Analysis of triclosan and triclocarban in soil and biosolids using molecularly imprinted solid phase extraction coupled with HPLC-UV

A molecularly imprinted polymer (MIP) able to selectively bind triclosan (TCS) and triclocarban (TCC), commonly used antibacterial agents in many consumer products, was prepared using noncovalent molecular imprinting methods. The prepared MIP was evaluated as a selective sorbent in SPE for sample cleanup before HPLC-UV analysis of TCS and TCC in soil and biosolid samples. The MIP was also compared with commercially available C18 SPE sorbent. The molecularly imprinted SPE (MISPE) developed in this study was more efficient than C18 SPE for the cleanup of extracts of soil and biosolid samples prior to the analysis of TCC and TCS using HPLC-UV. The LOQ values for both TCC and TCS in the soil samples were determined to be 40 microg/kg; in the biosolid samples, the LOQ values were 100 and 300 microg/kg for TCC and TCS, respectively. Compared to C18 SPE, using MISPE for sample cleanup may result in a significant reduction of analytical cost, because one MIP can be reused up to 35 times and HPLC-UV instead of HPLC/MS can be used for instrumental analysis following sample cleanup by MISPE.     

Evaluation of a new automated cleanup system for the analysis of polychlorinated dibenzo-p-dioxins and dibenzofurans in environmental samples

An automated cleanup system (Power-Prep, Fluid Management Systems, Inc.) was evaluated for the analysis of polychlorinated dibenzo-p-dioxins and dibenzofurans (PCDD/PCDF) in environmental samples. The study was firstly carried out against standard mixtures containing labeled and unlabeled PCDD/PCDF and a certified reference material (fly ash CRM 490). Next, a comparison between a conventional cleanup procedure and the new automated system for PCDD/PCDF analysis in environmental samples such as flue gas emissions, fly ashes, sludges, ambient air and soils was also made. The suitability of the system was finally assessed from the participation in an interlaboratory exercise. Owing to its capability to successfully perform the sample cleanup the Power-Prep apparatus is an alternative to the conventional methods.     

Optimization of Soxtec Extraction for the Determination of Polychlorinated Biphenyls (PCBs) in Mussel and Comparison with Soxhlet Extraction,Accelerated Solvent Extraction,and Microwave Assisted Extraction

An on-line Soxtec extraction and cleanup method is optimized for PCBs determination in mussel samples. Soxtec extraction conditions have been optimized using two factorial designs. Optimized extraction parameters were sample weight, anhydrous sodium sulfate weight, solvent volume, alumina weight, and boiling and rinsing times. The results suggest that all PCBs congeners extracted by Soxtec appeared statistically affected by solvent volume. Soxtec quantitative recoveries (8– ?115%) were achieved for all PCBs and method precision (RSD <12%) was satisfactory. The optimized method is compared with three different applied extraction methods, Soxhlet, accelerated solvent extraction, and microwave-assisted extraction. This latter presents the cleanup step on column or assisted by polypropylene membranes. The extraction effectiveness of the four different applied extraction methods for the determination of PCBs in mussel was similar.     

Determination of fumonisins B1 and B2 in various maize products by a combined SAX + C18 column and immunoaffinity column

Fumonisins B1 and B2 were determined in 42 samples of different maize products from the Swedish market by 2 different methods based on cleanup steps using an immunoaffinity column and a combination of SAX + C18 columns, respectively. A simple "precipitation step" was included before the samples were added to the main column(s), giving less column clogging, fewer interfering peaks, and better recoveries for the different sample matrixes. Recovery, repeatability, and results from the survey showed comparable results with the methods. The limit of detection for both methods was 5 micrograms/kg for fumonisin B1 and 10 micrograms/kg for fumonisin B2. All 7 maize chips analyzed and 6 of 8 popcorn samples contained fumonisins (B1 + B2) with averages of 180 and 115 micrograms/kg, respectively. All other samples except a maize flour sample contained little or no fumonisins.     

