Organophosphate esters in water,suspended particulate matter (SPM) and sediments of the Minjiang River,China

As organic pollutants of emerging concern, organophosphate esters (OPEs) have shown toxicity to organisms after entering the water environment. However, research on OPEs in freshwater in Southwest China is very limited. The levels, distribution and partitioning behavior of OPEs in the Minjiang River and their influencing factors is still unknown. In this study, six OPEs, tri-n-butyl phosphate (TnBP), tri(2-chloroethyl)-phosphate (TCEP), trichloropropyl phosphate (TCPP), triphenyl phosphate (TPhP), tributoxyethyl phosphate (TBEP), and tris(2-ethylhexyl)-phosphate (TEHP), were determined in surface water, suspended particle matter (SPM) and sediments of the Minjiang River. The results showed that the average concentrations of Σ₆OPEs in surface water, SPM and sediments of the Minjiang River were 199.32 ± 124.95 ng/L, 38463.79 ± 45641.89 ng/g dry weight (dw) and 76.45 ± 28.00 ng/g dw, respectively. High concentrations of OPEs were detected in SPM samples, indicating that more attention should be paid to pollution in SPM. It is worth noting that the variation trend of OPEs in SPM was almost opposite to that in water but basically similar to that in sediment. The proportions of alkyl OPEs in Σ₆OPEs increased from surface water to SPM and sediments. Alkyl OPEs were the main pollutants in SPM (10.44%–80.88% of Σ₆OPEs, mean of 54.52%) and sediments (59.08%–81.30% of Σ₆OPEs, mean of 68.91%), whereas chlorinated OPEs were the most abundant components in surface water (43.16%–75.99% of Σ₆OPEs, mean of 55.50%). The water-sediment partition coefficient (logK_OC) of OPEs was 4.97–7.58, while the water-SPM partition coefficient was 6.71–10.00. No significant correlations were found between logK_OW and logK_OC. K_OW was not the main factor affecting the distribution of OPEs in the Minjiang River, China.     

Prediction of the environmental distribution of alkyl dinitrates – Chromatographic determination of vapor pressure p0, water solubility SH2O, gas-water partition coefficient KGW (Henry’s law constant) and octanol-water partition coefficient KOW

Alkyl nitrates are complex mixtures of homologues and isomers and are part of the large NO_y pool of important atmospheric trace compounds. The knowledge of their physico-chemical parameters allows to forecast their partitioning into the environment. Water solubility, octanol-water partition coefficient, vapor pressure, and gas-water partition coefficient have been determined for 26 alkyl dinitrates by RP-HPLC and HRGC, respectively. Octanol-water partition coefficient (K_OW) and water solubility (S_{H 2 O}) were determined by C18 reversed-phase liquid chromatography using phenylalkanes as reference standards. Retention data obtained with methanol-water mixtures as eluents were extrapolated to 100% water. The vapor pressures were determined by capillary gas chromatography on a non polar stationary phase (CP-Sil 2, Chrompack). The octanol-water partition coefficients ranges from log K_OW = 1.4 for 1,2-ethyl dinitrate up to log K_OW = 5.9 for 1,2-decyl dinitrate, respectively. The experimental results are within ± 0.15 log units in agreement with calculations of log K_OW by the increment method according to Hansch and Leo. Water solubilities are in the range of 154 mol/m³ (23.1 g/L) for 1,2-ethyl dinitrate and 0.002 mol/m³ (0.5 mg/L) for 1,2-decyl dinitrate, respectively. The vapor pressures p⁰ _L ranges from 196 Pa for 1,2-ethyl dinitrate to 0.01 Pa for 1,10-decyl dinitrate (sub-cooled liquid value). The gas-water partition constants (dimensionless) or Henry’s law constants ranges from K_GW = 0.0005 (H = 1.28 Pa m³/mol) for 1,2-ethyl dinitrate to K_GW = 0.020 (H = 51.1 Pa m³/mol) for 1,2-decyl dinitrate.     

