Abstract
A new method to measure oxygen concentration in air-saturated organic solvents and binary mixtures has been developed. The methodology relies on the ability of HPLC columns to retain the molecular oxygen contained in different types of solvents which are injected into the system at 298.15 K. The outlet of the HPLC is coupled with an optical oxygen sensor which continuously measures changes in oxygen partial pressure.
Knowledge of oxygen solubility in different organic solvents and binary mixtures is of valuable importance both in photochemistry, where quenching of the excited state by molecular oxygen is one of the predominant processes, and in electrochemistry since the electrochemical reduction of oxygen is one of the most convenient methods to generate superoxide ions.
In the past few years most gas solubility measurements have been performed by physical methods using manometers or burets,1–4 by photochemical methods,5 by electron spin resonance,6 by gas chromatography7 or by optical oxygen sensing.8,9 Solubilities were also estimated by property–property correlation by knowing the boiling points, the heats of evaporation, the surface tensions and the polarizabilities of the different solvents.10 To the best of our knowledge this is the first time an HPLC method combined with optical oxygen sensor has been used to measure the solubility of oxygen in different media. The method described here is based on the ability of reverse phase chromatographic columns to retain the molecular oxygen contained in air saturated solvents. Standard volumes (5 μl) of different organic solvents are injected into the HPLC system (mobile phase: 50% methanol and 50% water at a flow rate of 0.5 ml min−1); the outlet of the HPLC is directly connected to an optical oxygen sensor which measures continuously the oxygen partial pressure.
The optical sensor used, pictured in Fig. 1, was built as follows: a glass capillary (i.d. = 0.2 mm) was first treated with 3-phenoxy-propyldimethylchlorosilane to enhance the adhesion of the sensing layer made of a thin film of PtTPTBPF (synthesised according to the literature11) in polystyrene (see the ESI†).
Knowledge of oxygen solubility in different organic solvents and binary mixtures is of valuable importance both in photochemistry, where quenching of the excited state by molecular oxygen is one of the predominant processes, and in electrochemistry since the electrochemical reduction of oxygen is one of the most convenient methods to generate superoxide ions.
In the past few years most gas solubility measurements have been performed by physical methods using manometers or burets,1–4 by photochemical methods,5 by electron spin resonance,6 by gas chromatography7 or by optical oxygen sensing.8,9 Solubilities were also estimated by property–property correlation by knowing the boiling points, the heats of evaporation, the surface tensions and the polarizabilities of the different solvents.10 To the best of our knowledge this is the first time an HPLC method combined with optical oxygen sensor has been used to measure the solubility of oxygen in different media. The method described here is based on the ability of reverse phase chromatographic columns to retain the molecular oxygen contained in air saturated solvents. Standard volumes (5 μl) of different organic solvents are injected into the HPLC system (mobile phase: 50% methanol and 50% water at a flow rate of 0.5 ml min−1); the outlet of the HPLC is directly connected to an optical oxygen sensor which measures continuously the oxygen partial pressure.
The optical sensor used, pictured in Fig. 1, was built as follows: a glass capillary (i.d. = 0.2 mm) was first treated with 3-phenoxy-propyldimethylchlorosilane to enhance the adhesion of the sensing layer made of a thin film of PtTPTBPF (synthesised according to the literature11) in polystyrene (see the ESI†).
| Originalsprache | englisch |
|---|---|
| Seiten (von - bis) | 6243-6245 |
| Fachzeitschrift | Analyst |
| Jahrgang | 138 |
| Ausgabenummer | 21 |
| DOIs | |
| Publikationsstatus | Veröffentlicht - 2013 |
Fields of Expertise
- Advanced Materials Science