Ion-pair Technique Research Articles

Dextran-Based Nanoparticles for Encapsulation of Ciprofloxacin

Key success for regenerative endodontics is an effective removal of bacteria inside the root canal during the treatment. Ciprofloxacin (CIP) is one of the triple antibiotics commonly used as the root canal medicament. However, the rapid clearance of antibiotics causes bacterial reinfection. Nanoparticles (NPs) provide an alternative approach for antibiotics delivery system to improve the drug stability and release control. In the previous study, modified dextran was successfully formed the ester linkage with vinyl decanoate via lipase-catalyzed transesterification. The amphiphilic dextran, dextran-decanoate (Dex-D), has been synthesized with the degree of substitution of 83-88% and were applied for CIP-loaded nanoparticles. The suitable technique for producing antibiotic carriers considering by size, shape, and drug encapsulation efficiency was investigated in this work. The preparation methods were compared between nanoprecipitation and solid-in-oil-in-water (s/o/w) ion pairing technique. We found that the obtained Dex-D nanoparticles had stable monodispersed with spherical shape in both techniques. However, Dex-D nanoparticles formed by s/o/w ion pairing technique provided smaller size with better encapsulation efficiency. The antimicrobial activity of CIP-loaded Dex-D nanoparticles against oral pathogens showed satisfactory outcome with the MIC equal to 0.7 μg/mL. Also, the compatibility of nanoparticles and dental stem cells was observed in this work.

Hydrophobic ion-pairing assembled liposomal Rhein with efficient loading for acute pancreatitis treatment

Aim The present study aimed to develop liposomal Rhein by employing a hydrophobic ion-pairing technique (HIP) for improved pancreatitis therapy. Methods F127 modified liposomal Rhein (F127-RPC-Lip) was prepared using a two-step process consisting of complexation first, followed by a film-ultrasonic dispersion step. The drug-phospholipid interaction was characterised by FT-IR and P-XRD. Particle size and morphology were investigated using DLS and TEM, respectively. Biodistribution and therapeutic efficacy of F127-RPC-Lip were evaluated in a rat model of acute pancreatitis. Results F127-RPC-Lip achieved efficient drug encapsulation after complexation with lipids through non-covalent interactions and had an average hydrodynamic diameter of about 141 nm. F127-RPC-Lip demonstrated slower drug release (55.90 ± 3.60%, w/w) than Rhein solution (90.27 ± 5.11%) within 24 h. Compared with Rhein, F127-RPC-Lip exhibited prolonged systemic circulation time, superior drug distribution, and attenuated injury in the pancreas of rats post-injection. Conclusions HIP-assembled liposomes are a promising strategy for Rhein in treating pancreatitis.

Probing the Role of Ion-Pair Strategy in Controlling Dexmedetomidine Penetrate Through Drug-in-Adhesive Patch: Mechanistic Insights Based on Release and Percutaneous Absorption Process.

The purpose of present study was to develop a controlled release drug-in-adhesive patch for transdermal delivery of dexmedetomidine (Dex) using ion-pair technique. Based on the in vitro transdermal experiment, the role of ion-pair on the Dex release behavior and percutaneous absorption process was also investigated. Fourier transform infrared spectroscopy (FTIR), molecular modeling, differential scanning calorimetry (DSC), and rheological test were conducted to probe the effect of ion-pair on the Dex release from patch. Besides, the tape stripping test, attenuated total reflectance Fourier transform infrared (ATR-FTIR), and molecular simulation were carried out to elaborate the action of ion-pair on the Dex percutaneous permeation process. Results showed that the optimized patch prepared with Dex-salicylic acid (SA) showed zero-order skin permeation profile within 24h; Dex-SA had greater hydrogen bonding formation potential with pressure sensitive adhesive (PSA) than Dex, which resulted in the decrease in the formation ability of free volume of PSA and the increase with the improvement of mechanical strength and chain stiffness of PSA and thus controlled the release rate of Dex from transdermal patch. Besides, the physicochemical properties of Dex such as molecular weight and octanol/water partition coefficient were changed after forming ion-pair with SA, which decreased the permeation ability of Dex. In conclusion, a controlled release drug-adhesive patch for Dex was developed and the mechanism study of ion-pair on the Dex release and percutaneous permeation process was proposed at molecular level.

