An easy and green assay to determine albendazole and ivermectin in veterinary preparations by micellar liquid chromatography.

A procedure to determine albendazole and ivermectin in veterinary formulations, like tablet, bolus, oral suspensions, and injections by micellar liquid chromatography, has been developed. Sample preparation was a batch solid-to-liquid extraction in mobile phase, consisting of a stirring step (15 min), followed by ultrasonication (15 min) and filtration of the obtained supernatant, to reach a target concentration of 2 mg/L for both analytes. Using a mobile phase of 0.15 M sodium dodecyl sulfate-6% 1-pentanol buffered at pH 3 with a 0.01 M phosphate salt, running at 1 mL/min through a C18 column, both drugs were resolved in less than 10 min. Absorbance detection wavelength was 292 nm. Procedure was validated by the guidelines of the International Council on Harmonization in terms of specificity, calibration range (0.025-5 mg/L), trueness (97.8%-102.6%), precision (<2.2%), and system suitability. The method was found easy-to-handle, low cost, safe, green, and with high sample-throughput, thus useful for routine analysis. Therefore, it represents a valuable alternative for quality control of veterinary formulations. It was applied to samples of veterinary formulations purchased from local chemists and veterinarians, and label claims were inside the acceptance criteria (95%-105%).

A rapid and reliable assay to determine flumequine, marbofloxacin, difloxacin, and sarafloxacin in commonly consumed meat by micellar liquid chromatography.

BACKGROUND: Micellar liquid chromatography - fluorescence detection was used to determine the antibiotics flumequine, marbofloxacin, difloxacin, and sarafloxacin in porcine, bovine, poultry, ovine, caprine, rabbit, and equine meat, to verify compliance with EU Regulation 37/2010 with regard to the occurrence of veterinary drugs in food. RESULTS: The analytes were isolated from the matrix by ultrasonication-assisted leaching in a micellar solution, and the supernatant was filtered and directly injected. The fluoroquinolones were resolved in < 19 min using a C18 column, with an isocratic mobile phase of 0.05 mol L-1 sodium dodecyl sulfate - 8% 1-butanol - 0.5% triethylamine buffered at pH 3. The limits of quantification (0.01-0.05 mg kg-1 ) were below the maximum residue limits (0.15-0.4 mg kg-1 ). The method was validated by EU Commission Decision 2002/657/EC guidelines. CONCLUSION: The method shows practical advantages such as simplicity, low cost, eco-friendliness, safety, and applicability for routine analysis, and is useful for surveillance programs. © 2018 Society of Chemical Industry.

Validation of a procedure to quantify oxolinic acid, danofloxacin, ciprofloxacin and enrofloxacin in selected meats by micellar liquid chromatography according to EU Commission Decision 2002/657/EC.

The suitability of an analytical method to determine oxolinic acid, danofloxacin, ciprofloxacin and enrofloxacin in edible tissues, based on micellar liquid chromatography coupled with fluorescence detection, to be applied in chicken, turkey, duck, lamb, goat, rabbit and horse muscle, is described. The method was fully matrix-matched in-lab revalidated, for each antimicrobial drug and meat, following the guidelines of the EU Commission Decision 2002/657/EC. The permitted limits were the maximum residue limits stated by the EU Commission Regulation 37/2010. The results obtained for the studied validation parameters were in agreement with the guidelines: selectivity (the antibiotics were resolved), linearity (r2  > 0.995), limit of detection (0.004-0.02 mg/kg), limits of quantification (0.01-0.05 mg/kg), calibration range (up to 0.5 mg/kg), recovery (89.5-105.0%), precision (<8.3%), decision limit, detection capability, ruggedness, stability and application to incurred samples. The method was found to be able to provide reliable concentrations with low uncertainty within a large interval, including the maximum residue limits, and then was useful to find out prohibited contaminated samples. The method did not require to be adapted for these matrices, and then it maintained its interesting advantages: short-time, eco-friendly, safe, inexpensive, easy-to-conduct, minimal manipulation and useful for routine analysis.

Use of micellar liquid chromatography for rapid monitoring of fungicides post harvest applied to citrus wastewater.

