Analysis of volatiles in water using headspace solid-phase microcolumn extraction

A rapid solvent-free sample preparation method is presented in which volatilized organic substances are extracted via a solid-phase microcolumn mounted on a gas-tight syringe by the aspiration of an appropriate volume of headspace (tens of millilitres) of the sample under investigation. The microcolumn with the analytes concentrated on an adsorbent material is then transferred to the analytical instrument for desorption and analysis. The instrumental set-up consists of a Twister desorption unit (Gerstel) mounted on an Agilent 6890 GC system equipped with a CIS 4 programmed temperature vaporiser injector and coupled with an Agilent 5973 MS system. The instrumentation is slightly modified in comparison with the analysis made with a twister (stir bar coated with a layer of polydimethylsiloxane) after stir bar sorptive extraction and, thus, its utilization has been extended. For volatiles in water, the method is applicable to the qualitative screening at the microg/l to sub-microg/l level and to the quantitative determination at the ng/l level.     

Spectrophotometric determination of some phenothiazine drugs using chloramine-T-iodine-starch

A simple, accurate, and sensitive spectrophotometric method for the determination of promethazine hydrochloride (PMH), prochlorperazine maleate (PCPM), trifluoperazine hydrochloride (TFPH), trimeperazine tartrate (TMT), fluphenazine dihydrochloride (FH), and trifluopromazine hydrochloride (TPH) is described. The method is based on the oxidation of the studied drugs by a known excess of chloramine-T in a hydrochloric acid medium and subsequent determination of the unreacted oxidant by interacting it with iodide in the same acid medium. Liberated iodine subsequently reacts with starch to form a stable starch-iodine complex. The reacted oxidant corresponds to the drug content. The colored complex exhibits a maximum absorption at 590 nm. The apparent molar absorptivity and Sandell sensitivity values are in the range 4.07 × 10⁴ − 1.18 × 10⁵ L/mol cm and 45.00−95.00 ng/cm², respectively. The proposed method has been applied to the assay of phenothiazine drugs in pure and dosage forms. The reliability of the analysis was established using parallel determination by the reference method. The text was submitted by the authors in English.     

Elemental concentrations of some Ayurvedic drugs using energy dispersive XRF

Summary Elemental concentration of nineteen Ayurvedic drugs have been measured using energy dispersive X-ray fluorescence analysis. Concentrations of nineteen elements: Si, P, S, Cl, K, Ca, Ti, Cr, Mn, Fe Ni, Cu, Zn, As, Br, Rb, Sr, Zr and Hg have been determined using emission transmission method with Mo target. K, Ca and Fe were detected in all samples and their concentrations ranged from 0.35-2.88%, 0.346-8.65% and 0.007-36.7%, respectively. Maximum concentration measured in other elements ranged from 0.006% to 40.7%. The multi element and non-destructive nature of the method offers a simple way to establish the quality of the drugs that contain heavy metals in considerable concentration.     

Determination of beer aroma compounds using headspace solid-phase microcolumn extraction

A rapid sampling technique for the analysis of beer aroma compounds is described. The headspace (10 ml) is passed through the microcolumn filled with 5 mg of Tenax TA and thermally desorbed in a modified GC inlet (modification is described). Eight compounds (from acetaldehyde to 2-phenylethanol) in four beer samples were analyzed. The correlation coefficients (r²), repeatability (RSD) and limits of detection (LOD) were 0.9973-0.9994, 2.1-6.9% and 0.00002-0.13 mg/l, respectively. The methodology can be useful for routine beer sample analysis.     

New biochemical separations using precolumn derivatization and microcolumn liquid chromatography

Microcolumn liquid chromatography with slurry-packed capillary columns has been used to resolve mixtures of biologically important steroids and prostaglandins. In order to enhance detection sensitivity, the samples are first derivatized with a suitable chromophore-yielding agent. Hydroxy steroids were derivatized with either benzoyl chloride or 7-(chlorocarbonylmethoxy)-4-methylcoumarin, while Dns hydrazine was employed to react with the ketonic groups of certain steroidal conjugates. Bile acids can also be derivatized with bromomethylcoumarin to yield fluorescent products. The use of microcolumns permits both a high degree of component resolution and enhanced detection sensitivity.     

