A novel,simple and robust method for the analysis of sulfonamides in fish farming water samples using column switching liquid chromatography

A novel method for the online extraction and preconcentration of four sulfonamides was developed using column switching liquid chromatography. Sulfadiazine, sulfathiazole, sulfamethoxypyridazine and sulfamethoxazole were analysed in water samples and preconcentrated in a C18 guard column. Suitable validation parameters were obtained, such as precision, accuracy and relative recovery, in accordance with the validation guidelines of the Food and Drug Administration. Low limits of detection (0.05–0.09 µg L^?1) and quantification (0.30 µg L^?1, for all of them) were obtained. The quadratic polynomial model was used to adjust the calibration data, and the coefficients of determination were higher than 0.999 for all the analytes. The method was shown to be robust to the assayed parameters according to Youden’s test. The proposed method was successfully used to determine sulfonamides in 11 different fish farming water samples, in which sulfadiazine (0.732 µg L^?1), sulfamethoxazole (0.531 µg L^?1), sulfathiazole (0.546–1.856 µg L^?1) and sulfamethoxypyridazine (0.369–1.509 µg L^?1) were found.     

Validation of an HPLC Analytical Method for Determination of Pancuronium Bromide in Pharmaceutical Injections

Abstract

Pancuronium bromide is used with general anesthesia in surgery for muscle relaxation and as an aid to intubation. A high performance liquid chromatographic method was fully validated for the quantitative determination of pancuronium bromide in pharmaceutical injectable solutions. The analytical method was performed on an amino column (Luna® 150 mm × 4.6 mm, 5 µm). The mobile phase was composed of acetonitrile:water containing 50 mmol L^?1 of 1-octane sulfonic acid sodium salt (20:80 v/v) with a flow rate of 1.0 mL min^?1 and ultraviolet (UV) detection at 210 nm. The proposed analytical method was compared with that described in the British Pharmacopoeia.     

Large‐volume sample stacking with polarity switching for analysis of azo dyes in water samples by capillary electrophoresis

ABSTRACT

A simple, fast and efficient on-line pre-concentration method (large-volume sample stacking) by capillary electrophoresis was proposed for determination of azo dyes residues (allura red [AR], sunset yellow [SY] and tartrazine [TAR]) in water samples. Pre-concentration variables involved in the system were optimised using of a Box–Bhenken design. Under the optimal conditions: injection time 150.0 s, pre-concentration time 120.0 s and reverse potential ?8.0 kV, the proposed methodology improved the analytical sensibility achieving limits of detection of 21.0–41.4 µg L^?1 with enrichment factors of 82.1–210.8 fold. The large-volume sample stacking-capillary electrophoresis method was validated and applied to determine azo dyes residues in 20 water samples (bottled, spring and tap water). Two samples were positive for sunset yellow and tartrazine with a concentration of 25.3 and 30.2 µg L^?1 and % RSD less than 10.0% in all cases.     

Ion Chromatography with Post-column Reaction and Serial Conductivity and Spectrophotometric Detection Method Development for Quantification of Transition Metal Dissolution in Lithium Ion Battery Electrolytes

We present a method for the separation and determination of transition metals in electrolytes based on ion chromatography (IC) with post-column reaction (PCR) and serial conductivity and spectrophotometric detection. Three IC columns [Metrosep C4—250/4.0 (column A), Metrosep C6—250/4.0 (column B), and Nucleosil 100-5SA—250/4.6 (column C)] with different capacities, and stationary phases were used and compared with each other for method development. All spectrophotometric measurements were carried out with 4-(2-pyridylazo)resorcinol (PAR) as PCR reagent at a wavelength of 500 nm. To characterize the precision of the separation, the selectivity for the analysis of transition metals (nickel, cobalt, copper, and manganese) in the presence of large amounts of lithium and the resolution of the peaks were determined and compared with one another. Furthermore, the limits of detection (LOD) and quantification (LOQ) were determined for the transition metals. The LODs and LOQs determined by column C were as follows: cobalt (LOD/LOQ): 9.4 µg L^?1/31.3 µg L^?1, manganese (LOD/LOQ): 7.0 µg L^?1/23.5 µg L^?1, and nickel (LOD/LOQ): 6.3 µg L^?1/21.1 µg L^?1. Finally, the concentration of transition metal dissolution of the cathode material Li₁Ni_1/3Co_1/3Mn_1/3O₂ (NCM) was investigated for different charge cut-off voltages by the developed IC method.     

