Showing papers in "Chromatographia in 2007"

Determination of Trihalomethanes in Drinking Water by Dispersive Liquid–Liquid Microextraction then Gas Chromatography with Electron-Capture Detection

Abstract: Dispersive liquid–liquid microextraction (DLLME) has been used for preconcentration of trihalomethanes (THMs) in drinking water. In DLLME an appropriate mixture of an extraction solvent (20.0 μL carbon disulfide) and a disperser solvent (0.50 mL acetone) was used to form a cloudy solution from a 5.00-mL aqueous sample containing the analytes. After phase separation by centrifugation the enriched analytes in the settled phase (6.5 ± 0.3 μL) were determined by gas chromatography with electron-capture detection (GC–ECD). Different experimental conditions, for example type and volume of extraction solvent, type and volume of disperser solvent, extraction time, and use of salt, were investigated. After optimization of the conditions the enrichment factor ranged from 116 to 355 and the limit of detection from 0.005 to 0.040 μg L−1. The linear range was 0.01–50 μg L−1 (more than three orders of magnitude). Relative standard deviations (RSDs) for 2.00 μg L−1 THMs in water, with internal standard, were in the range 1.3–5.9% (n = 5); without internal standard they were in the range 3.7–8.6% (n = 5). The method was successfully used for extraction and determination of THMs in drinking water. The results showed that total concentrations of THMs in drinking water from two areas of Tehran, Iran, were approximately 10.9 and 14.1 μg L−1. Relative recoveries from samples of drinking water spiked at levels of 2.00 and 5.00 μg L−1 were 95.0–107.8 and 92.2–100.9%, respectively. Comparison of this method with other methods indicates DLLME is a very simple and rapid (less than 2 min) method which requires a small volume of sample (5 mL).

Investigating the Effect of Chromatographic Conditions on Retention of Organic Acids in Hydrophilic Interaction Chromatography Using a Design of Experiment

Abstract: Small organic acids have shown significant retention on various stationary phases, such as amide, amino, aspartamide, silica and sulfobetaine phase commonly used in hydrophilic interaction chromatography (HILIC). This study investigated the effect of chromatographic conditions on the retention behavior of organic acids in HILIC using the tool of design of experiment (DOE). The results of the DOE study indicated that both the content of organic solvent (i.e., acetonitrile) and salt concentration in the mobile phase had significant effects on the retention of organic acids. Higher content of organic solvent in the mobile phase led to a significant increase in retention on all types of stationary phases. Increasing salt concentration also resulted in a moderate increase in retention; however, the effect of salt concentration varied with the type of stationary phase. The study also revealed that column temperature had less impact on retention than organic solvent content and salt concentration in HILIC.

Rapid Extraction of Volatile Compounds Using a New Simultaneous Microwave Distillation: Solvent Extraction Device

Abstract: Simultaneous distillation–extraction (SDE) is routinely used by analysts for sample preparation prior to gas chromatography analysis. In this work, a new process design and operation for microwave assisted simultaneous distillation–solvent extraction (MW-SDE) of volatile compounds was developed. Using the proposed method, isolation, extraction and concentration of volatile compounds can be carried out in a single step. To demonstrate its feasibility, MW-SDE was compared with the conventional technique, SDE, for gas chromatography-mass spectrometry (GC-MS) analysis of volatile compounds in a fresh aromatic herb, Zygophyllum album L., a wild salty desert herb belonging to the family Zygophyllaceae. SDE method required a long time (3 h) to isolate the volatile compounds, and large amounts of organic solvent (200 mL of hexane) for further extraction, while MW-SDE needed shorter time (only 30 min) to prepare the sample, and less amount of organic solvent (10 mL of hexane). These results show that MW-SDE–GC-MS is a simple, rapid and solvent-less method for the determination of volatile compounds from aromatic plants.

Simultaneous Determination of Phytohormones in Plant Extracts using SPME and HPLC

Abstract: Solid-phase microextraction followed by HPLC was used for the determination of indole-3-acetic acid (IAA), abscisic acid (ABA), indole-3-butyric acid (IBA) and 1-naphthylacetic acid (NAA) in plant samples. Parameters influencing performance, including pH, salinity, extraction time, fiber coating and temperature, were optimized. A Carbowax-coated fiber was chosen for determination due to much higher extraction efficiency compared to polyacrylate fibers. The dynamic ranges spanned over three orders of magnitude. The LOD/(LOQ) values of the target compounds in pure water were 0.149(0.497), 0.442(1.472), 0.121(0.403), 0.058(0.193) μg L−1 for IAA, ABA, IBA and NAA respectively. The method was successfully applied to the analysis of xylem fluid from Musa basjoo stem obtaining recoveries of 98.85% (IAA), 94% (IBA) and 94.30% (NAA). The method was also successfully applied to the analysis of these four target compounds in the hyperaccumulating plant, Viola baoshanensis. The results matched quite well with ones obtained by solid phase extraction followed by HPLC. The method developed was superior when applied to liquid samples because matrix effects could be eliminated.

