Ammonium Formate Solution Research Articles

Separation and characterization of unknown impurities in cefonicid sodium by trap-free two-dimensional liquid chromatography combined with ion trap time-of-flight mass spectrometry.

Seven unknown antibiotic impurities in cefonicid sodium were separated and characterized by a trap-free two-dimensional liquid chromatography coupled to high-resolution ion-trap time-of-flight mass spectrometry (2D-LC/IT-TOF MS) using both positive and negative modes of electrospray ionization. Trap-free 2D-LC and an online demineralization technique made it possible to characterize cefonicid sodium under the conditions of the official standard, and the TIC chromatogram obtained by LC/MS was in conformity with the LC chromatogram obtained by the official analytical method in the peak sequence of impurities. In the first dimension, the column was a GRACE Alltima C18 (250mm×4.6mm, 5μm), and the gradient elution used 0.02mol·L-1 ammonium dihydrogen phosphate solution and methanol as mobile phase. In the second dimension, the analytical column was a Shimadzu Shim-pack GISS C18 (50mm×2.1mm, 1.9μm) with 10mmol·L-1 ammonium formate solution and methanol as mobile phase. Full scan LC/MS was first executed to obtain the exact m/z values of the molecules. Then LC/MS2 and LC-MS3 experiments were performed on the compounds of interest. The structures of seven unknown degradation products in cefonicid sodium were deduced based on the high-resolution MSn data using both positive and negative mode. The problem of incompatibility between the non-volatile salt mobile phase and mass spectrometry was solved completely by multidimensional heart-cutting approaches and an online demineralization technique, which is worthy of widespread use and application for the advantages of stability and repeatability.

Separation and characterization of allergic polymerized impurities in cephalosporins by 2D-HPSEC × LC-IT-TOF MS

Eleven unknown allergic impurities in cefodizime, cefmenoxime and cefonicid were separated and characterized by a trap-free two-dimensional high performance size exclusion chromatography (HPSEC) and reversed phase liquid chromatography (RP-HPLC) coupled to high resolution ion trap/time-of-flight mass spectrometry (2D-HPSEC×LC-IT-TOF MS) with positive and negative modes of electrospray ionization method. Separation and characterization the allergic polymerized impurities in β-lactam antibiotics were on the basis of column-switching technique which effectively combined the advantages of HPSEC and the ability of RP-HPLC to identify the special impurities. In the first dimension HPSEC, the column was Xtimate SEC-120 analytical column (7.8mm×30cm, 5μm), and the gradient elution used pH 7.0 buffer-acetonitrile as mobile phase And the second dimension analytical column was ZORBAX SB-C18 (4.6×150mm, 3.5μm) with ammonium formate solution (10mM) and ammonium formate (8mM) in [acetonitrile-water (4:1, v/v)] solution as mobile phase. Structures of eleven unknown impurities were deduced based on the high resolution MSn data with both positive and negative modes, in which nine impurities were polymerized impurities. The forming mechanism of β-lactam antibiotic polymerization in cephalosporins was also studied. The question on incompatibility between non-volatile salt mobile phase and mass spectrometry was solved completely by multidimensional heart-cutting approaches and online demineralization technique, which was worthy of widespread use and application for the advantages of stability and repeatability.

Multiclass method for the determination of pharmaceuticals and personal care products in compost from sewage sludge using ultrasound and salt-assisted liquid–liquid extraction followed by ultrahigh performance liquid chromatography-tandem mass spectrometry analysis

An analytical method for the analysis of 16 pharmaceuticals and personal care products in compost from sewage sludge is successfully validated. Ultrasound assisted extraction with a mixture of acetonitrile:ethyl acetate (1:1, v/v) containing 10% (v/v) of acetic acid was carried out. Two cycles of extraction of 10min were applied. A clean-up of the extracts using salt-assisted liquid–liquid extraction (SALLE) was also included. Experimental design was used for the optimization of the main parameters involved in the extraction and cleaned-up steps. The chromatographic separation was carried out by ultrahigh performance liquid chromatography using a mobile phase gradient mixture of a 13mM buffer ammonium formate solution (pH 9.25) (solvent A) and methanol (solvent B). An ACQUITY UPLC® BEH C18 column (1.7μm; 2.1×50mm) column was used. Analytes were separated in less than 11min. The compounds were detected and quantified using single reaction monitoring electrospray tandem mass spectrometry. The limits of detection calculated ranged from 0.5 to 4ngg−1d.w., and the limits of quantification from 2 to 13ngg−1d.w. Recoveries from 93% to 111%, with relative standar deviations lower than 11% in all cases, were obtained. The method was applied to natural compost samples. High concentrations of some analytes were found. Ketoprofen (510ngg−1d.w.), methylparaben (240ngg−1d.w.), diclofenac (175ngg−1d.w.) and flufenamic acid (128ngg−1d.w.) were the most abundant.