Development and validation of an LC–MS method for the simultaneous determination of sulfadiazine,trimethoprim, and N4-acetyl-sulfadiazine in muscle plus skin of cultured fish

An analytical method for the determination of both sulfadiazine (SDZ) and trimethoprim (TMP), and also N⁴-acetyl-sulfadiazine (AcSDZ), the main metabolite of SDZ, in fish muscle plus skin has been developed and validated. Dapsone was used as internal standard. The method involves extraction of the analytes from fish tissue by pressurized liquid extraction using water as extractant. Sample cleanup was carried out by solid phase extraction using Abselut Nexus cartridges. Target analytes were quantitatively determined by liquid–chromatography mass spectrometry using single ion monitoring. The developed method was validated according to the European Union requirements (decision 2002/657/EC). The limit of detection for SDZ and AcSDZ was 3.0 and 2.5 µg kg^?1 for TMP. The limit of quantification (LOQ) was 10 µg kg^?1 for SDZ and AcSDZ and 7.5 µg kg^?1 for TMP. The recovery experiments carried out included the concentration levels of 0.5, 1 and 1.5 times the MRLs for SDZ and TMP. Concentration levels for AcSDZ were the same as SDZ. The values obtained were higher than 92.0% with coefficient of variation (CV, %) below 8.6%. The precision of the method, calculated as CV (%), ranged from 0.2 to 6.8% and from 0.8 to 8.9% for intra–day and inter–day analysis, respectively. Decision limit (CC_α) was calculated as 104.3, 53.7 and 105.3 µg kg^?1 for SDZ, TMP and AcSDZ, respectively. Detection capability (CC_β) was calculated as 110.0, 58.8 and 109.7 µg kg^?1 for SDZ, TMP and AcSDZ, respectively. “Matrix effect” and “relative matrix effect” were also evaluated. The method was used for the analysis of fish samples purchased from local markets.     

Simple Method for Determination of Lead in Hair Dyes Using Slurry Sampling Graphite Furnace Atomic Absorption Spectrometry

A fast, simple and sensitive method for determining of lead in hair dyes using graphite furnace atomic absorption spectrometry with slurry sampling was developed. Multivariate optimization was used to establish optimal analytical parameters through a fractional factorial and a central composite design. The samples were submitted for direct analysis without prior digestion and were diluted in 2.5% v/v HNO₃ and 1.5% v/v H₂O₂. Palladium (chemical modifier) and rhodium (permanent modifier) were selected from several potential modifiers. The optimal conditions were a pyrolysis time of 10 s (liquid and dust dyes) 20 s (cream dyes), a pyrolysis temperature of 789°C (liquid dyes) or 750°C (cream and dust dyes) and an atomization temperature of 1800°C for all dyes. Under optimum conditions, the calibration graph is linear in the 1.50–50.0 µg L^?1 concentration range, with a detection limit of 0.33, 0.44, and 0.39 µg L^?1 for liquid, dust, and cream hair dyes, respectively. The relative standard deviation ranged from 1.63 to 4.56%. The recovery rate ranged from 85 to 108%, and no significant differences were found between the results obtained with the proposed method and the microwave decomposition analysis method of real samples. The concentration ranges obtained for lead in the hair dyes samples were 1.00–11.3 µg L^?1 for liquid dyes, 14.0–100 µg kg^?1 for dust dyes, and 19.9–187 µg kg^?1 for cream dyes.     

