Background Arsenic is a naturally occurring element with varying species and levels of toxicity. Inorganic arsenic (e.g., arsenite (AsIII) and arsenate (AsV)) are toxic, while its metabolites (e.g., monomethylarsonic acid (MMA) and dimethylarsinic acid (DMA)) are less toxic). Symptoms of exposure can include headaches, confusion, diarrhea, and drowsiness. As these symptoms overlap with many other conditions, arsenic exposure can often be overlooked as a cause. Arsenic toxicity may be treated with chelation and/or electrolyte replacement therapy. However, treatment is not without risks and is unnecessary for exposure to organic (nontoxic) forms of arsenic. This makes screening and differentiation of arsenic important for clinical testing. Method An IC-ICP-MS method was developed using a Dionex 5000 with ion exchange chromatography for separation and iCAP Q for detection. Nontoxic species are arsenobetaine and arsenocholine, and toxic species are AsIII, DMA, MMA, and AsV. Results Precision, linearity, and specificity studies produced acceptable results. For accuracy, proficiency testing and method comparison samples were analyzed and produced acceptable results. Carryover studies demonstrated single species carryover from the diluter at levels of 500 µg/L, which can be avoided by analysis rules in the standard operating procedure. Limit of detection studies yielded a lower limit of quantitation of 1 µg/L per species. Conclusions Here, we present a rapid and reliable method for quantifying and differentiating toxic and nontoxic forms of arsenic to allow for swift and appropriate management of patients with exposure.

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Background Gadolinium-based contrast agents (GBCAs) have been used in magnetic resonance imaging for the past 30 years, where they have significantly improved the effectiveness of imaging studies. However, the increased usage of gadolinium in the medical community has also resulted in unexpected interferences in other laboratory assays. This has been particularly the case in clinical elemental analysis using inductively coupled plasma mass spectrometry (ICP-MS). Methods By conducting ICP-MS interference experiments, we describe how gadolinium interferes with elemental analysis by space charge effect, double charge effect and the creation of polyatomic interferences. Additionally, by reviewing more than a year of reference laboratory data from our laboratory information system, we determined the number of elemental tests cancelled due to gadolinium interference. Results Interference experiments show that gadolinium normally found in GBCAs can interfere with heavy metals, platinum and selenium analysis of biological fluids using ICP-MS. Within one year, our institution’s metals laboratory had to cancel 42 selenium serum tests and 19 heavy metal urine panels due to potential interference caused by gadolinium. Conclusions GBCAs will continue to be utilized in hospitals around the world. However, clinical laboratories should be wary of potential interferences caused by GBCAs. Relevant interferences include space charge effect, double charge interference, and the formation of polyatomic interferences caused by gadolinium. These interferences can negatively affect patient care by resulting in cancelled laboratory tests and causing patients to have blood redrawn and analysed at a later date leading to delays in their diagnosis/treatment.

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