A method based on micellar liquid chromatography has been developed to simultaneously monitor four pesticides largely post-harvest applied to citrus: thiabendazole, pyrimethanil, o-phenylphenol and imazalil. Water samples were filtered and directly injected without other treatment, thus avoiding extraction steps. The composition of the mobile phase was optimized using a chemometrical approach to achieve and excellent resolution to 0.07 mol/L SDS/5%, V/V 1-pentanol buffered at pH3. Mobile phase run through a C18 column at 1 mL/min at room temperature. The detection was performing by UV-Visible absorbance using a wavelength program: 0-10 min, 305 nm (for thiabendazole); 10-12; 265 nm (for pyrimethanil) and 12-18, 220 nm (o-phenylphenol and imazalil). The developed method was validated following the guidelines of the US Environmental Protection Agency in terms of: quantitation range, (0.5-4 to 15 µg/mL), linearity (r(2)>0.9995), sensitivity (LOD, 0.18-1.4 µg/mL), precision (<9.2%), trueness (93.9%-103.7%), and ruggedness (<9.9%). It was found that the fungicides remain up to eight days in surface water at outdoor conditions. The method was used to screen the presence of the analytes in several waste water samples, and was proved to be useful in routine analysis.

Analysis of thiabendazole, 4-tert-octylphenol and chlorpyrifos in waste and sewage water by direct injection ­ micellar liquid chromatography.

A micellar liquid chromatographic method has been developed for the simultaneous quantification of the pesticides thiabendazole and chlorpyrifos, as well as an alkylphenol, which is included in pesticide formulations, i.e., 4-tert-octylphenol, in water. A sample was filtered and directly injected, avoiding large extraction steps using toxic solvents, thus expediting the experimental procedure. The contaminants were eluted without interferences in <17 min, using a mobile phase of 0.15 M sodium dodecyl sulfate ­ 6% 1-pentanol buffered at pH 3, running through a C18 column at 1 mL min(-1) under the isocratic mode. This optimal mobile phase was selected using a statistical approach, which considers the retention factor, efficiency and peak shape of the analytes measured in only a few mobile phases. The detection was carried out by measuring absorbance at 220 nm. The method was successfully validated in terms of specificity, calibration range (0.5-10 mg L(-1)), linearity (r(2) > 0.994), limit of detection and quantification (0.2-0.3; and 0.5-0.8 mg L(-1), respectively), intra- and interday accuracy (95.2-102.9%), precision (<8.3%), and ruggedness (<9.3%). The stability in storage conditions (at least 14 days) was studied. The method was safe, inexpensive, produced little pollutant and has a short analysis time, thus it is useful for the routine analysis of samples. Finally, the method was applied to analyse wastewater from the fruit-processing industry, wastewater treatment plants, and in sewage water belonging to the Castelló area (Spain). The results were similar to those obtained by an already reliable method.

Use of micellar liquid chromatography to analyze darunavir, ritonavir, emtricitabine, and tenofovir in plasma.

Danuravir, ritonavir, emtricitabine, and tenofovir are together prescribed against AIDS as a highly active antiretroviral therapy regimen. Micellar liquid chromatography has been applied to determine these four antiretroviral drugs in plasma. The sample preparation is shortened to the dilution of the sample in a micellar solution, filtration, and injection. Clean-up steps are avoided, due to the solubilization of plasma matrix in micellar media. The drugs were analyzed in <20 min using a mobile phase of 0.06 M sodium dodecyl sulfate/2.5% 1-pentanol (pH 7) running under isocratic mode through a C18 column at 1 mL/min at room temperature. Absorbance wavelength detection was set at 214 nm. The method was successfully validated following the ICH Harmonized Tripartite Guideline in terms of selectivity, limit of detection (0.080-0.110 µg/mL), limit of quantification (0.240-0.270 µg/mL), linearity between 0.25 and 25 µg/mL (r(2) > 0.995), accuracy (89.3-103.2%), precision (<8.2%) and robustness (<7.5%). Real plasma sample from patients taking this therapy were analyzed. This is the first paper showing the simultaneous detection of this four drugs. Therefore, the methodology was proven useful for the routine analysis of these samples in a hospital laboratory for clinical purposes.

