Application of On-Line Sorbentless Cryogenic Needle Trap Extraction Coupled with GC-FID for Analysis of Some Organic Volatile Impurities in Solid Pharmaceuticals.

An automated sorbentless cryogenic needle trap device (ASCNTD) was developed for the extraction of organic volatile impurities (OVIs) from solid pharmaceuticals prior to their determination by gas chromatography (GC). In this method, a new set up was designed and used to extraction of several OVIs from ceftazidime, ceftriaxone sodium and amoxicillin. For this purpose, a proper amount of the sample was transferred into the extraction vessel. The sample headspace components were started to circulate through a needle with a flow rate of 20 mL min-1. The OVIs were trapped on the inner surface of a needle placed on top of the sample by flowing liquid nitrogen. After a predetermined time, the coiled nichrome resistance wire placed into the hollow ceramic rod was heated and the trapped analytes were desorbed and swept into the GC capillary column using the carrier gas. The effective parameters such as volume of the sample vial, headspace flow rate, extraction temperature and time, and desorption conditions have been investigated. Qualification studies reveal that pyridine (as a degradation product of ceftazidime), methylene chloride, diethylamine, triethylamine, isopropyl alcohol and n-butyl acetate are the main impurities in the studied pharmaceuticals. Detected OVIs were quantitated using external standard method. The obtained relative standard deviation values were <8%, and the limits of detection (LOD) for the detected OVIs were in the range of 1-34 ng g-1.

On-Line Sorbentless Cryogenic Needle Trap and GC-FID Method for the Extraction and Analysis of Trace Volatile Organic Compounds from Soil Samples.

In this study, an automated sorbentless cryogenic needle trap device (ASCNTD) coupled with a gas chromatograph (GC) was developed with the aim of sampling, pre-concentration and determination of volatile organic compounds (VOCs) from soil sample. This paper describes optimization of relevant parameters, performance evaluation and an illustrative application of ASCNTD. The ASCNTD system consists of a 5 cm stainless steel needle passed through a hollow ceramic rod which is coiled with resistive nichrome wire. The set is placed in a PVC (Polyvinyl chloride) chamber through which liquid nitrogen can flow. The headspace components are circulated with a pump to pass through the needle, and this results in freeze-trapping of the VOCs on the inner surface of the needle. When extraction is completed, the analytes trapped in the inner wall of the needle were thermally desorbed and swept by the carrier gas into the GC capillary column. The parameters being effective on the extraction processes, namely headspace flow rate, the temperature and time of extraction and desorption were optimized and evaluated. The developed technique was compared to the headspace solid-phase microextraction method for the analysis of soil samples containing BTEX (Benzene, Toluene, Ethylbenzene and Xylene). The relative standard deviation values are below 8% and detection limits as low as 1.2 ng g-1 were obtained for BTEX by ASCNTD.

Co-liquefaction with acetone and GC analysis of volatile compounds in exhaled breath as lung cancer biomarkers.

Introduction: A simple, rapid and low cost method for enrichment of volatile organic compounds (VOCs) from exhaled breath (EB) is presented. Methods: A 1000 mL home-made extraction device was filled with EB. The VOCs were extracted and condensed in 0.5 mL acetone. Recognition of volatiles in the real studied EB samples was performed by a GC-MS. Results: The method displays an extraction efficiency of >86% with the enrichment factor of 1929 for octanal. Limits of detection and quantification, and linear dynamic range were 0.008, 0.026 and 0.026-400 ng/mL respectively. Analysis of real samples showed the existence of more than 100 compounds in EB of healthy volunteers and patients with lung cancer before and after treatment. Exhaled octanal concentration was significantly higher in lung cancer patient than in healthy volunteers and lung cancer patient after treatment. Conclusion: Having used the proposed approach, high extraction recovery (up to 86%) was attained for the lung cancer marker, octanal, as an important biomarker. Our findings on smaples of EB of healthy controls and patients with lung cancer before and after treatment provide complelling evidence upon the effectiveness of the developed method.

