The use of glyoxal and glyoxylic acid to determine N- and N,N-alkyl-substituted hydrazines by liquid chromatography

Using chromatography and spectrophotometry, it has been shown that the reaction of 1,1-dimethylhydrazine (UDMH), methylhydrazine (MH), and 2-hydroxyethylhydrazine (HEH) with excess of glyoxal (Gl) and glyoxylic acid (GlA) in aqueous solutions yields corresponding monohydrazones as single derivatization products. The derivatization reaction occurs in a quantitative yield for 20 min at 25 or 40°C for Gl and GlA, respectively (pH 3.5). The electronic absorption spectra of the derivatives have maxima in the range of 275–305 nm. The conditions for the simultaneous determination of hydrazines in waters by reversed-phase HPLC coupled with UV detection in aqueous solutions with preliminary derivatization are proposed. The derivatives are separated on a Zorbax SB-C18 (150 × 4.6 mm) column with a mobile phase of 20 mM phosphate buffer solution (pH 3.5) and 2–5% acetonitrile. The detection limits are 0.25–0.5 or 0.4–0.7 μg/L for the derivative of Gl and GlA, respectively.     

A sensitive chromatographic determination of hydrazines by naphthalene-2,3-dialdehyde derivatization

A new high-performance liquid chromatography (HPLC) method for the sensitive simultaneous determination of hydrazine (Hy), monomethylhydrazine (MMH) and 1,1-dimethylhydrazine (UDMH) based upon the derivatization of hydrazines with naphthalene-2,3-dialdehyde and the separation of the derivatives on Zorbax Eclipse AAA column in a single chromatographic run under acidic conditions (pH 2.4) was developed. Hydrazine and monomethylhydrazine derivatives were found to be strongly fluorescent at λ_ex?=?273?nm, λ_em?=?500?nm. It was shown that UDMH derivative can be detected as non-fluorescent hydrazone at 290?nm by UV-detection. Limits of detection were 0.05?µg?·?L^?1 for Hy and MMH, and 1?µg?·?L^?1 for UDMH for the injection volume of 100?µL. The method was validated for water sample analysis. It proved to be selective, accurate and precise with the supplementary advantage of the simple and rapid sample preparation.     

Optimization of cloud point extraction of copper with neocuproine from aqueous solutions using Taguchi fractional factorial design

Taguchi method was applied to optimize cloud point extraction (CPE) conditions for preconcentration and determination of trace amounts of copper by UV-Vis spectrophotometry. Briefly, the copper ions formed complexes with neocuproine in aqueous solution; then, Triton X-114 (0.15%, w/v) was added and phase separation occurred upon heating to 60°C. The copper complexes were preconcentrated into the small volume of the surfactant-rich phase; after centrifugation, the surfactant-rich phase was diluted with methanol and absorbance was measured at 455 nm. The main factors affecting the CPE were evaluated and optimized with Taguchi orthogonal array design (OA ₂₅). Under the optimum conditions, the calibration curve was linear in the range 2–500 μg/L (r ² > 0.997). The limit of detection and preconcentration factor were 1.8 μg/L and 37.2, respectively. The applicability of the proposed method was successfully confirmed by preconcentration and determination of trace amounts of copper in water samples and satisfactory results were obtained.     

Sorption preconcentration and separation of Palladium(II) and Platinum(IV) for visual test and densitometric determination

We have demonstrated the advantages of the dynamic preconcentration and separation of Pd(II) and Pt(IV) on paper carriers modified with 3-methyl-2,6-dimercapto-1,4-thiopyrone. The optimal conditions of the solid-phase reaction have been determined in Pd(II) sorption; after its separation Pt(IV), has been preconcentrated by sorption as its dimercaptides. Test scales have been produced for the visual determination of 0.5–40 μg Pd(II) and 1–195 μg Pt(IV) in 10- and 100 mL-samples, respectively. In addition, a procedure of their sorption-chromaticity densitometry determination from a single aliquot portion has been developed with detection limits of 5 and 1 ng/mL, respectively, and a procedure of Pd(II) determination using a test strip (c _min = 0.40 mg/L) has been proposed. The procedures have been applied to the determination of palladium and platinum in electrolytes, sludges, and alloys.     

