Determination of Iodinated Contrast Media in Aqueous Samples by Direct-Injection LC-MS/MS Application Note Environmental Authors Abstract Gerd Vanhoenacker, Mieke Steenbeke, Determination of iodinated contrast media in aqueous samples was performed by Frank David, and Pat Sandra fast chromatography on an Agilent 1290 Infi nity II LC that included an Agilent 1290 Research Institute for Chromatography Infi nity II Multisampler equipped with a 100 µL analytical head and loop cartridge. President Kennedypark 26 Detection was done with an Agilent 6495 Triple Quadrupole LC/MS. With this B-8500 Kortrijk confi guration, it was possible to detect the contrast agents at the low ng/L parts Belgium per trillion (ppt) level in water without any pretreatment except fi ltration. The method was developed for seven target contrast agents, and the performance Udo Huber and fi gures of merit were investigated on standard solutions as well as on various Agilent Technologies, Inc. water samples. Waldbronn, Germany Introduction The analysis of ICMs in the environment This Application Note describes the use has gained considerable interest over the of the Agilent 6495 Triple Quadrupole Iodinated contrast media (ICMs) are last decade. Earlier approaches measured LC/MS in combination with the globally used for medical X-ray imaging. the total absorbable organic iodine (AOI), Agilent 1290 Infi nity II LC for the direct These iodine-based chemicals are whereas recent methods focus on the analysis of selected ICMs (Figure 1) in administered intravascularly, and absorb sensitive detection of individual ICMs water samples at low ng/L (ppt) levels. X-rays in vessels and tissues, enhancing and potential degradation products by Direct injection of water samples without the visibility of internal structures. LC-MS and LC-MS/MS1-4,8. These polar any pretreatment except fi ltration was Several ICMs are available. This class and sometimes acidic compounds can applied. Relatively large volumes need to of pharmaceuticals is one of the most suffer from bad peak shapes in LC, and be injected, requiring adequate control of frequently used groups of chemicals the chromatographic parameters need the separation conditions. State-of-the-art applied in hospitals, and generally at to be carefully chosen. To meet low mass spectrometry offers high sensitivity, relatively high doses1. ng/L (part per trillion, ppt) detection allowing direct analysis of trace Signifi cant levels can be found in various limits, an extraction step such as contaminants in water. This reduces time aqueous matrices (hospital wastewater1-3, solid-phase extraction (SPE) is commonly and cost per analysis, and minimizes 1,9 surface water2, ground water4,5, and performed . errors that can be made during sample even drinking water5), and soil6. Studies pretreatment. have demonstrated that complete ICM removal in wastewater treatment plants OH OH is diffi cult or even impossible with state-of-the-art water treatment methods OH H O NH such as ozonation, UV irradiation, O N OH chlorination, microbial degradation, I I I I OH 1,2 OH H O and so on . Consequently, they are H O N OH frequently detected at signifi cant levels HO N OH N N H in wastewater treatment plant effl uents. O I O I HO Moreover, potentially toxic iodine derivatives can be formed and released Iomeprol Iopamidol 7 into the environment upon treatment . OH H OH O N OH H O N OH I I OH H O I I OH HO N O N HO N O O N I OH H O I OH Iohexol Iopromide H O OH N O O OH I I I I II O O H O H O N N HO N N N N H H H O I O I I Ioxaglic acid Diatrizoic acid O OH I I H O N HNO H O I Ioxitalamic acid Figure 1. Structures of the studied ICMs. 2 Experimental Method parameters Instrumentation Parameter Description An Agilent 1290 Infi nity II LC and an Mobile phase A) 0.1 % (v/v) acetic acid in water Agilent 6495 Triple Quadrupole MS with B) Acetonitrile an Agilent Jet Stream technology source Flow rate 0.4 mL/min were used. The 1290 Infi nity II LC was Gradient 0 to 1 minutes – 0 %B confi gured as follows: 1 to 5 minutes – 0 to 73 %B 5 to 5.5 minutes – 73 to 95 %B • Agilent 1290 Infi nity II High Speed 5.5 to 7 minutes – 95 %B Pump (G7120A) with a 35 µL Jet