Introduction
This study evaluated the effectiveness of the new NOVAWAVE microwave digestion system. The study entailed the digestion of Peach Leaves, a NIST Certified Reference Material, and demonstrated the effectiveness of the digestion and the analysis through an evaulation of metal recoveries and comparison to the certified values.
Sample Type
Dried Peach Leaves prepared by N.I.S.T. (CRM 1547; Certificate Date: January 22th, 1993.)
Supplies and Reagent
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1) NOVAWAVE Model SA* 2) Quartz 50ml Vessels * 3) Teflon® Caps and Safety Pressure Release Caps, pre-set release pressure at 30 bar (435 psi) * 4) PlasmaPURE HNO3 (70%), 10ml * 5) Analytical Balance, 4 Decimal Places, Mettler-Toledo 6) Spectroflame Modula FMD-07 ICP-OES, Spectro Analytical 7) Mini X-Flow Nebulizer * 8) 1.2mm Alumina Injector Torch * 9) Baffled Cyclonic Spray Chamber * 10) 10 ml Graduated Cylinder, Corning |
Sample Preparation Procedure
The samples were digested following EPA 3051 Method protocols. The CRM was mixed in its container. A portion was placed in a beaker and dried in a desiccator with CaSO4 (over 5 days) to ensure a stable mass. The samples were weighed on a 4 place analytical balance directly in the quartz vessels. After adding 10ml of HNO3, the samples were allowed to sit at room temperature for 5-10 minutes. They were then placed in the NOVAWAVE rack and digested following the instrument’s heating profile noted below. After cooling, samples were then normalized to 50 ml with DI H20.
Discussion
At the end of the digestion period and after cooling to room temperature, the vessels should be carefully vented in a fumehood. Some elements were not reported as their results were below their ICP-OES detection limits.
Recoveries are reported for 24 replicates.
NOVAWAVE Heating Program:
| Stage |
Ramp time |
Pressure (psi-limit) |
Temperature (oC) | Hold time (Minutes) |
| 1 | 10 | 435 | 180 | 10 |
Recoveries:
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Element symbol |
Wavelength (nm) | NOVAWAVE Results (ppm) |
Uncertainty (95% conf.) (ppm) |
Certified Value (ppm) | Dung sai (ppm) | Độ thu hồi (%) |
| Al | 396.15 | 252.00 | ±5 | 249.00 | ±8 | 101.20% |
| B | 249.77 | 29.00 | ±2 | 29.00 | ±2 | 100.00% |
| Ba | 455.4 | 125.00 | ±6 | 124.00 | ±4 | 100.80% |
| Ca | 422.67 | 15,629.00 | ±636 | 15,600.00 | ±200 | 100.20% |
| Fe | 259.94 | 219.00 | ±11 | 218.00 | ±14 | 100.50% |
| Mg | 277.98 | 4,335.00 | ±170 | 4,320.00 | ±80 | 100.30% |
| Mn | 257.61 | 97.00 | ±4 | 98.00 | ±3 | 99.00% |
| Sr | 407.77 | 54.00 | ±3 | 53.00 | ±4 | 101.90% |
| Zn | 213.86 | 18.00 | ±0.8 | 17.90 | ±0.4 | 100.60% |
Conclusions
The NOVAWAVE microwave digestion system produced good RSDs and excellent recoveries.
References
1) Certificate of Analysis NIST 1547
2) EPA 3051 Microwave Digestion Method
* Components manufactured by SCP SCIENCE.
