Biomedical subjects

Ernest R Blatchley

Publications and source records attributed to Ernest R Blatchley.

7 recordsLinked to original sources

PubMed2005

(E)-5-[2-(methoxycarbonyl)ethenyl]cytidine as a chemical actinometer for germicidal UV radiation.

(E)-5-[2-(Methoxycarbonyl)ethenyl]cytidine (S) was examined for use as a chemical actinometer for germicidal UV radiation. Its photoproduct, 3-beta-D-ribofuranosyl-2,7-dioxopyrido[2,3-d]pyrimidine (P), is strongly fluorescent with excitation and emission maxima at 330 and 385 nm, respectively. Experiments were conducted to characterize the dynamic behavior of aqueous solutions of S and P when subjected to UV radiation. UV sources used for these experiments included a low-pressure mercury lamp, a XeBr excimer lamp, and a KrCI excimer lamp; all three sources were mounted in collimating devices to provide incident beams that could be easily and accurately characterized by radiometry. These three sources each yielded essentially monochromatic outputwith characteristic wavelengths of 254, 282, and 222 nm, respectively. At practical concentrations, it was found that the absorbance of the actinometer solution was neither high enough to make the actinometer solutions optically opaque nor low enough to be optically transparent to UV. In addition, the photoproduct displayed a molar absorption coefficient that was similar in magnitude to that of the parent compound, thereby resulting in competitive absorption of UV energy between Sand Pduring irradiation. For purposes of evaluation of the results of irradiation, a mathematical model was developed to accountforthe nonideal optical characteristics of the system. The model is based on a description of local photochemical kinetics; predictions of overall reactor performance were developed by spatial and temporal integration of model results. The model was used to analyze the dynamic behavior of actinometer solutions during UV irradiation and to estimate the quantum yield for photoproduction of Pfrom S. This modeling approach is potentially applicable to other photochemical processes in which multiple compounds are present that absorb photoactive radiation; however, general application of this modeling approach to photochemical reactor systems will require inclusion of othertermsto describe relevanttransport behavior within the system.

Cytidine↗

PubMed2004

Toxicity of model aliphatic amines and their chlorinated forms.

Aliphatic amines can be found in many wastewater effluents from industry, agriculture, pharmacy, and food processing. Amines can induce toxicological responses that are relevant in biochemical treatment processes, as well as in natural waters. This research compared the toxicity and inhibition caused by three aliphatic amines (n-propylamine, ethylmethylamine, and trimethylamine) and their chlorinated derivatives. The chemistry of chlorine interactions with these compounds was characterized by using membrane introduction mass spectrometry (MIMS). Acute toxicity assays were conducted by using a Microtox system with Phosphobacterium phosphoreum (also known as Vibrio fischeri) for the aliphatic amine compounds and their corresponding chlorinated derivatives, as identified by MIMS. Inhibition tests were conducted by using the oxygen utilization rate test with an enhanced nitrifier culture. The median effective concentration (EC50) values for chloropropylamine, chloroethylmethylamine, and chlorodimethylamine obtained by Microtox with a contact time of 15 min were 12.68, 19.72, and 15.92 microM, respectively. The EC50 values of these aliphatic chloramines from the Microtox test decreased by roughly one order of magnitude as a result of chlorination. Inhibition of nitrifiers also was observed in these amines. Trimethylamine and n-propylamine caused greater inhibition to nitrifiers than did ethylmethylamine under similar concentrations. Nitrifier inhibition from these amines increased after chlorination. The results of these tests indicated that aliphatic amines and their chlorinated derivatives could induce environmentally relevant toxicity responses in treatment settings and in receiving waters.

Amines↗

PubMed2003

Disinfection efficacy of organic chloramines.

The disinfection efficacies of model organic chloramines were investigated. Twenty amino acids and two nucleic acid bases were chlorinated separately with sodium hypochlorite at a Cl:N molar ratio of 0.4:1, and were then used to treat an E. coli suspension for 60 min. DPD/FAS titration was carried out to obtain the concentration of the chlorinated nitrogenous organic compounds as a function of time. In addition, membrane introduction mass spectrometry (MIMS) was used to quantify inorganic chloramines (mono-, di-, and trichloramine). The results of these experiments showed that the organic chloramines examined in this research had little or no effect on the viability of E. coli. MIMS analyses demonstrated that there was no quantifiable formation of inorganic chloramines when the organic nitrogen compounds were chlorinated.

