Strong Cation Exchange Cartridge Research Articles

Automated Synthesis of [68Ga]Ga-FAPI-46 on a Scintomics GRP Synthesizer.

[68Ga]Ga-FAPI-46 is a radiolabelled fibroblast activation protein inhibitor that selectively binds to fibroblast activation protein (FAP), which is overexpressed by cancer-associated fibroblasts (CAFs) in the tumour microenvironment. In recent years, radiolabelled FAP inhibitors (FAPIs) are becoming increasingly important in cancer diagnostics and also for targeted radionuclide therapy. Because of the increasing demand for radiolabelled FAPIs, automating the synthesis of these compounds is of great interest. In this work, we present a newly programmed automatic synthesis process of [68Ga]Ga-FAPI-46 on a Scintomics GRP module using two Galli Ad generators as a radionuclide source. Dedicated cassettes for the labelling of 68Ga-peptides were used without any modifications. The generators were connected via a three-way valve to the module and eluted automatically over a strong cation exchange (SCX) cartridge by using the vacuum pump of the synthesis module, eliminating the need to transfer the eluates into a separate vial. After a reaction step in HEPES buffer, the compound was purified by solid-phase extraction (SPE) over a Sep-Pak Light C18 cartridge. The evaluation of 10 routine syntheses of [68Ga]Ga-FAPI-46 resulted in a radiochemical yield of 72.6 ± 4.9%. The radiochemical purity was 97.6 ± 0.3%, and the amount of free gallium-68 and colloid was <2%. The final product fulfilled the quality criteria, which were adapted from relevant monographs of the European Pharmacopoeia (Ph. Eur.). This work presents the successful preparation of multiple doses of [68Ga]Ga-FAPI-46 in a GMP-compliant automated process for clinical use.

Determination of six thyroid hormones in dog brain and liver using acidic extraction, mixed-mode cleanup, and liquid chromatography–tandem mass spectrometry

Thyroid hormones (THs) play a critical role in the regulation of biological processes, such as growth, metabolism, and development, in various animal species. Prohormone L-thyroxine (T4) is secreted from the thyroid gland and carried to peripheral tissues. T4 is then biotransformed to several metabolites which play different roles, mainly by iodothyronine deiodinases. Determination of deiodinated TH metabolites in key organs such as liver and brain would help to understand tissue-specific TH metabolism and homeostasis. In this study, we thus developed a highly sensitive method for the determination of six THs [T4, 3,5,3′-triodo-L-thyronine (T3), 3,3′,5′-triiodo-L-thyronine (rT3), 3,5-diiodo-l-thyronine (3,5-T2), 3,3′-diiodo-l-thyronine (3,3′-T2), and 3-iodo-l-thyronine (3-T1)] in the brain and liver by using stored dog samples. The analytical method consisted of ultrasonic-assisted extraction in acetone acidified with formic acid, cleanup with a EVOLUTE® EXPRESS CX cartridge (reversed-phase combined with strong cation-exchange cartridge), and quantification with liquid chromatography-tandem mass spectrometry. Acceptable accuracy (internal standard-corrected recovery: 80%–120%) and intra- and inter-day precision (coefficient of variation: <6% and <15%, respectively) (n = 3/ batch, three days) were obtained for both brain and liver samples. In addition, low method detection limits were achieved for both brain (0.013–0.12 ng g–1) and liver (0.030–0.78 ng g–1), which resulted in the quantitation of not only T4, T3, and rT3, but also 3,3′-T2 in both dog brain and liver samples. The developed method was successfully applied to the analysis of THs in the brain and liver of dogs (Canis lupus familiaris) which were exposed to polychlorinated biphenyls (PCBs). As a result, concentration ratios of rT3/T4 and 3,3′-T2/T3 in the PCB-exposed dogs were significantly higher than those in the control groups, suggesting the enhanced inner (tyrosyl)-ring deiodination (5-deiodination) by PCB exposure. The analytical method developed in the present study enables comprehensive evaluation of alterations in peripheral TH metabolism which are caused by exposure to environmental pollutants.