Determination of herbicides in environmental water samples by simultaneous in‐syringe magnetic stirring‐assisted dispersive liquid–liquid microextraction and silylation followed by GC–MS

An on‐line, fast, simple, selective, and sensitive method has been developed for the determination of three herbicides belonging to the following families: triazines (atrazine), chloroacetamide (alachlor), and phenoxy (2,4‐dichlorophenoxyacetic acid) in water samples. The method involves an in‐syringe magnetic stirring‐assisted dispersive liquid–liquid microextraction along with simultaneous silylation prior to their determination by gas chromatography with mass spectrometry. Extraction, derivatization, and preconcentration have been simultaneously performed using acetone as dispersive solvent, N‐methyl‐N‐tert‐butyldimethylsilyltrifluoroacetamide as derivatization agent and trichloroethylene as extraction solvent. After stirring for 180 s, the sedimented phase was transferred to a rotary micro‐volume injection valve (3 μL) and introduced by an air stream into gas chromatograph with mass spectrometry detector. Recovery and enrichment factors were 87.2–111.2% and 7.4–10.4, respectively. Relative standard deviations were in the ranges of 6.6–7.4 for intraday and 9.2–9.6 for interday precision. The detection limits were in the range of 0.045–0.03 μg/L, and good linearity was observed up to 200 μg/L, with R² ranging between 0.9905 and 0.9964. The developed method was satisfactorily applied to assess the occurrence of the studied herbicides in groundwater samples. The recovery test was also performed with values between 77 and 117%.     

Dispersive liquid-liquid microextraction and solid-phase extraction of polar pesticides from natural water and their determination by micellar electrokinetic chromatography

Procedures for the determination of polar pesticides in surface and ground water after their preconcentration by dispersive liquid-liquid microextraction and solid-phase extraction on Oasis® HLB (3 cc/60 mg) extraction cartridges are proposed. Conditions for the separation and determination of pesticides from the following classes by micellar electrokinetic chromatography were chosen: arylhydroxycarboxylic acids, sym-triazines, triazinones, urea derivatives, neonicotinoids, carbamates, triazoles, imidazoles, benzimidazoles, and organophosphorus compounds. The determination limits of pesticides in water were 0.5–20 μg/L with consideration for preconcentration. The relative standard deviation of the results of analysis was no higher than 10%.     

The trace determination of some heavy metals in waters by flow-injection spectrophotometry and potentiometry

Three automated flow-injection systems are proposed for the determination of traces of manganese(II), lead and copper(II) in waters. The first system utilizes the catalytic effect of manganese(II) on the oxidation of N,N-diethylaniline by potassium periodate at pH 6.86–7.10 (30°C) and is used for spectrophotometric determination at 475 nm in the range 0.02–1.00 μg1^?1; the system involves reagent injection and stopped flow. The determination of lead in the range 0.7–100 μg1^?1 is based on spectrophotometric detection of the lead 4/(2-pyridylazo)resorcinol complex at 525 nm after on-line preconcentration of the sample (5–50 ml) on a minicolumn filled with Chelex-100 or Dowex 1-X8 resin. A potentiometric flow-injection system with a copper ion-selective electrode is applied for the determination of 0.5–1000 μg 1^?1 copper(II) after on-line preconcentration of 50–500 ml of sample on Chelex-100 resin. The procedures are tested on synthetic and real water samples, including sea water and waste-waters.     

Highly sensitive determination of 1,1-dimethylhydrazine by high-performance liquid chromatography–tandem mass spectrometry with precolumn derivatization by phenylglyoxal

A new highly sensitive and rapid approach to the determination of 1,1-dimethylhydrazine in natural water is developed (determination range is 0.03–1 μg/L). It is based on the use of high-performance liquid chromatography–tandem mass spectrometry with precolumn derivatization by phenylglyoxal and does not require any preconcentration. Derivatization, chromatographic separation conditions, and tandem mass spectrometry detection parameters are chosen. Intra-day precision of the results of measurements of 1,1- dimethylhydrazine in natural water is 12–16%, and inter-day precision is 16–22%. The lowest limit of detection and the lowest limit of quantification are 0.010 μg/L and 0.030 μg/L, respectively.     

