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.     

Porous graphitic carbon chromatography/tandem mass spectrometric determination of cytarabine in mouse plasma

A high-performance liquid chromatography (HPLC) system using a porous graphitic carbon (PGC) stationary phase interfaced with an electrospray ionization (ESI) source and a tandem mass spectrometer (MS/MS) for the analysis of cytarabine (ara-C) in mouse plasma samples has been developed in support of a pharmacodynamic study. The graphitized carbon column was adopted for the separation of ara-C and endogenous peaks from mouse plasma samples under the reversed-phase phase mode in liquid chromatography. The retention characteristics of the PGC column and the ionization efficiencies of all analytes based on the experimental factors such as the composition of mobile phases were investigated. The potential of ionization suppression resulting from the endogenous biological matrices on the PGC column during HPLC/ESI-MS/MS was investigated using post-column infusion. The concentrations of ara-C in mouse plasma obtained by using PGC-HPLC/MS/MS and ion-pairing HPLC/MS/MS were found to be in good agreement in terms of analytical accuracy.     

Rapid analysis of triazolopyrimidine sulfoanilide herbicides in waters and soils by high-performance liquid chromatography with UV detection using a C18 monolithic column

In this work, the simultaneous analysis of five triazolopyrimidine sulfoanilide herbicides (flumetsulam, florasulam, metosulam, cloransulam-methyl, and diclosulam) by HPLC using UV detection and a C18 monolithic column is proposed. The mobile phase which was composed of ACN, water, and formic acid was pumped at a high flow rate (5 mmL/min) providing an analysis time of all the compounds in less than 2.3 min. The LODs were in the low microg/L range (i.e. between 60 microg/L for flumetsulam and 90 microg/L for florasulam) and the calibration curves showed good linearity (R2 > 0.9949). The method was applied to the analysis of these compounds in spiked mineral and tap waters and soils after an SPE preconcentration procedure using C18 cartridges. Mean recovery values ranged between 35 and 110% for water samples providing LODs of the whole procedure in the low ng/L level, down to 280 ng/L, and between 77 and 92% for soil samples with LODs down to 9.38 microg/kg. This is the first time that this family of pesticides is simultaneously analyzed in both types of samples by HPLC and also using a monolithic column.     

High-performance liquid chromatography-fluorescence determination of dinitropyrenes in soil after column chromatographic clean-up and on-line reduction.

In order to quantify 1,3-dinitropyrene (DNP), 1,6-DNP and 1,8-DNP in soil, we developed an efficient clean-up procedure and a sensitive determination method using fluorescence detection. DNP isomers were efficiently cleaned by three stages of fractionation, i.e., a silica gel open column chromatography using stepwise elution and two further purification steps by high-performance liquid chromatography (PPLC) using a monomeric-type octadecylsilyl (ODS) column and a polymeric-type ODS column. The recoveries of DNPs during the whole clean-up process were 94% or more. The fraction corresponding to DNPs was injected into an analytical polymeric-type ODS column for HPLC to separate DNP isomers. The effluent from the analytical ODS column was directly introduced to a catalyst column, which was packed with 5 microns alumina coated with platinum and rhodium (Pt-Rh), in order to reduce DNPs to diamino compounds, and then the fluorescence of diaminopyrenes was detected. The immediate detection of diaminopyrene isomers after on-line reduction afforded a sensitive detection of DNP isomers. The detection limits for DNPs were in the range of 0.7 to 4 pg. These developed methods were applied to four soil samples collected at parks in residential areas.     

Pyraflufen-ethyl residues in soil by solid phase extraction and high-performance liquid chromatography with UV detection.

Solid-phase extraction (SPE) procedure for cleanup followed by HPLC-UV method has been investigated for the determination of pyraflufen-ethyl residues in soil. The pesticide is extracted from the sample with acetone-water (80:20, v/v) and the extract is loaded onto an octadecyl (C(18)) column. The pesticide is eluted with acetonitrile and determined by HPLC with a UV detector. Using an acetone-water extraction followed by a C(18) cleanup, this method is characterized by recovery >90.1%, precision <5.8% RSD and sensitivity of 0.01 mg/kg. The proposed method has been successfully employed for the determination of the degradation dynamics of pyraflufen-ethyl in four agricultural soil samples under laboratory conditions.     