Detection of 5α-reductase inhibitors by UPLC-MS/MS: Application to the definition of the excretion profile of dutasteride in urine.

An analytical procedure based on ultra-performance liquid chromatography-mass spectrometry was developed to screen and to confirm dutasteride and its metabolites in human urine. Sample preparation included an enzymatic hydrolysis followed by solid-phase extraction using the strong cation exchange cartridges OASIS® MCX. The chromatographic separation was carried out on C18 column, employing as mobile phases ultra purified water and acetonitrile, both containing 0.1% formic acid. Detection was achieved using a triple quadrupole as a mass spectrometric analyzer, with positive ion electrospray ionization and multiple reaction monitoring as acquisition mode. The analytical procedure developed was validated according to ISO 17025 and World Anti-Doping Agency guidelines. The extraction efficiency was estimated to be greater than 75% for both dutasteride and its hydroxylated metabolites. Detection capability was determined in the range of 0.1-0.4ng/mL. Specificity and repeatability of the relative retention times (CV%<0.5) and of the relative abundances of the characteristic ion transitions selected (CV%<10) were confirmed to be fit for purpose to ensure the unambiguous identification of dutasteride and its metabolites in human urine. The developed method was used to characterize the urinary excretion profile of dutasteride after both chronic and acute administration of therapeutic doses. After chronic administration, dutasteride and its hydroxylated metabolites were easily detected and confirmed. After acute administration, instead, only the two hydroxylated metabolites were detected for 3-4days.

Development of UPLC-Q-TOF-MS Coupled with Cation-exchange Solid-phase Extraction Method for the Determination of Ten Pyrrolizidine Alkaloids in Herbal Medicines.

Pyrrolizidine alkaloids are secondary metabolites of plants and can cause significant hepatotoxicity in humans. In this study, a fast and simple method was developed to determine ten pyrrolizidine alkaloids (PAs) in six types of herbal medicines using ultra performance liquid chromatography-quadrupole-time of flight mass spectrometry (UPLC-Q-TOF-MS). An efficient solid-phase extraction procedure was carried out by using strong cation-exchange cartridges and the parameters were optimized. The established analytical method was validated and the results showed that the method presented satisfactory accuracy and precision. The established method was successfully applied for the determination of PAs in six herbal plants, including Senecionis Scandentis Hebra, Arnebiae Radix, Asteris Radix Et Rhizoma, Farfarae Flos, Senecionis Cannabifolii Herba and Emilia sonchifolia. PAs were found in all of these herbal plant samples. Eight types of related commercial herbal drugs were also detected, six of them were detected with different amounts of PAs. This work not only provided a powerful technical platform for both qualitative and quantitative analysis of PAs in herbal medicines, but also obtained information concerning PAs in these herbal samples, which could provide reference to the government regulatory authorities and non-governmental organizations.

Total determination of triclabendazole and its metabolites in bovine tissues using liquid chromatography-tandem mass spectrometry

A reliable LC-MS/MS analytical method for the determination of residual triclabendazole and its principal metabolites (triclabendazole sulfoxide, triclabendazole sulfone and keto-triclabendazole) in bovine tissues was developed, in which triclabendazole and its metabolites are oxidized to keto-triclabendazole as a marker residue. The method involves sample digestion with hot sodium hydroxide, thus releasing the bound residues of various triclabendazole metabolites in bovine tissues. The target compounds are extracted from the digest mixture with ethyl acetate, defatted by liquid-liquid partitioning using n-hexane and acetonitrile, then oxidized with hydrogen peroxide in a mixture of ethanol and acetic acid. The reaction mixture is cleaned up using a strong cation exchange cartridge (Oasis MCX) and the analytes are quantified using LC-MS/MS. The optimal conditions for the complete oxidation of triclabendazole and its metabolites to keto-triclabendazole are an incubation time of 16 h and a temperature of 90 °C. The developed method was evaluated using three bovine samples: muscle, fat, and liver. Samples were spiked with triclabendazole and its principal metabolites at 0.01 mg/kg and at the Japanese Maximum Residue Limits (MRLs) established for each sample. The validation results show excellent recoveries (81–102%) and precision (<10%) for all target compounds. The limit of quantification (S/N ≥ 10) of the developed method is 0.01 mg/kg. These results suggest the developed method is applicable to quantifying residual triclabendazole in bovine tissues in compliance with the MRLs established by the Codex Alimentarius and EU and Japanese regulations, and thus the proposed method will be a useful tool for the regulatory monitoring of residual triclabendazole and its metabolites.

