Off-line Solid-phase Extraction Procedure Research Articles

Identification of the nitroaromatic explosives in post-blast samples by online solid phase extraction using molecularly imprinted silica sorbent coupled with reversed-phase chromatography

In a previous work, a molecularly imprinted silica (MIS) sorbent was synthesized for the selective extraction of nitroaromatic explosives from real samples. This MIS packed in a cartridge was used for an off-line solid phase extraction procedure mainly based on hydrophobic and π-π interactions. In this work, the MIS was packed in a precolumn to be connected online with a reversed-phase LC system and a diode array detector. For this, the chromatographic conditions were first studied to obtain the separation of 1,3-dinitrobenzene, 1,3,5-trinitrobenzene, 2,4-dinitrotoluene, 2,6-dinitrotoluene, 2,4,6-trinitrotoluene, and tetryl. An optimized procedure dedicated to the selective treatment of aqueous samples was then developed with the MIS for the simultaneous extraction of the nitroaromatic compounds commonly used as explosives. Finally, the four nitrotoluenes were selectively extracted and determined simultaneously with extraction recoveries higher than 90% using the online device composed of the MIS coupled with a diphenyl chromatographic column. The potential of this sorbent was highlighted by its use for the cleanup of simulated post-blast samples.

Validation of an on-line solid-phase extraction method coupled to liquid chromatography–tandem mass spectrometry detection for the determination of Indacaterol in human serum

Indacaterol has been recently approved in Europe for the treatment of chronic obstructive pulmonary disease (COPD). In the present study, we have developed and validated a rapid and sensitive on-line solid phase extraction (SPE) method coupled to liquid chromatography–tandem mass spectrometry (LC–MS/MS) detection for the determination of Indacaterol in human serum. The sample preparation involves the serum dilution with a 0.2% acetic acid solution prior to the on-line SPE on a mixed-mode cationic (MCX) polymer based sorbent. The samples were then eluted on a reversed phase column with a mobile phase made of acidified water and methanol and detection was performed by MS using electrospay ionization in positive mode. The analysis time between 2 samples was 7.0min. Standard curves were linear over the range of 10.0pg/mL (LLOQ) to 1000pg/mL with correlation coefficient (r2) greater than 0.990. The method specificity was demonstrated in six different batches of human serum. Intra-run and inter-run precision and accuracy within ±20% (at the LLOQ) and ±15% (other levels) were achieved during a 3-run validation for quality control samples (QCs). The stability at room temperature (38h) was determined and reported. In addition, the comparison between an off-line SPE procedure and our method gave equivalent results. The results of the present work demonstrated that our on-line SPE–LC–MS/MS method is rapid, sensitive, specific and could be applied to the quantitative analysis of Indacaterol in human serum samples. Our method effectively eliminated the tedious conditioning and rinsing steps associated with conventional off-line SPE and reduced the analysis time. The on-line SPE approach appears attractive for supporting the analysis of several hundreds of clinical samples.

Evaluating on-line solid-phase extraction coupled to liquid chromatography–ion trap mass spectrometry for reliable quantification and confirmation of several classes of antibiotics in urban wastewaters

This study provides an evaluation of on-line solid-phase extraction (SPE) and liquid chromatography (LC) in combination with ion trap (IT) mass spectrometry for the simultaneous routine analysis of 12 antibiotics belonging to multiple classes together with carbamazepine and propranolol in sewage treatment effluents. The on-line SPE step warranted high sensitivity and high sample throughput while IT mass detection provided high selectivity for confirmation of positive samples. A single extraction procedure resulted in recoveries ranging from 40% to 120%. Limits of detection were in the 1–46 ng/L range, which constitutes an improvement of a factor of 10 with respect to the off-line SPE procedure.

Comparison of a non-aqueous capillary electrophoresis method with high performance liquid chromatography for the determination of herbicides and metabolites in water samples

A method of capillary electrophoresis (CE) for the determination of triazine herbicides and some of their main metabolites in water samples has been developed. The proposed CE method includes an off-line solid-phase extraction (SPE) procedure with LiChrolut EN sorbent coupled to a non-aqueous capillary electrophoresis (NACE) separation with UV detection. The target compounds were the chloro-s-triazines simazine, atrazine, propazine; the methyltio-s-triazines ametryn and prometryn and three main derivatives from the atrazine degradation products; namely, deethylatrazine, deethylhydroxyatrazine and deisopropylhydroxyatrazine. The analytical characteristics of the CE method are reported. The repeatability of the method was studied considering the different steps of the method separately in order to determine the contributions of each step to the total variability of the method. The NACE-UV results are compared with those obtained with a high performance liquid chromatography with UV detection (HPLC-UV) method. The same off-line SPE procedure was applied to both techniques. The results obtained show that both methods afford the same results in the analysis of surface and drinking water samples, with a level of significance regarding the F- and t-tests greater than 0.05 in all the cases. The detection limits in surface water samples were in the 0.04–0.32 μg l −1 and 0.11–1.2 μg l −1 ranges for the NACE-UV and HPLC-UV methods, respectively. The recoveries (spiked/found) were significantly 100% in all cases.

