Development of a Method for the Measurement of Human Scent Samples Using Comprehensive Two-Dimensional Gas Chromatography with Mass Detection

Every human body is a source of a unique scent, which can be used for medical or forensic purposes. Human skin scent is a complex mixture of more or less volatile compounds with different chemical and physical properties, which often differ significantly in their concentrations. The most efficient technique for separating such complex samples is comprehensive two-dimensional gas chromatography (GC × GC). This work aimed to find the optimal arrangement of a two-dimensional chromatographic system and define a suitable chromatographic method for non-targeted analysis of human scent samples. Four different chromatographic columns (non-polar Rxi-5MS and TG-5HT, medium polar Rxi-17Sil MS and Rtx-200MS) and their different configurations were tested. The best system was the 30 m primary column Rtx-200MS (with the 2 m pre-column Rtx-200MS) and the 1 m secondary column TG-5HT in a reverse configuration. This system achieved the highest theoretical and conditional peak capacities, optimal resolution, and the lowest number of coelutions.

An Internal Standard High-Performance Liquid Chromatography Method for Simultaneous Quantification of Candesartan and Hydrochlorothiazide in Combined Formulations

The internal standard method is a versatile procedure that avoids misleading results caused by the instability of the chromatographic system or inexperienced workers. It is an effective way to judge the accuracy of any obtained data. As the detector responses of chlorzoxazone (CZN) resemble those of candesartan (CDZN) and hydrochlorothiazide (HCTZ), CZN was employed as an internal standard. Herein, a simple chromatographic method was established for quantification of CDZN and HCTZ. Isocratic elution was conducted using 1% premixed acetonitrile/formic acid (7:3 v/v) at a 0.8 mL/min flowrate. The separation of the three components was maintained using the universal 20 µL loop, and for further simplicity in application, the analysis was optimized at 25 °C. CDZN, HCTZ, and CZN were simultaneously monitored and quantified at 270 nm. The method developed here complies with all the validation limits according to the British Pharmacopoeia (BP), United States Pharmacopoeia (USP), and the guidelines of the International Council ForHarmonisation (ICH). The method proved to be linear in the range of 6.4 to 25.6 µg/mL and 5.0–20 µg/mL for CDZN and HCTZ, respectively, while the quantitation detection limits were less than 1.0µg/mL for both.

Enantiomeric purity deviations of radiolabelled amino acids obtained from chiral columns

Enantiomeric purity (EP) is an important value which denotes the relative percentage of the L-isomer with respect to the D-isomer. For 11C and 18F-labelled amino acid (AA) radiopharmaceutical (RP) production, EP represents a quality control parameter specified in European and national monographs for particular RPs. In most instances, EP value of greater then 90 or 95% (depending on AA type) is required as part of the quality control (QC) value of a RP following radiosynthesis. In common practice, two chromatographic columns are used for the EP determination of RPs: Crownpak CR(+) (Daicel), which contains a crown ether stationary phase or Chirobiotic T (Astec), which contains silica-bound glycoproteins as the stationary phase. The application of column Crownpak CR(+) requires that only perchloric acid solution (with pH 1–2) may be used, as the retention capability of the stationary phase is greatly reduced using organic solvents. This work intends to identify which chromatographic system is more accurate and reliable for EP determination as part of QC. We performed a series of parallel injections of the same batch of the widely used AA RPs [11C]MET and [18F]FET on the two aforementioned columns. The EP determination using column Crownpak CR(+) consistently provided a lower EP value compared to the Chirobiotic T column; the EP deviation between the respective columns was found to range from 2.4–4.0% for the same RP sample. Furthermore, the EP value was influenced by a sample’s dilution factor, e.g. the EP was observed to increase up to 1.5% when the radioactive sample had a fivefold dilution factor. This phenomenon was consistent for both Crownpak CR(+) and Chirobiotic T columns. Finally, a series of standard solutions of non-radioactive methionine with various ratios of L-and D-isomers was analyzed. The data obtained for non-radioactive methionine confirmed that column Crownpak CR(+) incorrectly provided a higher D-enantiomer concentration, whereas Chirobiotic T was found to provide a lower D-enantiomer concentration of the same sample. The deviation from the theoretical EP value was between 0.67 and 1.92%.

