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A commercial micromembrane suppressor, usually used to chemically suppress eluent conductance in ion chromatography, has been successfully used to effect ion replacement reactions in suppressed eluent streams. For 10 mM fluoride and 100 μM acetate, there were net decreases in conductance upon conversion of the acids to the sodium salts, showing that these concentrations were below their critical point concentrations (CPCs), defined here as the formal concentration above which a specified conjugate salt has a higher conductance than the same formal concentration of the weak acid. For 10 mM carbonate and 10 μM borate, there were net increases in conductance, showing that these concentrations were above their respective CPCs. The most effective of several ion replacement reagents investigated was EDTA at pH 11, which, for 5.0 mM borate, produced 250- and 1400-fold increases in peak height and peak area, respectively, compared with a normal IC system and low background conductance. The applicability of the sy...

Nonylphenol ethoxylate (NPE) and primary alcohol ethoxylate (PAE(9-6)) were degraded using heterogeneous photocatalysis. An aqueous surfactant solution (2L, 2000 mg/L) containing TiO2 catalyst (0.1 % w/v) was irradiated with a 400W Blacklight lamp. Analyses of the starting material and degradation intermediates were performed using gas chromatography (GC), gas chromatography-mass spectrometry (GC-MS), electrospray mass spectrometry (ESMS) and nuclear magnetic resonance spectroscopy (NMR). Identified intermediates suggested that the ethylene oxide chain was more susceptible to degradation than aliphatic or aromatic moieties. Competitive degradation was also observed. NPE was degraded more rapidly than PAE(9-6).

Silica and polyimide coatings were successfully applied to both sides of 10 MHz AT-cut quartz crystal resonators with silver and gold electrodes. A similar oscillation was observed for the uncoated and coated resonators in air, deionised water, 0.1 M NaCl and propylene glycol, in terms of the complex impedance analysis. The impedance module decreased with increasing conductance of the surrounding media while the resonant frequency appeared to depend on the liquid viscosity and density. However, differences in the oscillation were evident when these devices were immersed in waste water from a clean room for microelectronic fabrication. Relevant chemical analyses were also made on the waste water samples. Hourly testing results indicated that changes in the impedance were due to metal ions (Na+, K+, Ca2+, etc.) and the frequency shift comes from the complicated interaction between the solute molecules (propylene glycol) and the coatings or electrodes. This study highlights that the multi-sensors with various coatings and electrodes provide possibilities to monitor waste water in real-time.

The Microtox® test was successfully used to measure EC50 values of nonionic polyethoxylate surfactants. However, toxicity measurements of real samples that contain surfactants above a particular concentration, termed the critical toxicity concentration (CTC) are not valid. These samples require dilution before the test is performed, and because the relationship between toxicity and concentration is not linear above the CTC, the EC50 cannot be extrapolated back to give the toxicity of the original concentrated sample and a true estimation of toxicity is therefore not possible. This phenomenon may be related to the minimum surface tension requirement of the bacteria or other physical properties of the surfactant such as the tendency to assemble at interfaces and surfaces and the tendency to form micelles.

Secondary alcohol ethoxylate (SAE) was photocatalytically degraded using a suspension of TiO 2 particles irradiated with long wavelength ultraviolet light. High starting concentrations of SAE were used (ca. 2000 mg/L), and changes in both SAE oligomer distribution and production of intermediates were monitored by using GC, GC/MS, NMR, and ESMS. Initial preferential cleavage of the ethoxyl groups over H0 . reactions with the aliphatic portions of the molecule is followed by cleavage at the secondary carbon. Relatively hydrophilic intermediates remained in solution, while the hydrophobic products adhered to the TiO 2 , causing agglomeration of the particles.

Electrospray mass spectrometry (ESMS) has been used to identify the mixture of components in three nonionic surfactants, nonylphenol ethoxylate (NPE), secondary alcohol ethoxylate (SAE), and primary alcohol ethoxylate (PAE). In each case singly protonated species are observed with the number of ethylene oxide units ranging from 4 to 16. Collisionally activated decomposition of protonated SAE leads to cleavage of the secondary carbon-oxygen bond to give protonatea ethylene oxide fragment ions. ESMS is used to show that the products of the photocatalytic decomposition of SAE are the same as those produced by the collisionally activated decompositions

Solutions prepared by suspending freeze-dried sludge in water were found to contain aggregated particles of about 1000-nm size and substantial concentrations of surfactants. The microparticles sorbed significant amounts of the organophosphorus (OP) pesticide diazinon, causing low recoveries and a decrease in observed partition coefficients with an increase in the suspended sludge concentration. The microparticles could be removed by prewashing the sludge, by filtration, or by passing the solution through a C-18 cartridge, which effectively acted as a filter. In contrast to diazinon, the recovery of the more polar OP propetamphos was excellent. Microparticles were not significant in muffled sludge obtained from the same source but were significant in three waste streams at a sewage treatment plant, including the final effluent

The procedures needed for the optimisation of programmable fluorescence detectors have been investigated. We found that wavelength programs had to be developed from data obtained from the particular detector for which the program was to be used -programs reported in the literature or developed from data obtained on other instruments gave substantially lower sensitivities. The wavelength program we developed was a compromise between: chromatographic separation, abundance and relative sensitivitv of each PAH; the ease with which a timed event could be included in the clution profile and; the relative importance of each PAH to the analyst. The success of programmable fluorescence detection was dependant on the reproducibility with which the detector was able to reset specified wavelengths, with corresponding detector response variabilitv of up to 20% for one new detector.

