Two-dimensional liquid chromatography with reversed phase in both dimensions: A review

Two-dimensional liquid chromatography (2D-LC), and in particular comprehensive two-dimensional liquid chromatography (LC×LC), offers increased peak capacity, resolution and selectivity compared to one-dimensional liquid chromatography. It is commonly accepted that the technique produces the best results when the separation mechanisms in the two dimensions are completely orthogonal; however, the use of similar separation mechanisms in both dimensions has been gaining popularity as it helps avoid difficulties related to mobile phase incompatibility and poor column efficiency. The remarkable advantages of using reversed phase in both dimensions (RPLC×RPLC) over other separation mechanisms made it a promising technique in the separation of complex samples. This review discusses some physical and practical considerations in method development for 2D-LC involving the use of RP in both dimensions. In addition, an extensive overview is presented of different applications that relied on RPLC×RPLC and 2D-LC with reversed phase column combinations to separate components of complex samples in different fields including food analysis, natural product analysis, environmental analysis, proteomics, lipidomics and metabolomics.

Green comprehensive two-dimensional liquid chromatography (LC × LC) for the analysis of phenolic compounds in grape juices and wine

Grape juices and wines are rich in numerous groups of polyphenolic compounds which require a dedicated separation technique for such complex samples. LC × LC is considered the best technique for the analysis of such samples as it can achieve better resolution and higher peak capacity compared to 1D LC. The ever-growing demand for protecting the environment necessitates reducing or eliminating hazardous solvents to improve the environmental friendliness of analytical procedures. In this study, propylene carbonate was used as an eco-friendly mobile phase component in comprehensive two-dimensional liquid chromatography to analyze phenolic compounds in grape juices and a dealcoholized wine sample. Novel green RPLC × RPLC-DAD and RPLC × RPLC-MS methods were developed for the first time to identify phenolic compounds in five samples (two red grape juice samples, two white grape juice samples, and one dealcoholized wine sample). Four different RPLC × RPLC systems were developed; three systems were connected to a diode array detector (RPLC × RPLC-DAD), while the fourth system was connected to DAD and MS detectors (RPLC × RPLC-DAD-ESI-MS). Solvent X (propylene carbonate:ethanol, 60:40) was adopted as a green organic modifier in the first dimension (¹D) and methanol in the second dimension (²D). The practical peak capacity and the surface coverage were calculated as metrics to measure the separation performance of all proposed systems. The orthogonality values for the setups ranged from 0.64 to 0.92 when calculated by the convex hull method, and from 0.54 to 0.80 when calculated by the asterisk equations method. The practical peak capacity production rate ranged from 14.58 to 22.52 peaks/min. The results revealed that the phenolic compounds were separated efficiently with good coverage of the 2D separation space and high peak capacity. A total of 70 phenolic compounds were detected based on MS data and information from the literature.

Green Approaches to Sample Preparation Based on Extraction Techniques

Preparing a sample for analysis is a crucial step of many analytical procedures. The goal of sample preparation is to provide a representative, homogenous sample that is free of interferences and compatible with the intended analytical method. Green approaches to sample preparation require that the consumption of hazardous organic solvents and energy be minimized or even eliminated in the analytical process. While no sample preparation is clearly the most environmentally friendly approach, complete elimination of this step is not always practical. In such cases, the extraction techniques which use low amounts of solvents or no solvents are considered ideal alternatives. This paper presents an overview of green extraction procedures and sample preparation methodologies, briefly introduces their theoretical principles, and describes the recent developments in food, pharmaceutical, environmental and bioanalytical chemistry applications.

Development of spectrofluorimetric method for determination of certain aminoglycoside drugs in dosage forms and human plasma through condensation with ninhydrin and phenyl acetaldehyde

A simple and sensitive spectrofluorimetric method has been developed and validated for determination of amikacin sulfate, neomycin sulfate and tobramycin in pure forms, pharmaceutical formulations and human plasma. The method was based on condensation reaction of cited drugs with ninhydrin and phenylacetaldehyde in buffered medium (pH 6) resulting in formation of fluorescent products which exhibit excitation and emission maxima at 395 and 470nm, respectively. The different experimental parameters affecting the development and stability of the reaction products were carefully studied and optimized. The calibration plots were constructed with good correlation coefficients (0.9993 for tobramycin and 0.9996 for both neomycin and amikacin). The proposed method was successfully applied for the analysis of cited drugs in dosage forms with high accuracy (98.33-101.7)±(0.80-1.26)%. The results show an excellent agreement with the reference method, indicating no significant difference in accuracy and precision. Due to its high sensitivity, the proposed method was applied successfully for determination of amikacin in real human plasma.

