Sequential Determination of Inorganic Cations and Anions in Cerebrospinal Fluid by Microchip Electrophoresis

Analysis of inorganic ions in cerebrospinal fluid (CSF) is used mainly in the diagnostics of central nervous system diseases, such as Alzheimer’s disease or multiple sclerosis. A new analytical method for fast determination of inorganic cations (ammonium, calcium, magnesium, sodium and potassium) and anions (chloride, sulfate, nitrite and nitrate) in CSF on an electrophoretic microchip was developed in this context. Zone electrophoresis (ZE) separations were performed on the microchip with coupled channels (CC) and contact conductivity detection. Two different propionate background electrolytes were used for the sequential determination of cations at pH 3.1 and anions at pH 4.3. ZE was used for the determination of cationic constituents while ZE–ZE approach was employed for the determination of chloride in the first separation channel on the CC microchip and other anionic micro-constituents in the second channel. LOD values were in the range of 0.003–0.012 mg L^?1 and 0.019–0.047 mg L^?1 for cations and anions, respectively. Repeatability of migration time was up to 1.2 % for both cations and anions. Repeatability of peak area ranged from 0.3 to 5.6 % for cations and from 0.6 to 6.0 % for anions. Recovery of both cations and anions was in the range 90–106 %. CSF samples were only diluted appropriately without other sample pretreatment prior to analysis. Developed sequential method is suitable for fast determination of the studied cations and anions in CSF with total analysis time <15 min.     

Characterization of Porous Graphitic Carbon LC Phase with some Carbohydrate Derivatives

Stereoselective CE method for investigations of pharmacokinetics of ketoprofen enantiomers (KTP) in patients taking also other drugs is proposed, to establish relation between levels of KTP enantiomers in blood and synovial fluid of patients with rheumatoid arthritis. Resolution of the analytes was obtained in silica capillary filled with chiral selector-heptakis 2,3,6-tri-O-methyl–β-cyclodextrin in triethanolamine-phosphate buffer. Calibration curves for enantiomers in plasma and synovial fluid were linear in the range of 0.25–50.0 mg L⁻¹, but 1.0–250.0 mg L⁻¹ in urine. Concentrations of KTP enantiomers in synovial fluid measured at 4 h after the administration of a tablet with racemic KTP were insignificantly greater [(−)-R = 1.07 ± 0.66; (+)-S-KTP = 1.13 ± 0.65 mg L⁻¹] than in plasma [(−)-R = 0.86 ± 0.37; (+)-S-KTP = 0.96 ± 0.42 mg L⁻¹]. The validated method has been successfully applied for the determination of KTP enantiomers in biological fluids of patients with rheumatoid arthritis.

     

Concurrent determination and separation of inorganic cations and anions in microchip electrophoresis with precisely controlled high‐voltage

An improved method for the concurrent determination and separation of cations and anions by microchip electrophoresis with capacitively coupled contactless conductivity detection (ME‐C⁴D) is described. Two kinds of microchip structures were designed. The first microchip has a long bent separation channel. And for the defects of the first microchip, the second microchip with a Y‐type separation channel has been proposed. The background electrolyte (BGE) composed of 20 mm His/MES and 0.01 mm CTAB was optimized for inhibiting the electroosmotic flow (EOF). Due to the low electroosmotic flow, the cations and anions migrate in opposite directions and can be separated from each other. With the precisely controlled high‐voltage, cations and anions can be migrated in microchannels according to our requirements and sequentially detected by a C⁴D detector built in‐house. Samples containing K⁺, Na⁺, Li⁺, Cl⁻, F⁻ and PO₄³⁻ were analyzed simultaneously in a single run (within 140 s) by both methods. The reproducibility obtained by both methods remained below 5% for migration time and within 3.5–9.1% for peak areas. The proposed concurrent determination methods are inexpensive, simple, fast, ease of operation, high degree of integration.     

