Galvanostatic Entrapment of Penicillinase into Polytyramine Films and its Utilization for the Potentiometric Determination of Penicillin

A sensitive and reliable potentiometric biosensor for determination of penicillin has been developed by exploiting the self-limiting growth of the non-conducting polymer, polytyramine. Optimum polytyramine-penicillinase (PTy-PNCnase) films for potentiometric detection of penicillin were accomplished with monomer solutions which contained 0.03 M tyramine, 37 U/mL penicillinase, 0.01 M KNO3, and 3 mM penicillin with an applied current density of 0.8 mA/cm2 and an electropolymerisation time of 40 seconds. The potentiometric biosensor gave a linear concentration range of 3–283 μM for penicillin and achieved a minimum detectable concentration of 0.3 μM. The biosensor was successfully utilized for the detection of Amoxycillin and gave an average percentage recovery of 102 ± 6%. Satisfactory recoveries of penicillin G were also achieved in milk samples with the potentiometric biosensor when concentrations are ≥20 ppm

Phosphorus distribution in soils from Australian dairy and beef rearing pastoral systems

The influence of soil type and management practices on P distribution in soils from Australian dairy and beef rearing pastoral systems has been investigated by chemical measurements and phosphorus-31 (31P) nuclear magnetic resonance (NMR) spectroscopy. The amount and forms of P within the soil profile varied with soil type, with the acidic red Ferrosols containing relatively high orthophosphate concentrations, averaging 72.2% compared with 66.8% for Dermosols, under similar management conditions. Soil from Sodosol sites which received less fertiliser P addition had the lowest orthophosphate concentration with only 57.6%. In contrast, relatively high proportions of organic P were found in soil samples from unfertilised Sodosol sites. On average, soil from Sodosol sites contained 37.5% organic P (combined monoester P and diester P), while those from Dermosol and Ferrosol sites contained 31.7% and 25.8%, respectively. Of these, the highest monoester phosphate proportions of 44.6% (site M3) and 46.4% (site M4) were found in Sodosol sites with no recent P inputs, but the highest proportion of diester phosphate (5.7%) was found in an unclassified grey sandy loam Dermosol. The higher organic P concentrations in soil from Sodosol sites may be associated with more regular moisture input from both rainfall and boarder-check (flood) irrigation. The highest level of pyrophosphate (8.5%) was also found in a grey/yellow Sodosol. Overall, the results indicate that P speciation in the Australian soils is strongly influenced by soil type, fertiliser P application rate and timing, and moisture variations.Samuel B. Adeloju, Benjamin Webb and Ronald Smerni

Phosphorus distribution in soils from Australian dairy and beef rearing pastoral systems

The influence of soil type and management practices on P distribution in soils from Australian dairy and beef rearing pastoral systems has been investigated by chemical measurements and phosphorus-31 (31P) nuclear magnetic resonance (NMR) spectroscopy. The amount and forms of P within the soil profile varied with soil type, with the acidic red Ferrosols containing relatively high orthophosphate concentrations, averaging 72.2% compared with 66.8% for Dermosols, under similar management conditions. Soil from Sodosol sites which received less fertiliser P addition had the lowest orthophosphate concentration with only 57.6%. In contrast, relatively high proportions of organic P were found in soil samples from unfertilised Sodosol sites. On average, soil from Sodosol sites contained 37.5% organic P (combined monoester P and diester P), while those from Dermosol and Ferrosol sites contained 31.7% and 25.8%, respectively. Of these, the highest monoester phosphate proportions of 44.6% (site M3) and 46.4% (site M4) were found in Sodosol sites with no recent P inputs, but the highest proportion of diester phosphate (5.7%) was found in an unclassified grey sandy loam Dermosol. The higher organic P concentrations in soil from Sodosol sites may be associated with more regular moisture input from both rainfall and boarder-check (flood) irrigation. The highest level of pyrophosphate (8.5%) was also found in a grey/yellow Sodosol. Overall, the results indicate that P speciation in the Australian soils is strongly influenced by soil type, fertiliser P application rate and timing, and moisture variations. © 2016 by the authors; licensee MDPI, Basel, Switzerland

Determination of Antimony (III) in Real Samples by Anodic Stripping Voltammetry Using a Mercury Film Screen-Printed Electrode

