Residual Ethylene Research Articles

Equivalency of Hydrochloric Acid and Distilled Water Extraction Media for Determining Residual Ethylene Oxide in Medical Devices

An alternate method for determining residual ethylene oxide (EtO) in medical devices was compared with the aqueous extraction method suggested by the Association for the Advancement of Medical Instrumentation (AAMI). Residual EtO was extracted from EtO-sterilized samples of acrylic polymer (XT250-301 glass-tinted formulation) in pellet form by immersion in 1M HCI at 37 ± 2°C (alternate method) or immersion in distilled water (AAMI method). The EtO residuals in the extracts were determined using gas chromatography and were statistically compared using a two-sample t test. Results obtained using the alternative method agreed within 10% of those obtained using the AAMI method.

Comparison of Two Methods for Enumeration of Anaerobe Numbers on Forages and Evaluation of Ethylene Oxide Treatment for Forage Sterilization

Experiments were conducted to (i) compare most-probable-number (MPN) procedures with roll tube procedures for enumeration of forage anaerobic bacteria and (ii) evaluate the efficacy of using ethylene oxide to sterilize wet herbage. Alfalfa, corn, and alfalfa-orchardgrass silages and alfalfa and orchardgrass herbages were analyzed for total anaerobic bacteria (medium pH, 6.8) and acid-tolerant anaerobic bacteria (medium pH, 4.5) by both roll tube and MPN procedures. No difference was found between the roll tube and MPN procedures for total bacteria; however, higher counts were obtained for acid-tolerant bacteria when the MPN procedure was used. Although MPN procedures require less time to obtain an estimate of bacterial numbers, isolation and identification of the microbial population is not possible. Alfalfa herbage was treated with ethylene oxide for 12, 24, or 36 h, incubated for 7 days at 37 degrees C with or without addition of a bacterial inoculant, and analyzed for total bacteria by MPN procedures. Microbial growth after inoculation of ethylene oxide-treated herbage indicated that there was insufficient residual ethylene oxide to inhibit subsequent microbial growth. The results also indicated that 24 h was required to adequately sterilize fresh herbage. Thus, ethylene oxide can be used to sterilize wet herbage for use as a substrate for pure cultures of silage bacteria.

Residual ethylene oxide in hollow fiber hemodialysis units is neurotoxic in vitro.

Ethylene oxide gas is used to sterilize plastic medical equipment including capillary flow dialysis membranes. To test whether ethylene oxide retained in the dialyzers might be neurotoxic, tissue culture medium was incubated in the blood compartment of dialyzers. Embryonic rat dorsal root ganglion neurons were then incubated in this medium for up to 5 days. During the first 24 hours axonal growth was normal. During the next 24-hour period varicosities appeared on axons, and after 4 days neuron cell bodies died. The pattern of degeneration was identical to that observed when cultures were exposed to an atmosphere containing 1 ppm ethylene oxide gas. Culture medium introduced into dialyzers after routine prerinsing still caused degeneration, which was not completely abolished even by a 10-liter rinse. When medium was exposed to identical dialyzers sterilized by gamma irradiation, no changes were seen in culture. Identical morphological changes were produced by using dialysis patient serum in the culture medium in place of the usual calf bovine serum. Such changes were never seen with control human serum. Since ethylene oxide is toxic to the human peripheral nervous system, it is proposed that ethylene oxide in dialyzers may contribute to the progressive neuropathy observed in patients on long-term hemodialysis.

Determinationo f Residual Ethylene Oxide in Small Samples by Electron-Capture Detection Gas Chromatography : Aplication to Intraocular Lens

Determinationo f Residual Ethylene Oxide in Small Samples by Electron-Capture Detection Gas Chromatography : Aplication to Intraocular Lens

Residual ethylene oxide determination in polymethyl methacrylate disks and intraocular lenses by headspace gas analysis and N,N-dimethylformamide extraction.

