Separations, Volume 3, Issue 1 (March 2016) – 10 articles

The simple and simultaneous determination of silicic, boric and carbonic acids was made using ion-exclusion chromatography (IEC) and a Corona™ charged aerosol detector (C-CAD). Silicic and boric acids were separated by the column packed with a weakly acidic cation-exchange resin in H⁺-form and ultra-pure water eluent, and the detector responses were improved by the addition of acetonitrile to eluent. Under the optimized conditions, the simultaneous determination of weak inorganic acids, except for carbonic acid, was successfully performed. When the conversion column packed with a strong acidic cation-exchange resin in Na⁺- or K⁺-form was inserted between the separation column and the detector, weak inorganic acids including carbonic acid could be detected by the C-CAD. The calibration curves were linear in the range of 0.5–10 mg·L⁻¹ as Si for silicic acid (r² = 0.996), 10–100 mg·L⁻¹ as B for boric acid (r² = 0.998) and 1.3–21 mg·L⁻¹ as C for carbonic acid (r² = 0.993). The detection limits based on three times the standard deviation were 0.03 mg·L⁻¹ as Si for silicic acid, 0.40 mg·L⁻¹ as B for boric acid and 0.08 mg·L⁻¹ as C for carbonic acid. This method was applicable to river, hot spring and drinking water. Full article

The widespread use of antibiotics in veterinary practice and aquaculture has led to the increase of antimicrobial resistance in food-borne pathogens that may be transferred to humans. Global concern is reflected in the regulations from different agencies that have set maximum permitted residue limits on antibiotics in different food matrices of animal origin. Sensitive and selective methods are required to monitor residue levels in aquaculture species for routine regulatory analysis. Since sample preparation is the most important step, several extraction methods have been developed. In this review, we aim to summarize the trends in extraction of several antibiotics classes from shrimps and give a comparison of performance characteristics in the different approaches. Full article

In this study, polydimethylsiloxane (PDMS)-coated capillary columns (TRB-5 and TRB-35), both unmodified and functionalized with single-wall carbon nanotubes (SWCNTs) or multiwall carbon nanotubes (MWCNTs), have been tested and compared for the extraction of amphetamine (AMP), methamphetamine (MET) and ephedrine (EPE) by in-tube solid-phase microextraction (IT-SPME). Prior to their extraction, the analytes were derivatized with the fluorogenic reagent 9-fluorenylmethyl chloroformate (FMOC). For separation and detection capillary chromatography with fluorimetric detection has been used. The presence of carbon nanotubes in the extractive coatings enhanced the extraction efficiencies and also significantly improved the chromatographic profiles, thus resulting in a reliable option for the analysis of these drugs. As an example of application, a new method is proposed for the analysis of the tested amphetamines in oral fluid using a TRB-35 capillary column functionalized with MWCNTs. The proposed conditions provided suitable selectivity and reproducibility (CV ≤ 6%, n = 3) at low µg/mL levels, and limits of detection of 0.5–0.8 µg/mL. Full article

Nano HPLC-MS/MS separation and detection of peptides for proteomic analysis is usually performed upon tryptic digest of proteins and peptide pre-concentration on trap columns. Pre-concentration on trap columns is needed for sample wash (removal of salts and impurities), sample focusing prior to separation, and volume reduction. Usually, trap columns are mounted on selection valves close to the separation column in order to keep the void volume low and to enable injection of large sample amounts onto nano-separation column. Since separation columns are operated at elevated temperature of ≥45 °C and they are mounted on the same valve as the trap column (in the column oven); loading samples at elevated temperature will result with significant loss of analytes. A method for loading samples on a trap column at 60 °C was developed and optimized. No sample loss was observed when the optimized method was used for analysis of standards and of complex biological samples. Full article

Water samples were collected and analyzed for conductivity, pH, temperature and trihalomethanes (THMs) during the fall of 2014 at two monitored municipal drinking water source ponds. Both spot (or grab) and time weighted average (TWA) sampling methods were assessed over the same two day sampling time period. For spot sampling, replicate samples were taken at each site and analyzed within 12 h of sampling by both Headspace (HS)- and direct (DI)- solid phase microextraction (SPME) sampling/extraction methods followed by Gas Chromatography/Mass Spectrometry (GC/MS). For TWA, a two day passive on-site TWA sampling was carried out at the same sampling points in the ponds. All SPME sampling methods undertaken used a 65-µm PDMS/DVB SPME fiber, which was found optimal for THM sampling. Sampling conditions were optimized in the laboratory using calibration standards of chloroform, bromoform, bromodichloromethane, dibromochloromethane, 1,2-dibromoethane and 1,2-dichloroethane, prepared in aqueous solutions from analytical grade samples. Calibration curves for all methods with R² values ranging from 0.985–0.998 (N = 5) over the quantitation linear range of 3–800 ppb were achieved. The different sampling methods were compared for quantification of the water samples, and results showed that DI- and TWA- sampling methods gave better data and analytical metrics. Addition of 10% wt./vol. of (NH₄)₂SO₄ salt to the sampling vial was found to aid extraction of THMs by increasing GC peaks areas by about 10%, which resulted in lower detection limits for all techniques studied. However, for on-site TWA analysis of THMs in natural waters, the calibration standard(s) ionic strength conditions, must be carefully matched to natural water conditions to properly quantitate THM concentrations. The data obtained from the TWA method may better reflect actual natural water conditions. Full article

A sensitive and selective ultra-high performance liquid chromatography-tandem mass spectrometric method was developed for the quantification of temozolomide (TMZ) in nonhuman primate (NHP) plasma, cerebrospinal fluid (CSF), and brain extracellular fluid (ECF) following microdialysis. Ethyl acetate was used to extract the plasma and CSF samples, using theophylline as the internal standard (IS). ECF samples were diluted with acetonitrile prior to analysis. TMZ was separated on a Waters UPLC^® BEH C18 column with an isocratic mobile phase of ammonium acetate (10 mM)-0.1% formic acid/acetonitrile (30:70, v/v) in a positive-ion multiple reaction monitoring mode (m/z 195.5→137.6 for TMZ; m/z 181.5→124.2 for IS). The retention time of TMZ and theophylline was 0.45 min with a total run time of 2.5 min. The method was validated over the range from 5–2000 ng/mL in NHP plasma, CSF, and ECF with respect to linearity, accuracy, precision, selectivity, and stability. This method was successfully applied toward the measurement of pharmacokinetic samples following various routes of drug administration. Full article

This article presents an overview of recent advances in the field of portable capillary electrophoresis and microchip electrophoresis equipment during the period 2013–Mid 2015. Instrumental achievements in the separation as well as the detection part of the equipment are discussed. Several applications from a variety of fields are described. Full article

A novel method for the labeling and rapid separation of morphine, morphine-3-beta-d-glucuronide (M3G) and morphine-6-beta-d-glucuronide (M6G) in human urine employing a new boronic acid functionalized squarylium dye (SQ-BA3) and capillary electrophoresis with laser induced fluorescence detection (CE-LIF) is described. The spectrochemical properties, solution stability, pH range, and mechanisms for interactions with morphine and its metabolites were first established for SQ-BA3, followed by optimization of an on-column labeling procedure and CE-LIF method. SQ-BA3 itself was shown to be unstable and weakly fluorescent in aqueous buffers due to aggregate formation. However, SQ-BA3 showed a relative stability and dramatic increase in fluorescence intensity upon the addition of morphine, M3G, and M6G. Because of the low background fluorescence of this dye, on-column labeling was feasible, leading to a simple and rapid analytical method with the potential for clinical applications. Full article