Ion-pair Extraction Research Articles

Spectrophotometric Estimation of Losartan Potassium with Methylene Blue by Ion-Pair Extraction Method

A selective and sensitive spectrophotometric extraction method was established and used to estimate antihypertensive drug, losartan potassium. The method is based on the formation of blue ion pair of the anionic drug, losartan, and the cationic dye, methylene blue, at adjusted pH 6.5 in aqueous solutions, followed by quantitative extraction to dichloromethane;.The observed maximum absorbance was at π 654.9 nm. With 4.53321 x 105 M-1 cm-1 molar absorptivity, Beer's law was obeyed within a concentration range of 0.03-1.5 μg / ml. The limit of detection and the limit of quantification were 0.01μg / ml and 0.03μg / ml, respectively. The method's precision was estimated by a relative standard deviation (0.725%-1.64%), and the accuracy was validated at a recovery range (98.48-100.3%). The proposed method was successfully used for estimating losartan in the pharmaceutical formulation and in the urine sample.

Cover Feature: Selective Phase Transfer Reagents (OxP‐crowns) for Chromogenic Detection of Nitrates Especially Ammonium Nitrate (Chem. Eur. J. 58/2020)

A color-based detector for ammonium nitrate consists of crown ether-appended oxoporphyrinogens, the OxP-Crowns, which extract ion pairs into an organic phase based on cation binding at crown ether and anion complexation. Selective mauve chromogenic response is observed when ammonium nitrate, commonly used in improvised explosive devices, is extracted from water to chloroform providing a simple test. As illustrated, a network of responses is found when considering other anions and aqueous phase pH. More information can be found in the Full Paper by J. P. Hill et al. on page 13177.

Development and application of analytical procedures for the GC–MS/MS analysis of the sulfates metabolites of anabolic androgenic steroids: The pivotal role of chemical hydrolysis

In this work, we present a gas-chromatography tandem mass spectrometry (GC–MS/MS) method for the identification of the sulfo-conjugate metabolites of pseudo-endogenous steroids (endogenous steroids when administered exogenously). We have preliminarily evaluated the performances of different preparations of sulfatases from Pseudomonas aeruginosa and Helix pomatia, characterized by various origins and catalytic activities, and compared the efficacy of the enzymatic hydrolysis with chemical hydrolysis, performed with a mixture of ethyl acetate, methanol, and sulphuric acid. A procedure for the selective isolation of steroid conjugates from the urine matrix has been designed and optimized, based on the “sequential” extraction of the glucuro-conjugated and of the sulfo-conjugated fractions, performed by two different direct methods, i.e. by ion paired extraction or solid-phase extraction. More specifically, the former method is based on the use of N,N-dimethylephedrinium bromide as the ion paired extraction reagent, while the latter on the use of WAX® (weak anion exchange) cartridges. The performance of the newly developed procedure has been assessed by the analysis of real urine excretion samples collected after the oral intake of a single dose of dehydroepiandrosterone (DHEA) or androstenedione (AED), measuring the concentration of epiandrosterone (EpiA) sulfate.Our results have shown the following: (i) although the yields of chemical hydrolysis and enzymatic hydrolysis are in some cases quite similar, the former is generally preferable since it results in the quantitative cleavage of sulfate moiety; (ii) ion paired extraction has been selected as the most reliable method for direct isolation of sulfate steroids from urine matrices; (iii) EpiA sulfate allows to prolong the detectability of DHEA and AED when compared to routinely used steroidal target compounds.