The use of turbulent flow chromatography and the isocratic focusing effect to achieve on-line cleanup and concentration of neat biological samples for low-level metabolite analysis

The use of turbulent flow chromatography in conjunction with column switching isocratic focusing was used to perform on-line sample cleanup and concentration of neat rat plasma for the identification of low-level metabolites. The concentration was achieved by focusing multiple injections, which were cleaned by a turbulent flow column, onto an analytical column prior to elution into the mass spectrometer. In addition, the first application of turbulent flow chromatography for on-line sample cleanup of neat bile samples is reported. The on-line cleanup and concentration method extracts and concentrates a sample 20-fold in 1 h, and is completely automated.     

On-capillary sample cleanup method for the electrophoretic determination of carbohydrates in juice samples

On many occasions, sample treatment is a critical step in electrophoretic analysis. As an alternative to batch procedures, in this work, a new strategy is presented with a view to develop an on-capillary sample cleanup method. This strategy is based on the partial filling of the capillary with carboxylated single-walled carbon nanotube (c-SWNT). The nanoparticles retain interferences from the matrix allowing the determination and quantification of carbohydrates (viz glucose, maltose and fructose). The precision of the method for the analysis of real samples ranged from 5.3 to 6.4%. The proposed method was compared with a method based on a batch filtration of the juice sample through diatomaceous earth and further electrophoretic determination. This method was also validated in this work. The RSD for this other method ranged from 5.1 to 6%. The results obtained by both methods were statistically comparable demonstrating the accuracy of the proposed methods and their effectiveness. Electrophoretic separation of carbohydrates was achieved using 200 mM borate solution as a buffer at pH 9.5 and applying 15 kV. During separation, the capillary temperature was kept constant at 40 degrees C. For the on-capillary cleanup method, a solution containing 50 mg/L of c-SWNTs prepared in 300 mM borate solution at pH 9.5 was introduced for 60 s into the capillary just before sample introduction. For the electrophoretic analysis of samples cleaned in batch with diatomaceous earth, it is also recommended to introduce into the capillary, just before the sample, a 300 mM borate solution as it enhances the sensitivity and electrophoretic resolution.     

Increased sample throughput in HPLC using sample switching

Summary Column switching methods are described which demonstrate an alternative approach to the reduction of analytical time in HPLC. Although most methods use a combination of techniques, it has been possible to group them into major categories involving column cleanup, sample cleanup, multicolumn methods and boxcar chromatography. Presented at the 15th International Symposium on Chromatography, Nürnberg, October 1984     

Method development of combining pressurized liquid extraction and off-line HPLC fractionation with a porous graphite carbon column for the analysis of polychlorinated dibenzo-p-dioxins and dibenzofurans (PCDD/Fs) in environmental samples

A method was developed for analysis of PCDD/Fs in fly ash and soil samples by using the combination of pressurized liquid extraction (PLE) and off-line HPLC fractionation with a porous graphite carbon (PGC) column, followed by analysis using HRGC/HRMS. The samples were automatically extracted by PLE. A multi-layer silica column was used for the preliminary cleanup. Then off-line fractionation was applied for the separation of PCDD/Fs and the collected PCDD/Fs fraction was analyzed by HRGC/HRMS. The use of solvent back-flushing at 70°C successfully solved the carry-over problem of PGC column. The procedure of single extraction and cleanup provided advantages of high automation and significant reduction of solvent and time compared to conventional methods. The method was validated by certified materials of fly ash and industrial sandy soil, and applied for the analysis of fly ash samples collected from three two-ton medical waste incinerators in Beijing and one farm soil sample collected in the vicinity of the incinerators.     