Effects of Microenvironmental Changes on the Fluorescence Signal of Alternariol: Magnesium Induces Strong Enhancement in the Fluorescence of the Mycotoxin

Alternariol (AOH) is an emerging mycotoxin produced by Alternaria molds. It occurs as a contaminant e.g., in oilseeds, cereals, grapes, and tomatoes. Chronic exposure to AOH may cause genotoxic and endocrine disruptor effects. Our recent studies demonstrated that the fluorescence signal of AOH can be strongly affected by the environmental pH as well as by the presence of serum albumin or cyclodextrins. In the current study, we aimed to characterize the most optimal circumstances regarding the highly sensitive fluorescent detection of AOH. Therefore, the further detailed investigation of the microenvironment on the fluorescence signal of the mycotoxin has been performed, including the effects of different buffers, organic solvents, detergents, and cations. Organic solvents (acetonitrile and methanol) caused only slight increase in the emission signal of AOH, while detergents (sodium dodecyl sulfate and Triton-X100) and Ca2+ induced considerably higher enhancement in the fluorescence of the mycotoxin. In addition, Mg2+ proved to be a superior fluorescence enhancer of the AOH. Spectroscopic and modeling studies suggest the formation of low-affinity AOH-Mg2+ complexes. The effect of Mg2+ was also tested in two HPLC assays: Our results show that Mg2+ can considerably increase the fluorescence signal of AOH even in a chromatographic system.

Polyaniline modified silica gel coupled with green solvent as eco favourable mobile phase in thin layer chromatographic analysis of organic dyes

This article studies a new green eco-friendly TLC (thin layer chromatography) using silica gel and polyaniline modified silica gel as stationary phase in combination with ethyl acetate (EA), n-butyl acetate (BA) and butane-1-ol (BO) solutions as mobile phase for the comparative study of migration behaviour of organic dyes to identify the most suitable thin layer chromatographic system for the resolution of co-existing dyes. Better separation efficiency was observed by modifying silica gel with polyaniline as compared to pure silica stationary phase. Densitogrpahic presentation of separations achieved on polyaniline modified silica gel Pani@SG-EB1 was also presented. The thin layer chromatographic system comprising of polyaniline modified silica gel Pani@SG-EB1 as stationary phase and n-butyl acetate:DDW, 5:5 as green mobile phase was observed to be the most favourable for the separation of various combinations of three or four-component mixtures of organic dyes viz. methyl thymol blue, tartrazine, carmoisine, rose bengal, amidoblack 10B, bromopyrogallol red and 4-nitrobenzene dizonium tetrafluoroborate. The effect of presence of cations and anions on separation trend was also examined and the limits of detection of the separated organic dyes were estimated. Fourier transform infrared spectroscopy (FTIR), x-ray diffraction (XRD), scanning electron microscopy (SEM) and transmission electron micrograph (TEM) studies were undertaken to characterize silica gel and modified silica gel (stationary phase). The developed method has been successfully applied for the identification of carmoisine in Solvin cold DS syrup and tartrazine in MefastTM syrup.

Method Development and Validation of Droxidopa by RP-UPLC

A simple, rapid, accurate and economical method has been developed for the quantification of droxidopa by UPLC. The chromatographic system was equipped with Phenomenex column C18 (50mm x 3.0mm, 3µ) as stationary phase and UV detector at 235nm, in conjunction with a mobile phase of buffer: methanol (25:75 % v/v ratio) at a flow rate of 1.0mL/min. Linearity was observed over the concentration range of 100-300µg/mL for droxidopa. The droxidopa peak eluted at 0.35 min. The recovery of Droxidopa was found to be 100.17% - 100.63% respectively. Statistical techniques were employed for the validation of precision, linearity, accuracy, robustness and ruggedness and can be applied for routine analysis. Validation revealed that the developed method was specific, accurate, precise, reliable, robust, reproducible and suitable for the routine quantitative analysis.