Molecularly imprinted-solid phase extraction combined with simultaneous derivatization and dispersive liquid-liquid microextraction for selective extraction and preconcentration of methamphetamine and ecstasy from urine samples followed by gas chromatography.

In this study, a developed technique was reported for extraction and pre-concentration of methamphetamine (MAMP) and 3,4-methylenedioxymethamphetamine (MDMA, ecstasy) from urine samples using molecularly imprinted-solid phase extraction (MISPE) along with simultaneous derivatization and dispersive liquid-liquid microextraction (DLLME). Molecularly imprinted microspheres as sorbent in solid phase extraction (SPE) procedure were synthesized using precipitation polymerization with MAMP as the template. Aqueous solution of the target analytes was passed through MAMP-MIP cartridge and the adsorbed analytes were then eluted with methanol. The collected eluate was mixed with butylchloroformate which served as the derivatization reagent as well as the extraction solvent. The mixture was immediately injected into deionized water. After centrifugation, 1 µL of the settled organic phase was injected into gas chromatography-flame ionization detection (GC-FID) or gas chromatography-mass spectrometry (GC-MS). Various experimental parameters affecting the performance of both of the steps (MISPE and DLLME) were thoroughly investigated. The calibration graphs were linear in the ranges of 10-1500 ng mL(-1) (MAMP) and 50-1500 ng mL(-1) (MDMA), and the detection limits (LODs) were 2 and 18 ng mL(-1), respectively. The relative standard deviations (%RSDs) obtained for six repeated experiments (100 ng mL(-1) of each drug) were 5.1% and 6.8% for MAMP and MDMA, respectively. The relative recoveries obtained for the analytes in human urine samples, spiked with different levels of each drug, were within the range of 80-88%.

Dispersive liquid-liquid microextraction combined with gas chromatography for extraction and determination of class 1 residual solvents in pharmaceuticals.

The 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 dispersive liquid-liquid microextraction (DLLME) combined with gas chromatography-flame ionization detection (GC-FID). Unlike common DLLME methods, solvents of high boiling point were selected as dispersive and extraction solvents in order to prevent their chromatographic 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 chosen as dispersive and extraction solvents, respectively. Analytical parameters of the proposed method were determined and good linearities and broad linear ranges (LRs) were obtained. Taking 500 mg samples, limit of detections for the tested pharmaceuticals were obtained as 0.11, 0.03, 0.05, 0.05, and 0.006 µg g(-1) for CT, 1,1-DCE, 1,2-DCE, 1,1,1-TCE, and Bz, respectively, which are considerably much lower than their permissible limits in pharmaceuticals.

Determination of phthalate esters in cow milk samples using dispersive liquid-liquid microextraction coupled with gas chromatography followed by flame ionization and mass spectrometric detection.

A simple and economic method for the analysis of phthalate esters, dimethyl phthalate, diethyl phthalate, di-iso-butyl phthalate, di-n-butyl phthalate, and di-2-ethylhexyl phthalate in cow milk samples by means of gas chromatography-flame ionization detection and gas chromatography-mass spectrometry has been developed. In this work, NaCl and ACN were added to 5 mL of the milk sample as the salting out agent and extraction solvent, respectively. After manual shaking, the mixture was centrifuged. In the presence of NaCl, a two-phase system was formed: upper phase - acetonitrile containing phthalate esters -and lower phase - aqueous phase containing soluble compounds and the precipitated proteins. After the extraction of phthalate esters from milk, a portion of supernatant phase (acetonitrile) was removed, mixed with 1,2-dibromoethane at microliter level and injected by syringe into NaCl solution. After the extraction of the selected phthalate esters into 1,2-dibromoethane, phase separation was performed by centrifugation and the enriched analytes in the sedimented phase were determined by gas chromatography-flame ionization detection and gas chromatography-mass spectrometry. Under the optimum extraction conditions, low limits of detection and quantification between 1.5-3 and 2.5-11 ng/mL, respectively was observed. Enrichment factors were in the range of 397-499. The relative standard deviations for the extraction of 100 ng/mL of each phthalate ester were in the range of 3-4% (n = 6). Finally, some milk samples were successfully analyzed using the proposed method and two analytes, di-n-butyl phthalate and di-2-ethylhyxel phthalate, were determined in them in nanogram per milliliter level.

