dispersive liquid–liquid microextraction combined with gas chromatography for extraction and...
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J. Sep. Sci. 2012, 35, 10271035 1027
Mir Ali Farajzadeh1Leila Goushjuii1Djavanshir Djozan1Javad Kompani Mohammadi2
1Department of AnalyticalChemistry, Faculty of Chemistry,University of Tabriz, Tabriz, Iran
221st Street, Kaveh IndustrialCity, Mahban PharmaceuticalCompany, Tehran, Iran
Received October 25, 2011Revised January 10, 2012Accepted January 10, 2012
Dispersive liquidliquid microextractioncombined with gas chromatography forextraction and determination of class 1residual solvents in pharmaceuticalsThe present study reports a new method for analyzing class 1 residual solvents (RSs), 1,1-dichloroethene (1,1-DCE), 1,2-dichloroethane (1,2-DCE), 1,1,1-trichloroethane (1,1,1-TCE),carbon tetrachloride (CT), and benzene (Bz), in pharmaceutical products using dispersiveliquidliquid microextraction (DLLME) combined with gas chromatographyflame ioniza-tion detection (GC-FID). Unlike common DLLME methods, solvents of high boiling pointwere selected as dispersive and extraction solvents in order to prevent their chromato-graphic peaks from overlapping with those of analytes that have short retention times.Therefore N,N-dimethyl formamide (DMF) and 1,2-dibromoethane (1,2-DBE) were chosenas dispersive and extraction solvents, respectively. Analytical parameters of the proposedmethod were determined and good linearities and broad linear ranges (LRs) were ob-tained. Taking 500 mg samples, limit of detections for the tested pharmaceuticals wereobtained as 0.11, 0.03, 0.05, 0.05, and 0.006 g g1 for CT, 1,1-DCE, 1,2-DCE, 1,1,1-TCE,and Bz, respectively, which are considerably much lower than their permissible limits inpharmaceuticals.
Keywords: Class 1 residual solvents / Dispersive liquidliquid microextraction /Gas chromatography / PharmaceuticalsDOI 10.1002/jssc.201100917
Residual solvents (RSs) are defined as volatile organic com-pounds (VOCs) that are used in or produced during the man-ufacturing process of drug substances, or in the preparationof drug products. These solvents are not completely removedby practical manufacturing techniques such as freezedryingand drying at high temperature under vacuum. The presenceof these unwanted chemicals even in small amounts, notonly may influence the efficacy and safety of drug (regardingboth human health and environmental issues), but also theirchemical identity and amountmay affect some physicochem-ical properties of drug products such as: their particle size,
Correspondence: Dr. Mir Ali Farajzadeh, Department of AnalyticalChemistry, Faculty of Chemistry, University of Tabriz, Tabriz, IranE-mail: firstname.lastname@example.org and email@example.comFax: +98-411-3340191
Abbreviations: Bz, benzene; CT, carbon tetrachloride; 1,2-DBE, 1,2-dibromoethane; 1,1-DCE, 1,1-dichloroethene; 1,2-DCE, 1,2-dichloroethane; DLLME, dispersive liquidliquidmicroextraction; DMF, N,N-dimethyl formamide; EF, en-richment factor; ERs, extraction recoveries; GC-FID, gaschromatography-flame ionization detection; LR, linear range;RSs, residual solvents; 1,1,1-TCE, 1,1,1-trichloroethane;VOCs, volatile organic compounds
crystalline structure , wettability [2, 3], stability, and disso-lution properties . Moreover, RSs may play a key role inthe modification of product odor as well . This implies thatquality control of pharmaceutical products should include ob-taining accurate information on identity and quantity of anyRS present.
Guideline Q3C  was adopted by the International Con-ference on Harmonization (ICH) of Technical Requirementsfor Registration of Pharmaceuticals for Human Use on 17July 1997 and it has been accepted by the European Phar-macopoeia (5th Ed.), Japanese Pharmacopoeia (14th Ed.),the United States Pharmacopoeia (28th Ed.), and the Chi-nese Pharmacopoeia 2005. It classified RSs into three cate-gories according to their potential toxicity and limited theiramount in pharmaceuticals. Class 1 includes solvents con-sidered to be the most toxic, such that their use should beavoided in the production of pharmaceutical products. Thesechemicals are: benzene (Bz), carbon tetrachloride (CT), 1,2-dichloroethane (1,2-DCE), 1,1-dichloroethene (1,1-DCE), and1,1,1-trichloroethane (1,1,1-TCE) (the latter owing to its ad-verse environmental impact). However, if their use is un-avoidable, their level should be restricted to the amounts givenin Table 1 . Class 2 and class 3 RSs are considered to be oflesser hazard. A list of other RSs that may attract a growinginterest could someday be called class 4 RSs.