The residue in an ethylene oxide (EO)-exposed polymethyl methacrylate (PMMA) material [flat disk and intraocular lens (IOL)] was determined using three methods: semiautomatic and manual headspace methods and N,N-dimethylformamide (DMF) solvent extraction. Results from the analysis of three different sample configurations at three different EO concentrations are compared. Results from the DMF extraction of PMMA indicate that the headspace methods at 100 degrees C are not exhaustive with respect to recovery of total residual ethylene oxide. Furthermore, the manual headspace method appears to be slightly more effective than the semiautomatic injection headspace method. Sorption of EO and subsequent extraction is related to the surface area-to-volume ratio of the sample, with higher concentrations observed in samples with the high ratio.

Gas Chromatographic Determination with Electron Capture Detection of Residual Ethylene Oxide in Intraocular Lenses

A sensitive method is described to determine trace quantities of ethylene oxide (EO) in EO-sterilized intraocular lenses (IOLs). An IOL is dipped in ethanol containing 0.25 ppm propylene oxide (PO) in a 4 mL vial, 2 drops of freshly distilled hydrobromic acid is added through a septum, and the mixture is warmed at 50 degrees C for 24 h. It is then neutralized by vigorous shaking with sodium bicarbonate, dehydrated with anhydrous sodium sulfate, and filtered. The filtrate is injected into a gas chromatograph with electron-capture detection, and the peak height ratio of ethylene bromohydrin/propylene bromohydrin is measured. EO residue is calculated from the calibration curve obtained through a similar procedure with the standard EO/PO solutions. The limit of determination is 0.04 microgram/lens (ca 2.0 ppm). When EO residue levels were determined for IOLs sampled at 3 different aeration periods after sterilization, we found that 9 days of aeration was necessary to meet the U.S. Food and Drug Administration proposed limit for EO residue in IOLs.

Determination of fumigants in cereals and cereal products by capillary gas chromatography.

This study describes two methods for the quantitative determination of the residual fumigants ethylene dichloride (EDC), carbon tetrachloride (CCl4), trichloroethylene (TCE), ethylene dibromide (EDB) and tetrachloroethylene (PCE) in cereals (especially wheat) and other foodstuffs. In the first method, a micro steam distillation- solvent extraction apparatus is used, while the second method is based on a headspace technique. For the quantitative determination of carbon tetrachloride in cereals, the multiple headspace technique is not retained because it is too time-consuming. The analysis of the different fumigants is performed by electron-capture gas chromatography, using a fused silica capillary column, CP sil 8 CB. With the steam distillation-solvent extraction method, recoveries from 95.9% to 100.5% are obtained for the fumigants, added at two different levels. The standard deviation varies between 1.1% and 6%. Using the simple headspace technique, recoveries from 73.5% to 85.1% with a standard deviation of between 1.7% and 6.6% have been reached for the fumigants in cereals fortified at two different levels. The absolute detection limits for the five fumigants EDC, CCl4, TCE, EDB and PCE, in both methods, are 30, 0.25, 1.1, and 0.5 pg, respectively.

Toxicity potential of residual ethylene oxide on fresh or frozen embryos maintained in plastic straws.

The toxic effects of residual ethylene oxide (EtO), a frequently used gas-sterilant, on embryos either frozen for long-term purposes or stored acutely for 30 min to 9 hr in a fresh condition in 0.25-ml straw containers were evaluated. In Experiment 1, fresh embryos were frozen (using conventional technology) in straws previously aerated for 0 hr to 8 mo after EtO sterilization. With the exception of the 8-mo group in which survival and quality ratings were depressed, embryo viability was not affected significantly by short-term prefreeze and post-thaw exposure to EtO residues. Experiment 2 was conducted to analyze the influence of prefreeze exposure to EtO residues on embryo development in vitro for embryos temporarily stored in previously sterilized straws aerated for different intervals. Compared to non-EtO-sterilized control straws, the development, quality, and viability of embryos exposed to EtO-treated straws were compromised (p less than 0.05) as the aeration interval decreased and the exposure interval increased. The combined results of both experiments indicate that EtO-treated straws can be used to cryopreserve gametes efficiently, but only if the aeration interval is greater than or equal to 72 hr and the prefreeze duration of exposure is less than or equal to 3 hr.

