Copolymer Sorbent Research Articles

Determination of phenolic compounds at low μg 1 −1 levels by various solid-phase extractions followed by liquid chromatography and diode-array detection

An off-line solid-phase extraction was carried out to determine thirteen phenolic compounds, which included eleven EPA priority phenols, using reversed-phase liquid chromatography and diode-array detection. Two different sorbents, carbon and a highly cross-linked styrene-divinylbenzene copolymer, were compared for the preconcentration process. To increase the retention of the most polar compounds, mainly phenol, tetrabutylammonium bromide was used as an ion-pair reagent in the extraction system. Better recoveries were obtained for the copolymer sorbent and the performance of the method was tested with tap and Ebro river water. Recoveries higher than 90% were obtained for all compounds when a 500-ml sample was preconcentrated using the optimum conditions found with the copolymer sorbent. The R.S.D. for a river water sample spiked at 1 μg l −1 was lower than 10% ( n = 4) and the detection limits were between 65 and 100 ng l −1.

Determination of carbaryl and some organophosphorus pesticides in drinking water using on-line liquid chromatographic preconcentration techniques

Reversed-phase high-performance liquid chromatography (HPLC) was adapted for the determination of trace concentrations of carbaryl and seven organophosphorus pesticides in drinking water. Between 100 and 300 ml of water sample is passed through a 1.5-cm precolumn, packed with C 18- bonded silica or styrene—divinylbenzene copolymer (PRP-1) sorbent at a flow-rate of 3 ml/min. The HPLC system is then switched to an acetonitrile—water gradient elution programme. The analytes that have been concentrated on the precolumn are eluted and separated on a 15-cm C 18 analytical column and are determined by measuring their UV absorption at 254 nm. This wavelength was selected as the optimum for the simultaneous determination of these pesticides. The preconcentration yields of the examined solutes obtained with the two types of precolunm are almost identical. Band broadening is avoided by a suitable choice of the C 18 precolumn and the analytical column. With 200 ml of tap water, the recoveries for most of the examined pesticides were ca. 90%, except for carbaryl (54%). The detection limits are in the range 0.03–0.2 μg/l.

Hydrolysed macroporous glycidyl methacrylate-ethylene dimethacrylate copolymer sorbent for size-exclusion high-performance liquid chromatography of synthetic polymers and biopolymers

Les groupes epoxy sont hydrolyses pour ameliorer leur hydrophilicite. Separation de proteines, de polystyrene

Comparison of octadecyl-bonded silica and styrene-divinylbenzene copolymer sorbents for trace enrichment purposes fundamental aspects II. Linear chromatographic behaviour of the extracting supports

Two reversed-phase LC systems were investigated by frontal analysis for the determination of linear chromatographic conditions, as defined according to the isotherm concept. The Partisil ODS-3 bonded silica and the PRP-1 polystyrene-divinylbenzene resin were used as stationary phases together withtrans-2-hexen-al as test solute and methanol-water mixtures as mobile phases. Particular attention was paid to the respective influence of the two main parameters which may cause sorbent overloading, that is, the capacity factor (k′) and the solute concentration in the mobile phase (Cm). Provided that k′Cm≤10−2 M, linear chromatographic behaviour was observed for both sorbents, the maximum capacities of which were found greater than 1mmolg−1.

Comparison of octadecyl-bonded silica and styrene—divinylbenzene copolymer sorbents for trace enrichment purposes : Fundamental aspects I. Calibration of the stationary phases in pure water

An octadecyl-bonded silica (Partisil ODS-3) and a styrene-divinylbenzene copolymer (PRP-1) with comparable particle sizes, average pore diameters and specific pore volumes were investigated for trace-enrichment purposes. The organic resin leads to systematically higher values of the logarithm of the capacity factor, log k′, whatever the composition of the methanol-water eluent and whatever the solute investigated. Lower retention differences were observed for two alcohols. Accordingly, the correlation of experimental log k′ values obtained for a given eluent composition with calculated hydrophobic log P coefficients leads to one regression line for the C 18 material and two lines (for hydroxylated and non-hydroxylated solutes respectively) for the organic resin. This also applies to the calibration graphs of log P with the weighted linearly extrapolated log k′ w values in pure water. A weaker affinity of the copolymer for hydroxylated compounds can generally account for all the experimental results.

