taleranol in meat and liver Page : 1 of 9 1. INTRODUCTION 1.1 Summary This SOP describes a screening and confirmation method for the determination of resorcyclic acid lactones (RAL s) in meat and liver samples of bovine origin. A procedure is described for the detection of α-zearalanol (zeranol) and β-zearalanol (taleranol) by a combination of solid phase extraction (SPE) and GC-MS. The method consist of, digestion of the meat sample using the enzyme protease and hydrolysis of the liver sample using suc d Helix Pomatia, extraction of the RAL s with tert-butylmethylether (TBME), purification using reversed-phase C 18 cartridges. This method can also be used for the metabolites α-zearalenol, β-zearalenol, zearalanone and zearalenone. When doing so validation for these compounds is necessary. 1.2 Field of application The method is used to perform routine screening in meat and liver samples and has proven to be suitable for the analysis of α-zearalanol and β-zearalanol. The limit of detection is 0.5 µg/g based on the detection of the most abundant diagnostic ions namely m/z 433 and m/z 437 for the internal standard, with a response at the correct retention time exceeding the signal to noise ratio of 3. The method is validated according to SOP ARO/425 (1.3.3). 1.3 References 1.3.1. H.J. van Rossum et al, Multi residue analysis anabolic agents, SOP ARO/113, revision 4, 21 January 1997, RIVM. 1.3.2. H.A. Herbold, S.S. Sterk, R.W. Stephany, L.A. van Ginkel. Multi residue method using coupled-column HPLC and GC-MS for the determination of anabolic agents in samples of urine. RIVM report n.389002-035, September 1997. 1.3.3. A.A.M. Stolker, Procedure for the validation of analytical methods, SOP ARO/425, revision 1, 28 April 1997, RIVM. 1.3.4. Report: European Commission Decision laying down requirements for analytical methods to be used for detecting certain substances and residue thereof in live animals and animal products according to Council Directive 93/256/EC. 1.3.5 S.M. Gort and R. Hoogerbrugge, Linear regression program Calwer. Report RIVM no. 502501025. A spreadsheet program for calibration. March 1995. 2. MATERIALS Reference to a company and/or product is for purposes of identification and information only and does not imply approval or recommendation of the company and/or the product by the National Institute of Public Health and Environment (RIVM) to the exclusion of others which might also be suitable.
taleranol in meat and liver Page : 2 of 9 2.1 Chemicals 2.1.1 SPE extraction columns, 6 ml, 1 g, disposable octadecyl (C18) (Alltech, 205430). 2.1.2 SPE extraction columns, 6 ml, 1 g, disposable amino (NH2) (Alltech, 211153). 2.1.3 Methanol (Baker, 8045). 2.1.4 Ethanol (Baker, 8006). 2.1.5 Acetone (Baker, 8001). 2.1.6 Iso-octane (Baker, 8715). 2.1.7 Derivatization reagent: N,O-bis(trimethylsilyl)trifkuoracetamide (BSTFA) with 1% TMCS (Pierce, 38832). 2.1.8 Acetic acid (Merck, 63). 2.1.9 Sodium acetate (Merck, 6268). 2.1.10 Hydrochloric acid, 37% solution (Merck, 317). 2.1.11 Beta-glucuronidase/sulfatase (suc d'helix Pomatia containing 100.000 units ß-glucuronidase and 100.000 units sulfatase per ml, France, code IBR 213473. 2.1.12 Acetate buffer, 2 mol/l, ph 5.2 Dissolve 25.2 g acetic acid and 129.5 g sodium acetate in 800 ml water. Adjust the ph to 5.2 ± 0.1, add water to a final volume of 1000 ml. 2.1.13 Tris buffer, 0.1 mol/l, ph 9.5. Dissolve 12.1 g of Tris(hydroxymethyl)-amino-methane (2.1.16) in 800 ml of water. Adjust the ph (5.5.18.) at 9.5 ± 0.1 and add water to a final volume of 1000 ml. 2.1.14 Tert-butylmethylether (TBME) (Merck, 1845). 