Development of a simultaneous extraction and cleanup method for pyrethroid pesticides from indoor house dust samples

An efficient and reliable analytical method was developed for the sensitive and selective quantification of pyrethroid pesticides (PYRs) in house dust samples. The method is based on selective pressurized liquid extraction (SPLE) of the dust-bound PYRs into dichloromethane (DCM) with analysis by gas chromatography/mass spectrometry. Various adsorbents and combinations of extraction solvents and temperatures were evaluated to achieve a high-throughput sample preparation that eliminates the post-extraction cleanup step. The final method used sulfuric acid-impregnated silica (acid silica) and neutral silica together in the extraction cell with the dust sample to provide both extraction and cleanup simultaneously. The optimal ratio of dust/acid silica/silica was 1:0.8:8. The extraction was performed at 2000 psi, at 100 °C with DCM for 5 min in three cycles. Method precision and accuracy were evaluated by the analysis of triplicate aliquots of the dust samples and the samples fortified with the target PYRs. The accuracy measured as the recoveries of the PYRs in the fortified samples ranged from 85% to 120%. The precision measured as the relative standard deviation of replicate samples was within ±25%. The SPLE method was applied to 20 house dust samples collected from households that participated in two field studies regarding exposures to pesticides and other pollutants. Similar concentrations of target PYRs were obtained for the SPLE and a stepwise extraction/cleanup procedure. The SPLE procedure reduces organic solvent consumption and increases the sample throughput when compared with a traditional stepwise extraction and cleanup procedure. This study demonstrates that the SPLE procedure can be applied to complex dust matrices for analysis of PYRs for large scale exposure or environmental monitoring studies.     

Coupling HPLC to GC: why? How? With what instrumentation?

Coupling LC to GC alleviates sample preparation in the sense of preseparation, cleanup, or enrichment and replaces conventional methods such as column liquid chromatography, enrichment by or filtration through sample preparation tubes, preparative thin-layer chromatography, or liquid-liquid partitioning. LC is more efficient in separation power, more rapid, and allows fully automatic integration of sample preparation into GC. Advantages are discussed for selected applications. The transfer techniques, as well as some key requirements for an LC-GC instrument, are briefly summarized.     

Development and validation of a direct plasma injection LC-MS method for YM087 and YM440 and metabolites in human plasma

Summary A fully automated, direct plasma-injection technique using an LC coupled to a quadrupole mass spectrometric detector with an on-line, sample clean-up procedure for two new pharmaceutical products, YM087 and YM440, has been developed. Plasma samples containing YM440 were mixed with internal standard or plasma containing YM087 and were injected into a chromatographic system based on two coupled columns. An extraction column packed with alkyl-diol-silica (ADS) was used for online sample cleanup. Using a back-flush technique analytes were subsequently transferred to an analytical column, for separation. Detection was based on tandem mass spectrometry either in electronspray or in APCI mode. Despite the relatively small volumes of plasma injected, reasonably low limits of quantitation were achieved. Validation of both assays was performed using guidelines concerning method validation. All parameters studied were within acceptance criteria. The methods were successfully applied to clinical pharmacokinetic studies.     

On-line sample stacking of peptides in capillary electrophoresis for the study of prebiotic reactions between α,α-dialkylated amino acids and amino acid N-carboxyanhydrides

The reaction between α,α-dialkylated amino acids and amino acid N-carboxyanhydrides is slow leading to low concentrations of products (peptides). The detection by capillary electrophoresis of the analytes contained in such samples is therefore a challenging issue. In this work, on-line sample pre-concentration methods based on field-amplified sample stacking have been implemented and compared. Because of the high ionic strength present in the sample matrix, samples were diluted with an organic solvent prior to analysis to decrease the sample conductivity. Different modes of sample injection (field amplified sample injection (FASI), hydrodynamic normal sample stacking (NSS) or large volume sample stacking (LVSS)) were compared. Pre-concentration factors of 20 for FASI, about 30–40 for NSS and 60 for LVSS were obtained for the analysis of (l,l) dipeptide of valine in a large excess of isovaline and 0.2 M of ionic strength. For LVSS application and resolution optimisation, a new non-covalent coating based on the partial modification of the capillary surface was used to tune the electroosmotic flow magnitude and to pump the sample matrix out of the capillary. This on-line sample pre-concentration step allowed confirming that oligopeptides including α,α-dialkylated amino acids are formed during the reaction between α,α-dialkylated amino acids and N-carboxyanhydride amino acids.     

