Chlorobutanol Research Articles

Unusual addition of hydrogen chloride to N-substituted quinone imines

Addition of hydrogen chloride to quinones and N-substituted quinone imines follows 1,4[1] or 6,3-addition pattern [2], leading to aromatization of the quinoid ring with introduction of chlorine into the aromatic ring. We found that 4-[2-(4-nitrobenzylidene)hydrazono]cyclohexa-2,5-dien-1-one (I) reacts with hydrogen chloride to give 4-[2-(α-chloro-4-nitrobenzylidene)hydrazino]phenol (II). This reaction is unusual, for no chlorine atom is introduced into the aromatic ring, but highly reactive imidoyl chloride II is obtained. 4-[2-(α-Chloro-4-nitrobenzylidene)hydrazino]phenol (II). Concentrated hydrochloric acid, 5 ml, was added to a solution of 1.0 g (4 mmol) of compound I in 100 ml of glacial acetic acid, the mixture was stirred for 45 min, 100 ml of methylene chloride and 150 ml of water were added, the mixture was shaken for 10 min, and the organic phase was separated, washed with a 5% solution of sodium carbonate and water, and dried over anhydrous sodium sulfate. The solvent was distilled off under reduced pressure, and the brown precipitate was washed with several portions of hexane. Yield 0.81 g (70%), mp 159–162°C. H NMR spectrum, δ, ppm: 10.12 s (1H, NH), 9.11 s (1H, OH), 8.28–8.04 d.d (4H, O2NC6H4, J = 8.9 Hz), 7.24 d (2H, 2-H, 6-H, J = 8.7 Hz), 6.74 d (2H, 3-H, 5-H, J = 8.7 Hz). Found, %: C 53.38; H 4.76; Cl 12.06; N 14.35. C13H10ClN3O3. Calculated, %: C 53.42; H 4.79; Cl 12.12; N 14.38. The H NMR spectra were recorded on a Varian Gemini 2000 spectrometer (400 MHz). The purity of compounds I and II was checked by TLC on Kieselgel 60 F254 plates (Merck) using chloroform–acetone (9 : 1) as eluent.

Modeling of phase equilibria with CPA using the homomorph approach

For association models, like CPA and SAFT, a classical approach is often used for estimating pure-compound and mixture parameters. According to this approach, the pure-compound parameters are estimated from vapor pressure and liquid density data. Then, the binary interaction parameters, kij, are estimated from binary systems; one binary interaction parameter per system. No additional mixing rules are needed for cross-associating systems, but combining rules are required, e.g. the Elliott rule or the so-called CR-1 rule. There is a very large class of mixtures, e.g. water or glycols with aromatic hydrocarbons, chloroform–acetone, esters–water, CO2–water, etc., which are classified as “solvating” or “induced associating”. The classical approach cannot be used and the cross-association interactions are difficult to be estimated a priori since usually no appropriate experimental data exist, while the aforementioned combining rules cannot capture the physical meaning of such interactions (as at least one of the compounds is non-self-associating). Consequently, very often one or more of the interaction parameters are optimized to experimental mixture data. For example, in the case of the CPA EoS, two interaction parameters are often used for solvating systems; one for the physical part (kij) and one for the association part (βcross). This limits the predictive capabilities and possibilities of generalization of the model. In this work we present an approach to reduce the number of adjustable parameters in CPA for solvating systems. The so-called homomorph approach will be used, according to which the kij parameter can be obtained from a corresponding system (homomorph) which has similar physical interactions as the solvating system studied. This leaves only one adjustable parameter for solvating mixtures, the cross-association volume (βcross). It is shown that the homomorph approach can be used with success for mixtures of water and glycols with aromatic hydrocarbons as well as for mixtures of acid gases (CO2, H2S) with alcohols and water. The homomorph approach is less satisfactory for mixtures with fluorocarbons as well as for aqueous mixtures with ethers and esters. In these cases, CPA can correlate liquid–liquid equilibria for solvating systems using two adjustable parameters. The capabilities and limitations of the homomorph approach are discussed.

Stability‐indicating HPTLC method for quantitative estimation of silybin in bulk drug and pharmaceutical dosage form

In the present study a novel stability-indicating high-performance thin-layer chromatography (HPTLC) method for quantitative determination of silybin in bulk drug and nanoemulsion formulation has been developed and validated on silica using solvent chloroform-acetone-formic acid (9 : 2 : 1 v/v/v) (R(f )of silybin 0.46 +/- 0.05) in the absorbance mode at 296 nm. The method showed a good linear relationship (r(2) +/- 0.999) in the concentration range 25-1500 ng per spot. It was found to be linear, accurate, precise, specific, robust and stability-indicating and can be applied for quality control and standardization of several multi-component hepatoprotective formulations as well as for stability testing of different dosage forms. The method proposed was also used to investigate the kinetics of acidic and alkaline degradation processes by quantification of drug at different temperature to calculate the activation energy and half-life for silymarin degradation.

