Understanding the effects of mineral water matrix on degradation of several pharmaceuticals by ultrasound: Influence of chemical structure and concentration of the pollutants

Degradation of seven relevant pharmaceuticals with different chemical structures and properties: acetaminophen (ACE), cloxacillin (CXL), diclofenac (DCF), naproxen (NPX), piroxicam (PXC), sulfacetamide (SAM) and cefadroxil (CDX), in distilled water and mineral water by ultrasound was studied herein. Firstly, proper conditions of frequency and acoustic power were determined based on the degradation ability of the system and the accumulation of sonogenerated hydrogen peroxide (24.4 W and 375 kHz were found as the suitable conditions for the sonochemical treatment of the pharmaceuticals). Under such conditions, the pharmaceuticals degradation order in distilled water was: PXC > DCF ~ NPX > CXL > ACE > SAM > CDX. In fact, the initial degradation rate showed a good correlation with the Log P parameter, most hydrophobic compounds were eliminated faster than the hydrophilic ones. Interestingly, in mineral water, the degradation of those hydrophilic compounds (i.e., ACE, SAM and CDX) was accelerated, which was attributed to the presence of bicarbonate ions. Afterwards, mineral water containing six different initial concentrations (i.e., 0.331, 0.662, 3.31, 16.55, 33.1, and 331 µM) of selected pharmaceuticals was sonicated, the lowest concentration (0.331 µM) always gave the highest degradation of the pollutants. This result highlights the great ability of the sonochemical process to treat bicarbonate-rich waters containing pollutants at trace levels, as pharmaceuticals. Finally, the addition of ferrous ions to the sonochemical system to generate a sono-Fenton process resulted in an acceleration of degradation in distilled water but not in mineral water. This was attributed to the scavenging of sonogenerated HO• by bicarbonate anion, which decreases H₂O₂ accumulation, thus limiting the Fenton reaction.     

Determination of Benzocaine Using HPLC and FIA with Amperometric Detection on a Carbon Paste Electrode

A new method for benzocaine determination employing FIA and HPLC with electrochemical detection on a carbon paste electrode was developed. The optimum conditions for the determination were found. Carrier solution for FIA consisted of B–R buffer pH 4 (80 % methanol, v/v) and used flow rate was 1.0 mL min^?1. Mobile phase for HPLC consisted of B–R buffer pH 4 (75 % methanol, v/v) with flow rate 0.4 mL min^?1. Working potential of +1.2 V was employed. Practical applicability of the methods was tested on the determination of benzocaine in selected pharmaceuticals. The results were in agreement with results obtained using spectrophotometric detection and with one exception also with the content declared by the manufacturer.     

Comparison of four extraction methods for the analysis of pharmaceuticals in wastewater

As one category of the most urgent emerging pollutants, pharmaceuticals have provoked much public and scientific attention due to widespread contamination in aquatic environment. In this study, two active methods by Oasis HLB and MCX and two passive methods by XAD-16 and XAD-16/7 were evaluated for determining the concentrations of 10 pharmaceuticals (carbamazepine, clofibric acid, diclofenac, gemfibrozil, ibuprofen, ketoprofen, naproxen, paracetomol, terbutaline and triclosan) in reclaimed wastewater. Recoveries of the target pharmaceuticals extracted by MCX were higher than HLB except for diclofenac and ketoprofen. For the passive methods, the addition of polar resin XAD-7 improved the recovery compared with the addition of XAD-16 only. The mean recoveries of the target analytes by XAD-16/7 ranged from 22 to 75.8%. The limit of quantification (LOQ) ranged between 25 and 280 ng/L. In addition, by comparing the accuracy and precision of XAD-16/7 method and MCX method, we further demonstrated that the XAD-16/7 method can be satisfactorily used for the analysis of pharmaceuticals in wastewater samples. We applied the method to some wastewater samples from sewage treatment plant (STP) nearby Riverside, CA to track the concentration change of pharmaceuticals in the treatment processes. The result shown that pharmaceuticals were effective reduced in STP mostly by activated sludge.     

