Quantification of the enantiomers of ofloxacin in biological fluids by high-performance liquid chromatography

Two methods for the determination of (+)- and (-)-ofloxacin in biological fluids by high-performance liquid chromatography are described. The first method is separation on a chiral stationary phase with bovine serum albumin immobilized on silica gel. The second is the coupling of ofloxacin to L-leucinamide via diphenylphosphinyl chloride activation. The diastereoisomeric derivatives are then separated on a common reversed-phase column. The second method revealed only slight differences in the pharmacokinetics of (+)- and (-)-ofloxacin in humans after an intravenous administration of racemic ofloxacin.     

Quantification of neurotransmitter amino acids by capillary electrophoresis laser-induced fluorescence detection in biological fluids

The role of neurotransmitter amino acids (NAAs) in the functioning of the nervous system has been the focus of increasingly intense research over the past several years. Among the various amino acids that have important roles as neurotransmitters, there are alanine (Ala), glutamic acid (Glu), aspartic acid (Asp), serine (Ser), taurine (Tau) and glycine (Gly). NAAs are present in plasma, cells and—at trace levels—in all biological fluids, but complex components in biological matrices make it difficult to determine them in biological samples. We describe a new capillary electrophoresis (CE) method with laser-induced fluorescence detection by which analytes are resolved in less than 12 minutes in a 18 mmol/L phosphate run buffer at pH 11.6. The use of elevated temperatures during sample derivatization leads to a drastic reduction in the reaction time, down to 20 min, compared to the 6–14 h usually described for reactions between FITC and amino acids at room temperature. In order to demonstrate its wide range of applications, the method was applied to the analysis of NAA in human plasma and in other sample types, such as red blood cells, urine, cultured cells, cerebrospinal fluid, saliva and vitreous humor, thus avoiding the typical limitations of other methods, which are normally suitable for use with only one or two matrix types.     

A micromethod for the determination of selenium in tissues and biological fluids by single-test-tube fluorimetry

A sensitive single-test-tube procedure for the fluorimetric determination of ng quantities of selenium with diaminonaphthalene, from small samples of animal origin is described. Several parameters related to the nitric/perchloric/sulphuric acid digestion, subsequent reduction and piazselenol formation are studied using blood as the matrix. The detection limit is 0.45 ng Se. The within-series precision for blood and heart tissue is 4.2% and 2.3% and between series is 5.0% and 3.6%, respectively. Recovery of added selenite and selenomethionine to blood, heart tissue and urine ranges from 98–101%. The correlation coefficient between the proposed and an electrothermal atomic absorption spectrometric method for serum samples is 0.997. This procedure is especially suitable for serial operation with a daily (8-h) throughput of 25 samples in duplicate.     

Challenges in determining perchlorate in biological tissues and fluids: implications for characterizing perchlorate exposure

The ability to measure environmental contaminants in biological tissues and fluids is important in the characterization of exposure. However, the analysis of certain contaminants in these matrices presents significant challenges. Perchlorate (ClO₄⁻) has emerged as a potential contaminant of concern primarily in drinking water and also in contaminated food. Significant advances have been made in the analysis of perchlorate in environmental matrices (water, soil) by ion chromatography (IC). In contrast, the analysis of perchlorate in extracts of biological tissues and fluids (vegetation, organs, milk, blood, urine, etc.) presents several challenges including small sample sizes, extracts with high matrix conductivity, and co-elution of other ions during IC analysis. To be able to detect low concentrations of perchlorate in biological samples, interferences must be removed or minimized, such as through the use of preparative chromatography cleanup techniques and/or alternative analytical methods less susceptible to common interferences (preconcentration or mass spectrometric detection). We present discussion and examples of the challenges encountered in the analysis of tissue extracts and fluids for perchlorate by IC and how some of those analytical challenges have been overcome.     

High-pressure liquid chromatographic determination of thioridazine and its major metabolites in biological tissues and fluids

A method is described for the determination of thioridazine and its major metabolites in postmortem tissues and fluids by enzymic digestion, followed by a micro-extraction technique using ethyl acetate. Quantitation was performed by using a cyano-bonded silica (mu Bondapak-CN) column packing and a mobile phase consisting of n-octylamine, methanol, and water.     