Highly sensitive spectrofluorimetric method for determination of certain aminoglycosides in pharmaceutical formulations and human plasma

A simple, reliable, highly sensitive and selective spectrofluorimetric method has been developed for determination of certain aminoglycosides namely amikacin sulfate, tobramycin, neomycin sulfate, gentamicin sulfate, kanamycin sulfate and streptomycin sulfate. The method is based on the formation of a charge transfer complexes between these drugs and safranin in buffer solution of pH 8. The formed complexes were quantitatively extracted with chloroform under the optimized experimental conditions. These complexes showed an excitation maxima at 519-524 nm and emission maxima at 545-570 nm. The calibration plots were constructed over the range of 4-60 pg mL(-1) for amikacin, 4-50 pg mL(-1) for gentamicin, neomycin and kanamycin, 4-40 pg mL(-1) for streptomycin and 5-50 pg mL(-1) for tobramycin. The proposed method was successfully applied to the analysis of the cited drugs in dosage forms. The proposed method was validated according to ICH and USP guidelines with respect to specificity, linearity, accuracy, precision and robustness. The high sensitivity of the proposed method allowed determination of amikacin and gentamicin in spiked and real human plasma.

Association of angiotensin converting enzyme gene (I/D) polymorphism with hypertension and type 2 diabetes

OBJECTIVES

This study was conducted to determine the association of insertion/deletion (I/D) polymorphism of the ACE gene in hypertensive and T2DM subjects in Egyptian population.

BACKGROUND

The deletion (D) allele of the angiotensin-converting enzyme (ACE) gene has been studied in relation to hypertension and type 2 diabetes mellitus (T2DM) with contradictory results which might be due to ethnic and geographical variations.

METHODS

A total of 85 subjects participated in this study; hypertension (Group 1); type 2 diabetes mellitus (Group 2) and controls (Group 3). Written informed consent was obtained. for each subject: age, sex, diabetes duration and the drugs used, blood pressure (systolic and diastolic), and lipid profile. Genotyping was performed by polymerase chain reaction (PCR).

RESULTS

The frequency of DD genotype was significantly higher in hypertensive (60 %) and diabetic patients (68 %) compared to controls (33.3 %) (p=0.04, p=0.01 respectively). The DD genotype (vs DI and II genotype) in the hypertensive and diabetic groups is associated with increased risk of hypertension and/or diabetes. OR=3.00; 95%, Cl = 0.993-9.067; OR=4.250; 95%, Cl = 1.234-14.63 respectively). The D allele was more frequent in hypertensive (77.5 %) and diabetic patients (82 %) compared to controls (52.4 %) (p=0.004 and 0.002 respectively). The D allele (vs the I allele) is associated with increased risk of hypertension and diabetes OR=3.13, 95%Cl=1.405-6.978; OR= 4.14, 95% CI= 1.615-10.622 respectively).

CONCLUSION

The DD genotype and the D allele are associated with hypertension and type 2 diabetes in Egyptian patients (Tab. 5, Fig. 1, Ref. 32).

Quantum mechanical calculations of the cephalosporin nucleus

A computational study using several ab initio methods, HF, DFT and MP2 at different basis set levels (6-31G*, 6-31G**, 6-311G** and 6-311++G**) has been performed to determine the possible stable conformations attained by the cephalosporin nucleus. The calculations were carried out in three stages by studying the conformational analysis of the 3-cephem nucleus, the 3-cephem-4-carboxylic acid nucleus and the acetylamino group of the 7-acetylamino-3cephem-4-carboxylic acid. In the first two stages, the potential energy surfaces indicated two minima that correspond to the S1-up and C2-up conformations, with the S1-up being more stable. The energy required for the interconversion of the S1-up to the C2-up is around 7 kcal/mol, indicating the feasibility of interconversion between the two conformers. In the third stage, the acetylamino group attained two conformations with respect to the 3-cephem nucleus. All the geometric parameters obtained in this study were found to be in reasonably good agreement with available X-ray diffraction data, even upon using a simple basis set.