Solid phase fractionation techniques for segregation of red cabbage anthocyanins with different colorimetric and stability properties

Red cabbage anthocyanin extract contains cyanidin derivatives as various non-, mono-, and di-acylated forms capable of expressing various colors from red to blue. The objective of this study was to develop a simple solid phase extraction (SPE) method to fractionate and segregate di-acylated anthocyanins which have greater stability and more desirable blue colorimetric properties. Two different sorbents with different separation chemistries: SCX (Strong Cation Exchange) and C18 sorbents were evaluated. Red cabbage anthocyanins were fractionated and eluted from the SCX cartridge using combinations of different buffers (pH 6–8) and MeOH (20–70%) or eluted from the C18 cartridge using different percentages of acidified (0.01% HCl) MeOH (30–100%) or EtOH (10–100%). With SCX SPE, washing the loaded pigments with a mixture of buffer pH 6 + 20% MeOH followed by elution with buffer pH 8 + 70% MeOH proved most effective in segregating the di-acylated pigments; however, some anthocyanins were permanently retained by the sorbent. When using the C18 cartridge, washing bound pigments with 32% MeOH or 18.5% EtOH and eluting with 100% alcohol respectively resulted in high (> 93%) recovery of di-acylated pigments. The C18 cartridge with MeOH eluent was the most effective for isolating the target di-acylated red cabbage anthocyanins that produced desirable blue colors with increased stability.

Determination of Caffeine and Its Metabolites in Wastewater Treatment Plants Using Solid-Phase Extraction and Liquid Chromatography-Tandem Mass Spectrometry.

For caffeine and its seven major metabolites (i.e., theobromine, theophylline, paraxanthine, 1-methylxanthine, 3-methylxanthine, 7-methylxanthine, and xanthine), an optimized analytical method using liquid chromatography-tandem mass spectrometry (LC-MS/MS) for their detection in wastewater samples was developed in this study. Extraction of these compounds (recoveries ranged from 60.3 to 83.2%) was made possible by combining universal polymeric reversed-phase cartridge and polymeric strong cation exchange cartridge. This method was applied to the determination of caffeine and its metabolites in the influent and effluent of an anaerobic-anoxic-oxic (A2O) process. In the A2O influent, caffeine and its metabolites (except xanthine) ranged from 1.39 to 5.45 μg/L, and their concentrations in the A2O effluent ranged from 10.2 to 171.3 ng/L. The mass load of caffeine was 14.9 g/day/1000 inhabitants, considering the population served by the target wastewater treatment plant (WWTP). The concentration of caffeine derivatives in wastewater influent is a tool for estimating the population size in the area served by WWTPs.

Simultaneous determination of kasugamycin and validamycin-A residues in cereals by consecutive solid-phase extraction combined with liquid chromatography–tandem mass spectrometry

ABSTRACTTwo polar aminoglycosides, kasugamycin and validamycin-A, were determined in cereals (brown rice, wheat and corn) by high-performance liquid chromatography–tandem mass spectrometry. The analytes were extracted from samples using methanol and water (70:30, v/v) at pH 5.5, purified using both a hydrophilic–hydrophobic-balanced cartridge and a strong cation-exchange cartridge, and then analysed using multiple reaction monitoring in positive electrospray ionisation mode with a special ReproSil 100 C18 high-performance liquid chromatography column. This newly proposed method yielded good sensitivity and excellent chromatographic performance. The limits of quantification for kasugamycin and validamycin-A were 4.1 µg/kg and 1.0 µg/kg, respectively. The recoveries for both compounds at three fortification levels (4, 100 and 500 µg/kg for kasugamycin; 1, 10 and 100 µg/kg for validamycin-A) ranged from 75% to 110%, and the relative standard deviations were below 15%.

