Digestion Method

Digestion solution: 10% HF/50% HNO3 (v/v) “higher concentrations of HNO3 have no effect on particulate digestion effectiveness, but can increase filter blank”.

2ml should be sufficient for a 47mm filter.

0.2ml HF (Con) +1.0 ml HNO3 +0.8ml DI Water= 2ml

“Close cap tightly and place on Teflon hotplate 130 degC for 4 hours” – we don’t have screw lids for these so reflux for longer. It should be apparent when all the material has dissolved.After cooling collect all drops at bottom of vial by tapping. Dry down the solution and carefully watch for ~ 5ul of solution remaining, i.e. not burnt and crispy. Add 100ul conc HNO3 and dry down again to ~5ul droplet (to remove any residual HF).

CRM 50mg GBW07315 Anything organic/more appropriate in the CRM cupboard Gangi?

Blanks(we have 2 or 3 blanks already in the samples).

Sample VolumeTake up samples by washing down the sides of the vials in 14ml 5% HNO3 (leave over night to dissolve all solutes) and decant into pre acid washed 15ml sample tubes with stoppers.

Analytes.

Order of importance: Fe (!) Rare Earth Elements, Al, Transition metals + the usual elements.Based on a rough estimate of Fe concentration in loch Etive particulate material from Tim’s REES program, the conc of a 14ml solution will be between 0 and 3000ppb (mean ~600ppb).

ICPMS analysis 13ml taken from sample – In and Rh added (dilution factor applied to final conc calc) Direct measurement of solution – 0 – 100ppb with calibrator concentrations increased at the low end 0-10ppb (upper standards to be removed where appropriate off line) using 5% matrix match standards. Target analyte any low conc Fe and REE. This will also give us rough Fe concs for dilution calculations (step 2 below). Monitor counts on Fe57 normal mode and Fe56 collision cell to remove ArO interference. Tune collision cell on Fe56 for maximum stability vs intensity. Tune out the nitric blank Fe56 signal (mostly ArO) by increasing collision cell gas. REE measured in standard mode.If the Fe signal from samples is massive do a second run of these samples in ‘high resolution mode’ to reduce the number of counts and get a better idea of conc for analysis 2.Potential problems – High salt content on filters. If the samples were not DI rinsed may need to think about doing this prior to digestion?

ICPMS analysis 2. Most important.

Take <1 ml and as appropriate dilute to get ~50ppb Fe in final sample (~3ml) for analysis. Adding internal standards may not be possible if all the vials have wildly different volumes. We will see it may be possible depending on the concentration range. Suggest adding more check standards (with In and Rh) to sample run which will monitor instrument drift, but not matrix effects. Take three samples with high conc Fe and make a second sample and spike with In and Rh to monitor internal standard recovery.

ICPMS analysis 3. As appropriate.Subsequent dilution to obtain any other analytes within the 100 ppb range

ICPOES~10ml sample will remain for direct ICPOES analysis.Fe and Al most important (but do the usual run).Hopefully a few samples will have high enough Fe that we can compare OES Fe with MS Fe (that has an isobaric interference).The Al will give us a lithogenic signal if high enough conc.