SPR-IDA (Suspended Particulate Reagent – Iminodiacetate) is a sample preparation material for preconcentration of trace elements and reduction of high alkali metal (e.g. Na) sample matrix levels. The reagent consists of 10 micron diameter polymer beads that have been chemically derivatized with the iminodiacetate chelating agent. Small aliquots of the reagent can be added via a batch mode to a sample and separated with bound metals by gravity or centrifugation.
Seawater Example: The determination of trace elements in liquid samples such as seawater presents a number of challenges for inductively coupled plasma mass spectrometry (ICP-MS). The high dissolved solids content (approx. 3.5%) of seawater can suppress analyte signal, cause interelement interferences and clog the interface sampler and skimmer cones.
The seawater sample can be diluted, but at the expense of detectability, as some elements of interest are in the 5 to 50 ppt (ng/L) range. An alternative is a sample preparation technique that can selectively preconcentrate trace elements of interest while having much less affinity for major matrix components such as Na, K, Ca and Mg.
A chelating polymer resin called SPR-IDA (Suspended Particulate Reagent - Iminodiacetate) can be used for preconcentration/matrix elimination of seawater. The reagent consists of 10 micron diameter polymer beads derivatized with the chelating agent iminodiacetate. The beads are supplied as a 10% suspension in deionized water, and can be easily pipetted into a sample. The resin suspension aliquot is typically 0.1ml per 15mL of seawater sample.
Batch Mode Sample Preparation: After an aliquot of the resin suspension is added to the sample, the pH of the sample is adjusted to 8 and the resin is separated by gravity or centrifugation. The supernatant liquid is removed and the resin is washed to remove more of the remaining unbound sample matrix. Nitric acid is then added to the resin to release the bound analytes and the acid extract analyzed via conventional nebulization by ICP-MS. Important elements that are chelated by SPR-IDA include Al, Cd, Co, Fe, Mn, Ni, Pb, U, and Zn.
Iminodiacetate (IDA) on SPR Bead
Off-Line Sample Preparation: Sample preparation can be done offline, saving valuable ICP-MS running time (Ar gas and electricity) that is lost during traditional column loading, washing, and elution steps.
Avoid Sample Memory Effects: The SPR-IDA bead aliquot is used only once, avoiding sample memory effects from incomplete column elution.
Simple and Economical: No additional complex, costly liquid handling hardware (e.g. injection and switching valves) are needed. Typically 15 to 50 mL test vials (ex. polypropylene) are used for sample preparation with bead separation by gravity.