An Improved Method for the Quantification of Thiamine (Vitamin B1) in Cocoa-Containing Beverage Powders.

The purpose of this work was to understand low recoveries of thiamine (vitamin B1) when extracted from cocoa-containing beverage powders fortified with water-soluble vitamin B1, and to develop and validate a new procedure to improve these results. Based on the literature, previous trials have focused on two main factors: pH value prior to paper filtration and the need for solid-phase extraction (SPE) clean up. We demonstrate that by following European Standard EN 14122, recovery of thiamine in cocoa-containing beverage powders is low and dependent on the test portion (86 and 72% for 0.5 and 1.5 g test portions, respectively). Our improved method resolved this problem by keeping the pH low (around 1) prior to paper filtration, leading to a 96.3% recovery and high precision (RSDr of 3.5%). The use of strong cation-exchange SPE cartridges for cleanup prior to the thiamine oxidation reaction proved to be essential. A comparison between our improved method and EN 14122 on nine cocoa-containing beverage samples available on local market from different manufacturers showed a systematic increase in thiamine content (up to 70%) when the improved method was applied. The highest difference was observed for the sample that contained the highest amount of cocoa. However, for beverage powders that contained both cocoa and milk, no difference was observed.

Tandem Mass Spectrometry Quantitation of Lyso-Gb3 and Six Related Analogs in Plasma for Fabry Disease Patients.

Fabry disease is an X-linked lysosomal storage disorder, caused by a deficit in α-galactosidase A enzyme activity, leading to the storage of sphingolipids such as globotriaosylsphingosine (lyso-Gb3 ), globotriaosylceramide (Gb3 ), and galabiosylceramide (Ga2 ) in organs, tissues and biological fluids. A recent metabolomic study performed in plasma revealed lyso-Gb3 analogs as novel Fabry disease biomarkers. These molecules correspond to lyso-Gb3 with different chemical modifications on the sphingosine chain (-C2 H4 , -H2 , +O, +H2 O, +H2 O2, and +H2 O3 ). An ultra-performance liquid chromatography tandem mass spectrometry (UPLC-MS/MS) method was developed and validated for the multiplex analysis of lyso-Gb3 and its 6 analogs in plasma. The samples are prepared by solid phase extraction using mixed-mode strong cation exchange (MCX) cartridges. An in-house synthesized N-glycinated lyso-Gb3 derivative was used for the internal standard. The limits of detection (LODs) measured for lyso-Gb3 and its analogs ranged from 0.06 to 0.29nM. © 2016 by John Wiley & Sons, Inc.

Flexible Method for Analysis of Lidocaine and Its Metabolite in Biological Fluids.

A robust liquid chromatography-tandem mass spectrometry (LC-MS-MS) method has been developed and validated for the determination of lidocaine (LIDO) and its metabolite (monoethylglycinexylidide (MEGX)) in serum. One hundred microliters of bovine serum were spiked with LIDO-d10 as internal standard and deproteinized with acetonitrile prior to solid-phase extraction purification using strong cation exchange cartridge. The chromatographic separation was achieved on a BetaBasic-18 column with a mobile phase consisting of aqueous 0.1% formic acid and 0.1% formic acid in acetonitrile. The instrumental linearity was verified from 0.4 to 1,000 ng/mL obtaining determination coefficients (r(2)) of >0.99. The limit of quantification (LOQ) was set at 1 ng/mL for both LIDO and MEGX. The coefficients of variation for within- and between-batch imprecision, including LOQ, were ≤10% and the percentage of inaccuracy was <15%. The absolute recoveries were >75% for both analytes. Experiments demonstrated the method applicability to sera of different animal species and also to plasma, urine and milk matrices.