Calculation of heating power generated from ferromagnetic thermal seed (PdCo-PdNi-CuNi) alloys used as interstitial hyperthermia implants

High quality heating device made of ferromagnetic alloy (thermal seed) was developed for hyperthermia treatment of cancer. The device generates sufficient heat at room temperature and stops heating at the Curie temperature T (c). The power dissipated from each seed was calculated from the area enclosed by the hysteresis loop. A new mathematical formula for the calculation of heating power was derived and showed good agreement with those calculated from hysteresis loop and calorimetric method.

Variation in Sensitivity Among Some Isolates of Macrophomina phaseolina Isolated from Cotton Roots to Flutolanil Fungicide

Toxicity of the fungicide Flutolanil was in vitro tested against 20 isolates of Macrophomina phaseolina and cotton seedlings of ten commercial cotton cultivars. The isolates were recovered from roots of cotton plants obtained from different cotton-growing areas in Egypt. Most of the tested isolates were sensitive to Flutolanil; however, they varied in sensitivity. Twenty-five percent of the isolates were highly sensitive where IC50 ranged from < 1 to 5.1 µg/ml, 20% of the isolates were sensitive where IC50 ranged from 15 to 30 µg/ml, 45% of the isolates were moderately sensitive where IC50 ranged from 46 to 58.5 µg/ml, and 10% of the isolates were not much sensitive (tolerant) where IC50 was > 100 µg/ml. Flutolanil was very safe on both shoots and roots of the tested cultivars (IC50 > 100 µg/ml). Treating cotton seeds with Flutolanil resulted in highly significant (P < 0.01) reductions in pathogenicity of 18 isolates and a significant reduction (P < 0.05) in pathogenicity of isolate M29. M1 was the only isolate, which was insensitive to the application of Flutolanil. In vivo toxicity to Flutolanil was not correlated with its in vitro toxicity. However, a highly significant correlation (r = 0.60, P < 0.01) was observed between pathogenicity of isolates and the in vivo toxicity of the fungicide.

Simple synthesis of novel diphenylsulfapyrimidine acetates from chalcones and their antimicrobial activity

Given the significant low yield (19-43%) in reported results on the cyclocondensation of sulfaguanidine acetate with chalcones, a careful reinvestigation was carried out. A new series of chalcones, bearing electron-attracting groups in the aromatic moiety, have been used as precursors in the synthesis of diphenylsulfapyrimidine acetates with good yield. All synthesized compounds were active against G(+)- and G(-)-bacteria, and fungi. Combination of substituents (Cl, OMe, NO2, etc.) enhanced antimicrobial activity. Derivative with two NO2 groups exhibits an activity comparable with sulfadiazine.

Alpha,beta-unsaturated 4-oxo acids in heterocylic synthesis. II. Behavior of 3-(1,1-dioxadibenzothein-4-oyl)acrylic acid towards carbon nucleophiles under Michael reaction condition

3-(1,1-Dioxadibenzothien-4-oyl)acrylic acid (1) was condensed with compounds containing active methylene groups under Michael reaction conditions to furnish the Michael adducts (lactones 2a-c, lactams 3a-c, ketones 4a,b). The behavior of these adducts toward the action of hydrazine hydrate were investigated. The compounds were tested for their biological properties.

Phylogenetic classification of serotype III group B streptococci on the basis of hylB gene analysis and DNA sequences specific to restriction digest pattern type III-3

Previous work divided serotype III group B streptococci (GBS) into 3 major phylogenetic lineages (III-1, III-2, and III-3) on the basis of bacterial DNA restriction digest patterns (RDPs). Most neonatal invasive disease was caused by III-3 strains, which implies that III-3 strains are more virulent than III-2 or III-1 strains. In the current studies, all RDP III-3 and III-1 strains expressed hyaluronate lysase activity; however, all III-2 strains lack hyaluronate lysase activity, because the gene that encodes hyaluronate lysase, hylB, is inactivated by IS1548. Subtractive hybridization was used to identify 9 short DNA sequences that are present in all the III-3 strains but not in any of the III-2 or III-1 strains. With 1 exception, these III-3-specific sequences were not detected in nonserotype III GBS. These data further validate the RDP-based subclassification of GBS and suggest that lineage-specific genes will be identified, which account for the differences in virulence among the lineages.

