The retention of organic cations including homologues of n-alkylamines, phenylalkylamines, and ethanolamines was investigated for 20 commercially produced cation-exchange columns with varying matrix, bonding chemistry, functional groups, and ion-exchange capacity. All data was obtained using 13 mM nitric acid as eluent, under constant column temperature of 25 degrees C and employing a combination of a UV-detector followed by a nonsuppressed conductivity detector. Collected data was used to calculate methylene selectivity alpha(CH2) values from dependences logk - nCH2 with an outlook to evaluate and characterise hydrophobicity of various cation-exchange columns used in ion chromatography. According to the determined alpha(CH2) values the studied cation-exchangers were divided into groups of low (0.195 - 0.286), moderate (0.316 - 0.525) and high (0.502 - 1.078) hydrophobicity. New parameters illustrating contribution of aromatic ring and hydroxy- groups to the retention of model compounds were explored. The effect of aromatic group can be evaluated by a comparison of separation selectivity log(kpea/kea) of phenylethylamine and ethylamine; and this parameter was observed to vary from 0.480 obtained for silica coated with poly(butadiene-maleic acid) to 1.644 for carboxylic cation-exchanger IonPac CG12. A contribution of hydroxyl- group in the retention was less profound with separation selectivity between monoethanolamine and ethanolamine varied from -0.55 to 0.320. A possibility of multipoint interactions of organic cations with cation-exchangers was discussed. The evidence of a mixed-mode behaviour of cation-exchangers was presented.

The retention regularities on a column packed with microspherical zeolite 13X particles were studied for different classes of compounds (alkanes, aromatic substances, oxygen-, nitrogen-, chlorine-, and sulfur- containing compounds) under conditions of hydrophilic interaction liquid chromatography (HILIC) using methanol and acetonitrile as mobile phases. In general, the retention (logk') of studied substances having kinetic diameter less than zeolite pore size is proportional to their polarity. The retention of organic substances was compared for 13X and mesoporous silica columns. A special attention was paid to the retention of n- and iso-alcohols homologues, for which a electrostatically induced sieving effect was observed. It was found that retention factors (k') of solutes on 13X depend strongly on flow rate of the mobile phases indicating the presence of kinetic selectivity effect for the micrporous adsorbent. For the first time the baseline separation was obtained for the low homologues of n-alkanols. Also, selective separation of methanol and methanol-d4 (selectivity alpha = 1.274; resolution of peaks RS = 1.32) is achieved on 50 x 4.6 mm I.D. column with acetonitrile as the eluent.

This chapter describes multiple ways for using complexation in ion-exchange chromatography of metal ions. The main role of complexation is to improve separation selectivity and optimize the total time of complete separation. Complexation can be exploited either in the mobile phase with standard ion-exchange and reverse-phase adsorbents or in a specially designed stationary phase with immobilized chelating ligands. Chelation ion chromatography (CIC) is a high-performance liquid chromatography (HPLC) mode, in which metal ions are retained and separated according to the stability of their complexes with functional groups immobilized on the surface of the chelating or complexing adsorbent. The retention of metals is proportional to the stability constants of surface complexes. As a rule, separation selectivity for CIC and classic ion-exchange chromatography is orthogonal. Unlike ion chromatography, CIC is significantly less sensitive to the ionic strength of analyzed solutions, which makes it useful for the analysis of very complex samples. The theory, methodology, and some practical applications of complexation in ion-exchange chromatography are considered in this chapter.

The most significant element of any chromatographic system is chromatographic column, which is responsible for the provision of desired selectivity and separation efficiency. Ion-exchange chromatography is used for the separation of various inorganic and organic ions as well as ionic and polar compounds. There is a large number of ion-exchange columns designed for separation of specific groups of analytes. This chapter considers basic characteristics of ion-exchangers affecting separation selectivity of simple inorganic and organic ions. Classification of ion-exchangers based on charge and type of functional groups, matrix properties, localization of charged groups, and bonding chemistry is presented. The role of secondary interactions in ion-exchangers is briefly discussed with a focus on their contribution in mixed-mode retention mechanism. Ion-exchange selectivity is considered for the separation of small inorganic and organic ions, where electrostatic interactions compose the dominant contribution into retention mechanism.