Banned Organochlorine Pesticides Residues in Camel Milk, Meat, and Liver: A Case Study from Jordan

Although most of the organochlorine pesticides have been banned from use and trade in Jordan, their residues remain still present in different environmental and food matrices. Because of the need to clarify the current status of pesticide contamination in Jordan, the present study has investigated the extent of contamination in camel milk, meat, and liver. One hundred eighty samples of camel milk, meat, and liver have been analyzed for their residual contents of dichlorodiphenyltrichloroethane and related metabolites, hexachlorohexane isomers, aldrin, dieldrin, endrin, heptachlor, heptachlor epoxide, and hexachlorobenzene. These samples were Soxhlet-extracted, cleaned up using florisil-column chromatography, and analyzed using a gas chromatographic system equipped with the electron-capture detector. Results: 31.7, 35, and 38.8% of the examined milk, meat, and liver samples, respectively, were contaminated with organochlorine pesticides. In general, obtained results have confirmed that pesticide contamination is still a significant concern when speaking of environmental samples and food in Jordan. More research is needed in this ambit. The pesticide contamination appears relevant enough in camel milk and liver samples, suggesting the need for reliable maximum residue levels where absent.

DEVELOPMENT AND VALIDATION OF QUANTITATIVE DETERMINATION METHOD OF DIHYDROSTREPTOMYCIN SULPHATE AND PROCAINE BENZYLPENICILLIN IN INJECTION SUSPENSIONS

The aim of the work was to develop and validate a method for the simultaneous identification and quantification of dihydrostreptomycin and benzylpenicillin in injectable suspensions. The method was validated by testing two preparations in the form of injectable suspensions containing benzylpenicillin 108–144 mg/ml and dihydrostreptomycin 180–220 mg/ml. Test samples were dissolved in purified water P, and standard samples: benzylpenicillin - in methanol (up to a concentration of 126 μg/ml), dihydrostreptomycin - in purified water P (up to a concentration of 200 μg/ml). The maximum allowable total uncertainty of the analysis was 1.64%, which is within the recommendations of SFU 2.0. The samples were separated on a Dionex Ultimate 3000 chromatograph equipped with a Luna C18 (2) 250 × 4.6 mm, 5 μm chromatographic column. The mobile phase was a mixture of acetonitrile and a solution of 0.01 M sodium heptanesulfonate with 0.05 M sodium phosphate trisubstituted, acidified with 0.1 M phosphoric acid to pH 6.0, in a volume ratio of 2: 8. Under mentioned conditions, dihydrostreptomycin and benzylpenicillin were completely separated. The established parameters of the chromatographic system did not exceed the limits specified in the FDA recommendations. The calibration curves were linear in the recommended SFU 2.0 range (80–120% of the nominal concentration of the corresponding active substance). The ratio of the amount of standard sample added to the test samples with its subsequent detection in the preparation was 99.35–100.79% for benzylpenicillin and 99.49–100.12% for dihydrostreptomycin, which does not exceed the limits recommended in SFU 2.0. The precision criterion was 0.07 for dihydrostreptomycin and -0.08 for benzylpenicillin, which is within the limits recommended in SFU 2.0. At the same time, the results of the study by different analysts at different times differed by 1.3% for dihydrostreptomycin and 0.98% for benzylpenicillin, which is well within the limits adopted in the recommendations of the FDA and SFU 2.0. Therefore, the method developed and validated by us for the simultaneous determination of dihydrostreptomycin sulfate and benzylpenicillin procaine in injectable suspensions can be considered suitable for routine analysis.

A REVIEW ON FLASH CHROMATOGRAPHY AND ITS PHARMACEUTICAL APPLICATIONS

Earlier column chromatography was used for preparative purposes as well as for reaction control in organic synthesis. Column chromatography is an extremely tedious stage in any laboratory and can quickly become a point of congestion for any process lab. Flash chromatography is a technique developed as a modification of preparative column chromatography. This is an air pressure driven technique comprising of medium and short column chromatography, optimised for rapid separation of organic compounds. Modern flash chromatographic system consists of pre- packed plastic cartridges where in the solvent is pumped through the cartridge. By employing high pressure gas, the efficiency and speed of classical column chromatography can be increased. Flash chromatography is an easy & quick approach that is economical to preparative liquid chromatography. The content mentioned in this article mainly focuses on the various components, general principles, procedures and applications of flash chromatography.