Preservation of solid mercuric dithizonate samples with polyvinyl chloride for determination of mercury(II) in environmental waters by photochromism-induced photoacoustic spectrometry

A novel sample preparation technique has been developed to preserve solid mercuric dithizonate [Hg(HDz)2] in a matrix of polyvinyl chloride (PVC) for analysis by photochromism-induced photoacoustic spectrometry (PCPAS). This technique, which begins with the extraction of Hg2+ from water with dithizone, allows for the determination of Hg2+ in environmental samples. Inclusion of Hg(HDz)2 within the polymer matrix enhances the PCPAS signal amplitude over that from the bare Hg(HDz)2 film by almost sixfold. The standard calibration graph of PCPAS signal amplitude as a function of Hg2+ concentration is linear in the concentration range of 5-100 μg/ml. A lower detection limit can be achieved by using a laser of higher power tuned to a wavelength closer to the maximum absorptivity of the excited Hg(HDz)2 complex. A study, conducted to monitor the change in PCPAS signal amplitude obtained for the same sample over an extended storage period of 19 days, demonstrates that the PVC protects the integrity of the solid Hg(HDz)2 sample. Hence, it is potentially feasible to collect environmental samples from a remote area for analysis at a later date

Surface plasmon resonance sensors using molecularly imprinted polymers for sorbent assay of theophylline, caffeine, and xanthine

A sensory system based on the optical phenomenon of surface plasmon resonance (SPR), which employs either photothermal deflection spectroscopy (PDS) or a photodiode array (PDA) for detection, was developed to use molecularly imprinted (MI) polymethacrylic acid -ethylene glycol dimethacrylates (PMAA-EDMA) as the sensing element. The MI polymers were first processed by Soxhlet extraction to remove the print molecules (theophylline, caffeine, and xanthine), yielding the specific anti-polymers. Each anti-polymer was layered over a silver film to serve as the analysis surface for the molecularly imprinted sorbent assay (MIA) of one target drugs. This surface was exposed for 60 min to an aqueous standard drug solution, dried in air, and the uptake of the print molecule into the anti- polymer was monitored by shifts in the SPR angle θ(r) (and hence the SPR- PDS signal measured at constant θ). The linear dynamic range of the MIA was found to extend up to 6 mg/mL, with a concentration detection limit estimated at 0.4 mg/mL for theophylline in aqueous solution. A cross-reactivity study of the anti-theophylline and anti-caffein