Antarox CO-880 Research Articles

Phase change and viscosity effects on a quartz crystal microbalance

The mass–frequency dependence for various materials deposited onto the surface of a resonating quartz crystal was investigated. The relationship is linear, but the constant of proportionality is different for different materials deposited. Such frequency changes are commonly described by the Sauerbrey equation, but in this experiment the equation was found to be in error by factors of up to 23. This can be accounted for by changes in surface viscosity. Slow temperature changes of a resonating quartz crystal coated with the polymer Antarox CO-880 revealed a significant frequency minimum at the phase-transition points. This is also attributed to a change in the viscosity of the coating at transition. The phase-transition temperature for this polymer was verified by differential scanning calorimetry. Quartz crystal techniques may provide a simple, accurate method for the measurements of phase-transition temperatures.

Denuder tube preconcentration and detection of gaseous ammonia using a coated quartz piezoelectric crystal

The feasibility of using a cylindrical denuder tube for sampling gaseous ammonia, followed by detection with a piezoelectric quartz crystal, was investigated. Gaseous ammonia was sampled with a tungsten oxide-coated cylindrical denuder tube and then thermally desorbed onto a piezoelectric quartz crystal coated with pyridoxine hydrochloride–Antarox CO-880. A linear calibration graph of peak area response versus ammonia concentration sampled was obtained for ammonia concentrations between 3.1 and 8.2 µg l–1. A concentration of 29 ng l–1 of ammonia in air was detected with a signal-to-background ratio of 14:1 by achieving an enrichment ratio of 900 with the tungsten oxide denuder tube.

Comparative barium ion sensing qualities of planar and tetrahedral tripodal receptor molecules

Nine acyclic polyethers, representing examples of planar and tripodal ‘scorpion-like’ molecules, each with oligoether ‘tails’ and a pair of anionic ‘pincers’, were evaluated as possible barium ion-selective electrodes (ISEs) when incorporated into a poly(vinyl chloride) matrix membrane with 2-nitrophenyl phenyl ether as the solvent mediator. The general performance was inferior to a traditional ISE based on the tetraphenylborate salt of the barium complex with α-(nonylphenyl)-ω-hydroxy-catena-poly(oxyethylene)(Antarox CO-880 with 30 oxyethylene units). However, a general barium ion response seems to be favoured by a tetrahedral tripodal structure (sensor C, electrode 3), with its design promoting good ion–dipole interactions, as seen in another study on the association constants of these acyclic polyethers with barium ions. A more extensive study of the effect of methoxylated benzyl groups on similar type groups in the pincer positions for the tetrahedral tripodal structures is indicated.

Potentiometric behaviour of lanthanum polyalkoxylate complexes in PVC membrane electrodes: effect of plasticizers and applications

Tetraphenylborate salts of lanthanum complexes of nonylphenoxypolyethyleneoxyethanol (Antarox CO-880) and polypropylene glycol-425 (PPG-425) have been prepared and examined for their applicability as sensing species for lanthanum ions by incorporating them in a poly (vinyl chloride) membrane system in the presence of 2-nitrophenyl phenyl ether (NPPE), dioctylphenyl phosphonate or a mixture of both as plasticizers. Almost all of the systems studied showed an excellent response for lanthanum ions in pure solutions with a near Nernstian response of 18–20 mV per decade between 10 −5 and 10 −1 M lanthanum and a static response time of less than 1 min. Among the systems studied, lanthanum(Antarox CO-880)TPB/100% NPPE (TPB=tetraphenylborate) was the best in terms of tolerance to interfering ions. K +, Ba 2+, Pb 2+ and Al 3+ were serious interferents, but most other interferents investigated were tolerable at [La 3+] > 10 −4 M. Plasticizers were found to be decisive in determining the sensor selectivity towards the different metal ions. A lanthanum(Antarox CO-880)TPB/100% NPPE PVC membrane electrode was utilized for the potentiometric titration of fluoride, in sodium fluoride, against lanthanum nitrate solutions. It proved to be successful for fluoride concentrations of ⩾ 10 −3 M.

