Hybrid microscale analytical methods for environmental analysis

The contamination of natural resources by human activity can have severe socio-economical impacts. Environmental analytical chemistry plays an essential role in the solving of these environmental problems. However, conventional environmental analytical procedures are generally lengthy and necessitate several steps. Hybrid microscale analytical techniques have been developed with the objective of minimizing the number of sample preparation steps, avoiding the use of organic solvents and reducing the size of the samples required for an analysis as well as increasing the speed of analyses. An Inductively Heated – Electrothermal Vaporizer (IH-ETV) was coupled to an Inductively Coupled Plasma Mass Spectrometer (ICP-MS) to vaporize mercury from single human hair strands without any prior sample preparation, such as the destruction of its matrix by digestion. The results were comparable to those obtained with a reference method. For samples requiring chromatographic separation, sample handling was minimized by direct coupling of the chromatographic procedure to an ICP-MS through Laser Ablation (LA). Cr3+ and Cr6+ were separated on silica gel High Performance Thin Layer Chromatography plates (HPTLC) using aqueous mobile phases. LA was used to volatilize the chromium species directly from thechromatographic stationary phase material for ICP-MS detection. This procedure allows for a rapid separation and quantification, and requires only 0.5 μL of sample. The same procedure was used to couple miniature Solid Phase Extraction (SPE) columns implemented on centrifugal microfluidic discs to an ICP-MS to determine pre-concentrated metal chelates from drinking water. The miniature SPE devices require only 1 – 600 μL samples, allowing a reduction of three to four orders of magnitude in sample size compared to the conventional procedure, and the device requires no more than a simple motor to actuate fluid flow. The centrifugal microfluidic SPE discs can be used to perform up to eight extractions simultaneously and allow the easy storage of samples before transport to the laboratory for LA-ICPMS analysis. Finally, the centrifugal microfluidic SPE discs were modified to allow their coupling to absorption and fluorescence spectrometers. As well as the advantages listed above, this hyphenated system allows the in-situ screening of aquatic organic pollutants trapped on the SPE column directly in the field using simple and small light sources and detectors.