Speciation analysis of vanadium in natural water samples by electrothermal vaporization inductively coupled plasma optical emission spectrometry after separation/preconcentration with thenoyltrifluoroacetone immobilized on microcrystalline naphthalene

A sensitive and simple method for low temperature electrothermal vaporization inductively coupled plasma optical emission spectrometry (ETV-ICP-OES) determination of V(IV) and V(V) after separation/preconcentration by a micro-column packed with immobilized thenoyltrifluoroacetone (TTA) on microcrystalline naphthalene has been developed. Thenoyltrifluoroacetone was used as both a chelating agent for micro-column separation/preconcentration and a chemical modifier for ETV-ICP-OES determination of vanadium. Both vanadium species could be trapped by micro-column at pH 4.0, and the vanadate (VO₂⁺) ion could be collected selectively at pH 2.4. Solid material loaded with analyte in the micro-column was dissolved with 100 μL of acetone containing 2.0 mmol L⁻¹ TTA and the vanadium was determined subsequently by ETV-ICP-OES. The concentration of vanadyl (VO²⁺) ion was calculated by subtracting the vanadate concentration from the total concentration of vanadium. Under the optimized experimental conditions, the detection limit (3σ) for the preconcentration of 5 mL of aqueous solution is 0.068 μg L⁻¹ for both species and the relative standard deviations were 4.3% for vanadium(V) and 4.8% for vanadium(IV) (c=10 μg L⁻¹, n=7), respectively. The method was applied successfully to the determination of vanadium(IV) and vanadium(V) in natural water samples.     

Ultrasonic‐assisted derivatization of estrogenic compounds in a cup horn booster and determination by GC‐MS

Cup horn boosters are miniaturized ultrasound baths that maximize efficiency and precision. The optimization of an ultrasonic‐assisted derivatization step by means of a cup horn booster and the determination of estrone, 17β‐estradiol, estriol, 17α‐ethynyl estradiol and mestranol was developed by GC‐MS. Different derivatization reagents and solvents were studied for maximizing the di‐derivatization of 17α‐ethynyl estradiol under ultrasound energy. Only N,O‐bis(trimethylsilyl)trifluoroacetamide with 1% of trimethylchlorosilane in pyridine gave satisfactory results and this mixture was further used in the optimization of the ultrasound assisted derivatization. The experiment designs included sonication time (1–10 min), sonication power (20–80%), sonication cycles (1–9), derivatization reagent volume (25–125 μL) and solvent volume (25–125 μL). Once the optimum conditions were fixed, the effect of organic matter and the frequency of the water bath change were studied. Finally, the validation of the analytical method was carried out using spiked natural and synthetic waters. Recoveries (natural (138–70%) and synthetic (112–89%)), the LODs (0.35–1.66 ng/L), and LOQs (1.16–5.52 ng/L) and the precision (0.2–5.3%) of the method were studied. This is the first work in the literature where a cup horn booster is used with the aim of minimizing derivatization time during the determination of estrogenic compounds.     

Preconcentration and determination of trace amounts of lead (II) as thenoyltrifluoroacetone complex with dibenzo-18-crown-6 by synergistic extraction and atomic absorption spectrometry

A new method for the preconcentration and determination of trace amounts of lead at the μg/L level in natural waters has been established based on the formation of the thenoyltrifluoroacetone (TTA) complex with dibenzo-18-crown-6 (DB18C6) by means of synergistic extraction and back-extraction combined with atomic absorption spectrometry (AAS). The effect of various factors (synergism with TTA and DB18C6, shaking time, preconcentration factor, composition of the extracted species, and foreign ions etc.) on the extraction and back-extraction of lead has been investigated in detail. The lead-TTA chelate in o-dichlorobenzene forms a stable adduct with DB18C6 as Pb(TTA)₂ DB18C6. The stability constant (β) of the adduct determined by curve fitting method was log β = 4.2. The amount of lead in natural waters such as tap water (Kanazawa University) and Kakehashi river (Komatsu City) determined by the present method was found to be 0.64 ± 0.02 μg/L and 5.10 ± 0.03 μg/L, respectively.     

Application of the localized surface plasmon resonance of gold nanoparticles for the determination of 1,1-dimethylhydrazine in water: Toward green analytical chemistry

Localized surface plasmon resonance (LSPR) is an optical phenomena generated by light when it interacts with conductive nanoparticles that are smaller than the incident wavelength. In this work, we proposed a simple, fast, and green method for spectrophotometric determination of unsymmetrical 1,1-dimethylhydrazine (UDMH) based on LSPR property of gold nanoparticles (AuNPs). An LSPR band is produced via reduction of Au³⁺ ions in solution by UDMH as active reducing agent in the presence of cetyltrimethylammonium chloride as a capping agent. Some important parameters in the formation of LSPR including Au(III) concentration, pH, concentration of stabilizer, and reaction time were studied and optimized. Under optimum conditions, the LSPR intensity displays linear response with the increasing UDMH concentration in the range from 0.5–10 μg/mL at 550 nm with a detection limit of 0.2 μg/mL. Also, the relative standard deviation for ten replicate determination of 5.0 μg/mL of UDMH was 3%. Usage of AuNPs as new nontoxic reagent instead of hazardous reagents in the spectrophotometric determination of UDMH is a step toward green analytical chemistry. The proposed method was successfully applied for determination of UDMH in water and wastewater samples.     