As mentioned above, the RSs are VOCs; thereforethey can be separated and determined qualitatively and
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1028 M. A. Farajzadeh et al. J. Sep. Sci. 2012, 35, 10271035
Table 1. Class 1 residual solvents (RSs), related applied symbolsin this article, ICH recommended concentration and im-pact of their toxicity
Compound ICH recommended Concernconcentration (ppm)
1500 Toxic andenvironmental hazard
Benzene (Bz) 2 Toxic1,2-Dichloroethane
(1,2-DCE)5 Environmental hazard
quantitatively by gas chromatography (GC). So, direct injec-tion to GC system has commonly used for achieving thispurpose . Furthermore, use of dynamic headspace sys-tem, i.e. purge and trap [3, 8], and programmed tempera-ture vaporizer inlet to inject the samples into the chromato-graphic column  are previously devised and appliedmethods. However it should be considered that complex ma-trix of pharmaceutical samples and low concentrations ofanalytes (their prescribed limits are at ppm levels), make itnecessary to introduce an isolation and/or preconcentrationstep in the analytical procedure. Solid-phase microextraction(SPME) coupled with GC has been established and appliedto determine RSs in drugs being soluble in water .Headspace-solid phase microextraction (HS-SPME) has also been used in this field. A headspace-liquid phase mi-croextraction (HS-LPME) combinedwithGCwas proposed byWang et al. in 2006 for extraction anddetermination of volatilesolvent residues in pharmaceutical products . Recently anew method was developed by combining the single-dropmicroextraction (SDME) and multiple headspace extractionfollowed by capillary GC-FID for quantitative determinationof volatile RSs in solid drug .
The above-mentioned methods, despite their applicabil-ity, have some defects. Direct injection method is simple butits main disadvantage is that non-volatile components arealso injected into the system which leads to injector con-tamination, column contamination, and deterioration withunavoidable matrix effects [16,20]. Headspace injection is analternative technique, but it is rather limited in terms of opti-mization possibilities with respect to its selectivity . SPMEalso suffers from some disadvantages. That uses expensivematerials, is time-consuming, and usually has carryover ef-fects .
A few years ago, a new liquidliquid microextrac-tion method named dispersive liquidliquid microextraction(DLLME) was introduced by Assadi and co-workers  asan extraction and preconcentration method which has manybenefits and eliminates most disadvantages of the traditionalsample preparation techniques. Owing to the outstandingmerits of DLLME including simplicity, low cost, rapidity and
high enrichment factor (EF), this technique was widely ac-cepted and has been successfully applied in the preconcen-tration of different target compounds in aqueous samples.
In the present work, we developed this strategy and com-bined itwithGC-FID for the extraction, preconcentration, anddetermination of toxic ICH class 1 solvents in pharmaceuticalproducts. By now, DLLME was not used in determination ofvolatile compounds such as solvents, and all reported worksare based on extraction and dispersive solvents of low boil-ing point. In this work, common dispersive solvents such asacetone, methanol, and acetonitrile and common extractionsolvents such as CT, chloroform, etc. cannot be used. Chro-matographic peaks of the target analytes (volatile solvents) areoverlapping with those of solvents used in DLLME. For thefirst time, dispersive and extraction solvents (e.g. DMF and1,2-DBE, respectively) of boiling point higher than that ofanalytes were used in DLLME that decrease or eliminate sep-aration problems in GC. The proposed method is rapid andsimple, uses mg levels of sample and L levels of extractionand dispersive solvents and has low LODs.
2.1 Chemicals and samples
The solvents used were purchased from the followingsources: CT, 1,2-DCE, 1,2-DBE, 1,1,1-TCE, N,N-dimethylformamide (DMF), dimethyl sulfoxide (DMSO), methanol,acetone, acetonitrile, 1,1-DCE, and n-propanol were fromMerck (Darmstadt, Germany); and 1,2-bromochloroethane,1,1,2,2-tetrachloroethane, and 1,1,2,2-tetrabromoethane werefrom Janssen (Beerse, Belgium). Other chemicals such assodium chloride, hydrochloric acid, and sodium hydrox-ide were obtained from Merck. Deionized water (GhaziCompany, Tabriz, Iran) was used for preparation of aque-ous solutions. Erythromycin and clindamycin hydrochlo-ride were from Sepidaj Pharmaceutical Company (Tehran,Iran), cefepime was from Hetro (Hyderabad, India), amoxi-cillin trihydrate was from Farabi Company (Isfahan, Iran),ceftriaxone-Na was from Daana Pharmaceutical Company(Tabriz, Iran), and meglumine compound 76% (sodium di-atrizoate/meglumine diatrazoate, 10:66) was from DarouPakhsh Company (Tehran, Iran).
To optimize the preconcentration and chromatographic sep-aration, standard solution of analytes (class 1 RSs) was pre-pared in 1,2-DBE ormethanol with concentrations as