LC-MS/MS measurements of urinary guanidinoacetic acid and creatine: Method optimization by deleting derivatization step

BackgroundCerebral Creatine deficiency syndromes (CCDS) include three hereditary diseases affecting the metabolism of creatine (Cr): arginine glycine amidinotransferase deficiency, guanidinoacetate methyltransferase deficiency and disorders of creatine transporter. These pathologies cause a brain creatine deficiency responsible of non-specific neurological impairments with mental retardation. LC-MS/MS measurements of guanidinoacetic acid (GAA) and creatine in urine and plasma are an important screening test to identify the deficit. Analysis of this polar and basic molecules not hold on standard column requires a derivatization step to butyl-esters. To overcome this long and fastidious derivatization, an ion pairing (IP) method was chosen in this study. MethodIP method was validated using Comité francais d'accréditation (COFRAC) recommendations. Then, urine GAA and creatine of 15 patients with a CDS deficiency suspected were tested y LC-MS/MS using IP technique, and performances were assessed with reference laboratory method (butylation method). Moreover, references values were suggested y the study of 100 urines samples of healthy patients. ResultsThe method developed provided a good accuracy and precision with intra and inter-day coefficients of variation (CVs) <15%. The curve was linear for the biological and pathological concentrations. The comparison with the reference method did not reveal any significant difference for analytical performances but showed a simplification of the preparation of samples. ConclusionThe use of IP technique that we have developed demonstrated a good correlation with the butylation method. Moreover, this new method not only allows a simplification of the technique, but also decreases in run time.

An Improved, Rapid, and Sensitive Ultra-High-Performance Liquid Chromatography-High-Resolution Orbitrap Mass Spectrometry Analysis for the Determination of Highly Polar Pesticides and Contaminants in Processed Fruits and Vegetables.

A rapid, specific, and sensitive method based on quick polar pesticide extraction and ultra-high-performance liquid chromatography coupled to high-resolution mass spectrometry with an Orbitrap analyzer was evaluated. Usually, pesticides were analyzed individually using derivatization or ion-pairing techniques and detection by ion chromatography. We identified and simultaneously quantified 6 highly polar compounds (glyphosate, aminomethyl phosphonic acid (AMPA), phosphonic acid, fosetyl-Al, chlorate, and perchlorate) in 83 processed fruits and vegetables as well as 15 infant foods. Isotopically labeled internal standards 18O4-perchlorate, 18O3-chlorate, and 13C215N-glyphosate were applied to quantify five polar compounds and to compensate for any factor affecting the recovery rates. Only AMPA was quantified using a standard addition approach to compensate for matrix effects. This analytical methodology is fast and reliable, and it is also able to satisfy the strict requirements of infant food analysis.

Investigate the control release effect of ion-pair in the development of escitalopram transdermal patch using FT-IR spectroscopy, molecular modeling and thermal analysis

The aim of this study was to develop a controlled release drug-in-adhesive patch containing escitalopram (ESP) using ion-pair technique. Special attention was paid on the mechanism of how counter ion controlled the release of ESP. Five organic acids were chosen as the counter ions. Formulation factors including adhesive matrix, drug loading and permeation enhancers were investigated through in vitro experiments using rat skin and the optimized patch was evaluated using in vivo pharmacokinetic study. Drug-counter ion-PSA interactions were characterized by FT-IR, molecular modeling and DSC at molecular level. The optimized patch prepared with ESP-BA showed zero-order skin permeation profile and a satisfied permeation amount of three days (1059±104.9μg/cm2) in vitro, which also showed a steady-state drug plasma concentration lasting 36h in vivo and the Cmax was significantly controlled compared with the control group. The controlled release of ESP was attributed to the interactions among ESP-counter ion-PSA by hydrogen bonding, and counter ion enhanced the interaction between ESP and PSA molecule, which acted as a “bridge” between them. In conclusion, a controlled release ESP transdermal patch was developed and a novel insight of ion-pair controlled release was proposed at molecular level.

Ion-pair dispersive liquid–liquid microextraction solidification of floating organic droplets method for the rapid and sensitive detection of phenolic acids in wine samples using liquid chromatography combined with a core–shell particle column

This study describes a novel sample preparation method for extraction of phenolic acids from wine using ion pair dispersive liquid–liquid microextraction based on the solidification of a floating organic droplet (IP-DLLME-SFO). The ion-pairing technique combined with DLLME-SFO dramatically enhanced the extraction efficiency for very polar phenolic acids, such as gallic acid and protocatechuic acid, which could not be extracted by DLLME-SFO in the absence of an ion-pairing reagent. The effects of the parameters that can affect the extraction efficiency were systematically investigated, including the type and concentration of ion-pairing reagent, type and volume of extraction and dispersive solvents, extraction time, sample pH, and ion strength. The method linearity was constructed in the range of 0.01–15μg/mL, and the sensitivity expressed as limit of detection was as low as 10ng/mL. The method that we developed was applied for the analysis of commercial wine samples, revealing different levels of phenolic acids among these products.