Spectrophotometric determination of chloroquine, pyrimethamine and trimethoprim by ion pair extraction in pharmaceutical formulation and urine

A simple and accurate method for the determination of chloroquine diphosphate (CQ), pyrimethamine (PYM) and trimethoprim (TMP) in pure, pharmaceutical and urine samples is described. The method involved an ion pair extraction procedure with chloroform using an acid base indicator, bromocresol purple (BCP), as a counter ion. The ion pair extracted in organic phase was yellow, and the absorbance was measured at λmax = 420 nm. Beer's law was obeyed over the concentration range of 1.25-8.75, 0.62-7.5, and 1.25-10.71 μg/mL, respectively. The Sandell's sensitivity was 0.01258, 0.01102 and 0.01464 μg/cm2. The Ringbom optimum concentration range, which was 2.5-7.5, 1.25-7.5 and 2.5-10.7 μg/mL for CQ, PYM, and TMP, respectively, exhibited reliability of the method. Stoichiometry and thermodynamic of the complexes were evaluated by Job's method and Benesi-Hildebrand plot. The statistical results of intra- and inter-day estimation of drugs and comparison with the reported methods demonstrated high precision and accuracy of the method. The procedure was rapid, simple and suitable for quality control purpose.

Ion pair extraction coupled with digital image colorimetry as a rapid and green platform for pharmaceutical analysis: An example of chlorpromazine hydrochloride tablet assay

Ion pair extraction coupled with digital image colorimetry has been developed as a promising platform for pharmaceutical analysis. The applicability of the approach was demonstrated through the assay of chlorpromazine hydrochloride tablets. In this method, the colorless, positively charged drug reacted with an anionic methyl orange dye in 1.5 mL microcentrifuge tubes, forming a yellow ion pair complex, which was extracted one time using a green solvent, i.e., ethyl acetate. Without the isolation or transfer of the liquid phase for dilution or measurement in a cuvette, a set of multiple tubes consisting of standards and samples were placed in a radial alignment above the white-light-illuminating screen of an iPad in a closed dark box and an image was taken in a single shot from the top of the box using an iPhone camera. The intensities of the yellow color of the extracts were transformed into red–green–blue (RGB) pixels using a mobile application, and the B values divided by the total of R + B + G were used as the analytical signals, which were plotted against the drug concentration to construct a standard curve. The proposed method showed good linearity (R2 = 0.9998) over the concentration range of 2.5–50 μg mL−1 with a limit of quantitation of 2.30 μg mL−1. The proposed method was accurate, precise, and free from interferences by excipients used in tablets, thus yielding assay results with no significant difference from those analyzed using the United States Pharmacopeia 42 reference method. Moreover, the proposed method is exceptional because it can be rapidly and easily used, requires relatively inexpensive instrumentation, can be safely utilized by analysts, and is environmentally friendly. Therefore, the proposed assay platform has considerable potential for application to routine quality control and analysis of drug formulations in the pharmaceutical industry.

Synergistic Ion-pair Extraction and Separation of Trivalent Lanthanoid Ions with 4-Isopropyltropolone and 1,10-Phenanthroline into o-Dichlorobenzene.

The synergistic extraction of trivalent lanthanoid (Ln(III)) ions with 4-isopropyltropolone (Hipt) and 1,10-phenanthroline (phen) in o-dichrolobenzene (DCB) was investigated. The synergistic effect in DCB is more significant than that in toluene, and the polynuclear complexes found in toluene are not formed in DCB. Based on the 3-dimensional equilibrium analysis, the extracted species for La(III), Eu(III), and Lu(III) are found to be ion-pairs, such as Ln(ipt)2phen·ClO4 and Ln(ipt)2(phen)·ClO4 in the presence of NaClO4 as a salt, and the extraction constants of the respective species were determined. The simultaneous extraction of different lanthanoids in the present extraction system was demonstrated. The separation factors between lighter lanthanoids were larger than those with 2-ethylhexyl phosphonic acid mono-2-ethylhexyl ester, an excellent extractant for the separation of lanthanoid ions, in decane.

Monofunctionalized Bambus[6]urils and Their Conjugates with Crown Ethers for Liquid-Liquid Extraction of Inorganic Salts.