Potential metabolites of dimethoate produced by bacterial degradation

Microbial degradation of pesticide has been recognized as a potential solution for the disposal of pesticide. Two bacterial strains namely Bacillus licheniformis and Pseudomonas aeruginosa, which were isolated from water and fish intestine, respectively, were allowed to grow in mineral salt solution. The acetonitrile extracts of the bacterial cultures were subjected to thin layer chromatography using two different solvent systems: hexane–chloroform–methanol and cyclohexane–acetone–chloroform. The chromatogram revealed the presence of four metabolites of dimethoate with different Rf values, in the original P. aeruginosa strain using both hexane–chloroform–methanol and cyclohexane–acetone–chloroform solvent systems. Total disappearance of dimethoate spot occurred in the culture of B. licheniformis strain at day 3. Thus, the present study establishes the bacterial degradation of dimethoate and also suggests the role of bacteria in the bioremediation of pesticides.

Calorimetric determination of the enthalpy of specific interaction of chloroform with a number of proton-acceptor compounds

Calorimetry was used to measure the enthalpies of solution of chloroform in various proton-acceptor solvents and, vice versa, proton-acceptors in chloroform. Based on a previously proposed equation, the enthalpies of specific interaction were calculated and compared with the published data on the enthalpy of hydrogen bonding of chloroform with various proton-acceptor solvents. The composition of the H-bonded complexes mainly formed during the dissolution of proton-acceptor solutes in chloroform was established. It was demonstrated that the dissolution of ethers in chloroform is predominantly accompanied by the formation of 1: 1 complexes, while the dissolution of acetone, dimethylformamide, and dimethyl sulfoxide in chloroform gives rise to more complex associates.

Influence of the Mobile and Stationary Phases on the Separation of Selected Essential Oil Components and Aroma Substances Investigated by TLC

Fifteen selected essential oil components and aroma substances were investigated using adsorption thin‐layer chromatography on silica gel 60 (E. Merck, #1.05744) and aluminum oxide (E. Merck, #1.05550) plates and the mobile phases benzene–chloroform, benzene–acetone, carbon tetrachloride–acetone, chloroform–acetone, and chlorobenzene–acetone in different volume compositions. The separations were evaluated on the basis of retention parameter RF and separation parameters values ΔRF, α, and RF α. None of the applied chromatographic conditions allowed for the complete separation of all the compounds examined. Aluminium oxide plates and carbon tetrachloride–acetone in volume composition 98:2 were optimal for the separation of the investigated alcohols: (+) borneol (B), geraniol (GR), menthol (M), and linalool (L). Aluminium oxide and carbon tetrachloride–acetone mobile phases in a volume composition of 85:15 were optimal for the separation of the investigated phenols: vanillin (V), guaiacol (G), eugenol (E), and thymol (T). Aluminium oxide and a chlorobenzene–acetone mobile phase in a volume composition of 95:5 was optimal for the separation of coumarin (C), cineole (CL), (R)‐(−) carvone (CR), cinnamic aldehyde (CA), camphor (CP), (1R)‐(−) fenchone (F), and trans anethole (A).

Adsorption of N 2, Ar, acetone, chloroform and acetone–chloroform mixture on carbon black in the framework of molecular layer structure theory (MLST)

Adsorption of pure nitrogen, argon, acetone, chloroform and acetone–chloroform mixture on graphitized thermal carbon black is considered at sub-critical conditions by means of molecular layer structure theory (MLST). In the present version of the MLST an adsorbed fluid is considered as a sequence of 2D molecular layers, whose Helmholtz free energies are obtained directly from the analysis of experimental adsorption isotherm of pure components. The interaction of the nearest layers is accounted for in the framework of mean field approximation. This approach allows quantitative correlating of experimental nitrogen and argon adsorption isotherm both in the monolayer region and in the range of multi-layer coverage up to 10 molecular layers. In the case of acetone and chloroform the approach also leads to excellent quantitative correlation of adsorption isotherms, while molecular approaches such as the non-local density functional theory (NLDFT) fail to describe those isotherms. We extend our new method to calculate the Helmholtz free energy of an adsorbed mixture using a simple mixing rule, and this allows us to predict mixture adsorption isotherms from pure component adsorption isotherms. The approach, which accounts for the difference in composition in different molecular layers, is tested against the experimental data of acetone–chloroform mixture (non-ideal mixture) adsorption on graphitized thermal carbon black at 50 °C.