Determination of selected perfluorinated compounds and polyfluoroalkyl phosphate surfactants in human milk

Polyfluoroalkyl phosphate surfactants (PAPS) are used on food contact paper to impart oil/grease resistance and have been shown to be able to migrate into food. The biotransformation of the congeners belonging to this class of compounds is considered to be a potential source of perfluorinated carboxylic acids (PFCAs). In this study, two methods were developed for the determination of seven perfluorinated compounds (PFCs) and eight polyfluorinated disubstituted phosphate surfactants (diPAPS) in human milk. PFCs were extracted from milk using an ion-pairing technique; while the diPAPs extraction involved a sample clean up using solid phase extraction. Analyses of all compounds in this study were performed by liquid chromatography–tandem mass spectrometry (LC–MS/MS). Of the seven PFCs analyzed in human milk, only perfluorooctanoic acid (PFOA) was detected in eleven out of thirteen (85%) individual human milk samples analyzed, with a concentration range of <0.072 to 0.52ngmL−1. Four diPAPS were detected and quantified in human milk samples. Eight out of thirteen samples contained 4:2 diPAP with a concentration range of <0.01–0.26ngmL−1; 6:2 diPAP was detected in five samples with a concentration range of <0.01–0.14ngmL−1; 8:2 diPAP was detected in only three samples with concentrations of 0.21, 0.27, and 0.30ngmL−1. The 10:2 diPAP was quantified in seven milk samples, with concentration range of <0.01–0.83ngmL−1. No correlation was established between PFCAs and PAPS levels in this small sample size. To the best of the authors’ knowledge, this is the first study to report the presence of PAPS in human milk.

Determination of clemastine hydrogen fumarate, desloratadine, losartan potassium and moxepril HCl through binary complex formation with eosin

A simple and sensitive spectrophotometric method has been established for the determination of clemastine hydrogen fumarate (I), desloratadine (II), losartan potassium(III) and moxepril HCl(IV) based on binary complex formation with eosin. The method does not involve solvent extraction through the use of a non-ionic surfactant (methylcellulose). The color of the produced complex was measured at 552, 549nm for (I), (II) while was measured at 540nm for (III) and (IV). Appropriate conditions were established for the color reaction between eosin and the studied drugs to obtain maximum sensitivity. Under the proposed conditions, the method is applicable over concentration range of 1.25–11.25, 0.31–2.81, 2.5–20 and 1.25–15μg/ml for (I), (II), (III) and (IV), respectively. The molar absorptivity (ε), sandell sensitivity, detection (LOD) and quantitation limits (LOQ) are calculated. Unlike other reported ion-pair techniques, the suggested methods have the advantage of being applicable for the determination of the four drugs in their pharmaceutical dosage forms without prior extraction with excellent recoveries.

Mechanisms of ESI-MS Selectivity and Sensitivity Enhancements When Detecting Anions in the Positive Mode Using Cationic Pairing Agents

Recently, we have shown that dilute multivalent cationic reagents can be paired with analyte anions in ESI-MS, thereby allowing them to be detected in the positive mode at very low limits of detection. However, there can be differences in the efficiency of this technique depending on the nature of the cationic pairing agent and the anion being analyzed. In this study, three dicationic ion-pairing agents and four singly charged anionic species were examined in a series of experiments to elucidate the mechanism of action that allows for such sensitive detection and the profound differences in the selectivity of this ion-pairing method. The binding constants for the dication/anion complexes were determined by NMR and ESI-MS. The results indicated that the binding of these species is greatly enhanced as they move from the solution phase to the gas phase. Furthermore, surface tension measurements for the complexes were performed. This test revealed that, as the dication pairs with the anion, it creates a surface-active species within the ESI droplet. This is determined to be one of the major factors that leads to the overall sensitivity enhancement. This has led to a better understanding of how this ion-pairing technique produces unprecedented limits of detection for anions and why there are selectivity differences in pairing agents of different structures.