RP-LC for Determination of Plastochromanol, Tocotrienols and Tocopherols in Plant Oils

Abstract: An isocratic high performance liquid chromatographic method, with the application of C18 and C30 reverse-phase column and fluorescence detection, is described for the analysis of plastochromanol, tocotrienols and tocopherols in plant seed oils. The solvent systems have been optimized to obtain high resolution for all tocochromanols and relatively short analysis time. The use of reverse-phase columns for plastochromanol analysis, previously not reported, enables very sensitive and selective detection of plastochromanol which under the described separation conditions did not interfere with tocochromanols or any other compounds. The sample extraction method is fast, simple and highly efficient. The obtained results show that plastochromanol was present in most of the investigated seed oils. Its level was the highest in flax (17–30 mg/100 g oil), rape (8.5–9), camelina (4.3), peanut (1.95), corn (1.69) and grape (1.31) seed oils. Its level in the other investigated oils was below 1 mg/100 g oil, and only in sesame and coconut oils it was not detected. Tocotrienols were found in most of the oils but their content was usually very low ( 1 mg/100 g oil. Tocopherol content and isomer composition was within the earlier reported literature values for the investigated oils.

Development and Validation of Improved Reversed Phase-HPLC Method for Simultaneous Determination of Curcumin, Demethoxycurcumin and Bis-Demethoxycurcumin

Abstract: Isocratic reversed phase high performance liquid chromatographic (HPLC) method using RP C18 column was developed for simultaneous determination of the curcuminoids. Mobile phase consisted of acetonitrile:0.1% trifluro-acetic acid (50:50) and flow rate was 1.5 mL min−1 and elution was monitored at 420 nm. Validation in selected conditions showed that the chosen method is sensitive, selective, precise and reproducible with linear response of detector for the simultaneous determination of curcumin (C), demethoxycurcumin (DMC) and bis-demethoxycurcumin (BDMC). The limits of detection were 27.99, 31.91 and 21.81 ng mL−1 for C, DMC and BDMC, respectively. Limits of quantitation for C, DMC and BDMC, were 84.84, 96.72 and 66.10 ng mL−1, respectively. Linear range was form 100 to 600 ng mL−1. The mean ± SD percent recoveries of curcuminoids were 99.87 ± 0.34, 100.09 ± 0.48 and 100.10 ± 0.60% of C, DMC and BDMC, respectively. Further, the method was used for quantitation of curcuminoids from turmeric rhizome.

2D LC Separation and Determination of Bradykinin in Rat Muscle Tissue Dialysate with On-Line SPE-HILIC-SPE-RP-MS

Abstract: A 2D liquid chromatography (LC) system using hydrophilic interaction chromatography (HILIC) and reversed phase columns has been employed for comprehensive (LC × LC) separation of rat muscle tissue micro-dialysate. Incorporation of an on-line reverse-phase solid phase extraction (SPE) enrichment column in front of the first dimension enabled aqueous samples with high salt concentrations to be injected directly without compromising the chromatographic performance of the HILIC column. Since the SPE enrichment column allowed injection of large sample volumes (e.g. 450 μL), a capillary HILIC column (inner diameter 0.3 mm) could be employed instead of a larger column which is often used in the first dimension to load sufficient amounts of sample. The two chromatographic dimensions were connected using a column selector system with 18, 1.0 mm I.D. C18 “transition” SPE columns. A PLRP C18 column was used in the second dimension. The 2D LC system’s performance was evaluated with a tryptic digest mixture of three model proteins. Good trapping accuracy (HILIC→transition SPE→RP recovery >95%) and repeatability (within-and between day retention time RSDs of first and second dimension chromatography >1%) was achieved. A dialysis sample of rat muscle tissue was separated with the 2D system, revealing complexity and large differences in concentrations of the various compounds present, factors which could potentially interfere with the quantification and monitoring of two target analytes, arg-bradykinin and bradykinin. Subsequently, “Heart-cut” 2D LC-electrospray–mass spectrometry (ESI–MS) with post-column on-line standard injection was employed to monitor arg-bradykinin and bradykinin levels as a function of various muscle conditions. The method’s quantification precision was RSD = 3.4% for bradykinin.