Development of a new dispersive liquid-liquid microextraction method in a narrow-bore tube for preconcentration of triazole pesticides from aqueous samples.

In the present work a new, simple, rapid and environmentally friendly dispersive liquid-liquid microextraction (DLLME) method has been developed for extraction/preconcentration of some triazole pesticides in aqueous samples and in grape juice. The extract was analyzed with gas chromatography-flame ionization detection (GC-FID) or gas chromatography-mass spectrometry (GC-MS). The DLLME method was performed in a narrow-bore tube containing aqueous sample. Acetonitrile and a mixture of n-hexanol and n-hexane (75:25, v/v) were used as disperser and extraction solvents, respectively. The effect of several factors that influence performance of the method, including the chemical nature and volume of the disperser and extraction solvents, number of extraction, pH and salt addition, were investigated and optimized. Figures of merit such as linearity (r(2)>0.995), enrichment factors (EFs) (263-380), limits of detection (0.3-5 µg L(-1)) and quantification (0.9-16.7 µg L(-1)), and relative standard deviations (3.2-5%) of the proposed method were satisfactory for determination of the model analytes. The method was successfully applied for determination of target pesticides in grape juice and good recoveries (74-99%) were achieved for spiked samples. As compared with the conventional DLLME, the proposed DLLME method showed higher EFs and less environmental hazards with no need for centrifuging.

Development of a new microextraction method based on a dynamic single drop in a narrow-bore tube: application in extraction and preconcentration of some organic pollutants in well water and grape juice samples.

A novel sample preparation technique, the microextraction method based on a dynamic single drop in a narrow-bore tube, coupled with gas chromatography-flame ionization detection (GC-FID) is presented in this paper. The most important features of this method are simplicity and high enrichment factors. In this method, a microdrop of an extraction solvent assisted by an air bubble was repeatedly passed through a narrow-bore closed end tube containing aqueous sample. It has been successfully used for the analysis of some pesticides as model analytes in aqueous samples. Parameters affecting the method's performance such as selection of extraction solvent type and volume, number of extractions, volume of aqueous sample (tube length), and salt effect were studied and optimized. Under the optimal conditions, the enrichment factors (EFs) for triazole pesticides were in the range of 141-214 and the limits of detection (LODs) were between 2 and 112 µg L(-1). The relative standard deviations (C=1000 µg L(-1), n=6) were obtained in the range of 2.9-4.5%. The recoveries obtained for the spiked well water and grape juice samples were between 71 and 106%. Low cost, relatively short sample preparation time and less solvent consumption are other advantages of the proposed method.

Extraction and preconcentration technique for triazole pesticides from cow milk using dispersive liquid-liquid microextraction followed by GC-FID and GC-MS determinations.

A simple and rapid dispersive liquid-liquid microextraction (DLLME) technique coupled with gas chromatography-flame ionization detection (GC-FID) and gas chromatography-mass spectrometry (GC-MS) was developed for the extraction, preconcentration, and analysis of triazole pesticides (penconazole, hexaconazole, tebuconazole, triticonazole, and difenoconazole) in cow milk samples. Initially to 5 mL milk sample, NaCl and acetonitrile were added as salting-out agent and extraction solvent, respectively. After manual shaking, the mixture was centrifuged. In the presence of sodium chloride, a two-phase system was formed: upper phase, acetonitrile containing triazole pesticides and lower phase, aqueous phase containing soluble compounds and the precipitated proteins. After the extraction of pesticides from milk, a portion of supernatant phase (acetonitrile) was removed, mixed with chloroform at microliter level and rapidly injected by syringe into 5 mL distilled water. In this process, triazole pesticides were extracted into fine droplets of chloroform (as extraction solvent). After centrifugation, the fine droplets of chloroform were sedimented in bottom of the conical test tube. Finally, GC-FID and GC-MS were used for the separation and determination of analytes in the sedimented phase. Some important parameters like type of solvent for extraction of pesticides from milk, salt amount, the volume of extraction solvent, etc., which affect the extraction efficiency, were completely studied. Under the optimum conditions, enrichment factors were in the range of 156-380. The linear ranges of calibration curves were wide and limits of detection (LODs) and limits of quantification (LOQs) were between 4-58 and 13-180 µg/L, respectively. This method is very simple and rapid, requiring <15 min for sample preparation.