Bambusurils are a growing family of macrocyclic anion receptors. In this Letter, we present the first syntheses of monofunctionalized bambusurils and their use for the preparation of heteroditopic bambusuril-crown ether conjugates suitable for the extraction of ion pairs from water to chloroform.

Quantification of 4-Methylimidazol in NMRI Mice Plasma and Cerebrospinal Fluid (CSF) by Using Liquid Chromatography Tandem Mass Spectrometry.

A sensitive method using ion-pair extraction was developed by liquid chromatography tandem mass spectrometry (LC–MS/MS) for measurement of 4-methylimidazole (4-MI) in NMRI mice plasma and cerebrospinal fluid (CSF). Detection was done by electrospray positive ionization mass spectrometry in the multiple-reaction monitoring (MRM) mode. The validation method was applied to quantification of 4-MI in plasma and CSF samples using oral doses of 100, 200, and 300 mg/kg in NMRI mice. The efficiency of the method was evaluated in terms of linearity (R 2> 0.99), recovery (98–107%, 3 levels) and precision (8–10%, 3 levels, n = 6). Limit of detection (LOD) and limit of quantification (LOQ) were 25 ng/mL and 50 ng/mL, respectively. The results obtained showed that the exposure to oral doses of 4-MI in mice makes different concentrations in plasma and CSF and causes significant changes in mice. This study was the first report for determination of 4-MI in plasma and CSF samples in mice. Our results suggest that LC-MS/MS-based on ion-pair extraction is a robust method with high detection ability for measurement of 4-MI in plasma and CSF samples. Therefore, the developed method can be useful for evaluation and monitoring of imidazole derivatives in biological samples.

A Rapid and Sensitive Method for the Pharmacokinetic Study of Janumet (Sitagliptin and Metformin) Tablets by LC-MS/MS Coupled with Ion-Pair Solid Phase Extraction

Background: As first-line treatments for diabetes, sitagliptin and metformin have been widely prescribed as a combination to enhance the therapeutic effect. Objective: To establish a methodology to simultaneously monitor the two drugs in vivo by a reversedphase Liquid Chromatography-Tandem Mass Spectrometric (LC-MS/MS) method. Methods: The two drugs were extracted from 50 μl human plasma by ion-pair solid phase extraction. The separation of the plasma samples was implemented on an Agilent Zorbax SB-CN column (150×4.6 mm, 5.0 µm). The mobile phase was the mixture (80:20, v/v) of methanol and 5.0 mM ammonium formate in water (pH 4.5). An ion trap spectrometer equipped with an electrospray ionization source was utilized to detect the elution in positive mode. Quantification of the analytes was achieved by Multiple Reaction Monitoring (MRM) using the transitions of m/z 408.3→235.1 for sitagliptin and m/z 130.1→ 60.2 for metformin. Results: Sitagliptin and metformin demonstrated good linearity among the range of 1.00-1000 ng/mL and 5.00-4000 ng/mL. The intra-day and inter-day investigations displayed precisions of ≤ 3.6% and an accuracy range of -7.5% to 6.0% for the two drugs. The mean recovery of the two drugs was 96.0% and 98.5%. Under mandatory storage conditions, both the drugs gave an acceptable stability. The throughput of the assay was found to be more than 100 plasma samples per day ascribed to the run time of 3.0 min for each sample. Conclusion: The developed method was successfully applied to a pharmacokinetic study for a fixeddose tablet formulation containing 50 mg sitagliptin and 500 mg metformin in 12 healthy volunteers.