Rapid determination of bisphenol A in drinking water using dispersive liquid‐phase microextraction with in situ derivatization prior to GC‐MS

This paper described a novel approach for the determination of bisphenol A by dispersive liquid‐phase microextraction with in situ acetylation prior to GC‐MS. In this derivatization/extraction method, 500 μL acetone (disperser solvent) containing 30.0 μL chlorobenzene (extraction solvent) and 30.0 μL acetic anhydride (derivatization reagent) was rapidly injected into 5.00 mL aqueous sample containing bisphenol A and K₂CO₃ (0.5% w/v). Within a few seconds the analyte was derivatized and extracted at the same time. After centrifugation, 1.0 μL of sedimented phase containing enriched analyte was determined by GC‐MS. Some important parameters, such as type and volume of extraction and disperser solvent, volume of acetic anhydride, derivatization and extraction time, amount of K₂CO₃, and salt addition were studied and optimized. Under the optimum conditions, the LOD and the LOQ were 0.01, 0.1 μg/L, respectively. The experimental results indicated that there was linearity over the range 0.1–50 μg/L with coefficient of correlation 0.9997, and good reproducibility with RSD 3.8% (n = 5). The proposed method has been applied for the analysis of drinking water samples, and satisfactory results were achieved.     

Use of an ionic liquid‐based surfactant as pseudostationary phase in the analysis of carbamates by micellar electrokinetic chromatography

The applicability of an ionic liquid‐based cationic surfactant 1‐dodecyl‐3‐methyl‐imidazolium tetrafluoroborate (C₁₂MImBF₄) as pseudostationary phase in MEKC has been evaluated for the analysis of 11 carbamate pesticides (promecarb, carbofuran, metolcarb, fenobucarb, aldicarb, propoxur, asulam, benomyl, carbendazim, ethiofencarb, isoprocarb) in juice samples. Under optimum conditions (separation buffer, 35 mM NaHCO₃ and 20 mM C₁₂MImBF₄, pH 9.0; capillary temperature 25°C; voltage –22 kV) the analysis was carried out in less than 12 min, using hydrodynamic injection (50 mbar for 7.5 s) and detection at 200 nm. For the extraction of these CRBs from juice samples, a dispersive liquid–liquid microextraction (DLLME) procedure has been proposed, by optimization of variables affecting the efficiency of the extraction. Following this treatment, sample throughput was approximately 12 samples per hour, obtaining a preconcentration factor of 20. Matrix‐matched calibration curves were established using tomato juice as representative matrix (from 5 to 250 μg/L for CBZ, BY, PX, CF, FEN, ETH, ISP, and 25–250 μg/L for ASL, ALD, PRC, MTL), obtaining quantification limits ranging from 1 to 18 μg/L and recoveries from 70 to 96%, with RSDs lower than 9%.     

Enantioselective Analysis of Amphetamine-Related Designer Drugs in Body Fluids Using Liquid Chromatography and Solid-Phase Derivatization

A method for the enantioselective determination of the amphetamine-derived designer drugs 3,4-methylenedioxymethamphetamine (MDMA), 3,4-methylenedioxyamphetamine (MDA) and 3,4-methylenedioxyethylamphetamine (MDE) based on their derivatization with (-)-1-(9-fluorenyl)ethyl chloroformate (FLEC) is described. The proposed procedure entails preconcentration and derivatization of the analytes into C₁₈-packed solid-phase extraction cartridges, chromatographic separation of the diastereomers originated in a C₁₈ column under gradient elution, and UV detection at 265 nm. Compared with the solution derivatization approach the described procedure increased analyte responses by factors of 28–58. The reliability of the method has been tested by analysing plasma and urine samples spiked with the analytes in the 0.015–1.0 μg mL^?1 concentration interval. The proposed conditions provided adequate linearity, and coefficients of variation ranging from 5% to 14% in plasma, and from 3% to 12% in urine. The recoveries of the analytes were of 78%–126% and 78%–128% in plasma and urine, respectively. The limits of detection (LODs) obtained for all the analytes were 5 ng mL^?1 in both biological matrices.     