On-line redox derivatization liquid chromatography using double separation columns and one derivatization unit

A new on-line redox derivatization technique using double separation columns and one redox derivatization unit was presented for enhancement of separation selectivity of HPLC. This on-line redox derivatization HPLC system consisted of two separation columns and one redox derivatization unit placed between them. The redox reaction proceeds in the derivatization unit so that an analyte compound migrates as its original form in the first column, while as its oxidized or reduced form in the second column. The retention of the analytes is controlled by the lengths of the two separation columns in this system. We adopted a small column packed with porous graphitic carbon (PGC) as a redox derivatization unit and two C18 silica columns treated with hexadecyltrimethylammonium chloride as separation columns. The redox activity of PGC and the efficiency of the on-line redox derivatization HPLC system for enhancement of separation selectivity were investigated using EDTA complexes of some metal ions. Original untreated PGC and PGC treated with hydrogen peroxide completely oxidized Co(II)-EDTA and converted it to Co(III)-EDTA, while the other metal complexes eluted as their original oxidation states throughout the system. Selective separation and determination of cobalt in a reference copper alloy by the developed method were demonstrated.     

Interference of the electrospray voltage on chromatographic separations using porous graphitic carbon columns

The electrospray ionization (ESI) voltage is shown to interfere with liquid chromatographic separations performed with packed porous graphitic carbon (PGC) capillary columns. This interference is ascribed to the presence of an electric field over the conductive column in the absence of an earth point between the column and the ESI emitter. The current evolved alters the chromatographic behavior of the catecholamine metabolite 3-O-methyl-DOPA significantly, as both peak splitting and a dramatic decrease in the retention time were observed. Furthermore, the response from the mass spectrometer was decreased by 33% at the same time. A related compound, tyrosine, exhibited decreased retention times but no peak splitting, whereas no shifts in the retention times (or peak splitting) were seen for the less retained dopamine and noradrenaline. When the current through the PGC column was eliminated by the use of an earth point between the column and the ESI emitter, the chromatographic behavior of the column was found to return slowly to normal after hours of equilibration with 60 : 40 (v/v) methanol-ammonium formate buffer of pH 2.9. The behavior of the PGC column with and without the earth point was found to be highly reproducible during a period of 1 month. We propose that the effect of the ESI voltage on the chromatographic behavior of the PGC column is due to associated redox reactions affecting both the PGC particles and the analytes. It is concluded that (for analytical reasons), care should be taken to ensure that no current is flowing through the chromatographic system when interfacing PGC columns, and conducting parts in general, to ESI mass spectrometry.     

Molecularly imprinted polymer‐based solid phase clean‐up for analysis of ochratoxin A in beer,red wine,and grape juice

A simple, reliable, and low‐cost method based on molecularly imprinted polymer as a selective sorbent of SPE was proposed for the determination of ochratoxin A (OTA) in beer, red wine, and grape juice by HPLC coupled with fluorescence detection (HPLC‐FLD). Samples were diluted with water and cleaned up with an AFFINIMIP® SPE OTA column. After washing and eluting, the analyte was analyzed by HPLC‐FLD. Under the optimized conditions, LOD and LOQ for OTA were 0.025 and 0.08 ng/mL, respectively. The recoveries of OTA from beer, red wine, and grape spiked at 0.1, 2, and 5 ng/mL ranged from 91.6 to 101.7%. Furthermore, after a simple regenerated procedure, the molecularly imprinted polymer based SPE column could be reused at least 14 times to achieve more than 80% recoveries of OTA in real samples. The developed method was applied to the detection of 30 beer, red wine, and grape juice samples and only four samples were contaminated by OTA with levels below the legal limits.     