Proteomic profiling of human urinary proteome using nano-high performance liquid chromatography/electrospray ionization tandem mass spectrometry

Urine, a blood filtrate produced by the urinary system, is an ideal bio-sample and a rich source of biomarkers for diagnostic information. Many components in urine are useful in clinical diagnosis, and urinary proteins can be strong indication for many diseases such as proteinuria, kidney, bladder and urinary tract diseases. To enhance our understanding of urinary proteome, the urine proteins were prepared by different sample cleanup preparation methods and identified by nano-high performance liquid chromatography electrospray ionization tandem mass spectrometry followed by peptide fragmentation pattern. The experimental results demonstrated that a total of 2283 peptides, corresponding to 311 unique proteins, were identified from human urine samples, in which 104 proteins with higher confidence levels. The present study was designed to establish optimal techniques to create a proteomic map of normal urinary proteins. Also, a discussion of novel approaches to urine protein cleanup and constituents is given.     

The role of column switching in analysing complex samples

Our objective in using column switching is primarily to achieve the desired separation in the minimum analysis time. Complimentary to this aim is the need for sample and column cleanup followed by column re-equilibration. Finally, all operations should be capable of automation. Fundamental to column switching methodology is the concept of Zone cutting, where part of the chromatogram is transferred to another column. This forms the basis of sample cleanup and is a very versatile and powerful methods. Multiple zone cutting is also possible to further increase to scope of cleanup or to minimise analysis time. Zone cutting is also complimentary to the techniques of trace enrichment and recycling. Examples will be given involving the use of these techniques in the analysis of complex matrices such as urine, plant extracts, wine and serum. The latter will be used to propose a novel approach to the quantitative analysis of anti-convulsants in serum using hexobarbital as internal standard.     

Development of new cleanup method of polychlorinated dibenzo-p-dioxins/dibenzofurans in fish by freezing-lipid filtration

Freezing-lipid filtration as a new method has been developed for the rapid determination of polychlorinated dibenzo-p-dioxins/dibenzofurans (PCDDs/Fs) in biological samples. This method can effectively reduce the time of sample pretreatment, labor and amount of solvents compared with conventional methods. By freezing-lipid filtration procedure, about 90% of lipids in extract could be removed without any significant loss of PCDD/Fs. For further cleanup of extracts after freezing-lipid filtration, automatic parallel LC columns including silica gel, alumina and carbon columns were applied. During automatic parallel LC columns cleanup, most of co-extracted interferences such as residue lipids and fatty acids could be eliminated and dioxins could be separated from many other dioxin-like congeners such as polychlorinated biphenyls by this procedure. The extracts after cleanup were analyzed by high-resolution gas chromatography (HRGC)/high-resolution mass spectrometry (HRMS) using an isotope dilution method. The average recoveries and relative standard deviation (R.S.D.) of 17 native congeners in the spiked fish samples at 8-80 pg/g (n = 3) were ranged between 85.3 and 117.2% and 5.7-20.3%, respectively.     

Optimization and validation of organochlorine compounds in adipose tissue by SPE‐gas chromatography

Scientific evidence has shown an association between organochlorine compounds (OCC) exposure and human health hazards. Concerning this, OCC detection in human adipose samples has to be considered a public health priority. This study evaluated the efficacy of various solid‐phase extraction (SPE) and cleanup methods for OCC determination in human adipose tissue. Octadecylsilyl endcapped (C₁₈‐E), benzenesulfonic acid modified silica cation exchanger (SA), poly(styrene‐divinylbenzene (EN) and EN/RP₁₈ SPE sorbents were evaluated. The relative sample cleanup provided by these SPE columns was evaluated using gas chromatography with electron capture detection (GC–ECD). The C₁₈‐E columns with strong homogenization were found to provide the most effective cleanup, removing the greatest amount of interfering substance, and simultaneously ensuring good analyte recoveries higher than 70%. Recoveries > 70% with standard deviations (SD) < 15% were obtained for all compounds under the selected conditions. Method detection limits were in the 0.003–0.009 mg/kg range. The positive samples were confirmed by gas chromatography coupled with tandem mass spectrometry (GC‐MS/MS). The highest percentage found of the OCC in real samples corresponded to HCB, o,p′‐DDT and methoxychlor, which were detected in 80 and 95% of samples analyzed respectively. Copyright © 2012 John Wiley & Sons, Ltd.     