Studies on lead ion-selective electrodes based on polyalkoxylates

The performance of the tetraphenylborate (TPB) salts of lead complexes with non-ionic surfactant polyalkoxylates, namely polyethylene glycol 1540 (PEG 1540), Antarox CO-880 and polypropylene glycol 425 (PPG 425) as the active sensors for Pb2+ ions in poly(vinyl chloride)(PVC) membrane electrode systems has been assessed using 2-nitrophenyl phenyl ether (NPPE), dioctylphenyl phosphonate (DOPP) or dipentylpentyl phosphonate (DPPP) and their mixtures as plasticising solvent mediators. The PVC electrode based on Pb. Antarox CO-880. TPB-NPPE showed a higher selectivity towards Pb2+ ions in the presence of a large number of interferent metal ions and had a near Nernstian response between 10–1 and 10–5 mol dm–3 of Pb2+.In terms of range, the next best electrode was that based on Pb. PPG-425. TPB-DOPP, but this suffered from more interferences than the Pb. PPG-425. TPB-NPPE analogue and was of short range (down to 10–4 mol dm–3). The three electrodes, Pb. Antarox CO-880. TPB-NPPE, Pb. PPG-425. TPB-DOPP and Pb.PPG-425. TPB-20% DOPP + 80% NPPE, showed good end-point breaks in the potentiometric titration of sulphate in 80% ethanolic solutions with lead perchlorate, the best being the electrode based on Pb. PPG-425. TPB-DOPP. However, the lead(II) titrant system is susceptible to the interference by hydrogen peroxide that can occur in some analytes.

Characterisation of poly(vinyl chloride) barium ion-selective electrodes without an internal reference solution

Two types of poly(vinyl chloride)(PVC) barium ion-selective electrodes are compared. Each electrode is based on a sensor formed from the tetraphenylborate of the non-ionic surfactant Antarox CO-880 and its complex with barium (tetraphenylborate complex) and uses 2-nitrophenyl phenyl ether as solvent mediator. The first electrode is an original type, fabricated as a classic PVC model, whereas in the second, the PVC sensor material is applied to the outer surface of an epoxy resin and has no internal filling solution. Apart from the fact that the epoxy-based electrode has a longer lifetime, the two types of ISE possess virtually identical electrochemical properties. The electrodes were also assessed for measuring sulphate by analate subtraction.

X-ray fluorescence and radiotracer studies of polyalkoxylate interactions with potentiometric electrode PVC matrix membranes containing barium-polyalkoxylate complexes

Solution-membrane interactions for PVC matrix membranes containing 2-nitrophenyl phenyl ether plasticising solvent mediator and tetraphenylborates of various barium complexes with polyalkoxylates have been studied for various polyalkoxylate-containing solutions using X-ray fluorescence (XRF) and a 14C radiolabelled nonylphenoxypolyethoxylate [Antarox CO-880 with 30 ethoxylate units (EOUs)]. The PVC matrix polyalkoxylate membranes were based on Antarox CO-880 (Type I), Antarox CO-730 (15 EOUs, Type II), Antarox CO-430 (four EOUs, Type III), Glucam P20 (methyl glucoside polyalkoxylate with 20 AOUs, Type IV) and Glucam P10 (10 AOUs, Type V), and the solutions contained Antarox CO-880 and Glucam P20, either individually or in admixture, each at 1.95 × 10–4M.The XRF data indicated that soaking the membranes in de-ionised water led to a depletion of barium ions at the membrane surface for membranes of Types II-V, and especially for membrane Types III–V, but when alkoxylate was in solution this tendency was reduced, particularly for Antarox CO-880. Types III–V membranes, after soaking in Antarox CO-880, showed considerably improved potentiometric barium ion-sensing qualities as a result of barium-Antarox CO-880 complex formation on the membrane surface, as confirmed by scanning electron microscopy and ESCA spectra. The radiotracer data also showed that Antarox CO-880 was absorbed by membranes of Types II–V. Together with the other data these show the mechanistic basis for the potentiometric response of barium-alkoxylate complex-based membrane electrodes to alkoxylates in solution to be the complexation of barium ions in the membrane and/or the membrane/solution interface.

Electrode membrane and solvent extraction parameters relating to the potentiometry of polyalkoxylates

Poly(vinyl chloride)(PVC) matrix membrane electrodes containing various amounts and compositions of liquid ion-exchanger were studied in order to investigate their response to aqueous solutions of Antarox CO-880 as a model polyalkoxylate. The liquid ion-exchanger used in the membrane was based on solutions in 2-nitrophenyl phenyl ether of the tetraphenylborates of complexes with barium of either Antarox CO-880 or Antarox CO-430 polyethoxylates. Barium ion-responses were also noted.