Amino Acids↗

PubMed2003

Copper catalysis in chloroform formation during water chlorination.

The seminal work of Rook initiated a considerable body of research regarding the formation of trihalomethanes (THMs) and other by-products of chlorine-based disinfection. Since that time, a broad spectrum of compounds has been identified as precursors to THM formation. More recently, it has been demonstrated that the presence of copper in solution enhances THM formation. Copper is known to catalyze a number of reactions that are similar to the conventional haloform reaction. A study was therefore initiated to investigate the specific role played by copper in the formation of chloroform during chlorination of water supplies. Aqueous solutions containing a number of known THM precursors were chlorinated in the presence and absence of copper, and subjected to time-course monitoring of chloroform concentration. The results of experiments with humic acid demonstrated an apparent catalytic effect on the part of copper in chloroform formation. To examine the role of copper in greater detail, a series of experiments involving aqueous solutions of pure compounds of humic substance structural units was conducted. Of the pure compounds investigated as THM precursors, only citric acid demonstrated enhanced chloroform formation in the presence of copper. A detailed matrix of experiments conducted with citric acid as a precursor demonstrated that copper, at environmentally relevant concentrations, can have a profound effect on chloroform formation. Based on previously published information regarding the mechanism of chloroform formation from citric acid and the results of these experiments, it is hypothesized that copper promotes chloroform formation from chlorination of citric acid through catalysis of oxidative decarboxylation, and the subsequent chlorination of beta-ketoglutaric acid.

Catalysis↗

PubMed2003

Transport behavior of 3,3'-dichlorobenzidine in a freshwater estuary.

Like many hydrophobic organic compounds, 3,3'-dichlorobenzidine (DCB) partitions preferentially to (sediment) particles in lake systems. As such, the behavior of DCB in these systems is substantially affected by the movement of sediments. A field investigation of DCB distribution in sediments of Lake Macatawa (Holland, MI, USA) was initiated. The pattern of DCB distribution within the lake was found to display an oscillatory pattern that was consistent with a wind-driven mechanism of sediment transport. Numerical modeling of seiching behavior supported the hypothesized importance of this mechanism of sediment transport and redistribution. The dynamic behavior of sediment-associated DCB within Lake Macatawa seems to be strongly influenced by phenomena that are common to many freshwater estuaries. As such, the behavior of this system is expected to represent a reasonable model of the dynamic behavior of hydrophobic contaminants in other freshwater estuaries.

3,3'-Dichlorobenzidine↗

PubMed2002

Photodechlorination of 3,3'-dichlorobenzidine in water.

Laboratory experiments have been conducted to elucidate the photochemical behavior of 3,3'-dichlorobenzidine (DCB) and its congeners in aquatic systems. Photodechlorination of DCB was observed in aqueous samples that were irradiated with monochromatic radiation from a variable-wavelength laser at several wavelengths in the range 300 nm < or = lambda < or = 360 nm. Analytical measurements performed by high-performance liquid chromatography (HPLC) and Fourier-transform ion cyclotron resonance (FT-ICR) mass spectrometry revealed that 3-chlorobenzidine (MCB) was produced as a transient intermediate in the photodechlorination process, with subsequent photodechlorination to yield benzidine as a stable photoproduct. Data obtained from these measurements also suggest the existence of other (unidentified) reaction pathways and products. The time-course measurements of chlorobenzidine congener concentrations and irradiance history were combined with a simple reaction model to develop estimates of reaction kinetics. Model predictions were consistent with results obtained for all wavelengths investigated.

3,3'-Dichlorobenzidine↗

PubMedDate not supplied

Development of a nucleoside analog UV light sensor.

Conjugation of the photosensitive nucleoside (E)-5-(2-methoxycarbonylethenyl)cytidine to biotin provided a means to attach this analogue to microparticles for dosimetry applications that require UV sensor mobility.

Biosensing Techniques↗