Simultaneous determination of amantadine, rimantadine, and memantine in processed products, chicken tissues, and eggs by liquid chromatography with tandem mass spectrometry.

A simultaneous determination of amantadine, rimantadine, and memantine in processed products (deep-fried chicken, fried chicken, fried quail egg, and grilled chicken) with liquid chromatography tandem mass spectrometry (LC-MS/MS) was developed. This new method was also applicable for chicken tissue (muscle, liver, and gizzard) and eggs. The chromatographic separation was performed on a Kinetex® XB-C18 core-shell technology column using a mobile phase of acetonitrile and 0.1% formic acid in a 10mmol/L ammonium formate solution, resulting in the complete separation of isomers (rimantadine and memantine) and any other obstructive peaks from the sample matrices. Sample preparation was performed by a modified QuEChERS method using acetonitrile and a 0.1% acetic acid extraction solution and cleaned using an Oasis® MCX cartridge. The sample matrix had no effect on the identification of the compounds. For quantification, an external solvent calibration curve was used. This new method exhibited good accuracy ranging from 79.9% to 91.5%. The relative standard deviation of repeatability (RSDr) ranged from 1.2% to 3.6% and the relative standard deviation of within-laboratory reproducibility (RSDWR) ranged from 1.3% to 6.0%. These standard deviations satisfied the criteria for Japanese validation guidelines. The limit of quantification (LOQ) was 1.0μg/kg for all samples. Analyte residues were not detected in 55 samples using the validated method.

Simultaneous determination of diminazene aceturate and isometamidium chloride residues in cattle tissues by high performance liquid chromatography with solid-phase extraction

A method for the simultaneous determination of trypanocidal diminazene aceturate (DIM) and isometamidium chloride (ISM) that containing benzamidine groups in cattle tissues was developed by high performance liquid chromatography (HPLC) with solid-phase extraction (SPE). The tissue samples were extracted with different proportions of water-acetonitrile, then were cleaned up by Oasis WCX cartridges. DIM and ISM were separated by HPLC with a Spherisorb CN column (250 mm×4.6 mm, 5 μm). Acetonitrile-0.05 mol/L ammonium formate solution (pH 2.4) was used as mobile phases with gradient elution. The detection wavelength of UV was set at 380 nm. The limits of detection (LODs) and the limits of quantification (LOQs) of DIM and ISM in cattle tissues were 0.01 mg/kg and 0.025 mg/kg, respectively. The correlation coefficients (r) of DIM and ISM in cattle tissues were not less than 0.9993. The average recoveries of DIM and ISM at three spiked levels were 82.2%-97.6% with the intra-day relative standard derivations (RSDs) of 0.3%-5.2% (n=5) and inter-day RSDs of 1.3%-5.2% (n=15). The method was successfully applied to the analysis of DIM and ISM in cattle tissues. The method is rapid, sensitive and repeatable for the determination of diminazene aceturate and isometamidium chloride in cattle tissues.

Synthesis of Biokerosene through Electrochemical Hydrogenation of Terpene Hydrocarbons from Turpentine Oil

Indonesia possesses great potential for developing renewable resources as alternative fuels. For example, turpentine oil obtained from Pinus merkusii , which contains mostly monoterpene hydrocarbons (C 10 H 16 ). The oil is highly suitable to be processed for biokerosene or even jet biofuel. It consists of hydrocarbons within the range of C 10 to C 15 . However, it contains insufficient H and thus needs to be upgraded. In the present work, electrochemical hydrogenation was used for upgrading. In the electrochemical cell, stainless steel, silver, and carbon were used alternately for the anode, while copper and silver Raschig rings were used for the cathode. An electrolyte solution of cuprous ammonium formate was utilized not only as a source of H but also to draw the unsaturated hydrocarbons into the aqueous phase. The electrolyte : oil ratio (up to 2:1), electrolyte concentration (between 0.4 and 2 M) and reaction time were varied throughout the experiments. The bromine number (unsaturation level) of the turpentine oil, which was initially 1,86 (mole Br 2 /mole), was lowered significantly to 0.69-0.90. Promising increase of smoke point values were observed from 11 mm to 16-24 mm, indicating a higher H content of the processed oil, thus making it suitable as a substitute for petroleum kerosene.