Multi-class determination of around 50 pharmaceuticals, including 26 antibiotics, in environmental and wastewater samples by ultra-high performance liquid chromatography-tandem mass spectrometry

A multi-class method for the simultaneous quantification and confirmation of 47 pharmaceuticals in environmental and wastewater samples has been developed. The target list of analytes included analgesic and anti-inflammatories, cholesterol lowering statin drugs and lipid regulators, antidepressants, anti-ulcer agents, psychiatric drugs, ansiolitics, cardiovasculars and a high number (26) of antibiotics from different chemical groups. A common pre-concentration step based on solid-phase extraction with Oasis HLB cartridges was applied, followed by ultra-high performance liquid chromatography-tandem mass spectrometry (UHPLC-MS/MS) measurement. All compounds were satisfactorily determined in just one single injection, with a chromatographic run time of only 10 min. The process efficiency (combination of the matrix effect and the extraction process recovery) for the 47 selected compounds was evaluated in nine effluent wastewater (EWW) samples, and the use of different isotope-labelled internal standards (ILIS) was investigated to correct unsatisfactory values. Up to 12 ILIS were evaluated in EWW and surface water (SW). As expected, the ILIS provided satisfactory correction for their own analytes. However, the use of these ILIS for the rest of pharmaceuticals was problematic in some cases. Despite this fact, the correction with analogues ILIS was found useful for most of analytes in EWW, while was not strictly required in the SW tested. The method was successfully validated in SW and EWW at low concentration levels, as expected for pharmaceuticals in these matrices (0.025, 0.1 and 0.5 μg/L in SW; 0.1 and 0.5 μg/L in EWW). With only a few exceptions, the instrumental limits of detection varied between 0.1 and 8 pg. The limits of quantification were estimated from sample chromatograms at the lowest spiked levels tested and normally were below 20 ng/L for SW and below 50 ng/L for EWW. The developed method was applied to the analysis of around forty water samples (river waters and effluent wastewaters) from the Spanish Mediterranean region. Almost all the pharmaceuticals selected in this work were detected, mainly in effluent wastewater. In both matrices, analgesics and anti-inflammatories, lipid regulators and quinolone antibiotics were the most detected groups.     

Folarographic Behaviour of Nitrendipine

Abstract

Nifedipine, a calcium antagonist drug, proceduces a well-defined polarographic wave due to the four-electron, four-proton reduction of the nitro group. This peak is diffusion-controlled and shows a linear dependence on the Nitrendipine concentration. This behaviour is used for analytical purposes in determining Nitrendipine content in commercial preparations. The method is sensitive enough to be applied to single tablet, assays.

However, the principal advantage lies in the prompt determination. Preparation of the samples is easy and no extraction procedure is required. The method is recommended for uniformity contents studies and stability tests in day-to-day routine analyses.     

Separation methods for captopril in pharmaceuticals and biological fluids

Captopril (CAP) is an orally active angiotensin-converting enzyme (ACE) inhibitor and has been widely used for management of hypertension and congestive heart failure. CAP lacks an aromatic chromophore required for facile direct UV detection and also has two chiral centers. These factors can render the determination of CAP in complex matrices challenging. This review covers more than 20 years of analytical research on this drug, focusing mainly on pharmaceutical and biological applications. The primary separation techniques discussed are gas chromatography, liquid chromatography, and capillary electrophoresis. The structures of the CAP derivatizing agents as well as a table summarizing various HPLC methods are provided. A discussion of key recent chromatographic and electrophoretic methods for other ACE inhibitors is also present.     

Dispersive liquid-liquid microextraction combined with gas chromatography for extraction and determination of class 1 residual solvents in pharmaceuticals

The present study reports a new method for analyzing class 1 residual solvents (RSs), 1,1-dichloroethene (1,1-DCE), 1,2-dichloroethane (1,2-DCE), 1,1,1-trichloroethane (1,1,1-TCE), carbon tetrachloride (CT), and benzene (Bz), in pharmaceutical products using dispersive liquid-liquid microextraction (DLLME) combined with gas chromatography-flame ionization detection (GC-FID). Unlike common DLLME methods, solvents of high boiling point were selected as dispersive and extraction solvents in order to prevent their chromatographic peaks from overlapping with those of analytes that have short retention times. Therefore N,N-dimethyl formamide (DMF) and 1,2-dibromoethane (1,2-DBE) were chosen as dispersive and extraction solvents, respectively. Analytical parameters of the proposed method were determined and good linearities and broad linear ranges (LRs) were obtained. Taking 500 mg samples, limit of detections for the tested pharmaceuticals were obtained as 0.11, 0.03, 0.05, 0.05, and 0.006 μg g(-1) for CT, 1,1-DCE, 1,2-DCE, 1,1,1-TCE, and Bz, respectively, which are considerably much lower than their permissible limits in pharmaceuticals.     