Influence of the dilute‐solution properties of cellulose acetate in solvent mixtures on the morphology and pervaporation performance of their membranes

AbstractThe pervaporation performance of cellulose acetate (CA) membranes prepared from acetone (AC), acetone/tetrahydrofuran (AC/THF), acetone/chloroform (AC/CF), and acetone/cyclohexane (AC/CYH) was studied for separating MeOH/MTBE (methyl tert‐butyl ether) mixture with 5 (wt) % MeOH. The dilute‐solution properties and Huggins constant (KH) of CA dissolved in AC and AC/solvent mixtures with 15 vol % of the second solvent (tetrahydrofuran, chloroform, or cyclohexane) were examined. J and α of the CA membranes were affected by the types of solvent mixtures used to prepare the casting solutions. Under the same conditions, the membrane with AC/CYH had the highest J value and the lowest α value, and it was followed by the membranes with AC/CF, AC/THF, and AC. The increasing value of J and decreasing value of α for the CA membranes from different solvent mixtures were in good agreement with the increasing value of KH of CA in corresponding solvent mixtures. Furthermore, differences in the morphology from scanning electron microscopy images of the cross sections or from atomic force microscopy photographs of the surfaces of the membranes existed, and they provided proof of the different pervaporation performances of the CA membranes prepared from AC and AC/solvent mixtures. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 97:1891–1898, 2005

Application of stability-indicating HPTLC method for quantitative determination of metadoxine in pharmaceutical dosage form

A sensitive, selective, precise and stability-indicating high-performance thin-layer chromatographic method for analysis of metadoxine both as a bulk drug and in formulations was developed and validated. The method employed TLC aluminium plates precoated with silica gel 60F-254 as the stationary phase. The solvent system consisted of acetone–chloroform–methanol–ammonia (7.0: 4.0: 3.0: 1.2, v/v/v/v). Densitometric analysis of metadoxine was carried out in the absorbance mode at 315 nm. This system was found to give compact spots for metadoxine ( R f value of 0.45 ± 0.02, for six replicates). Metadoxine was subjected to acid, alkali and neutral hydrolysis, oxidation, dry and wet heat treatment and photo and UV degradation. The drug undergoes degradation under all stress conditions. Also, the degraded products were well resolved from the pure drug with significantly different R f values. The method was validated for linearity, precision, robustness, LOD, LOQ, specificity and accuracy. Linearity was found to be in the range of 100–1500 ng/spot with significantly high value of correlation coefficient r 2 = 0.9997 ± 1.02. The linear regression analysis data for the calibration plots showed good linear relationship with r 2 = 0.9999 ± 0.58 in the working concentration range of 200–700 ng/spot. The mean value of slope and intercept were 0.11 ± 0.04 and 18.73 ± 1.89, respectively. The limits of detection and quantitation were 50 and 100 ng/spot, respectively. Statistical analysis proves that the method is repeatable and specific for the estimation of the said drug. As the method could effectively separate the drug from its degradation products, it can be employed as a stability-indicating one. Moreover, the proposed HPTLC method was utilized to investigate the kinetics of acid and base degradation process. Arrhenius plot was constructed and activation energy was calculated respectively for acid and base degradation process.

A Rapid Cleanup Method for the Isolation and Concentration of Pyrrolizidine Alkaloids in Comfrey Root

Preparations from comfrey (Symphytum officinale and S. x uplandicum) root and leaf contain varying levels of the hepatotoxic pyrrolizidine alkaloids (PAs). Reference compounds for comfrey are not commercially available, and there is currently no rapid extraction or analytical method capable of determining low levels in raw materials or as adulterants in commercially available extracts. A solid-phase extraction (SPE) method was developed using an Ergosil cleanup column that specifically binds the PAs. With this method, powdered comfrey root was extracted by sonication and shaking with basic chloroform. The extract was applied to the cleanup column under vacuum, washed with 2 mL acetone-chloroform (8 + 2, v/v) followed by 2 mL petroleum ether to remove excess chloroform. The column was dried under vacuum, and the PAs were eluted with 2 successive 1 mL aliquots methanol. Percent recoveries of the PAs following Ergosil SPE had an overall average of 96.8%, with RSD of 3.8% over a range of 1.0 to 25.0 g extracted in 100 mL. Average precision of the method (n = 3 over 4 extraction concentrations) gave an overall RSD of 6.0% for the 5 alkaloids, with a range of 0.8% (5 g in 100 mL) to 11.2% (25 g in 100 mL). Recovery optimization testing showed that 1.0 g comfrey root extracted in 100 mL yielded the greatest recovery (% dry weight) of the PAs, with an extraction efficiency and accuracy of 94.2%, and RSD of 1.7% (n = 9). The unique properties of the Ergosil cleanup column provide rapid sample cleanup, volume reduction, and concentration of PAs from comfrey extracts, and allow the eluant to be analyzed directly by traditional chromatographic methods.