GC–MS Method Development for the Analyses of Thiophenes from Solvent Extracts of Tagetes patula L

A method for isotachophoretic determination of potassium and ammonium cations in fertilizers and silage was developed. A capillary of 0.4 mm i.d. and 100 mm effective length made of fluorinated ethylene–propylene copolymer was filled with an electrolyte system consisting of 10 mmol L⁻¹ RbOH + 0.1% (w/v) hydroxyethylcellulose, adjusted to pH 9.0 with l-histidine (leading electrolyte) and 10 mmol L⁻¹ lithium citrate (terminating electrolyte). Using contactless conductivity detection, the calibration curves in the tested concentration range up to 0.5 mmol L⁻¹ were linear for both cations. The concentration detection limits for potassium and ammonium were 2.9 and 2.7 μmol L⁻¹, respectively. RSD values of step lengths (n = 6) were 1.3% for potassium and 1.5% for ammonium. The separation time was about 20 min. Similar results were obtained with cesium cation used as the leading ion, however, in the system with rubidium better resolution of other cations present in tested matrices was reached. The elaborated method is simple to perform, sufficiently sensitive and accurate and can be recommended as an alternative procedure to the methods used so far for the determination of potassium and ammonium.

     

Residue Analysis of Propionylbrassinolide in Fruit and Vegetables by GC–MS

A rapid and simple method for the determination of propionylbrassinolide residues in tomatoes, apples and grapes using GC–MS is reported. Samples were extracted with acetonitrile, and the extracts were analyzed without any further clean-up. The results showed good linearity (r ² > 0.99) with standard solutions over the concentration range of 0.5–50 mg L⁻¹. The LODs and LOQs of propionylbrassinolide were 0.15 and 0.5 mg kg⁻¹ in all samples. Recoveries were in the range of 81.9–111.2%, with corresponding RSDs of 4.6–12.9% for three fortified levels. Intra- and inter-day RSDs were in the ranges of 1.5–14.2% and 5.3–15.6%. It was demonstrated that the proposed method is simple and efficient, and particularly suitable for detecting propionylbrassinolide residues in fruit and vegetables.

     

A Simple Method for Determination of Homologue Imidazolium Cations in Ionic Liquids Using IC with Direct Conductivity Detection

An investigation was carried out into the fast determination of five homologue imidazolium cations in ionic liquids by ion chromatography using a cation-exchange column and direct conductivity detection. Ethylenediamine, complex organic acid (citric acid, oxalic acid and tartaric acid) and organic modifiers (acetonitrile) were used as mobile phase. The influences of the eluent types, eluent concentration, eluent pH and column temperature on separation of the cations were discussed. Simultaneous separation and determination of the five homologue imidazolium cations in ionic liquids were achieved under an optimum condition. The optimized mobile phase was consisted of 0.25 mmol L^?1 ethylenediamine + 0.5 mmol L^?1 citric acid + 3% acetonitrile (v/v) (pH 4.1), set at a flow rate of 1.0 mL min^?1. The column temperature was 40 °C and detection limits were obtained in the range of 1.1–45.6 mg L^?1. The relative standard deviations of the chromatographic peak areas for the cations were <3.0% (n = 5). This method was successfully applied to separate imidazolium cations in ionic liquids produced by organic synthesis. The recoveries of spiked components were 92.5–101.9%.     

Quantitative Determination of Hyponitrite and Hyponitrate by Ion Chromatography

A simple, sensitive and reliable method for the rapid determination of hyponitrite and hyponitrate (Angeli’s salt) in alkaline media, is presented where both species are relatively stable. The method is based on the separation of the two anions by an anion exchange column and thereafter UV spectrophotometric detection at 248 nm. The calibration curves were linear over the concentration range of 0.4–100 mg L^?1, whereas the detection limit was found to be 50 μg L^?1 for hyponitrite and 100 μg L^?1 for hyponitrate. Under these conditions, the determination of nitrate and nitrite is also possible.     

An On-line Admicellar SPE-HPLC System Using CTAB-Modified Zeolite NaY as Sorbent for Determination of Carbamate Pesticides in Water

Zeolite NaY modified with cetyltrimethylammonium bromide (CTAB) was considered for extraction/preconcentration of carbamate pesticides using an on-line SPE-HPLC system. The simultaneous determination of carbamate pesticides, including aldicarb, carbofuran, carbaryl, isoprocarb, methiocarb and promecarb, was performed by HPLC–UV using a LichroCART RP-18 column with gradient elution of methanol and 0.1 % acetic acid. The sorbent presented admicelles of CTAB on its surfaces and exhibited a sorption capacity of 180–18,600 mg kg⁻¹ sorbent, which could be re-modified for at least five extraction cycles. The quantitative retention of target pesticides on the admicellar sorbent involved hydrophobic and π-cation interaction, while pesticides were eluted from the admicellar SPE column using only 750 μL of methanol. LODs and LOQs of the proposed method were 0.005–140 and 0.02–600 μg L⁻¹, respectively. The analytes were effectively concentrated with the enrichment factors between 5 and 551. The developed on-line admicellar SPE-HPLC system was successfully applied to the determination of carbamate pesticides in ten environmental water samples from different sources. Recoveries of spiked samples at a concentration of 0.1–5 mg L⁻¹ ranged from 77 to 111 %.