Trace Enrichment and HPLC Analysis of Chlorophenols in Environmental Samples, Using Precolumn Sample Preconcentration and Electrochemical Detection

Abstract A HPLC method has been developed for trace analysis of chlorophenols in the 0.2–2 ppb range from spiked water samples. Simple liquid-liquid extraction followed by on-line preconcentration of total mono- and dichlorophenols has been performed using a divinylbenzene-styrene copolymeric sorbent (PRP1) as packing material for the precolumn. The chlorophenols have been eluted from the precolumn on an analytical column (5μm LiChrosorb RP-18, 12.5 cm × 4 mm) by use of a switching valve system followed by separation. Detection was carried out with an electrochemical detector. The linearity of the detector response has been proved over two orders of magnitude. The detection limit of chlorophenols by means of the electrochemical method is in the lower picogram range. The recoveries of the isomeric chlorophenols from spiked river water samples having initial concentrations of 2ppb are usually 70–90%. The procedure has been applied to drinking water and river water.

Preferential Interactions on Polystyrene Divinylbenzene Copolymeric Sorbents

Abstract The adsorption of picric acid, naphthalene-sulfonic acid, and toluenesulfonic acid onto a polystyrene divinylbenzene copolymeric sorbent in methanol-water systems at 25°C was studied by reverse-phase high performance liquid chromatography. The observed peak asymmetry and increase in capacity factor at high methanol concentrations in the mixture was attributed to preferential interactions of the solutes at the surface. The phenomena were not as pronounced for octadecyl silane bonded phases.

Automated liquid chromatographic analysis of the anti-tumorigenic drugs etoposide (VP 16-213) and teniposide (VM 26)

A method is described for the fully automated analysis of large numbers of 1–2 ml serum and plasma or urine samples containing the anti-tumorigenic drugs etoposide and teniposide and their aglycone. The blood samples are hydrolysed by a proteolytic enzyme, subtilisin A, prior to preconcentration on a small precolumn. The hydrolysis step serves both to release the strongly protein-bound drugs and to prevent clogging of the chromatographic system. On-line preconcentration is carried out with precolumns packed with PRP 1, a microparticulate diviylbenzene—styrene copolymeric sorbent. Chromatography takes place, after column switching, in a C 18/methanol—water system. After a post-column clean-up step using continous extraction with dichloroethane in an autoanalyzer system, native fluorescence of these analytes is used for detection of the drugs. Recovery of etoposide and teniposide from spiked serum and plasma samples was 100%. Calibration curves of etoposide and teniposide typically show correlation coefficients of 0.9994 over a two-to-three order linear range. The detection limit of etoposide is approx. 8 ng per sample. Repeatability was found to be excellent. Unattended overnight routine analysis is possible without any problems. This method, considering optimal sample through-put reliability and selectivity, competes favourably with existing techniques for the analysis of etoposide and teniposide.

Preconcentration and LC analysis of chlorophenols, using a styrene-divinyl-benzene copolymeric sorbent and photochemical reaction detection

A specific HPLC method has been developed for the trace analysis of lower chlorinated aromatic compounds. The method consists of an on-line preconcentration and a post-column reaction step. On-line preconcentration of mono- and dichlorophenols from aqueous samples has been performed using PRP1, a divinylbenzene-styrene copolymeric sorbent as packing material for both pre-and analytical column. Enrichment factors of over 300 were obtained compared to regular (100 μl) loop injections, even for the highly polar monochlorophenols. After reversed-phase separation, post-column photochemical dechlorination is carried out directly in the eluent stream, using a photochemical reactor. Upon dechlorination, fluorescent products are formed, which can be detected selectively. The resulting fluorescence signal shows a linear response to the quantity of solute present over 2 to 3 orders of magnitude (correlation coefficients: 0.990–0.98). For the mono- and dichlorophenols, the detection limit of the photoconversion method is in the lower nanogram range. The method is especially suitable for the analysis of complex matrices such as effluent water samples or biological fluids containing traces of the polar chloroaromatic compounds together with large amounts of other constituents, which interfere when using more general methods of detection like UV absorption. The potential of this technique for automation has been demonstrated by using a microprocessor-controlled column switching unit.