Evaluating the effectiveness of different household washing techniques for removal of insecticides from spinach and chickpea leaves by micellar liquid chromatography.

In the past few decades, the employment of green analytical approaches in chromatographic method development has attracted the analytical separation community. The greenness of the developed method depends upon the toxicity of solvents and the amount of generated post-analysis waste generated. In this concern, micellar liquid chromatography (MLC) is a simple and rapid technique that generates very low toxic waste compared to traditional chromatographic pesticide detection methods. Here, MLC method has been validated and applied for the determination of monocrotofos (MCF), imidacloprid (ICP), dimethoate (DM) and profenofos (PFF) in spinach and chickpea leaves. The optimized mobile phase was 0.065 M SDS-2 % 1-propanol, 0.01 M NaH2PO4 buffered to pH 7. A C18 column was used for separation with a flow rate of 1 mL/min. The developed method has been validated following the guidelines of SANTE/11,312/2021 and ICH guidelines for; limit of quantification (0.05-0.20 mg/kg), linearity (r2> 0.997-0.999), precision (<6.3 %), accuracy (96.3 %-99.8 %) and robustness (<6) in real samples. ICP and MCF, apart from DM and PFF, were detected in the present work. After detecting insecticides in spinach and chickpea leaves both were washed with different household chemicals i.e. normal, lukewarm, common salt, lemon juice water and commercial ozonizer. Based on five washing techniques with insecticide concentration time intervals reduction rates were calculated for each washing treatment. The results show that lemon juice, common salt water, and ozonizer can be used as washing techniques for the reduction of superficial and systematic residues of ICP and MCF. Common salt and lemon juice water were better for washing over vinegar and potassium permanganate (KMnO4) as they enhance the colour of the green leafy vegetables and are available in every Indian kitchen. They can be easily used by lower socioeconomic classes who cannot afford KMnO4 and vinegar.

Quantification of melamine in drinking water and wastewater by micellar liquid chromatography.

Because of the large potential health impact caused by deliberate contamination with the synthetic chemical melamine of different products for human and animal consumption, the World Health Organization and the Food and Agriculture Organization of the United Nations provided a range of recommendations in order to facilitate obtaining needed data, among which was the determination of the background levels of melamine in drinking water and wastewater (December 4, 2008). A chromatographic procedure using a C18 column, a micellar mobile phase consisting of sodium dodecyl sulfate (0.1 M), and 1-propanol (7.5%) buffered at pH 3, and detection by absorbance at 210 nm is reported in this paper for the quantification of melamine in drinking water and wastewater. Samples were filtered and directly injected into the chromatographic system, thus avoiding an extraction procedure. The optimal mobile phase composition was obtained by a chemometrics approach that considered the retention factor, efficiency, and peak shape. Melamine was eluted in about 6.2 min without interferences. Validation was performed following U.S. Food and Drug Administration guidelines. The analytical parameters studied were linearity (0.03-5 microg/mL, R2 = 0.998), LOD (13 nglmL), intraday and interday accuracy (between 4.1 and 12.2%), intraday and interday precision (less than 14.8%), and robustness (RSD < 5.1% for retention time and <9.0% for area). The proposed methodology was successfully applied for analysis of local wastewater and drinking water, in which no melamine was found.

Micellar enhanced chromatographic separation of selected hazardous chemical present in hair dye and their detection in formulations and swab, including assessment of damage caused to cuticle of hair shaft.