Structure and properties of crystalline polymer fibers

Most polymer fibers studied by TEM have been semi-crystalline or more recently liquid crystalline, both because the majority of technically interesting fibers are ordered and because scientific interest lies in the polymer morphology. The obvious common feature of fibers is that they are "fibrous" that is to say, they have long and narrow features aligned along the fiber direction. The basic unit obtained by a very local deformation of a crystal is called a micro-fibri l . [1,2] Fibrils may or may not be clear in the TEM, either because the structure itself is not well defined or because of superposition of several small fibrils within the sample.The large plastic deformation in fiber drawing will make any heterogeneity in the material appear fibrous. While zone drawing gels of poly(vinyl alcohol) recently we obtained porous fibers when residual ethylene glycol solvent boiled at just below the draw temperature.

Interlaboratory Comparison of Analytical Methods for Residual Ethylene Oxide in Medical Device Materials

An interlaboratory comparison of four gas chromatographic test procedures for the quantification of ethylene oxide in an acrylic polymer was conducted by thirteen laboratories. The procedures included extractions with water, acetone, and N,N-dimethylformamide, and headspace gas analysis. The results of this study, using only the data from the labs that did not deviate from the procedure, showed that the average estimated total coefficient of variation ranged from 8 to 22% for the four different methods. Each of the methods is suitable for use as a reference test method for determining residual ethylene oxide in polymeric materials.

On-Stream HPLC Determination of Residual Ethylene Oxide and Propylene Oxide in Glycerol Based Polyol Synthesis

Abstract A simple automated HPLC scheme was developed to monitor synthetic polymerization reaction on-stream. Chromatographic conditions that affect the separation of the reaction species from the reaction product and base catalyst using high-performance aqueous gel permeation chromatography were also studied. Reactor samples are automatically drawn from the reaction vessel through a micro-loop sampling valve/actuator assembly and transferred to the chromatographic system via stainless steel tubing without interruption of the mobile phase flow. The resulting chromatograms, monitored by a refractive index detector, of reactants and products are continuously measured at intervals during the reaction automatically and unattended. Application of this system for the reaction of propylene oxide and ethylene oxide to high molecular weight polyols is presented.

Physical characteristics of various intraocular lenses

Physical characteristics of 15 posterior chamber lenses from 15 companies were examined for residual ethylene oxide gas; the content varied from 13 ppm to 78 ppm. Seven lenses met the FDA regulation of less than 25 ppm. Scanning electron microscopic study revealed that molded-type lenses had the smoothest optic surface and cast-molded lenses had a less smooth surface than the plano side. The lathe-cut lens with barrel polishing also had a smooth optic surface. Neodymium: YAG laser shots were delivered to the optic and the spots were examined by phase contrast microscopy. The lenses made of high molecular weight polymethylmethacrylate were more resistant to YAG laser damage. It was concluded that lathe-cut posterior chamber lenses with barrel polishing made of high molecular weight polymethylmethacrylate would be preferable but further studies of polishing compounds are necessary.

Sensitization of repeat plasmapheresis donors to ethylene oxide gas.

Repeat plasma donors were studied to determine whether there was a relationship between allergic-type reactions during plasmapheresis and IgE-dependent sensitization to ethylene oxide gas used for sterilization of disposable fluid administration sets. Serums from 32 donors with allergic-type reactions and 84 donors who had no reactions but were exposed to the same materials and served as controls were tested for IgE-antibodies to ethylene oxide. The results, expressed as an IgE ethylene oxide index, were greater than 2 in 78 percent of serums from donors with allergic reactions and 12 percent of serums from controls. This association was significant (p less than 0.0001). Reactivity of the antibodies was directed against an ethylene oxide-human serum albumin conjugate and not against human serum albumin carrier protein. IgG antibodies with ethylene oxide specificity also were present in the serums of repeat plasmapheresis donors. Each of seven rabbits immunized with an ethylene oxide-protein conjugate responded with a high serum level of antibody with ethylene oxide specificity. It was concluded that the residual ethylene oxide in fluid administration sets is immunogenic and may cause allergic reactions in plasma donors.