A facile direct nucleophilic synthesis of O-(2-[18F]fluoroethyl)-l-tyrosine ([18F]FET) without HPLC purification

Due to favourable in vivo characteristics, its high specificity and the longer half-life of 18F (109.8 min) allowing for remote-site delivery, O-(2-[18F]fluoroethyl)-l-tyrosine ([18F]FET) has gained increased importance for molecular imaging of cerebral tumors. Consequently, the development of simple and efficient production strategies for [18F]FET could be an important step to further improve the cost-effective availability of [18F]FET in the clinical environment. In the present study [18F]FET was synthesized via direct nucleophilic synthesis using an earlier developed chiral precursor, the NiII complex of an alkylated (S)-tyrosine Schiff base, Ni-(S)-BPB-(S)-Tyr-OCH2CH2OTs. The purification method has been developed via solid phase extraction thereby omitting cumbersome HPLC purification. The suggested SPE purification using combination of reverse phase and strong cation exchange cartridges provided [18F]FET in high chemical, radiochemical and enantiomeric purity and 35 % radiochemical yield (decay-corrected, 45 min synthesis time). The method was successfully automated using a commercially available synthesis module, Scintomics Hotboxone. Based on the current results, the proposed production route appears to be well suited for transfer into an automated cassette-type radiosynthesizers without using HPLC.

Applying polarity rapid assessment method and ultrafiltration to characterize NDMA precursors in wastewater effluents

Certain nitrosamines in water are disinfection byproducts that are probable human carcinogens. Nitrosamines have diverse and complex precursors that include effluent organic matter, some anthropogenic chemicals, and natural (likely non-humic) substances. An easy and selective tool was first developed to characterize nitrosamine precursors in treated wastewaters, including different process effluents. This tool takes advantages of the polarity rapid assessment method (PRAM) and ultrafiltration (UF) (molecular weight distribution) to locate the fractions with the strongest contributions to the nitrosamine precursor pool in the effluent organic matter. Strong cation exchange (SCX) and C18 solid-phase extraction cartridges were used for their high selectivity for nitrosamine precursors. The details of PRAM operation, such as cartridge clean-up, capacity, pH influence, and quality control were included in this paper, as well as the main parameters of UF operation.Preliminary testing of the PRAM/UF method with effluents from one wastewater treatment plant gave very informative results. SCX retained 45–90% of the N-nitrosodimethylamine (NDMA) formation potential (FP)—a measure of the precursors—in secondary and tertiary wastewater effluents. These results are consistent with NDMA precursors likely having a positively charged amine group. C18 adsorbed 30–45% of the NDMAFP, which indicates that a substantial portion of these precursors were non-polar. The small molecular weight (MW) (<1 kDa) and large MW (>10 kDa) fractions obtained from UF were the primary contributors to NDMAFP. The combination of PRAM and UF brings important information on the characteristics of nitrosamine precursors in water with easy operation.

Multi-dye residue analysis of triarylmethane, xanthene, phenothiazine and phenoxazine dyes in fish tissues by ultra-performance liquid chromatography–tandem mass spectrometry

