Study suggests that HPLC-ICP-MS is appropriate for determinations of large sample batches, while GC-ICP-MS is a better tool for monitoring studies at the ultratrace level
Agilent has announced the results of a study comparing two techniques for analysing organotins - toxic compounds found in seawater and marine sediments as well as in numerous consumer products.
In recent years, analysis has focused on matrices where the presence of organotin has human health implications, such as in seafood, in PVC pipes used for drinking water distribution, and in human blood samples.
One technique used gas chromatography (GC) with inductively coupled plasma mass spectrometry (ICP-MS), a highly sensitive detector yielding detection limits in the picogram to nanogram range.
This detector also enables calibration by isotope dilution mass spectrometry (IDMS), reducing measurement uncertainties and increasing precision compared with external calibration methods.
The second technique used is high-performance liquid chromatography (HPLC) with ICP-MS.
Organotin analysis has traditionally been performed by GC and HPLC coupled to a variety of other detectors.
Gas chromatography with ICP-MS offers the advantage of analysing 10 to 12 organotin compounds in a single analysis after derivatisation.
However, derivatisation is time-consuming and yields may vary, depending on the organotin species.
In contrast, HPLC does not require derivatisation, which eliminates one source of uncertainty in final results and reduces total analysis time by 40 percent.
Moreover, because there is no derivatisation, the cost per sample is about half that of GC sample preparation.
On the down side, HPLC-ICP-MS can measure only five to six organotin compounds in a single run.
In the study, there was no statistical difference in the results obtained.
However, by adding additional gases in the GC-ICP-MS analyses, Agilent chemists increased measured peak area.
Adding 5% oxygen, for example, produced a nine-fold increase in peak area for the organotins DBT and MPhT and a 12-fold increase for MBT.
These results suggest that HPLC-ICP-MS is appropriate for faster, more economical determinations of large sample batches, while the greater number of analytes separated in one run and the potential for superior sensitivity make GC-ICP-MS a better tool for monitoring studies at the ultratrace level.