Synthesis of amphiphilic sulfonamide halogenated porphyrins: MALDI-TOFMS characterization and evaluation of 1-octanol/water partition coefficients

Porphyrins are key precursors for development of photosensitizers for photodynamic therapy. A new series of ortho-halogenated tetraarylporphyrins with sulfonamide substituents have been synthesized via chlorosulfonation reaction and characterized by MALDI-TOFMS. To predict their partition properties, log K_OW of a selected range of the synthesized halogenated amphiphilic porphyrins is described. A significant effect of the number and type of halogen group as well as on the number of sulfonamide side chain was observed. The determined 1-octanol/water partition coefficients showed that it is possible to obtain compounds with a wide range of lipophilicities, from log K_OW=−2.71 till log K_OW>4, which are suitable to optimize the biological efficacy of this class of sensitizers.     

Solubility and partitioning studies with polycyclic aromatic hydrocarbons using an optimized SPME procedure

In order to determine the water solubilitiy (S _W) and octanol/water partition coefficient (K _OW) of polycyclic aromatic hydrocarbons, we have optimized the direct solid-phase microextraction (SPME) of selected compounds (fluoranthene (FLU), phenanthrene (PHE), pyrene (PYR), benz[a]anthracene (BaA), benz[a]pyrene (BaP), and coronene) from the matrices water and octanol-saturated water. By the use of a 100 μm polydimethylsiloxane fibre and magnetic stirring of the sample with glass-coated mini-impellers in combination with gas chromatography we obtained limits of determination (GC-MS) comparable to standard HPLC procedures. Only coronene could not be quantified. The determined S _W of FLU agree with reference data; for B[a]P we have obtained a 2 to 3 times higher value than described in recent literature. The obtained K _OW values are close to reference data for both single components. For a mixture of FLU, PHE, PYR, and B[a]A the measured K _OW values are 0.2–0.3 log units below tabulated values for the single components. Received: 22 July 1998 / Revised: 28 October 1998 / Accepted: 1 November 1998     

Solubility and partitioning studies with polycyclic aromatic hydrocarbons using an optimized SPME procedure

In order to determine the water solubilitiy (S _W) and octanol/water partition coefficient (K _OW) of polycyclic aromatic hydrocarbons, we have optimized the direct solid-phase microextraction (SPME) of selected compounds (fluoranthene (FLU), phenanthrene (PHE), pyrene (PYR), benz[a]anthracene (BaA), benz[a]pyrene (BaP), and coronene) from the matrices water and octanol-saturated water. By the use of a 100 μm polydimethylsiloxane fibre and magnetic stirring of the sample with glass-coated mini-impellers in combination with gas chromatography we obtained limits of determination (GC-MS) comparable to standard HPLC procedures. Only coronene could not be quantified. The determined S _W of FLU agree with reference data; for B[a]P we have obtained a 2 to 3 times higher value than described in recent literature. The obtained K _OW values are close to reference data for both single components. For a mixture of FLU, PHE, PYR, and B[a]A the measured K _OW values are 0.2–0.3 log units below tabulated values for the single components. Received: 22 July 1998 / Revised: 28 October 1998 / Accepted: 1 November 1998     

Influence of Organic Matter on the Sorption of Cefdinir,Memantine and Praziquantel on Different Soil and Sediment Samples

Pharmaceuticals are known for their great effects and applications in the treatment and suppression of various diseases in human and veterinary medicine. The development and modernization of science and technologies have led to a constant increase in the production and consumption of various classes of pharmaceuticals, so they pose a threat to the environment, which can be subjected to the sorption process on the solid phase. The efficiency of sorption is determined by various parameters, of which the physicochemical properties of the compound and the sorbent are very important. One of these parameters that determine pharmaceutical mobility in soil or sediment is the soil–water partition coefficient normalized to organic carbon (K_oc), whose determination was the purpose of this study. The influence of organic matter, suspended in an aqueous solution of pharmaceutical (more precisely: cefdinir, memantine, and praziquantel), was studied for five different types of soil and sediment samples from Croatia. The linear, Freundlich, and Dubinin–Raduskevich sorption isotherms were used to determine specific constants such as the partition coefficient K_d, which directly describes the strength of sorbate and sorbent binding. The linear model proved to be the best with the highest correlation coefficients, R² > 0.99. For all three pharmaceuticals, a positive correlation between sorption affinity described by K_d and K_oc and the amount of organic matter was demonstrated.     

