ICP-MS Trace Elements

Trace Elements in Rocks, Soils, Sediments, and Vegetation by Inductively Coupled Plasma - Mass Spectrometry (ICP-MS)

Weigh 400mg sample into a clean 125ml wide-mouth polypropylene bottle (if samples are moist/wet, determine moisture content on separate aliquot and correct analytical data to dry basis)
Add 8ml of aqua regia (and 4ml of HF, if necessary); seal bottle tightly and place in drying oven at 100°C for 1hr (re-tighten caps every 10 minutes until they remain tight)
Cool, wash into 500ml volumetric flask and bring to volume with Nanopure water

Prepare instrument calibration standards at 1ug/L (equivalent to 1.25 ug/g in solid samples), matrix blanks, interference standards, and appropriate certified reference materials.
100uL of In internal standard (10mg/L) and 10ml of all samples, standards, and blanks are transferred to 15ml polyethylene autosampler tubes
Solutions are aspirated into a Micromass Platform ICP-MS with hexapole collision cell operating with the following parameters:

Instrumental Parameter	Setting
Torch forward power	1350 watts
Argon cooling gas flow	13.5 L/min
Argon intermediate gas flow	1.10 L/min
Nebulizer argon gas flow	0.8 – 1.0 mL/min
Collision cell helium flow	3.0 mL/min
Collision cell hydrogen flow	2.0 mL/min
Sample cone voltage	600 volts
Collision cell exit lens voltage	400 volts
Collision cell bias	-2.3
Ion energy	1.2 volts
Data collection period	1 min
Inter-sample delay	4 min

Appropriate analyte isotopes are monitored, along with 115In and 129Xe, both used as internal standards for matrix and background corrections
Integrated counts of blanks are subtracted from samples and standards, these counts are divided by internal standard counts, any interfering counts are subtracted, and an array of calibration and certified reference standards are used to calculate a least squares equation of the calibration line. This equation is used to quantify samples and standards. These calculated standard values are compared to certified values for an assessment of accuracy. Replicate analysis of samples/standards is used to assess precision, and replicate analysis of blanks is used to assess lower limits of detection.