An ion-pairing liquid chromatography/tandem mass spectrometric method for the determination of cytarabine in mouse plasma

An ion-pairing high-performance liquid chromatographic (IP-HPLC) system interfaced with an atmospheric pressure chemical ionization (APCI) source and a tandem mass spectrometer (MS/MS) with minimal sample preparation was developed for the determination of cytarabine (ara-C), a very hydrophilic anticancer drug, in mouse plasma. A conventional reversed-phase chromatographic column in combination with two ion-pairing reagents was adapted for retention and separation of ara-C from the endogenous interferences in mouse plasma. The effects of the experimental conditions such as the fraction of ion-pairing reagents and organic solvents in the mobile phase on the chromatographic performance and the ionization efficiency of ara-C were investigated. The potential of ionization suppression resulting from the endogenous biological materials on the IP-HPLC/MS/MS method was evaluated using the post-column infusion technique. Furthermore, the feasibility of the proposed IP-HPLC/MS/MS procedure for analysis of ara-C in the mouse plasma was demonstrated by comparison with those obtained by the porous graphite carbon column (PGC) HPLC/MS/MS method.     

In-tube solid-phase microextraction with poly(methacrylic acid-ethylene glycol dimethacrylate) monolithic capillary for direct high-performance liquid chromatographic determination of ketamine in urine samples

Ketamine was used for anaesthesia originally but has emerged as an abused drug in recent years. The prevalence of ketamine abuse demands a direct and rapid determination method. It is known that in-tube solid phase microextraction (in-tube SPME) can perform extraction with a capillary linked directly to a HPLC system, providing an automated and accurate extraction procedure. In this paper, an in-tube SPME coupled to HPLC method was developed for the determination of ketamine in urine samples with a poly(methacrylic acid-ethylene glycol dimethacrylate) monolithic capillary column as the extraction phase, which is expected to provide higher extraction efficiency than open tubular capillaries. After optimizing the extraction conditions, ketamine was extracted directly from urine samples in a wide dynamic linear range of 50-10,000 ng mL(-1), with the detection limit obtained as 6.4 ng mL(-1). The intra-day and inter-day precision for the method was 1.6% and 1.7%, respectively. The urine samples from suspect addicts have been successfully analyzed within 20 min. The re-usability of the monolithic column was also confirmed as no decrease of the extraction efficiency was shown after urine extraction.     

固相萃取-高效液相色谱法同时测定水中的16种苯脲除草剂(英文)

 建立了固相萃取 高效液相色谱 (SPE HPLC)同时测定水中 16种苯脲除草剂的方法。HPLC采用Lichrospher 10 0RP 18e柱 ,紫外检测波长为 2 40nm ,流动相为乙腈水溶液 ,流速为 1mL/min ,采用梯度洗脱方式。HPLC分析时间少于 2 0min。水中的除草剂用C18柱固相萃取富集 10 0 0倍。在优化的条件下 ,各成分的添加回收率为 87 8%～ 10 3 7%。     

Determination of biotin by high-performance liquid chromatography in infant formula, medical nutritional products, and vitamin premixes

A solid-phase extraction sample preparation procedure was developed for use with a high-performance liquid chromatography (HPLC) method for biotin analysis. The HPLC method used a reversed-phase C18 column; chromatography run time was 8.5 min. After eluting from the column, biotin went through postcolumn reaction to form a conjugate with streptavidin-fluorescein isothiocyanate, which was then detected by a fluorescence detector. This method was tested with infant formula, medical nutritional products, and vitamin premix samples.     

Determination of the herbicide metribuzin and its major conversion products in soil by micellar electrokinetic chromatography

In this paper, a multiresidue method for the analysis in soils of metribuzin (M) and its major conversion products, deaminometribuzin (DA), diketometribuzin (DK) and deaminodiketometribuzin (DADK) is developed. Considering the neutral and charged nature of the molecules, micellar electrokinetic chromatography (MEKC) is a very efficient method for the separation of these compounds, providing high efficiency and short analysis times. Different electrophoretic parameters were studied to optimize the separation, such as the buffer pH and concentration, sodium dodecyl sulphate (SDS) concentration, injection conditions and applied voltage. Excellent separation of the studied compounds was achieved within about 7 min. Soil samples were previously extracted using methanol in an ultrasonic bath and then a SPE procedure was applied to pre-concentrate the analytes by passage through a LiChrolut EN sorbent column. Detection limits at the low microgkg(-1) level were obtained. The proposed method has been satisfactorily applied in soil samples showing recoveries ranging from 86.7% to 104.2% and represents a valuable alternative to high-performance liquid chromatography (HPLC).     

