ICP Analysis
Trace Elements in Sediments and Soils
ICP-OES Methods The ICP spectrometer is calibrated with five calibration standards (Table 1) and a blank (20% HNO3) each time it is used to measure the trace elements present in the digested soil samples. The standards are made from the initial solutions found in Table A2. The standards are made in Pyrex glass volumetric flasks of various sizes using ~6 MegaOhm distilled water. Volumes are measured using Fisherbrand Finnipipettes of 2-10mL, 1-5mL, and 100-1000?L sizes and Finntip 10mL and 5 mL and Fisherbrand 101-1000 ?L pipette tips. Standards are stored in Nalgene bottles and used within 10 days of preparation. The samples are analyzed by ICP-OES on a Spectro Ciros CCD machine connected to a Hewlett Packard computer running Smart Analyzer Ciros CCD software. This ICP spectrometer runs using Argon plasma.
A summary of the trace elemental concentrations for all of the SOILS standards used to calibrate the ICP-OES prior to processing each batch. All of the solutions contain 20% Nitric Acid.
Safety Warning: Nitric acid poses a hazard to skin, eyes, and internal organs. For more information see www.fishersci.com/msds
| SOILS Blank | SOILS Stnd. 1 | SOILS Stnd. 2 | SOILS Stnd. 3 | SOILS Stnd. 4 | SOILS Stnd. 5 |
Element | conc. (ppm) | conc. (ppm) | conc. (ppm) | conc. (ppm) | conc. (ppm) | conc. (ppm) |
Al | 0 | 50 | 100 | 30 | 0 | 150 |
Ba | 0 | 3 | 6 | 2 | 10 | 0 |
Be | 0 | 0.1 | 0.05 | 0.02 | 0 | 0.25 |
Cd | 0 | 0.1 | 0.05 | 0.02 | 0 | 0.25 |
Co | 0 | 0.1 | 0.05 | 0.02 | 0 | 0.25 |
Cr | 0 | 0.2 | 0.1 | 0.5 | 0.4 | 0 |
Cu | 0 | 0.2 | 0.1 | 0.5 | 0.4 | 0 |
Fe | 0 | 150 | 50 | 100 | 200 | 0 |
Mn | 0 | 10 | 20 | 6 | 30 | 0 |
Mo | 0 | 0.1 | 0.05 | 0.02 | 0 | 0.25 |
Ni | 0 | 0.2 | 0.1 | 0.5 | 0.4 | 0 |
P | 0 | 3 | 6 | 2 | 10 | 0 |
Pb | 0 | 0.6 | 1 | 0.4 | 0 | 2 |
Zn | 0 | 3 | 1 | 1.5 | 0 | 5 |
A summary of the solutions used to prepare the SOILS calibration standards for the ICP spectrometer.
Element | Conc. (ug/mL) | Acid solution | Brand |
Al | 1000 +/- 3 | 2 % HNO3 | High Purity Standards |
Ba | 1000 | 5 % HNO3 | Specpure |
Be | 1000 | 5 % HNO3 | Specpure |
Cd | 1000 | 5 % HNO3 | Specpure |
Co | 1000 | 5 % HNO3 | Specpure |
Cr | 1005 | 1-4 % HCl | Aldrich |
Cu | 1000 +/- 3 | 2 % HNO# | Environmental Express |
Fe | 1000 | 5 % HNO3 | Specpure |
Mn | 1000 | 5 % HNO3 | Specpure |
Mo | 1000 |
| Spex CertiPrep |
Ni | 1000 | 5 % HNO3 | Specpure |
P | 1000 | 5 % HNO3 | Specpure |
Pb | 1000 | 5 %HNO3 | Specpure |
Zn | 999 | 1.1 % HNO3 | Aldrich |
ICP-OES Analyses After initializing the ICP spectrometer and a 30 minute warm-up period, the machine is calibrated with the five SOILS standards and the blank. The calibration curves are checked and updated. After the calibration, the machine is ready to process samples. During the measurement procedure, standards are measured at the beginning, middle, and end (or at appropriate intervals for large batches) to check the consistency of the measurements. If there appears to be significant change in the measured values of the standards’ trace elements, the instrument is recalibrated. The trace elemental compositions of each digested soil solution are measured three times by the spectrometer and an average and standard deviation are calculated, printed, and stored in a data file on the computer. The data are retrieved after the measurements have been completed and they are further reduced in an Excel spreadsheet.