A novel high pressure tool: the solvation pressure of liquids

Co-solvents were studied to determine if the change in the cohesive energy density (CED)generates an effective solvation pressure equivalent to the application of an externalhydrostatic pressure. Raman modes of chloroform under hydrostatic pressure withco-solvents (chloroform–ethanol, chloroform–acetone) and in the vapour phase wererecorded. In some cases the Raman frequency shifts indicate that the solvation pressurebehaves as a true hydrostatic pressure. The pressure-induced gelation of starch grains wasstudied in aqueous media. A higher co-solvent concentration is postulated to put the grainsunder effective negative pressure, and indeed an increase in the external pressure needed forgelation was seen after the introduction of solvents. The quantitative agreement betweenthe change of solvation pressure and hydrostatic pressure is very good over a wide range ofsolvent concentration.

Enhancing reactivity of carbonyl compounds via hydrogen-bond formation. A DFT study of the hetero-Diels-Alder reaction between butadiene derivative and acetone in chloroform.

To examine how hydrogen-bond (HB) formation involving chloroform solvent molecules influences the chemical reactivity of ketones, the hetero-Diels-Alder reaction of N,N-dimethyl-1-amino-3-methoxy-1,3-butadiene and acetone has been studied by using density functional theory (DFT) at the B3LYP/6-31G level. The effects of the chloroform on the activation energies have been modeled by means of discrete-continuum models. In the gas phase, the formation of specific HB between acetone and one and two chloroform molecules decreases the activation barriers from 19.3 to 13.6 and 8.5 kcal/mol, respectively. Inclusion of solvent effects by means of combined discrete and polarizable continuum models yields a change of molecular mechanism from a concerted to a two-step mechanism, and the first nucleophilic step is the rate-limiting step. The corresponding values of activation barriers in chloroform are 18.6 kcal/ mol (no HB), 13.5 kcal/mol (one HB), and 9.6 kcal/mol (two HBs). These theoretical results account for the experimental observation that chloroform accelerates the reaction more markedly than more polar aprotic solvent such as acetonitrile. A DFT analysis of the global electrophilicity power of the reagents provides a sound explanation about the catalytic effects of chloroform.

Stability indicating HPTLC determination of clopidogrel bisulphate as bulk drug and in pharmaceutical dosage form

A sensitive, selective, precise and stability indicating high-performance thin layer chromatographic method of analysis of clopidogrel bisulphate both as a bulk drug and in formulations was developed and validated in pharmaceutical dosage form. The method employed TLC aluminium plates precoated with silica gel 60F-254 as the stationary phase. The solvent system consisted of carbon tetrachloride–chloroform–acetone (6:4:0.15, v/v/v). This system was found to give compact spots for clopidogrel bisulphate (R f value of 0.30±0.01). Clopidogrel bisulphate was subjected to acid and alkali hydrolysis, oxidation, photodegradation and dry heat treatment. Also the degraded products were well separated from the pure drug. Densitometric analysis of clopidogrel bisulphate was carried out in the absorbance mode at 230 nm. The linear regression data for the calibration plots showed good linear relationship with r 2=0.999±0.001 in the concentration range of 200–1000 ng. The mean value of correlation coefficient, slope and intercept were 0.999±0.001, 0.093±0.011 and 8.83±0.99, respectively. The method was validated for precision, accuracy, ruggedness and recovery. The limits of detection and quantitation were 40 and 120 ng per spot, respectively. The drug undergoes degradation under acidic and basic conditions, oxidation and dry heat treatment. All the peaks of degraded product were resolved from the standard drug with significantly different R f values. This indicates that the drug is susceptible to acid–base hydrolysis, oxidation and dry heat degradation. Statistical analysis proves that the method is reproducible and selective for the estimation of the said drug. As the method could effectively separate the drug from its degradation products, it can be employed as a stability indicating one.