Post time 3 minutes at 0 %B Weaver mixer Temperature 15 °C Injection 100 µL, with needle wash (fl ush port, 5 seconds, water/methanol 1/1) • Agilent 1290 Infi nity II Multisampler (G7167B) Detection parameters with analytical head 100 µL Parameter Description (G4267-60043) and sample Mode MS/MS loop-fl ex 100 µL (G4267-60500) Ionization Electrospray, positive ionization • Agilent 1290 Infi nity II Multicolumn Drying gas temperature 220 °C Thermostat (G7116B) with an Drying gas fl ow 13 L/min Agilent Infi nityLab Quick Connect Nebulizer pressure 40 psig heat exchanger assembly for Sheath gas temperature 390 °C standard fl ow (G7116-60015), Sheath gas fl ow 11 L/min Infi nityLab Quick Connect fi ttings Capillary voltage 3,500 V 0.12 × 105 mm (5067-5957), and Nozzle voltage 1,600 V an Agilent ZORBAX Eclipse Plus Dynamic MRM See Table 1 C18 RRHD, 2.1 × 150 mm, 1.8 µm Delta EMV 200 column (959759-902) Cycle time 200 ms 0 to 3 minutes – Waste 3 to 5 minutes – MS 5 minutes to end – Waste 3 Table 1 shows the acquisition parameters Separate stock solutions of the standards Water samples were stored at 4 °C. After for the selected ICMs. and internal standards were prepared removal from the refrigerator, they were in methanol/water 50/50 v/v at 5 and allowed to reach room temperature, Solutions and samples 1 mg/L (ppm), respectively. These then agitated. An aliquot was taken, solutions were diluted to 100 µg/L (ppb) and an internal standard was added. The ICMs were purchased from LGC working solutions in methanol/water For the spiking experiments, a stock Standards SARL (Molsheim, France), 10/90 v/v. All subsequent dilutions were solution of the ICMs was added. A and deuterated internal standards were made in deionized HPLC water. portion of the water sample was fi ltered provided by an Agilent customer, but can through a syringe fi lter (Captiva Premium be ordered, for example, from Santa Cruz Syringe Filter Regenerated Cellulose, Biotechnology, Inc., Dallas, Texas. 25 mm, 0.45 µm, Agilent Technologies, p/n 5190-5111) into an autosampler vial. Table 1. Dynamic MRM acquisition parameters for the compounds under investigation. The fi rst transition is the quantifi er transition. Precursor MS1 Product MS2 RT RT Window Collision Compound ion (m/z) Resolution ion (m/z) Resolution (min) (min) energy (V) Cell accelerator voltage Iopamidol 777.9 Unit 541.9 Wide 3.73 1 32 3.5 777.9 Unit 558.9 Wide 3.73 1 24 3.5 777.9 Unit 386.9 Wide 3.73 1 42 1 Ioxitalamic acid 662.0 Unit 645.0 Wide 3.76 1 5 3 662.0 Unit 429.0 Wide 3.76 1 33 3 662.0 Unit 302.0 Wide 3.76 1 50 3 Iohexol 821.9 Unit 803.9 Wide 3.80 1 24 1.5 821.9 Unit 656.9 Wide 3.80 1 30 1 821.9 Unit 375.0 Wide 3.80 1 52 6 Iomeprol 777.8 Unit 404.8 Wide 3.73 1 44 3.5 777.8 Unit 558.7 Wide 3.73 1 28 3.5 777.8 Unit 532.0 Wide 3.73 1 22 3.5 Diatrizoic acid 614.8 Unit 360.4 Wide 3.88 1 25 1 614.9 Unit 233.0 Wide 3.88 1 47 3 Iopromide 792.0 Unit 573.0 Wide 4.04 1 28 2 792.0 Unit 558.9 Wide 4.04 1 28 2 Ioxaglic acid 1269.6 Wide 610.8 Wide 4.51 1 40 2 1269.6 Wide 455.9 Wide 4.51 1 60 5.5 Internal standards Iopamidol-D8 786.0 Unit 391.0 Wide 3.73 1 42 1 786.0 Unit 546.0 Wide 3.73 1 32 3.5 Iohexol-D5 826.9 Unit 809.0 Wide 3.80 1 20 1.5 Iomeprol-D3 781.0 Unit 562.0 Wide 3.86 1 22 3.5 781.0 Unit 535.0 Wide 3.86 1 22 3.5 Iopromide-D3 795.1 Unit 576.0 Wide 4.03 1 28 2 795.1 Unit 299.9 Wide 4.03 1 28 2 4 Results and Discussion ×103 5.5 A The selected ICMs are highly polar, 4 5 6 1. Iopamidol (777.9 & 558.9) and the analytical conditions had to be 5.0 2. Ioxitalamic acid (662.0 & 645.0) 3. Iohexol (821.9 & 803.9) carefully chosen to obtain adequate 4.5 4. Iomeprol (777.8 & 404.8) retention, acceptable peak shape, and 5. Diatrizoic acid (614.8 & 360.4) 4.0 6. Iopromide (792.0 & 573.0) good effi ciency. Moreover, care had to 1 7. Ioxaglic acid (1,269.6 & 610.8) be taken so that the sensitivity of the 3.5 mass spectrometer was not affected by 3.0 the choice of the mobile phase. All LC parameters were carefully optimized, and Counts 2.5 reversed-phase LC with a mobile phase 2.0 of acetic acid in water and acetonitrile 1.5 3 2 7 proved to give the best overall results in *2786 terms of chromatography and detection.