High-Efficiency Liquid Chromatography Using Sub-2 μm Columns at Elevated Temperature for the Analysis of Sulfonamides in Wastewater

Abstract

Efficiency in HPLC can be enhanced by increasing the column length and/or decreasing the particle size. The use of high temperature in HPLC has emerged as a valuable tool to overcome the increase in column backpressure when using small packing particles, as it allows for reduction in mobile phase viscosity. In this study, high plate count was obtained by coupling sub-2 lm columns at elevated temperature to reduce the viscosity of the mobile phase, thus reducing the column backpressure. At 80°C, up to three columns of 15 cm 9 4.6 mm I.D. packed with 1.8 lm particles could be coupled generating *84,000 theoretical plates for the last eluting compound. The number of theoretical plates was increased on average by a factor of *3.6 when three columns were coupled at 80°C compared with one column at 30°C. The relationships between separation efficiency and column length were examined using Van Deemter plots constructed at 30°C and 80°C for different column lengths. The advantages of using coupled columns in combination with elevated temperature for the environmental analysis were illustrated using test mixtures comprised of eight sulfonamides separated on one column at 30°C and three coupled columns at 80°C by isocratic elution. Sample clean up was carried out by employing solid-phase extraction (SPE) using Oasis HLB cartridges. The method developed was validated based on parameters such as linearity, precision, accuracy, detection and quantification limits. Recoveries generally ranged from 71.7 to 99% (with the exception of sulfanilamide), with standard deviations not higher than 4.7%. The detection limits of the method ranged from 0.6-2 lg L -1 , while limits of quantification were in the range 2-6.7 lg L -1 with UV detection.

Optimization and validation of a fast ultrahigh‐pressure liquid chromatographic method for simultaneous determination of selected sulphonamides in water samples using a fully porous sub‐2 μm column at elevated temperature

“…The extraction was carried out in this study without adjusting the sample pH to accommodate all analytes studied. The low recovery found for SNM was also reported in other studies carried out with Oasis HLB cartridges [10,24].…”

“…Mobile-phase composition of 20% acetonitrile allowed all analytes to be baseline separated with good resolution in 3 min. The method developed has the highest performance in terms of analytical speed compared with other published HPLC-UV methods for the determination of sulphonamides [10,[30][31][32]. The isocratic mode of separation eliminated the need for re-equilibration, minimizing the turn-around time.…”

“…The method developed provided shorter analysis time compared with any other published HPLC-UV methods used to determine sulphonamides in environmental samples (e.g. [10,23,25]). …”

“…In the recent years, the continual discharge of pharmaceuticals to the aquatic environment has become an issue of great concern [10]. Pharmaceuticals enter the aquatic environment from households, hospitals and industrial units.…”

“…A limited number of analytical methods based on HPLC coupled with UV detection are available for the determination of sulphonamides in environmental samples, e.g. [10,[23][24][25]. Since pharmaceuticals are found in environmental samples at low concentrations ranging from ng/L to mg/L and because the matrix in such samples is usually very complicated, sensitive and highly efficient methods are required for their analysis, particularly in natural and wastewaters.…”