Optimisation and validation of a new analytical method for the determination of four natural and synthetic hormones using LC-ESI-MS/MS

ABSTRACTA rapid liquid chromatographic-tandem mass spectrometric method was developed for the simultaneous determination of four natural and synthetic hormone residues (progesterone, testosterone, trenbolone acetate and zeranol) in animal tissue samples. Sample preparation was optimised to minimise time and solvent consumption. Meat samples were mechanically homogenised and digested in a procedure that gave similar recoveries to those enzymatically hydrolysed by Helix pomatia. Efficient extraction was achieved using acidified acetonitrile (1% acetic acid). Chromatographic conditions were optimised to minimise matrix effects. Analytes were separated using a C18 column with gradient elution using ammonium formate solution in methanol (MeOH)/water (1:9) and MeOH mobile phases. Finally, residues were qualitatively and quantitatively determined by electrospray ionisation tandem mass spectrometry in multiple reaction monitoring mode. Different parameters for LC-MS/MS (e.g., declustering potential and collision energy) were optimised using API 6500QT; all analytes were measured using positive-mode electrospray ionisation (ESI+) except zeranol which was measured in negative mode (ESI–). Due to LC-MS/MS signal enhancement/suppression, the determination of hormones was based on matrix-matched standard calculations. The method was validated for the four hormones on meat samples at different fortification levels and showed accepted performance criteria according to European Commission Decision 2002/657/EC. Decision limits and detection capabilities were estimated for all analytes.

Simultaneous determination of ginsenoside Rg1 , Re and notoginsenoside R1 in human plasma by LC-MS/MS and its application in a pharmacokinetic study in Chinese volunteers.

A rapid and sensitive liquid chromatography-tandem mass spectrometry (LC-MS/MS) method has been developed and validated for simultaneous quantification of ginsenosides Rg1 , Re and notoginsenoside R1 in human plasma. Chromatography was performed on Capcell Pak C18 MG II column using a binary gradient using mobile phase A (5 mm ammonium formate solution) and B (methanol, containing 5 mm ammonium formate) at a flow rate of 0.3 mL/min. The entire chromatographic run time was 3.2 min. Quantification was achieved using multiple reaction monitoring in positive mode using API 3000. This method was validated in terms of specificity, linearity, precision, accuracy, matrix effect and stability. The calibration curves were linear in the concentration range of 0.020-5.00 ng/mL for ginsenosides Rg1 , Re and notoginsenoside R1 . The lower limit of quantification (LLOQ) of this method was 0.020 ng/mL. The intra-run and inter-run precision values were within 12.31% for ginsenoside Rg1 , 14.13% for ginsenoside Re and 11.46% for notoginsenoside R1 at their LLOQ levels. The samples were stable under all tested conditions. This method was successfully applied to study the pharmacokinetics of ginsenoside Rg1 and notoginsenoside R1 in 24 healthy volunteers following oral administration of 200 mg Sanqi Tongshu Enteric-Pellets Capsule.

Analysis of 8-hydroxy-2'-deoxyguanosine in human urine by ultra-high performance liquid chromatography mass spectrometer method