2.1.15 Subtilisin (Protease) (Sigma, P-5380). 2.1.16 Tris(hydroxymethyl)-amino-methane (Merck, 8382) 2.2. Relevant Internal Standards 2.2.1 α-zearalanol-d4 and β-zearalanol-d4 The analytes are a mixture of ± 50% of each compound. RIVM/ARO sample no. 87M1553. From these a standard stock solution containing 1 mg/ml is prepared. The stock solutions is prepared by dissolving the appropriate amount of the analytes in ethanol. Quality control includes the registration of a mass spectrum (identity). These solutions are stored in the dark at -20 C for a maximum period of 5 years. Working solutions are prepared by 10-fold dilution of the stock solutions with methanol. These solutions are stored in the dark at 4 C (range 1-10 C) for a maximum period of 6 months. 2.2.2 α-zearalanol and β-zearalanol Relevant data of the analytes are listed in table 1. Stock solutions containing 1 mg/ml are prepared by dissolving the appropriate amount of the analytes in ethanol. Quality control includes the registration of a mass spectrum (identity). These solutions are stored in the dark at -20 C for a maximum period of 5 years. Working solutions are prepared by 10-fold dilution of the stock solutions with methanol. These solutions are stored in the dark at 4 C (range 1-10 C) for a maximum period of 6 months. Table 1. Data of analytes. Analytes CAS # Formula Mol. weight α-zearalanol 26538-44-3 C 18 H 26 O 5 322.4 β-zearalanol 42422-68-4 C 18 H 26 O 5 322.4
taleranol in meat and liver Page : 3 of 9 2.3 Equipment 2.3.1 ASPEC (Automated Sample Preparation with Disposable Extraction Columns) XL Gilson. The ASPEC consists of three components: a model 401C dilutor, a sample processor and a set of racks and accessories to handle 6 ml SPE columns. The ASPEC is programmed using the Gilson Sample Manager 721 software. 2.3.2 Collecting tubes for the ASPEC system, Gilson type B54728-4. 2.3.3 Derivatization vials, Screw Top Vial /PTFE Septa (Omnilabo, 154920). 2.3.4 Automatic pipettes (Gilson P20, P100, P200, P1000 and P5000). 2.3.5 Injection vials, Wide Mouth Crimp (Alltech, 98213), with micro inserts (200 ml) (Alltech, EK-1022.395) and aluminium caps (Chrompack, 10210). 2.3.6 GC-MS equipment. Hewlett Packard 5890 series 11 gaschromatograph, equipped with a Hewlett Packard 7673 automatic sampler, a Hewlett Packard Vectra computer 486/66U with HPchem data acquisition software and a 5989A Mass Spectrometer (type Engine). 2.3.7 Fused silica capillary column CP SIL-5, Low bleeding/non polar, length 60 m, i.d. 0.25 mm, 0.1 micron film thickness, (Chrompack, 7818). 2.3.8 Vortex (Vortex-Genie). 2.3.9 ph-meter, (Applikon). 2.3.10 Moulinette S (Moulinex). 2.3.11 Electric water bath, thermostat adjustable ± 5 C, with nitrogen facility (TurboVap, Zymark). 2.3.12 Varifuge 3.0R, centrifuge with swing-out rotor 5315 (Heraeus). 2.3.13 Centrifuge tubes (50 ml), plastic (Omnilabo) 2.3.14 Incubator TH15, (Edmund Bühler). 3. GC-MS CONDITIONS Table 2: Parameters GC-MS Carrier gas helium 0.6 ml/min (EPC system for constant flow) Column 60 meter CP-SIL-5 Low Bleeding/non polar fused silica capillary (0.25 mm i.d. 0.1 µm film) Detector temperature 250 o C MS-source, 120 o C quadruple. Oven temperature 80 o C for 1 min, increased at 30 o C/min. to 300 o C and held at this temperature for 5 min. Ionisation EI - positive, SIM mode Injection volume 3 µl Pressure Electronic Pressure Control syst. Pressure is held at 50 psi for 1 minute, decreased at 99 psi/minute to 28.4 psi, constant during the oven-temperature program Mass monitored 433, 437 (internal standard) Tune High mass/sensitivity tune.
