Study on Dicarboxylic Acids in Aerosol Samples with Capillary Electrophoresis

Table 1

Method optimization data: the calibration of the DCAs. Experimental conditions: 4 mM PDA + 0.5 mM MTAH, pH 11.0; indirect detection at 310/266 nm (pilot/reference wavelength); sample injection for 6 sec. at 50 mbar; separation voltage −24 kV; analysis time 5 min.

Dicarboxylic acids	Concentration calibration equation	𝑅^2	Calibration range* [pg]	Minimum amounts (MDL)** [pg]
Oxalic acid (C2)	𝑦=0.2038𝑥+0.335	0.9996	1.03*–102.6	18.3**
Malonic acid (C3)	𝑦=0.1509𝑥+2.8785	0.9337	1.19–118.9	20.1
Succinic acid (C4)	𝑦=0.3199𝑥−0.0787	0.9994	1.02–102.6	15.2
Glutaric acid (C5)	𝑦=0.1107𝑥+1.4553	0.9367	1.02–101.6	11.4
Adipic acid (C6)	𝑦=0.1995𝑥+0.2539	0.9989	1.01–100.8	11.9
Pimelic acid (C7)	𝑦=0.1995𝑥+0.2539	0.9989	1.02–102.0	12.2
Suberic acid (C8)	𝑦=0.2064𝑥+1.4553	0.9978	1.0–100.0	15.2
Azelaic acid (C9)	𝑦=0.179𝑥+0.3412	0.9991	1.07–107.3	17.4
Sebacic acid (C10)	𝑦=0.1855𝑥+0.0131	0.9993	1.03–103.0	30.5
Mandelic acid (MA, IS1)	𝑦=0.1282𝑥+0.1979	0.9908	nd	nd
Trichloroacetic acid (TCA, IS2)	𝑦=0.031𝑥+0.3666	0.9778	nd	nd

∗Example about the calculations: Injection of 0.5 p.s.i. for 6 sec. 6 nL sample into the capillary, calculated with program CE Expert Lite; corresponds: 0.167 mg/L standard sample that is injected for 6 s at 0.5 p.s.i.; signal-to-noise ratio (S/N) used is 3. Oxalic acid in detection: 1.03 pg.
**Calculation made by similar ways as in calibration; signal-to-noise ratios (S/N) is 3; Oxalic acid in the filter sample: 3.05 mg/L.