Alka J.M. Horvat

Solid Phase Extraction and HPLC Determination of Veterinary Pharmaceuticals in Wastewater

This work focuses on the application of SPE-HPLC analysis of important veterinary pharmaceuticals from different classes in highly complex wastewater matrix. The pharmaceutical investigated included three sulfonamides (sulfamethazine, sulfadiazine and sulfaguanidine), a sulfonamide synergist (trimethoprim), a tetracycline (oxytetracycline), a fluoroquinolone (enrofloxacine) and a beta-lactame (penicillin G/procaine). The method involves pre-concentration and clean-up by solid phase extraction (SPE) using Oasis HLB extraction catridges. Final analysis of the selected pharmaceutical compounds was carried out by high-performance liquid chromatography (HPLC) coupled with diode array detector (DAD). Recoveries were ranged from 68.3 to 97.9% with relative standard deviation below 8.4%. Only for sulfaguanidine low recovery was obtained. Limits of quantification were in the range 1.5-100mug/L depending on pharmaceutical. The described method was applied to the determination of pharmaceuticals in wastewater samples from pharmaceutical industry.

Interactive Sorption of Metal Ions and Humic Acids onto Mineral Particles

The sorption of metal ions (Pb2+, Zn2+ and Cu2+) and soil humic acids (HA) from aqueous solutions onto mineral particles (sand, calcite and clay) was investigated using a batch equilibrium system. The sorption reactions in two- component systems (heavy metals-mineral particles and humic acids- mineral particles), as well as interactions in three-component system (heavy metals-humic acids-mineral particles) were examined. Results showed that the presence of humic acids, dissolved or bound onto mineral surfaces, considerably influenced the fixation of heavy metals. The various effects, depending on mineral type, humic concentration and specific metal-ion, were observed in three- component system. Sorption of Cu2+-ions on all minerals studied rapidly increased as the concentration of dissolved HA increased. The amount of Pb2+-ions sorbed on sand slightly decreased, while on kaolin increased between 15 and 20%. Sorption of Zn2+-ions on all minerals studied decreased at pH 4. At pH 5.5 the sorption of Zn2+-ions onto calcite decreased, while on kaolin and sand increased as a function of the humic acid concentration giving the curve with maximum at c(HA) = 2.5 mmol C L-1. At pH 6.5 sorption onto kaolin and sand increased. This effect occurs as a result of the conditional stability constant of Zn-HA complexes increasing at higher pH which in turn promotes the chelation of Zn2+-ions to mineral- bound humic substances. The enhanced sorption of metal ions from the aqueous phase in three-component systems is not only the result of mineral sorption of free metals but also the result of chelation with HA sorbed on the mineral surface.

Development and optimization of the SPE procedure for determination of pharmaceuticals in water samples by HPLC-diode array detection.

This paper focuses on the investigation of different types of SPE sorbents for the preconcentration of eight veterinary pharmaceuticals from water samples. The pharmaceuticals studied were sulfamethazine, sulfadiazine, sulfaguanidine, trimethoprim, oxytetracycline, enrofloxacin, norfloxacin and penicillin G/procaine. Five different SPE materials (Strata-X, Strata-X-C, Strata SDB-L, Strata C8 and Strata C18) from Phenomenex were compared with Oasis HLB with a view to obtaining the best cartridges for all pharmaceuticals investigated. Extraction efficiency was determined by HPLC with diode array detection (DAD). HPLC-DAD separation and quantification of the selected pharmaceuticals were carried out under gradient elution by a binary mixture of 0.01 M oxalic acid and ACN based on cyano modified column (LiChrosphere 100 CN) from Merck. Strata-X provided the best results in the preconcentration of 100 mL water samples, yielding average pharmaceutical recoveries of higher than 90%, except for sulfaguanidine (76.1%). The developed Strata-X-HLPC-DAD method was validated and applied, for the efficient investigation of reverse osmosis/nanofiltration membranes and for the removal of these eight pharmaceuticals from the production wastewater samples. NF90 and XLE membranes were shown to be the best for the rejection of all investigated pharmaceuticals.

SPE-HPLC/DAD determination of trimethoprim, oxytetracycline and enrofloxacin in water samples

In this paper high-performance liquid chromatography with diode array UV detection (HPLC/DAD) after SPE sample pretreatment for simultaneous analysis of pharmaceuticals from three different classes: enrofloxacin, oxytetracycline and trimethoprim, has been developed, optimised and validated. The chromatographic separation was developed on spiked wellspring water samples and checked on model wastewater samples of veterinary pharmaceuticals before and after RO/NF membrane treatment (feed and permeate streams) and on process wastewaters of industrial origin. Chromatographic separation was performed on Varian ProStar HPLC/DAD with C-18 column (Microsorb-MV 100 C18, 150 × 4.6 mm; 5 µm, Varian, USA). Detection and quantification was performed at 254 nm. The best separation was achieved with mobile phase 0.5% formic acid and 1% trifluoroacetic acid in 0.05 M ammonium acetate-methanol, 70 + 30, (v/v) after extraction procedure on polystyrenedivinylbenzene Varian Empore extraction disks. The extraction efficiency was checked by recovery experiments.