Rapid Gas Chromatographic Determination of Ethylene Oxide, Ethylene Chlorohydrin, and Ethylene Glycol Residues in Rubber Catheters

Isothermal gas chromatography with flame ionization detection was used to determine residual ethylene oxide (EtO), ethylene chlorohydrin, and ethylene glycol in soft rubber catheters that had been sterilized with EtO. Catheter samples were extracted by shaking with carbon disulfide, and the extract was analyzed on a 3% Carbowax 20M on 80-100 mesh Chromosorb 101 column, using nitrogen as the carrier gas. Ten replicate injections of a mixed standards solution gave coefficients of variation of 1.91, 1.23, and 4.74% for EtO, ethylene chlorohydrin, and ethylene glycol, respectively. A linear response was obtained with concentrations ranging from 1.0 to 7.9 micrograms EtO, 14.0 to 88.0 micrograms ethylene chlorohydrin, and 31.0 to 98.5 micrograms ethylene glycol. The proposed method detected as little as 0.5, 5.0, and 16.5 ng EtO, ethylene chlorohydrin, and ethylene glycol, respectively.

Determination of residual ethylene dibromide in cereals by glass capillary gas chromatography.

This study describes two methods for the quantitative determination of residual ethylene dibromide (1,2-dibromoethane) in cereals, especially wheat, and in dried fruit. The first method is based on a solvent-extraction technique; in the second a continuous micro steam-distillation--solvent-extraction apparatus is used. The quantitative determination of ethylene dibromide is performed by electron-capture gas chromatography using a glass capillary column coated with CPwax 51. The absolute detection limit for EDB is 0.5 pg and recoveries of 82 and 98% resp. are obtained for samples with EDB added in the range of 10 to 50 micrograms/kg. 75 samples of cereal products and 19 samples of dried fruit have been analysed with the solvent extraction method. For 22 samples the micro steam-distillation-solvent-extraction technique has been used.

Gas chromatographic determination of residual ethylene oxide in gas-sterilized, medical-grade plastics

Gas chromatographic determination of residual ethylene oxide in gas-sterilized, medical-grade plastics

Residual ethylene oxide in hollow-fiber dialyzers.

The deaeration and extraction kinetics of ethylene oxide (ETO) in hollow-fiber dialyzers were examined. The investigations showed that both deaeration and extraction can be described by two additive first-order kinetic expressions. The ETO content of membranes decreased rapidly at first, followed by a second slower decrease. Even after prolonged storage time, residual ETO was still detectable in the milligram range. These residuals cannot be eliminated by the usual rinsing of the dialyzer prior to use.

Determination of residual ethylene chlorohydrin (ECH) in fumigated foodstuffs by glass capillary gas chromatography

A simple quantitative method for the determination of residual ethylene chlorohydrin in fumigated foodstuffs is described. The method is based on a solvent extraction and quantitative determination of ethylene chlorohydrin by capillary gas chromatography using dibutyl ketone as internal standard. The chromatographic identification of ethylene chlorohydrin is performed on a glass capillary column coated with Carbowax 20 M. The detection limit of this analytical system is 2 ng. Recoveries of added ethylene chlorohydrin from foodstuffs are between 85% and 99% in the concentration range of up to 100 ppm. Of a total of 340 samples analysed 11,6% were positive for ethylene chlorohydrin.

Studies on Residual Ethylene Oxide in Medical Devices (I) : Gas Chromatographic Determination of Ethylene Oxide in Plastics

Studies on Residual Ethylene Oxide in Medical Devices (I) : Gas Chromatographic Determination of Ethylene Oxide in Plastics

Studies on Residual Ethylene Oxide in Medical Devices (II) : Residue and Dissipation of Ethylene Oxide in Surgical Glove and Various Rubber Materials

Studies on Residual Ethylene Oxide in Medical Devices (II) : Residue and Dissipation of Ethylene Oxide in Surgical Glove and Various Rubber Materials