Table 2. Recovery and Matrix Effect for DTG DBMS following liquid-liquid extraction with and without addition of EDTA, and the Internal Standard spiked in the extraction solution or directly onto the DBMS filter paper.
| Method | Nominal QC Concentration (ng/mL) | %ME (SD) | %RE (SD) | %PE (SD) | %Analysis RE (SD) |
|---|---|---|---|---|---|
| (B/A*100) | (C/B*100) | (C/A*100) | (C2/B2*100) | ||
| DBMS extracted with IS added to the extraction solvent | 30 (LQC) | 109.48 (7.80) | 35.816 (4.15) | 39.21 (5.99) | 37.38 (7.94) |
| 455 (MQC) | 129.63 (7.55) | 50.53 (1.53) | 65.51 (3.30) | 55.66 (7.085) | |
| 3700 (HQC) | 142.95 (10.32) | 39.41 (2.69) | 56.33 (4.01) | 41.33 (3.41) | |
| Overall Mean (%CV) | 127.35 (13.24) | 41.92 (7.96) | 53.68 (13.35) | 42.07 (25.67) | |
| DBMS pre-soaked with EDTA, and IS added to the extraction solvent | 30 (LQC) | 90.37 (3.07) | 102.23 (9.56) | 92.38 (11.50) | 98.64 (8.59) |
| 455 (MQC) | 74.27 (7.49) | 104.81 (8.46) | 77.842 (6.48) | 64.74 (5.63) | |
| 3700 (HQC) | 85.29 (6.93) | 99.26 (11.97) | 84.67 (11.49) | 71.15 (9.73) | |
| Overall Mean (%CV) | 83.31 (8.12) | 102.10 (11.92) | 84.97 (13.58) | 78.18 (23.03) | |
| DBMS pre-soaked with EDTA, and IS spotted directly onto the spot | 30 (LQC) | 97.10 (4.02) | 92.94 (10.27) | 90.24 (12.11) | 102.10 (12.87) |
| 455 (MQC) | 88.46 (8.62) | 114.82 (14.33) | 101.56 (11.08) | 86.84 (10.58) | |
| 3700 (HQC) | 104.93 (12.03) | 107.47 (15.18) | 112.77 (7.45) | 78.15 (10.12) | |
| Overall Mean (%CV) | 96.83 (8.18) | 105.07 (11.23) | 101.52 (11.09) | 89.03 (13.62) | |
A=Mean peak area response of analyte in mobile phase; B= Mean peak area response of analyte spiked after extraction of matrix (Spiked post extraction of blank DBMS); C= Mean peak area response of analyte spiked prior to extraction (spiked pre-extraction); %ME= Matrix effect, defined as ratio of mean peak area of analyte spiked post extraction (B) to mean peak area of analyte in mobile phase (A) X 100; %RE= Extraction yield, derived by dividing the mean peak area response of analyte spiked pre-extraction (C) with mean peak area response of analyte spiked post extraction (B) and multiplying by 100; %PE= Process efficiency calculated by dividing mean peak area response of analyte spiked pre-extraction (C) by mean peak area of analyte in mobile phase (A) and multiplying by 100; B2 is defined as response ratio of analyte spiked post extraction and internal standard; C2 is the response ratio of analyte spiked pre-extraction and internal standard; %Analysis RE calculated by dividing the mean response ratio of analyte spiked pre-extraction (C2) to mean response ratio of analyte spiked post extraction (B2), multiply by 100;