[Thrombolysis with Tenecteplase in a stroke with a long time window after onset of symptoms. Report of one case]. / Trombolisis endovenosa con tenecteplase en ventana extendida tras selección por CT y AngioCT: Caso clínico.

We report a 78-year-old man with a basal Rankin score of 2 points, last seen 10 hours before in good conditions, who arrived at the emergency department with left hemiparesis, hypoesthesia, and spacial neglect. Neuroimaging was compatible with stroke in the territory of the right middle cerebral artery. Due to the evolution time of the stroke, usual thrombolysis was contraindicated. Therefore, a thrombolysis with Tenecteplase was used with reversal of symptoms without symptomatic bleeding and with recovery of baseline functionality.

Trombolisis endovenosa con tenecteplase en ventana extendida tras selección por CT y AngioCT: Caso clínico / Thrombolysis with Tenecteplase in a stroke with a long time window after onset of symptoms. Report of one case

We report a 78-year-old man with a basal Rankin score of 2 points, last seen 10 hours before in good conditions, who arrived at the emergency department with left hemiparesis, hypoesthesia, and spacial neglect. Neuroimaging was compatible with stroke in the territory of the right middle cerebral artery. Due to the evolution time of the stroke, usual thrombolysis was contraindicated. Therefore, a thrombolysis with Tenecteplase was used with reversal of symptoms without symptomatic bleeding and with recovery of baseline functionality.

Extraction of ß-blockers from urine with a polymeric monolith modified with 1-allyl-3-methylimidazolium chloride in spin column format.

A glycidyl methacrylate-based monolith was modified with imidazolium-based ionic liquid (IL) to be used as stationary phase for solid-phase extraction (SPE). The host monolithic support was prepared by in-situ UV polymerization in spin column format. Two approaches were developed to incorporate the IL into the polymeric monolithic matrix: generation of IL onto the surface monolith, and copolymerization by addition of the IL to the polymerization mixture, which gave the best results. The resulting sorbent materials were morphologically characterized and used for the isolation of five ß-blockers from human urine samples. All SPE steps were accomplished by centrifugation, which reduces significantly costs and time in sample treatment. Under optimal conditions, ß-blockers were quantitatively retained in the modified monolith at pH 12, and desorbed with a water-methanol mixture, to be subsequently determined via HPLC with UV detection. The limits of detection ranged between 1.4 and 40 µg L-1, and the reproducibility among extraction units (expressed as relative standard deviation) was below 8.2%. The novel phase was successfully applied to the extraction of propranolol in urine samples with recoveries above 90%.

Search of non-ionic surfactants suitable for micellar liquid chromatography.

Most reports in reversed-phase liquid chromatography (RPLC) with micellar mobile phases make use of the anionic sodium dodecyl sulfate. This surfactant masks efficiently the silanol groups that are the origin of the poor efficiencies and tailing peaks observed for basic compounds in conventional RPLC. However, it has the handicap of yielding excessive retention, which forces the addition of an organic solvent to reduce the retention times to practical values. Other surfactants, such as the non-ionic polyoxyethylene(23)lauryl ether (Brij-35), are rarely used. Brij-35 allows the separation of a large range of analytes in adequate retention times, without the need of adding an organic solvent to the mobile phase. However, this non-ionic surfactant shows irreversible adsorption on chromatographic columns and peak shape is poorer. Therefore, the search of non-ionic surfactants with similar properties to Brij-35, but showing reversible adsorption and better peak shape, can be of great interest. In this work, the adequacy of several non-ionic surfactants as modifiers in RPLC has been explored, being polyoxyethylene(10)tridecyl ether particularly attractive. The separation of different types of compounds was checked: sulfonamides (acidic), ß-adrenoceptor antagonists and tricyclic antidepressants (basic with diverse polarity), and flavonoids (with and without hydroxyl groups on the aromatic rings). The chromatographic behaviors were examined in terms of retention and peak shape. The results were compared with those obtained with Brij-35.

LC of high to moderately polar basic drugs in urine with water and detergent, and direct injection.

