Determination of Ethylene Oxide and its Derivative in ...

Determination of Ethylene Oxide and its Derivative in water by GC-FID E.Grushka* and I.Bar-Ilan** * Department of Inorganic and Analytical Chemistry The Hebrew University of Jerusalem, Israel. ** Department of Analytical Chemistry, MIGAL-Galilee Technologic Center, Kiryat-Shmona, Israel.

Abstract Ethylene Oxide (EO) is used for sterilization of medical devices. The British Standard (BS) defines the maximum allowable residues for EO, ethylene chlorohydrine (ECH) and ethylene glycol (EG), for each individual medical device. The method of choice analyzing for these residues is by GC. The current GC methods requires two separate chromatographic runs, one for EO and the other for EG and ECH. In addition, in the existing method the life-time of the columns is very short. The work presented here describes a new gas chromatographic method to determine all three components in aqueous solutions in one run. The life-time of the columns in this method is of conventional duration.

Introduction Determination of Ethylene Oxide (EO) and its derivatives Ethylene Glycol (EG) and Ethylene Chlorohydrin (ECH) in medical devices is of major concern to the health care professionals1 (public health). Gaseous EO is used in medical products sterilization and it is important to ensure that minimal levels of EO EG and ECH are found to minimize risk for the patient2. Many analytical methods for EO and its derivatives have been described and reviewed in the literature3. All the recommended analytical gas chromatography methods available in the standard monographs1,5,6 describe a packed column separation of these residues in aqueous solutions. These methods usually require two separate analysis in order to determine EO EG and ECH in short-live columns. Furthermore, the AAMI suggests specifically separate analyses for EO5 and for EG and ECH6. Danielson4 first described (1990) a capillary column separation of the three materials. The separation was done on two DB-WAX columns, a cross-linked and bonded polyethylene glycol (PEG) on fused silica capillary column. These columns are of high polarities and they are less stable, less robust and have lower temperature limits than most polysiloxanes. They exhibit shorter lifetimes and are more susceptible to damage upon over heating or exposure to oxygen7. Polyethylene glycol stationary phases must be liquids under GC temperature conditions.

EO, ECH & EG – GC/FID Poster Water & SPME Injections

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In the present study a detailed one-step GC analytical method for the analysis of EO and its derivative EG and ECH in aqueous solution is described, using a capillary column coate with dimethylpolysiloxane. This column is non-polar and shows an excellent thermal stability of the stationary phase. This non-polar phase is less susceptible to oxidation and hydrolysis than phases incorporating more polar functional groups8. Thus, the column lifetime is greatly increased. In addition, this paper also presents the use of Solid Phase MicroExtraction (SPME) to determine EO, ECH & EG in aqueous solutions. SPME is used here in the headspace (HS) gas phase as well as in the aqueous phase.

Experimental Materials. Double Distilled Water (DDW) after 0.45µm filtration was used. Ethylene Oxide was obtained from AirGas. Ethylene Glycol and Ethylene Chlorohydrine were manufactured by Merck. Standard solutions. EO from the standard gas cylinder passed through septum with a hypodermic needle to a 30ml serum bottle. Polyvinyl chloride tubing was connected to the vent needle to bubble EO through a filtered DDW in a beaker. The additional weight to the DDW was calculate to receive the EO concentration of the stock solution (approximately 1000mg(EO)/l). 100mg of EG and ECH were transferred to 100ml volumetric flasks and diluted to volume with DDW. Suitable aliquots of the stock solutions were transferred to a 25ml volumetric flask and diluted to volume. Adding appropriate volumes of the standards stocks solution gives the calibration serial solutions. Apparatus. A HP 5890A gas chromatograph with FID equipped with HP 7673 autosampler and a split/splitless injector was used. The chromatography integration is achieved using a Pentium computer equipped with HP-ChemStation chromatography software. Helium was the carrier gas at 1.2 ml/min (Helium velocity of 21.6 cm/sec) and it produces a column head pressure of 6 psi at 38°C. Nitrogen was the auxiliary gas at 30 ml/min. The septum purge gas was Helium at 3 ml/min. The injection volume was 0.5 µl (using 5 µl autosampler syringe), at split ration of 18:1 (vent flow/column flow). The injector temperature was 200°C and the detector temperature was 300°C. Bonded 100% dimethylpolysiloxane fused-silica capillary column was used (Quadrex 007-1 series). The column length was 30 m with i.d. of 0.32 mm, and films thickness of 1.0 µm. This stationary phase is a non-polar phase, which separates compounds according to boiling point, with excellent efficiency and thermal stability (column max temperature of EO, ECH & EG – GC/FID Poster Water & SPME Injections