Chlorinated Phenol Analysis Using Off-Line Solid-Phase Extraction and Capillary Electrophoresis Coupled with Amperometric Detection and a Boron-Doped Diamond Microelectrode

The analysis of chlorinated phenols (2-chlorophenol, 3-chlorophenol, 4-chlorophenol, 2,4-dichlorophenol, 2,4,6-trichlorophenol, pentachlorophenol) in river water was accomplished using off-line solid-phase extraction (SPE) and capillary electrophoresis coupled with electrochemical detection. A key to the sensitive, reproducible, and stable detection of these pollutants was the use of a boron-doped diamond microelectrode in the amperometric detection mode. An off-line SPE procedure was utilized to extract and preconcentrate the pollutants prior to separation and detection, with ENVI-Chrom P, a highly cross-linked styrene-divinylbenzene copolymer, being employed as the sorbent. Pollutant recoveries in the 95-100% range with relative standard deviations of 1-4% were achieved. The diamond microelectrode provided a low and stable background current with low peak-to-peak noise. The oxidative detection of the pollutants was accomplished at +1.05 V vs Ag/AgCl without the need for electrode pretreatment. The method was evaluated in terms of the linear dynamic range, sensitivity, limit of quantitation, response precision, and response stability. A reproducible electrode response was observed during multiple injections of the chlorinated phenol solutions with a relative standard deviation of < or =5.4%. Good electrode response stability was observed over many days of continuous use with no significant electrode deactivation or fouling. The separation efficiencies for all six pollutants were greater than 170,000 plates/m. The minimum concentration detectable for all six ranged from 0.02 to 0.2 ppb (S/N > or = 3) using a 250:1 preconcentration factor.

Simple solid-phase extraction method for determination of polychlorinated biphenyls and selected organochlorine pesticides in human serum

A simple off-line solid-phase extraction (SPE) method for isolation of polychlorinated biphenyls (PCBs) and selected organochlorine pesticides (OCPs) from human serum has been developed. The procedure includes denaturation of serum proteins by a mixture of water–1-propanol, application of the sample by aspiration twice repeatedly through the SPE column and elution with a mixture of n-hexane–dichlormethane. After final clean-up the compounds of interest were analysed by gas chromatography with micro-electron capture detection (GC–μECD). The recoveries achieved for PCB congeners using spiked porcine serum samples were 99–120% and for OCPs 88–115%. Relative standard deviations (RSD) ranged from 3 to 7%. The method was applied to real human serum samples and the recoveries of analytes in the serum were proportionally recalculated considering the recovery of the internal standard PCB-174. PCB-103 served as a syringe standard to correct volume of samples analysed. The aim of this study was to develop an effective off-line SPE procedure by optimization of existing SPE methods to supply laborious, solvent- and time-consuming liquid–liquid extraction (LLE) in routine analytical process.

Off-line solid-phase extraction procedure for the determination of phenyl and butyltin compounds from aqueous matrices followed by GC-FPD determination

An analytical methodlogy for the determination of organotin compounds (OTs) in aqueous matrices based on solid-phase extraction (SPE) followed by Grignard pentylation and gas chromatography-flame photometric detector (GC-FPD) determination was developed. Spiked OTs, mono-, di- and tributyltin (MBT, DBT and TBT); and mono-, di- and triphenyltin (MPhT, DPhT and TPhT) were pre-concentrated from aqueous samples as OT chlorides in two different sorbents. A macroporous copolymer containing either lipophilic divinylbenzene, hydrophilicN-vinylpyrrolidone or conventional hydrophobic octadecyl (C18) bonded silica were evaluated by using an automated off-line SPE system. Optimization of the SPE preconcentration included the presence of a complexing agent, sample pH, loading the sorbent with a complexing agent (tropolone), eluent type and volume, breakthrough volume and the sorbent mass. Recoveries of OTs in spiked water samples at 100 ng L−1 ranged from 70 to 90%. Detection limits for butyltin and phenyltin compounds ranged from 10 ng L−1 to 20 ng L−1. Automation of the SPE procedure provides a higher sample throughput in comparison with the use of conventional C18 disks. A new polymeric SPE sorbent evaluated provides higher recoveries, better sample capacities and higher reproducibility in comparison with conventional hydrophobic C18 silica cartridges, and also uses lower sorbent mass.

Solid phase extraction and HPLC determination of 9-benzyladenine and isomeric 9-(nitrobenzyl)adenines and their metabolic N 1-oxides present in microsomal incubates

9-Benzyladenine, 9-(2-nitrobenzyl)adenine, 9-(3-nitrobenzyl)adenine and 9-(4-nitrobenzyl)adenine were metabolized to 9-benzyladenine-N 1-oxide, 9-(2-nitrobenzyl)adenine-N 1-oxide, 9-(3-nitrobenzyl)adenine-N 1-oxide and 9-(4-nitrobenzyl)adenine-N 1-oxide, respectively, by animal hepatic microsomes. For the quantitative determination of the substrates and metabolites present in microsomal incubates, an off-line solid phase extraction procedure, using columns packed with C18 silica bonded phase, was developed. The extraction recovery for these 9-alkyladenines and their N 1-oxides was in the range of 92–101%. A reversed-phase HPLC method was established with an ODS column at a column temperature of 50°C. The mobile phase consisted of H 2O-MeOH-diethylamine (65:35:0.5, v/v/v), pH 6.8. The above analytes were monitored at 233 nm and the retention times of all analytes were within 6–14 min. The within-day coefficients of variation (CV) for the determinations were in an acceptable range. The biotransformation of BA and NBAs to N 1-oxides by hamster microsomes was determined under the experimental conditions employed.