Evaluation of a new method for chemical coating of aluminum wire with molecularly imprinted polymer layer. Application for the fabrication of triazines selective solid-phase microextraction fiber.

A new solid-phase microextraction (SPME) fiber is fabricated through ultra violet irradiation polymerization of ametryn-molecularly imprinted polymer on the surface of anodized-silylated aluminum wire. The prepared fiber is durable with very good chemical and thermal stability which can be coupled to GC and GC/MS. The effective parameters on the fabrication and application procedures such as spraying mode, ultra violet irradiation (polymerization) time, number of sprayings and polymerizations, pH and ionic strength of sample and extraction time were optimized. This fiber shows high selectivity with great extraction capacity toward triazines. SPME and GC analysis of ametryn, prometryn, terbutryn, atrazine, simazine, propazine and cyanazine using the fabricated fiber result in the detection limits of 9, 32, 27, 43, 51, 74 and 85 ng mL(-1), respectively. The reliability of the prepared fiber in real samples has been investigated and proved by using spiked tap water, rice, maize and onion samples.

Coupling stir bar sorptive extraction-dispersive liquid-liquid microextraction for preconcentration of triazole pesticides from aqueous samples followed by GC-FID and GC-MS determinations.

Stir bar sorptive extraction (SBSE) combined with dispersive liquid-liquid microextraction (DLLME) has been developed as a new approach for the extraction of six triazole pesticides (penconazole, hexaconazole, diniconazole, tebuconazole, triticonazole and difenconazole) in aqueous samples prior to GC-flame ionization detection (GC-FID). A series of parameters that affect the performance of both steps were thoroughly investigated. Under optimized conditions, aqueous sample was stirred using a stir bar coated with octadecylsilane (ODS) and then target compounds on the sorbent (stir bar) were desorbed with methanol. The extract was mixed with 25 microL of 1,1,2,2-tetrachloroethane and the mixture was rapidly injected into sodium chloride solution 30% w/v. After centrifugation, an aliquot of the settled organic phase was analyzed by GC-FID. The methodology showed broad linear ranges for the six triazole pesticides studied, with correlation coefficients higher than 0.993, lower LODs and LOQs between 0.53-24.0 and 1.08-80.0 ng/mL, respectively, and suitable precision (RSD < 5.2%). Moreover, the developed methodology was applied for the determination of target analytes in several samples, including tap, river and well waters, wastewater (before and after purification), and grape and apple juices. Also, the presented SBSE-DLLME procedure followed by GC-MS determination was performed on purified wastewater. Penconazole, hexaconazole and diniconazole were detected in the purified wastewater that confirmed the obtained results by GC-FID determination. In short, by coupling SBSE with DLLME, advantages of two methods are combined to enhance the selectivity and sensitivity of the method. This method showed higher enrichment factors (282-1792) when compared with conventional methods of sample preparation to screen pesticides in aqueous samples.

Investigation of pencil leads fiber efficiency for SPME of trace amount of methamphetamine from human saliva prior to GC-MS analysis.

The efficiency of pencil lead fiber was investigated for effective head-space solid-phase microextraction (HS-SPME) of methamphetamine (MAMP) from aqueous standard solutions without chemical derivatization prior to gas chromatography (GC) and gas chromatography-mass spectrometry (GC-MS) analyses. Most effective experimental parameters such as extraction temperature and time, sample pH, and salting out were studied and optimized. At the optimum conditions, the efficiency of this fiber was compared with polyacrylate (PA) commercial fiber, which is most selective for volatile and semi-volatile compounds. The results obtained prove the suitability of modified pencil-lead fiber for sampling of the studied compound from aqueous solutions. Under optimum conditions, the calibration plot was linear in the range of 40-8000 ng/mL (r = 0.998), and the detection limit was 27 ng/mL (n = 3). The proposed method was successfully applied for HS-SPME of MAMP from 200 microL human saliva, which has been spiked with trace amounts of MAMP (160 ng/mL) followed by GC-MS monitoring.

