CE-DAD-MS/MS in the simultaneous determination and identification of selected antibiotic drugs and their metabolites in human urine samples

In this study, a new analytical method was developed and validated for the simultaneous analysis of antibiotic drugs (amoxicillin, cefotaxime, ciprofloxacin, clindamycin, linezolid, metronidazole) and their metabolites (amoxycilloic acid, amoxicillin diketopiperazine, 3-desacetyl cefotaxime lactone, clindamycin sulfoxide, ciprofloxacin piperazinyl-N4-sulfate, linezolid N-oxide, metronidazole-OH) in human urine. Capillary electrophoresis (CE) along with the tandem mass spectrometry (MS/MS) was used to determine and identify all analytes. Appropriate conditions for MS/MS measurements along with the use of the central composite design were optimized. The effects of different analytical conditions (the composition, the concentration, and the pH value of the background electrolyte, the time and pressure of the injection, the capillary temperature and influence of the organic modifier) on the migration and separation of antibiotic drugs and metabolites were examined using the CE-DAD. The analytical procedure was linear for concentrations ranging from 20 to 1000 ng/mL, with determination coefficients higher than 0.99 for all the analytes. The validated analytical procedure was then applied to the measurement of antibiotic drugs and their metabolites in human urine samples.     

The determination of N-nitrosamines in alkylamines using the thermal energy analyzer

N-Nitrosodiethylamine can be determined in diethylamine and triethylamine, and N-nitrosodiisopropylamine can be determined in monisopropylamine and diisopropylamine using the same analytical procedure. This procedure combines an extraction step with final analysis of the concentrated extract by gas chromatography-thermal energy analyzer. Concentrations of nitrosoamine in alkylamine at levels of 10 ppb to 1 ppm can be measured with a precision of ± 10% when using 10-g samples. Lower limits of detection were not investigated but could probably be controlled by sample size.     

Determination of ultratrace levels of dissolved metals in seawater by reaction cell inductively coupled plasma mass spectrometry after ammonia induced magnesium hydroxide coprecipitation

A method for the determination of ultratrace amounts of Cr, Fe, Mn, Pb and Zn in seawater has been developed. It combined the low-blank magnesium hydroxide coprecipitation procedure with quadrupole inductively coupled plasma mass spectrometry and used the dynamic reaction cell technique to resolve the polyatomic interferences arising from the residual matrix, the solvent and plasma gases. Detection limits (3σ_B, n = 10) for Cr, Fe, Mn, Pb and Zn were 0.02, 0.10, 0.01, 0.002 and 0.19 nM, respectively, using 50 mL of seawater sample. The accuracy of the analytical procedure was verified by the analysis of the seawater reference materials CASS-4, NASS-5, SAFe D2 and SAFe S. The analytical precision ranged from 3% to 16% (n = 6), with a sample throughput of about 6 samples h⁻¹.     

In situ application of a cellulose bag and an ion exchanger for differentiation of labile and inert metal species in aquatic systems

This work involved the development and application of a new analytical procedure for in-situ characterization of the lability of metal species in aquatic systems by using a system equipped with a diffusion membrane and cellulose organomodified with p-aminobenzoic acid groups (DM-Cell-PAB). To this end, the DM-Cell-PAB system was prepared by adding cellulose organomodified with p-aminobenzoic acid groups (Cell-PAB) to pre-purified cellulose bags. After the DM-Cell-PAB system was sealed, it was examined in the laboratory. The in-situ application involved immersing the DM-Cell-PAB system in two different rivers, enabling us to study the relative lability of metal species (Cu, Cd, Fe, Mn, and Ni) as a function of time and quantity of exchanger. The procedure is simple and opens up a new perspective for understanding environmental phenomena relating to the complexation, transport, stability, and lability of metal species in aquatic systems rich in organic matter.     

Fractionation of Bulgarian viper (Vipera ammodytes) venoms. Relation of venom content and subspecies affiliation of the snakes

Summary A cation-exchange procedure has been developed for fractionation of venom from Bulgarian snakes (Vipera ammodytes), using a 75×7.5 mm TSK SP-5 PW column for gradient elution of venom components with NH₄OAc and UV-detection at 280 nm. The procedure developed was applied for venom component separation and especially to assay the vipoxin content—a previously studied and described toxic protein complex—in the venom of various subspecies of Bulgarianvipera ammodytes. Chromatographic profiles obtained show that venom fromVipera ammodytes ssp.montandoni Boulenger, 1904 andVipera ammodytes ssp.meridionalis Boulenger, 1903 contain vipoxin (content higher in venom ofVipera ammodytes ssp.meridionalis), while in the venom ofVipera ammodytes ssp.ammodytes Linnaeus, 1758 vipoxin is absent. All data obtained show that the procedure developed can be successfully used for reliable subspecies affiliation by venom analysis and assay of vipoxin (in analytical mode) and its purification (in semipreparative mode) also.     

