GAFTI Analytical method for ISO/TS 16179:2012 Detection and Determination of Organotin Compounds in Footwear and Apparel Materials by GC-MS

Transcription

1 GAFTI Analytical method for ISO/TS 16179:2012 Detection and Determination of Organotin Compounds in Footwear and Apparel Materials by GC-MS 1. Scope This method is applicable for determining the presence of organotin compounds in all types of footwear materials. This test method is also applicable to apparel materials. 2. Definition 2.1 GC/MS: Gas Chromatography with Mass Spectrometer 2.2 MBT: Monobutyltin 2.3 MOT: Monooctyltin 2.4 DBT: Dibutyltin 2.5 DOT: Dioctyltin 2.6 TBT: Tributyltin 2.7 TPhT: Triphenyltin 2.8 TCyT: Tricyclohexyltin 2.9 TeBT: Tetrabutyltin 2.10 MHT: Monoheptyltin (IS) 2.11 DHT: Diheptyltin (IS) 2.12 TPT: Tripropyltin (IS) 2.13 TePrT: Tetrapropyltin (IS) 2.14 NaBEt 4 : Sodium tetraethylborate 2.15 THF: Tetrahydrofuran 2.16 D.I. water: Deionized water 2.17 IS: Internal standard Page 1 of 8

2 3. Principle The organotin substances are extracted from the footwear material with a methanol-ethanol mixture in a medium-strength acidic condition, using tropolone as a complexant agent. The polar and high-boiling organotin is then converted to the corresponding volatile tetra-alkyl derivative, by reaction with sodium tetraethylborate, NaB(Et) 4. Finally, it is detected by a gas chromatograph fitted with a mass selective detector (GC-MS). 4. Reagents 4.1 Ethanol absolute, purity 99.8%, or equivalent 4.2 Methanol, purity 99.9%, or equivalent 4.3 Methanol-ethanol mixture (80/20 v/v): Mix 800mL methanol and 200mL ethanol. 4.4 Sodium acetate, analytical grade or above 4.5 Glacial acetic acid, analytical grade or above 4.6 Tropolone, CAS No.: , analytical grade or above 4.7 Isooctane (2,2,4-trimethylpentane), CAS No.: , analytical grade or above 4.8 Sodium tetraethylborate (NaBEt 4 ), CAS No.: , purity 98% or above Note: Pure NaBEt 4 is an off-white powder. It is pyrophoric, air and moisture sensitive. It should be kept inside desiccators. 4.9 Tetrahydrofuran (THF), analytical grade or above 4.10 Monobutyltin trichloride, C 4 H 9 SnCl 3, CAS No.: , analytical grade or 4.11 MonoOctyltin-trichloride, C 8 H 17 SnCl 3, CAS No.: , analytical grade or 4.12 Dibutyltin dichloride, (C 4 H 9 ) 2 SnCl 2, CAS No.: , analytical grade or 4.13 Dioctyltin-dichloride, C 16 H 34 SnCl 2, CAS No.: , analytical grade or 4.14 Tributyltin chloride, (C 4 H 9 ) 3 SnCl, CAS No.: , analytical grade or 4.15 Triphenyltin chloride, (C 6 H 5 ) 3 SnCl, CAS No.: , analytical grade or Page 2 of 8