This paper describes a procedure for the determination of antimony (III) by differential pulse anodic stripping voltammetry using a mercury film screen-printed electrode as the working electrode. The procedure has been optimized using experimental design methodology. Under these conditions, in terms of Residual Standard Deviation (RSD), the repeatability (3.81 %) and the reproducibility (5.07 %) of the constructed electrodes were both analyzed. The detection limit for Sb (III) was calculated at a value of 1.27×10−8 M. The linear range obtained was between 0.99 × 10−8 − 8.26 × 10−8 M. An analysis of possible effects due to the presence of foreign ions in the solution was performed and the procedure was successfully applied to the determination of antimony levels in pharmaceutical preparations and sea water samples

Chemical characterization of MEA degradation in PCC pilot plants operating in Australia

An important step towards commercial scale post-combustion CO2 capture from coal-fired power stations is understanding solvent degradation. Laboratory scale trials have identified three main solvent degradation pathways for 30% MEA: oxidative degradation, carbamate polymerization and formation of heat stable salts. This paper probes the semi-volatile organic compounds produced from a single batch of 30% MEA which was used to capture CO2 from a black coal-fired power station (Tarong, Queensland, Australia) for approximately 700 hours, followed by 500 hours at the brown coal-fired power station (Loy Yang, Victoria, Australia). Comparisons are made between the compounds identified in this aged solvent system with MEA degradation reactions described in literature. Most of semi-volatile compounds tentatively identified by GC/MS have previously been reported in laboratory scale degradation trials. Our preliminary results show low levels of degradation products were present in samples after its use in the pilot plant at Tarong (black coal) and consequent 13 months storage, but much higher concentrations were later found in the same solvent during its at use in the pilot plant at Loy Yang Power (brown coal). Further work includes identifying the cause of poor GC/MS repeatability and investigating the relative rates of reactions described in literature. The impact of inorganic anions and dissolved metals on MEA degradation will also be explored

A Novel Conductometric Urea Biosensor with Improved Analytical Characteristic Based on Recombinant Urease Adsorbed on Nanoparticle of Silicalite

Development of a conductometric biosensor for the urea detection has been reported. It was created using a non-typical method of the recombinant urease immobilization via adsorption on nanoporous particles of silicalite. It should be noted that this biosensor has a number of advantages, such as simple and fast performance, the absence of toxic compounds during biosensor preparation, and high reproducibility (RSD = 5.1 %). The linear range of urea determination by using the biosensor was 0.05–15 mM, and a lower limit of urea detection was 20 μM. The bioselective element was found to be stable for 19 days. The characteristics of recombinant urease-based biomembranes, such as dependence of responses on the protein and ion concentrations, were investigated. It is shown that the developed biosensor can be successfully used for the urea analysis during renal dialysis

Electrochemical Glucose Sensors—Developments Using Electrostatic Assembly and Carbon Nanotubes for Biosensor Construction

In 1962, Clark and Lyons proposed incorporating the enzyme glucose oxidase in the construction of an electrochemical sensor for glucose in blood plasma. In their application, Clark and Lyons describe an electrode in which a membrane permeable to glucose traps a small volume of solution containing the enzyme adjacent to a pH electrode, and the presence of glucose is detected by the change in the electrode potential that occurs when glucose reacts with the enzyme in this volume of solution. Although described nearly 50 years ago, this seminal development provides the general structure for constructing electrochemical glucose sensors that is still used today. Despite the maturity of the field, new developments that explore solutions to the fundamental limitations of electrochemical glucose sensors continue to emerge. Here we discuss two developments of the last 15 years; confining the enzyme and a redox mediator to a very thin molecular films at electrode surfaces by electrostatic assembly, and the use of electrodes modified by carbon nanotubes (CNTs) to leverage the electrocatalytic effect of the CNTs to reduce the oxidation overpotential of the electrode reaction or for the direct electron transport to the enzyme

A self assembled monolayer based microfluidic sensor for urea detection

Urease (Urs) and glutamate dehydrogenase (GLDH) have been covalently co-immobilized onto a self-assembled monolayer (SAM) comprising of 10-carboxy-1-decanthiol (CDT) via EDC–NHS chemistry deposited onto one of the two patterned gold (Au) electrodes for estimation of urea using poly(dimethylsiloxane) based microfluidic channels (2 cm × 200 μm × 200 μm). The CDT/Au and Urs-GLDH/CDT/Au electrodes have been characterized using Fourier transform infrared (FTIR) spectroscopy, contact angle (CA), atomic force microscopy (AFM) and electrochemical cyclic voltammetry (CV) techniques. The electrochemical response measurement of a Urs-GLDH/CDT/Au bioelectrode obtained as a function of urea concentration using CV yield linearity as 10 to 100 mg dl−1, detection limit as 9 mg dl−1 and high sensitivity as 7.5 μA mM−1 cm−2