Weak-acid anions such as borate and cyanide, present problems in chemically suppressed ion chromatography, since the acids are weakly ionised, giving low conductivity and therefore decreased sensitivity. For borate this problem was overcome by converting the weak acid to its sodium salt, by the use of a second anion micromembrane suppressor (AMMS) as an ion exchange reactor (IER), flushed by EDTA reagent, to supply sodium ions for the conversion. This paper will discuss the use of this IER system to determine cyanide, which is also a very weak acid, with a similar pKa to borate. The detection limit for cyanide of 50 μM compare favourably with indirect conductivity detection.

Anions of weak acids can represent a problem when determined via chemically suppressed ion chromatography as the acids can be weakly ionised, giving low conductivity and hence low sensitivity. Previous work showed that converting some weak acids back to their sodium salts, using a second micromembrane suppressor, greatly enhanced conductivity and thus sensitivity. This paper will discuss further work in optimising the conversion for boric acid by using sodium salts of EDTA and the mechanisms involved.

A quartz crystal microbalance (QCM) technique has been employed to examine the detergency process involved when solid organic soils are removed from hard surfaces by surfactants. Experiments have been designed to focus on real time monitoring of the physicochemical aspects of detergency. Two model soils, tripalmitin and dotriacontane, have been investigated. Water absorption by the model soils has been monitored, through the change in resonance frequency of the coated crystal, as a function of time of immersion in high purity water solutions. Water and surfactant absorption and the rate of removal of the model soils upon immersion of the coated QCM crystal in aqueous surfactant solutions have also been monitored. Specifically, results obtained with the surfactants pentaethylene glycol mono-n-dodecyl ether (C12E5) and octaethylene glycol mono-n-dodecyl ether (C12E8) have shown that the QCM technique can be employed to identify several distinct stages in the soil removal process and to rank surfactants in t...

A quartz crystal microbalance (QCM) has been employed to monitor the removal of two model solid organic soils, dotriacontane and tripalmitin, from the hard surface of the QCM crystal in aqueous surfactant solutions of octa-ethyleneglycol mono n -dodecyl ether (C 12 E 8 ). We have investigated the effect of varying the thickness of the soil coating on soil removal and the effect of soaking the soil in high-purity water for an extended period of time before adding surfactant. The QCM results support the view that net soil removal is preceded by a stage of water and surfactant penetration into the soil. The rate of penetration and rate of removal depends on the soil type. Water and surfactant take longer to penetrate dotriacontane compared to tripalmitin coatings. The removal process also occurs over a longer period of time in the case of dotriacontane coatings. The percentage of material removed is less for dotriacontane, compared to tripalmitin coatings. The initial coating thickness on the hard surface does not appear to govern the final percentage of soil removed, at least in the thickness range accessible to the QCM (approximately ≤800 nm). Immersing the soil coated surfaces in water for a relatively long time, hastens the onset of the removal stage after surfactant is added but does not significantly influence the rate and extent of removal from the hard surface.

The crystal structure of [Pd(dam)Cl]2CO (dam = Ph2AsCH2AsPh2) shows that the palladium atoms are not directly bonded or halogen bridged but that they are spin-paired via an unusual bridging carbonyl group.

The crystal structure of [Pd(dppm)Br]2(dppm = Ph2PCH2PPh2) shows that the palladium(I) atoms are directly metal–metal bonded and adopt an idealised square-planar stereochemistry.

The reactions of Pd(CO)X (X = Cl, Br) with bis(diphenylphosphino)methane (dpm) and its arsenic analogue, dam, have been investigated. The iodo complexes were prepared indirectly. Ligand dpm gives complexes of the formula [Pd(dpm)X]2. With dam, the nature of the product depends upon the identity of the halogen; with X = Cl, Br the products are [Pd(dam)X]2CO, but the iodo derivative is [Pd(dam)I]2. N.m.r. spectroscopy suggests that [Pd(dam)I]2 has a structure different to the dpm complexes. ��� [Pd(dam)Cl]2CO,3C6H14 is tetragonal, space group P4I, a 22.0458(1), c 14.4345(1) Ǻ containing four dimer units per unit cell. The structure was refined to R 0.096 and Rw 0.097 for 1698 independent reflections. The crystals are molecular being composed of discrete dimeric molecules of the complex and solvent. The palladium coordination is approximately square planar with two trans arsenic atoms, terminal halogen and the bridging carbonyl group which is common to both metal environments. There is no twist about the Pd-Pd axis so the Pd,As, unit is planar. The Pd-Pd distance of 3.274(8) Ǻ is too long for a direct metal-metal bond. However, the compound is diamagnetic so spin pairing must occur through the unusual carbonyl bridge.