Beside the possible illegal use of malachite green in aquaculture, other familiar dyes could also been applied by fraudulent producers due to their antiseptic and antibacterial activity. In this contribution, a new sensitive multi-residue method was developed to determine triarylmethane, xanthene, phenothiazine and phenoxazine dyes in fish by ultra-performance liquid chromatography-tandem mass spectrometry. Samples were extracted with acetonitrile, followed by an oxidation step using 2,3-dichloro-5,6-dicyanobenzoquinone. Further clean-up was performed by tandem solid phase extraction using weak and strong cation exchange cartridges. Extracts were analysed by UPLC-MS(n) operating in the positive electrospray ionisation mode (ESI+). The fourteen dyes were separated within only 12min on a C18 BEH column using 1mM ammonium acetate in water at pH 4.5 and acetonitrile as mobile phases at a flowrate of 0.4mLmin(-1). The presented method was validated as defined by the European Union and scientific literature. Good linearity (R ≥0.99 and goodness-of-fit (g) ≤10%) was achieved over the tested concentration range (0.25-2ngg(-1)). Limit of quantification was 0.25ngg(-1) for all dyes, with a signal-to-noise ratio of at least 10/1. This is at least 5 to 10 times lower than previous published methods. Limits of detection were all <0.1ngg(-1). Precision and trueness fell within the criteria requested by the EC requirements for this concentration range. Decision limit (CCα) and detection capability (CCβ) were all <1 and <0.25ngg(-1), respectively. Due to background levels of the xanthene dyes, the two rhodamine dyes could only be determined above 0.75ngg(-1). For these dyes, the method can only be used for screening purposes. To show the applicability of the method, a monitoring study was performed to investigate the occurrence of artificial dyes in wildlife European eel in Flemish rivers.

Simplified NaCl Based 68Ga Concentration and Labeling Procedure for Rapid Synthesis of 68Ga Radiopharmaceuticals in High Radiochemical Purity

A simple sodium chloride (NaCl) based (68)Ga eluate concentration and labeling method that enables rapid, high-efficiency labeling of DOTA conjugated peptides in high radiochemical purity is described. The method utilizes relatively few reagents and comprises minimal procedural steps. It is particularly well-suited for routine automated synthesis of clinical radiopharmaceuticals. For the (68)Ga generator eluate concentration step, commercially available cation-exchange cartridges and (68)Ga generators were used. The (68)Ga generator eluate was collected by use of a strong cation exchange cartridge. 98% of the total activity of (68)Ga was then eluted from the cation exchange cartridge with 0.5 mL of 5 M NaCl solution containing a small amount of 5.5 M HCl. After buffering with ammonium acetate, the eluate was used directly for radiolabeling of DOTATOC and DOTATATE. The (68)Ga-labeled peptides were obtained in higher radiochemical purity compared to other commonly used procedures, with radiochemical yields greater than 80%. The presence of (68)Ge could not be detected in the final product. The new method obviates the need for organic solvents, which eliminates the required quality control of the final product by gas chromatography, thereby reducing postsynthesis analytical effort significantly. The (68)Ga-labeled products were used directly, with no subsequent purification steps, such as solid-phase extraction. The NaCl method was further evaluated using an automated fluid handling system and it routinely facilitates radiochemical yields in excess of 65% in less than 15 min, with radiochemical purity consistently greater than 99% for the preparation of (68)Ga-DOTATOC.

A GC–EI-MS-MS Method for Simultaneous Determination of Seven Adulterants in Slimming Functional Foods

A gas chromatography-electron impact-tandem mass spectrometric method was established for the simultaneous determination of seven adulterants, including fenfluramine (FEN), norpseudoephedrine (NPE), pseudoephedrine (PSE), ephedrine (EPH), amfepramone (AMF), sibutramine (SIB) and strychnine (STR) in slimming functional foods. The target chemicals were extracted with 2% formic acid solution and then cleaned-up with solid-phase extraction using a strong cation exchange cartridge from tablet, liquid, mixed plant powder and capsule formulations. Chromatographic separation was accomplished on a VF-5MS column within 23 min. Leucomalachite green was employed as an internal standard. The recoveries of seven target chemicals in two formulations ranged from 80.1 to 106%. Limits of detection of the method were from 7.5 to 375 µg/kg with relative standard deviations of 1.6 to 13.9%. The linearity of the method ranged from 90 to 1500 ng/mL for NPE, 150 to 1500 ng/mL for STR, 10 to 500 ng/mL for AMF, 5.0 to 500 ng/mL for PSE and EPH and 3.0 to 500 ng/mL for FEN and SIB. This method was applied to the determination of six brands of slimming functional foods. SIB was detected in five of the samples with the contents in the range of 10.3 - 8.55 × 10(5) μg/kg.