Simultaneous HPLC Analysis of Olmesartan and Hydrochlorothiazide in Combined Tablets and in vitro Dissolution Studies

Abstract: A simple, rapid and reproducible HPLC method was developed and validated for the simultaneous determination of olmesartan (OLM) medoxomil and hydrochlorothiazide (HCT) in combined tablets. Chromatography was carried out on a 4.6 mm I.D × 200 mm, 5 μm cyano column with methanol–10 mM phosphoric acid containing 0.1% triethylamine (pH 2.5, 50:50 v/v) at a flow rate of 1.0 mL min−1 and UV detector was set at 260 nm. Valsartan (VAL) was used as internal standard (IS). A linear response was observed in the range of 0.2–6 μg mL−1 (r 2 = 0.9998) for OLM and 0.1–4 μg mL−1 (r 2 = 0.9999) for HCT, respectively. The method showed good recoveries (99.56% for OLM and 99.48% for HCT) and the relative standard deviation (RSD) values for intra- and inter-day precision were 0.70–1.59 and 0.80–2.00% for OLM and 1.20–1.37 and 1.63–1.93% for HCT, respectively. The developed method was applied successfully for quality control assay of OLM and HCT in combined tablets and in vitro dissolution studies.

Determination of Pantoprazole, Rabeprazole, Esomeprazole, Domperidone and Itopride in Pharmaceutical Products by Reversed Phase Liquid Chromatography Using Single Mobile Phase

Abstract: A simple, sensitive, and precise high performance liquid chromatographic method for the analysis of pantoprazole, rabeprazole, esomeprazole, domperidone and itopride, with ultraviolet detection at 210 nm, has been developed, validated, and used for the determination of compounds in commercial pharmaceutical products. The compounds were well separated on a Hypersil BDS C18 reversed-phase column by use of a mobile phase consisting of 0.05 M, 4.70 pH, potassium dihydrogen phosphate buffer - acetonitrile (720:280 v/v) at a flow rate of 1.0 mL min−1. The linearity ranges were 400–4,000 ng mL−1 for pantoprazole, 200–2,000 ng mL−1 for rabeprazole, 400–4,000 ng mL−1 for esomeprazole, 300–3,000 ng mL−1 for domperidone and 500–5,000 ng mL−1 for itopride. Limits of detection (LOD) obtained were: pantoprazole 147.51 ng mL−1, rabeprazole 65.65 ng mL−1, esomeprazole 131.27 ng mL−1, domperidone 98.33 ng mL−1 and itopride 162.35 ng mL−1. The study showed that reversed-phase liquid chromatography is sensitive and selective for the determination of pantoprazole, rabeprazole, esomeprazole, domperidone and itopride using single mobile phase.

A Validated and Densitometric HPTLC Method for the Quantification of Withaferin-A and Withanolide-A in Different Plant Parts of Two Morphotypes of Withania somnifera

Abstract: A simple, sensitive and accurate high performance thin layer chromatographic (HPTLC) method has been developed for the estimation of withaferin-A and withanolide-A in different plant parts such as, leaf, root, stem and fruit of two morphotypes of Withania somnifera. HPTLC of W. somnifera methanolic extract was performed on Si 60 F254 (20 cm × 20 cm) plates with toluene:ethyl acetate:formic acid (5:5:1), as mobile phase. Quantitative evaluation of the plate was performed in the absorption-reflection mode at 530 nm. The method was validated for precision, repeatability, and accuracy. The average recovery of withaferin-A and withanolide-A in two levels were 96.0 and 96.7%, showing the excellent reproducibility of the method. The calibration curves were linear for both in the range of 200–3,200 ng. The technique has been applied, for the first time, for the estimation of withaferin-A and withanolide-A in different parts of the two morphotypes of Withania somnifera. The method is simple, precise, specific, sensitive and accurate and can be used for routine analysis as well as for quality control of raw materials and herbal formulations.

