Simultaneous Determination of 6 Arsenic and 2 Chromium Species in Atmosphere PM_2.5 by High Performance Liquid Chromatography-Inductively Coupled Plasma Mass Spectrometry

The title method was proposed and used for simultaneous determination of AsC, AsB, As(Ⅲ), DMA, MMA, As(Ⅴ), Cr(Ⅲ) and Cr(Ⅵ) in atmosphere PM_2.5. The atmosphere PM_2.5 samples were collected with quartz filter membrane by air sampler under condition of flow rate of 100 L·min^-1 for 24 h at a fixed monitoring point. The filter membrane was divided into two equal parts, one of which was cut into pieces and placed in a 15 mL-centrifugal tube. An aliquot (6 mL) of mobile phase B (an appropriate amount of nitric acid was added into 50 mmol·L^-1 ammonium carbonate solution, to make the molarity of NO₃^- reach 80% of that of NH₄⁺, and the solution was adjusted to pH 8.35 by aqueous ammonia) containing 20 mmol· L^-1 ethylenediamine tetraacetic acid disodium salt was added, and the mixture was oscillated for 30 min. The extract was passed through a 0.45 μm filter membrane, and the filtrate was introduced into the high performance liquid chromatograph. The element species were separated on a HAMILTON PRP-X100 column by gradient elution of mixed solutions of water and mobile phase B at different volume ratios, and determined by inductively coupled plasma mass spectrometer in the form of ⁷⁵As and ⁵²Cr. The standard curves of the 8 element species showed the good linearity in the range of 1.0-50.0 μg·L^-1, and detection limits (3S/N) of the method were 0.003-0.025 ng·m^-3. The recoveries obtained by the spiked recovery test were in the range of 68.7%-112%, with RSDs (n=6) of the determined values in the range of 1.4%-9.2%. Ten PM_2.5 samples collected from the central and eastern regions of Shijiazhuang city were analyzed by the prescribed method, and As(Ⅴ) was detected in each of the 10 samples with the detection amounts in the range of 0.74-2.35 ng·m^-3. Small amounts of AsB, As(Ⅲ) and Cr(Ⅲ) were also detected in some samples collected from the eastern region, and detection amounts of arsenic did not exceed the annual limit (6 ng·m^-3) specified by GB 3095-2012.