To develop an ultra-high performance liquid chromatography mass spectrometer method for the rapid determination of 8-hydroxy-2'-deoxyguanosine (8-OHdG) in human urines. 8-OHdG standard solution with the concentration from 0.01 to 0.1 μg/ml was formulated. The solution was implanted into ion source with a rate of 7 μl/min, the mass-to-charge ratio of parent ion and product ions, and ion mass to charge ratio was identified. The mass spectrum parameters of each Ion pairs, such as DP, EP and EXP, were gradually optimized. The urine sample with a concentration of 10.0 μg/L was detected, and the pH of the sample was adjusted using 1 mol/L ammonium formate and formic acid solution with a volume ratio of 5∶1, 4∶1, 3∶1, 2∶1, and 1∶1. It was tested using three different polarity of SPE, i.e.: HLB, MCX, and MAX. The elution effect of methanol and water mixture with the proportion of 90∶10, 80∶20, 50: 50, 20: 80, and 10: 90 were tested, and then acetonitrile and water mixture with the proportion of 90∶10, 80∶20, 50∶50, 20∶80, 10∶90 were also tested. The standard curve was constructed using the ratio of a standard series application fluid concentration to corresponding compounds quantitative ion liquid concentration of the peak area. The detection limit was determined as 3 times of the signal to noise ratio corresponding to the concentration of 8-OHdG, and the quantitative lower limit was determined as 10 times of the signal to noise ratio corresponding to the concentration of 8-OHdG. The blank urine spiked recovery method was used to evaluate the precision and recovery rate. The mass to charge ratio of parent ion was 284.1 and the product ions was 168.1, 140.1, 123.0, and 112.0, respectively. The collision voltage of quantitative ion-pair 284.1/168.1 was 18 V, the 284.1/140.1 collision voltage was 42 V, the 284.1/123.0 collision voltage was 48 V, and the 284.1/112.0 collision voltage was 53 V. The recovery rate was the highest (87.9%-104.3%) when the pH of urine was adjusted by a 10 ml 1 mol/L ammonium formate solution, 2 ml of formic acid, 88 ml of water are mixed with the sample solution volume ratio of 1∶5, and then purified with 3 ml of methanol and 3 ml water activated HLB extraction column. Within 1.0-100.0 μg/L concentration range, 8-OHdG standard application solution test results showed a good linear relationship. The regression equation was y= 1.25x+0.74, and the correlation coefficient was r=0.999 5. The detection limit was 0.2 μg/L, and the limit of quantification was 0.7 μg/L. The method of recovery rate was in the range of 87.9% to 104.3%, the precision was in the range from 1.5% to 3.7% and inter-assay precision was in the range from 1.6% to 5.4%. The method developed in this study had high sensitivity, good precision and accuracy, and a wide range of testing concentrations.

Shock wave synthesis of amino acids from solutions of ammonium formate and ammonium bicarbonate

AbstractThe emergence of life's building blocks, such as amino acids and nucleobases, on the prebiotic Earth was a critical step for the beginning of life. Reduced species with low mass, such as ammonia, amines, or carboxylic acids, are potential precursors for these building blocks of life. These precursors may have been provided to the prebiotic ocean by carbonaceous chondrites and chemical reactions related to meteorite impacts on the early Earth. The impact of extraterrestrial objects on Earth occurred more frequently during this period than at present. Such impacts generated shock waves in the ocean, which have the potential to progress chemical reactions to form the building blocks of life from reduced species. To simulate shock‐induced reactions in the prebiotic ocean, we conducted shock‐recovery experiments on ammonium bicarbonate solution and ammonium formate solution at impact velocities ranging from 0.51 to 0.92 km/s. In the products from the ammonium formate solution, several amino acids (glycine, alanine, ß‐alanine, and sarcosine) and aliphatic amines (methylamine, ethylamine, propylamine, and butylamine) were detected, although yields were less than 0.1 mol % of the formic acid reactant. From the ammonium bicarbonate solution, smaller amounts of glycine, methylamine, ethylamine, and propylamine were formed. The impact velocities used in this study represent minimum cases because natural meteorite impacts typically have higher velocities and longer durations. Our results therefore suggest that shock waves could have been involved in forming life's building blocks in the ocean of prebiotic Earth, and potentially in aquifers of other planets, satellites, and asteroids.

Quantification of Meranzin Hydrate in Rat Hippocampus and Plasma by LC–MS/MS: A Compound Derived from Chaihu–Shugan–San Displays Antidepressant Potential

Meranzin hydrate (MH), a compound derived from Chaihu–Shugan–San (CSS), displayed potent preclinical antidepressant functions. In this study, an LC–MS/MS method was developed and validated to quantify the MH in rat hippocampus and plasma. Tert-butyl methyl ether and irbesartan were used as the extraction reagent and the internal standard (IS), respectively. Chromatographic separation was achieved on a C18 column using the mobile phase, which consisted of a 20 mM solution of ammonium formate and acetonitrile at a ratio of 60:40. The flow rate was set at 0.3 mL min−1. The detection was performed by multiple reactions monitored in a positive ion mode via electrospray ionization. The transitions were monitored by m/z 279.1 → 188.9 for MH and m/z 429.0 → 206.9 for IS. Linear calibration curves were obtained in the concentration range of 0.70–278.29 ng mL−1, with a lower limit of quantification of 0.70 ng mL−1. The intra- and inter-day precision values were below 11.9 % relative standard deviation, and the accuracy was from 90.5 to 107.5 %. The recovery was from 85.7 to 89.5 %. The LC–MS/MS method was applied to quantify the MH in hippocampus tissue compared with that in plasma after intragastric administration of MH (9 mg kg−1) to rats. The results showed that the AUC(0–480), AUC(0–infinity), and Cmax values of MH in plasma were much higher than those values in the hippocampus of rats. Our study established a sensitive, reliable, and specific LC–MS/MS method for quantification of MH and confirmed the existence of MH in the rat hippocampus, which may contribute to antidepression mechanism research for MH in further study.