Liquid Chromatographic Analysis of Ciprofloxacin and Ciprofloxacin Metabolites in Body Fluids

Abstract

An isocratic HPLC assay procedure for analysis of ciprofloxacin and three metabolites was developed. The procedure requires only dilution of bile, saliva, and urine samples prior to reverse-phase chromatography on a polystyrene-divinylbenzene (PSDVB) column; analysis of serum samples requires a cleanup step on a PSDVB cartridge prior to chromatography. The dependence of chromatographic efficiency on flow rate and temperature was investigated and the accuracy, precision, selectivity, and sensitivity of the procedure were evaluated. The developed procedure was also compared to a modified version of a published ciprofloxacin procedure that requires an octadecyl-silane (ODS) column for chromatographic separation. Similar efficiency, precision, and accuracy were observed with both procedures and both were used for analysis of clinical samples. However, the procedures were used for different purposes. The PSDVB procedure, because of more favorable column selectivity, was used to assay ciprofloxacin and its metabolites in bile, urine and saliva samples. The ODS procedure, because of a simpler serum preparation step, was used t o assay ciprofloxacin in serum samples.     

Application of totally automated on-line sample clean up for prostanoid extraction and HPLC separation

Summary The aim of this study has been the evaluation of an automated system for on-line sample preparation using solid phase extraction and HPLC purification for the measurement of prostanoids in urine. We have established the optimum precolumn and column conditions for this analysis. The manual extraction —HPLC procedure furnishes lower recoveries and higher coefficients of variation than those obtained by the automated on-line procedure. The automated system has been applied to prostanoid analysis of human urine samples from subjects exposed to lead.     

Hydrazine determination in sludge samples by high-performance liquid chromatography

A relatively simple and cost-effective method utilizing HPLC with UV detection was developed to detect and quantify hydrazine in sludge samples. The method was developed primarily for sludge samples, but it can also be applicable to soil and other environmental samples. The hydrazines in the matrices were derivatized to hydrazones with benzaldehyde. The hydrazones were separated using HPLC with an RP C-18 column in an isocratic mode with methanol-water (95:5 v/v) and detected with UV detection at 313 nm. The detection limit (25 microL injection) for the method is 0.02 microg/mL of hydrazine.     

Online combination of reversed-phase/reversed-phase and porous graphitic carbon liquid chromatography for multicomponent separation of proteomics and glycoproteomics samples

In this paper, we describe an online combination of reversed‐phase/reversed‐phase (RP–RP) and porous graphitic carbon (PGC) liquid chromatography (LC) for multicomponent analysis of proteomics and glycoproteomics samples. The online RP–RP portion of this system provides comprehensive 2‐D peptide separation based on sequence hydrophobicity at pH 2 and 10. Hydrophilic components (e.g. glycans, glycopeptides) that are not retained by RP are automatically diverted downstream to a PGC column for further trapping and separation. Furthermore, the RP–RP/PGC system can provide simultaneous extension of the hydropathy range and peak capacity for analysis. Using an 11‐protein mixture, we found that the system could efficiently separate native peptides and released N‐glycans from a single sample. We evaluated the applicability of the system to the analysis of complex biological samples using 25 μg of the lysate of a human choriocarcinoma cell line (BeWo), confidently identifying a total of 1449 proteins from a single experiment and up to 1909 distinct proteins from technical triplicates. The PGC fraction increased the sequence coverage through the inclusion of additional hydrophilic sequences that accounted for up to 6.9% of the total identified peptides from the BeWo lysate, with apparent preference for the detection of hydrophilic motifs and proteins. In addition, RP–RP/PGC is applicable to the analysis of complex glycomics samples, as demonstrated by our analysis of a concanavalin A‐extracted glycoproteome from human serum; in total, 134 potentially N‐glycosylated serum proteins, 151 possible N‐glycosylation sites, and more than 40 possible N‐glycan structures recognized by concanavalin A were simultaneously detected.     

