Table 3: Precision and accuracy in the analysis of QC samples and ECD in ECD Kit.

Day

Standard curve^{(1)}

Sulfur weight (%)^{(2)}

Recovery yield (%)

Dynamic range of sulfur (mg)

Linear least squares regression equation

Correlation coefficient ()

QC_{coal}

QC_{coal}

QC_{ECD}^{ (3)}

1

0.033 –0.104

Y = 1.615 × 10^{−6}X + 4.747 × 10^{−3}

0.9993

3.13 ± 0.07 (2.25%)

102.08 ± 2.29

—

1

0.031–0.105

Y = 1.623 × 10^{−6}X + 1.741 × 10^{−3}

0.9989

3.10 ± 0.02 (0.60%)

100.89 ± 0.60

—

2

0.034–0.107

Y = 1.634 × 10^{−6}X + 1.034 × 10^{−3}

0.9994

3.08 ± 0.04 (1.21%)

100.15 ± 1.21

—

3

0.033–0.106

Y = 1.576 × 10^{−6}X + 4.202 × 10^{−3}

0.9996

3.18

103.79

102.78 (QC-L)

100.00 (QC-M)

102.08 (QC-H)

^{(1)}Standard curves of coal. ^{(2)}Content percentage of sulfur in coal standard: 3.07% (w/w); data are expressed as average ± SD (%R.S.D.), . ^{(3)}Purity of ECD: 97.53%; compositions of ECD QC samples (QC-L, QC-M, and QC-H) were shown in Table 2.