BACKGROUND: Micellar LC was first proposed as a 'green' mode using mobile phases of water and surfactant. However, in most procedures a small amount of organic solvent is required to decrease the retention to convenient values. Results & methodology: Mixed micellar mobile phases prepared with both cationic (sodium dodecyl sulphate) and nonionic surfactant (Brij-35) modulate the retention of high to moderately polar basic drugs to practical times, eliminating the need of organic solvent. While the mobile phase is continuously recycled through the system, the stationary phase performance is maintained after repetitive injection of the samples. DISCUSSION & CONCLUSION: Through an extensive validation, the approach is shown to be appropriate to determine these drugs in urine samples without previous pretreatment.

Reversed-phase liquid chromatography without organic solvent for determination of tricyclic antidepressants.

The chromatographic behavior of seven tricyclic antidepressants (amitryptiline, clomipramine, doxepin, imipramine, maprotiline, nortryptiline, and trimipramine) was examined with micellar mobile phases containing the nonionic surfactant Brij-35. Acetonitrile-water mixtures were also used for comparison purposes. Tricyclic antidepressants are moderately polar basic drugs, which are positively charged in the usual working pH. This gives rise to a strong association with the alkyl chains and residual ionized silanols in silica-based stationary phases, which is translated in a high consumption of organic solvent to get appropriate retention times. Brij-35 modifies the surface of the stationary phases creating a neutral bilayer that masks silanols and reduces the polarity. Consequently, the retention times are decreased. A simple chromatographic procedure for the control of tricyclic antidepressants in pharmaceutical formulations was developed, using 0.02 M Brij-35 at pH 3 and UV detection. Satisfactory recoveries were achieved, with intra- and inter-day relative standard deviations usually below 1 and 2%, respectively. The preparation of the samples was simple and only required solubilization and filtration steps previous to injection. The proposed procedure has the advantage of not using an organic solvent in the mobile phase, and the biodegradable character of Brij-35. This makes an example of "green" liquid chromatographic analysis.

Correction of the deviations in the retention times with Chromolith columns associated to the flow rate: implications in the modelling of the retention behaviour.

In a previous work (J. Sep. Sci. 2009, 32, 2793-2803), we reported an interpretive optimisation approach to achieve maximal resolution in minimal analysis time, based on models describing the retention and peak shape as a function of mobile phase composition and flow rate. The method was applied to the separation of a group of basic drugs in a Chromolith column. In that work, we found that the retention factors were sensitive to the flow rate. The reason of the observed deviations in retention times is the increase in the column volume at the applied pressure, which decreases the linear velocity inside the column. This behaviour forced to include a correction term in the model that described the retention. We show here how the deviations in retention times can be evaluated, allowing retention models that do not include the flow rate as a variable, similar to isocratic chromatography at fixed flow rate. The logarithm of the deviations in the retention times with flow rate is shown to correlate with the solute polarity. This correlation is compared with similar correlations for the retention factor at fixed mobile phase composition and the extrapolated retention factor in water at fixed flow rate.

Performance of a Chromolith RP-18e column for the screening of beta-blockers.

The chromatographic performance of a monolithic column (Chromolith RP-18e) was comprehensively examined in the isocratic separation of ten beta-blockers, using ACN-water mobile phases, and compared with the performance of three microparticulate RP columns manufactured with different types of silica: Spherisorb ODS-2, Kromasil C18 and XTerra MS C18. The comparison considered the analysis time, selectivity, peak shape (column efficiency and asymmetry) and resolution, and was extended to a wide range of mobile phase compositions. The Chromolith column showed good performance for the analysis of beta-blockers with regard to the packed columns. In terms of selectivity and analysis time, the greatest similarity was found between the Chromolith and XTerra columns. The addition of a silanol blocking agent (0.1% triethylamine) to both Chromolith and Spherisorb columns yielded, apparently, a similar blocking degree of the silanol groups (based on the similar peak shapes), and gave rise to similar selectivity.

Micellar liquid chromatography in doping control.