Quantitative determination of diazepam, nitrazepam and flunitrazepam in tablets using thin-layer chromatography–densitometry technique

A simple and reliable assay for diazepam, nitrazepam and flunitrazepam in tablets by high-performance liquid chromatography (HPLC) and thin-layer chromatography (TLC)–densitometry is described. A quantity of a ground tablet mass, equal to the average weight of one tablet was sonicated in MeOH, mixed with appropriate internal standard, filtered and either injected directly into the liquid chromatograph, or after evaporation and reconstitution of an aliquot of the extract, was spotted on a silica gel thin-layer plate. A variable UV detector, operated at 254 nm was employed in both procedures. A C18, reversed phase 7 μm column was used for HPLC analysis; the mobile phase was a 1:1 (v/v) mixture of MeOH (40 °C) and 0.01 M phosphate buffer (pH 7, 80 °C). The TLC plate was developed in an unsaturated chromatographic chamber containing 100 ml chloroform–acetone (9:1); at room temperature, the mobile phase was allowed to travel 15 cm. The percentage of the active ingredient content of each tablet obtained by both procedures, was in the range of the stated amount except for one brand of diazepam tablets which contained ∼23% less active ingredient than the minimum prescribed amount. The TLC densitometry, although yields slightly higher values than the HPLC method, is preferred due to its simplicity, ease and low cost.

The Properties of Polymer-Containing BeO Dispersions in an Acetone–Chloroform Binary Medium

The properties of Newtonian and concentrated (non-Newtonian) BeO dispersions in solutions of acidic poly(vinyl acetate-co-vinyl chloride) in binary mixtures of chloroform (a Lewis acid) and acetone (a Lewis base) of different compositions were studied. In contrast to systems characterized by strong acid–base interactions at the particle–medium interface, the role of the steric stabilization factor was found to be extremely low in the studied dispersions. Polymer-containing BeO dispersions in acetone had the highest kinetic stability due to the specific interactions of this solvent with BeO particles and polymer macromolecules contributing to the redispersion of particles and the formation of protective solvation shells. The obtained data on the effect of the dispersion medium composition on the rheological properties of concentrated BeO dispersions can be used for the selection of optimal regimes for preparation of pastes for high-temperature ceramics.

Evaluation of Allergic Potential of Rubber Products: Comparison of Sample Preparation Methods for the Testing of Polymeric Medical Devices

A round-robin study was organized in the international standardization working group, ISO/TC194/WG8, with the purpose to compare the efficacy of different sample preparation procedures for determining the sensitization potency of polymeric medical devices. Three custom-made rubber samples were supplied to the participating laboratories and tested according to predetermined extraction and test protocols: A, formulated with a high level of mercaptobenzothiazole (MBT); B, formulated with a low level of MBT; and C, formulated with zinc dibutyldithiocarbamate. Extraction protocols included the so-called ISO method that applies physiological saline and/or vegetable oil extraction media without concentration (designated here “simple extraction”) and the so-called Japanese method that applies organic solvent extract (in this study chloroform–acetone mixture) after concentration to the test systems (designated here “exhaustive extraction”). Tests included human patch test, guinea pig maximization test (GPMT), adju...

Mass transfer resistance in liquid–liquid extraction with individual phase mixing

The paper deals with mass transfer in liquid–liquid extraction in both directions using the following ternary systems, water–acetone–chloroform and water–acetone–toluene. The experiments were performed in an improved Lewis cell operating in continuous mode, made out of two baffled compartments equipped with separate driven agitators. Each compartment contains a stirred or non-stirred phase. The transfer of the solute can be carried in the two directions through an interface of constant area, created between the two phases. The specific resistances on mass transfer were determined in the stirred or non-stirred phases, with the influence of the partition coefficient and transfer direction on these resistances being also evidenced.

