Mercury sensors

TRANSDUCERS FOR MERCURY SENSORS BASED ON THIN GOLD LAYERS... 

Fig. 12.3. Mercury sensor based on surface acoustic waves (SAW) with shear-horizontal acoustic plate mode. This approach was tested in Ref. [8].

The main disadvantage of mercury sensors based on bare gold layers is their poor selectivity. This is illustrated in Fig. 12.6 an incubation at 100% humidity (Fig. 12.6a), with saturated vapour of sulphuric acid (Fig. 12.6), volatile sulphides or thiols (10 pg/1 of 1-butanethiol vapour, Fig. 12.6c), or halogens (10 pg/1 of iodine vapour, Fig. 12.6d), results in conductivity changes of the same magnitude as an incubation with 10-20 ng/1 of mercury vapour. This interference with widely spread substances is a serious problem in applications of such sensors for real probes and makes necessary a pre-treatment of probes. 

Fig. 12.6. Influence of typical interferents on mercury sensors based on changes of lateral resistance of thin gold layers. Sensors bare gold layers (open symbols), gold layers coated by self-assembled monolayers of 1-hex-adecanethiol (filled symbols). Interferents 100% humidity (a), saturated vapour of sulphuric acid (b), 10 pg/1 of 1-butanethiol (c), 10 pg/1 of iodine vapour (d), Thickness of gold layers 42 nm [25].

Mercury sensors based on thin gold layers require regular calibrations. In ideal cases, the calibration should be performed before each measurement. Therefore, a calibration technique should be compatible with design and concept of the mercury vapour sensor. Several approaches were suggested. 

Trace level analysis 45 Training of the ANN e319 Trandolapril 62 Transducer materials 479 for mercury sensors 238 Transient response 746 Transparent substrates (SOI) 100 Triclosan 520... 

The amalgamated gold electrode should be used for calibration of the mercury sensors within 10 min or stored at —20°C up to 4 days. The longer storage time may be possible but was not tested. 

On one side, application of combinatorial chemistry to sensor discovery could be traced back to very early time, as the receptor discovery has been recognized as an important applicable field for combinatorial chemistry as in medicinal chemistry.15 In this approach, combinatorial techniques are utilized to compensate receptor design, and the fluorophore can be either incorporated into the receptor synthesis or remain independent for displacement assays. Diversity of the receptor part helps for probing the interactions between the receptor and target analyte, thus this approach can greatly facilitate the target-oriented approach in the situations that the receptor is unknown or not easily designed.16 One recent example of mercury sensor development clearly demonstrated the power of this approach (Fig. 17.4).17... 

Use of nanohybrid materials as electrochemical transducers for mercury sensors. Sens. Actuators, B, 165 (1), 143-150. 

M. Rex, F. E. Hernandez and A. D. Campiglia, Pushing the limits of mercury sensors with gold nanorods. Analytical Chemistry, 78(2), 445-451 (2006). 

Tuning the sensitivity of a foldamer-based mercury sensor by its folding... 

Several special forms of electromagnetic flow meters have been developed. A d-c field version is used for Hquid metals such as sodium or mercury. Pitot and probe versions provide low cost measurements within large conduits. Another design combines a level sensor and an electromagnetic meter to provide an indication of flow within partially full conduits such as sewer lines. 

Mercury layers plated onto the surface of analytical electrodes serve as Hquid metal coatings. These function as analytical sensors (qv) because sodium and other metals can be electroplated into the amalgam, then deplated and measured (see Electro analytical techniques). This is one of the few ways that sodium, potassium, calcium, and other active metals can be electroplated from aqueous solution. In one modification of this technique, a Hquid sample can be purified of trace metals by extended electrolysis in the presence of a mercury coating (35). 

Calculation yields that in these experiments the stationary concentration of radicals [ 4] for the maximum intensity of light of a mercury lamp SVDSh-500 was no more than 10 radicals/cm, the stationary conductivity of a ZnO film at 300 C changing by 300 to 400% compared to its initial pre-adsorption value. Thus, in accordance with the above formula (3.21), concentrations of radicals equal to 10 -10 radicals/cm may be detected by means of semiconductor sensors which is 7 magnitudes lower than existing methods would allow. 

Fig. 4.18. Kinetics of variation of electric conductivity of the ZnO sensor on Si02 plate activated with Pd after leaking-in hydrogen 1 - without illuminating the plate 2 - during illumination with light at 313 nm from a mercury lamp with an additional water filter absorbing IR radiation. Stars show the beginning of sharp rise of electric conductivity.

Fluorescent lamp coatings, ethylene oxide polymers in, 10 688-689 Fluorescent lamps, mercury in, 16 41 Fluorescent lighting phosphors, cerium application, 5 688-689 Fluorescent photo-induced electron transfer (PET) sensor, 24 54 Fluorescent pigments, for inks, 14 318 Fluorescent probes, 11 150 16 388 modified-base oligonucleotides as, 17 633-634... 

Temperature measurement was historically done with a mercury thermometer. Modern instruments have electronic temperature sensors that can be coupled with digital temperature readouts. Digital temperature monitoring also allows the operator to record the observed melting point with the press of a keypad button. Data can be stored within the instrument or transmitted to a computer or laboratory information management system (LIMS). 

Liu CW, Huang CC, Chang HT et al (2009) Highly selective DNA-based sensor for lead(II) and mercury(II) ions. Anal Chem 81 2383-2387... 

Huang CC, Chang HT (2006) Selective gold-nanoparticle-based tum-on fluorescent sensors for detection of mercury(II) in aqueous solution. Anal Chem 78 8332-8338... 

Zheng AF, Chen JL, Wu GN et al (2009) Optimization of a sensitive method for the switch-on determination of mercury(II) in waters using rhodamine B capped gold nanoparticles as a fluorescence sensor. Microchim Acta 164 17-27... 

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