A new derivatization reagent, phthalylglycyl chloride (PG-Cl), for the analysis of urinary amino acids was demonstrated using reversed-phase ultra-high performance liquid chromatography coupled to electrospray ionization-quadrupole-time-of-flight mass spectrometer. The study compares the limits of detection and quantification for different sample preparation techniques with the commonly used and effective method of derivatization using dansyl chloride. The stability of the derivatives was investigated, and the study includes an example of urinary amino acid analysis using PG-Cl derivatization. The optimal values for pH, temperature, and concentration of the derivatization reagent were established. Limits of quantification in the range of 0.5–500 µg/mL were obtained for different amino acids. The possibility of phthalylglycyl chloride usage for non-target screening applications and targeted analysis of amino acids in urine was discussed. An advantages and issues of PG-Cl in comparison with commonly used acyl-chlorides (FMOC-Cl and DNS-Cl) provided and discussed.

Inorganic zeolites or microporous crystalline aluminosilicates have high porosity, developed specific surface area, uniform pore size and ion exchange properties, which determines their molecular sieve and adsorption properties. The use of zeolites as catalysts, dryers of solvents and gases, and selective sorbents for the separation of low molecular weight compounds is widely known. Zeolites are widely used as fillers for chromatographic columns in gas adsorption chromatography. Little is known about the use of zeolites in high-performance liquid chromatography (HPLC) and the mechanism of sorbate retention on these sorbents. Depending on the properties of sorbates, retention is determined by a combination of ion exchange, adsorption, molecular sieve effect, as well as kinetic selectivity. Due to solvation of the sorbent surface in HPLC, the thermodynamic parameters of the interaction of sorbates with zeolite change, the effective pore size decreases, and the diffusion of separated compounds into the pores of the sorbent becomes more difficult. Nevertheless, zeolites are promising adsorbents, since specific size (dpore) and the pore geometry of zeolites, as well as the possibility of selecting zeolites with a certain polarity, determines the high selectivity of the separation of low molecular weight compounds. Wide-pore zeolites with dpore (0.6-0.8 nm) with 8, 10, 12, and 14-membered ring channels are of greatest interest for HPLC. This review provides brief information about the classification, composition, structure of zeolites and their effect on their adsorption properties, as well as systematizes data on the use of zeolites in HPLC.

The chromatographic retention of carbohydrates on chelating stationary phase loaded with different metal ions was studied under conditions of hydrophilic interaction chromatography (HILIC). The chelating stationary phases represented silica microparticles with immobilized 2-hydroxyethyliminodiacetic acid (HEIDA) groups in loose form and saturated with Ca2+, Pb2+, and La3+form. The role of loaded metal ion, the acetonitrile and methanol content in the mobile phase, buffer pH and column temperature on the retention of l-(+)-arabinose, d-(+)-maltose, l-(+)-rhamnose, d-(+)-lactose, d-(+)-xylose, glucose, fructose, sucrose, mannose, maltotriose and d-(+) raffinose was studied. The investigation was mainly focused on possible contribution of the complexation in the stationary phase on retention of carbohydrates as well as on effect of the presence metal ion in HEIDA-silica on resulting HILIC behavior of. It is shown that adsorbents with immobilized metal complexes have a good potential for the separation of organic ligands under HILIC mode.

The new scheme of the rapid preconcentration of volatile organic substances followed by the thermodesorption and gas chromatographic determination by using a flame ionization detector is proposed for the analysis of air. The scheme implies a change in the geometry of the adsorbent layer in a column during the transition from adsorption to thermal desorption steps. The extraction of analytes is carried out in a wide tube, allowing quantitative adsorption at higher flow rates of the analyzed air passed through the magnetic sorbent held in a thin layer retained by a permanent magnet without any supporting frits. Novel magnetic adsorbents composed of magnetite or a zirconia/magnetite core and pyrocarbon shell are developed for this application. At the end of the adsorption step, the magnet moved out of the system, and the adsorbent transferred under the gravity force into a narrow tube, which provides the more efficient heating of the adsorbent and minimal blurring of the analyte zones during the subsequent thermal desorption. The proposed scheme allows a significant reduction (approximately 10 times) of the time required for the preconcentration of analytes, which is illustrated by the GC determination of alcohols (butanol-1, pentanol-1), phenol, and o-cresol in the air.

