Table 2 – Between-day precision for 10 samples
Between-day precision/process stability (%) Sample 1
Sample 2 Sample 3 Sample 4 Sample 5 Sample 6 Sample 7 Sample 8 Sample 9 Sample 10
99.76 ± 5.73 102.16 ± 1.86 98.66 ± 5.21 97.34 ± 2.34 97.13 ± 4.93 95.48 ± 4.61 94.07 ± 1.16 96.57 ± 1.62 95.53 ± 1.41 95.13 ± 2.47
reasons are that foam developed in the waste reservoir during sample processing, i.e., foam rose up from the waste reservoir to the columns, negatively aff ecting the adsorbate and the results. Consequently, sample incubation time in the columns was reduced from 7 seconds (with the 24-column adapter plate) to 3 seconds (with the 96-deep-well plate) to minimize foam development.
The recovery rate for the automated process was in a slightly lower range (24-column adapter plate: 88.60–108.10%, MV: 98.35%; 96-well plate: 72.88–95.20%, MV: 84.04%) compared to the manual procedure (90.10–104.26%, MV: 97.18%). The within-day precision for the manual SPE was 96.04 ± 4.30% for all fi ve days. In contrast, the automated process with the 24-column adapter plates achieved a higher within-day precision (98.04 ± 5.52%) and the 96-deep-well plate a lower within-day preci- sion (78.16 ± 6.06 µg/L). The presence of foam may have been a factor in the lower within-day precision with the 96-deep-well plates. Further, the shorter incubation time of the sample within the column infl uenced the adsorption process. In the automated procedure, a maximum of two plates (24 or 96 samples) can be processed in one day because of the time- consuming sample preparation, decontamination, liquid handling and detection method. Therefore, optimization of the automated SPE can be achieved by 1) using a larger waste reservoir and removing the foam and 2) curtailing the liquid handling process and the quantifi cation method.
Discussion The fi ndings presented here demonstrate the success of the automated
SPE with the positive pressure unit. The results show that the automated process with the 24-column adapter and 96-well plate are in an accept- able range and can replace the manual sample preparation process. Automated and semiautomated SPE methods using vacuum for sample processing6,10
are suitable for routine use. In Ref. 11, Chen et al. presented
a fully automated solid-phase extraction method for drug screening pur- poses and compared automated to manually generated results.
In the current study, automated SPE was based on positive pressure and manual SPE was based on vacuum. Consistent with this, Chen et al. ob- tained better reproducibility, with the automated process.11
Carver Automatic Hydraulic Presses
Faster, more pre cise pro gram ma ble con trol!
From the leader in laboratory press es, 15 to 100 ton clamp ca pac i ties, in te gral electrically op er at ed hydraulic pow er unit, safety shields, heated plat ens (optional). Send for catalog.
ISO 9001:2008 Certified
Carver, Inc., 1569 Morris St., P.O. Box 544 Wabash IN 46992-0544 USA
Tel: 260-563-7577 • Fax: 260-563-7625
www.carverpress.com
AMERICAN LABORATORY • 31 • MARCH 2015
The World Leader in Laboratory Presses For Over 100 Years
Page 1 |
Page 2 |
Page 3 |
Page 4 |
Page 5 |
Page 6 |
Page 7 |
Page 8 |
Page 9 |
Page 10 |
Page 11 |
Page 12 |
Page 13 |
Page 14 |
Page 15 |
Page 16 |
Page 17 |
Page 18 |
Page 19 |
Page 20 |
Page 21 |
Page 22 |
Page 23 |
Page 24 |
Page 25 |
Page 26 |
Page 27 |
Page 28 |
Page 29 |
Page 30 |
Page 31 |
Page 32 |
Page 33 |
Page 34 |
Page 35 |
Page 36 |
Page 37 |
Page 38 |
Page 39 |
Page 40 |
Page 41 |
Page 42 |
Page 43 |
Page 44 |
Page 45 |
Page 46 |
Page 47 |
Page 48 |
Page 49 |
Page 50 |
Page 51 |
Page 52 |
Page 53 |
Page 54 |
Page 55 |
Page 56