Characterization of Carbamate Pesticides in Natural Water from Cameroon

With the increased use of chemicals in agriculture for crop protection and improvement of yield, the contamination of water is currently a serious health concern. This study used solid-phase extraction with ultra-high-performance liquid chromatography–tandem mass spectrometry to evaluate the presence of 23 carbamate pesticides in waters from Cameroon. The separation was achieved in 5.5?min using a C₁₈ column (50?×?2.1?mm, 1.8?µm) with a mobile phase composed of water and methanol each containing 0.01% formic acid. The analytes were determined in positive multiple reaction monitoring mode. The recoveries for fortified water were from 75 to 99%, with relative standard deviations below 13%. The limits of detection ranged from 0.003 to 0.397?µg?L^?1. The reported method is simple, sensitive, and accurate, and is a suitable alternative for routine monitoring of pesticide residues at ultra-trace levels. The analysis revealed the presence of propoxur at a concentration of 0.072?µg?L^?1 in stream water.     

Custom-Made C18 Column for Simultaneous Determination of Endocrine Disrupting Substances in Water by Diode-Array and Fluorescence Detectors

A C₁₈ stationary phase was synthesized for a custom-made HPLC column. When compared to a commercial C₁₈ column, better chromatographic performances were obtained. This column was successfully applied for simultaneous determination of p,p′-DDT, o,p′-DDT, benzo(a)anthracene, benzo(b)fluoranthene, and benzo(a)pyrene in waters by high performance liquid chromatography coupled with dual detectors (diode array and fluorescence detectors) combined with solid phase extraction. Low method detection limits were obtained, i.e., p,p′-DDT: 0.5 µg L^?1, o,p′-DDT: 1 µg L^?1, benzo(a)anthracene: 2.5 ng L^?1, benzo(b)fluoranthene: 5 ng L^?1, and benzo(a)pyrene: 2.5 ng L^?1. High recoveries that ranged from 82 to 94% were obtained for all compounds.     

Rapid and Highly Sensitive HPLC and TLC Methods for Quantitation of Amlodipine Besilate and Valsartan in Bulk Powder and in Pharmaceutical Dosage Forms and in Human Plasma

Two simple, sensitive, and specific high-performance liquid chromatography and thin-layer chromatography methods were developed for the simultaneous estimation of Amlodipine besilate (AM) and Valsartan (VL). Separation by HPLC was achieved using a xTerra C18 column and methanol /acetonitrile /water/ 0.05% triethylamine in a ratio 40:20:30:10 by volume as mobile phase, pH was adjusted to 3 ± 0.1 with o-phosphoric acid. The flow rate was 1.2 mL min^?1. The linearity range was 0.2 to 2 µg mL^?1 for amlodipine besilate and 0.4 to 4 µg mL^?1 for Valsartan with a mean percentage recovery of 99.59 ± 0.523% and 100.61 ± 0.400% for amlodipine besilate and valsartan, respectively. The TLC method used silica gel 60 F₂₅₄ plates; the optimized mobile phase was ethyl acetate/ methanol / ammonium hydroxide (55:45:5 by volume). Quantitatively, the spots were scanned densitometrically at 237 nm. The range was 0.5–4.0 µg spot^?1 for amlodipine besilate and 2.0–12.0 µg spot^?1 for valsartan. The mean percentages recovery was 99.80 ± 0.451% and 100.61 ± 0.363% for amlodipine besilate and valsartan, respectively. The HPLC method was found to be simple, selective, precise, and reproducible for the estimation of both drugs from spiked human plasma.     

Evaluation of a cloud point extraction method for the preconcentration and quantification of silver nanoparticles in water samples by ETAAS

ABSTRACT

A simple and reliable analytical method using instrumentation available in most of the laboratories has been developed for the separation and determination of silver nanoparticles in water samples. Cloud point extraction (CPE) was used for the separation of silver nanoparticles (AgNPs) from the sample and these nanoparticles were then determined by electrothermal atomic absorption spectrometry (ETAAS). Parameters related to the cloud point extraction procedure (Triton X-114 concentration, type of complexing agent (EDTA or Na₂S₂O₃), pH, incubation temperature, incubation and centrifugation time) were selected using a multivariate approach (designs of experiments); 8.6% (v/v) Triton X-114, 750 µL saturated EDTA and pH 7 were selected as the optimum conditions. Calibration standards in a concentration range from 0 to 10 µg L^?1 of AgNPs were subjected to the CPE procedure to obtain quantitative recoveries. The LOD and LOQ were 0.04 and 0.13 µg L^?1, respectively. The method is selective for the extraction of AgNPs, and ionic Ag remains in the aqueous phase. Single particle inductively coupled plasma mass spectrometry (SP-ICP-MS) was used to evaluate the effect of the CPE procedure in particle size, and no changes were observed. Finally, the procedure was applied to wastewater samples spiked with nanoparticles with quantitative recoveries.     

