C. Colapicchioni

New amperometric and potentiometric immunosensors for anti-human immunoglobulin G determinations

Two new electrochemical immunosensors for the determination of antibodies such as anti-human immunoglobulin G (anti-HIgG) were fabricated and characterized. The two immunosensors investigated made use of two different types of electrochemical transducer: an amperometric electrode for H2O2 determination and a gaseous diffusion potentiometric electrode for NH3 determination. The development of these immunosensors involved the immobilization of human immunoglobulin G (HIgG) on a polymeric membrane located on the electrode head. Furthermore, two different enzymes were used as markers, thus allowing two different anti-HIgG conjugates with urease and glucose oxidase, respectively, to be obtained. Two different polymeric membranes on which the HIgG were immobilized, namely ‘Pall-Biodyne’ and ‘Immobilon’, were also employed. A method for re-utilizing the membrane of the immunosensor in which the conjugate was immobilized was also optimized.

Organophosphorus pesticide (Paraoxon) analysis using solid state sensors

A comparison of two new solid-state biosensors for organophosphorus pesticide analysis is presented, both of which employ the inhibiting action of these toxic compounds versus the enzyme butyrylcholinesterase. The indicating sensor used was a graphite electrode, or a FET, coated with an ion-selective polymeric membrane sensitive to pH containing tridodecylamine as exchanger. The former was coupled to the enzyme butyrylcholinesterase immobilised on a functionalized nylon net, while the latter employed the same enzyme coated on the polymeric membrane by means of polyazetidine prepolymer. The responses of the two biosensors to the substrate, i.e. butyrylcholine (BuCh), and to the inhibitor, i.e. Paraoxon, one of the most common organophosphorus pesticides, were tested.

Sensitive membrane ISFETs for nitrate analysis in waters

Abstract We have fabricated and characterized two new nitrate-sensitive ISFET devices employing two different kinds of field-effect transistors (FETs), one supplied by Academia Sinica, Beijing (China), the other purchased from HEDCO Lab., Utah University (USA), and both based on a poly(vinyl chloride) (PVC)-sebacate membrane, containing tetradodecylammonium nitrate as exchanger. A comparison with a classical nitrate ISE fabricated using the same PVC-sebacate membrane and the same exchanger is also reported. The two nitrate ISFETs display fast response (less than 25 s), a minimum detection limit of 1.0 × 10−5 mol/l and a linearity range extending over more than three decades, from about 10−5 to 10−2 mol/l, with a slope of about 52 and 54 mV per decade. Lastly, tests were performed on an ISFET with a membrane containing PVC and a copolymer (PVC-poly(vinyl alcohol) (PVA)-poly(vinyl acetate) (PVAc)) as base polymer. The application of these sensors to the nitrate determination in real matrices (river or lake water and aqueous soil extracts) has also been evaluated.

Comparison of three analytical methods for cocaine analysis of illicit powders

A new cocaine-sensitive ISFET device based on a cocaine-reineckate ion-pair complex dispersed in a PVC--sebacate matrix has been fabricated. this sensor displays a linear range for cocaine hydrochloride between about 3 x 10(-6) and 2 x 10(-2) M and a fast response (< or = 25 s), which remains almost constant over the pH range 3-7. The sensor has been applied to the analysis of authentic illicit powders containing cocaine hydrochloride and other substances commonly associated with it, or of cocaine free base (crack). Experimental results were compared with those obtained employing two more common instrumental methods of analysis: gas chromatography (GC), and UV absorption spectrometry (the latter applied directly or based on second derivative absorption spectroscopy). Good agreement was found between results obtained by ISFET and GC methods, while UV absorption spectrophotometry proved suitable only in the case of pure cocaine hydrochloride and free base, or in samples also containing lidocaine, but using second derivative absorption spectroscopy.

A new ISFET device repsonsive to anionic detergents

Abstract An ISFET device selective to anionic detergents, based on a PVC-sebacate membrane, containing benzyldi-methylcetylammonium cholate as exchanger has been prepared, characterized and applied to the determination of some anionic surfactants in standard aqueous solutions and in authentic matrices (lake and sea water). The linearity range extends over 3–4 decades depending on the examined surfactant, within the range between about 10 −6 and 10 −3 mol/l in all cases. The results are compared with those ones obtained by previously described liquid and polymeric membrane sensors, based on the same exchanger.

Lidocaine and benzalkonium analysis and titration in drugs using new ISFET devices

Two new ISFETs recently developed by us have now been applied to some pharmaceutical determinations in real matrices; the first device, responsive to cationic surfactants, was employed in the determination of benzalkonium chloride contained in two different disinfectant solutions and in three types of commercial collyrium; the second device, responsive to cocaine hydrochloride, showed an appreciable response also to lidocaine hydrochloride and was used in the determination of lidocaine hydrochloride contained in some injectable antibiotics. The repeatability and accuracy of measurements performed in the analysis of these pharmaceutical matrices using new solid state sensors were evaluated. A further aspect of the research involved the use of two sensors to record complete titration curves for the determination of benzalkonium chloride, cocaine hydrochloride and lidocaine hydrochloride, respectively. Applications to real matrices were also performed by analysing by titration pharmaceutical formulations containing benzalkonium chloride, or lidocaine hydrochloride and an illicit powder containing cocaine hydrochloride and sugars.

Analysis of Cationic Surfactants in Environmental Aqueous Matrices by New Isfet Devices.

Abstract Three new ISFET devices (ion-selective field effect transistor) based on polymeric selective membranes sensitive to cationic surfactants have been fabricated and characterised. These new sensors use a PVC-sebacate matrix incorporating benzyldimethyl-hexadecylammonium reineckate, dodecyltrimethyl-ammonium reineckate and hexadecylpyridinium phosphotungstate, respectively, as exchanger. A complete electroanalytical characterisation of new cationic ISFETs has been performed and the analytical results compared with those obtained using other sensors such as ISEs equipped with the same exchanger or using a biosensor responsive to cationic and anionic surfactants. Determinations of cationic surfactants in authentic aqueous matrices of environmental interest have been carried out using the new sensor with the best performance. Furthermore, the critical micellar concentration (CMC) of some cationic surfactants has also been evaluated.

Cholanic acids determined in commercial drugs by means of a new ISFET device

An ISFET device selective for cholanic acids, based on a PVC-sebacate membrane, containing benzyldimethylcetylammoniumcholate as exchanger, has been prepared, characterized and applied to the determination of cheno or ursodeoxycholic acid content of commercial pharmaceutical drugs and critical micellar concentration (CMC) values for cholate, deoxycholate and chenodeoxycholate. The results are compared with those obtained using previously described polymeric membrane sensors based on the same exchanger.