Simultaneous determination of pirfenidone and its metabolite in human plasma by liquid chromatography-tandem mass spectrometry: application to a pharmacokinetic study.

A simple and rapid analytical method for the simultaneous determination of pirfenidone and its metabolite, 5-carboxy-pirfenidone, in human plasma using liquid chromatography-tandem mass spectrometry has been developed and validated. Aliquots of plasma (0.1 mL) containing pirfenidone and 5-carboxy-pirfenidone, as well as deuterium-labeled internal standards (ISs), were deproteinized using acetonitrile. An Agilent Zorbax Plus C18 column was used for the chromatography, with isocratic elution. The mobile phase was a mixture of acetonitrile and aqueous ammonium formate solution (5 mM) containing 0.1% formic acid (60 : 40, v/v). Using multiple reaction monitoring in positive ionization mode, transitions m/z 186.1 → 65.1, m/z 216.0 → 77.0, m/z 191.1 → 65.1 and m/z 221.0 → 81.0 were chosen to quantify pirfenidone, 5-carboxy-pirfenidone and the two ISs, respectively. The time of analysis was <3 min. The calibration curve was linear over the concentration ranges 0.005-25 μg/mL for pirfenidone, and 0.005-15 μg/mL for 5-carboxy-pirfenidone. The lower limit of quantification for both analytes was 0.005 μg/mL. The intra- and interday precision and relative errors in quality control samples were between -11.7 and 1.3% for pirfenidone and between -5.6 and 2.5% for 5-carboxy-pirfenidone, with mean recoveries ≥90%. The method that has been developed is easy to carry out, sensitive and rapid, and has been successfully used to investigate the pharmacokinetics of pirfenidone in healthy human volunteers.

Determination of purine contents in different parts of pork and beef by high performance liquid chromatography

Determination of adenine, hypoxanthine, guanine and xanthine in different parts of pork and beef using high performance liquid chromatography was described. Chromatographic separation was carried out on Waters Atlantis T3 column (4.6mm×250mm×5μm) with column temperature at 30°C. The mobile phase contained 99% 10.0mmol/L ammonium formate solution at pH 3.6 and 1.0% methanol. Chromatography was achieved at a flow rate of 1.0mL/min and detection wavelength at 254nm. The results indicated that total purine amounts in pork rump and beef sirloin were higher than those in other parts (P<0.05). The principal purine bases were hypoxanthine and adenine, and hypoxanthine content was the most highest in all samples (P<0.05). As pork rump and beef sirloin contain considerable amounts of total purine and uricogenic purine base, we suggest that excess consumption of them be avoid, whereas pork loin chop and beef rib eye are more suitable for a low-purine diet.

Determination of urinary 8-hydroxy-2'-deoxyguanosine, trans, trans-muconic acid, and S-phenylmercapturic acid by liquid chromatography-mass spectrometry

To establish a method for simultaneously determining the urinary concentrations of 8-hydroxy-2'-deoxyguanosine (8-OHdG), trans, trans-muconic acid (tt-MA), and S-phenylmercapturic acid (S-PMA) in subjects exposed to benzene. After being purified by a solid-phase extraction column, the urine samples were transferred to a liquid chromatography-mass spectrometry system, and the concentrations of 8-OHdG, tt-MA, and S-PMA were determined by external standard method. A C18 reversed-phase column was used as the chromatographic column, and methanol/acidic ammonium formate solution was used as the mobile phase for gradient elution. The mass spectrometer was operated in a multi-reaction monitoring mode. For tt-MA, the calibration curves were linear in the range of 10-1000 µg/L, and the recovery rates were over 90% (relative standard deviation (RSD) < 3%) at spiked levels of 50 µg/L and 500 µg/L. For S-PMA and 8-OHdG, the calibration curves were linear in the range of 1-100 µg/L, and the recovery rates were over 85% (RSD < 5%) at spiked levels of 5 µg/L and 50 µg/L. This determination method meets the requirement of Biological materials- of monitoring-Guide of development (WS/T 68-1996) and can be used for simultaneous determination of 8-OHdG, tt-MA, and S-PMA in urine.