Salting-out homogeneous liquid-liquid microextraction for the determination of azole drugs in human urine: Validation using total error concept

A salting-out homogeneous liquid-liquid microextraction was proposed for the quantification of four azole drugs in human urine prior to high-performance liquid chromatography analysis. The procedure involved the mixing of the sample with acetonitrile in appropriate volumes followed by the addition of sodium sulfate solution in order to facilitate phase separation. The parameters influencing the extraction performance were studied and optimized using a two-step experimental design. The analytical procedure was thoroughly validated using the accuracy profiles as a graphical decision-making tool. The β-expectation tolerance intervals did not exceed the acceptance criteria of ±15% meaning that 95% of future results will be included in the defined bias limits. The limits of detection of the procedure were satisfactory, ranging between 0.01 and 0.03 μg/mL. The mean analytical bias in the spiking levels was satisfactory and ranged between –10.3 and 4.2% while the relative standard deviation was lower than 5.6%. Monte-Carlo simulations followed by capability analysis were employed to investigate the ruggedness of the sample preparation protocol. The developed method offers advantages compared to previously reported approaches for the same type of analysis including extraction efficiency and scaling down of the sample volume and extraction time.     

Sequential voltammetric determination of trace metals in meals

An analytical procedure for the sequential determination of Zn(II), Cr(VI), Cu(II), Sb(III), Sn(II), Pb(II) by square wave anodic stripping voltammetry (SWASV) and Fe(III), Mn(II), Mo(VI) by square wave voltammetry (SWV) in matrices involved in foods and food chain as wholemeal, wheat and maize meal is described.The digestion of each matrix was carried out using a concentrated HCl–HNO₃–H₂SO₄ attack mixture, employing dibasic ammonium citrate buffer solution (pH 6.9 and 8.7) as supporting electrolytes. The analytical procedure was verified by the analysis of the standard reference materials Wholemeal BCR-CRM 189, Wheat Flour NIST-SRM 1567a and Rice Flour NIST-SRM 1568a.For all the elements in the certified matrix, the precision as repeatability, expressed as relative standard deviation (s_r) was of the order of 3–5%; the accuracy, expressed as relative error (e) was generally of the order of 3–6%.In presence of reciprocal interference, the standard addition method considerably improved the resolution of the voltammetric technique.Finally, the analytical procedure was transferred and applied to commercial meals sampled on market.A critical comparison with atomic absorption spectroscopic measurements is also discussed.     

High‐performance liquid chromatographic determination of multi‐mycotoxin in cereals and bean foodstuffs using interference‐removal solid‐phase extraction combined with optimized dispersive liquid–liquid microextraction

A novel pre‐treatment was proposed for the simultaneous determination of aflatoxins, ochratoxin A and zearalenone in foodstuffs using high‐performance liquid chromatography with fluorescence detection. The analytical procedure was based on a first step using a quick, easy, cheap, effective, rugged, and safe based extraction procedure, followed by salting out and purification with a C₁₈ solid‐phase extraction column as interference removal clean‐up. Subsequently, collected supernatant was subjected to dispersive liquid–liquid microextraction. Response surface methodology based on central composite design was employed to optimize conditions in the microextraction procedure. Under the optimum conditions, satisfactory analytical performance with recoveries ranging from 63.22 to 107.6% were achieved in different types of cereals and beans, as well as desirable precisions (0.81–8.13%). Limits of detections and quantifications for these six mycotoxins ranging from 0.03 to 13 μg/kg and 0.22 to 44 μg/kg, respectively, were obtained. Finally, the established method was successfully validated by four certified reference materials (P  = 0.897 > 0.05) and applied to 79 samples from local markets.     