Hydrodistillation-Solvent Microextraction and GC-MS Identification of Volatile Components of Artemisia aucheri

Abstract: A new, simple hydrodistillation–solvent microextraction (HD–SME) technique has been used for analysis of the volatile components of the aerial parts of Artemisia aucheri. The components were collected in a single microdrop, and this was injected directly for gas chromatographic–mass spectrometric (GC–MS) analysis. The effects on extraction efficiency of extraction solvent, sample mass, microdrop volume, and extraction time were optimized by use of a simplex method. The identities of the components of HD–SME extracts were confirmed according to their retention indexes and mass spectra with those of standards. Forty components were extracted and identified by use of the method; 1,8-cineol (22.8%), chrysanthenone (18.16%), α-pinene (8.33%), and mesitylene (7.41%) were the major constituents. The results obtained from the microextraction method were compared with those obtained by conventional hydrodistillation.

HPLC Quantification of Vitexine-2″-O-rhamnoside and Hyperoside in Three Crataegus Species and Their Antimicrobial and Antiviral Activities

Abstract: Crataegus sp., also known as “hawthorn”, is one of the most prescribed herbal drugs and approved to be used against congestive heart failure. The extract is required to be standardized according to its flavonoid (vitexine-2″-O-rhamnoside and hyperoside) and oligomeric procyanidin content by the European Pharmacopoeia (EP). In this study, the leaves and berries of three Crataegus species including C. aronia var. aronia, C. monogyna ssp. monogyna (from two different localities) as well as C. pseudoheterophylla growing in Turkey were evaluated for their vitexine-2″-O-rhamnoside and hyperoside content by reversed-phase HPLC as well as their total procyanidin amount by a spectrophotometric method. In addition, antibacterial, antifungal, and antiviral activities of the extracts were also determined. Our results indicated that C. monogyna ssp. monogyna samples of both localities met the criteria required by the EP for their total flavonoid amount (2.49 and 2.86%) and total proanthocyanidin content (1.56 and 2.22%). According to data we obtained, the extracts have been verified to be highly effective against Candida albicans and Herpes simplex virus.

GC–MS Analysis of the Essential Oils of Piper nigrum L. and Piper longum L.

Abstract: A simple, rapid and solvent-free method based on gas chromatography–mass spectrometry (GC–MS) following microwave distillation and headspace solid-phase microextraction (MD–HS-SPME) was developed for the analysis of the essential oils in two traditional Chinese medicines, Piper nigrum L. and Piper longum L. Thirty compounds were separated and identified from P. nigrum L. The main components were β-caryophyllene (23.49%), 3-carene (22.20%), d-limonene (18.68%), β-pinene (8.92%) and α-pinene (4.03 %). Forty-five compounds were separated from P. longum L. and identified. The main components were β-caryophyllene (33.44%), 3-carene (7.58%), eugenol (7.39%), d-limonene (6.70%), zingiberene (6.68%) and cubenol (3.64%). To demonstrate its advantages, MD–HS-SPME was compared to conventional HS-SPME. With conventional HS-SPME, only 28 and 33 compounds were detected in P. nigrum L. and P. longum L, respectively. Relative standard deviation (RSD) values of MD–HS-SPME for the essential oils in P. nigrum L. under optimal conditions were less than 10%. The results show that microwave distillation has a high extract efficiency and good precision and can be used to compare similarities and differences of essential oils.

Effect of Temperature on the Chromatographic Behavior of Epirubicin and its Analogues on High Purity Silica Using Reversed-Phase Solvents

Abstract: The influence of temperature on the retention behavior of epirubicin and its analogues on high purity silica with reversed-phase solvents has been systematically investigated. It was found that temperature effects on retention are highly dependent on the type and concentration of organic modifier, as well as the pH of the mobile phase. In organic-rich mobile phases, the type of organic modifier plays an important role. With an aprotic solvent as modifier, retention times show anomalous increases with elevated temperature. At the same time, both efficiency and resolution are significantly improved but this is not the situation with a protic solvent as modifier. In addition, temperature shows different effects on retention time and selectivity when the pH is changed, and temperature-dependent selectivity reversal is found at higher pHs. In aqueous-rich mobile phases, regardless of the nature of the organic solvent and pH, retention of solutes drops as temperature is raised. It seems that the effect of temperature on chromatographic behavior of the solutes on bare silica using mobile phases containing various organic modifiers or pHs, results from a number of different retention mechanisms.