SPME and GC-MS analysis of triethylene glycol dimethacrylate released from dental composite.

A solid-phase microextraction (SPME) coupled with gas chromatography followed by mass spectrometry was developed for the determination of triethylene glycol dimethacrylate (TEGDMA) in aqueous media originated from cured dental composite. Cylindrical specimens of a common dental composite were cured and immersed for 48 h in 3 mL portions of human saliva and also some non-biologic media e.g., pure water and Ringer's solution. The extraction was carried out by direct SPME for 15 min. The efficiency and reliability of some commercially available and modified pencil lead fibers were evaluated for the extraction of interest compound from aqueous media. Some effective and experimental parameters of SPME and gas chromatography procedures were examined and optimized. The obtained results reveal that the direct SPME using the modified pencil lead is very effective and can extract TEGDMA with a good selectivety from among various compounds such as 2,6-di-tert-butyl-4-methyl phenol (buylated hydroxy toluene) (BHT), 2-propenoic acid, 2-methyl-oxybis (2,1-ethanediyl oxy-2,1-ethanediyl) ester (TEEGDMA), 3,5-di-t-butyl-4-hydroxy benzaldehyde, benzoic acid 4 (dimethyl-amino)-ethyl ester (DMA BEE), 2-propenoic acid, 2-methyl-dodecyl ester (methacrylic acid, dodecyl ester), 2-ethoxy ethyl methacrylate, and drometrizole (TINP). The results obtained also prove that the studied composite releases 11.0, 13.4, and 28.3 microg/mL TEGDMA into distilled water, Ringer's solution, and saliva, respectively, at 48 h of the exposition.

Preparation and binding study of solid-phase microextraction fiber on the basis of ametryn-imprinted polymer: application to the selective extraction of persistent triazine herbicides in tap water, rice, maize and onion.

A monolithic ametryn molecular-imprinted polymer based on a simple polymerization method was fabricated for use as new solid-phase microextraction (SPME) fiber, which can be coupled with GC and GC/MS for selective extraction and analysis of triazine herbicides. Methacrylic acid (MAA), ethylene glycol dimethacrylate (EDMA) and ametryn bear role of functional monomer, cross-linker and template, respectively. In the optimized conditions the fabricated fiber showed better molecular recognition abilities for methylthiotriazine herbicides than chloro-triazine herbicides. By use of bi-Langmuir isotherm model the evaluated equilibrium constants for ametryn were 0.01 and 890.69 microM(-1), and the numbers of binding sites were 129.98 and 5.82 nmol g(-1), respectively. The high extraction efficiency was obtained for ametryn, prometryn, terbutryn, atrazine, simazine, propazine, and cyanazine, yielding the detection limits of 14, 28, 45, 56, 85, 95 and 74 ng mL(-1), respectively by GC with flame ionization detection. The reliability of the prepared fiber for extraction of ametryn and other analogues in real samples has been investigated and proved by using spiked samples such as tap water, rice, maize, and onion.

Ultrasonic assisted SPME coupled with GC and GC-MS using pencil lead as a fiber for monitoring the organic volatile impurities of ceftazidime.

A simple, rapid, non-destructive, and in-situ method for the isolation and sampling of organic volatile impurities in Ceftazidime is developed using solid-phase microextraction (SPME). For the monitoring of the extracted compounds, gas chromatography (GC) and GC-mass spectrometry analyses are used. The effective factors such as nature of the fiber, SPME mode, extraction temperature, and ultrasonic assistance have been investigated and detailed here. Qualification studies reveal the existence of pyridine (as a degradation product of ceftazidime) and the residual solvents; acetone, methylene-chloride, and diethylamine are the main impurities in the studied pharmaceutical. External standard method is used for quantitative analysis. The % relative standard deviation values are below 10%, and the limits of detection for the detected solvents are 1.06, 0.98, 0.83, and 0.51 ppm, respectively. The proposed method is both accurate and linear and could be used in quality control of ceftazidime and also its stability investigations.