Manganese sensitised-indirect determination of melamine in milk-based samples by flame atomic absorption spectrometry coupled with ultrasound assisted-cloud point extraction

ABSTRACTIn the current study, a simple and low- cost method of UA-CPE in combination with flame atomic absorption spectrometry (FAAS) was developed for pre-concentration and indirect determination of melamine in milk-based samples. The method is based on the formation of charge transfer sensitive ternary complex among melamine, Mn(II) and Eosin Yin presence of sensitivity enhancer, ionic surfactant cetyltrimethylammonium bromide at pH 4.5, and then extraction of the formed complex into the micellar phase of nonionic surfactant, Triton X-114. After extraction, the surfactant-rich phase was diluted with 1.0 mol L−1 HNO3 in methanol and aspirated into the nebuliser of FAAS for indirect analysis. For optimisation of the variables affecting the ion-pair formation and extraction efficiency, the univariate method was adopted due to its simplicity and ease of use. Under optimal conditions, a good linear relationship was observed from 0.8 to 130 µg L−1 with a detection limit of 0.23 µg L−1. From pre-concentration of 35-mL sample, a pre-concentration factor of 70-fold was obtained with a good sensitivity enhancement (88.5). The accuracy and precision were evaluated as repeatability and intermediate precision with RSD of less than 6.5% with a recovery varied from 92.5% to 98.6%. (n: 5, 5, 25 and 100 µg L−1). The performance of the method from the accuracy and precision studies of two quality control samples was highly good with the precision (4.2–6.0%) and relative recoveries (91.4–96.0%) obtained for spiking levels, 5 and 10 µg L−1. The accuracy, according to two-way ANOVA analysis, was also controlled by two calibrations approaches without any matrix effect in analysis step of samples.

Development of a new analytical method for Pb preconcentration and its further determination in water and foodstuffs using relatively low-sensitivity flame atomic absorption spectrometry

ABSTRACTThe present study describes chelation of Pb(II) with ascorbic acid and formation of a charge-transfer sensitive ion-pair in the presence of Rhodamine 6G at pH 5.5, and then its extraction to the micellar phase of non-ionic surfactant, PONPE 7.5 by an ultrasound-assisted cloud point extraction method before analysis by FAAS. The various variables affecting ion-pair formation and extraction efficiency were studied and optimised. Under the optimised conditions, the good linear relationships in the ranges of 0.4–150 μg L−1 and 0.8–120 μg L−1 for solvent-based calibration and matrix-matched calibration curves, respectively, were achieved with a pre-concentration factor of 71.4 from pre-concentration of 50-mL sample. Moreover, the limits of detection with good sensitivity enhancements of 124 and 114.5 were 0.13 and 0.24 μg L−1, respectively, while the intra-day and inter-day precision (as RSD%, for five replicate measurements of 5 and 100 μg L−1 in the same day and three succeed days) were in range of 2.8–5.4% and 3.7–6.3%, respectively. The matrix effect on triplicate determination of 50 µg L−1 Pb(II) was also investigated. The accuracy of the method was statistically verified by the analysis of two certified reference materials (CRMs) after digestion with acid mixtures (HNO3-H2O2-HF and HNO3-H2O2) and dilution at suitable ratios. It has been observed that there is statistically not a significant difference between the certified- and found-values. The accuracy was also controlled using the pre-treated sample solutions spiked at different concentration levels, and the good spiked recoveries were obtained in range of 90–102.8%. The method was successfully applied to the determination of trace amounts of lead in water and food matrices with satisfactory results.

Ion-Pair Extraction of Quaternary Ammoniums Using Tetracyanocyclopentadienides and Synthetic Application for Complex Ammoniums.

A simple isolation method for quaternary ammonium cations via ion-pair extraction using tetracyanocyclopentadienide (TCCP) was established. Separation of tetraethylammonium and carbachol cations was achieved by the selective extraction of tetraethylammonium with ethoxycarbonyl TCCP, which was moderately lipophilic. The ion-pair extraction with TCCPs was applied to the synthesis of complex quaternary ammonium salts, including a spiro vinylammonium that is a precursor of the novel 3-aza-Cope-Mannich cascade.

