BPE-DNPH Cartridge for Simultaneous Determination of Ozone and Carbonyls

By: Shigehisa Uchiyama, Reporter EU Volume 33

Contributed Article

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.

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Measuring Procedure

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.

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HPLC Analysis

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

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Accuracy and Precision

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

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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.

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  1. Uchiyama, S. Anal. Chem. 2008, 80, 3285-90.

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