Determination of Veterinary Pharmaceuticals in Production Wastewater by HPTLC-Videodensitometry

An SPE-HPTLC method for simultaneous identification and quantification of seven pharmaceuticals in production wastewater was optimized and validated. The studied compounds were enrofloxacine, oxytetracycline, trimethoprim, sulfamethazine, sulfadiazine, sulfaguanidine and penicillin G/procaine. The method involves solid-phase extraction on hydrophilic-lipophilic balance cartridges with methanol and HPTLC analysis of extracts on CN modified chromatographic plates followed by videodensitometry at 254 and 366 nm. Optimization of chromatographic separation was performed by systematic variation of the mobile phase composition using genetic algorithm approach and the optimum mobile phase composition for TLC separation was 0.05 M H₂C₂O₄:methanol = 0.81:0.19 (v/v). Linearity of the method was demonstrated in the ranges from 1.5 to 15.0 μg L⁻¹ for enrofloxacine, 100–500 μg L⁻¹ for oxytetracycline, 150–600 μg L⁻¹ for trimethoprim, 300–1100 μg L⁻¹ for sulfaguanidine and 100–400 μg L⁻¹ for sulfamethazine, sulfadiazine and penicillin G/procaine with coefficients of determination higher than 0.991. Mean recoveries ranged from 74.6 to 117.1% and 55.1 to 108.0% for wellspring water and production wastewater, respectively. Only sulfaguanidine showed lower results. The described method has been applied to the determination of pharmaceuticals in wastewater samples from pharmaceutical industry.     

Multivariate Analysis for the Classification Differentiation of Brazilian Sugarcane Spirits by Analysis of Organic and Inorganic Compounds

Abstract

Brazilian sugarcane spirits were analyzed to elucidate similarities and dissimilarities by principal component analysis. Nine aldehydes, six alcohols, and six metal cations were identified and quantified. Isobutanol (LD 202.9 µg L^?1), butiraldehyde (0.08–0.5 µg L^?1), ethanol (39–47% v/v), and copper (371–6068 µg L^?1) showed marked similarities, but the concentration levels of n-butanol (1.6–7.3 µg L^?1), sec-butanol (LD 89 µg L^?1), formaldehyde (0.1–0.74 µg L^?1), valeraldehyde (0.04–0.31 µg L^?1), iron (8.6–139.1 µg L^?1), and magnesium (LD 1149 µg L^?1) exhibited differences from samples.     

Use of ionic liquid based chitosan as sorbent for preconcentration of fluoroquinolones in milk,egg, fish,bovine, and chicken meat samples by solid phase extraction prior to HPLC determination

The possibility of using ionic liquid based chitosan sorbent for the separation and preconcentration of fluoroquinolone antibiotics (marbofloxacin, enoxacin, ofloxacin, ciprofloxacin, and enrofloxacin) has been studied. For this reason, different ionic liquids were prepared and coated on the chitosan sorbent. The conditions of the preconcentration of fluoroquinolones on a microcolumn have been optimized and the extraction efficiencies of the prepared sorbents have been compared. The compounds were eluted with 5 mL of 20% NH₃ (v/v, MeOH) solution and determined by HPLC with diode array and fluorescence detector. The limits of detection were found as 4.23 µ g L^?1 for marbofloxacin, and 1.09 µg L^?1 for enoxacin; 3.23 × 10^?3 µg L^?1 for ofloxacin; 8.39 × 10^?3 µg L^?1 for ciprofloxacin; and 19.50 × 10^?3 µg L^?1 for enrofloxacin. The developed method was applied for the analysis of fluoroquinolone in milk, egg, fish, bovine, and chicken samples and the recoveries were obtained in the range 70–100%.     