The analysis of a group of acidic pharmaceuticals, carbamazepine, and potential endocrine disrupting compounds in wastewater irrigated soils by gas chromatography-mass spectrometry

The analysis of pharmaceuticals and potential endocrine disruptors in the environment has rightly concentrated on their presence in wastewaters and possible contamination of receiving bodies, such as groundwaters. However, wastewater is increasingly being reused for irrigation and in order to fully understand the environmental fate of these compounds, reliable methods for their analysis in soil are required, of which there are relatively few available. This article reports a method for a range of acidic pharmaceuticals, carbamazepine, and endocrine disrupting compounds in soils with final analysis by gas chromatography-mass spectrometry. Two soil types (Phaeozom and Leptosol) and three fortification levels were used to validate the method. Recoveries of acidic pharmaceuticals varied between 62 and 102%, carbamazepine from 75 to 118%, and potential endocrine disruptors between 54 and 109%; most recoveries were between 75 and 95% and relative standard deviations were generally less than 10%. Detection limits were between 0.25 and 2.5 ng/g except for phthalates and 4-nonylphenols (25 ng/g). The method was used to analyze soils where untreated wastewaters have been used to irrigate crops for approximately 90 years. Concentrations of acidic pharmaceuticals in the soil were <1 ng/g and potential endocrine disruptors varied from below the limit of detection (estrone, 17β-estradiol, and 17α-ethinylestradiol) to 2079 ng/L (bis-diethylhexyl phthalate). This data indicated that despite the continuous application of the contaminants over many years, concentrations were generally lower than those expected to be contributed by a single irrigation event. Only carbamazepine, at concentrations of 6.48 ng/g (in Phaeozem) and 5.14 ng/g (in Leptosol), showed any evidence of persistence in the soils analyzed.     

Theoretical prediction of the native fluorescence of pharmaceuticals

At present, to search fluorescent compounds or to increase the native fluorescence is an active research line specially and not only with analytical purposes. On some analytical areas and from the early times of applications of fluorescence (mid-fifties) the fluorimeter was defined as the suitable detector for determination of pharmaceuticals and subsequently, this detection mode has been widely applied. Therefore, it is mandatory to develop new strategies to discover or to enhance in a simple way the native fluorescence of organic compounds to increase the number of analytes to be determined by direct fluorescence.In the present paper are studied further applications of a new tool suitable to increase the research in analytical field. Calculations on molecular connectivity and discriminant analysis are applied to a certain number of pharmaceuticals (and some pesticides) on which fluorescence behaviour was observed in an experimental screening or obtained from scientific literature. The screening tests were based on the on-line fluorimetric measurement by using a continuous-flow assembly. The screening comprised pre-selected compounds with different molecular structures. The theoretical predictions agree with the empirical results from the screening test.     

High performance liquid chromatography-high resolution mass spectrometry and micropulverized extraction for the quantification of amphetamines, cocaine, opioids, benzodiazepines, antidepressants and hallucinogens in 2.5 mg hair samples

A high performance liquid chromatography-high resolution mass spectrometry (HPLC-HRMS) method for simultaneous screening and quantification of 28 drugs was developed and validated for 2.5 mg hair samples. Target drugs and their metabolites included amphetamines, cocaine, opioids, benzodiazepines, antidepressants, and hallucinogens. After decontamination, hair samples were extracted with 200 μL of a mixture of water: acetonitrile:1 M trifluoroacetic acid (80:10:10, v/v) using a 5 min simultaneous pulverization/extraction step. The extracts were analysed by HPLC-HRMS in an Orbitrap at a nominal resolution of 60,000, with concomitant in source collisional experiments (in source CID). Gradient elution on an Atlantis T3 column resolved 28 target compounds and 5 internal standards. Total chromatographic run time was 26 min. Calibration was achieved by linear regression analysis utilizing six calibration points; R2 ranged from 0.9964 to 0.9999, the limits of quantification were 0.1 ng/mg for 8 compounds, 0.2 ng/mg for 16 compounds and 0.5 ng/mg for 4 compounds; mean relative errors from -21% to +23% were obtained; relative standard deviation, used to estimate repeatability and intermediate reproducibility at three concentrations, was always less than 20%. Process efficiency and recoveries for all analytes were better than 65 and 73%, respectively, at any concentration. The method was applied to hair samples from forensic investigations that contained a broad assortment of drugs of abuse and pharmaceuticals. The use of concomitant HRMS full scan and CID afforded the possibility of retrospective analysis for discovering untargeted drugs.