Ion pair vortex assisted-ionic liquid based dispersive liquid-liquid microextraction for selective separation and preconcentration of 4-methylimidazole from caramel colour drinks and foodstuffs prior to its spectrophotometric determination

In the study, a simple, fast, easy to use, cost-effective and green analytical method was developed for the selective extraction and determination of 4-methylimidazole (4-MeI) from caramel colored drinks and foods by using vortex assisted-ionic liquid-based dispersive liquid liquid microextraction (VA-IL-DLLM) followed by spectrophotometry. The method is based on ion-pairing of the formed anionic chelate complex, AgIm(ImH)(H2N-C(CH2OH)2(CH2O)− (in fact, where the charged chelate formation and concentration dependent charge transfer proceeds together in aqueous IL medium), between soft Ag+ ions and 4-MeI with cationic soft IL, trihexyl(tetradecyl)phosphonium chloride, Cyphos IL 101 in presence of chelating and redox sensitive biological tris buffer at pH 7.0, and then extraction of the formed ion-pair into the micro-droplets of the IL by help of vortex. Greener IL, Cyphos IL 101 as both extractant and ion-pairing was effectively used together with the dispersive solvent (ethanol) for separation of analyte from sample matrix in extraction process. The important factors influencing extractable ion-pair formation and extraction efficiency were evaluated and optimized in detail. The method has shown a low limit of detection and quantification, LOD and LOQ (1.15 and 3.82 μg L−1) and excellent linearity (4–500 μg L−1) with a regression coefficient (r2 = 0.9917) via calibration based on aqueous standard solutions of 4-MeI in solvent. Also, a validation study was performed on the spiked two quality control samples (honey and tea) at levels of 25, 100 and 300 μg L−1 by means of matrix-matched calibration curves. The method showed good analytical features such as LODs (1.27, 1.42 μg L−1), LOQs (4.24, 4.73 μg L−1), recovery% (91.5–96.3%), repeatability (3.5–6.2%) and reproducibility (4.1–7.6%) without a significant matrix effect in linear working ranges of 5–350 and 4–400 μg L−1 respectively as a measure of accuracy and precision with a sensitivity enhancement factor of 115-fold. After the validation, the method was successfully applied to the determination of low levels of 4-MeI in caramel colour drinks and foodstuffs. The findings have shown that the method is promising for accurate and reproducible detection of 4-MeI in the selected samples with acceptable analytical results.

Ionic Liquid-Based Process Development for Cobalt Recovery from Aqueous Streams

Using the ionic liquid [P8888 +][Oleate-], liquid-liquid extraction has been studied to recover Co2+ from water. Extractionregeneration experiments were followed during five consecutive cycles with Na2CO3(aq) as regeneration solution. Over 99% of Co2+ was extracted and using 0.7-1 M Na2CO3(aq) the extracted Co2+ was recovered for 99% in the form of CoCO3(s). Co2+ transfer shifted from ion-pair extraction in the first cycle to ion-exchange in the successive cycles. Thus, the measurement of a single extraction–regeneration cycle is not sufficient to perceive conclusive information about the steady-state conditions of the process. In the context of the feasibility of the technology, four key aspects are addressed: extraction efficiency, recovery of the IL, loss of the IL, and the end product. Synopsis Cobalt extraction from aqueous using ionic liquid [P8888 +][oleate-] and cobalt recovery applying Na2CO3 solution as an efficient and sustainable regeneration strategy since it provides interesting end product for market with high regeneration efficiency.

