Chromatographic separation of racemic praziquantel and its residual determination in perch by LC-MS/MS.

An enantioselective depletion study of praziquantel (PZQ) in perch muscle was done using a simple, sensitive and specific liquid chromatography-tandem mass spectrometry (LC-MS/MS) method. Two cyclic polypeptides and two cyclic saccharide chromatographic columns were evaluated. The new hydroxypropyl ß-cyclodextrin (HP-RSP) superficially porous particle (SPP) column produced the optimum separation and was selected for the study. Deuterium labeled PZQ-d11 was used as the internal standard. The method was linear over concentration ranges of 5.00-5.00×102µgL-1 (r2≥0.99) for (-)-R-PZQ and (+)-S-PZQ. The average recoveries of R-PZQ and S-PZQ at three spiked levels of 5.00, 50.00 and 5.00×102µgkg-1 ranged from 86.1% to 98.2%, and the intra-day and inter-day relative standard deviations were less than 5%. The decision limit (CCα) and detection capability (CCß) of R-PZQ and S-PZQ in perch muscle matrices were all 1.0µgkg-1 and 5.0µgkg-1, respectively. The method was successfully applied in monitoring the depletion of praziquantel enantiomers in perch muscle following oral administration. The elimination rate of R-PZQ and S-PZQ in perch muscle tissue is equivalent.

Validated capillary electrophoretic method for the enantiomeric quality control of R-praziquantel.

The enantiomers of praziquantel, the drug of choice in schistosomiasis, were separated by electrokinetic chromatography with cyclodextrins. Nine anionic cyclodextrins were screened for their ability to discriminate between the uncharged enantiomers. Seven investigated selectors presented chiral interactions with the enantiomers, these cases being interpreted in terms of stability constants and complex mobilities. The best results were delivered by sulfated-ß-cyclodextrin, where quasi-equal stability constants were accompanied by extreme selectivity values and was explained on the basis of highly different mobilities of the transient diastereomeric complexes. Since the enantiomer migration order was unfavorable, a simple polarity switch was employed (detection end at anode), which apart from migration order reversal, also resulted in extreme resolution values (Rs > 35) and increased migration times. After optimization (50 mM phosphate buffer pH 2.0, supplied with 15 mM sulfated-ß-cyclodextrin, 15 kV, capillary temperature 25°C, short-end injection with 50 mbar × 2 s), analysis time under 10 min were obtained, while still maintaining high resolution (Rs > 10). The method was validated according to the ICH guidelines and application of the method was tested on in-house synthetized R-praziquantel batches and on commercial, combination tablets containing racemic mixture of the drug.

Nonlinear model predictive control applied to the separation of praziquantel in simulated moving bed chromatography.

An adaptive nonlinear model predictive control of a simulated moving bed unit for the enantioseparation of praziquantel is presented. A first principle model was applied at the proposed purity control scheme. The main concern about this kind of model in a control framework is in regard to the computational effort to solve it; however, a fast enough solution was achieved. In order to evaluate the controller's performance, several cases were simulated, including external pumps and switching valve malfunctions. The problem of plant-model mismatch was also investigated, and for that reason a parameter estimation step was introduced in the control strategy. In every studied scenario, the controller was able to maintain the purity levels at their set points, which were set to 99% and 98.6% for extract and raffinate, respectively. Additionally, fast responses and smooth actuation were achieved.

Resolution of praziquantel.

BACKGROUND: Praziquantel remains the drug of choice for the worldwide treatment and control of schistosomiasis. The drug is synthesized and administered as a racemate. Use of the pure active enantiomer would be desirable since the inactive enantiomer is associated with side effects and is responsible for the extremely bitter taste of the pill. METHODOLOGY/PRINCIPAL FINDINGS: We have identified two resolution approaches toward the production of praziquantel as a single enantiomer. One approach starts with commercially available praziquantel and involves a hydrolysis to an intermediate amine, which is resolved with a derivative of tartaric acid. This method was discovered through an open collaboration on the internet. The second method, identified by a contract research organisation, employs a different intermediate that may be resolved with tartaric acid itself. CONCLUSIONS/SIGNIFICANCE: Both resolution procedures identified show promise for the large-scale, economically viable production of praziquantel as a single enantiomer for a low price. Additionally, they may be employed by laboratories for the production of smaller amounts of enantiopure drug for research purposes that should be useful in, for example, elucidation of the drug's mechanism of action.

Treatment of praziquantel wastewater using the integrated process of coagulation and gas membrane absorption.

Praziquantel is an anti-schistosoma drug, its wastewater contains numerous cyanide and other colloid pollutant. A novel integrated treatment process was proposed in this study, i.e., using coagulation to eliminate colloid pollutant and using gas membrane absorption (GMA) to remove cyanide. The optimization of coagulation condition, determination of cyanide removal rate, elimination of membrane fouling, and overall evaluation of the integrated process for the treatment of praziquantel wastewater were investigated in this study. Good results were achieved: turbidity reduced from 700 NTU to 10-40 NTU, 92% COD was removed, cyanide concentration dropped from 3500 mg/L to below 0.5 mg/L, recovery rate of cyanide reached to 98%, and operation cost could be entirely compensated from the gain of recovered cyanide. The results demonstrate that the novel integrated process offers a number of advantages over alkaline chlorination method in the treatment of praziquantel wastewater: cyanide can be reused rather than destroyed, no secondary pollutants are produced, the operation cost is low and the equipment etching is avoided.