taleranol in meat and liver Page : 4 of 9 4. ANALYTICAL PROCEDURES 4.1 Sample pre-treatment Meat and liver (1 kg) is crushed and homogenised in a Moulinette S (Moulinex). A test portion of 5.0 g is weighted into a 50 ml centrifuge tube, spiked with a mixture of internal standards (α-zearalanol-d4 and β-zearalanol-d4) at the level of 10 ng (corresponding to 2 ng/g). 4.1.1 Meat samples For digestion, 10 ml volume of Trisbuffer (2.1.13) and 5 mg subtilisin (2.1.15) is added. The mixture is vortexed for 30 seconds and shaken thoroughly for two hours at 50 o C. 4.1.2 Liver samples For hydolysis, 40 µl of Suc Helix Pomatia (2.1.11), diluted with 10 ml 2 M acetate buffer (ph 5.2) (2.1.12) is added. The mixture is vortexed for 30 sec., check ph 5.2 (when necessary adjust the ph with acetic acid to 5.2) and hydrolyse overnight at 37 o C, with constant shaking by means of an incubator equipped with a shaker. 4.2 Liquid/liquid extraction To the mixture (4.1) 2 ml conc. HCl and 10 ml TBME is added, shake for 10 minutes and centrifuge for 3 minutes at 3600 rpm. The organic layer is collected in a glass tube. This operation is repeated with 5 ml TBME. The extract in the glass tube is evaporated at 50 o C under a gentle stream of nitrogen. The dry residue is dissolved in 5 ml of MeOH/milli-Q water (40-60) and washed twice with 1 ml hexane (each time centrifuged for 3 minutes at 3600 rpm). The hexane layer is separated from the MeOH-water fraction and discarded. The MeOHwater layer in the tube is cleaned over C18 disposable column (SPE). 4.3 SPE Chromatography 4.3.1 Meat The C18 column (6 ml) is preconditioned with 5 ml of MeOH and 5 ml milli-q water at a flow rate of 6 ml/min. The sample (4.2) is passed through the column. The C18 column is washed with 5 ml of milli-q water and a mixture of 4 ml of MeOH/milli-Q water (40-60). The analytes for meat are eluted with 3 ml of acetone (for liver see 4.3.2). This eluate is collected and evaporated at 50 o C under a gently stream of nitrogen, until dryness and dissolved in 0.5 ml MeOH. 4.3.2 Liver An extra cleanup step with NH2 amino disposable column (SPE) is necessary. The NH2- column is preconditioned with 3 ml acetone and the collected eluate (3 ml of acetone) is passed through the amino column. This eluate is collected and evaporated at 50 o C under a gently stream of nitrogen, until dryness and dissolved in 0.5 ml MeOH. 4.4 Detection The extract (4.3) is transferred into a derivatization-vial and evaporated at 50 o C under a gently stream of nitrogen until dryness. The dry residue is derivatized with 20 µl BSTFA. The derivatization-vials are placed in a heater at 60 o C for about 30 minutes. Evaporate at 50 o C under a stream of nitrogen until dry and dissolve in 20 µl iso-octane and transfer into an injection-vial with micro insert. The 7673 automatic sampler injects 3 µl of these extracts into the GC-MS and measures the diagnostic ions 433 and 437 in the SIM-mode.