Stability of Sulfonamides, Nitrofurans, and Chloramphenicol Residues in Preserved Raw Milk Samples Measured by Liquid Chromatography

A stability study was made of 10 antimicrobials: 6 sulfonamides, 3 nitrofurans, and chloramphenicol residues in raw milk samples preserved with 0.1 % potassium dichromate (K2Cr2O7) and 0.05% mercuric bichloride (HgCl2) during cold storage for 7 days. Preserved milk samples fortified with 50 ppb of each antimicrobial were analyzed by liquid chromatography (modified AOAC Method 993.32). Drugs were extracted with chloroform-acetone after solvent evaporation residues were dissolved with aqueous sodium acetate buffer solution (0.02M, pH 4.8), and fat was removed with hexane. Sulfonamides and chloramphenicol were detected at 275 nm (UV) by using a gradient system of sodium acetate buffer solution-acetonitrile starting at 95 + 5 (v/v) and finishing at 80 + 20 (v/v). Nitrofurans were detected at 375 nm (UV) isocratically with sodium acetate buffer solution-acetonitrile (80 + 20, v/v). Residues stability was measured through recovery data. Sulfamethoxazole, sulfachloropyridazine, nitrofurazone, furazolidone, and furaltadone residues remained stable in the presence of either preservative for 7 days. Sulfamethazine and chloramphenicol were not affected by K2Cr2O7, but had significant losses (p <0.05) when HgCl2 was used: 26.2 and 13.4%, respectively. Average recoveries of sulfamonomethoxine, sulfamerazine, and sulfathiazole significantly decreased by Day 7, with losses of 17.1, 17.2, and 23.2% for K2Cr2O7, and 23.3, 20.7, and 48.0% for HgCl2, respectively. During 5 days of cold storage all antimicrobials tested, except sulfathiazole, remained stable in milk samples preserved with 0.1 % K2Cr2O7 or 0.05% HgCl2.

Development of polylactide microspheres for protein encapsulation and delivery

AbstractThe development of injectable microparticles for protein delivery is a major challenge. We demonstrated the possibility of entrapping human serum albumin (HSA) and thrombin (Thr) in poly(ethylene glycol) (PEG)‐coated, monodisperse, biodegradable microspheres with a mean diameter of about 10 μm. In our earlier studies, diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS) analysis was used to characterize the surface of PEG‐coated, taxol‐loaded poly(lactic acid) (PLA) microspheres. An analysis by DRIFTS revealed that PEG was incorporated well on the PLA microsphere surface. An emulsion of protein (in water) and PLA dissolved in an acetone–dichloromethane (or acetone–chloroform) mixture were poured into an aqueous solution of PEG [or poly(vinyl alcohol) (PVA)] with stirring with a high‐speed homogenizer for the formation of microparticles. HSA recovery in microspheres ranged from 13 to 40%, depending on the solvent and emulsification systems used for the preparation. PLA dissolved in a dichloromethane/acetone system and albumin loaded via a PEG emulsification solution (PLA–PEG–HSA) showed maximum drug recovery (39.5%) and drug content (9.9%). Scanning electron microscopy revealed that PEG‐coated microspheres had less surface micropores than PVA‐based preparations. The drug‐release behavior of microspheres suspended in phosphate‐buffered saline exhibited a biphasic pattern. An initial burst release (30%) followed by a constant slow release for 20 days was observed for HSA and Thr from PLA–PEG microspheres. PEG‐coated PLA microspheres show great potential for protein‐based drug delivery. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 86: 1285–1295, 2002

Liquid Chromatographic Determination of Multiple Sulfonamides, Nitrofurans, and Chloramphenicol Residues in Pasteurized Milk

A rapid and selective liquid chromatographic method was developed to detect 6 sulfonamides, 3 nitrofurans, and chloramphenicol residues in pasteurized milk. The 10 drugs were extracted with chloroform-acetone and the organic phase was evaporated; the residues were dissolved in an aqueous sodium acetate buffer solution 0.02M (pH = 4.8), and the fat was removed by washing with hexane. The aqueous layer was collected, filtered, and injected. The 6 sulfonamides and chloramphenicol were detected at 275 nm ultraviolet (UV) using a gradient system starting with sodium acetate buffer solution-acetonitrile (95 + 5) and finishing with sodium acetate buffer solution-acetonitrile (80 + 20). Nitrofurans were detected at 375 nm (UV) isocratically with sodium acetate buffer solution-acetonitrile (80 + 20). For 50 ppb fortified milk, the average recoveries were (sulfathiazole) 65.52%; (sulfamerazine) 75.36%; (sulfamethazine) 93.94%; (sulfachlorpyridazine) 75.94%; (sulfamethoxazole) 85.18%; (sulfamonomethoxine) 83.45%; (chloramphenicol) 104.17%; (nitrofurazone) 91.81%; (furazolidone) 100.76%; and (furaltadone) 72.38%. Method detection limits ranged from 4 ppb (nitrofurazone) to 16 ppb (sulfamethazine). Some matrix interferences (3-7 ppb) were observed only with sulfonamides.