The issue of doping control in sport involves the development of reliable analytical procedures and efficient strategies to process a large number of samples in a short period of time. Reversed-phase LC techniques with aqueous-organic mobile phases and MS or diode-array detection yield satisfactory results for the identification of prohibited substances in sport. However, time-consuming sample pretreatment steps are required, which reduces sample throughput. Micellar LC (MLC) that uses hybrid mobile phases of surfactant above its critical micellar concentration and organic solvent has been revealed as an interesting alternative. The surfactant sodium dodecyl sulfate solubilizes the protein components of urine, serum and plasma, which permits their direct injection into the chromatographic system. Only dilution and filtering of the samples may be required. Most MLC analyses are performed in isocratic mode, with short retention times and good selectivity. The sensitivity of MLC allows the detection of a variety of doping substances at least 24-48 h after being administered.

Reversed-phase liquid chromatography analysis of alkyl-imidazolium ionic liquids II. Effects of different added salts and stationary phase influence.

Two mixtures of four 1-alkyl-3-methylimidazolium ionic liquids (ILs) salts associated to the anions tetrafluoroborate or hexafluorophosphate were analyzed by reversed-phase liquid chromatography with three different stationary phases: Kromasil C(8), Zorbax Extend C(18) and Zorbax Sb-Aq. The effect on retention of various inorganic salts (NaCl, NaH(2)PO(4,) NaBF(4), NaClO(4) and NaPF(6)) added to acetonitrile/water mobile phases was studied. The three columns gave similar separation profiles. In all cases, the retention of ILs increased with the increasing affinity of the inorganic anions for the apolar stationary phases; a phenomenon called chaotropicity. The chaotropic anion order is Cl(-) approximately H(2)PO(4)(-) < BF(4)(-) approximately ClO(4)(-) < PF(6)(-). It is established that the presence of chaotropic anions in the mobile phase do not permit to differentiate between ILs associated to different anions. However, chloride or dihydrogenphosphate added salts do not fully screen the retention differences between ILs associated with different anions. Distorted and even split peaks may appear in the chromatogram depending on the nature and concentration of the injected ILs. In the RPLC analysis of imidazolium-based IL, it is recommended to add to the mobile phase significant amounts of a salt containing a chaotropic anion. This salt addition will improve the IL peak shapes and give reproducible retention factors. LODs in the low microgram range ( approximately 5 nmol) were obtained with the Kromasil C(8) column with a 50/50 acetonitrile-water mobile phase containing 0.01 M NaPF(6) added salt and 230 nm UV detection.

Solvent systems for countercurrent chromatography: an aqueous two phase liquid system based on a room temperature ionic liquid.

A new aqueous two phase liquid system (ATPS) based on the ionic liquid 1-butyl-3-methyl imidazolium chloride (BMIM Cl), potassium dibasic phosphate (K(2)HPO(4)) and water was recently proposed in the literature. The full phase diagram of this ATPS was prepared and some tie lines were fully determined. It was compared to classical ATPSs based on polyethylene glycol with an average molecular mass of 1000 (PEG 1000) and 10,000 (PEG 10000) and K(2)HPO(4). Two countercurrent chromatography (CCC) columns, a hydrostatic Sanki and a J type hydrodynamic CCC columns were used to test the liquid phase retention of these ATPSs in all possible configurations. It was found that the BMIM Cl ATPS liquid phases were much easier to retain in the two CCC columns than the PEG 1000 ATPS phases. Using protein and alcohol solutes, it was established that the BMIM Cl ATPS has a polarity completely different from that of the PEG 1000 ATPS. For example, ovalbumin partitions equally between the two phases of the PEG 1000 ATPS (K(D)=1.4) when it is completely located in the BMIM Cl upper phase of the ionic liquid ATPS (K(D)=180). The discrimination factor of the ionic liquid system and its intrinsic hydrophobicity were respectively found three times higher and ten times lower than the respective values of the PEG 1000 ATPS.

Reversed phase liquid chromatography of alkyl-imidazolium ionic liquids.