Optimization of extraction procedure and chromatographic separation of glyphosate, glufosinate and aminomethylphosphonic acid in soil

Analysing herbicides in soil is a complex issue that needs validation and optimization of existing methods. An extraction and analysis method was developed to assess concentrations of glyphosate, glufosinate and aminomethylphophonic acid (AMPA) in field soil samples. After testing extractions by accelerated solvent extraction and ultrasonic extraction, agitation was selected with the best recoveries. Water was preferred as solvent extraction because it resulted in a cleaner chromatogram with fewer impurities than was the case with alkaline solvents. Analysis was performed by FMOC pre-column derivatization followed by high-performance liquid chromatography (HPLC) on a 300 mm C(18) column which permitted enhanced separation and sensitivity than a 250 mm C(18) column and increased resistance than the NH(2) column for soil samples. This extraction and analysis method allowing a minimum of steps before the injection in the HPLC with fluorescence detection is efficient and sensitive for a clay-loamy soil with detection limits of 103 μg kg(-1) for glyphosate, 15 μg kg(-1) for glufosinate and 16 μg kg(-1) for AMPA in soil samples.     

Surfactant coated graphitic carbon based stationary phases for anion-exchange chromatography

Separations of common inorganic anions were carried out on three different surfactant coated media using carbonate/bicarbonate eluents with suppressed conductivity detection. Graphitic carbon columns (porous graphitic carbon and carbon-clad zirconia) packed with 3 microm particles have been converted into anion-exchange stationary phases by equilibration with the cationic surfactants: didodecyldimethylammonium bromide (DDAB); cetyltrimethylammonium bromide (CTAB); and cetylpyridinium chloride (CPC). Additionally, an ethylene-bridged silica column was studied with CPC coatings. Porous graphitic carbon (PGC) columns coated with DDAB exhibited pressure increases and loss of resolution at higher capacities. CPC coatings on PGC exhibited better repeatability and efficiencies of 5.0 x 10(4)plates/m. However, CPC coatings exhibited a 15% loss in retention factor with <1.2 x 10(3) column volumes on PGC. Conversely, the ethylene-bridged silica column showed complete failure in less than 8 h of use. As with PGC, carbon-clad zirconia coated with CPC showed an initial loss of capacity, but thereafter was stable for more than 1.7 x 10(3) column volumes (t(r) RSD<2%).     

New approach to large-volume injection in reversed-phase high performance liquid chromatography: determination of atrazine and hydroxyatrazine in soil samples

A well established method of direct injection of larger than conventional sample volumes ranging from 0.1 mL to 10 mL in HPLC is the injection valve method in which a loop of tubing is totally or partially filled with sample. Recent HPLC pumps have a flow-rate setting accuracy of +/- 1-2% over a flow-rate range from 0.1 mL/min to 10 mL/min and the flow stability is 0.2% or less. Quarternary low pressure gradient pumps are widely available and used, but all their hydraulic lines are seldom utilised. The idea of using one line of a common commercial HPLC quaternary low-pressure pump for direct on-column injection (pumping) of large sample volumes ranging from 1 mL to 100 mL was tested. This approach was evaluated during practical work on the development of an RP-HPLC method of determination of residual atrazine and hydroxyatrazine. In lysimetric environmental experiments hydroxyatrazine was formed in situ in a soil column by hydrolysis of atrazine. The results proved the applicability of this approach not only in experiments with model mixtures of analytes at microg/L levels in solutions. Analysis of 20 mL of soil leachates and extracts of soil samples containing atrazine and hydroxyatrazine at the 10 microg/kg level (in dry soil) revealed that good figures-of-merit were preserved, even in the presence of a large excess of humic substances.