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

Fabrication of ultra-thin polypyrrole-glucose oxidase film from supporting electrolyte-free monomer solution for potentiometric biosensing of glucose

A simple electropolymerisation process is described for the fabrication of an ultra-thin (55 nm) polypyrrole (PPy)–glucose oxidase (GOD) film in a supporting electrolyte-free monomer solution for potentiometric biosensing of glucose. The optimum conditions for growing the ultra-thin film include 0.1 M pyrrole, 55–110 U/ml GOD, an applied current density of 0.05 mA/cm2 and an electrical charge of 25 mC/cm2. Long-term storage of the biosensor in acetate buffer improved the sensitivity of the biosensor by a factor of approximately two. The biosensor can also be used repeatedly for over 2 months with little or no loss in sensitivity. The interference effect of ascorbic acid was successfully reduced by inclusion of an outer PPy-Cl layer

Arsenic Contamination of Groundwater and Its Implications for Drinking Water Quality and Human Health in Under-Developed Countries and Remote Communities—A Review

Arsenic is present naturally in many geological formations around the world and has been found to be a major source of contamination of groundwater in some countries. This form of contamination represents a serious threat to health, economic and social well-being, particularly in under-developed countries and remote communities. The chemistry of arsenic and the factors that influence the form(s) in which it may be present and its fate when introduced into the environment is discussed briefly in this review. A global overview of arsenic contamination of groundwater around the world is then discussed. As a case study, the identified and established causes of groundwater contamination by arsenic in Bangladesh is highlighted and a perspective is provided on the consequential health, agricultural, social and economic impacts. In addition, the relevant removal strategies that have been developed and can generally be used to remediate arsenic contamination are discussed. Also, the possible influence of groundwater inorganic compositions, particularly iron and phosphate, on the effectiveness of arsenic removal is discussed. Furthermore, some specific examples of the filter systems developed successfully for domestic arsenic removal from groundwater to provide required potable water for human consumption are discussed. Lastly, important considerations for further improving the performance and effectiveness of these filter systems for domestic use are outlined

Photoinitiator-free UV grafting of styrene, a weak donor, with various electron-poor vinyl monomers to polypropylene film

This study investigated the possibility of using styrene, a weak donor forming donor(D)/acceptor(A) pairs with electron-poor (EP) vinyl monomers, for initiating spontaneous photopolymerization and photografting of the copolymers onto polypropylene. Maleic anhydride (MA), methyl methacrylate (MMA), methyl acrylate (MAC), dimethyl maleate (DMMA), acrylonitrile (AN) and acrylic acid (AA) were the EP monomers used. Grafting yields together with FTIR analyses were used to confirm the presence of grafting. Styrene/MMA and styrene/AN systems achieved significant grafting, but such levels of grafting were not observed in the styrene/MAC and styrene/DMMA systems. No grafting was observed for styrene/AA or styrene/MA systems, but the latter system underwent photopolymerization. The effect of solvents on grafting was evaluated on styrene/MMA and styrene/AN systems and dimethylformamide (DMF) was found to retard grafting of both D/A systems. In contrast, chloroform and methanol enhanced grafting of the styrene/AN system although these two solvents had no significant effect on the grafting of the styrene/MMA system

Effect of an intermediate on the amperometric response of a polypyrrole-based formate biosensing membrane

It was evidenced that an intermediate exists in the polypyrrole conjugation system, resulting in a negative response. This fact is a disadvantage with respect to the amperometric response, due to the changing background current that overlaps with the response of the biosensing system. The solution to this problem is to use an overoxidised polypyrrole film for stabilising the background. Keywords: Polypyrrole, Biosensors, Formate, Amperometry, Intermediate

Measurement of polarization parameters impacting on electrodeposit morphology. II, Conventional zinc electrowinning solutions

A new technique for measuring effects of polarization modifiers on nucleation potential and plating potential in polycrystalline electrodeposition was presented in Part I of this series (J. Appl. Electrochem. 32(2002) 1101–1107). This paper presents the