Eleven 1-alkyl-3-methyl imidazolium ionic liquid (IL) salts were analyzed in reversed phase mode with a Kromasil C18 column. The mobile phases were water-rich acetonitrile solutions (water content > or =70%, v/v) without any added salts. It is shown that it is possible to separate different ILs sharing the same cation and differing by the anion when salt-free mobile phases are used. When a buffer, acetate or phosphate salt, or any salt, such as sodium chloride or sodium tetrafluorobarate, is added to the mobile phase, the ILs differing only by their anions cannot be separated. ILs with different alkyl chains in the imidazolium cation are separated by mobile phases with or without added salts following a hydrophobic interaction behavior: log k is proportional to nC, the carbon number of the alkyl chain. Important differences in ion/stationary phase interactions are observed depending on the ionic content of the mobile phase. With salt-free mobile phases, the IL/C18 stationary phase interactions correspond to concave isotherms associated with fronting peaks for all ILs. With mobile phase containing 0.01 M of salt, tailing IL peaks correspond to convex adsorption isotherms. Also, the IL retention factor depends on the concentration and nature of the added salt. Hexafluorophosphate chaotropic anions can adsorb on the Kromasil C18 surface dramatically increasing the imidazolium cation retention factors.

Nonmolecular solvents in separation methods: dual nature of room temperature ionic liquids.

Room temperature ionic liquids (RTIL) are molten salts starting to be used as nonmolecular solvents in separation methods mainly for their extremely low vapor pressure and thermal stability. RTILs are formed by an anion associated to a cation. This intrinsic structure gives them a dual nature. When used as additives in RPLC mobile phases to enhance basic compound separation, RTILs lose their particular physicochemical properties to become just salts. However, a given RTIL is not equivalent to another one made with the same cation. It is shown that both the anion and the cation contribute to solute retention and peak efficiency extending beyond simple "salting-out" or ion-pairing effects. Nine different alkyl-methyl-imidazolium ionic liquids with different alkyl chain length and chloride or BF(4-) or PF(6-) anions were used as additives (50 mM max. conc.) in the liquid chromatography separation of some cationic basic solutes on a Kromasil C18 column. It is shown with sodium salts and an acetonitrile-water 30/70 v/v mobile phase that anions can adsorb on the stationary phase surface according to their lyotropic character. They can also form ion pairs with the cationic basic solutes. Alkyl-imidazolium cations also adsorb on the C18 bonded stationary phase due to hydrophobic character depending on their alkyl chain length. Anion adsorption dramatically increases the cationic solute retention factors when cation adsorption decreases them. The cation adsorption is mainly responsible for peak shape and efficiency enhancements. RTILs are additives that enhance the basic cationic solute peak shape changing peak position. A wise choice of the appropriate combination of anion lyotropy with imidazolium cation hydrophobicity allows playing with solute selectivity and analysis duration.

Elution-extrusion countercurrent chromatography. Use of the liquid nature of the stationary phase to extend the hydrophobicity window.

Countercurrent chromatography (CCC) is a liquid chromatography technique with a liquid stationary phase. Taking advantage of the liquid nature of the stationary phase, it is possible to perform unique operations not possible in classical liquid chromatography with a solid stationary phase. It is easy to avoid any solute-irreversible absorption in the CCC column. If the retention volumes of solutes become too high, the dual mode will be used. The roles of the phases are reversed. The stationary phase becomes the mobile phase, and the CCC column is started again. The solutes elute rapidly in what was previously the stationary phase. The theoretical basis of the dual-mode method is recalled. The dual-mode method is a discontinuous method. The separation should be stopped when the phase switch is performed. The elution-extrusion procedure is another way to avoid any irreversible adsorption of solutes in the column. The method uses the fact that the liquid volumes occupied by the solutes highly retained inside the column can be orders of magnitude lower than the mobile-phase volume that would be needed to elute them. The elution-extrusion method also has two steps: the first step is a regular CCC chromatogram. Next, the stationary phase containing the partially separated hydrophobic solutes is extruded out of the column in a continuous way using the liquid stationary phase. The theory of the process is developed and compared to the dual-mode theory. Alkylbenzene homologues are experimentally used as model compounds with the heptane/methanol/water biphasic liquid system to establish the theoretical treatment and compare the performance of two types, hydrodynamic and hydrostatic, of CCC columns. It is shown that the method can dramatically boost the separation power of the CCC technique. An apparent efficiency higher than 20 000 plates was obtained for extruded octylbenzene and a 160-mL hydrodynamic CCC column with less than 500 plates when conventionally used.