     

Determination of Imidazolium Ionic Liquid Cations by Ion-Pair Chromatography Using a Monolithic Column and Direct Conductivity Detection

Determination of four imidazolium ionic liquid cations by ion-pair chromatography was carried out using direct conductivity detection. Chromatographic separations were performed on a silica-based monolithic column with 1-heptanesulfonic acid sodium + acetonitrile + citric acid as eluent. Carbon number rule and influence of acetonitrile on the retention of imidazolium cations were discussed. Detection limits (S/N = 3) for the cations were 2.1–55.9 mg L^?1. Relative standard deviations (RSD, n = 5) for peak areas were less than 3.0%. The method has been successfully applied to the determination of two ionic liquids synthesized by organic chemistry lab.     

Determination of Trenbolone Acetate in Cattle Feeds by a Flow Injection Chemiluminescence Method

A flow injection chemiluminescence (CL) method is described for the determination of trenbolone acetate based on the CL generated during its reaction with KMnO₄ in acidic medium. The CL intensity is greatly enhanced by alizarin yellow R. The CL intensity is linear with trenbolone acetate concentration in the range 0.1–100.0 mg L^?1 with a detection limit of 0.05 mg L^?1. The sample throughout is about 90 h^?1 and the relative standard deviation for 2.0 mg L^?1 trenbolone acetate solution is 1.5% (n = 11). The proposed method was applied to the determination of trenbolone acetate in cattle feeds.     

Automated Derivatization of Pharmaceutically Active Thiols Under Flow Conditions Using an o-Phthalaldehyde/Glycine Fluorogenic System and Sequential Injection Analysis

The present study reports a new automated, generic analytical method for the determination of the pharmaceutically active thiols captopril (CAP), N-acetylcysteine (NAC), and D-Penicillamine (PEN). The proposed sequential injection (SI) method is based on the on-line reaction of the selected thiols with o-phthalaldehyde/glycine in alkaline medium (pH = 9.5) to form highly fluorescent iso -indole derivatives. The effect of all major flow and reaction variables was investigated, while validation was carried out in terms of linearity/range (2.5–7.5 mg L^?1), limits of detection (1.6–2.3 µ g L^?1), quantification (5.3–7.7 µ g L^?1), precision (0.9–1.2% for repeatability and 3.5–4.9% for intermediate precision), selectivity, and accuracy (98.3–102.8%). The developed method was applied to the assay and dosage uniformity tests of various pharmaceutical formulations at a sampling rate of 73 h^?1.     

Sequential Injection Chemiluminescence Methodology for Ozone Evaluation

A sequential injection methodology with chemiluminescence detection for the evaluation of residual ozone in waters is presented. The procedure is based on the reaction between luminol and ozone without catalysts.

Linear calibration plots were obtained for ozone concentrations between 0.05 and 2.0 mg L^?1, with a detection limit of 0.04 mg L^?1.

The developed methodology was applied to the determination of residual ozone in ozonized waters and the results complied with those furnished by the spectrophotometric reference procedure (relative deviations < 6.3%). The method exhibited good precision (RSD < 3.5%) and the sampling rate was about 140 determinations per hour.     

Fast Determination of Phenolic Compounds in Brazilian Wines from Vale do São Francisco Region by CE

Six phenolic compounds were separated and determined by capillary zone electrophoresis in red wine from Brazil’s region Vale do São Francisco with total analysis time of 12 min. The limit of detections varied from 1.59 to 2.24 mg L^?1. The relative standard deviations (for n = 6) varied from 0.28 to 3.50 %. The red wine samples analyzed were bought in the local market and the phenolic compound recoveries were in the range of 98–101 %. The concentrations of gallic acid in the samples of wines varied from 16.0 to 42.0 mg L^?1, caffeic acid (3.16–5.18 mg L^?1), syringic acid (5.73–13.0 mg L^?1), kaempferol (2.32–4.33 mg L^?1), quercetin (1.68–4.03 mg L^?1), myricetin (7.52–25.1 mg L^?1). The concentrations found agree with data reported in the literature.     