Genetic polymorphisms of group B streptococcus scpB alter functional activity of a cell-associated peptidase that inactivates C5a

Many group B Streptococcus agalactiae strains and other pathogenic streptococci express a cell-associated peptidase that inactivates C5a (C5a-ase), the major neutrophil chemoattractant produced by activation of the complement cascade. Type III group B streptococci (GBS) can be classified genotypically into three restriction digest pattern types. Functional C5a-ase activity of GBS correlates with this genetic typing; therefore, we sought to identify a genetic basis for this phenomenon. Southern hybridization confirms that all type III GBS contain scpB, the gene encoding GBS C5a-ase. GBS strains with high C5a-ase functional activity and those with no or very low activity both express immunoreactive C5a-ase. The scpB sequence of strain I30, which has high C5a-ase activity, is 98.2% homologous to the previously reported serotype II GBS scpB sequence. The scpB sequences of strains I25 and GW, which have low or no C5a-ase activity, are identical. The predicted I25 and GW C5a-ase proteins share a four-amino-acid deletion affecting the protease histidine active-site consensus motif. Recombinant I30 C5a-ase has good functional activity, whereas recombinant I25 C5a-ase has low activity. These data demonstrate that functional C5a-ase differences between type III GBS strains are attributable to a genetic polymorphism of scpB. The ubiquitous expression of C5a-ase, irrespective of functional activity, suggests that C5a-ase may have a second, as yet unidentified, function.

Case survey of management of cellulitis in a tertiary teaching hospital

OBJECTIVE

To examine management of cellulitis in a tertiary teaching hospital, identify inefficiencies and suggest revised management guidelines.

DESIGN

Retrospective case survey, based on patient hospital records.

SETTING

Heidelberg Repatriation Hospital, Melbourne, Victoria (a tertiary teaching hospital), in 1991 and 1992.

SUBJECTS

All patients admitted with lower-limb cellulitis as the primary diagnosis.

RESULTS

118 patients were included. Underlying disease predisposing to cellulitis was found in 79%, but was adequately investigated in only 20% of these. Blood cultures were performed in 55%, all with negative results. Other microbiological investigations also had poor yields. Combination therapy with intravenous (i.v.) flucloxacillin and penicillin was given to 76%, with duration varying widely (mean, six days). Where documented (73%), most patients (94%) responded to antibiotics within five days. However, in 40% of patients i.v. therapy was continued for longer and in 10% for 10 days or more, with no significant difference in outcome. Length of hospital stay averaged 13 days, with prolonged stay often associated with surgical intervention or intercurrent problems. However, 15% of patients remained in hospital longer than 10 days for no clear indication. Outpatient review was common (75%), but persistence or relapse of cellulitis was found in only four patients on review.

CONCLUSIONS

Management of inpatients with cellulitis is inefficient, with excessive use of microbiological investigations, inadequate investigation and treatment of underlying disease, prolonged use of intravenous antibiotics, unnecessarily long hospital stays, questionable use of combination antibiotic therapy and excessive outpatient review (rather than review by a local medical practitioner).

Technetium-aspirin molecule complexes

Technetium-aspirin and technetium-aspirin-like molecule complexes were prepared. The structure of N-acetyl-anthranilic acid (NAA) has been decided through CNDO calculations. The ionization potential and electron affinity of the NAA molecule as well as the charge densities were calculated. Comparative studies of the electronic absorption spectra of acetylthio-salicylic acid (ATS) and aspirin (Asp) reveal the structure resemblance in which the acetyl carbonyl group is perpendicular to the plane of the corresponding organic acid. The studies of the electronic absorption spectra of NAA and anthranilic acid reveal the planarity of the NAA molecule. The electronic absorption spectra of Tc(V)-Asp and Tc(V)-ATS complexes have two characteristic absorption bands at 450 and 600 nm, but the Tc(V)-NAA spectrum has one characteristic band at 450 nm. As a comparative study, Mo-ATS complex was prepared and its electronic absorption spectrum is comparable with the Tc-ATS complex spectrum.