Piezoelectric quartz crystal detection of ammonia using pyridoxine hydrochloride supported on a polyethoxylate matrix

The use of a nonylphenoxypolyethoxylate (Antarox CO-880) as a support polymer is confirmed as a means of prolonging the life (to >50 d) of pyridoxine hydrochloride as a sensitive sorbent coating during the piezoelectric crystal detection of ammonia. However, the matrix system incurs possible interference from hydrogen chloride gas although, except for triethylamine, the other gases studied at high levels (sulphur dioxide, nitrogen dioxide, carbon dioxide and hydrogen sulphide) give only a small piezoelectric signal. The extreme sensitivity of the piezoelectric crystal detection of ammonia to below the µg dm–3 range is inconsistent with the Sauerbrey equation, which normally applies to straightforward deposition on piezoelectric transducers. This is a consequence of the low slopes of the log(frequency decrease)versus log(concentration) graphs. Such slopes can be increased by modifying the syringe dilution procedure, but there are other more intransigent factors involved.

A polymer support for pyridoxine hydrochloride used as a sorbent for the piezoelectric quartz crystal detection of ammonia

A high molecular mass polyalkoxylate, Antarox CO-880 (nonylphenoxypolyethoxylate with 30 ethoxylate units) is a suitable matrix for supporting pyridoxine hydrochloride (an ammonia sorbent) on a quartz piezoelectric crystal detector. The matrix helps considerably to extent the useful lifetime of the detector from ca. 10 to >53 days.

Radiotracer studies on ion-selective electrode membranes containing metal complexes of a nonylphenoxypoly(ethyleneoxy)ethanol in poly(vinyl chloride) matrices

Radiotracer studies with 133Ba, 45Ca and 36Cl are reported for PVC matrix membranes containing 2-nitrophenyl phenyl ether and the tetraphenylborate of a barium (or calcium) complex with a nonylphenoxypoly(ethyleneoxy)ethanol (NP), Antarox CO880. The results show that there is very limited permeation of radioactive barium and calcium ions through the membrane systems. However, the continued uptake (with time) of radioactive barium ions by the membranes (the uptake of calcium ion is less) suggests that in relation to selective electrode response the stabilization of ions by the NP ligand within the membrane is important in addition to the simple availability of membrane pathways for primary-ion transport through the membrane. Permselectivity to counter-ions is indicated by the non-permeation of radioactive chloride ions.

Barium-polyethoxylate complexes as potentiometric sensors and their application to the determination of non-ionic surfactants

Electrodes having PVC matrix membranes consisting of 2-nitrophenyl phenyl ether and sensors of the tetraphenylborate salts of barium complexes with Antarox CO-730, Antarox CO-430, Lutensol AO7 and Monflor 51 are compared with the corresponding electrodes of barium complexes with Antarox CO-880. Generally, they are inferior to the Antarox CO-880 electrodes for sensing barium ions. However, all of the electrodes respond to non-ionic surfactants in the manner described previously for the Antarox CO-880 system.The electrode based on Antarox CO-430 is considered to be superior in its response to non-ionic surfactants and shows some selectivity towards these materials compared with its response towards cationic and anionic surfactants. The electrode has been evaluated for determining Dobanol 25-7, Synperonic 7 and Lutensol AO7 in detergent powders with good recoveries of the non-ionic surfactants and relative standard deviations ranging between 0.8 and 4.0%. The recommended procedure is based on known (standard) addition which, although taking up to 2 h to complete, is faster than analate addition.

Solvent mediator studies on barium ion-selective electrodes based on a sensor of the tetraphenylborate salt of the barium complex of a nonylphenoxypoly-(ethyleneoxy)ethanol

The barium ion-selective electrode sensor based on the neutral carrier complex of a nonylphenoxypoly(ethyleneoxy)ethanol containing 12 ethylene oxide units and 2 mol of tetraphenylborate ion per mole of Ba2+(12 EOU. Ba.2TPB) requires a more viscous solvent mediator than 4-nitroethylbenzene for long-life poly(vinyl chloride)(PVC) matrix-membrane barium ion-selective electrodes. Both 2-nitrophenyl octyl ether and di-2-nitrophenyl ether used in conjunction with the sensor in a PVC matrix membrane give functional barium ion-selective electrodes, but those with di-2-nitrophenyl ether mediator are far superior with lifetimes of about 30 d. Barium ion-selective electrodes with the sensor and mediator in liquid membranes can be made for a wide range of nitro-aromatic solvent mediators.Barium ion-selective electrodes made from discs taken from a master membrane containing 0.40 g of a saturated solution of Antarox CO-880. Ba.-2TPB in di-2-nitrophenyl ether can be used as indicator electrodes for the potentiometric titration of SO42– with Ba2+. A role for a potentiometric titration finish in the determination of sulphur in organic compounds by the oxygen-flask method is recommended.