Application of bar adsorptive microextraction to determine trace organic micro-pollutants in environmental water matrices

The present work proposes the application of bar adsorptive micro-extraction (BAµE) coated with an N-vinylpyrrolidone polymer (NVP) combined with micro-liquid desorption (200 µL) followed by high-performance liquid chromatography with diode array detection (BAµE(NVP)-µLD/HPLC-DAD) for the determination of trace levels of emerging organic micro-pollutants in environmental water matrices. The model compounds selected include an antibacterial/antifungal agent (triclosan), two pharmaceuticals (carbamazepine and diclofenac) and two steroid hormones (17α-ethinylestradiol and 17β-estradiol), in which the latter three were recently included in the European Union watch list of substances to be monitored in the field of water policy. Assays performed on 25 mL of ultrapure water samples spiked at the 8.0 µg L^?1 level yielded average recoveries ranging from 81.9 to 102.4% for the compounds studied using optimised experimental conditions. The proposed analytical methodology demonstrated suitable detection limits (0.02–0.10 µg L^?1) and good linear dynamic ranges (0.1–20.0 µg L^?1) with determination coefficients higher than 0.9909. Using the standard addition method (SAM), the present analytical approach was applied on environmental water matrices, including surface, sea, river and groundwaters. The proposed method proved to be a suitable and alternative sorption-based static micro-extraction technique for monitoring trace levels of organic micro-pollutants in environmental water matrices.     

Electrochemical Oxidation of Astaxanthin on Glassy‐carbon Electrode and its Amperometric Determination Using Batch Injection Analysis (BIA)

This work presents the electrochemical oxidation of the antioxidant astaxanthin on a glassy‐carbon electrode (GCE) and its amperometric determination in salmon samples using a batch‐injection analysis (BIA) system. The proposed BIA method consisted of 80‐µL a fast microliter injection of sample at 193 µL s^?1 on the GCE immersed in the electrolyte, a mixture of acetone, dichloromethane, and water (80 : 10 : 10 v/v), containing 0.1 mol L^?1 HClO₄. Advantages include high precision (RSD of 2.4 %), sample throughput of 240 h^?1, and low detection limit (0.3 µmol L^?1 that corresponds to 0.1 µg g^?1) for the analysis of acetone extracts of salmon samples. Recovery values between 83 and 97 % attested the accuracy of the method.     

Simultaneous Determination of Nickel and Cobalt as Chelates with 1-(2-Pyridylazo)-2-naphthol Using an LC Switching Column Method

A simple liquid chromatographic method was developed for the separation and simultaneous determination of cobalt and nickel as chelates with 1-(2-pyridylazo)-2-naphthol (PAN). The method, using a switching column technique for the on-line purification and separation, enables to reach the sub-microgram per litre concentration level excluding off-line sample treatment with the exception of the derivatization reaction. Two small-sized columns packed with CN- and C₄-bonded stationary phases were selected and used considering their complementary behaviour with respect to chelated Co and Ni ions. The analysis was performed within 10 min using an optimised eluent (water–acetonitrile–methanol–tetrahydrofuran, 40:45:10:5, v/v/v/v) containing Tween 40 (10^?3 M) and acetate buffer (5 × 10^?3 M, pH 4.8). Detection was performed by UV-vis spectrophotometry (λ = 565 nm) permitting to reach quantification limits of 0.9 and 0.5 μg L^?1 for Co and Ni, respectively.     

Evaluation of Monolithic Columns for Determination of Formaldehyde and Acetaldehyde in Sugar Cane Spirits by High-Performance Liquid Chromatography

Abstract

High-Performance Liquid Chromatography (HPLC) conditions are described for separation of 2,4-dinitrophenylhydrazone (2,4-DNPH) derivatives of carbonyl compounds in a 10 cm long C₁₈ reversed phase monolithic column. Using a linear gradient from 40 to 77% acetonitrile (acetonitrile-water system), the separation was achieved in about 10 min—a time significantly shorter than that obtained with a packed particles column. The method was applied for determination of formaldehyde and acetaldehyde in Brazilian sugar cane spirits. The linear dynamic range was between 30 and 600 µg L^?1, and the detection limits were 8 and 4 µg L^?1 for formaldehyde and acetaldehyde, respectively.     

