A Temperature Calibration Procedure for the Sunset Laboratory Carbon Aerosol Analysis Lab Instrument

Figures & data

TABLE 1 The IMPROVE_A carbon sub-fraction measurement conditions including the target filter temperatures and the sample oven sensor setpoint temperatures (T_SETPOINT) for the UCD Sunset Analyzer (S/N 119) that produce the IMPROVE_A temperatures at the filter

		IMPROVE_A
IMPROVE_A	IMPROVE_A	Filter	TSETPOINT
Carbon fraction	Carrier gas	temperature (°C)	(°C)
OC1	He	140	195
OC2	He	280	325
OC3	He	480	532
OC4	He	580	630
EC1	2% O2/98% He	580	630
EC2	2% O2/98% He	740	786
EC3	2% O2/98% He	840	884

FIG. 1 (a) The sample analysis configuration and (b) the temperature calibration configuration of a Sunset Laboratory Carbon Aerosol Analysis Lab Instrument. The temperature calibration apparatus consists of a modified quartz boat handle and quartz cap, which enables a thermocouple to be placed at the filter sample while maintaining the functionality of the original components. Details of the modification are labeled in blue in Figure 1b.

TABLE 2 Filter temperatures achieved using a calibration based on Tempilaq° G data and measured at the filter by an external thermocouple probe. Measurements performed on a DRI Model 2001 Analyzer

IMPROVE_A Carbon	TSETPOINT (°C) from calibration	IMPROVE_A Target filter	TFILTER measured with the
fraction	with Tempilaq° G	temperature (°C)	temperature probe (°C)	% Difference ^1
OC1	122	140	120.4	14.0
OC2	261	280	279.0	0.3
OC3	459	480	480.3	−0.1
OC4	588	580	580.4	−0.1
EC1	588	580	582.6	−0.4
EC2	717	740	744.9	−0.7
EC3	816	840	844.4	−0.5

FIG. 2 Temperature calibration data for the UCD Sunset Instrument. The regression parameters are listed in Table 3.

TABLE 3 Linear calibration constants (with ±95% confidence intervals) for Sunset Instruments at UCD, ASU, and RTI

	Slope ^1 , m	Intercept ^1 , b	R ^2
UCD ^2	1.02 ± 0.03	−62.9 ± 15.6	0.998
ASU ^2	0.97 ± 0.01	−22.1 ± 8.8	0.999
RTI – 1 ^3	1.02 ± 0.09	−64.6 ± 56.5	0.996
RTI – 2 ^3	0.97 ± 0.06	−65.8 ± 40.9	0.998

FIG. 3 Mean concentration and standard deviation of (a) Total Carbon (TC), (b) Organic Carbon (OC), and (c) Elemental Carbon (EC) for samples analyzed with IMPROVE_A target filter temperatures at the sample oven and IMPROVE_A target filter temperatures at the filter. T_SETPOINT values used to obtain IMPROVE_A temperatures at the filter are given in Table 1. TC (p = 0.17), OC (p = 0.05) and EC concentrations (p = 0.06) are not significantly different from each other.

FIG. 4 Mean concentration and standard deviation of (a) OC2, (b) OC3, (c) OP, and (d) EC2 for filters analyzed with IMPROVE_A target filter temperatures at the sample oven and IMPROVE_A target filter temperatures at the filter. T_SETPOINT values used to obtain IMPROVE_A temperatures at the filter are given in Table 1. OC2 (p < 0.01), OC3 (p < 0.01), OP (p = 0.01), and EC2 (p < 0.01) are statistically different under the two temperature profiles.