Stanley M. Billedeau

Influence of selected physical parameters on the biodegradation of acrylamide by immobilized cells of Rhodococcus sp.

The influences of concentration of acrylamide, pH, temperature, duration of storage of encapsulated cells and presence of different metals and chelators on the ability of immobilized cells of a Rhodococcus sp. to degrade acrylamide were evaluated. Immobilized cells (3 g) rapidly degraded 64 and 128 mM acrylamide in 3 and 5 h, espectively, whereas free cells took more than 24 h to degrade 64 mM acrylamide. An acrylamide concentration of 128 mM inhibited the growth of the free cells. Immobilized bacteria were slow to degrade acrylamide at 10 °C. Less than 60% of acrylamide was degraded in 4 h. However, 100% of the compound was degraded in less than 3 h at 28 °C and 45 °C. The optimum pH for the degradation of acrylamide by encapsulated cells was pH 7.0. Less than 10% of acrylamide was degraded at pH 6.0, while ca. 60% of acrylamide was degraded at pH 8.0 and 8.5. Copper and nickel inhibited the degradation, suggesting the presence of sulfhydryl (-SH) groups in the active sites of the acrylamide degrading amidase. Iron enhanced the rates of degradation and chelators (EDTA and 1,10 phenanthroline) reduced the rates of degradation suggesting the involvement of iron in its active site(s) of the acrylamide-degrading-amidase. Immobilized cells could be stored up to 10 days without any detectable loss of acrylamide-degrading activity.

Fluorimetric determination of vitamin K3 (menadione sodium bisulfite) in synthetic animal feed by high-performance liquid chromatography using a post-column zinc reducer.

A high-performance liquid chromatographic (HPLC) method for analysis of vitamin K3 (menadione), as the water-soluble sodium bisulfite salt, in synthetic animal feed is described. The menadione sodium bisulfite (MSB) is extracted with aqueous methanol, converted to oil-soluble menadione with sodium carbonate, and partitioned into n-pentane. After evaporation, the menadione is dissolved in methanol and analyzed by reversed-phase HPLC. The menadione is reduced on-line to its fluorescent 1,4-dihydroxy analogue by zinc reduction prior to fluorescence determination at 325 nm excitation wavelength and 425 nm emission wavelength. The fluorescence response was linear in the range 1 to 100 ng of menadione injected. Recovery experiments were performed on synthetic animal feed spiked at 20 and 200 mg/kg levels of MSB. Average recoveries from feed were greater than 90% with an average relative standard deviation of 5.5%. Additional confirmation of menadione in actual feed extracts was performed using capillary gas chromatography-Fourier transform infrared spectroscopy (GC-FT-IR). The HPLC-fluorescence and GC-FT-IR methods had lower limits of detection of 20 micrograms/kg and 2 mg/kg, respectively.

Recent advances in the gas and liquid chromatography of fluorescent compounds. I. A direct gas-phase isolation and injection system for the analysis of polynuclear arenes in air particulates by gas-liquid chromatography.

Abstract A gas-phase isolation and injection system has been devised that completely eliminates the need for solvents in the preparation of polynuclear arene-containing air particulate samples for analysis by gas-liquid chromatography. The entire package consists of a remote, preparative multi-sample stripper unit, a gas-phase injector mounted on a gas chromatograph, and a gas-phase spectrophotofluorometric detector. Advantages of the gas-phase method over traditional solvent extraction procedures includes short per-sample preparation and handling times, and, since sample size can be relatively large, good sensitivity.

Determination of N-nitrosamines and N-nitrosamine precursors in rubber nipples from baby pacifiers by gas chromatography-thermal energy analysis