LC-MS/MS method for the quantification of carbinoxamine in human plasma

A simple, reverse-phase high performance liquid chromatographic method with mass spectrometric detection (HPLC-MS/MS) was developed for determination of carbinoxamine in human plasma using pargeverine HCl as an internal standard. The procedure involves a simple protein precipitation technique using BDS HYPERSIL C8 (100 x 4.6mm) column. The mobile phase used was acetonitrile: buffer (25mm ammonium formate solution) (80:20). Precipitation was done using acetonitrile and detection was done in MRM mode, using an Electro Spray positive ionization. The ion transition monitored was (m/z) carbinoxamine (Q1 Mass: 291.2; Q3 Mass: 167.1), Internal standard (Q1 Mass: 338.1; Q3 Mass; 167.0). The retention time of carbinoxamine and internal Standard were 1.61 and 1.75 respectively. Method was evaluated in terms of linearity, accuracy, precision, recovery, sensitivity. The simple extraction procedure and short chromatographic runtime make the method suitable for therapeutic drug monitoring studies. I. Introduction Carbinoxamine (CX) (2-((4-chlorophenyl)-pyridin-2-yl-methoxy)-N, N-dimethyl-ethanamine) (Fig. 1) is an antihistamine of the ethanolamine class. Ethanolamine antihistamines have significant antimuscarinic activity and produce marked sedation in most patients. In addition to the usual allergic symptoms, the drug also treats irritant cough and nausea, vomiting, and vertigo associated with motion sickness. It is also used commonly to treat drug-induced extrapyramidal symptoms as well as to treat mild cases of Parkinson's disease. Rather than preventing the release of histamine, as docromolyn and nedocromil, carbinoxamine competes with free histamine for binding at HA-receptor sites. Carbinoxamine competitively antagonizes the effects of histamine on HA-receptors in the GI tract, uterus, large blood vessels, and bronchial muscle. Ethanolamine derivatives have greater anticholinergic activity than other antihistamines, which probably accounts for the antidyskinetic action of carbinoxamine.

Development and Validation of a LC-MS/MS Method for the Simultaneous Estimation of Amlodipine and Valsartan in Human Plasma: Application to a Bioequivalence Study.

A reliable, simple, and robust liquid chromatography-tandem mass spectro-metric (LC-MS/MS) method has been developed and validated that employs solid-phase extraction for the simultaneous estimation of amlodipine and valsartan in human K3EDTA plasma using amlodipine-d4 and valsartan-d9 as internal standards. Chromatographic separation of amlodipine and valsartan was achieved on the Luna C18 (2)100A (150 × 4.6 mm, 5 μm) column using acetonitrile: 5 mM ammonium formate solution (80:20, v/v) as the mobile phase at a flow rate of 0.8 mL/min in isocratic mode. Quantification was achieved using an electrospray ion interface operating in positive mode, under multiple reaction monitoring (MRM) conditions. The assay was found to be linear over the range of 0.302–20.725 ng/mL for amlodipine and 6.062–18060.792 ng/mL for valsartan. The method has shown good reproducibility, as intra- and interday precisions were within 10% and accuracies were within 8% of nominal values for both analytes. The method was successfully applied for the bioequivalence study of amlodipine and valsartan after oral administration of a fixed dose of the combination. Additionally, as required by the current regulatory bodies, incurred sample reanalysis was performed and found to be acceptable.

Pentafluorophenylprophyl Ligand-based Liquid Chromatography-Tandem Mass Spectrometric Method for Rapid and Reproducible Determination of Metformin in Human Plasma