taleranol in meat and liver Page : 5 of 9 5 INTERPRETATION AND CALCULATION 5.1 Checks The first step in interpreting the results is to check for: - Adequate performance characteristics of the GC-MS system (MS-tuning). - Adequate sensitivity for external derivatized standards (S/N α-zearalanol-d4 [3.0 ng absolute] > 6). - Adequate signals for internal standard in sample (S/N α-zearalanol-d4 [2 ppb] > 3). 5.2 Calculation of quantitative results Quantitative results are obtained by constructing calibration curves of the response variable versus the concentration. Quantification is only valid if: - The maximum of the signal originating from the analyte has a S/N ratio > 3. - The coefficient of correlation of the constructed calibration curve is better than 0.99. - The numerical value of the intercept does not deviate more than ± 3 SD from zero. Calibration curves are calculated using calibration software Calwer, option linear regression (1.3.5). 5.3 Calculation in case of deuterated internal standard When for the analyte concerned the corresponding deuterated internal standard was added to the test portion, quantification is straight forward. The area of the selected ion of the standard and internal standard are calculated and the ratio is the response variable. A calibration curve is constructed by analysing different concentrations of standard in range of the inspected concentration in the sample. A linear curve is fitted using least squares linear regression calculation. Unknown concentrations are calculated by interpolation. 5.4 Identification For identification according to the EC-criteria it is mandatory that the GC retention time corresponds with the retention time of the internal standard and that at least 4 ions are monitored. Each ion monitored (response) should fulfil the criterion that the S/N ratio of the maximum exceeds a value of 3. The ratio of the analyte s retention time to that of the internal standard (relative retention time), should correspond to that of the calibration standard at a tolerance of ± 0.5%. The relative intensities of the detected ions, expressed as a percentage of the intensity of the most intense ion (base peak) must correspond to those of the standard analyte, either from calibration standards or from spiked samples, at comparable concentrations, within the following tolerances (table 3). Table 3: Maximum permitted tolerances for relative ion intensities. Relative intensity compared to base peak. (Ratio in % of base peak) Relative error compared to calibration standard. > 50% ± 10% > 20% - 50% ± 15% > 10% - 20% ± 20% 10% ± 50%
taleranol in meat and liver Page : 6 of 9 6. VALIDATION OF METHOD 6.1 Reproducibility The reproducibility, definitions and criteria according to European Commission decision 93/256/EC, determined at the level of 1 ppb, on 5 different days in triplate. Internal standard at 2 ppb level. Table 4: Results reproducibility. Matrix α-zearalanol β-zearalanol Average (%) STD VC(%) Average (%) STD VC(%) Liver 94 19 21 102 31 30 Meat 108 18 17 112 20 17 6.2 Limit of detection The limit of detection is the amount of the analyte which is necessary for a signal/noise of 6 (S/N). Samples of 5.0 g liver (or meat) are spiked with a mixture of internal standards (αzearalanol-d4 and β-zearalanol-d4) at the level of 2 ppb and spiked with a mixture of α- zearalanol and β-zearalanol at the level of 0.2, 0.5, 1.0, 2.0 ppb. In this case, the limit of detection for liver and meat is given at 0.5 ppb and the signal/noise is 6. 