High-performance liquid chromatography (HPLC) method for direct determination of water impurities in various organic solvents using a column (50 × 4.6 mm, ID) packed with 5 μm faujasite and methanol as an eluent was developed. Detection of the water peaks was performed by using either refractometric or indirect spectrophotometric method at 204 nm. In the first case the limit of detection (LOD) and limit of quantitation (LOQ) were 0.001 wt% and 0.0033 wt%, respectively for a sample volume of 20 μL. A linear calibration plot (R2 = 0.9998) for the water content between 0.01 and 9.55 wt% was obtained. The developed method was applied for the direct analysis of various polar organic solvents including acetonitrile, nitromethane, 1,4-dioxane, 2-ethoxyethanol, methanol, dimethyl sulfoxide (DMSO), ethanol and 2-propanol.

Dopamine, adrenaline and octopamine are small polar molecules that play a vital role in regulatory systems. In this paper, phthalylglycyl chloride was proposed as a derivatization agent for octopamine, adrenaline and dopamine determination in urine for the first time. The derivatization procedure facilitated the use of reversed-phase liquid chromatography with positive electrospray ionization–high-resolution mass spectrometry. An LC-HRMS method was developed that provided quantification limits of 5 ng/mL and detection limits of 1.5 ng/mL for all analytes. The 95–97% yield of derivates was observed after a 10 min derivatization with phthalylglycyl chloride at pH 6.5 and 30 °C. The proposed method was successfully applied to the analysis of human urine samples. The obtained results were compared with those of conventional derivatization procedures with 9-fluorenyl-methoxycarbonyl chloride and dansyl chloride.

A novel enantioselective adsorbent was obtained by hybridization of microspherical polystyrene-divinylbenzene (PS-DVB) macroporous particles with eremomycin-stabilized gold nanoparticles (GNPs). Macrocyclic antibiotic eremomycin was used as a stabilization agent to obtain GNPs which were then characterized by transmission electron microscope. The average diameter of obtained nanoparticles is about 16.6 nm. Eremomycin-stabilized nanoparticles were successfully embedded into the porous polymer structure with a resulting chiral selector content of 37.5 pmol/g. The obtained PS-DVB composite containing GNPs with immobilized eremomycin was studied by scanning electron microscopy and diffuse reflectance spectroscopy. The values of the specific surface area (500 m2/g) and porosity of the adsorbent (0.39 cm3/g) are measured using nitrogen adsorption at low temperatures. The obtained composite material was used as a chiral stationary phase of liquid chromatography. A good separation enantio-selectivity to amino acids, their derivatives and beta-blockers under RPC (reversed-phase) and HILIC (Hidrophilic Interaction Liquid Chromatography) mode is demonstrated. The results obtained revealed that the prepared Eremo@GNP@PS-DVB composite is promising for use as a stationary phase in HPLC.

Adsorption and chromatographic properties of oxidized and hydrogenated diamond synthesized at high pressure and high temperature (HPHT) are studied using highperformance liquid chromatography. The retention factors of organic cation (benzyltributylammonium chloride), weak base (aniline), weak acid (benzoic acid), strong acid (benzenesulfonic acid), hydrophobic toluene, and hydrophilic uracil are obtained at different pH, organic solvent content, and ionic strength of mobile phase. Both adsorbents exhibited moderate polarity with a mixed-mode retention mechanism with a combination of ion-exchange, hydrophobic and hydrophilic interactions. Unexpectedly, hydrogenated HPHT revealed significant anion-exchange properties under acidic conditions and cation-exchange properties under alkaline conditions, while only cation-exchange ability was found for oxidized HPHT in a whole pH range. The retention factors obtained for a set of 21 model compounds including n-alkyl-, polymethyl-, nitro- and halogenated benzenes are well correlated with their hydrophobicity (log P ) values. The thermal stability of the adsorbent and immutability of retention mechanisms involved was confirmed by linear Van’t Hoff plots for the investigated compounds.