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350°C). The column temperature was 38°C for 0 min then it rose to 100°C at 5°C/min. Direct Injection. Direct injections carry out with 5µl autosampler syringe, after 3 washes with water and 3 washes in the sample solution. The injection volume was 0.5 µl . SPME apparatus. A manual Solid Phase MicroExtraction (SPME) fiber holder with 100 µm polydimethylsiloxane (PDMS) SPME resin coated fibers protected in SS syringe needle was used. The SPME was obtained from Supelco (Bellefonte, PA). The fibers were conditioned at 200°C for 3 min. Procedure. The standards solution was put in a 2 ml GC autosampler vial sealed with aluminum seal with PTFE-faced red rubber septum. The standards volume was 1 ml, which leaves 1ml air Headspace. For Headspace analysis, 2mm of the SPME syringe penetrated through the vial septum, then the PDMS fiber was exposed to the vial headspace for the desired time. At the end of the adsorption the fiber was retracted to the SS SPME syringe needle, and the SPME holder was taken out of the vial for GC injection.


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EO curve – 5 to 25 ppm (mg/l) in DDW 0.5 µl water automatic 18:1 Split injection at 200°C. 25ppm

15ppm 10ppm 5ppm

EO curve – Direct 0.5 µl water Injection (18:1 split injection)

LOD ~ 1 ppm


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EO SPME curve – 5 to 25 ppm Headspace (HS) – 15 min exposure 1 min desorption at 200°C; splitless injection

EO 25 ppm EO in DDW

15 ppm EO in DDW 10 ppm EO in DDW 5 ppm EO in

EO curve – SPME Headspace

SPME LOD ~ 5 ppm


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ECH curve – 5 to 25 ppm (mg/l) in DDW 0.5 µl water automatic 18:1 Split injection at 200°C.

25 ppm 15 ppm 10 ppm 5 ppm

CH curve – Direct 0.5 µl water Injection (18:1 split injection)

SPME LOD ~ 1 ppm


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ECH SPME curve – 5 to 25 ppm Headspace (HS) – 15 min exposure 1 min desorption at 200°C; splitless injection

ECH

25 ppm 15 ppm

10 ppm 5 ppm

ECH curve – SPME Headspace SPME LOD ~ 5 ppm


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EG curve –25 to 150 ppm (mg/l) in DDW 0.5 µl water automatic 18:1 Split injection at 200°C.

150 ppm

100 ppm 50 ppm

25 ppm

EG curve – Direct 0.5 µl water Injection (18:1 split injection) LOD ~ 20 ppm


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EG SPME curve – 25 to 150 ppm Headspace (HS) – 15 min exposure 1 min desorption at 200°C; splitless injection

EG Not detectable

SPME LOD – not detectable


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EO, ECH & EG mix - GC-FID analysis.

Calibration curve 5 to 25 ppm (mg/l) standards in DDW 0.5 µl water automatic 18:1 Split injection at 200°C. EG (4.13min) 25-150 ppm

EO (1.40min) 5-25 ppm


ECH (3.27min) 5-25 ppm

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EO (1.40min) 5-25 ppm

ECH (3.27min) 5-25 ppm

EG (4.13min) 25-150 ppm


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HeadSpace (HS) SPME - GC-FID Analysis. Calibration curves of EO, ECH & EG mix Headspace (HS) – 15 min exposure 1 min desorption at 200°C; splitless injection

EO

ECH

5-25ppm

5-25ppm

SPME Impurities


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Immersion SPME - GC-FID Analysis. Calibration curves-EO, ECH & EG mix Water Immersion – 15 min exposure 1 min desorption at 200°C; splitless injection

EO 525ppm

ECH 525ppm

EO curve

ECH curve


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Immersion SPME - GC-FID Analysis. Mix of 5ppm EO, 5ppm ECH & 25ppm EG Water Immersion – 15 to 60 min exposure 1 min desorption at 200°C; splitless injection

EO curve

ECH curve


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EO Immersion

Immersion time (min)

ECH Immersion

Immersion time (min)


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RESULTS AND DISCUSSION


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LITERATURE CITED 1. Biological evaluation of medical devices, part 7 – Ethylene oxide sterilization residuals; BS EN ISO 10993-7: 1996. 2. Medical devices-Validation and routine control of ethylene oxide sterilization; ISO 11135: 1994. 3. Biological evaluation of medical devices, part 7 – Ethylene oxide sterilization residuals; Annex F; BS EN ISO 10993-7: 1996. 4. Danielson, J.W., Snell, R.P. and Oxborrow, G.S. Detection and quantification of ethylene oxide, 2-chloroethanol, and ethylene glycol with capillary gas chromatography. J.Chromatogr.Sci.28 1990; pp.97101. 5. Determining Residual Ethylene Oxide in Medical Devices, ANSI/AAMI ST29-1988. 6. Determining Residual Ethylene Chlorohydrin and Ethylene Glycol in Medical Devices, ANSI/AAMI ST30-1989. 7. J&W Scientific Incorporated 1998 catalog, Technical reference & cookbook. 8. Quadrex Corporation 1999 Gas Chromatography Products – Buyers Guide.


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