Quantitative Determination of Four Water-Soluble Compounds in Herbal Drugs from Lamiaceae Using Different Chromatographic Techniques

Abstract: HPTLC-densitometric and HPLC–UV techniques were used for qualitative and quantitative determination of luteolin-7-O-glucuronide, lithospermic acid, rosmarinic acid and caffeic acid in several herbal drugs from the Lamiaceae family: Thymi herba, Serpylli herba, Majoranae herba and Menthae piperitae folium. Unmodified silica gel (HPTLC Si60) and silica gel chemically modified with aminopropyl groups (HPTLC NH2) were used during the investigation process. Among HPTLC methods the best resolution and selectivity was achieved with mobile phases: diisopropyl ether–acetone–formic acid–water (50:30:10:10, v/v/v/v) and acetone–formic acid (85:15, v/v), respectively. Plates were densitometrically evaluated. Contents of analyzed compounds in the studied aqueous extracts prepared from herbal drugs were established using both techniques. The results from the HPTLC-densitometric analysis have been compared with those from HPLC–UV on a C18 column with acetonitrile–water–formic acid as a mobile phase. The chromatographic methods were validated for linearity, LOD, LOQ, repeatability, intermediate precision and recovery. An analysis of variance showed that the HPTLC-densitometric and HPLC–UV methods are equivalent and sufficiently precise for the estimation of polyphenolic compounds mentioned above, in investigated herbal drugs. All of the suggested methods (HPTLC NH2, HPTLC Si60 and HPLC RP18) give results with good agreement.

Simultaneous Determination of Olanzapine and Fluoxetine by HPLC

Abstract: A rapid, specific reversed phase HPLC method has been developed for simultaneous determination of olanzapine and fluoxetine in their formulations. Chromatographic separation of these two pharmaceuticals was carried out on an Inertsil C18 reversed phase column (150 mm × 4.6 mm, 5 μm) with a 40:30:30 (v/v/v) mixture of 9.5 mM sodium dihydrogen phosphate (pH adjusted to 6.8 ± 0.1 with triethylamine), acetonitrile and methanol as mobile phase. The flow rate 1.2 mL min−1 and the analytes are monitored at 225 nm. Paroxetine was used as internal standard. The assay results were linear from 25 to 75 μg mL−1 for olanzapine (r2 ≥ 0.995) and 100–300 μg mL−1 for fluoxetine (r2 ≥ 0.995), showed intra- and inter-day precision less than 1.0%, and accuracy of 97.7–99.1% and 97.9–99.0%. LOQ was 0.005 and 0.001 μg mL−1 for olanzapine and fluoxetine, respectively. Separation was complete in less than 10 min. Validation of the method showed it to be robust, precise, accurate and linear over the range of analysis.

Simultaneous Determination of Tramadol and Acetaminophen in Human Plasma by LC–ESI–MS

Abstract: This study presents a high-performance liquid chromatography–electrospray ionization–mass spectrometric (LC–ESI–MS) method for the simultaneous determination of tramadol and acetaminophen in human plasma using phenacetinum as the internal standard. After alkalization with saturated sodium bicarbonate, both compounds were extracted from human plasma with ethyl acetate and were separated by HPLC on a Hanbon LiChrospher CN column with a mobile phase of 10 mM ammonium acetate buffer containing 0.5% formic acid–methanol (40:60, v/v) at a flow rate of 1 mL min−1. Analytes were determined using electrospray ionization in a single quadrupole mass spectrometer. LC–ESI–MS was performed in the positive selected-ion monitoring (SIM) mode using target ions at [M+H]+ m/z 264.3 for tramadol, [M+H]+ m/z 152.2 for acetaminophen and [M+H]+ m/z 180.2 for phenacetinum. Calibration curves were linear over the range of 5–600 ng mL−1 for tramadol and 0.03–16 μg mL−1 for acetaminophen. The inter-run relative standard deviations were less than 14.4% for tramadol and 12.3% for acetaminophen. The intra-run relative standard deviations were less than 9.3% for tramadol and 7.9% for acetaminophen. The mean plasma extraction recovery for tramadol and acetaminophen were in the ranges of 82.7–85.9 and 83.6–85.3%. The method was applied to study the pharmacokinetics of a new formulation of tramadol/acetaminophen tablet in healthy Chinese volunteers.

Study of Anion Effects on Separation Phenomenon for the Vinyloctylimidazolium Based Ionic Liquid Polymer Stationary Phases in GC

Abstract: Poly-vinyloctylimidazolium ionic liquid polymers with different counter ions (bromide, hexafluorophosphate and bis-trifluoromethanesulfonylimide) were directly coated in capillary fused silica tubing as the stationary phases for gas chromatography. The anion effects on the polymers were examined and discussed. The results suggest that the poly-vinyloctylimidazolium, bis-trifluoromethanesulfonylimide capillary column has the highest thermal stability and separation efficiency. Column-to-column reproducibility was also studied. The results indicate that anions significantly influence ionic liquid polymers which give them potential to extend the range of options for the stationary phases in gas chromatography.