TXRF determination of mercury(II) in water in combination with liquid–liquid microextraction

A highly selective hybrid way of TXRF determination of mercury(II) in drinking water at the level of n(10^–2–10⁰) μg/L is developed. The technique of preconcentration of mercury(II) ions includes directly suspended droplet microextraction with benzene in the form of an iodide molecular complex. The proposed method of determination is characterized by its high degree of sensitivity and reproducibility (c _min = 8 ng/L, s _r = 0.12 (100 ng/L)). The accuracy of the analysis results is confirmed by the introduced–found method.     

Determinaton of trace amounts of titanium by flame atomic absorption spectrometry after cloud point extraction

In this work a cloud-point extraction has been used for the preconcentration of the trace amounts of titanium after complex formation with morin (2′,3,4′,5,7-pentahydroxyflavone) using Triton X-114 as surfactant. The chemical variables affecting the phase separation and the viscosity affecting the detection by flame atomic absorption spectrometry (FAAS) were optimized. At pH 4.5, preconcentration of 50 mL of sample in the presence of 0.08% Triton X-114 and 1.0 × 10^?4 M morin enabled the detection limit (c _L = 3S _b/m) of 2.9 ng/mL titanium and linear range 0.02–2.0 μg/mL to be achived. The preconcentration factor was 61, and the relative standard deviation was 3.8% for 0.1 μg/mL solution of Ti(IV) by repeated assays (n = 9). The proposed method has been applied to the determination of titanium in well water, spiked water and plant (Haloxylon).     

Development of dry derivatization and headspace solid-phase microextraction technique for the GC-ECD determination of haloacetic acids in tap water

A simple, fast and efficient liquid-liquid extraction (LLE) technique using headspace solid-phase microextraction (HS-SPME), in conjunction with gas chromatography-electron capture detection (GC-ECD) has been developed for the determination of haloacetic acids (HAAs) in tap water. The analytical procedure involves LLE, evaporation of extraction solvent to dryness, derivatization of HAAs into their methyl esters with acidic methanol, HS-SPME using 100-μm polydimethylsiloxane (PDMS) fiber, and GC-ECD determination. The derivatization process was optimized in dry conditions to achieve maximum sensitivity using the following conditions: esterification for 10 min at 55°C in 50 μL methanol, 30 μL sulphuric acid and 0.1 g anhydrous sodium sulphate. The HS-SPME conditions were also optimized and good sensitivity was obtained at a sampling temperature of 25°C, an absorption time of 10 min and a desorption time of 2 min. The linear calibration curves were observed for the concentration ranging from 0.1 to 200 μg/L with the correlation coefficients (R ²) greater than 0.993 and the relative standard deviation (RSD) less than 12%. The method detection limits of all analytes ranging from 0.02 to 0.7 μg/L were obtained. The proposed method is compared directly to standard EPA method 552.2 in drinking water, and significant advantage in terms of selectivity was observed. Finally the optimized procedure was applied to the analysis of HAAs in Bizerte drinking water. The studied HAA were detected in all the water samples and the concentration of total HAA5 ranged from 17.8 to 70.3 μg/L.     

Determination of herbicides and their metabolites in natural waters by capillary zone electrophoresis combined with dispersive liquid-liquid microextraction and on-line preconcentration

A method has been proposed for the determination of 17 herbicides and their metabolites in natural waters by capillary zone electrophoresis with UV detection at 190 nm. Dispersive liquid-liquid microextraction with trichloromethane has been used for pesticide recovery from water. The high sensitivity of determination has been provided by additional intracappilary preconcentration: the limits of pesticide detection in water involving off- and on-line preconcentration are 0.5–3.0 μg/L. The analysis takes 1–1.5 h; the relative standard deviation of the analysis results does not exceed 5%.     

Determination of <Emphasis Type="Italic">o</Emphasis>-phthalic acid esters in water by chromatography–mass spectrometry with emulsion dispersive liquid–liquid microextraction preconcentration

Using emulsion dispersive liquid–liquid microextraction preconcentration and injection of a large volume of an extract (10 μL), the limits of chromatographic–mass spectrometric detection of o-phthalic acid esters in water have been attained at the level 4 × 10^–6–1 × 10^–5 mg/L. The main source of the systemic error of the determination of impurities was found to be the release of o-phthalates from microparticles of chromatographic septum to the carrier gas. The extractant (n-octane) was purified by Rayleigh distillation. The independence of the concentration coefficient of the studied o-phthalates of concentration in the range (0.4–30) × 10^–4 mg/L has been demonstrated. The relative expanded uncertainty of the determination of o-phthalates has been calculated and equals 12–39%.