Comparison of Different Solid-Phase Extraction Materials for Sample Preparation in the Analysis of Veterinary Drugs in Water Samples

This paper focuses on the study of different types of SPE material that can be used for preconcentration of eight pharmaceuticals from water samples. The compounds studied were enrofloxacine, norfloxacine, Oxytetracycline, trimethoprim, sulfamethazine, sulfadiazine, sulfaguanidine, and penicillin G/procaine. Cartridges were tested on spiked water samples and extraction efficiency was determined by thin-layer chromatography (TLC) CN-modified chromatographic plates with 0.05 m H2C2O4-methanol, 81 + 19, as mobile phase. Strata-X cartridges were proved to be the best type of SPE material for this group of pharmaceutical compounds. For this reason an SPE—TLC method with Strata-X cartridges and HPTLC plates was validated. The method has been applied to the determination of pharmaceutical products in production wastewater samples from the pharmaceutical industry.

Solid-phase extraction and TLC quantification of enrofloxacin, oxytetracycline, and trimethoprim in wastewater

Quantitative determination of the antibiotics enrofloxacin, oxytetracycline, and trimethoprim in aquatic samples is reported. The method involves solid-phase extraction (SPE) and preconcentration of the antibiotics, separation by thin-layer chromatography (TLC) and quantification by video densitometry. TLC separation was performed on HPTLC CN F254s plates with H2C2O4-methanol as mobile phase. Spots were detected and quantified at X - 254 nm by videodensitometry. Limits of detection (LOD) and limits of quantification (LOQ) for TLC determination were calculated. The method was evaluated for spiked water samples. Antibiotics were extracted by solid-phase extraction (SPE) on a polystyrene-divinyl-benzene (SDB) Empore extraction disk. The extraction efficiency was checked by recovery experiments.

Determination of sulfonamides and trimethoprim in spiked water samples by solid-phase extraction and thin-layer chromatography

This paper describes a method for separation and quantification of a mixture of antibiotics extracted from spiked water samples. The method involves SPE of the analytes from water then analysis of the extract by TLC. Excellent separation of sulfadimidine, sulfadiazine, sulfaguanidine, and trimethoprim (TMP) was achieved by HPTLC on silica gel F254 plates with chloroform-methanol, 89 + 11, as mobile phase. Videodensitometric quantification was validated for linearity, precision, limit of detection, and limit of quantification. Limit of detection (LOD) was 0.05 µg per spot for sulfadimidine, sulfadiazine, and sulfaguanidine, and 0.1 µg per spot for TMP. Limit of quantification (LOQ) was 0.1 µg per spot for sulfadimidine, sulfadiazine, and sulfaguanidine, and 0.2 µg per spot for TMP. The TLC method was tested on extracts obtained, by use of solid-phase extraction, from spiked water samples. The best recovery of these antibiotics was achieved by use of HLB cartridges and elution with acetonitrile. Apparent recoveries were 87.1 ± 8.4 for sulfadiazine, 93.1 ± 6.4 for sulfadimidine, 16.1 ± 7.2 for sulfaguanidine, and 108.7 ± 23.7 for trimethoprim.

Study of MCPA and MCPP herbicides mobility in soils from North-West Croatia as affected by presence of fertilizers

The mobility of acid herbicide (4‐chloro‐2‐methylphenoxy)acetic acid [MCPA] and 2‐(4‐chloro‐2‐methylphenoxy)propionic acid [MCPA] in soils of North‐West Croatia has been studied by soil thin‐layer chromatography (STLC). Mobility of MPCA and MCPP was influenced by the change in concentration of soluble salts and the effect of mineral composition of the system studied, i.e. content of kaolin and sand in soil thin layer. The objective of this work was also to investigate how the mobility of phenoxy herbicides MCPA and MCPP is altered by the presence of fertilizers when both coexist in soil as a result of human activity. It has been found that mobility of acidic herbicides increases with application of fertilizers especially on soil with low clay and low organic matter content.

Use of a genetic algorithm to optimize TLC separation

A method for optimization of a TLC separation based on use of a genetic algorithm is described. The procedure was tested by optimization of the reversed-phase HPTLC separation of a mixture of six pesticides and satisfactory optimum results were obtained. The performance of the genetic algorithm was tested by measurement of the number of generations, the population size, the mutation probability, and the crossover probability. Three separation criteria (MRF, R* and R**) were examined as fitness functions. The genetic algorithm was compared with the simplex method.

TLC separation and identification of heavy metals present in cotton material

Optimization of the separation and identification of heavy metals present in cotton material has been performed by TLC-densitome-try after microwave digestion of cotton samples. The best separation was achieved on precoated microcrystalline cellulose layers with acetonitrile-conc. HCl-water as mobile phase. Optimization of the composition of the ternary mobile phase was achieved by use of experimental design software. Plates were visualized with quercetin-dimethylglyoxime-NH3 reagent. A highly sensitive CCD color video camera was used to capture the chromatograms under white light.