Development of negligible depletion hollow fiber membrane-protected liquid-phase microextraction for simultaneous determination of partitioning coefficients and acid dissociation constants

A new method based on negligible depletion hollow fiber-protected liquid-phase microextraction coupled with high-performance liquid chromatography (HPLC) was developed for the simultaneous determination of partitioning coefficients (K_OW) and acid dissociation constants (pK_a), by using phenol, 4-chlorophenol and 2,4-dichlorophenol as model compounds. A 37-mm length polypropylene hollow fiber membranes (600 μm inner diameter, 200 μm wall-thickness, 0.2 μm pore size, ∼70% porosity) with two-end sealed were filled with 1-octanol by ultrasonic agitation to prepare the extraction device. The extraction device was deployed in sample solutions, prepared by spiking target analytes in 1-octanol saturated aqueous solutions (500 mL), for negligible depletion extraction. After equilibrium was reached (∼5 h), the 1-octanol in the lumen of the hollow fiber membrane was collected for HPLC determination of the target analytes. As the depletion of the analytes in aqueous samples was negligible, the distribution coefficient (D_OW) could be calculated based on the measured equilibrium concentration in 1-octanol (C_O) and the initial concentration (C_W) in the aqueous sample of the target analyte (D_OW = C_O/C_W). The D_OW values measured at various pH values were nonlinearly regressed with pH to obtain the K_OW and pK_a values of a compound. Results showed that the measured values of the K_OW and pK_a of these model compounds agreed well with literature data.     

Water solubility and octanol/water-partitioning of hydrophobic chlorinated organic substances determined by using SPME/GC

The critical step in the determination of water solubilitiy (S _w) and octanol-water partition coefficient (K _ow) of hydrophobic organic chemicals by using the generator-column technique and the slow-stirring procedure, respectively, is the exact quantification of the low water-phase concentrations of the substances under investigation. We have tested the applicability of solid-phase microextraction (SPME) and gas chromatography with seven chlorinated organic compounds. The substances cover a S _w range from 500 mg/L to 7 ng/L and a log K _ow range from 3 to 8. The results show that SPME can be a valuable alternative to common preconcentration techniques in the quantification of hydrophobic organics in pure and octanol-saturated water. The apparent SPME distribution constants K _SPME (obtained with the 100 μm-PDMS fiber for analyte’s partitioning between fiber coating and aqueous sample) do not correlate directly with octanol/water partition coefficients and thus cannot be recommended as a surrogate parameter for K _ow.     

A rapid determination method of the air/water partition coefficient and its application

The air/water partition coefficient (K_aw) and Henry's constant (H) were measured by our own modified EPICS (Equilibrium Partitioning in Closed System) method, which uses two bubble columns. This method gives accurate K_aw data much more rapidly than other methods. In order to establish this method, the influence of airflow rate and the volume ratios of water in two columns to partition coefficient were carefully examined. Then we have measured K_aw for some n-alkanes, aromatic and chlorinated compounds. The experimental results of our modified EPICS method agreed very well with literature values. Besides the relationships between K_aw and molar volume, vapor pressure and water solubility were also analyzed.     