3 4.16 Tricyclohexyltin chloride, (C 6 H 11 ) 3 SnCl, CAS No.: , analytical grade or 4.17 Tetrabutyltin, (C 4 H 9 ) 4 Sn, CAS No.: , analytical grade or 4.18 Monoheptyltin trichloride, C 7 H 15 SnCl 3, CAS No.: , analytical grade or 4.19 Diheptyltin dichloride, (C 7 H 15 ) 2 SnCl 2, CAS No.: , analytical grade or 4.20 Tripropyltin chloride, C 9 H 21 SnCl, CAS No.: analytical grade or 4.21 Tetrapropyltin, (C 3 H 7 ) 4 Sn, CAS No.: , analytical grade or 4.22 Deionized water (D.I. water), at least grade 3 purity in accordance with ISO Preparation of ph 4.5 buffer solution Weigh 16.4g sodium acetate in 1L of D.I. water and adjust with glacial acetic acid to reach a ph of 4.5 measured by ph meter Preparation of tropolone solution Weigh 0.500g of tropolone into a glass beaker and dissolve in approximately 20mL of methanol. Dilute to 100mL in a volumetric flask Preparation of Sodium tetraethylborate (NaBEt 4 ) derivatization agent Using inert gas supply or appropriate inert conditions, weigh 200mg of NaBEt 4 into an amber vial. Transfer 1mL of THF into the vial and mix the solution until all NaBEt 4 dissolves. Note 1: The amount of derivatizing agent prepared can be adjusted according to sample volume. Note 2: This solution is not stable, and shall be prepared daily fresh, or kept at -18 o C for maximum 3 months. 5. Apparatus 5.1 Gas Chromatography equipped with Mass Selective Detector (GC/MSD) 5.2 Analytical balance 5.3 GC capillary column, DB-5MS (30m x 250 µm x 0.25 µm thickness), or equivalent 5.4 ph meter 5.5 Mechanical shaker 5.6 Ultrasonic bath 5.7 Auto-pipette Page 3 of 8

4 5.8 Micro syringe 5.9 Culture tube with PTFE lined screw cap, 30mL 5.10 Vial with PTFE liner screw cap, 50 ml 5.11 Centrifuge 5.12 ph paper, ph Glass volumetric flask 5.14 Glass pipette 5.15 GC vial, 2mL 6. Standard preparation 6.1 Preparation of 1000mg/L organotin cation individual stock standard: Use analytical balance to weigh the appropriate amount of chemicals or following below table and dissolve in methanol in individual volumetric flask. Analyte Chemicals Amount (mg) Final volume in methanol (ml) MBT Monobutyltin trichloride (MBTCl 3 ) MOT Monooctyltin trichloride (MOTCl 3 ) DBT Dibutyltin dichloride (DBTCl 2 ) DOT Dioctyltin dichloride (DOTCl 2 ) TBT Tributyltin chloride (TBTCl) TPhT Triphenyltin chloride (TPhTCl) TCyT Tricyclohexyltin chloride (TCyTCl) TeBT Tetrabutyltin (TeBT) Weighing factor = molar mass (organic tin cation) / molar mass (organic tin chloride). 6.2 Preparation of 1000mg/L organotin cation individual internal standard (IS) stock solution: Use analytical balance to weigh the appropriate amount of chemicals or following below table and dissolve in methanol in individual volumetric flask. Page 4 of 8

5 Organotin Chemicals Amount (mg) Final volume in methanol (ml) MHeT DHeT TPT Monoheptyltin trichloride (MHeTCl 3 ) Diheptyltin dichloride (DHeTCl 2 ) Tripropyltin monochloride (TPTCl) TePrT Tetrapropyltin (TePrT) Preparation of 10mg/L organotin cation mix standard solution from 1000mg/L individual stock standard: Pipette 100 µl of each individual 1000 mg/l stock standard to a 10 ml volumetric flask, and mark up with methanol. 6.4 Preparation of 1mg/L organotin cation mix working standard solution from 10mg/L mix stock standard: Dilute 500µL of 10mg/L mix standard with methanol in 5mL volumetric flask, and make up to the mark with methanol. 6.5 Preparation of 10mg/L mix IS solution Pipette 100 µl of each individual 1000 mg/l IS stock standard to a 10 ml volumetric flask, and mark up with Methanol. 6.6 Preparation of calibration standards Add the specified volume of 1mg/L mix working standard into each of 5 vials according to the following table. Parameter Volume of 1mg/L mix working standard added (µl) Page 5 of 8 Concentration of the calibration standard in the 2mL isooctane (mg/l) Calibration point Calibration point Calibration point Calibration point Calibration point Note: The calibration points should cover 0.02 mg/l to 0.5 mg/l. The actual intermediate points are subject to change upon the need of laboratory.