Simultaneous Separation and Determination of Seven Quinolones Using HPLC: Analysis of Levofloxacin and Moxifloxacin in Plasma and Amniotic Fluid

Abstract: A reversed-phase high-performance liquid chromatographic method is described for the determination of seven quinolones in plasma and amniotic fluid. Experimental designs have been applied for the optimization of the method in order to determine the experimental conditions for maximized resolution and minimized retention time. A total desirability function D that weights the responses together was used to optimize the two different responses simultaneously. The experimental responses were fitted into a second order polynomia. The optimum assay conditions were: 15 mM citrate buffer, pH 3.2, 9% MeCN, 5% MeOH, 5 mM TMAB, 1.5 mL min−1 flow rate and 40 °C column temperature. A simple and efficient solid phase extraction has been applied for preparation of samples. The recovery of quinolones is >95%. The optimized assay condition was validated according to Federal Drug Administration (FDA) guidelines to confirm specificity, linearity, accuracy, precision and robustness. The method developed has been applied to quantification of levofloxacin and moxifloxacin in amniotic fluid and plasma.

A Stability-Indicating LC Method for Candesartan Cilexetil

Abstract: An isocratic reversed-phase liquid chromatographic method has been developed for quantitative determination of candesartan cilexetil, used to treat hypertension, in the bulk drug and in pharmaceutical dosage forms. The method is also applicable to analysis of related substances. Chromatographic separation was achieved on a 250 mm × 4.6 mm, 5 μm particle, CN column with a 50:50 (v/v) mixture of phosphate buffer, pH 3.0, and acetonitrile as mobile phase. The flow rate was 1.0 mL min−1 and the detection wavelength was 210 nm. Resolution of candesartan cilexetil and six potential impurities was greater than 2.0 for all pairs of compounds. The drug was subjected to hydrolytic, oxidative, photolytic, and thermal stress and substantial degradation occurred in alkaline and acidic media and under oxidative and hydrolytic stress conditions. The major product obtained as a result of basic hydrolysis was different from that produced by acid hydrolysis and aqueous hydrolysis. The stress samples were assayed against a reference standard and the mass balance was found to be close to 99.6%. The method was validated for linearity, accuracy, precision, and robustness.

LC Determination of Adulterated Saffron Prepared by Adding Styles Colored with Some Natural Colorants

Abstract: A high-performance liquid chromatographic method previously developed (Lozano et al. in J Chromatogr A 830:477–483, 1999) for simultaneous detection, identification and quantification of the secondary metabolites in commercial saffron was extended for the detection of adulterated saffron prepared by adding styles colored with the natural colorants extracted from saffron petals, safflower, madder and red beet. The chromatograms of the methanol-water (50%, v/v) extracts of pure and adulterated saffron were obtained at the assayed wavelengths, 402 (or 254), 260 and 535 (or 440) nm and then by applying two-way analysis of variance (ANOVA) to the obtained data the presence of the styles colored with the colorant of safflower (>14.3%), styles colored with the colorant of madder (>9.1%) and styles colored with the colorant of red beet (>14.3%) in saffron were significantly detected. But the detection of adulterated saffron prepared with the colorant of saffron petals was not successful.

SEC Characterization of Au Nanoparticles Prepared through Seed-Assisted Synthesis

Abstract: In this paper we report the use of size-exclusion chromatography (SEC) for rapid determination of the sizes and size distributions of Au nanoparticles (NPs) prepared by seed-assisted synthesis. Analytical separation of Au NPs was performed in a polymer-based column of pore size 400 nm. We characterized the sizes and size distributions of the Au NPs by using 10 mM sodium dodecyl sulfate (SDS) as mobile phase and obtained a linear relationship (R 2 = 0.986) between retention time and size of Au NPs within the range 9.8–79.1 nm; the relative standard deviations of these retention times were less than 0.3%. These separation conditions were used to characterize the sizes and size distributions of Au NPs prepared by seed-assisted synthesis. In addition to observing the elution times of the Au NPs we also simultaneously characterized their size-dependent optical properties by spectral measurement of the eluting peaks by use of an on-line diode-array detector (DAD), i.e., monitoring of the stability of the Au NP products. By using this approach we found the presence of SDS was beneficial in stabilizing the synthesized Au NPs. We also found that the volume of Au metal ions used affected the sizes of the final products. SEC seems an efficient tool for characterizing the sizes of NPs fabricated by seed-assisted synthesis.