Sample enrichment by using monolithic precolumns in microcolumn liquid chromatography

An on-line sample enrichment system was designed using monolithic precolumns in microcolumn LC. The monolithic ODS capillary columns were prepared via in situ sol-gel processes. The enrichment efficiency of the monolithic columns was tested by using phthalates as the analytes. The relative standard deviations (n = 6) for the retention time, peak area and peak height were between 0.4 and 1.2%, 0.9 and 5.5% and 0.4 and 3.9%, respectively. The system was linear (R2 > 0.99) within the working sample concentration and sample volume ranges. Comparing to 0.2 microl injection with a typical sample injector, the theoretical plate number of a same separation column was increased by 3-6-fold when the precolumn unit was used for sample injection. The recoveries of the analytes were between 88 and 120%, and the sample volume that could be injected into the system was increased up to 5000-fold. The limits of detection were improved by more than 2000-fold and were between 0.21 and 0.87 ng ml(-1) even with a UV absorbance detector. This system was applied to the determination of phthalates contained in laboratory distilled water and tap water samples.     

Flow gradient liquid chromatography using a coated anion exchange microcolumn

Ion chromatography on a 4.0-mm-long (3.0 mm ID) ion exchange column is presented. Using a 10 mM phosphate buffer (pH 2.22) the separation of up to six UV-absorbing anions was obtained using the microcolumn, containing 5 microm RP support (Phenomenex Gemini) coated with the zwitterionic surfactant, (N-dodecyl-N,N-dimethylammonio) undecanoate. The short analytical column facilitated the application of a flow gradient programme over the flow range 0.3-5 mL/min resulting in optimum resolution of nitrite, nitrate, benzoate, iodide, thiocyanate and trichloroacetate in less than 10 min. The effect of both eluent concentration and pH on the retention of six selected anions was investigated, showing a strong pH capacity dependence. The microcolumn was found to exhibit no selectivity towards chloride and so was well suited to the analysis of saline samples. To illustrate this, the rapid analysis of a concentrated iodized table salt sample (20 g/L) was carried out. Following standard addition, a concentration of 3.55 +/- 0.05 microg iodide/g and 1.05 +/- 0.02 microg iodate/g in the solid salt sample was determined.     

Spectrophotometric determination of some antihistaminic drugs using 7,7,8,8-tetracyanoquinodimethane (TCNQ)

A simple and sensitive spectrophotometric method is suggested for analysis of 3 antihistaminic drugs, acrivastine (I), mequitazine (II), and dimethindene maleate (III). The method is based on reaction of the drugs with 7,7,8,8-tetracyanoquinodimethane (TCNQ) in acetonitrile to form highly stable colored products that are measured at 750, 766, and 844 nm for I and II, and 480 and 618 nm for III. Beer's law is obeyed in the ranges of 5-60 microg/mL for 1, 5-50 microg/mL for II, and 10-70 microg/mL for III. The optimum assay conditions and their applicability to the determination of the cited drugs in pharmaceutical formulations are described. The method is statistically analyzed as compared with the European Pharmacopoeia (2001) method for the analysis of dimethindene maleate and reference methods for acrivastine and mequitazine drugs revealing good accuracy and precision.     

Direct coupling of microcolumn liquid chromatography with in-tube solid-phase microextraction for the analysis of antidepressant drugs

The direct coupling of in-tube solid-phase microextraction (in-tube SPME) with microcolumn liquid chromatography (micro-LC) has been investigated for the analysis of antidepressants in human urine. The use of in-tube SPME has been clearly shown to be advantageous for the on-line coupling of the SPME method, as the sample pretreatment technique, with micro-LC as the separation technique. This is because much smaller amounts of the sample solutions, desorption solvents and the mobile phase are required compared with conventional SPME-LC systems. The parameters for preconcentration have been investigated for the extraction capillary with the newly developed 'wire-in-tube' configuration.     

Stability-indicating densitometric determination of some antidiabetic drugs in dosage forms, using TLC

The most commonly used antidiabetic sulfonylurea drugs, gliclazide, glipizide and glibenclamide, were determined using stability-indicating densitometric methods. The degradation products were prepared by acid hydrolysis of the intact drugs. Thin layer chromatography was carried out using silica gel 60 F₂₅₄ plates and different mobile phases, followed by scanning of the developed chromatograms. Mixtures of the investigated drugs and their degradation products were prepared and analysed using the proposed methods, with recovery in the range 100.4–101.0% and RSD in the range 0.6–0.7%. Pharmaceutical dosage forms were assayed and found to give results of the same accuracy and reproducibility as official or reference methods.     

