Development and Laboratory Testing of an Automated Monitor for the Measurement of Atmospheric Particle-Bound Reactive Oxygen Species (ROS)

Figures & data

TABLE 1 Tested functional groups and surrogate test compounds

Functional Group	Surrogate Compound
Hydroperoxide (HOO-)	1. Hydrogen Peroxide (HP) 2. tert-butyl hydroperoxide (TBHP)
Organic peroxide (R-OO-R′)	Di-tert-butyl peroxide (DTBP)
Alkyl Peroxy Radicals (ROO×)	2,2′-azobis (2-aminopropane) dihydrochloride
Redox active organics	Phenantroquinone (PQ)
Hypochlorite (OCl-)	Sodium hypochlorite (NaOCl)
Acids (R-COOH)	cis-Pinonic Acid (c-PA)
Alcohols (ROH)	2,4-hydroxy-3-methoxy-cinnamldehyde (HMCA)
Aldehydes (RCHO)	2,4-hydroxy-3-methoxy-cinnamldehyde (HMCA)

TABLE 2 Responses of the various ROS measurement agents with the surrogate compounds

	DCFH		POPHAA		DTT
	Response?	If Yes, Linear	Response?	If Yes, Linear	Response?	If Yes, Linear
HP	Yes	Yes, r^2 = 0.99	Yes	Yes, r^2 = 0.99	No	N/A
TBHP	Yes	Yes, r^2 = 0.65	No	N/A	No	N/A
DTBP	Yes	No	No	N/A	No	N/A
NaOCl	Yes	No	Yes	No	Yes	No
PQ in Me2SO	No	N/A	No	N/A	No	N/A
c-PA in MeOH	No	N/A	No	N/A	No	N/A
HMCA in MeOH	Yes	No	—	—	—	—
ROO ^a	Yes	No	—	—	—	—

FIG. 1 Schematic of the integrated ROS sampling-analysis system.

FIG. 2 Calibration plot of the system with standard H₂O₂ solutions.

FIG. 3 Concentration-time plot at various flow rates through the flow reactor.

FIG. 4 Box and Whisker plot of variation in the measured ROS concentrations indicated by the ROS Monitor with residence time in the flow reactor.

TABLE 3 Measured ROS concentrations (in nanomoles of equivalent H₂O₂) for different sampling intervals at 0.3 M α -pinene-hexane, ∼ 2.4 ppm ozone, and sampling flow rate of 18 LPM (reproduced from Venkatachari and Hopke 2007a)

Time of Sampling (hours)	Measured ROS Conc. (nanomoles)
1	7.56 ± 1.16
2	12.88 ± 2.15
3	18.15 ± 2.04

Venkatachari , P. and Hopke , P. K. 2007a . Development and Evaluation of A Particle-Bound Reactive Oxygen Species Generator . J. Aerosol Sci. , Accepted

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