Perfluoroalkyl Substances (PFASs) in Ten Edible Freshwater Fish Species from Major Rivers and Lakes in Korea: Distribution and Human Exposure by Consumption

In this study, we determined 13 perfluoroalkyl substances (PFASs) concentrations in 514 samples of blood, liver, muscle and egg tissues of ten edible freshwater fish species from major rivers and lakes in Korea. The sample was extracted by ion-pair extraction (IPE) method and analyzed by Shimadzu HPLCMSMS 8040. Besides, the Total Daily Intake (TDI) of PFASs and potential risk of human exposure by freshwater fish consumption in several scenarios were investigated. The greatest total PFASs concentration in each fish tissue was found as 925 ng/mL in a crucian carp (Carassius auratus) for blood, 598 ng/g ww in a Korea piscivorous chub (Opsariichthys uncirostris) for liver, 283 ng/g ww in a crucian carp (Carassius auratus) for egg, and 129 ng/g ww in a skygager (Erythroculter erythropterus) for muscle. The greatest mean concentration of PFOS was determined in blood (38.8 ng/mL), followed by egg (22.0 ng/ww), liver (21.1 ng/g ww) and muscle tissues (1.14 ng/g ww). Addition to fish species and tissues, several other factors such as sex, habitat and fish traits, may affect the bioaccumulation of PFASs in fish. The consumption guideline of one meal per week for skygager is strongly applied for skygager caught from a middle stream of Nakdong River watershed. The total daily intake of PFASs by freshwater fish muscle tissues consumption were ranged from 0 to 12.4 ng/kg b.w./day for PFOS and from 0 to 0.05 ng/kg b.w./ day for PFOA. This study firstly reports the tissues distribution and human consumption exposure of PFASs in various edible freshwater fish from major rivers and lakes in Korea. The contamination levels of PFOS and PFOA in the fish muscles in this study were unlikely to pose an immediate risk to the Korean general population or Korean freshwater fish consumer population.

Determination of Perfluorinated Compounds Level of Domestic and Imported Crabs in South Korea

Perfluorinated compounds(PFCs) are an organic fluorine compound that hydrogens of all of carbons compound were replaced by fluorine. PFCs were demonstrated for toxic effects by various studies. PFCs tend to accumulate because of the long half-life in vivo. Research on PFCs level of food material in South Korea is still in insufficient. In this study, we analyzed 19 PFCs in crab meat with LC-MSMS.A total of 151 crabs were collected from fish market of South Korea. The samples taken included countries of origin information; South Korea (n=104), China (n=37) and India (n=10). Crab samples were homogenized with water. Each sample was weighed (1g) and spiked 20 µl internal standard. PFCs were extracted from samples using ion-pairing extraction after enzyme hydrolysis. Quantitative analysis was performed with liquid chromatography–tandem mass spectrometry(LC-MS/MS).As result, PFOA was detected in South Korean and Chinese crab samples. PFTrDA and PFDS levels were higher in Chinese crab than South Korean Crabs.Although the legal criteria of PFCs in food is not yet defined, the levels of PFCs in South Korean crabs were similar to or less than other studies performed in aboard; Belgium (PFOS ranged from 93 to 292 ppb), China (PFOS up to 82.2 ppb) and Japan (PFOA ranged from 5.6 to 14 ppb).

A green and cost-effective procedure for determination of anionic surfactants in milk with liquid-liquid microextraction and smartphone-based photometric detection

Aiming at determination of anionic surfactants as milk adulterants, a novel procedure based on simultaneous protein precipitation and liquid-liquid microextraction (LLME) of the ion-pair formed between the analytes and methylene blue is described. Sample treatment, ion-pair extraction, and photometric detection with a smartphone camera were carried out in a single vessel, thus significantly simplifying the procedure and minimizing risks of contamination and analyte loss. The chloroform volume for both sample treatment and extraction of the ion-pair was only 150 μL and usual drawbacks of LLME, such as the need for phase isolation and dilution of the extract before spectrophotometric measurements were avoided. By using sodium dodecylsulfate as a model surfactant, and only 100 μL of sample, 25 μg of methylene blue, and 2.9 mg of EDTA, a linear response was achieved from 10 to 50 mg L−1, r = 0.999 (n = 5), with detection limit (99.7% confidence level) and coefficient of variation of 2.2 mg L−1 and 1.9% (n = 10), respectively. The proposed procedure is a simple, fast, cost-effective, and environmentally friendly approach for detection of milk adulterations by surfactants.