Enantioseparations by capillary electro-chromatography: differences exhibited by normal- and reversed-phase versions of polysaccharide stationary phases.

The influence of using normal-phase and reversed-phase versions of four commercial polysaccharide stationary phases on chiral separations was investigated with capillary electrochromatography (CEC). Both versions of the stationary phases, Chiralcel OD, OJ, and Chiralpak AD, AS were tested for the separation of two basic, two acidic, a bifunctional, and a neutral compound. Different background electrolytes were used, two at low pH for the acid, bifunctional and neutral substances, and three at high pH for the basic, bifunctional and neutral ones. This setup allowed evaluating differences between both stationary-phase versions and between mobile-phase compositions on a chiral separation. Duplicate CEC columns of each stationary phase were in-house prepared and tested, giving information about the intercolumn reproducibility. In general, reversed-phase versions of the current commercial polysaccharide stationary phases are found to be best for reversed-phase CEC, even though at high pH no significant differences were seen between both versions. Most differences were observed at low pH. For acidic compounds, it was seen that an ammonium formate electrolyte performed best, which is also an excellent electrolyte if coupling with mass spectrometry is desired. For basic, bifunctional and neutral compounds, no significant differences between the three tested electrolytes were observed at high pH. Here, a phosphate buffer is preferred as electrolyte because of its buffering capacities. However, if coupling to mass spectrometry is wanted, the more volatile ammonium bicarbonate electrolyte can be used as an alternative.

Separation of enantiomers by nanoliquid chromatography and capillary electrochromatography using a bonded cellulose trisphenylcarbamate stationary phase.

A cellulose trisphenylcarbamate-bonded chiral stationary phase was applied to nano-liquid chromatography (nano-LC) and capillary electrochromatography (CEC) with nonaqueous and aqueous solutions as the mobile phases. Several chiral compounds were successfully resolved on the prepared phase by nano-LC. The applicability of nonaqueous CEC on a cellulose derivative stationary phase was investigated with the organic solvents methanol, hexane, 2-propanol, and tetrahydrofuran (THF) containing acetic acid, as well as triethylamine as the mobile phases. Enantiomers of warfarin and praziquantel were baseline-resolved with plate numbers of 82,300 and 38,800 plates/m, respectively, for the first eluting enantiomer. The influence of applied voltage, concentration of nonpolar solvent, apparent pH, and buffer concentration in the mobile phase on the electroosmotic flow (EOF) and the mobility of the enantiomers was evaluated. Enantioseparations of trans-stilbene oxide and praziquantel were also achieved in aqueous CEC with plate numbers of 111,100 and 107,400 plates/m, respectively, for the first eluting enantiomer. A comparison between nonaqueous CEC and aqueous CEC based on a cellulose trisphenylcarbamate stationary phase was discussed. Pressure-assisted CEC was examined for the chiral separation of praziquantel and faster analysis with high enantioselectivity was acquired with the proper pressurization of the inlet vial.

Enantiomer separation by strong anion-exchange capillary electrochromatography with dynamically modified sulfated beta-cyclodextrin.

A novel mode of capillary electrochromatography (CEC) based on a dynamically modified stationary phase was presented for chiral separation. The capillary column was packed with strong anion-exchange (SAX) stationary phase packing; the sulfated beta-cyclodextrin (S-CD), which was added to the mobile phase, was dynamically adsorbed to the packing surface. Separation of enantiomers was achieved by their different abilities to form an inclusion complex with the adsorbed S-CD. The enantiomers of tryptophan, praziquantel, atropine, metoprolol, and verapamil were successfully separated in this system with a column efficiency of 36000-412000 plates/m. The resolution value obtained for atropine was as high as 11.23. The superiority of CEC with a dynamically modified stationary phase over that with a physically adsorbed stationary phase was demonstrated. The influence of ionic strength, S-CD concentration, and methanol content on separation was also studied.

[The preparation of chiral column of cellulose triacetate coated on small pore silica gel and the separation of enantiomers].

The cellulose triacetate (CTA) prepared by heterogeneous acetylation and coated on small pore 3-aminopropyl silica gel (10 nm) was used as chiral stationary phase for HPLC (OA column). The racemes of three drugs, two fulvenes and one dazine, were separated on this column. Among these racemes, timolol maleas was separated using 1.0 mol/L NaClO4:95% ethanol = 10:90 as mobile phase. Without NaClO4 in mobile phase, the resolution of timolol maleas can not occur. Ethanols of 95%-98% were used as mobile phase for other racemes. The influence of the content of water in mobile phase on the chiral separation of praziquentelum, the retention time and separation factor (alpha) were reduced with the increase of water content in mobile phase. When the content of water in the mobile phase was 13%, praziquentelum could not be separated. It was found that in the case of samples No. 1 and No. 2, when the substituents R1 and R2 or R'1 and R'2 of fulvenes are 4-methoxybenzoyl and 4-methoxyphenyl, the chiral separations of fulvenes can be obtained. For sample No. 4 when R1 and R2 of fulvenes are 2-methylbenzoyl and 2-methylphenyl or in the case of No. 5, when R1 and R2 are 5-bromo-2-furoyl and 5-bromo-2-furan, the chiral separations of fulvenes can not be achieved. For sample No. 6 and No. 7, when R'1 are 4-chlorobenzoyl and benzoyl or R'2 are 4-chlorophenyl and phenyl, the chiral separation also can not be achieved. The column performance and separation factor were not obviously reduced after used for four months.