Simultaneous Detection of Residues of 25 β2-Agonists and 23 β-Blockers in Animal Foods by High-Performance Liquid Chromatography Coupled with Linear Ion Trap Mass Spectrometry

A sensitive method has been developed for the simultaneous determination of residues of 25 β₂-agonists and 23 β-blockers in animal foods by high-performance liquid chromatography coupled with linear ion trap mass spectrometry (HPLC-LIT-MS). This method is based on a new procedure of hydrolysis and extraction by 5% trichloracetic acid, and then cleaned up by mixed strong cation exchange (MCX) cartridges coupled with a novelty cleanup step by methanol. Methanol and 0.1% formic acid were used as mobile phases for gradient elution, while a Supelco Ascentis Express Rp-Amide column was used for LC separation. ESI positive ion scan mode was used with consecutive reaction monitoring (CRM, MS³). Nine β₂-agonists labeled by the deuterium isotope were used as internal standards for quantification. The linear ranges of 48 analytes were from 5 to 200 μg/L; the coefficient of correlation was not less than 0.995. Blank pork muscle, blank liver, and blank kidney were selected as representative matrix for spiked standard recovery test. The recoveries of each compound were in the range of 46.6-118.9%, and the relative standard deviations were in the range of 1.9-28.2%. Decision limits (CCα, α = 0.01) of 48 analytes in muscles, liver, and kidney samples ranged from 0.05 to 0.49 μg/kg, and the detection capability (CCβ, β = 0.05) ranged from 0.13 to 1.64 μg/kg. This method was successfully applied to 110 real animal origin food samples including meat, liver, and kidney of pig and chicken samples.

A highly sensitive LC‐MS/MS method capable of simultaneously quantitating celiprolol and atenolol in human plasma for a cassette cold‐microdosing study

A highly sensitive simultaneous quantitative method for a cassette cold-microdosing study on celiprolol and atenolol was developed with liquid chromatography-tandem mass spectrometry. The method utilizes a combination of solid-phase extraction (SPE) with strong cation exchange (SCX) cartridge columns and reversed-phase chromatography with an ODS analytical column. SCX-SPE cartridge columns (100 mg sorbent) were used for a selective extraction of celiprolol, atenolol and metoprolol (internal standard) from 500 μL of human plasma samples. Turbo-ion spray at positive mode was employed for the ionization of the drug compounds. Quantitation was performed on a triple quadrupole mass spectrometer by selected reaction monitoring with the transitions of m/z 380 to m/z 251 for celiprolol and m/z 267 to m/z 145 for atenolol. Separation of analytes was achieved on an ODS column (100 mm length × 2.1 mm id, 3 μm) by a gradient elution with 10 mM formic acid and methanol by varying their proportion at a flow rate of 0.2 mL/min. The method was validated in the range of 1-250 pg/mL for celiprolol and 2.5-250 pg/mL for atenolol and was successfully applied to the elucidation of pharmacokinetic profiling in a cold cassette microdosing study of the β-blockers.

Determination and Confirmation of Tulathromycin Residues in Bovine Liver and Porcine Kidney via Their Common Hydrolytic Fragment Using High-Performance Liquid Chromatography/Tandem Mass Spectrometry