Spectrophotometric determination of diphenhydramine hydrochloride in pharmaceutical preparations and biological fluids via ion-pair formation

A simple, sensitive and accurate spectrophotometric method has been described for the assay of diphenhydramine hydrochloride (DPH) in raw material and in biological samples. The method is based on extraction of DPH into dichloromethane as ion-pair complexes with patent blue (PB), eriochrome black T (EBT), methyl orange (MO) and bromocresol purple (BCP) in acidic medium. The coloured species exhibited absorption maxima at 632, 514, 428 and 414 nm for PB, EBT, MO and BCP, with molar absorptivity values of 1.32 × 10⁵, 2.36 × 10⁴, 3.68 × 10⁴ and 3.07 × 10⁴ l mol^?1 cm^?1, respectively. The reaction conditions were optimized to obtain the maximum colour intensity. Beer’s law was obeyed with a good correlation coefficient (0.9982–0.9993) in the concentration ranges 0.5–3, 2.0–16, 2.0–10 and 1.0–10 μg ml^?1 for PB, EBT, MO and BCP methods, respectively. The composition ratio of the ion-association complexes was found to be 1:1 in all cases as established by Job’s method. The conditional stability constant (K_f) and the free energy changes (ΔG°) were determined for all complexes formed. The proposed method was successfully applied for the determination of DPH in tablets and human urine with good accuracy and precision. Statistical comparison of the results with those obtained by the official method showed good agreement and indicated no significant difference in accuracy and precision.     

Estimation of diuretic drugs in biological fluids by HPLC

Summary This critical review of different methods proposed for the determination and screening of diuretics is directed mainly, because of its potential application, towards highperformance liquid chromatography.     

Solid-phase extraction based on hydrophilic interaction liquid chromatography with acetone as eluent for eliminating matrix effects in the analysis of biological fluids by LC-MS

Analysis of drugs and metabolites in biological matrices such as blood or plasma by LC-MS is routinely challenged by the presence of large quantities of competing molecules for ionization in soft ionization sources, such as proteins and phospholipids. While the former can easily be removed by protein precipitation, pre-analytical extraction of the latter is necessary because they show very high retention in reversed-phase LC resulting in long analysis times or in ion suppression effects when not eluted before the next runs. A novel HILIC-based SPE approach, making use of silica cartridges and of acetone as organic solvent, is introduced as a potent alternative to current commercial methods for phospholipid removal. The methodology was developed and tested for a broad polarity range of pharmaceutical solutes (log P from 0 to 6.6) and broad applicability can therefore be envisaged.     

Determination of histamine in biological fluids by capillary isotachophoresis and fluorescence

Analytical isotachophoresis was used for the determination of histamine in biological fluids. For biological fluids with a very low content of histamine a method was developed that combines the fluorescing condensation product of histamine and o-phthaldialdehyde with the high concentration effect of isotachophoresis. This method permits the determination of histamine in serum and other biological fluids down to less than 3 ng/ml.     

Quantification of the plant-derived hallucinogen Salvinorin A in conventional and non-conventional biological fluids by gas chromatography/mass spectrometry after Salvia divinorum smoking

A gas chromatography method with mass spectrometric detection is described for the determination of Salvinorin A, the main active ingredient of the hallucinogenic mint Salvia divinorum. The method was validated in plasma, urine, saliva and sweat using 17-alpha-methyltestosterone as internal standard. The analytes were extracted from biological matrices with chloroform/isopropanol (9:1, v/v). Chromatography was performed on a 5% phenyl methyl silicone capillary column and analytes were determined in the selected ion monitoring mode. The method was validated over the concentration range 0.015-5 microg/mL plasma, urine and saliva and 0.01-5 microg/patch in the case of sweat. Mean recoveries ranged between 77.1 and 92.7% for Salvinorin A in different biological matrices, with precision and accuracy always better than 15%. The method was applied to the analysis of urine, saliva and sweat from two consumers after smoking 75 mg plant leaves to verify the presence of the active ingredient of S. divinorum in human biological fluids as a biomarker of plant consumption. Salvinorin A was detected in urine (2.4 and 10.9 ng/mL) and saliva (11.1 and 25.0 ng/mL), but not in sweat patches from consumers.     

Determination of thallium in autopsy tissues and body fluids by spectrophotometric technique

Microchimica Acta - A sensitive and specific Spectrophotometric technique for the determination of microgram amounts of thallium in autopsy tissues and body fluids is described. The material is...     

Quantification of domoic acid in shellfish tissues by pressurized capillary electrochromatography

A method was developed to quantify domoic acid (DA), the chemical responsible for amnesic shellfish poisoning (ASP), by pressurized CEC (pCEC). The effect of different experimental conditions on the separation of DA and matrix solutes, such as the content of ACN in mobile phase, pH and concentration of buffer, supplementary pressure and applied voltage, were investigated. Under the optimal conditions, the pCEC method separated DA from shellfish matrices within 6 min. By using supplementary pressure, bubble formation in the capillary column was completely suppressed. The method was repeatable, sufficient accurate and sensitive for rapid screening of DA in shell seafood.     

An overview of the analytical methods for the determination of organic ultraviolet filters in biological fluids and tissues

Organic UV filters are chemical compounds added to cosmetic sunscreen products in order to protect users from UV solar radiation. The need of broad-spectrum protection to avoid the deleterious effects of solar radiation has triggered a trend in the cosmetic market of including these compounds not only in those exclusively designed for sun protection but also in all types of cosmetic products.