Sequential Injection Magneto Chromatography Determination of Non-Steroidal Anti-Inflammatory Drugs in Pharmaceutical Formulations

A magnetic separation method based on the use of magnetic silica as the stationary phase in sequential injection chromatography was used for simultaneous determination of nonsteroidal anti-inflammatory drugs (acetaminophen, naproxen, diclofenac, and ibuprofen) in tablets. The method is based on a thin layer paramagnetic stationary phase retained on the inner wall of a mini-column through the action of an external magnetic field. The influence of the variables involved was evaluated and the optimal conditions were found to be: a methyl-silica magnetic adsorbent was used as the stationary phase, the mobile phase was methanol-water (60:40, v/v), pH 2.5 adjusted with 98% phosphoric acid, a flow rate 0.60 ml min^?1, and UV detection at 225 nm. Under these conditions, the linear range of the calibration curve ranged from 3–6 mg L^?1 to 100 mg L^?1 with limits of detection ranging between 1 to 2 mg L^?1. The proposed method was validated by comparing the results obtained against those provided by high performance liquid chromatography; no significant differences were seen.     

Temperature-assisted ionic liquid-based dispersive liquid–liquid microextraction with following back-extraction for HPLC/UV–Vis determination of 3-indole acetic acid in pea plants

In this work, the ionic liquid (IL)[C₆mim][PF₆] was used as IL-based extractant for dispersive liquid–liquid microextraction, followed by back-extraction and HPLC/UV–Vis determination of 3-indole acetic acid (IAA) in pea plant. The effects of some crucial factors such as chemical structure and volume of IL, pH adjustment, dissolution temperature, extraction time, centrifugation time, and ionic strength of aqueous sample were studied. The linear range of the HPLC method for IAA quantification was 17.5 × 10^?2–36.8 mg L^?1. LOD, LOQ, method recovery, and preconcentration factor values were 0.170 mg L^?1, 0.175 mg L^?1, 98.3, and 40 %, respectively. The RSD for the suggested method was calculated as 0.93 % at 35.04 mg L^?1 of IAA and each IL phase was able to be reused for at least four DLLME/back-extraction cycles. To evaluate the applicability of the suggested method, IAA was determined in pea plant samples.     

Flow-Batch Method with a Sequential Injection System for Spectrophotometric Determination of Selenium(IV) in Selenium-Enriched Yeast Using o-Phenylenediamine

A precise, accurate, and reliable flow-batch spectrophotometric method for the determination of selenium (IV) was developed using o-phenylenediamine as a reagent with a sequential injection monosegmented flow system incorporating a simple heating unit. The reaction zones of selenium(IV) and o-phenylenediamine were mixed and heated in a chamber at 62°C for 5 minutes. The piaselanol complexes were then detected at a maximum absorption wavelength of 335 nm. In-line single standard calibration and standard addition procedures were developed employing the monosegmented flow technique. Under the optimized conditions, a linear calibration graph in a range of 0.1–4.0 mg L^?1 selenium (IV) was obtained with limits of detection and quantitation of 0.01 and 0.1 mg L^?1, respectively. Relative standard deviations were 2% [for both 0.1 and 0.5 mg L^?1 selenium (IV) (n = 11)]. A sample throughput of 2 h^?1 using four standard addition levels was achieved. The developed system was successfully applied to raw selenium-enriched yeast samples. The analyses performed by the developed method agreed well with those obtained from a standard inductively coupled plasma mass spectrometry method.     

Rapid Determination of Trifluoromethanesulfonate and p-Toluenesulfonate by Ion-Pair Chromatography Using a Reversed-Phase Silica-Based Monolithic Column: Application to the Analysis of Ionic Liquids