Hydroquinone (HQ), resorcinol (RS), m-aminophenol (m-AMP) and p-phenylenediamine (p-PPD) are aromatic compounds which are generally used in hair dyes to provide different colours to hair. In European Union the concentrations of HQ, RS, m-AMP and p-PPD is regulated in hair dyes and other cosmetic products by EU commission regulation EU/2019/831. This legislation is generally exercised because all these compounds are toxic and may cause severe allergies when used regularly. However in India no such regulations exist to monitor these toxic compounds in hair dyes therefore in this study a simple, rapid, economical and ecofriendly micellar liquid chromatographic (MLC) technique has been developed which can monitor all the selected toxic compounds simultaneously. HQ and RS are positional isomers and are difficult to be separated by HPLC whereas with the developed MLC method it was well separated and detected. The developed MLC technique has been applied to detect and quantify selected analytes in oxidative and non-oxidative hair dyes and swab samples from the scalp. The simultaneous separation of selected analytes was performed in mobile phase 0.09 M SDS, 0.01 M NaH2PO4-2% v/v 1-butanol at pH 7 running through C18 column under isocratic mode at 1 mL/min. flow rate. All the analytes were eluted within 6 min. The present method has been validated following the EURCHEM Guideline, 2014 in terms of calibration range (0.08-15 µg/mL), limit of detection (0.01-0.09 µg/mL), limit of quantification (0.08-0.35 µg/mL), accuracy (<5.6%), precision (91-105%) and robustness (<5.8%). The selected compounds in hair dye formulation were found in the range of 0.06-12.2 µg/mL (when diluted 25 times). Hair dyes persistence study was conducted up to 10 days from the day of application on the scalp, suggesting that the dyes were not completely washed off and were retained on the scalp for more than one week. SEM analysis of dyed hair revealed that hair are severely damaged due to use of dyes. The advantage of the developed method is that it could easily be adopted by quality control and cosmetic laboratories for quality control and check for the simultaneous separation of positional isomers together with two other aromatic compounds.

A method to determine two antibiotics prescribed to treat nosocomial infections in plasma and urine by micellar liquid chromatography.

Combined prescription of the antimicrobial drugs linezolid and meropenem is a common strategy to treat multidrug-resistant nosocomial infections. We propose an innovative method to determine these two drugs in plasma and urine, based on micellar liquid chromatography. Both biological fluids were diluted in mobile phase, filtered and directly injected, without any extraction step. Using a C18 column and a mobile phase of 0.1 M sodium dodecyl sulfate - 10 % methanol, phosphate buffered at pH 3, running under isocratic mode, both antibiotics were eluted without overlapping in<15 min. Detection was by absorbance: 255 nm for linezolid and 310 nm for meropenem. The influence of sodium dodecyl sulfate and methanol concentration on retention factor was established for both drugs using an interpretative approach assisted by chemometrics. The procedure was successfully validated following the guidelines of 2018 Bioanalytical Method Validation Guidance for Industry in terms of: linearity (determination coefficients over 0.99990), calibration range (1 - 50 mg/L), instrumental and method sensitivity, trueness (bias of -10.8 to + 2.4%), precision (relative standard deviation of < 10.2%), dilution integrity, carry-over effect, robustness and stability. It should be emphasized that the method uses low volumes of toxic and volatile solvents and can be achieved in a short period. The procedure was found useful for routine analysis, as it was cost-affordable, more eco-friendly and safer than hydroorganic HPLC, easy-to-handle and highly sample-throughput. Finally, it was applied to incurred samples of patients taking this medication.

Micellar liquid chromatography as a sustainable tool to quantify three statins in oral solid dosage forms.

A method based on micellar liquid chromatography has been developed to determine rosuvastatin, lovastatin and simvastatin in oral solid dosage forms. Samples were solved in mobile phase up to the target concentration, filtered and directly injected. The three statins were resolved in 30 min, using an aqueous solution of 0.10 M sodium dodecyl sulfate - 7.0% 1-butanol, buffered at pH 3 with 0.01 M phosphate salt as mobile phase, running under isocratic mode at 1 mL/min through a C18 column. Detection was at 240 nm. The effect of sodium dodecyl sulfate on elution strength was more important than that of the organic solvent. The procedure was successfully validated by the guidelines of the International Council for Harmonization in terms of: specificity, linearity (r2 > 0.990), calibration range (1.5 - 15 mg/L for rosuvastatin, 0.5-10 mg/L for lovastatin and simvastatin), limit of detection (0.4, 0.2 and 0.15 mg/L for rosuvastatin, lovastatin and simvastatin, respectively), trueness (98.8-101.7%), precision (<2.7%), carry-over effect, robustness, and stability. Values were inside the acceptance criteria of the Methods, Method Verification and Validation, Food and Drug Administration-Office of Regulatory Affairs, thus ensuring the reliability of the results. The main feature was the low proportion of organic solvent used, thus making the procedure sustainable and green. Besides, it was easy-to-conduct and with high sample-throughput, and then useful for routine analysis in pharmaceutical quality control. Finally, it was applied to commercial pharmaceutical preparations.

