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An automated molecularly imprinted sorbent based assay (MIA) for the rapid and sensitive analysis of penicillin-type [beta]-lactam antibiotics (BLAs) has been developed and optimized. The polymers were prepared using penicillin G procaine salt as template (PENGp) and a stoichiometric quantity of a urea-based functional monomer to target the single oxyanionic species in the template molecule. Highly fluorescent competitors (emission quantum yields of 0.4-0.95), molecularly engineered to contain pyrene labels while keeping intact the 6-aminopenicillanic acid moiety for efficient recognition by the cross-linked polymers, have been tested as analyte analogues in the competitive assay. Pyrenemethylacetamido penicillanic acid (PAAP) was the tagged antibiotic providing for the highest selectivity when competing with PenG for the specific binding sites in the molecularly imprinted polymer (MIP). Upon desorption from the MIP, the emission signal generated by the PAAP was related to the antibiotic concentration in the sample. The 50% binding inhibition concentration of penicillin G standard curves was at 1.81 x [10.sup.-6] M PENG, and the detection limit was 1.97 x [10.sup.-7] M. The sensor showed a dynamic range (normalized signal in the 20 to 80% range) from 6.80 x [10.sup.-7] to 7.21 x [10.sup.-6] M (20-80% binding inhibition) PENG in acetonitrile:HEPES buffer 0.1 M at pH 7.5 (40:60, v/v) solutions. Competitive binding studies demonstrated various degrees of cross-reactivity with penicillin-type [beta]-lactam antibiotics such as ampicillin (71%), oxacillin (66%), penicillin V (56%), amoxicillin (13%), and nafcillin (46%) and a lower response to other isoxazolyl penicillins such as cloxacillin (27%) and dicloxacillin (16%). The total analysis time was 14 min per determination, and the MIP reactor could be reused for more than 150 cycles without significant loss of recognition. The automatic MIA has been successfully applied to the direct analysis of penicillin G in spiked urine samples with excellent recoveries (mean value 92%). Results displayed by comparative analysis of the optimized MIA with a chromatographic procedure for penicillin G showed excellent agreement between both methods.

A molecularly imprinted polymer (MIP) prepared using penicillin G procaine salt as the template (PENGp) and a stoichiometric quantity of urea-based functional monomer to target the single oxyanionic species in the template molecule has been applied to the development of a molecularly imprinted solid-phase extraction (MISPE) procedure for the selective preconcentration of [beta]-lactam antibiotics (BIAs) from environmental water samples. Various parameters affecting the extraction efficiency of the polymer have been evaluated to achieve the selective preconcentration of the antibiotics from aqueous samples and to reduce nonspecific interactions. This resulted in an MISPE-HPLC method allowing the direct extraction of the analytes from the sample matrix with a selective wash using just 10% (v/v) organic solvent. On the basis of UV detection only, the method showed good recoveries and precision, ranging between 93% and 100% (RSD 3.8-8.9%, n = 3) for tap water and between 90% and 100% (RSD 4.2-9.1%, n = 3) for river water fortified with 30 or 60 [micro]g [L.sup.-1] (50 mL samples) penicillin G, penicillin V, nafcillin, oxacillin, cloxacillin, and dicloxacillin, suggesting that this MIP can be successfully applied to the direct preconcentration of BLAs in environmental water samples.

The interaction of seven novel fluorescent labeled [beta]-lactams with a library of six polymer materials molecularly imprinted (MI) with penicillin G (PenG) has been evaluated using both radioactive and fluorescence competitive assays. The highly fluorescent competitors (emission quantum yields of 0.4-0.95) have been molecularly engineered to contain pyrene or dansyl labels while keeping intact the 6-aminopenicillanic acid moiety for efficient recognition by the cross-linked polymers. Pyrenemethylacetamidopenicillanic acid (PAAP) is the tagged antibiotic that provides the highest selectivity when competing with PenG for the specific binding sites in a MI polymer prepared with methacrylic acid and trimethylolpropane trimethacrylate (10:15 molar ratio) in acetonitrile in the presence of PenG. Molecular modeling shows that recognition of the fluorescent analogues of PenG by the M! material is due to a combination of size and shape selectivity and demonstrates how critical the choice of label and tether chain is. PAAP has been applied to the development of a fluorescence competitive assay for PenG analysis with a dynamic range of 3-890 [micro]M in 99:1 acetonitrile--water solution. Competitive binding studies demonstrate various degrees of cross-reactivity for some antibiotics derived from 6-aminopenicillanic acid, particularly amoxicillin, ampicillin, and penicillin V (but not oxacillin, cloxacillin, dicloxacillin, or nafcillin). Other antibiotics, such as chloramphenicol, tetracycline, or cephapirin, do not compete with PAAP for binding to the imprinted polymer. The MI assay has successfully been tested for PenG analysis in a pharmaceutical formulation.