Book Review: Ion-Pair Chromatography and Related Techniques

Book Review: Ion-Pair Chromatography and Related Techniques

Quantification of lysophosphatidic acids in rat brain tissue by liquid chromatography–electrospray tandem mass spectrometry

Lysophosphatidic acid (LPA) is a lipid mediator with multiple biological functions. A highly selective and sensitive liquid chromatography–tandem mass spectrometry (LC/MS/MS) method was developed for the determination of LPAs (16:0 LPA, 18:0 LPA, 18:1 LPA, 20:4 LPA) in rat brain cryosections. After partitioning the LPAs from other lipophilic material present in the tissue with a liquid–liquid extraction, a reversed-phase column and ion pair technique was used for separating analytes with a gradient elution. An internal standard (17:0 LPA) was included in the analysis. Detection and quantification of the LPAs were carried out with a triple quadrupole mass spectrometer using negative electrospray ionization (ESI) and multiple reaction monitoring (MRM). The artificial formation of LPAs from lysophosphatidylcholines during the sample preparation procedure and instrumentation was carefully studied during the method development. The method was validated; acceptable selectivity, accuracy, precision, recovery, and stability were obtained for concentrations within the calibration curve range of 0.02–1.0 μM for LPAs. The quantification limit of the assay was 54 fmol injected into column for each LPAs. The method was applied to comparative studies of LPA levels in rat brain cryosections after the various chemical pre-treatments of the sections.

Fluorescent-Dye-Doped Sol−Gel Sensor for Highly Sensitive Carbon Dioxide Gas Detection below Atmospheric Concentrations

Optical fluorescence sol-gel sensors have been developed for the detection of carbon dioxide gas in the 0.03-30% range with a detection limit of 0.008% (or 80 ppm) and a quantitation limit of 0.02% (or 200 ppm) CO(2). Sol-gels were spin-coated on glass slides to create an organically modified silica-doped matrix with the 1-hydroxypyrene-3,6,8-trisulfonate (HPTS) fluorescent indicator. The luminescence intensity of the HPTS indicator (513 nm) is quenched by CO(2), which protonates the anionic form of HPTS. An ion pair technique was used to incorporate the lipophilic dye into the hydrophilic sol-gel matrix. TiO(2) particles (<5 microm diameter) were added to induce Mie scattering and increase the incident light interaction with the sensing film, thus increasing the signal-to-noise ratio. Moisture-proof overcoatings have been used to maintain a constant level of water inside the sensor films. The optical sensors are inexpensive to prepare and can be easily coupled to fiber optics for remote sensing capabilities. A fiber-optic bundle was used for the gas detection and shown to work as part of a multianalyte platform for simultaneous detection of multiple analytes. The studies reported here resulted in the development of sol-gel optical fluorescent sensors for CO(2) gas with sensitivity below that in the atmosphere (ca. 387 ppm). These sensors are a complementary approach to current FT-IR measurements for real-time carbon dioxide detection in environmental applications.

Design of high payload PLGA nanoparticles containing melittin/sodium dodecyl sulfate complex by the hydrophobic ion-pairing technique

The water-soluble peptide, melittin, was modified with an anionic agent, sodium dodecyl sulfate by hydrophobic ion-pairing. Investigations showed that the formed complex was very soluble in organic solvent, especially, in dimethylsulfoxide and dehydrated alcohol. Furthermore, the physiochemical properties of the complex in the solid state or in an aqueous medium were characterized using octanol/water partition measurement, Fourier transform infrared spectroscopy, and differential scanning calorimetry. The complex was formulated into poly(d,l-lactide–co-glycolide acid) nanoparticles by an emulsion solvent diffusion method. It was found that the nanoparticles of about 130 nm in size can be produced with a high encapsulation efficiency, and the entrapment of nanoparticles prepared with the formed complex increased from about 50% to nearly 100% compared with that for pure melittin. Moreover, the growth inhibitory effects of modified melittin and melittin-loaded nanoparticles in breast cancer MCF-7 cells were not changed comparing with free melittin as determined by (3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl tetrazolium bromide) assay.

Enhanced detection of sulfated glycosylation sites in glycoproteins

We demonstrate a method that enhances the mass spectral signal of mono- and disulfated glycopeptides, present in glycoproteins that contain many other nonsulfated glycoforms. This method utilizes the tripeptide Lys-Lys-Lys as an ion-pairing reagent to complex selectively to sulfated species, and enhance their ion signal. The method is applied to the analysis of glycopeptides released from the enzymatic digestion of ovine luteinizing hormone. In this analysis, a disulfated glycopeptide is identified that was previously not detectable by MS assays, and a monosulfated glycoform, present at less than 1% abundance, is identified without any separation or enrichment of these species prior to analysis. In addition to enhancing the ion signal of sulfated glycopeptides, the ion-pairing technique is useful in obtaining structural information about the sulfated species.