Use of micellar mobile phases for the chromatographic determination of melamine in dietetic supplements.

Melamine is a nitrogen-rich industrial chemical which is occasionally used to increase the apparent protein content of different products destined for human and animal consumption. In this work, a liquid chromatographic procedure that uses micellar mobile phases of sodium dodecyl sulfate (SDS) buffered at pH 3, a C18 column and UV detection is reported for the determination of melamine in dietetic supplements. Samples were reconstituted with a SDS solution and were directly injected, thus avoiding long extraction and experimental procedures. Melamine was eluted in less than 10 min with no interference by other compounds of the matrices. The optimum mobile phase composition was taken by a chemometrical approach that considers the retention factor, efficiency and peak shape. Validation was performed following the indications of the European Commission (Decision 2002/657/EC). The following parameters were considered: linearity (0.02-100 µg mL(-1); R(2) = 0.9996), intra- and inter-day precisions (<12.4%), accuracy (90.0-101.3%), and robustness (less than 9.8% and 5.1%, for retention time and peak area, respectively). The limits of detection and quantification were 9 and 20 ng mL(-1), respectively. Recoveries for several spiked samples were in the 85.8-114.3% range. These results indicate that the proposed methodology is useful for routine analysis of control quality of infant formula and adult dietetic supplements.

Direct injection green chromatographic method for simultaneous quantification of amoxicillin and amikacin in maternity hospital wastewater (Sagar, India).

Amoxicillin (AMO) and amikacin (AMK) are broad-spectrum antibiotics that are most preferably given post-delivery (normal and cesarian) in the maternity hospitals located in Sagar city (Madhya Pradesh), India. Both the antibiotics make their way through sewage/drainage systems into the environment in the form of metabolized and unmetabolized compounds. Growing concern about the contamination of wastewater by antibiotics requires fast, sensitive and eco-friendly techniques. Therefore a simple, rapid and environmental friendly chromatographic method has been developed for simultaneous determination of AMO and AMK in maternity hospital wastewater samples. A micellar liquid chromatographic (MLC) method was developed with a C18 column (250 mm × 4.6 mm), sodium dodecyl sulphate (SDS; 0.15 M), 1-butanol (7%) as a modifier, pH 5 and photo diode detector (PDA) at 270 nm and 256 nm for AMO and AMK respectively. The method was fast with analysis time below 9 min. In the present MLC method, linearities (r > 0.998), limits of quantification in the range of 0.02-0.04 µg/mL, repeatabilities, and intermediate precision below 4.9% were adequate for the quantification of AMO and AMK. The proposed method can be utilized to detect and quantify both the antibiotics in various samples by hospitals, pharmaceutical companies, pollution control board, municipal corporations, etc.

Development and validation of micellar liquid chromatographic methods for the determination of antibiotics in different matrixes.

Antibiotics are the most important bioactive and chemotherapeutic compounds to be produced by microbiological synthesis, and they have proved their worth in a variety of fields, such as medicinal chemistry, agriculture, and the food industry. Interest in antibiotics has grown in parallel with an increasingly high degree of productivity in the field of analytical applications. Therefore, it is necessary to develop chromatographic procedures capable of determining various drugs simultaneously in the shortest possible time. Micellar liquid chromatography (MLC) is an RP-HPLC technique that offers advantages over conventional HPLC as far as sample preparation, selectivity, and versatility are concerned. Its main advantage is that samples can be injected directly into the chromatographic system with no previous preparation step. This paper mainly focuses on the results of the authors' own recent research and reports the chromatographic conditions for determination of various antibiotics (penicillins, quinolones, and sulfonamides) in different matrixes (pharmaceuticals, biological fluids, and food). The work of other authors on MLC-based antibiotic determination has been included.