Simultaneous Determination of Aluminum and Iron in High Salt Content Matrices by Adsorptive Stripping Voltammetry. Application to Dialysis Fluids

A new analytical procedure for the simultaneous determination of aluminum(III) and iron(II) in two kinds of dialysis fluids (peritoneal and hemodialysis fluids) by differential pulse adsorptive stripping voltammetry (DPAdSV) is described. The voltammetric measurements were performed using, as working electrode, a stationary mercury electrode, and a platinum electrode and a Ag|AgCl|KCl_(sat.) electrode as auxiliary and reference electrodes, respectively, employing acetate buffer solutions at different pH as supporting electrolyte. As complexing agents, Solochrome Violet RS, Palatine Chrome Black 6BN, Chromazurol S and Eriochrome Black T were employed. For both elements, the accuracy, expressed as relative recovery R%, was very satisfactory being in the range 94–105%, the precision as repeatability, expressed as relative standard deviation s_r%, was lower than 6%, while the limits of detection were of the order of a few units of μg/L. The analytical voltammetric procedure has been validated by comparison with spectroscopic (graphite furnace atomic absorption spectroscopy, GFAAS) measurements.     

An advanced automation platform coupled with mass spectrometry for investigating in vitro human skin permeation of UV filters and excipients in sunscreen products

Rationale

Systemic absorption of UV-filtering chemicals following topical application of sunscreens may present a safety concern. The Food and Drug Administration (FDA) had recommended an in vitro skin permeation test (IVPT) to evaluate the potential of this safety risk for the evaluation of sunscreens prior to clinical studies. Therefore, a sensitive and robust bioanalytical method(s) were required for IVPT studies of different topical sunscreen products.

Methods

An analytical procedure to quantitate sunscreen UV-filtering components and excipients in IVPT samples including avobenzone, octocrylene, oxybenzone, ecamsule, methylparaben and propylparaben was developed employing a RapidFire 360 robotic sample delivery system coupled with a triple quadrupole mass spectrometer. The analytical procedure was developed and validated according to the requirements of the FDA Bioanalytical Method Validation Guidance for Industry (2018).

Results

The analytical method provided a turnaround time of 12 seconds per sample and was determined to be accurate, precise, specific, and linear over the corresponding analytical ranges. The validated method was successfully applied for two IVPT studies for evaluating the skin permeation potential of UV-filtering chemicals and assisting with the selection of the sunscreen products for the clinical study conducted by the FDA.

Conclusions

This work highlights the first analytical procedure that has applied a non-chromatographic-MS/MS automation platform to an in vitro biopharmaceutics study. The analytical platform simultaneously quantitated four UV filters and two excipients in complex media to evaluate their permeation in IVPT studies. The sample throughput and analytical performance of advanced automation platforms indicate their analytical procedure has the potential to significantly advance the efficiency of IVPT studies to evaluate permeation of a wide variety of UV chemical filters and excipients for topical OTC sunscreen products.

     

Ubiquinone and photochemical activity in Rhodospirillum rubrum.

Abstract— An analytical procedure was developed for quantitatively determining the ubiquinone content of bacterial photosynthetic material. High sensitivity was obtained by supplementing growth media with¹⁴C-labelled p-hydroxybenzoic acid which was specifically incorporated into the benzoquinones, ubiquinone and rhodoquinone. Sufficiently radioactive p-hydroxybenzoic acid was used so that 10 picomoles of ubiquinone could be quantitatively measured. High accuracy was obtained by using a carrier technique which was employed during the extraction and isolation of quinones for analyses. Purification of quinones was achieved by selective solvent extraction and thin layer chromatography in two different solvent systems. This analytical procedure was employed to determine the ubiquinone content of R. rubrum chromatophores following hydrocarbon solvent extraction to remove ubiquinone from the chromatophores. Ubiquinone was found to exist in at least two pools: a loosely bound pool which easily extracted with hydrocarbon solvents, and a tightly bound pool which required addition of some polar solvent for its removal. It was demonstrated that ubiquinone would not exchange readily between these two pools. Careful analyses of all protein fractions showed that less than 0.06 ubiquinone per primary electron donor unit (P865) could be covalently bound to these components. From the average of a number of measurements, the tightly bound ubiquinone was determined as very nearly one-half ubiquinone per phototrap (0.48 ± 0.05 S.D.). Removal of the tightly bound ubiquinone was linearly related to the loss of primary photochemical capacity. These results are consistent with the ‘duplex model’ for primary photochemical events but would seem to rule out an iron-ubiquinone complex where the ubiquinone can function only between the semiquinone and the fully oxidized oxidation state.     