A Rapid Method for the Determination of Organochlorine, Pyrethroid Pesticides and Polychlorobiphenyls in Fatty Foods Using GC with Electron Capture Detection

Abstract: A new, single-step extraction and purification method was developed for the separation of 26 organochlorine pesticides (OCPs), three pyrethroid pesticides (PPs) and six polychlorinated biphenyls (PCBs) from fatty foods of either animal or vegetable origin. The method includes homogenisation of extracted fat and diatomaceous earth. Separation was achieved using a mini Pasteur pipette where a matrix solid-phase dispersion extraction was carried out with only 5 mL of dimethyl sulphoxide as an eluting solvent. A Pasteur pipette was joined to a prepacked slurry filled Florisil column, water deactivated to 15% where a liquid–liquid extraction and adsorption chromatography successively took place. The elution of OCPs, PPs and PCBs was performed with n-hexane/diethyl ether. Recoveries for PCBs were from 81 to 86% and for OCPs 68 to 94%, except for β-HCH, which gave lower, more variable recoveries. Excellent recoveries were obtained for pyrethroid pesticides, mostly more than 80%. The method was applied to 509 fatty samples for monitoring of these compounds. GC, with two columns connected to two electron capture detectors (ECD), was used.

Simultaneous Determination of Trichothecenes A, B, and D in Maize Food Products by LC–MS–MS

Abstract: Two new methods of analysis, based on liquid chromatography–tandem mass spectrometry, for simultaneous determination of trichothecenes A, B, and D in maize flour and oil have been developed and validated in accordance with European Commission decision 2002/657/EC (recovery, CCα, CCβ, and precision). The trichothecenes were extracted from maize flour by matrix solid-phase dispersion, with recoveries ≥79%, and from maize oil by liquid–liquid extraction, with recoveries ≥78%. Limits of quantitation ranged between 0.03 and 50 μg kg−1, depending on the electrospray response to each analyte and on the matrix. Monitoring of flour and oil samples with this HPLC–MS–MS method revealed the presence of deoxynivalenol, T-2 toxin, and diacetoxyscirpenol at very low concentrations.

MSPD Extraction of Sulphonamides from Meat followed by LC Tandem MS Determination

Abstract: In this paper an extraction procedure is presented for sulphonamides (SAs) in animal tissues (raw meat and meat-based baby food), based on matrix solid phase dispersion (MSPD). Determination was carried out using liquid chromatography coupled with tandem mass spectrometry. In complex matrices extraction is usually the critical step of analysis: several procedures were employed for the recovery of SAs in animal tissues, but often they entail time and solvent-consuming processes. MSPD has demonstrated itself to be a very efficient extraction technique for matrices such as animal tissues, with simplified and shortened procedures, and very low solvent consumption. This procedure allowed to obtain quantitative recovery, high selectivity improved by a cool eluant, and easy application. Good recoveries are accompanied by low RSDs and not a significative matrix effect. The MSPD procedure, coupled with LC-MS-MS analysis, provides very interesting LODs, due also to the concentration step. Validation is carried out following the EU guidelines for confirmation methods (EU Dec. 657/02).

Comparison of UPLC and HPLC for Determination of trans-10-Hydroxy-2-Decenoic Acid Content in Royal Jelly by Ultrasound-Assisted Extraction with Internal Standard

Abstract: The ultra performance liquid chromatography (UPLC) and high performance liquid chromatography (HPLC) method was developed and compared to detect the trans-10-hydroxy-2-decenoic acid (10-HDA) content in royal jelly cream and lyophilized powder. The sample was extracted using absolute ethanol based on the ultrasound-assisted extraction. Chromatographic separation of 10-HDA and methyl 4-hydroxybenzoate as internal standard was carried out on a Nova-pak® C18 column for HPLC and on Acquity BEH C18 column for UPLC. In the HPLC system, the average recoveries were 95.0–99.2% (n = 5) with relative standard deviation (RSD) values of 1.1–2.1% for royal jelly cream and 98.0–100.0% (n = 5) with RSD values of 1.6–3.0% for lyophilized powder, respectively. The limit of detection (LOD) and limit of quantitation (LOQ) were 0.5 and 1.5 mg kg−1 for both royal jelly cream and lyophilized powder. In the UPLC system, the limit of detection (LOD) and limit of quantitation (LOQ) were 0.3 and 1.0 mg kg−1 for both royal jelly cream and lyophilized powder. The major advantages of UPLC, using 1.7 μm particles, over HPLC are the speed of analysis, the narrower peaks and the decrease of solvent consumption for the 10-HDA in the analyses of beeproducts. The two methods were validated for the determination of practical royal jelly products. The concentration of 10-HDA ranges from 1.26 to 2.25% for pure royal jelly cream samples and 3.01–6.26% for royal jelly lyophilized powder samples. For 30 royal jelly products, the 10-HDA content varied from no detectable to 1.005%.

