Phthalates in Dog Toys Gc/ms

Introduction

Phthalates are chemicals added to plastics to make them more flexible and harder to break. They are used in hundreds of plastic products, such as vinyl flooring, shower curtains, and plastic toys, but they may pose a health risk to humans and animals alike.1 Growing health concerns resulted in increased government regulations. In 1999, the European Commission restricted that the phthalates DEHP, DBP, and BBP not be present in concentrations greater than 0.1% by weight in children’s toys or plastic items designed to go into a child’s mouth.2 Three additional phthalates, DINP, DIDP, and DNOP, are not to be present in concentrations greater than 0.1% by weight in toys designed to be placed in the mouth.2 The US passed similar regulations in 2008, citing that the phthalates DEHP, DBP, and BBP not be present in children’s toys or child care articles at concentrations greater than 0.1%.2 The phthalates DINP, DIDP, and DNOP are conditionally banned above the concentration of 0.1% pending further analysis.2 This regulation, however, does not extend to pet toys. So, while children are protected against these potentially harmful chemicals, man’s best friend may be exposed. This study aims to quantify the amount of phthalates in dog toys using gas chromatography/mass spectrometry (GC/MS). The GC will be used to separate the phthalates from the rest of the plastic matrix, while the MS will be used to quantify the amount and confirm its identification. [pic 1][pic 2]

        Gas chromatography is a common analytical technique that separates and analyzes compounds that can be thermally vaporized without decomposition based on their differential affinity for the mobile and stationary phase.3,4 GC uses an inert or unreactive carrier gas such as helium, hydrogen, or nitrogen as the mobile phase.4 The stationary phase consists of a thin liquid or polymer coating on an inert solid support inside of a metal or glass tube column. The column can either be packed or capillary, however capillary tubes are used more frequently because they have a higher resolution and sensitivity along with a shorter experimental time.4 After the analyte is vaporized in the injection port, its components travel in the carrier gas and interact with the stationary phase as it moves through the column, causing them to elute at different times, called retention times.34 Retention times are determined by compounds boiling points, polarity, and affinity for the stationary phase. This leads to separation of the analytical matrix, and the relative retention times serve to identify each compound. This tool is only useful when analyzing volatile, thermally stable compounds. High performance liquid chromatography (HPLC) may be used when analyzing non-volatile or thermally unstable compounds, as it uses a liquid mobile phase and a lower temperature.3 However, using an inert gas as the mobile phase means limited interaction between the mobile phase and the analyte or detector, and it can operation at a lower pressure, making GC a simpler method than HPLC.4[pic 3][pic 4]

Mass spectrometry is an analytical technique which uses ionization to measure the charge-to-mass ratio of a compound to identify and quantify it. After the analyte passes through the GC column, it is bombarded by a stream of electrons from an ion source. These electrons ionize the species by knocking off electrons, yielding a positive ion. The ions then pass through the quadrupole mass analyzer (QMS), which separates then by their charge-to-mass ratio (m/z). The QMS consists of two positively and two negatively charged rods that oscillate at a certain frequency such that the ions travel in a corkscrew path.4 Ions with a specific m/z will reach the detector at the end of the rods, while other ions will have unstable trajectories and will collide with the rods or escape from between them. Thus, by varying the applied voltage, the mass spectrometer can plot the detector signal against m/z to identify and quantify compounds. Previous applications of GC/MS include the detection of mycobacterium xenopi in drinking water7, analysis of benzodiazepines in blood and urine8, and determination of pesticide levels in organic honey9. [pic 5][pic 6]

GC/MS is an ideal tool for the analysis of phthalates because they are easily separated from the plastic matrix and are thermally stable and volatile.3 No internal standard was used in this study because it is difficult to separate one from such a complex mixture chromatographically. Standard solutions of phthalates and dog toy sample were quantified and identified by GC/MS. The peak areas of the standard solutions were plotted against relative concentrations to generate a calibration curve for each phthalate. This calibration curve was used to quantify the amount of phthalates in a dog toy sample.

Materials

Dichloromethane (≥ 99.9%) was purchased from Sigma Aldrich. EPA 8270 Phthalate Mixture (2000 μg/mL in methylene chloride) containing bis(2-chloroethyl)ether, bis(2-chloroisopropyl)ether, bis(2-chloroethoxy)methane, dimethyl phthalate, diethyl phthalate, 4-chlorophenylphenyl ether, 4-bromophenylphenyl ether, di-n-butyl phthalate (DBP), butyl benzyl phthalate (BBP), bis(2-ethylhexyl)phthalate (DEHP), and di-n-octyl phthalate (DnOP) was purchased from Supelco Analytical. Diisonyl phthalate (≥0.99%) and diisodecyl phthalate (≥0.99%) was purchased from Sigma Aldrich. The dog toy was provided by the University of Pittsburgh. All standard and sample solutions were prepared using dichloromethane and filtered through a 0.45-micron PTFE syringe filter provided by the University of Pittsburgh.

Instrumentation

A PerkinElmer Clarus 600 GC/MS equipped with a split injector and a PerkinElmer Elite-5MS (5% diphenyl/95% dimethyl polysiloxane, 30 m x 0.25 mm x 0.25 μm) GC column was used to analyze all standard and sample solutions. The column was temperature programmed from 100°C to 260°C at 8°C/min, then to 320°C at 35°C/min. TurboMass Software was used for data collection. The GC conditions was set according to the following parameters: injector port temperature 280°C, split injection 25 mL/min, syringe volume 5 μL, injection volume 1 μL, and normal injection speed. Methylene chloride was used as the rinse solvent. Helium was used as the carrier gas at a flow rate of 2 mL/min for 0.5 min and then 1 mL/min. The MS was operated in fullscan mode and set according to the following parameters: GC inlet temperature 280°C, ion source temperature 280°C, full scan m/z range of 45–300, full scan time 0.15 seconds, interscan delay 0.05 seconds, and a 3-minute solvent delay.