Determination of Anti-Tumor Agent TM208, 4-Methyl-piperazine-1-carbodithioc Acid 3-Cyano-3,3-diphenylpropyl Ester Hydrochloride,in Rats by LC

A new, specific and sensitive high performance liquid chromatography analytical procedure was developed and validated for the determination of TM208 in rat primary solid organs/tissues and plasma. TM208 was extracted from the appropriate matrix using methanol followed by centrifugation at 11,255×g for 20 min and injection of a 30 μL aliquot. Separation was carried out under gradient conditions using an ODS C18 column equipped with a guard column. The mobile phase consisted of methanol and water and retention times of TM208 and plunarizine (IS) were 17.658 and 26.175 min, respectively. The analytical procedure provided acceptable precision, accuracy, recoveries and linearity. Stability studies showed that TM208 was stable in organs/tissues homogenates for three freeze–thaw cycles, at room temperature for at least 24 h 3 weeks at −20 °C. The validated method was successfully applied to the determination of TM208 in SD rats following oral administration at a dose of 250 mg kg⁻¹.

     

Analytical supercritical fluid extraction of Chinese herbal medicines

Summary An analytical supercritical fluid extraction (SFE) technique, followed by GC/MS, was developed to separate and determine the volatile components in Chinese herbal medicine. Three kinds of herbs, frankincense, myrrh, andEvodia rutaecarpa were extracted and analyzed. The extraction was carried out using supercritical fluid CO₂ at 20 MPa and 50°C. The main factors affecting the efficiency and selectivity of the extraction are discussed. The results revealed the potential of supercritical fluid extraction as an analytical procedure for the study of medicinal plants.     

Maintenance of Soft Calibration Models in the Determination of Zinc,Cadmium, Lead and Copper by Differential Pulse Anodic Stripping Voltammetry

A strategy for constructing a global multivariate calibration model that includes calibration samples measured over time on different days is developed and applied in electroanalysis. Both synthetic and real samples (tap, extracted and river water) are analyzed by differential‐pulse anodic stripping voltammetry, showing the suitability of the global model constructed that provides successful results similar to those of the usual multivariate calibration. In addition the capability of discrimination of this model is evaluated in prediction for the mean of three replicates with estimation of probability of false noncompliance, α, and false compliance, β, being found 3.1, 11.2, 6.7 and 64.7 nM for nominal concentrations of zinc, cadmium, lead and copper of 96.0, 40.4, 37.3 and 328.0 nM respectively when α=β=0.05. It has been proven that the use of the global calibration does not imply a loss of multivariate analytical sensitivity, using this parameter as quality index of the analytical procedure. The viability of using calibration maintenance strategies with electroanalytical techniques is shown, providing a way to save time and experimental effort when these techniques are used in routine analysis.     

Immunoassay for Highly Water-Soluble Nitenpyram: Evaluating the Analytical Performance of an Easy-to-Use Screening Method for Agricultural Samples

Abstract

Nitenpyram, a neonicotinoid insecticide, is highly soluble in water (>5.9?×?10⁵?mg/L). Specifically examining its physicochemical properties, we have established a simple and rapid residue analytical method for nitenpyram using an enzyme-linked immunosorbent assay (ELISA) which requires no organic solvents. The I₅₀ value found with this ELISA method using a selective monoclonal antibody toward nitenpyram was 4.8?ng/mL. A hand-shaking method using water was applied for ELISA analysis to extract nitenpyram from fruiting vegetable samples of four kinds. Matrix effects caused by interfering substances coexisting in aqueous sample extracts were reduced by dilution with water. No problems were found in the analytical values obtained using ELISA. From analyses of nitenpyram-incurred fruiting vegetables with the proposed ELISA and the reference HPLC protocols, high mutual correlation was found, which suggests that the measurement accuracy of the proposed ELISA method is comparable to the reference HPLC procedure.     

Simultaneous Voltammetric Determination of Nitrites and Nitrates in Waters

A rapid procedure was developed for the simultaneous voltammetric determination of nitrites and nitrates from a single sample of potable, mineral, or underground water. Nitrites were first determined upon the anodic polarization of a graphite electrode in a sodium sulfate supporting electrolyte. Next, ascorbic acid and a copper salt were added, and the solution was acidified to an optimum pH value. A copper electrode was formedin situ, and the nitrate signal was recorded as the first derivative using cathodic sweep. The procedure does not require sample preparation or oxygen removal from the solution with a nitrogen flow. The copper–graphite electrode was regenerated electrochemically in the same solution. The analytical range for nitrite ions was 0.2–10.0 mg/L in the presence of any amount of nitrates. Nitrates were quantitatively determined in the range 0.5–5 mg/L. Common cations and anions in waters did not interfere with the determination. The procedure is suitable for the analysis of potable, mineral, underground, and surface waters. The procedure was verified by the added–found method and by the photometric procedure GOST (State Standard) 18826-73.     