A method of ion-pair chromatography was developed on a reversed-phase silica-based monolithic column for the fast and simultaneous determination of trifluoromethanesulfonate (CF₃SO₃ ⁻) and p-toluenesulfonate (C₇H₇SO₃ ⁻). The analysis was performed using a mobile phase of tetrabutylammonium hydroxide + citric acid + acetonitrile on the Chromolith Speed ROD RP-18e column with direct conductivity detection. The effects of the eluent, column temperature and flow rate on the retention of the anions were investigated. The experimental phenomenon was discussed according to hydrophobic interaction and ion-exchange mechanism in the separation. The optimized chromatographic conditions were selected. The optimized eluent for the separation consisted of 0.2 mmol L⁻¹ tetrabutylammonium hydroxide + 0.10 mmol L⁻¹ citric acid + 9% acetonitrile (pH 5.5). The flow rate was set at 6.0 mL min⁻¹. The column temperature was 25 °C. Under the optimal conditions, the better separation of CF₃SO₃ ⁻ and C₇H₇SO₃ ⁻ was achieved without any interference by other anions (Cl⁻, Br⁻, I⁻, NO₃ ⁻, SO₄ ²⁻, ClO₃ ⁻, BF₄ ⁻ and PF₆ ⁻). The detection limit (S/N = 3) was 0.28 and 0.71 mg L⁻¹ for CF₃SO₃ ⁻ and C₇H₇SO₃ ⁻, respectively. The method has been applied to the determination of CF₃SO₃ ⁻ and C₇H₇SO₃ ⁻ in ionic liquids. The spiked recoveries of CF₃SO₃ ⁻ and C₇H₇SO₃ ⁻ were 101.1 and 100.2%, respectively.

     

A Novel Non-Extractive Sequential Injection Procedure for Determination of Cadmium

This paper presents a novel non-extractive procedure for cadmium determination in a sequential injection (SI) system. The reaction is based on the formation of a complex by Cd(II), iodide ions, and 2-[2-(4-dimethylamino-phenyl)-vinyl]-1-ethyl-quinolinium iodide (R), commonly known as Quinaldine red. Complex-formation results in significant changes in the UV-Vis spectrum of R: the peak is significantly broadened and a shoulder appears near 618 nm. It is important to emphasize that no surfactant addition is needed for solubilization of the system. Under the optimum reaction conditions the calibration plot was linear in the range 1.12–11.24 mg L^?1 Cd and the detection limit was 0.24 mg L^?1 Cd. The method was tested for the analysis of mineral water and pharmaceutical samples spiked with cadmium.     

Nonderivatized Sarcosine Analysis by Gas Chromatography after Solid-Phase Microextraction by Newly Synthesized Monolithic Molecularly Imprinted Polymer

In this study, a simple method for analysis of nonderivatized sarcosine was developed by gas chromatography. It is based on solid-phase microextraction of sarcosine on a novel synthesized solid-phase microextraction (SPME) fiber. A monolithic SPME fiber was fabricated based on a molecularly imprinted polymer that could be coupled with gas chromatography for extraction and determination of sarcosine. Extraction time, pH, and ionic strength were investigated as important factors in the extraction procedure. The fabricated fiber was firm, inexpensive, stable, and selective, which are vital characteristics for SPME. The selectivity of the fabricated fiber in relation to analog compounds was also investigated. Under optimum conditions, the calibration curve was linear in the range of 1–100 mg L⁻¹ (R ² = 0.987). High extraction efficiency for sarcosine was obtained with a detection limit of 0.37 mg L⁻¹. The fabricated fiber was successfully applied for SPME of sarcosine from urine after its extraction, followed by gas chromatography flame ionization detector analysis.

     

Determination of Titanium in Nano-Titanium(IV) Oxide Composite Food Packaging by Microwave Digestion and Inductively Coupled Plasma Atomic Emission Spectrometry and Inductively Coupled Plasma Mass Spectrometry

Titanium was determined in nano-titanium(IV) oxide food packaging by microwave digestion with inductively coupled plasma atomic emission spectrometry (ICP-AES) and inductively coupled plasma mass spectrometry (ICP-MS). Microwave digestion was optimized using different acid combinations. Both spectrometry techniques showed good reproducibility, repeatability, and recovery. For ICP-AES, the limit of detection was 5.0 mg kg^?1, the linear dynamic range was 100–5000 µ g L^?1, the average recoveries for blank samples spiked with titanium were between 94.7% and 100.1%, and the relative standard deviations were from 2.1% to 7.1%. By ICP-MS, the limit of detection was 0.3 mg kg^?1, the linear dynamic range was 0.5–200 µ g L^?1, the recoveries were 88.4%–96.3%, and the relative standard deviations were 6.3%–7.4%. These results indicated that methods were effective for the determination of titanium in food packaging.