An accurate, reliable, and reproducible analytical method using HPLC/MS/MS for the determination of tulathromycin residues in bovine liver and porcine kidney via their common hydrolytic fragment (CP-60,300) was developed and validated. Briefly, the method involved an initial acid treatment of intact tissues, which yielded the common fragment (CP-60,300). A portion of the acid hydrolyzate was purified by SPE using a strong cation exchange cartridge. Evaporation of the purified extract was followed by reconstitution in aqueous buffer and analysis by HPLC/MS/MS under isocratic conditions. The developed method provided acceptable sensitivity for determinative surveillance of tulathromycin in porcine kidney and bovine liver with an LOQ of 7.50 and 2.75 microg/g, respectively. The overall recovery and precision of 45 determinations of each tissue were 97.8% (5.3%) for porcine kidney and 96.9% (7.9%) for bovine liver. Accuracy, precision, linearity, specificity, and ruggedness were demonstrated. An HPLC/MS/MS method was also developed for use in these tissues as a confirmatory assay following modifications to the MS detection parameters. The confirmatory method demonstrated acceptable sensitivity for confirmatory evaluation of tulathromycin in porcine kidney and bovine liver at tolerances of 15 and 5.5 microg/g, respectively.

Arsenic contamination of natural waters in San Juan and La Pampa, Argentina

Arsenic (As) speciation in surface and groundwater from two provinces in Argentina (San Juan and La Pampa) was investigated using solid phase extraction (SPE) cartridge methodology with comparison to total arsenic concentrations. A third province, Río Negro, was used as a control to the study. Strong cation exchange (SCX) and strong anion exchange (SAX) cartridges were utilised in series for the separation and preservation of arsenite (As(III)), arsenate (As(V)), monomethylarsonic acid (MA(V)) and dimethylarsinic acid (DMA(V)). Samples were collected from a range of water outlets (rivers/streams, wells, untreated domestic taps, well water treatment works) to assess the relationship between total arsenic and arsenic species, water type and water parameters (pH, conductivity and total dissolved solids, TDS). Analysis of the waters for arsenic (total and species) was performed by inductively coupled plasma mass spectrometry (ICP-MS) in collision cell mode. Total arsenic concentrations in the surface and groundwater from Encon and the San José de Jáchal region of San Juan (north-west Argentina within the Cuyo region) ranged from 9 to 357μgl(-1) As. Groundwater from Eduardo Castex (EC) and Ingeniero Luiggi (LU) in La Pampa (central Argentina within the Chaco-Pampean Plain) ranged from 3 to 1326μgl(-1) As. The pH range for the provinces of San Juan (7.2-9.7) and La Pampa (7.0-9.9) are in agreement with other published literature. The highest total arsenic concentrations were found in La Pampa well waters (both rural farms and pre-treated urban sources), particularly where there was high pH (typically > 8.2), conductivity (>2,600 μS cm(-1)) and TDS (>1,400mgl(-1)). Reverse osmosis (RO) treatment of well waters in La Pampa for domestic drinking water in EC and LU significantly reduced total arsenic concentrations from a range of 216-224μgl(-1) As to 0.3-0.8μgl(-1) As. Arsenic species for both provinces were predominantly As(III) and As(V). As(III) and As(V) concentrations in San Juan ranged from 4-138μgl(-1) to <0.02-22μgl(-1) for surface waters (in the San José de Jáchal region) and 23-346μgl(-1) and 0.04-76μgl(-1) for groundwater, respectively. This translates to a relative As(III) abundance of 69-100% of the total arsenic in surface waters and 32-100% in groundwater. This is unexpected because it is typically thought that in oxidising conditions (surface waters), the dominant arsenic species is As(V). However, data from the SPE methodology suggests that As(III) is the prevalent species in San Juan, indicating a greater influence from reductive processes. La Pampa groundwater had As(III) and As(V) concentrations of 5-1,332μgl(-1) and 0.09-592μgl(-1) for EC and 32-242μgl(-1) and 30-277μgl(-1) As for LU, respectively. Detectable levels of MA(V) were reported in both provinces up to a concentration of 79μgl(-1) (equating to up to 33% of the total arsenic). Previously published literature has focused primarily on the inorganic arsenic species, however this study highlights the potentially significant concentrations of organoarsenicals present in natural waters. The potential for separating and preserving individual arsenic species in the field to avoid transformation during transport to the laboratory, enabling an accurate assessment of in situ arsenic speciation in water supplies is discussed.