Table 2 Summary of method validation results

System suitability

RSD (%) for peak area response (n = 6)

0.97%

1.62%

1.94%

Specificity

Interference from blank

No interference

No interference

No interference

Sensitivity

Concentration

LOD–2.5 ppm

LOQ–8.0 ppm

LOD–3.5 ppm

LOQ–11.0 ppm

LOD–4.0 ppm

LOQ–12.5 ppm

RSD for six replicate injections of LOQ solution should be ≤ 15.0%

4.13%

4.21%

3.29%

Linearity

Range

2.5–100 ppm

3.5–100 ppm

4.0–100 ppm

Calibration equation

y = 130.97x + 178.5

y = 123.16x − 41.816

y = 69.578x−36.595

R²

0.9992

0.9969

0.9997

Accuracy

Average recovery (n = 3) from the spiked samples performed at 3 levels—LOQ–150%; RSD should be ≤ 10.0%

LOQ–96.9%; 1.28%

100%–100.1%; 1.88%

150%–100.5%; 0.97%

LOQ–98.9%; 1.98%

100%–99.8%; 2.08%

150%–99.0%; 1.11%

LOQ–99.3%; 3.57%

100%–98.8%; 1.36%

150%–97.7%; 1.35%

Precision

(analyst 1)

RSD (%) for six preparations at 100% level should be ≤ 10.0%

2.37%

3.15%

2.94%

Intermediate precision

(analyst 2)

RSD (%) for six preparations at 100% level should be ≤ 10.0%

2.96%

3.42%

3.83%

Solution stability

Standard and 100% spiked solution stored at ambient laboratory conditions (25 ± 5 °C) and refrigerated conditions

(2–8 °C) were studied for 48 h

Stable for 48 h

Stable for 48 h

Stable for 48 h

Robustness

RSD (%) for peak area response (n = 6) with 0.7 mL/min flow rate

%Recovery (n = 3) for 100% spiked solution

1.28%

100.1%

1.94%

98.7%

1.82%

96.8

RSD (%) for peak area response (n = 6) with 1.0 mL/min flow rate

%Recovery (n = 3) for 100% spiked solution

4.1%

96.5%

3.4%

96.8%

3.5%

95.2%

RSD (%) for peak area response (n = 6) with 12 V cone voltage

%Recovery (n = 3) for 100% spiked solution

1.34%

99.6%

1.9%

97.7%

2.2%

97.4%

RSD (%) for peak area response (n = 6) with 18 V cone voltage

%Recovery (n = 3) for 100% spiked solution

3.1%

95.3%

4.3%

94.7%

4.9%

93.8%