Synthesis of biologically active [2.2]paracyclophanes

Claisen reaction of 4-acetyl[2.2]paracyclophane (1) with ethyl acetate and diethyl oxalate affords 4-acetoacetyl[2.2]paracyclophane (2) and ethyl (4-oxaloacetyl[2.2]paracyclophane) (6), respectively. Reaction of 2 and 6 with hydrazines and CuCl2 gave the pyrazole derivatives 4 and 8 in addition to the metal complexes 5 and 9. Mannich reaction of 2 with benzylamine and paraformaldehyde yielded the piperidinone derivative 3. The biological activity of all new compounds was tested.

Growth characteristics of enterococci isolated from Laban Rayeb

Eleven strains of Enterococcus (Streptococcus) faecalis isolated from Laban Rayeb, a type of fermented milk, had been studied when grew in milk. Enterococcus (Streptococcus) faecalis strains 19 and 22 were the most active strains in the production of lactic acid, acetaldehyde and diacetyl. Both strains exhibited a high proteolytic activity besides a good clean flavour. Based on the obtained results, Enterococcus (Streptococcus) faecalis 19 and 22 could be used to bring about the lactic fermentation during the manufacture of some cultured dairy products.

Synthesis of some 5-azo(4'-substituted benzene-sulphamoyl)-8-hydroxyquinolines with antidotal and antibacterial activities

5-Azo(4'-substituted benzenesulphamoyl)-8-hydroxyquinolines(III) have been prepared by coupling of the appropriate p-substituted benzenesulphamoyldiazonium acetates with 8-hydroxyquinoline. The corresponding copper chelates(IV) and iron chelates(V) were also prepared in a 1:2 metal to ligand ratio. Structures of III, IV and V were confirmed by some representative UV, IR, and NMR spectrometry in addition to microanalysis. Antidotal activity of four ligands (IIIa, IIId, IIIf, and IIIi) has been evaluated in mice against the toxicity of lead acetate and copper sulphate. Study revealed that compound IIIf elicited significant antidotal activity against lead and copper poisoning, while IIIi was potent only against lead poisoning. Antibacterial activity of compounds III, IV, and V was also determined in comparison to sulphanilamide against Staph. aureus, Bacill. cereus, and Esch. coli. The test compounds showed variable bacteriostatic activities, and some of them (IIIc, IIId, IIIf, Ve, IIIg, and Vi) are more effective than the reference drug, especially against Bacill. cereus.

Properties of Labneh-Like Product Manufactured Using Enterococcus Starter Cultures as Novel Dairy Fermentation Bacteria

The traditional yogurt starter, i.e. Staphylococcus thermophilus and Lactobacillus bulgaricus , has always been used to bring about the lactic acid fermentation during manufacture of concentrated yogurt known in Egypt as "Labneh". Different combinations of some strains of Enterococcus faecalis , isolated from Laban Rayeb (a type of fermented milk), in combination with a certain strain of Lactobacillus bulgaricus were used to produce a Labneh-like product. Chemical, microbiological and organoleptic properties of the Labneh-like product were assessed and compared to the characteristics of Labneh processed traditionally by two different dairy plants in Egypt. All treatments showed similar changes during storage at 5 ± 1°C for 28 d. Total solids, fat, titratable acidity and pH values coincided with those of Labneh. Some components increased until the seventh day, i.e. acetaldehyde and diacetyl, while other features, such as the ratio of soluble nitrogen/total nitrogen and tyrosine, increased until the fourteenth day of storage. Thereafter, no marked variations occurred. However, a decrease in tryptophan content of all products occurred during the storage period. Total viable count and count of lactic acid bacteria of Labneh-like product as well as Labneh increased until the end of the second week of storage and then decreased. Coliforms, yeasts and molds and psychrotrophic bacteria were detected in some fresh and stored samples. The starter culture which consisted of 1.5% Enterococcus faecalis 19 and 1.5% Enterococcus faecalis 22 was used successfully to manufacture a Labneh-like product with high acceptability when fresh or refrigerated at 5 ± 1°C.