Adsorption and chromatographic properties of oxidized and hydrogenated 'high pressure and high temperature' synthesised diamond (HPHT) are studied using high-performance liquid chromatography. The retention factors of organic cation (benzyltributylammonium chloride), weak base (aniline), weak acid (benzoic acid), strong acid (benzenesulfonic acid), hydrophobic toluene, and hydrophilic uracil are obtained at varied pH, organic solvent content, and ionic strength of mobile phase. Both adsorbents exhibited moderate polarity with a mixed-mode retention mechanism with a combination of electrostatic, hydrophobic and hydrophilic interactions. Unexpectedly, hydrogenated HPHT revealed significant anion-exchange properties under acidic conditions and cation-exchange properties under alkaline conditions, while only cation-exchange selectivity was noted for oxidized HPHT across the enntire pH range. The retention factors obtained for a set of model compounds including n-alkyl-, polymethyl-, nitro- and halogenated benzenes correlated well with their hydrophobicity (logP) values. The thermal stability of the adsorbent and immutability of retention mechanisms involved was confirmed by linear van't Hoff plots for the investigated compounds.

Solid-phase analytical derivatization (SPAD) is a promising hybrid sample preparation technique combining the clean-up and preconcentration of the sample in a single step. In this work, a novel SPAD method based on the preparation of trimethylsilyl (TMS) derivatives of steroid hormones (testosterone, estrone, DHT, estriol, estradiol, and progesterone) in Phenomenex Strata C18-E (100 mg, 1 mL) cartridges has been developed and applied for their GC-MS/MS determination in human urine samples. The proposed procedure allows the detection and quantification of steroids with limits of 1.0–2.5 and 2.5–5 ng/mL, respectively. These characteristics are comparable with those obtained with a conventional liquid–liquid extraction, while the recovery of analytes in the proposed SPAD procedure is higher. The major advantages of SPAD are a short derivatization time, high efficiency, and the possibility to automatize the procedure. However, its cost-effectiveness in routine practice is still questionable.

In this study, a novel approach in headspace gas chromatographic analysis using the selective absorption of the gas extractant during concentration of the analytes was developed. The carbon dioxide used as the gas extractant was removed from the sample flow by passing it through a column packed with microdispersed sodium hydroxide granules. The analytical capabilities of the suggested method were illustrated by the determination of aliphatic and aromatic hydrocarbons in water. We established that this method allows the preconcentration of analytes in the gas phase to be increased proportionally to the volume ratios of the gas extractant before and after absorption, while the analyte limits of detection decrease 30-fold. For example, benzene can be detected in water at a concentration of 0.5 μg/L.

The silicon carbide and poly(butadiene-acrylonitrile) rubber (NBR) composite material was used for the first time as adsorbent for gas-phase preconcentration of volatile hydrocarbons. The possibility of the preconcentration of n -alkanes and polyaromatic hydrocarbons from the air by using passive sampling on cartridges packed with this sorbent following by thermal desorption - gas chromatographic determination was demonstrated. The sorption rate of model substances from the air at room temperature and atmospheric pressure was studied. The optimum material for the storage and transportation of the collected samples was selected. The desorption efficiency of model compounds from the adsorbent was investigated. The result of thermo gravimetric analysis of the composite to provide the choice of temperature for the regeneration was given. Soil air at the oil field was analyzed using the developed method. The possibility of multiple use of the composite sorbent for analysis was demonstrated.

Macrocyclic glycopeptide antibiotics immobilized on silica are one of the effective classes of stationary phases for chiral recognition and HPLC separation of a wide range of optically active compounds. Enantioselectivity primarily depends on the chemical structure of the chiral ligand, immobilization chemistry, and separation conditions. In the present work, three new chiral stationary phases (CSPs) based on macrocyclic antibiotic eremomycin were prepared and investigated for enantioseparation of amino acids. Two eremomycin derivatives, including simple non-substituted amide and bulky adamantyl amide, provided important information on the role of the carboxylic group in the eremomycin structure in the chiral recognition mechanism concerning amino acid optical isomers. One more CSP having a chlorine atom in the same position elucidates the role of the first aromatic ring in the eremomycin structure as a crucial point for chiral recognition. CSP with immobilized chloreremomycin was the most successful among the phases prepared in this work. It was additionally investigated under various separation conditions, including the type and content of the organic solvent in the eluent, the effects of different additives, and the concentration and pH of the buffer. Importantly, an efficient enantioselective separation of amino acids was achieved with pure water as the eluent.

The results of studying the complexation of a number of metal ions on the surface of silica chemically modified by various functional analytical groups are systematized in the review. Examples of the influence of the matrix of sorbents (silica) on the thermodynamic and kinetic parameters of surface complexation reactions with metals are presented. Specific features of using finely dispersed silicas with complexing functional groups in high performance complexation metal ion chromatography are considered.