Spectrophotometric Analysis of some Phenothiazine Neuroleptics using Chloramine-T

ABSTRACT

A sensitive and selective spectrophotometric method has been developed for the determination of six phenothiazine neuroleptics. The method is based on the interaction of the drugs with chloramine-T in sulphuric acid medium to yield a red, reddish-violet, orange or greenish-blue intermediate with maximum absorption at 500-636 nm. Beer's law is obeyed over the range 5-125 μg ml^?1 of the drugs. The apparent molar absorptivities were found to be in the range 1.04x10³ to 5.46x10³ 1.mol^?1cm^?1. The investigated drugs were assayed in tablets and injections. The mean percentage recoveries were 97.65-101.75 and the relative standard deviations were found to be less than 2%.     

Efficiency of small-bore HPLC-columns in different liquid chromatographs

Summary It is demonstrated that small-diameter (2 mm) columns can provide their full efficiency only if the instrument is specially designed for them. In general purpose commercial instruments actual column performance will only be a fraction of what the column is capable of providing, and deterioration is particularly evident with early peaks. With the more conventional 4.6-mm i.d. columns the difference is less significant although the design of the sample inlet system still plays a role. An equation is derived which permits prediction of actual column efficiency.     

Analysis of anthocyanin pigments in Lonicera (Caerulea) extracts using chromatographic fractionation followed by microcolumn liquid chromatography-mass spectrometry

Anthocyanins from the fruit Lonicera caerulea L. var. kamtschatica (blueberry honeysuckle, Caprifoliaceae) were studied via (semi)preparative chromatographic fractionation followed by MS and μLC/MS analysis. The extraction procedure was optimized with respect to analytical purposes as well as its potential use for the preparation of nutraceuticals. The highest yield of anthocyanins was obtained using acidified methanol as the extraction medium. A comparable total anthocyanin content was obtained using a mixture of methanol and acetone. However, when Lonicera anthocyanins were in contact with acetone, a condensation reaction occurred to a large extent and related 5-methylpyranoanthocyanins were found. The effect of other extraction media, including ethanol as a "green" solvent, is also discussed. The potential of two fractionation procedures for extract purification differing in their chromatographic selectivity and scale was studied (i.e. using a Sephadex LH-20 gel column and a reversed phase). Fractions obtained by both procedures were used for a detailed analysis. MS and μLC/MS(2) methods were used for monitoring anthocyanin and 5-methylpyranoderivatives content as well as identifying less common and more complex dyes (dimer of cyanidin-3-hexoside, cyanidin-ethyl-catechin-hexosides, etc.). These more complex dyes are most likely formed during fruit treatment.     

Determination of ferrocene-A in the blood serum of rabbits using reversed-phase microcolumn HPLC

Ferrocene-A (ferrocenyl-1-phenyl-1-dioxy-1,4-butin-2) has shown significant antitumour and antibacterial activity. To facilitate studies in this field a simple and rapid liquid chromatographic procedure was developed, allowing the determination of ferrocene-A in the blood serum. The procedure was based on a reversed-phase high-performance liquid chromatography (HPLC) method, with UV detection at 210 nm. The mobile phase ethanol-0.01 M KH2PO4 60:40 (v/v) provides the complete separation of ferrocene-A, internal standard and endogenous compounds of serum. The recovery of ferrocene-A from serum using a hexaneisoamyl alcohol mixture was 90%. The proposed method is convenient for pharmacological and pharmacokinetic applications.     

On-line precolumn enrichment of bisphenol A using boronate column in microcolumn liquid chromatography

The application of a boronate precolumn in the trace determination of 4,4'-isopropylidenediphenol (bisphenol A or BPA) in aqueous solution was investigated by microcolumn liquid chromatography (LC). BPA was enriched by a precolumn packed with TSK(gel) boronate and it was then injected (back-flushed) into an ODS separation column. Comparing to a conventional syringe injection, a better peak shape was obtained via the boronate precolumn injection, and the calculated theoretical plate number improvement was approximately two folds. The relative standard deviations for the retention time, peak area and peak height were 0.12, 3.0 and 1.8%, respectively. The system is linear (R2>0.99) within the working sample concentration and sample-volume ranges, and it presents a detection limit of 0.09 microg L(-1)(S/N=3) when a 0.2 mL sample was enriched. Recovery values of the proposed method were between 107 and 123%, and this method was applied satisfactorily to the determination of BPA in commercially available bottled drink samples. The boronate precolumn was proven to produce better sensitivity than that of an ODS or C30 precolumn as long as the enrichment of BPA in aqueous samples is concerned.