N-Nitrosamines and precursors are present in rubber products in which the accelerators and stabilizers used in the vulcanization process were derived from dialkylamines. Research was performed to develop data concerning the presence of N-nitrosamines and precursors so that the health significance of the exposure problem related to infant ingestion of these chemicals could be properly assessed. Volatile N-nitrosamines were determined in cut-up pacifier nipples by extraction with dichloromethane followed by concentration in a Kuderna-Danish evaporator, high-temperature mineral oil purge and trap, and analysis by gas chromatography--thermal energy analysis (GC-TEA). N-nitrosodibutylamine (NDBA) was the principal N-nitrosamine found, with concentrations up to 427 ppb. N-Nitrosamines and precursors in cut-up and intact nipples were determined by GC-TEA after a single extraction with artificial saliva. NDBA was the principal nitrosamine found, at levels up to 1040 ppb, while dibutylamine (DBA) was the principal precursor found, at levels up to 3890 ppb. The persistence of these compounds in intact nipples was determined by multiple artificial saliva extractions. Amounts of NDBA and DBA found after 15 artificial saliva extractions of intact pacifier nipples totalled 824 ppb and 15.6 ppm, respectively. N-Nitrosamine levels generally showed a gradual decrease in concentration with each extraction, whereas no consistent trend could be determined for concentrations of precursors.

Application of the particle beam interface to high-performance liquid chromatography-thermal energy analysis and electron impact mass spectrometry for detection of non-volatile N-nitrosamines

Abstract Interest in the analysis of non-volatile N-nitrosamines has recently been renewed due to the development of several new reversed-phase HPLC interfaces to thermal energy analysis (TEA) or chemiluminescence detection. A new application of a counter flow gas diffusion cell (CFGDC)-based particle beam LC interface (Universal Interface, Vestec) is described for the HPLC-TEA analysis of the non-volatile N-nitrosamines, N-Nitrosodiethanolamine (NDELA) and N-nitrosomethyl-p-amino-2-ethylhexylbenzoate (NMPABAO). The interface incorporates a thermospray vaporizer, desolvation chamber, and CFGDC to reduce the LC effluent to a dry aerosol and a single-stage momentum separator to form a particle beam of the non-volatile analyte. Using this system, the LC-TEA response to NDELA was linear in the range 6–200 ng total amount injected. Several experiments are reported indicating the effect of thermospray tip temperature, He carrier flow-rate, and mobile phase composition on TEA response. Minimum detection limits (5 ng NDELA injected on column) are comparable to other LC-TEA interfacing methods. Several advantages over existing methodology which include ease of use, ruggedness and MS compatibility are discussed. Additional LC-particle beam MS data are reported indicating that full scan electron impact MS identification of the N-nitrosamine contaminants in cosmetics is possible for confirming TEA detection data.

Evaluation of porous polymer traps for analysis of four volatile N-nitrosamines using thermal desorption injection coupled with a gas chromatograph-thermal energy analyzer.

Three porous polymer adsorbents, Tenax-TA, Chromosorb 102, and Chromosorb 103 were investigated as potential gas phase, trapping agents for volatile N-nitrosamines using a thermal desorption injector coupled with a gas chromatograph-thermal energy analyzer. N-Nitrosodimethylamine was used as the model N-nitrosamine for determining break-through volume, the effect of temperature on retention volume, and collection efficiency at 25 degrees C for each adsorbent. Results from these three parameters indicated that Chromosorb 103 exhibited the best adsorbent characteristics for the pre-concentration of volatile N-nitrosamines. A mixture of three dialkyl N-nitrosamines (dimethyl, diethyl, and dipropyl), and N-nitrosopyrrolidine were analyzed using a high-temperature mineral oil purge and trap procedure. Recoveries ranged from 82.2 to 102.8% at levels of 10 and 100 ng of each N-nitrosamine added.

High-performance liquid chromatography of the antihistamine pyrilamine and its N-oxide using electrochemical detection.

The electrochemical behavior of the over-the-counter antihistamine drug pyrilamine and its N-oxide analogue, have been studied by several voltammetric methods. Cyclic voltammograms of pyrilamine maleate in 0.1 M ammonium acetate at pH 7.0 indicated a quasi-reversible electrode process by observing a wave at + 0.85 V and + 1.30 V in the initial anodic sweep followed by a wave at - 1.30 V versus Ag/AgCl. Differential pulse and hydrodynamic voltammetry of pyrilamine and the N-oxide were examined to determine oxidation potentials for use in high-performance liquid chromatography with electrochemical detection (HPLC-ED). Differentiation between pyrilamine and its N-oxide was achieved in HPLC-ED analyses at a detection potential of + 0.7 V and + 0.9 V versus Ag/AgCl with tandem ultraviolet detection at 254 nm. Utility of the HPLC-ED method was demonstrated by the analysis of pyrilamine and the N-oxide in microbial biotransformation samples.