Determination of Total Arsenic in Wastewater and Sewage Sludge Samples by Using Hydride-Generation Atomic Fluorescence Spectrometry Under the Optimized Analytical Conditions

In this work, an improved hydride-generation atomic fluorescence spectrometry (HG-AFS) method for the determination of total arsenic (As) in wastewater and sewage sludge samples was applied. The samples were digested completely with mixtures of HNO₃ and HClO₄. Analytical conditions were studied and optimized through uniform experimental design U*₁₀(10⁸) combined with a single factor test. A mathematical model was established, and a quadratic polynomial stepwise regression analysis by using the DPS software was employed to obtain the factors that impact the fluorescence intensity. This technique is then combined with a single factor test. The optimized experimental conditions were obtained as follows: PMT voltage was 305 V, lamp current was 70 mA, KBH₄ concentration was 2.0% (m/v), carrier liquid (HCl) concentration was 5% (v/v), carrier gas (Ar) flow rate was 300 mL min^?1, and reaction acidity was 10% (v/v) HCl. The pre-reduction of all forms of As to As(III) was performed by using a mixed solution of 1% thiourea and 1% ascorbic acid. The content of total As was determined under the optimized experimental conditions. The detection limits for total As in wastewater and sewage sludge were 0.09 µg L^?1 and 0.01 mg kg^?1, respectively. The linear ranges were 0.24–100 µg L^?1, and the recovery was 91.0–102.0%. The relative standard deviation (RSD, n = 5) for eleven replicate measurements of the certified reference materials containing 60.6 ± 4.2 µg L^?1 As (certified sample of water) and 10.7 ± 0.8 mg kg^?1 As (certified sample of soil) were 3.1% and 1.6%, respectively. The proposed method was validated by the analysis of certified reference materials and was successfully applied to the determination of total As in real samples of wastewater and sewage sludge with satisfactory results.     

Determination of Triazines and N-Methylcarbamate Pesticides in Water by High-Performance Liquid Chromatography-Diode Array Detection

A rapid and selective method for the simultaneous determination of triazine herbicides (atrazine, its degradation product desethylatrazine, simazine, prometryn, terbutryn) and N-methylcarbamate insecticides (propoxur, carbaryl and methiocarb) in surface water has been developed. A 0.5 L of the water sample was preconcentrated by passage through a 1 g C₁₈ solid-phase extraction cartridge. The retained compounds were eluted with 5 mL of methanol from the cartridge. The pesticides were separated and quantified by reversed-phase high-performance liquid chromatography with UV diode-array detection. Analytical separation was performed using a concave gradient elution with acetonitrile and water on a C₁₈ column. Prometryn and terbutryn were determined at 240 nm; propoxur, methiocarb at 204 nm and the others at 220 nm. Recoveries varied from 85 to 102% over concentrations at 0.025 and 0.2 µg L^?1. The limits of detection for the compounds investigated are in the range of 0.005-0.012 µg L^?1.     

Trace Determination of Manganese in Urine by Graphite Furnace Atomic Absorption Spectrometry and Inductively Coupled Plasma–Mass Spectrometry

This paper describes a simple and sensitive method for the determination of manganese in human urine by graphite furnace atomic absorption spectroscopy (GFAAS), which includes sample preparation by microwave digestion. Matrix modifier combinations, the digestion power, pyrolysis, and atomization temperatures were optimized. A mixture of 5.0 µg Pd(NO₃)₂ and 3.2 µg Mg(NO₃)₂ modifier presented the best performance. The optimal temperatures for pyrolysis and atomization were 1500°C and 1950°C, respectively. The GFAAS method was compared to inductively coupled plasma–mass spectrometry (ICP–MS) for the determination of manganese in urine. Analytical figures of merit for GFAAS and ICP–MS were: accuracy (3.46%, 2.19%), precision (3.61%, 5.84%), LOD (0.109 µg · L^?1, 0.015 µg · L^?1), LOQ (0.327 µg · L^?1, 0.045 µg · L^?1), and recovery (80–100%, 74–89%). Both methods were employed for the determination of Mn in urine and the results were compared statistically.