A comparative study of the oxygen-quenching features of novel luminescent Ru(II) complexes, covalently attached to controlled porous glass (CPG), has been performed in methanol, chloroform, toluene, cyclohexane, and n-hexane. The investigated dyes contain 1,10-phenanthroline-4,7-bis(phenylsulfonate) (s2d), 5-acetamide-1,10-phenanthroline (acap), and 5-tetradecanamide-1,10-phenanthroline (tdap) coordinated to the Ru[(s2d).sub.2] moiety. The immobilization procedure involves stable sulfonamide linkages to amino-derivatized CPG-Glycophase, the loading being a function of indicator molecular size (i.e., highest for the [Ru[(s2d).sub.2][(acap)].sup.2-] dye). Steady-state and time-resolved emission analysis have revealed that oxygen quenching is purely dynamic and occurs on the glass bead surface. Using a continuous-flow system and a conventional spectrofluorometer, a detection limit of 6.2 [[micro]molar] (200 ppb) oxygen in methanol has been achieved and a 2-4-fold one in the other organic solvents tested, with dynamic ranges over two decades. The analytical figures of merit make the fabricated sensing phases suitable for fiber-optic industrial monitors and oxygen transducers for optical biosensing in nonaqueous media.

Low molecular weight alcohols, such as methanol and ethanol, are optically sensed in nonhydroxylic media using the highly fluorescent dyes 5-(4-aminophenyl)-2-(2-pyrazinyl)-1,3-oxasole (appzox) or -thiazole (appzth). The novel indicator molecules display an absorption band in the blue (up to 450 nm), high emission quantum yields (up to 0.82), and small excited-state lifetimes (1-3 ns) that prevent cross-sensitivity to oxygen. Their large Stokes shift and minute emission ([[Phi].sub.em] < 0.01) in the presence of alcohols are discussed in terms of an adiabatic photoreaction that produces an intramolecular charge-transfer excited state, which constitutes the basis of the sensor response. Fabrication of a fiber-optic sensing head for reversible quantification of such analytes is possible via deposition of the indicator onto silica gel (for gas-phase monitoring) or covalent binding to cross-linked chloromethyiated styrene-divinylbenzene copolymer (for both gas- and liquid-phase measurements). The performance of the optical monitoring device has been tested in the analysis of lower alcohols in hydrocarbon solvents and commercial gasoline samples. Typical response times ([t.sub.100%]) to 0.2-6% (v/v) methanol in the samples are 2-4 rain at 22 [degrees] C, the relative standard deviation for repeated measurements being 1.5-3%. Of all the two- to free-carbon alcohols tested, as well as water (up to saturation), only ethanol may be regarded as interferent for methanol quantification in gasoline. Fiber-optic measurements are also insensitive to other fuel additives such as methyl tert-butyl ether, lead tetraethyl and colored or fluorescent stains. The temperature coefficient of the sensor in the 10-40 [degrees] C range is 0.0057/[degrees] C.

Carbon dioxide monitoring that uses fiber optic sensors provides detection properties that exceed the performance of other fluorescence-based optical devices. This system functions via pH transduction through an excited-state proton transfer to a ruthenium(II) complex which facilitates monitoring of acid concentration changes utilizing emission intensities and lifetime-based measurements. Moreover, the system's detection of excitation and emission wavelengths within the visible region features a Stokes shift which identifies the luminescence signal from scattered light.

This paper describes the preparation of silica nanoparticles doped with a molecularly engineered luminescent Ru(II) complex for the selective determination of Cu(II) ions in aqueous media. Initially, three novel indicator dyes, namely [Ru(phen) 2 (L)] 2+ , where L is either hmpi (2-(1 H -imidazo[4,5- f ]-1,10-phenanthrolin-2-yl)-4-methoxyphenol), haip (1-(4-hydroxy-3-(1 H -imidazo[4,5- f ]-1,10-phenanthrolin-2-yl)phenyl)ethanone), or btym ( N , N' -(2,2'-bipyridine-4,4'-diyl)bis(2-(thymin-1-yl)acetamide)), were synthesised, characterised and their response to metal ions was evaluated. The [Ru(phen) 2 (haip)] 2+ complex demonstrated to be selective to Cu(II), so that it was embedded in 20-nm silica nanoparticles, synthesised by the Stöber method. The maximum sensitivity of the luminescent nanosensor was obtained when the indicator dye was incorporated 8 h after the beginning of the 10-h silane condensation process, because interaction with the metal ions improves when the encapsulated luminophore molecules are closer to the nanoparticle outermost surface The nanosensor showed selective response to Cu(II) in the presence of Zn(II), Hg(II), Pb(II), Ni(II), Cd(II) and Fe(II) ions in 50 mM phosphate buffer at pH 8.0, with a limit of detection of 0.30 μmol L −1 , RSD values lower than 3.0%, and a response time <30 s. The nanosensor was applied to the determination of Cu(II) in mineral and tap waters spiked with 5.0 and 7.0 μmol L −1 of the analyte, with recoveries from 88 to 110%. [ABSTRACT FROM AUTHOR]