Determination of the insecticide imidacloprid in fruit juices using micellar high-performance liquid chromatography.

A simple and reliable HPLC method was developed to determine imidacloprid, a chloronicotinyl insecticide that has a highly specific affinity to the nicotinic acetylcholine receptor of insects, above its permissible limit of consumption in fruit juices (orange, apple, and a mixture of pineapple and pear). Samples were injected directly into a Kromasil C18 column, without any pretreatment step, using the micellar mobile phase 0.10 M sodium dodecyl sulfate and 2.5% (v/v) propanol buffered at pH 7 and UV detection at 210 nm. Under these conditions, imidacloprid was eluted in < 4 min with no interference by the endogenous compounds of the juice fruits. The analytical parameters' linearity (r > 0.9998) and intraday and interday precision (RSD 0.1-2.8 and 0.07-7%, respectively) were obtained in the method validation. LOD and LOQ were calculated to be 0.4 and 1.5 ng/mL, respectively. Recoveries were in the 98-103% range. The simplicity of the method makes it a good candidate for application in routine analysis in the area of food control and quality evaluation.

Procedure for the Screening of Eggs and Egg Products to Detect Oxolonic Acid, Ciprofloxacin, Enrofloxacin, and Sarafloxacin Using Micellar Liquid Chromatography.

A method based on micellar liquid chromatography was developed to determine oxolinic acid, ciprofloxacin, enrofloxacin, and sarafloxacin in eggs and egg products. The antimicrobial drugs were obtained in a micellar solution which was directly injected. The analytes were resolved using a C18 column and a mobile phase of 0.05 M sodium dodecyl sulfate-7.5% 1-propanol-0.5% triethylamine, buffered at pH 3 with phosphate salt, running under the isocratic mode. The signal was monitored by fluorescence. Validation was successfully performed according to the EU Commission Decision 2002/657/EC in terms of specificity, calibration range (LOQ to 1 mg/kg), linearity (R2 > 0.9991), limit of detection and decision limit (0.01-0.05 mg/kg), limit of quantification (0.025-0.150 mg/kg), detection capability (<0.4 times decision limit), trueness (-14.2% to +9.8%), precision (<14.0%), robustness, and stability. The procedure was environmentally friendly, safe, easy-to-conduct, inexpensive, and had a high sample throughput, thus it is useful for routine analysis as a screening method in a laboratory for food residue control.

Anserine and carnosine determination in meat samples by pure micellar liquid chromatography.

Anserine and carnosine, which are both imidazole dipeptides, are natural antioxidants that are present in some types of meat. A pure micellar liquid chromatographic procedure was developed using a micellar mobile phase of 0.10 M sodium dodecyl sulphate buffered at pH 7, an amino column and UV detection. Three types of stationary phases (C18, phenyl and amino columns) were examined and the procedure was used to determine the two compounds in meat samples. They were completely resolved without any interference from the protein band. Total analysis time was 12 min. The limits of detection (ng/mL) were 71 and 53 for anserine and carnosine, respectively. Calibration curves were constructed on three different days (r>0.998). Repeatability and intermediate precision were evaluated at three different concentrations in meat matrices, the residual standard deviations being below 2.1%. Meat samples of poultry, pork and beef were injected directly into the chromatographic system after extraction in a sodium dodecyl sulphate solution and filtration. The possibility of direct injection using micellar liquid chromatography reduces the cost and time of analyses, and decreases error sources owing to minimised risks of losses and chemical changes in the analytes. Moreover, the selection of a pure mobile phase of sodium dodecyl sulphate allows this procedure to offer a number of advantages, such as non-toxicity, non-flammability, biodegradability and low cost, in comparison with aqueous-organic solvents. Its simplicity, then, makes it a good candidate for application in routine analysis in the area of food control and quality.

Development and validation of a method to determine amoxicillin in physiological fluids using micellar liquid chromatography.

