Since the discovery of Quantum Dots (QDs) by Alexey I. Ekimov in 1981, the interest of researchers in that particular type of nanomaterials (NMs) with unique optical and electrical properties has been increasing year by year. Thus, since 2009, the number of scientific articles published on this topic has not been less than a thousand a year. The increasing use of QDs due to their biomedical, pharmaceutical, biological, photovoltaics or computing applications, as well as many other high-tech uses such as for displays and solid-state lighting (SSL), has given rise to a considerable number of studies about its potential toxicity. However, there are a really low number of reported studies on the detection and quantification of QDs, and these include ICP–MS and electrochemical analysis, which are the most common quantification techniques employed for this purpose. The knowledge of chemical phenomena occurring on the surface of QDs is crucial for understanding the interactions of QDs with species dissolved in the dispersion medium, while it paves the way for a widespread use of chemosensors to facilitate its detection. Keeping in mind both human health and environmental risks of QDs as well as the scarcity of analytical techniques and methodological approaches for their detection, the adaptation of existing techniques and methods used with other NMs appears necessary. In order to provide a multidisciplinary perspective on QD detection, this review focused on three interrelated key aspects of QDs: properties, surface chemistry and detection.

A method for the determination of lead in slurries of marine sediment using palladium–magnesium nitrate as a chemical modifier has been optimized. To stabilize the marine sediment slurry, different thickening agents were studied. The grinding time and the particle size were also studied. To achieve complete pyrolysis of the slurry sample, two charring steps were used: the first one at a low temperature, 480 °C, and the second at 900 °C. The precision of the method was studied as within-run and within-batch precision; the relative standard deviations obtained in both cases were less than 3%. The relative standard deviation for the repeatability of the over-all procedure was 5.0%. The accuracy of the method was studied using a Certified Reference Material PACS-1 (Marine Sediment) from the National Research Council of Canada, which has a certified lead content of 404 ± 20 mg kg^–1; the result obtained was 418 ± 11 mg kg^–1. The detection limit for lead was 0.22 µg l^–1. Calibrations using aqueous standards and the reference material were compared. This method has been applied to the determination of lead in marine sediment samples from the Galicia Coast and the results were compared with a sample digestion method using nitric and hydrochloric acids in a high pressure poly(tetrafluoroethylene) bomb and microwave energy. No significant differences were found between the two procedures.

A method for the determination of lead in mussel slurries by atomic absorption spectrometry with electrothermal atomization using Pd–Mg(NO₃)₂ as a chemical modifier is proposed. The drying, ashing and atomization temperatures were optimized. Calibration and standard additions graphs, sensitivity, precision, accuracy and the effects of different slurry stabilization agents were also studied. The method was applied to the determination of lead in mussel samples from the Galician coast and the results obtained were compared with those achieved by means of a wet digestion procedure.

To complete these microwave distillation studies, a method for iodide determination in milk-type samples is proposed. The iodide contained in the sample is oxidized to iodine, which is distilled by means of microwave energy and reduced back to iodide. This iodide is combined with Hg(II) and 2,2′-dipyridyl to give an ion pair, which is selectively extracted into IBMK. Mercury is determined in the extract by ETAAS in order to determine iodide. The yield of the distillation process (100%) was evaluated using the Sandell–Kolthoff reaction. In addition, for the solvent extraction, no buffer was needed; 3/5 was the best phase ratio (organic/aqueous); 30 s was the shaking time and the extracts were stable for 24 h, at least. The yield of the extraction procedure (studied also using the Sandell–Kolthoff reaction) was 87.5 and 87.1%, for standards and samples, respectively. Regarding the ETAAS measurements, the ashing temperature selected for both samples and standards was 150 °C; 800 and 1000 °C were the atomization temperatures chosen for samples and standards, respectively. Palladium in IBMK was the chemical modifier at a concentration of 3.0 µg ml⁻¹, both for samples and standards. The sensitivity was 3.50 × 10⁻³ l µg⁻¹ (standard additions); the LOD and LOQ were 0.2 and 0.6 µg ml⁻¹, referred to sample; the mean characteristic mass within the linear range of concentrations (0–17.5 µg l⁻¹) was 27.3 pg; the mean analytical recovery within that range was 97.5% for a liquid whole milk sample and 100.6% for a CRM, which also gave results within certification. The method was applied to liquid whole milk, milk powder and infant formulae samples.