| 
   
  |  | MET | PIO | GLB | GMP |  
  | Systems | Conc. (µgmL-1) | Intra-day variation | Inter-day variation | Intra-day variation | Inter-day variation | Intra-day variation | Inter-day variation | Intra-day variation | Inter-day variation |  
  | LC 10 | 25 | 0.171 | 0.191 | 0.322 | 0.431 | 0.026 | 0.122 | 0.952 | 0.779 |  
  | 12.5 | 1.33 | 0.419 | 0.935 | 0.382 | 0.597 | 0.248 | 0.906 | 0.906 |  
  | 6.25 | 0.525 | 0.189 | 0.377 | 0.425 | 0.62 | 0.107 | 0.62 | 0.737 |  
  | 3.125 | 0.403 | 0.071 | 0.544 | 0.723 | 0.7 | 0.111 | 0.596 | 0.753 |  
  | 1.5625 | 0.381 | 0.18 | 0.99 | 0.317 | 0.755 | 0.214 | 0.885 | 0.253 |  
  | LC 20 | 25 | 0.175 | 0.124 | 0.174 | 0.269 | 0.193 | 0.131 | 0.529 | 0.357 |  
  | 12.5 | 0.291 | 0.397 | 0.17 | 0.866 | 0.367 | 0.208 | 0.301 | 0.307 |  
  | 6.25 | 0.182 | 0.769 | 0.439 | 0.868 | 0.268 | 0.915 | 0.563 | 0.944 |  
  | 3.125 | 0.516 | 0.854 | 1.05 | 0.086 | 0.382 | 0.355 | 0.013 | 0.205 |  
  | 1.5625 | 0.258 | 0.759 | 0.963 | 0.447 | 0.926 | 0.649 | 0.144 | 0.282 |  |