Directly Suspended Droplet Microextraction and Analysis of Amitriptyline and Nortriptyline by GC

Abstract: Directly Suspended Droplet Microextraction (DSDME) was used for the determination of two tricyclic antidepressant drugs (TCAs), amitriptyline and nortriptyline. In this technique, an aqueous sample is agitated with a stirring bar, creating a mild vortex at the center of the vial. A droplet of an immiscible organic solvent is placed at the bottom of the vortex. After 20 min a portion of the organic droplet is withdrawn with a syringe and injected into the GC. Experimental conditions, such as the extraction solvent, extraction time, solvent volume, stirring rate, pH and salt addition were optimized. In order to evaluate the practical application of the method, relative standard deviations, linearity range and limits of detection were calculated. Typical enrichment factors were 167 and 179 for amitriptyline and nortriptyline, respectively. The method was applied to the determination of these drugs in urine samples.

Rapid Determination of Volatile Compounds in Toona sinensis (A. Juss.) Roem. by MAE-HS-SPME Followed by GC–MS

Abstract: Toona sinensis (A. Juss.) Roem. belonging to the Toona family was used as one of the traditional Chinese medicines in China. Based on microwave-assisted extraction (MAE) and headspace solid-phase microextraction followed by gas chromatography-mass spectrometry, the volatile compounds of Toona sinensis (A. Juss.) Roem. were determined. Results indicated that the optimum condition of the determination of the volatile compounds in Toona sinensis (A. Juss.) Roem. was achieved with the experimental parameters including fiber coating of PDMS/DVB, microwave power of 400 W and irradiation time of 4 min. Under the optimal conditions, for the first time, 45 volatile compounds were separated and identified from the fresh leaves of Toona sinensis (A. Juss.) Roem. The highest content component of the 45 compounds was trans-Caryophyllene (21.422%). Relative standard deviation (RSD) values <9% showed that the present method has good precision. The experimental results demonstrate that MAE-HS-SPME followed by GC–MS is a simple, time-saving and solvent-free method, and it is a potential analytic tool for the determination of the volatile compounds of TCMs.

A Simple Liquid Chromatography Method for the Determination of Captopril in Urine

Abstract: A simple and specific method for the determination of total captopril in human urine was developed 2-Chloro-1-methylquinolinium tetrafluoroborate was used as a thiol precolumn derivatizing reagent after conversion of a disulfide forms to free captopril with tris(2-carboxyethyl)phosphine hydrochloride The 2-S-quinolinium derivative of captopril was separated on a Zorbax SB C-18 column using reversed-phase ion-paring chromatography and monitored by spectrophotometric detector at 355 nm The calibration curve for the derivatized captopril showed linearity in the range 01–200 μmol L−1 of urine with a regression coefficient corresponding to 09999 The detection and quantitation limits were 005 and 01 μmol L−1, respectively The intra-day imprecision was from 001 to 1058% This method can be used for routine clinical monitoring of the thiol-drug Omission of the reduction step gives result for concentration of the reduced form of captopril

Determination of Organophosphorus Pesticides in Soybean Oil, Peanut Oil and Sesame Oil by Low-Temperature Extraction and GC-FPD

Abstract: A low-temperature clean-up method for residue determination was developed and validated for 14 organophosphorus pesticides in soybean oil, peanut oil and sesame oil by gas chromatography with flame photometric detector (GC-FPD). A different matrix influenced the response and retention time of pesticides. Hence matrix-matched calibration standards were used to counteract the matrix effect. The pesticide responses in blank samples of soybean oil, peanut oil and sesame oil were within the linear range of 0.02–1 mg kg−1 and the correlation coefficients were higher than 0.9989. Average recoveries obtained from different oil samples at three fortified levels were higher than 50% with relative standard deviations (RSDs) of less than 15%. The limit of detections (LODs) of studied pesticides ranged from 2 to 5 μg kg−1. Thirty-nine commercial samples were analyzed, and the results were confirmed by gas chromatography–mass spectrometry (GC–MS) in selective ion monitoring (SIM) mode.