6 6.6.2 Add 20mL of methanol-ethanol mixture, 100µL of 10mg/L mix IS solution, 1mL of tropolone solution and 8mL of buffer solution at ph 4.5. Then follow clause 7.8 to Sample preparation 7.1 Weigh 1g of sample (cut in size of <4mm x 4mm) into an appropriate size screw-cap vessel (e.g. 30 ml). 7.2 Pipette 20 ml methanol/ethanol (8:2) into the vessel. 7.3 Add 100 ul Internal standard and 1 ml tropolone solution. 7.4 Extract the sample in ultrasonic bath at 60 o C for 1 hr. 7.5 Allow the extracts to cool to room temperature. Transfer the clear extracts to another screw-cap vial (e.g. 50 ml). Note: Centrifuge at 3000r.p.m for 5min, if needed. 7.6 Rinse with 2mL methanol-ethanol mixture and combine. 7.7 Add 8 ml buffer solution at ph Add 100µL NaBEt 4 solution to the extract solution, and shake vigorously for 30 min by mechanical shaker. (The shaking speed of 200r.p.m can be taken as a reference). 7.9 Add 2.0mL of isooctane into the vial and shake vigorously for another 30 min by mechanical shaker Left to stand until phase separation is completed. (For a better separation, centrifugation at 4000r.p.m can be used) Transfer the upper isooctane layer into a 2mL vial for GC/MS analysis Quality control samples Prepare method blank sample, blank or sample spike quality control samples where appropriate. 8. GC-MS Instrumental Analysis 8.1 Set up the instrument with reference to Annex A of ISO/TS 16179:2012. The conditions are subject to the need of the laboratory. The following is given as example: Acquisition Mode SIM-SCAN mode Injection Mode Splitless Injection Volume 1 µl Page 6 of 8

7 Injector Temperature 260 C Column DB-5MS, 30m x 250µm, 0.25µm thickness or equivalent Carrier Gas Helium Flow control mode Constant flow Flow Rate 1 ml/min Initial Temperature 60 C hold for 4 min Temperature Program 20 C / min to 300 C hold for 6 min; Total run time 22min Aux Temperature 310 C Scan range m/z SIM setting of the GC-MS The SIM setting can be referred to Annex A of of ISO/TS 16179:2012. The setting is subject to the need of the laboratory The following is given as reference for setting up SIM ions for different target compounds. Select one ion for quantitation and two other ions for qualification from the three groups for each target compound. Separate these ions into interval groups where appropriate. Substance IS Group Group 1 ion (m/z) Group 2 ion (m/z) Group 3 ion (m/z) MHeT (IS) 1 277/ / /149 MBT 1 235/ / /149 MOT 1 291/ / /149 DHeT (IS) 2 347/ / /149 DBT 2 263/ / /149 DOT 2 375/ / /149 TPT (IS) 3 249/ / /191 TBT 3 291/ / /177 TPhT 3 351/ / TCyT 3 233/ / /367 TePrT (IS) 4 249/ / /205 TeBT 4 291/ / / Run the calibration solution to the GC/MS to develop a calibration curve for each organic tin cation. 8.4 Establish internal calibration curve for each organic tin cation using Peak area vs Page 7 of 8

8 Conc against internal standard. The coefficient of linear regression (r) should be Inject the standard check solution (at appropriate concentration within the calibration curve) to the GC/MS, with recovery within ±15%. 8.6 Inject quality control samples to check for recovery, and then inject samples. 8.7 Identify the target compounds by matching the retention times for samples and calibration. 8.8 One quantification ion, two qualification ions and the full mass spectra are used for the detection of the target compounds. 9. Calculations and Results The single organotin content in sample is calculated as follow: C V Organotin cation content (mg/kg) = x DF W where C is the instrument concentration of the analyte quantified against internal standard, mg/l, V is the final volume of sample solution, ml W is the weight of sample used, g. DF is the dilution factor, if any Reporting limit of this method = 0.2 mg/kg* * Composite test for 3in1 mix is allowed upon client request 10. Test report The test report shall include, at least, the following: 10.1 All details necessary for complete identification of the sample tested; 10.2 Starting and completion dates of test; 10.3 The test result (in organotin cation) in the unit of mg/kg; 10.4 Any deviation, by agreement or otherwise, from the procedure specified. Page 8 of 8