Forensic discrimination of blue ballpoint pen inks based on thin layer chromatography and image analysis.

This article aims to provide a new and fast method for differentiation of inks on a questioned document. The data acquisition was carried out by designing specific image analysis software for evaluating thin layer chromatograms (TLC-IA). The ink spot was extracted from the document using methanol and separated by TLC using plastic sheet silica gel 60 without fluorescent indicator, and a mixture of ethyl acetate, ethanol, and water (70:35:30, v/v/v) as mobile phase. To discriminate between different pen inks, new software was designed on the basis of intensity profile of red, green, and blue (RGB) characteristic. In practice, after development of chromatogram, the chromatograms were scanned by ordinary office scanner, intensity profiles of RGB characteristics on the development straight of each sample were produced and compared with the mentioned software. RGB profiles of ballpoint inks from various manufacturers showed that the patterns in most cases were distinctly different from each other. This new method allowed discriminating among different pen inks with a high reliability and the discriminating power of 92.8%. Blue ballpoint pen inks of 41 different samples available on the local market were successfully analyzed and discriminated.

Preparation of new solid phase micro extraction fiber on the basis of atrazine-molecular imprinted polymer: application for GC and GC/MS screening of triazine herbicides in water, rice and onion.

A simple polymerization strategy has been used to produce a monolithic solid phase micro extraction (SPME) fiber on the basis of molecularly imprinted polymer able to couple with GC and GC-MS for selective extraction and analysis of triazine herbicides. A fiber was produced by copolymerization of methacrylic acid-ethylene glycol dimethacrylate imprinted with atrazine. The effective factors influencing the polymerization have been investigated and are detailed here. At the optimum conditions the prepared fiber is firm, inexpensive, durable and thermally stable up to 280 degrees C which has vital importance in SPME coupled with GC or GC/MS. In addition, the influences of pH, extraction time and temperature on the extraction efficiency of analytes were optimized. Selectivity of prepared fibers in relation to triazine herbicides and some of the other pesticide has been investigated. The high extraction efficiency was obtained for atrazine, simazine, propazine, cyanazine, ametryn, terbutryn and prometryn yielding the detection limits of 20, 70, 80, 81, 69, 88 and 68 ng mL(-1), respectively and the high quantities of recoveries. The reliability of prepared fiber to extraction of atrazine and other analogues in real samples has been investigated and proved by implementation of SPME in spiked samples such as tap water, onion and rice.

Preparation and evaluation of solid-phase microextraction fibers based on monolithic molecularly imprinted polymers for selective extraction of diacetylmorphine and analogous compounds.

All of the studies on solid-phase microextraction based on molecularly imprinted polymers up to now have been carried out on the synthesis of the polymer on the surface of the fiber which is brittle and the polymer coating strips during handling. The objective of this study was to develop a method for fabrication of a monolithic and robust solid-phase microextraction fiber on the basis of molecularly imprinted polymer for selective extraction of diacetylmorphine and its structural analogues followed by their GC or GC/MS analysis. A fiber was produced by copolymerization of methacrylic acid-ethylene glycol dimethacrylate imprinted with diacetylmorphine. The effective factors influencing the polymerization have been investigated and are detailed here. Also, the influences of pH, extraction time and temperature on the extraction efficiency of analytes were investigated. The prepared fiber was thermally stable up to 300 degrees C which has vital importance in SPME coupled with GC or GC/MS. The adsorption isotherm modeling was performed by fitting the data of studied compounds to bi-Langmuir isotherm model. The evaluated equilibrium constants for diacetylmorphine were 0.011 and 1824.72 microM(-1), and the number of binding sites was 170.37 and 4.64 nmolg(-1), respectively. This fiber was successfully used for extraction of template molecule from aqueous solution and further analysis with GC or GC/MS. The high extraction efficiency was obtained for diacetylmorphine, 6-monoacetylcodeine, and 6-monoacetylmorphine, yielding the detection limits of 300, 47, and 1 ngmL(-1), respectively.