Low-cost noninvasive optical CO2 sensing system for fermentation and cell culture

High-throughput bioprocessing is a very promising technique for bioprocess development and optimization because of its high efficiency. The key to its development has been the availability of simple and inexpensive sensors to monitor the bioprocesses conducted in its small-scale bioreactors. Here we report on a low-cost noninvasive CO2 sensing system suitable for any transparent vessel. The system was composed of a CO2 sensing patch, a coaster, an interface, and a computer. The sensing film was prepared using the ion-pair technique. The coaster was a small self-made device with necessary optics and electronics for ratiometric measurements with a component cost of less than dollar 100. Results show that the system was stable and reliable despite its simplicity and low cost. The sensitivity of the CO2 sensing system was not affected by pH, media type, or temperature. It was shown to be stable for at least 10 days, long enough for most bioprocesses.

Reversed-phase liquid chromatography on an amide stationary phase for the determination of the B group vitamins in baby foods

A liquid chromatographic method for the separation and determination of several water-soluble vitamins of the B group is proposed. The procedure is based on the use of a new amide-based stationary phase, which avoids the need of using the ion-pair technique, leading to narrower peaks and a simpler mobile phase. Analyses were performed by gradient elution with acetonitrile–phosphate buffer as mobile phase and using a photodiode array detector. Specificity was demonstrated by the retention characteristics, UV spectra and by comparing the peak purity index with commercial standards. Linearity, precision, recovery and sensitivity were satisfactory. The vitamins are extracted from the baby food using a single digestion with hydrochloric acid followed by enzymatic digestion with taka-diastase. The method was successfully applied to the determination of nine vitamins: thiamine, riboflavin, nicotinamide, nicotinic acid, pyridoxine, pyridoxal, folic acid, cyanocobalamine and inosine in different baby foods as infant formulas, cereals and fruit products. Validation was performed using two certified reference materials.

High performance liquid chromatography and capillary electrophoresis determination of sanguinarine in biological matrices

AbstractHPLC and CE methods were employed to determine the quaternary benzo[c]phenanthridine alkaloid sanguinarine in biological matrices (rat hepatocytes, human gingival fibroblasts, feed, porcine faeces, body fluids and tissues). HPLC was carried out on a C18 column using gradient elution and ion pairing techniques with 1‐heptanesulfonic acid as ion pairing agent under acidic conditions. The detection limit for fluorimetric detection at λex = 327 nm and λem = 577 nm was 3 nM sanguinarine. CE analyses were performed in 50 mM phosphate‐Na buffer pH 2.5, with 150 mM SDS used for pre‐concentration by the sweeping effect. This experimental configuration allows injecting the total capillary length with sanguinarine sample. The detection limit for UV detection at 285 nm was 12 nM. Both methods are suitable for analysing submicromolar quantities of sanguinarine in biological materials. The HPLC method is more sensitive than CE because it uses fluorescence detection.

Comparison of ion-pair and amide-based column reversed-phase liquid chromatography for the separation of thiamine-related compounds

Two reversed-phase chromatographic methods for the separation of thiamine and related compounds are compared. The first procedure is based on the ion-pair technique using an octadecylsilica column, while the second uses a new amide-based stationary phase, which avoids the need to form ion-pairs, leading to narrower peaks and a simpler mobile phase. Analyses were performed by gradient elution and a photo-diode array was used for detection. Specificity was demonstrated by the retention characteristics, UV spectra and by comparing the peak purity index with commercial standards. The procedures were applied to the determination of thiamine-related compounds in pharmaceutical preparations and urine. No preliminary sample treatment was required.

Development of an efficient system for the separation of indole alkaloids by high performance liquid chromatography and its applications.

An efficient system for the analysis of indole alkaloids by HPLC on a reversed-phase column using an ion pair technique is described. The optimised chromatographic conditions allowed the successful separation of 22 standard monoterpenoid indole alkaloids (including some isomers) and tryptamine. The described HPLC system was applied to the analysis of alkaloids in intergeneric somatic hybrid cell cultures of Rauvolfia serpentina x Rhazya stricta.