6.3 Accuracy A sample of 5.0 g is spiked with a mixture of internal standards (α-zearalanol-d4 and β- zearalanol-d4) at the level of 2 ppb and spiked with a mixture of α-zearalanol and β- zearalanol at the levels 0.2, 0.5 and 1 ppb, in triplo.(the yield must be > 80%). (Results see table 5) Table 5: Results accuracy. Matrix α-zearalanol β-zearalanol Average (%) STD VC(%) Average (%) STD VC (%) Liver 85.8 15.6 18.1 100.7 22.2 22.1 Meat 116.9 24.9 21.3 98.6 24.1 24.5 6.4 Repeatability The repeatability is determined at the level of 1 ppb by spiking a blank sample and measuring it 10 times. Samples of 5.0 g liver (or meat) are spiked with a mixture of internal standards (α-zearalanol-d4 and β-zearalanol-d4) at the level of 2 ppb and spiked with a mixture of α- zearalanol and β-zearalanol at the level of 1.0 ppb (10 times). Results see table 6. Table 6: Results repeatability. Matrix α-zearalanol β-zearalanol Average (%) STD VC(%) Average (%) STD VC(%) Liver 93.8 13.8 14.8 96.7 22.0 22.8 Meat 107.4 24.5 22.8 117.4 15.9 13.6
taleranol in meat and liver Page : 7 of 9 6.5 Ruggedness The ruggedness of a method can be estimated by measuring the effects of changes in external conditions. In this case, 5 different blank liver samples are spiked at the level of 1 ppb and a mixture of internal standards (α-zearalanol-d4 and β-zearalanol-d4) at the level of 2 ppb. Results see table 7. Table 7: Results ruggedness. Matrix α-zearalanol β-zearalanol Average (%) STD VC(%) Average (%) STD VC(%) Liver 67.8 14.8 21.8 102.4 22.5 22.0 Meat 106.6 8.3 7.8 110.0 19.1 17.4 6.6 Recovery For the absolute recovery of the method, samples of 5.0 g (liver or meat) is spiked with a mixture of α-zearalanol and β-zearalanol at the level of 1.0 ppb (3 times) and after clean-up with a mixture of internal standards (α-zearalanol-d4 and β-zearalanol-d4) at the level of 2 ppb. Results see table 8. Table 8: Results recovery. Matrix α-zearalanol β-zearalanol Average (%) STD VC(%) Average (%) STD VC(%) Liver 47.0 8.0 17.0 54.7 13.7 25.0 Meat 16 1.0 6.0 22 0.6 2.6
taleranol in meat and liver Page : 8 of 9 7. CHROMATOGRAM LIVER SAMPLE Figure 1: Blank liver sample. Internal standard m/z 437 (2 ppb). Ion 433.00 (432.70 to 433.70): 99020294.D 1000 950 900 11.00 11.05 11.10 11.15 11.20 11.25 11.30 11.35 11.40 11.45 Ion 437.00 (436.70 to 437.70): 99020294.D 11.17 11.25 1500 1000 11.00 11.05 11.10 11.15 11.20 11.25 11.30 11.35 11.40 11.45 Figure 2: Spiked liver sample, level 1 ppb. Diagn. ions m/z 433, 437 (internal st. 2 ppb) Ion 433.00 (432.70 to 433.70): 99020295.D 11.19 11.26 1800 1600 1400 1200 1000 11.05 11.10 11.15 11.20 11.25 11.30 11.35 11.40 11.45 Ion 437.00 (436.70 to 437.70): 99020295.D 11.17 11.25 1500 1000 11.05 11.10 11.15 11.20 11.25 11.30 11.35 11.40 11.45
taleranol in meat and liver Page : 9 of 9 Figure 3: Blank meat sample. Internal standard m/z 437 (2 ppb). Ion 433.00 (432.70 to 433.70): 98122370.D 2800 2600 2400 2200 10.60 10.70 10.80 10.90 11.00 11.10 11.20 11.30 11.40 Ion 437.00 (436.70 to 437.70): 98122370.D 8000 7000 6000 5000 11.09 11.19 4000 3000 10.60 10.70 10.80 10.90 11.00 11.10 11.20 11.30 11.40 Figure 4. Spiked meat sample, level 1 ppb. Diagn. ions m/z 433, 437 (internal st. 2 ppb) Ion 433.00 (432.70 to 433.70): 98122371.D 5000 11.10 11.20 4500 4000 3500 3000 2500 10.60 10.70 10.80 10.90 11.00 11.10 11.20 11.30 11.40 Ion 437.00 (436.70 to 437.70): 98122371.D 7500 11.09 7000 6500 6000 5500 11.19 5000 4500 4000 3500 3000 2500 10.60 10.70 10.80 10.90 11.00 11.10 11.20 11.30 11.40