Insights in uranium extraction from spent nuclear fuels using dicyclohexano-18-crown-6 – Fate of rhenium as technetium homolog

The single extraction of rhenium(VII) and uranium(VI) from nitric acid solution by dicyclohexano-18-crown-6 (DCH) solutions was investigated. The extraction of Re(VII), in the form of perrhenate (ReO4−) anion, was optimum for a nitric acid concentration of 3 M and was explained by the ion-pair extraction of perrhenate anions by the hydroxonium DCH complex. The stoichiometry of the Re(VII) complex was obtained from the distribution data by slope analysis and the extracted specie was identified as {ReO4−(DCH-H3O)+}. The uranyl extraction by DCH solutions was evaluated under the same conditions and the extracted specie was identified as {(NO3−)2(DCH-UO22+)} for a nitric acid concentration above 5 M. The extraction of rhenium(VII) from nitric acid solution by DCH solutions in the presence of large excess of uranium(VI) was then investigated. For a nitric acid concentration of 3 mol/L, the extraction efficiency of perrhenate was found to be almost independent of uranium concentration. Based on the chemical similarities between Re(VII) and Tc(VII), this suggests that DCH could be considered for the separation of technetium (VII)/uranium(VI) from nitric acid solution.

Highly Efficient Trivalent Americium/Europium Separation by Phenanthroline-Derived Bis(pyrazole) Ligands.

The synthesis, Eu3+ complexation, and solvent extraction of Am3+ and Eu3+ from nitric acid solutions by tetradentate phenanthroline-derived bis(pyrazole) (BPPhen) ligands were described. By using meta-nitrobenzotrifluoride as diluent, BPPhen ligands in combination with 2-bromohexanoic acid extracted Am3+ and Eu3+ with remarkably high efficiency, excellent selectivity, and fast extraction kinetics. Stripping posed no issues. The ligands also showed excellent hydrolytic stability and acid tolerance. 2-Bromohexanoic anion neutralized the charge and increased the lipophilicity of the extracted ion pair. The extraction conformed to a cation exchange model. Slope analysis demonstrated the extraction of 1:2 metal/ligand complexes. Analyses by electrospray ionization mass spectrometry, time-resolved laser-induced fluorescence spectroscopy, Raman, and Fourier transform infrared techniques indicated that the composition of the extracted species is [Eu(nOct-BPPhen)2(H2O)]3+. The formation of 1:2 complexes was also confirmed by UV-vis spectroscopic titration and microcalorimetric titration methods. Meanwhile, the stability constants ( K) and the thermodynamic parameters (Δ H, Δ S, Δ G) for the complexation of Eu3+ with nOct-BPPhen were presented too.

Determination of 4-Methylimidazole in Ammonia Caramel Using Gas Chromatography–Tandem Mass Spectrometry (GC-MS/MS)

One of Maillard reaction products formed in the production of ammonia caramel is 4(5)-methylimidazole (4-MeI) classified as carcinogen. A method of 4-MeI determination based on ion-pair extraction and derivatisation with isobutyl chloroformate with subsequent gas chromatography-tandem mass spectrometry analysis was proposed. Tandem mass spectrometry was applied to reduce the influence of matrix and increase the selectivity and sensitivity of the method. Triple quadrupole GC-MS system was used for this study. The collision energies were optimized for MRM mode. The detection (LOD) and quantification limits (LOQ) of the elaborated method were 17 and 37.8 μg kg−1, respectively, repeatability was <15% RSD for analyzed caramel samples, and the recovery for 4-MeI was 101%. Comparison of MS/MS with SIM detection on the same instrument proved almost 30 times lower LODs achieved by tandem mass spectrometry compared to SIM. Described method can be routinely used for monitoring 4-MeI as a quality and safety marker in the production of ammonia caramel.