1-2-bis(2-pyridyl)ethylene and 2-4-dinitrophenylhydrazine

A new diffusive sampling method for the simultaneous determination of ozone and carbonyls in air has been developed. In this method, silica gel impregnated with a mixture of trans-1,2-bis(2-pyridyl)ethylene (2BPE) and 2,4-dinitrophenylhydrazine (DNPH) is used as the absorbent; further, a porous sintered polyethylene tube (PSP-diffusion filter), which acts as a diffusive membrane, and a small polypropylene syringe (PP-reservoir) for elution of the analytes from the absorbent are used. The carbonyls present in air react with DNPH in the absorbent to form hydrazone derivatives. Concurrently, ozone in the air reacts with 2BPE to form pyridine-2-aldehyde, which immediately reacts with DNPH to form a pyridine-2-aldehyde hydrazone derivative. All the hydrazones derived from airborne carbonyls, including pyridine-2-aldehyde (formed from ozone), are completely separated and analyzed by high-performance liquid chromatography. The sampling rates of ozone (44.6 mL min(-1)) and formaldehyde (72.0 mL min(-1)) are determined by comparison with the rates obtained in an active sampling method. The sampling rates of other carbonyl compounds are calculated from the respective molecular weights according to a rule based on Graham's law. The calculated sampling rates agree with the experimental values. The DSD-BPE/DNPH method is advantageous because it is simple and allows for the simultaneous analysis of ozone and carbonyls.

Topics: Air Pollutants; Chromatography, High Pressure Liquid; Diffusion; Environmental Monitoring; Ethylenes; Formaldehyde; Hydrazones; Ozone; Phenylhydrazines; Polypropylenes; Pyridines

We have previously developed a new method using trans-1,2-bis-(4-pyridyl)ethylene (4-BPE) and 2,4-dinitrophenylhydrazine (DNPH) for the simultaneous determination of ozone and carbonyls in air using a two-bed cartridge system. In this method, 4-BPE was used to capture ozone. However, the method suffered from long reaction times in the eluate, low solubility of the DNPH derivative, and a strong dependence on atmospheric moisture. These problems could be overcome by using trans-1,2-bis-(2-pyridyl)ethylene (2-BPE) in place of 4-BPE. The efficiency of the reaction of ozone with 2-BPE to form pyridine-2-aldehyde (2PA) is higher than the corresponding reaction with 4-BPE. Under the optimized elution conditions, the reaction times of 2PA and 4PA with DNPH are within 15 and 120 min, respectively. In the elution from the sampling cartridge, 2PA formed from 2-BPE and ozone is easier to dissolve in the elution solvent. A stronger influence of humidity was observed in ozone recovery by the 4-BPE/DNPH method. 2-BPE exhibits a maximum reaction efficiency of 84% at 32% relative humidity (RH), while 4-BPE attains a maximum reaction efficiency of 82% at 49% RH. Humidity has much less influence on the reaction of 2-BPE with ozone. Above 18% RH, the reaction efficiency of 2-BPE with ozone is in the range 80-84%. Thus, 2-BPE is the more useful reagent for ozone analysis. The concentrations of ozone and carbonyls by the improved 2-BPE/DNPH method corresponded with the mean value by an ozone auto analyzer in an air monitoring station and a DNPH cartridge coupled with a KI-ozone scrubbing cartridge.

Topics: Air Pollutants; Carbon; Chromatography, High Pressure Liquid; Environmental Monitoring; Ethylenes; Ozone; Phenylhydrazines; Pyridines; Silicon Dioxide