Analytical density-dependent representation of Hartree—Fock atomic potentials

A procedure to represent atomic electron charge densities [L. Fernandez Pacios, J. Phys. Chem., 95 , 10653 (1991); J. Phys. Chem., 96 , 7294 (1992)] is here generalized to obtain simple analytical functions for potential energy contributions. Based upon suitable functions to describe atomic electron densities in a physically meaningful form, the procedure is developed to define density-dependent analytical expressions for the electrostatic (classical) and exchange (quantum) potentials by means of proper approximate functionals. Calculations of correlation energies by using various density-functional approaches are also performed. The whole scheme is used to represent Hartree–Fock limit atomic wave functions by Clementi–Roetti. This way, a set of analytically simple, nonbasis set-dependent functions are defined with the aim to be further implemented in energy decomposition schemes for molecular interactions studies using atomic instead of electronic building blocks. © 1993 John Wiley & Sons, Inc.     

Analytical SPLITT cell fractionation: Linearity and resolution study

In this paper the analytical SPLITT (split flow thin cell) procedure is used to characterize the percentage composition of micronic polydisperse particulate samples at a given cut‐off size. The linearity and resolution of the separation method have been tested using specifically prepared starch samples, in order to compare the analytical process with two continuous (preparative) SPLITT procedures. Linearity has been checked by injecting a series of suspensions (at different concentrations) under five different flow rate conditions. Retrieval factors F were evaluated to verify the relative amount of sample exiting the cell outlets. The effective resolution has been assessed by inspecting the SPLITT fractions with an optical microscope, counting the granules, and evaluating the percentage of granules of expected size. It has been found that the resolution is very good (around 90%) and independent of sample distribution. It is seen from the comparison that in the analytical SPLITT mode sample resolution is usually around 85–90% and it is significantly better than that of the continuous SPLITT modes, thus making the analytical mode valuable in characterizing polydisperse samples. The method was tested for the characterization of a commercial starch sample.     

Accurate Theoretical Study of LiS Radical and Its Singly Charged Cation and Anion in their Ground Electronic State

Potential energies of LiS(²Π), LiS^-(¹Σ⁺) and LiS⁺(³Σ^-) are calculated by using the multireference configuration interaction method including Davidson correction and the augmented correlation-consistent basis sets aug-cc-PV(X+d)Z (X=T, Q). Such obtained potential energies are subsequently extrapolated to the complete basis set limit. Both the core-valence correction and the relativistic effect are also considered. The analytical potential energy functions are then obtained by fitting such accurate energies utilizing a least-squares fitting procedure. By using such analytical potential energy functions, we obtain the accurate spectroscopic parameters, complete set of vibrational levels and classical turning points. The present results are compared well with the experimental and other theoretical work.     

Simultaneous square wave anodic stripping voltammetric determination of Cr, Pb, Sn, Sb, Cu, Zn in presence of reciprocal interference: application to meal matrices

An analytical procedure for simultaneously determining chromium(VI), lead(II), tin(II), antimony(III), copper(II) and zinc(II) by square wave anodic stripping voltammetry (SWASV) in matrices involved in foods and food chain as wholemeal, wheat and maize meal is described.The digestion of each matrix was carried out using a concentrated HCl–HNO₃–H₂SO₄ acidic attack mixture. Dibasic ammonium citrate buffer solution pH 6.5 was employed as the supporting electrolyte. The voltammetric measurements were carried out using, as working electrode, a stationary hanging mercury drop electrode (HMDE) and a platinum electrode and an AgAgClKCl_sat electrode as auxiliary and reference electrodes, respectively. The analytical procedure was verified by the analysis of the standard reference materials Wholemeal BCR-CRM 189, Wheat Flour NIST-SRM 1567a and Rice Flour NIST-SRM 1568a.For all the elements in the certified matrix, the precision as repeatability, expressed as relative standard deviation (s_r) was of the order of 3–5%. The accuracy, expressed as relative error (e) was generally of the order of 3–6%, while the detection limits were lower than 0.123 μg/g.In the presence of reciprocal interference, the standard addition method considerably improved the resolution of the voltammetric technique.Once set up on the standard reference materials, the analytical procedure was transferred and applied to commercial meals sampled on market for sale. A critical comparison with spectroscopic measurements is also discussed.