethylated dodecanol C12E9 having 9 oxyethylene subunits, under aerobic conditions. Enterobacter strain Z3 bacteria were chosen as biodegrading organisms under conditions with C12E9 as the sole source of organic carbon. Bacterial consortia of river water were used in a parallel test as an inoculum for comparison. The LC-MS technique was used to identify the products of biodegradation. Liquid-liquid extraction with ethyl acetate was selected for the isolation of C12E9 and metabolites from the biodegradation broth. The LC-MS/MS technique operating in the multiple reaction monitoring (MRM) mode was used for quantitative determination of C12E9, C12E8, C12E7 and C12E6. Apart from the substrate, the homologues C12E8, C12E7 and C12E6, being metabolites of C12E9 biodegradation by shortening of the oxyethylene chain, as well as intermediate metabolites having a carboxyl end group in the oxyethylene chain (C12E8COOH, C12E7COOH, C12E6COOH and C12E5COOH), were identified. Poly(ethylene glycols) (E) having 9, 8 and 7 oxyethylene subunits were also identified, indicating parallel central fission of C12E9 and its metabolites. Similar results were obtained with river water as inoculum. It is concluded that AE, under aerobic conditions, are biodegraded via two parallel pathways: by central fission with the formation of PEG, and by Ω-oxidation of the oxyethylene chain with the formation of carboxylated AE and subsequent shortening of the oxyethylene chain by a single unit.

Monitoring of selected non-ionic surfactants in river water by liquid chromatography-tandem mass spectrometry

Alcohol ethoxylates (AEs) are a significant component of the non-ionic surfactant (NS) flux discharged into surface water. Due to the polydispersity of the majority of NS, they are easily recognizable by their 'fingerprints', i.e. a series of mass peaks which differ by m/z = 44, namely the m/z of a single oxyethylene subunit. Dodecanol ethoxylates (C12EOx) represent AEs from both renewable and petrochemical sources. Therefore, C12Ex are suitable fingerprints of NS in the aquatic environment. The aim of this work was to develop an LC-MS/MS method suitable for AE monitoring in river water. River water samples taken from the River Warta in Poznan (Poland) were extracted with ethyl acetate, evaporated, reconstituted in the mobile phase and processed by the LC - Multistage MS procedure (LC-MS/MS) using optimum multiple reaction monitoring (MRM). The method of multiple standard additions was used for the evaluation of each AE fingerprint concentration. The concentration of C12EOx having 2-9 oxyethylene subunits was determined. Standards for higher C12EOx are not yet available. The developed method offers an LOD of between 1 and 9 ng L(-1), and is suitable for the monitoring of NS fingerprints in river water. The range of C12EO2-9 concentrations determined in the River Warta varied within two orders of magnitude in all cases. The lowest determined concentration was 17 ± 1 ng L(-1), while the highest was 2.6 ± 0.14 μg L(-1). The total concentration of C12EO2-C12EO9 homologues varied between 1.4 and 11.2 μg L(-1). A relatively high concentration of short-chained homologues (2-5 oxyethylene subunits) was observed in the investigated river water. This provides evidence of a biodegradation pathway involving the gradual shortening of the AE oxyethylene chain. Distinct evidence was also obtained of unregulated NS discharges into the river.

Cationization versus surface activity--the effect on electrospray ionization

Ethoxylated fatty alcohols, C(12)E(1), C(12)E(2), C(18)E(1) and C(18)E(2), were studied by electrospray ionization mass spectrometry (E is the ethoxylene unit OCH(2)CH(2)). For compounds containing two ethoxylene units, which form quite stable adducts with sodium cation, the abundances of [M + Na](+) ions were not affected by alkyl chain, so the hydrophobic effect was not observed. For the compounds containing one ethoxylene unit, forming rather unstable adducts with sodium, the hydrophobic effect was clearly seen since the [C(18)E(1) + Na](+) ion was more abundant than the [C(12)E(1) + Na](+) ion. Two ethoxylene units are not able to form stable adducts with potassium cations, therefore the hydrophobic effect was observed for the [C(12)E(2) + K](+) and [C(18)E(2) + Na](+) ions, the latter being more abundant than the former. For lithium cation adducts with C(12)E(1) and C(18)E(1), the hydrophobic effect was observed, but was less manifested than for sodium cations since lithium adducts are more stable than sodium ones. C(18)E(1) and C(18)E(2) gave more intense signals at higher cone voltage values than C(12)E(1) and C(12)E(2), respectively. However, this is not related to the hydrophobic effect but to the collisions being less effective for the former.

Electrospray ionization mass spectrometry of pyrimidine base-rubidium complexes

Nucleobases and alkali metal cations, under electrospray ionisation conditions, tend to form the so-called magic number clusters (unusually stable clusters in comparison with the neighbouring ones). The effect of the ion source parameters, namely cone voltage and desolvation temperature and relative concentrations of thymine and RbCl on the [T5+Rb]+ ion abundance has been studied.