Techniques and procedures for preparation of aquatic samples for chromatographic analyses

The measurement of low levels of organic compounds in environmental samples presents the researcher with a number of possible pathways to effectively obtain and analyze samples. Numerous sampling methods, sample preparation techniques, and extraction procedures are available. A number of different approaches to sampling strategy, isolation, concentration, cleanup and fractionation will be discussed. Objectives for collecting environmental samples differ from those for many other types of samples because reliable measurements at very low levels are frequently required. Often, specific analytes need to be measured at the μg/kg and even ng/kg levels in complex matrices. Advances in analytical methodology continue to lower the levels at which reliable measurements can be made. At these levels, many factors that are of little or no concern in other analytical measurements are of critical importance in influencing the outcome and reliability of environmental analyses. Analytical measurements are used for determining the composition and the quantities of analytes in the defined system at various concentration levels. Environmental analytical measurements provide data about the transportation and transformation of an environmental contraminant and for determination of its concentration in a sample.     

GC�CMS Determination of PAHs in Fish Samples Following Salting-out-Assisted Solvent Extraction-Gel Permeation Chromatography

A fast and effective sample cleanup procedure for the quantification of polycyclic aromatic hydrocarbons (PAHs) in fish samples is presented. The procedure involved extraction of fish samples using acetonitrile and cleanup by an automated gel-permeation chromatography (GPC) following liquid?Cliquid partition into n-hexane. The extracted samples were analyzed by gas chromatography-mass spectrometry (GC?CMS). Electron ionization was employed in a single analysis for the determination of PAHs in the selected ion monitoring mode. Three different solvents were studied for the extraction step: acetonitrile/n-hexane, methanol/n-hexane and acetone/n-hexane. The best solvent was found to be acetonitrile/n-hexane. The cleanup technique resulted in a good separation of analytes from co-extractive matrix compounds.     

Measurement of carnosine, homocarnosine and anserine by FASI capillary electrophoresis UV detection: applications on biological samples

A field amplified sample injection (FASI) capillary electrophoresis method with UV detection was developed for the separation and detection of carnosine-related peptides carnosine (Car), anserine (Ans) and homocarnosine (Hcar). The imidazole dipeptides were baseline-separated within 10 min by using 50 mmol/L Tris phosphate pH 2.2 as running buffer. The samples were diluted in water and directly injected on the capillary without complex cleanup and/or sample derivatization procedures. Using the electrokinetic injection, a sensitivity improvement of about 500-fold was achieved without any loss of separation efficiency if compared to the conventional sample injection. The detection limits for carnosine, anserine, and homocarnosine were between 0.4 and 0.5 nmol/L, thus improving of 10-100-fold the LOD of previous described methods based on laser induced fluorescence or chemiluminescence detection. This method has been applied to the analysis of homogenized rat tissue (heart, muscle and brain) and human cerebrospinal fluid (CSF).     

Determination of polycyclic aromatic hydrocarbons in environmental samples by high performance thin-layer chromatography and fluorescence scanning densitometry

High performance thin-layer chromatography (HPTLC) with fluorescence scanning densitometry was used for the quantitative determination of polycyclic aromatic hydrocarbons in the soluble organic fraction of air particulate samples. A method using normalized emission response ratios was developed to determine sample identity and to test for peak homogeneity. To preserve the high sample throughput of HPTLC, the two-point calibration method was used for quantitation. The principal advantages of HPTLC as a screening technique for environmental samples are its low cost, methodological simplicity, high sample throughput, and the ability to analyze crude samples with a minimum amount of sample cleanup.