This paper describes first development and validation of pentafluorophenylprophyl ligand-based liquid chromatography coupled to tandem mass spectrometry (PFPLC-MS/MS) method to determine metformin, a highly polar compound, in human plasma. Metformin and Phenformin (internal standard) were extracted from human plasma 50 <TEX>${\mu}L$</TEX> with a single-step protein precipitation. The chromatographic separation was performed using a linear gradient elution of mobile phase involving 5.0 mM ammonium formate solution with 0.1% formic acid (A) and acetonitrile (B) over 3.0 min of run time on a Phenomenex Luna PFP column. The detection was performed using a triple-quadrupole tandem mass spectrometer (Waters Quattro micro) with electrospray ionization in the mode of positive ionization and multiple-reaction monitoring (MRM). The developed method was validated with 5.0 ng/mL of lower limit of quantification (LLOQ). The calibration curve was linear over 5-3000 ng/mL of the concentration range (<TEX>$R^2$</TEX> > 0.99). The specificity, selectivity, carry-over effect, precision, accuracy and stability of the method met the acceptance criteria. The method developed in this study had had rapidness, simplicity and ruggedness. The reliable method was successfully applied to high throughput analysis of real samples for a practical purpose of a pharmacokinetic study.

Simultaneous Determination of 11 Preservatives in Cosmetics by High-Performance Liquid Chromatography

Preservatives prevent the growth of microorganisms in foods, pharmaceuticals and cosmetics. There exist numerous restrictions regarding the maximum allowable levels of preservatives in cosmetics. We analyzed 11 regulated preservatives in commercial cosmetics and manufacturers need to analyze their products for quality control purposes. However, methods used in previous studies to date have been inadequate for use by public institutions and manufacturers. Therefore, an effective, scalable method for the analysis of preservatives in cosmetics is required. We developed a novel method for the simultaneous determination of 11 regulated preservatives in cosmetics by high-performance liquid chromatography (HPLC). We applied the samples to a C18 column in a simple mobile phase (5 mmol/L ammonium formate solution and acetonitrile) with gradient elution at a flow rate of 1.0 mL/min at a single wavelength (230 nm). The correlation coefficients of the calibration curves were >0.997. The percent recoveries were 92.8-111.9% and the relative standard deviations were <4.3% (n = 6). The peak resolution for all preservatives was >1.9. Because of the simple conditions for isolation and complete separation, the HPLC method can be effectively applied to the analysis of preservatives in commercially retailed cosmetics.

Rapid method for the determination of metamizole residues in bovine muscle by LC-MS/MS

Metamizole is a pyrazolone non-steroidal anti-inflammatory drug allowed for use in food-producing animals. According to Council Directive 96/23, residues of this drug have to be monitored because of the potential risk to consumers’ health. Metamizole is hydrolysed to its marker residue 4-methylaminoantypyrine.This compound is further metabolised to three main metabolites: 4-formylaminoantipyrine, 4-aminoantipyrine and 4-acetylaminoantipyrine. The MRL of 4-methylaminoantipyrine in animal tissues is 100 µg kg−1. Considering the above points, a method for the detection of four metamizole metabolites in bovine muscles was developed. Analytes were extracted from muscle by a mixture of acetonitrile and sodium acetate buffer. After centrifugation, the supernatant was passed through alumina cartridges, diluted with mobile phase and analysed by using LC-MS/MS. Four metamizole metabolites were separated on a C8 column in 23 min with a gradient of methanol:acetonitrile:ammonium formate solution and analysed by using positive ionisation. Validation of the method indicated a within-laboratory reproducibility in the range of 7–30% and recovery in the range of 45–95%. The method fulfils the criteria for confirmatory methods and, thanks to its labour efficiency, may also be used for screening purposes.

Simultaneous determination of 38 phosphodiestrase-5 inhibitors in illicit erectile dysfunction products by liquid chromatography–electrospray ionization-tandem mass spectrometry

This paper describes the development and validation of simultaneous analytical method for 38 compounds, sildenafil, tadalafil, vardenafil and their analogues in illicit erectile dysfunction (ED) products by the liquid chromatography–electrospray ionization-tandem mass method (LC–ESI-MS/MS). Chromatographic separation was performed on a C18 reversed-phase column using a gradient of solvent A: aqueous 2mM ammonium formate solution and solvent B: acetonitrile (ACN). All components were monitored under time-scheduled multiple reaction monitoring (MRM) mode. The limits of detection (LOD) ranged from 0.004ng/ml to 0.455ng/ml and the limits of quantification (LOQ) ranged from 0.012ng/ml to 1.5ng/ml. Calibration curves were linear with correlation coefficients over 0.9991. Mean recoveries ranged from 73.6% to 111.3%, and relative standard deviation (RSD) was less than 10%. The intra- and inter-day precision ranged from 0.2% to 16.3% and from 0.2% to 17.0%, respectively. The proposed method was applied to investigate the 52 illicit ED products.