Lipophilicity Modulations by Fluorination Correlate with Membrane Partitioning

Bioactive compounds generally need to cross membranes to arrive at their site of action. The octanol-water partition coefficient (lipophilicity, logP_OW) has proven to be an excellent proxy for membrane permeability. In modern drug discovery, logP_OW and bioactivity are optimized simultaneously, for which fluorination is one of the relevant strategies. The question arises as to which extent the often subtle logP modifications resulting from different aliphatic fluorine-motif introductions also lead to concomitant membrane permeability changes, given the difference in molecular environment between octanol and (anisotropic) membranes. It was found that for a given compound class, there is excellent correlation between logP_OW values with the corresponding membrane molar partitioning coefficients (logK_p); a study enabled by novel solid-state ¹⁹F NMR MAS methodology using lipid vesicles. Our results show that the factors that cause modulation of octanol-water partition coefficients similarly affect membrane permeability.     

Sorption and partitioning parameters of benzotriazole compounds

Benzotriazole compounds have major commercial applications as anticorrosive agents in automotive antifreeze and airplane deicer fluids. This study assesses the sorption of benzotriazole (BT), 5-methylbenzotriazole (MBT), and 5-chlorobenzotriazole (CBT) from aqueous solutions to four top soils. The concentration range of 10-500 mg l⁻¹ was used with soils differing in total organic carbon content from 0.27 to 1.72%. Batch systems facilitated the equilibrium sorption with analysis by HPLC. The sorption of these compounds was as much as 60% by mass to a soil with 0.33% Org. C. The log octanol-water partition coefficients (log K_ow) were determined to be 1.23 for BT, 1.89 for MBT, and 2.17 for CBT. The relationship between the log of the sorption partition coefficient, log K_oc and log K_ow differed from previous correlations because hydrophobicity was not the only factor affecting sorption. These compounds have substantial permanent dipole moments as well as being hydrophobic. At high pH where CBT molecules approach their pK_a, sorption was approximately 50% less (by mass) than that of relatively non-ionized CBT molecules.     

Developing a QSPR Model of Organic Carbon Normalized Sorption Coefficients of Perfluorinated and Polyfluoroalkyl Substances

Perfluorinated and polyfluoroalkyl substances (PFASs) are known for their long-distance migration, bioaccumulation, and toxicity. The transport of PFASs in the environment has been a source of increasing concerned. The organic carbon normalized sorption coefficient (K_oc) is an important parameter from which to understand the distribution behavior of organic matter between solid and liquid phases. Currently, the theoretical prediction research on log K_oc of PFASs is extremely limited. The existing models have limitations such as restricted application fields and unsatisfactory prediction results for some substances. In this study, a quantitative structure–property relationship (QSPR) model was established to predict the log K_oc of PFASs, and the potential mechanism affecting the distribution of PFASs between two phases from the perspective of molecular structure was analyzed. The developed model had sufficient goodness of fit and robustness, satisfying the model application requirements. The molecular weight (MW) related to the hydrophobicity of the compound; lowest unoccupied molecular orbital energy (E_LUMO) and maximum average local ionization energy on the molecular surface (ALIE_max), both related to electrostatic properties; and the dipole moment (μ), related to the polarity of the compound; are the key structural variables that affect the distribution behavior of PFASs. This study carried out a standardized modeling process, and the model dataset covered a comprehensive variety of PFASs. The model can be used to predict the log K_oc of conventional and emerging PFASs effectively, filling the data gap of the log K_oc of uncommon PFASs. The explanation of the mechanism of the model has proven to be of great value for understanding the distribution behavior and migration trends of PFASs between sediment/soil and water, and for estimating the potential environmental risks generated by PFASs.     

Improved QSAR Analysis of the Toxicity of Aliphatic Carboxylic Acids

The results of a QSPR study of the toxicity of carboxylic acids in aqueous solution are reported. The molecular set comprises 35 carboxylic acids with the corresponding pK _a values in water. The set of molecular and topological parameters includes electrotopological state of the carboxy and methyl groups, molar refractivity, refractive index, n-octanol-water partition coefficient logKo/w, surface tension, and polarizability. Quite reasonable estimates are obtained, which improve the results of previous theoretical calculations.