A simple and robust method was developed for the routine identification and quantification of amoxicillin by micellar LC. Amoxicillin, a beta-lactamase inhibitor, is one of the most commonly prescribed drugs in the treatment of urine and skin structure infections. In this work, amoxicillin was determined in urine samples without any pretreatment step in a phenyl column using a micellar mobile phase of 0.10 M SDS and 4% butanol at pH 3. A UV detection set at 210 nm was used. Amoxicillin was eluted at 5.1 min with no interference by the protein band or endogenous compounds. Linearities (r >0.9998), intra- and interday precisions were determined (RSD (%) 0.4-2.7% and 0.3-5%, respectively, in micellar media, and 0.14-2.6% and 0.13-6%, respectively, in urine), and robustness was studied in the method validation. LOD and LOQ were 0.04 and 0.1 microg/mL in micellar media and 0.14 and 0.34 microg/mL in urine, respectively. Recoveries in the urine matrix were in the range of 95-110%. The validated method proved to be reliable and sensitive for the determination of amoxicillin in urine samples.

Optimization and Validation of a Chromatographic Method for the Quantification of Isoniazid in Urine of Tuberculosis Patients According to the European Medicines Agency Guideline.

Isoniazid is a drug that is widely used against tuberculosis. However, it shows high interpatient variability in metabolism kinetics and clinical effect, which complicates the prescription of the medication and jeopardizes the success of the therapy. Therefore, in a specific patient, the pharmacokinetics of the drug must be elucidated to decide the proper dosage and intake frequency to make the drug suitable for therapeutic drug monitoring. This can be performed by the quantification of the drug in urine as this process is non-invasive and allows the effects of long-time exposure to be inferred. The paper describes the development of a micellar liquid chromatographic method to quantify isoniazid in urine samples. Extraction steps were avoided, making the procedure easy to handle and reducing the waste of toxic organic solvents. Isoniazid was eluted in less than 5 min without interference from other compounds of the urine using a mobile phase containing 0.15 SDS⁻12.5% 1-propanol (v/v)⁻Na2HPO4 0.01 M buffered at pH 7, running at 1 mL/min under isocratic mode through a C18 column with the detection wavelength at 265 nm. The method was validated by following the requirements of the Guidelines on Bioanalytical Method Validation issued by the European Medicines Agency (EMA) in terms of selectivity, calibration curve (r² = 0.9998 in the calibration range (0.03⁻10.0 µg/mL), limit of detection and quantification (10 and 30 ng/mL respectively), precision (<16.0%), accuracy (-0.9 to +8.5%), carry-over, matrix effect, and robustness. The developed method was applied to quantify isoniazid in urine samples of patients of an Indian hospital with good results. The method was found to be useful for routine analysis to check the amount of isoniazid in these patients and could be used in its therapeutic monitoring.

Solvent systems for countercurrent chromatography: an aqueous two phase liquid system based on a room temperature ionic liquid.

A new aqueous two phase liquid system (ATPS) based on the ionic liquid 1-butyl-3-methyl imidazolium chloride (BMIM Cl), potassium dibasic phosphate (K(2)HPO(4)) and water was recently proposed in the literature. The full phase diagram of this ATPS was prepared and some tie lines were fully determined. It was compared to classical ATPSs based on polyethylene glycol with an average molecular mass of 1000 (PEG 1000) and 10,000 (PEG 10000) and K(2)HPO(4). Two countercurrent chromatography (CCC) columns, a hydrostatic Sanki and a J type hydrodynamic CCC columns were used to test the liquid phase retention of these ATPSs in all possible configurations. It was found that the BMIM Cl ATPS liquid phases were much easier to retain in the two CCC columns than the PEG 1000 ATPS phases. Using protein and alcohol solutes, it was established that the BMIM Cl ATPS has a polarity completely different from that of the PEG 1000 ATPS. For example, ovalbumin partitions equally between the two phases of the PEG 1000 ATPS (K(D)=1.4) when it is completely located in the BMIM Cl upper phase of the ionic liquid ATPS (K(D)=180). The discrimination factor of the ionic liquid system and its intrinsic hydrophobicity were respectively found three times higher and ten times lower than the respective values of the PEG 1000 ATPS.