Rapid determination of anionic surfactants in atmospheric aerosol in an urban area using an improved methylene blue method

The methylene blue method was troublesome and susceptible to operational error. In our improved method, we use only one vial (50 mL glass centrifuge tube) to determine the concentration of anionic surfactants as methylene blue active substances (MBAS). The combination of hand-shaking 20 times with shaking (1000 rpm) for 5 minutes by a shaker leads to a calibration curve (n = 4) with a high linearity (average r =0.996) and a high sensitivity (average 1.07 μM^-1) within 0 - 0.12 μM. In the optimum condition, the recovery of sodium dodecyl sulfate (SDS) was 94.7±3.3 % (n = 3) for a water extraction solution of blank quartz fiber filter, 92.3± 1.5 % (n = 4) for that of atmospheric aerosol collected on a quartz fiber filter, and 90.8± 3.5 % (n =3) for the throughfall of Japanese ceder (Cyptomeria japonica), respectively. This improved method revealed that the concentration of anionic surfactants in atmospheric aerosol ranged from 44.9 to 163 pmol m^-3 (84.3 pmol m^-3 on average, n =8) at Shinjuku, Tokyo in May, 2011.