Table 1.
Impact of SIL-IS concentration and isotope selection on assay accuracy. Accuracy (expressed as % average difference from the weighed-in concentration) of flucloxacillin controls with both SIL-IS isotopes, (m/z 458 → 160 and 460 → 160), at 0.7, 7 and 14 mg/L concentrations, analysed on Waters and Shimadzu systems, (n = 4).
| SIL-IS = 0.7 mg/L | SIL-IS = 14 mg/L | SIL-IS = 7 mg/L | ||||||||
|---|---|---|---|---|---|---|---|---|---|---|
| Waters Instrument | Shimadzu Instrument | Waters Instrument | Shimadzu Instrument | Waters Instrument | ||||||
| QC (mg/L) | Mean ± SD | % Diff | Mean ± SD | % Diff | Mean ± SD | % Diff | Mean ± SD | % Diff | Mean ± SD | % Diff |
| (m/z 458 → 160) | ||||||||||
| 2.5 | 3.11 ± 0.24 | 24.4 | 2.87 ± 0.26 | 14.7 | 2.65 ± 0.03 | 5.8 | 2.65 ± 0.04 | 6.0 | 2.55 ± 0.07 | 2.0 |
| 20 | 27.37 ± 0.83 | 36.9 | 26.70 ± 1.18 | 33.5 | 21.1 ± 0.48 | 5.4 | 20.8 ± 0.25 | 4.1 | 20.15 ± 0.57 | 0.8 |
| 200 | 141.57 ± 2.46 | −29.2 | 138.68 ± 4.79 | −30.7 | 194.7 ± 3.24 | −2.6 | 197.6 ± 2.82 | −1.2 | 169.3 ± 3.75 | −15.4 |
| (m/z 460 → 160) | ||||||||||
| 2.5 | 2.85 ± 0.22 | 13.9 | 2.74 ± 0.15 | 9.4 | 2.61 ± 0.07 | 4.3 | 2.67 ± 0.08 | 6.7 | 2.61 ± 0.07 | 4.3 |
| 20 | 19.90 ± 0.99 | −0.5 | 20.61 ± 1.50 | 3.0 | 20.3 ± 0.30 | 1.3 | 20.1 ± 0.18 | 0.3 | 19.53 ± 0.45 | −2.4 |
| 200 | 192.28 ± 9.44 | −3.9 | 197.79 ± 12.77 | −1.1 | 206.9 ± 6.57 | 3.4 | 206.2 ± 2.20 | 2.6 | 194.4 ± 5.10 | −2.8 |