BPE-DNPH Cartridge for Simultaneous Determination of Ozone and Carbonyls
By: Shigehisa Uchiyama, Reporter EU Volume 33
The following was generated by an outside source using Sigma-Aldrich products. Technical content provided by: Shigehisa Uchiyama, Faculty of Engineering, Chiba University, 1-33, Yayoicho, Inage-ku, Chiba City, Chiba, 263-8522, Japan
The BPE-DNPH cartridge is a patent pending sampler for the simultaneous determination of ozone and carbonyls in air. This sampler is a two-bed cartridge system and each bed consists of reagentimpregnated silica particles. The fi rst contains trans-1,2-bis-(4-pyridyl) ethylene (BPE) while the second contains 2,4-dinitrophenylhydrazine (DNPH). Ozone in the air sample is trapped in the fi rst bed by the BPE-coated silica particles and reacts to form pyridine-4-aldehyde. Airborne carbonyls pass unimpeded through the BPE and are trapped in the second bed by the DNPH-coated silica particles where they react to form 2,4-DNPhydrazones. DNPH and carbonyl 2,4-DNPhydrazones are not infl uenced by ozone because of effective trapping by the BPE. All of the hydrazones derived from airborne carbonyls and pyridine-4-aldehyde (derived from ozone) are completely separated and measured using high-performance liquid chromatography.
The use of a BPE-DNPH-cartridge has made it possible to simultaneously determine ozone and carbonyls. A separate ozone scrubber is not necessary as the BPE portion of the sampler serves this function.
The air sample is drawn through the cartridge (see below, graphic) from the BPE bed to the DNPH bed at a fl ow rate of 100 mL/min for 24 hours or 1000 mL/min for 1 hour. Ozone in the air sample is trapped in the BPE-coated silica bed and produces pyridine-4-aldehyde. Carbonyls in the air sample are trapped in the DNPH-coated silica bed and produce carbonyl 2,4-dinitrophenylhydrazones without any interference by ozone.
Extraction is performed in the reverse direction to air sampling. Solvent passing through the BPE-DNPH cartridge washes DNPH into the BPE bed where it reacts with pyridine-4-aldehyde and forms the corresponding hydrazone derivative. The eluate from the BPE-DNPH cartridge contains hydrazones of the sampled carbonyls including pyridine-4-aldehyde formed from ozone.
Separation of pyridine-4-aldehyde and C1-C3 carbonyl-DNPH derivatives was achieved using an Ascentis RP-Amide column (565322-U , 15 cm × 4.6 mm, 3 μm). For the mobile phase, various concentrations of ammonium acetate in acetonitrile:water were tested, with 2 mM found to be optimal. Figure 1 shows the HPLC separation of pyridine-4-aldehyde (PA), formaldehyde (FA), acetaldehyde (AA) and acetone (AC) 2,4-DNPhydrazones in the solutions extracted from air samplers on the Ascentis RP-Amide column.
Figure 1. Pyridine-4-aldehyde and Other Carbonyl 2,4-DNPhydrazones from Ambient Air Sample
Both the limit of detection (LOD) and the limit of quantitation (LOQ) for the BPE-DNPH-method were calculated using the linear regression theory. A mixture of pyridine-4-aldehyde-DNPhydrazone, formaldehyde-DNPhydrazone, acetaldehyde-DNPhydrazone and acetone-DNPhydrazone (0.5 μg/L each) was analysed. The LOD and LOQ for the BPE-DNPH cartridge method was calculated as three and ten times the standard deviations, respectively, obtained from the data of 10 replicate measurements (Table 1). The reproducibility of the BPE-DNPH cartridge method was estimated from data of the six parallel air samplings.
Table 1. Limit of Detection, Limit of Quantification and Reproducibility of BPE/DNPH-Cartridge Method
Concentrations of ozone and carbonyls were measured in ambient air were collected by a DNPH cartridge, a DNPH cartridge coupled with a KI ozone scrubber, and a BPE-DNPH cartridge. Air collections were performed simultaneously in Chiba city, Japan, June-July 2007.
The KI scrubber adsorbed a considerable amount of moisture and some water vapour migrated into the DNPH cartridge. As a result, aldehyde and ketone concentrations show lower results compared to DNPH alone and the BPE-DNPH cartridge (Table 2).
Table 2. Aldehyde and Ketone Concentrations found under Different Ambient Conditions
The use of the BPE-DNPH cartridge permits the simultaneous determin ation of ozone and airborne carbonyls. A separate ozone scrubbing cartridge is not necessary with the BPE-DNPH cartridge because the BPE performs this function. Moreover, air sampling can be performed effectively during either high or low humidity conditions.
- Uchiyama, S. Anal. Chem. 2008, 80, 3285-90.