Sequential Second Derivative Spectroscopy of Cocaine and Adulterants in Street Drug Samples. Part I: Cocaine,Procaine, and Lidocaine

Abstract

A sequential spectrophotometric method for the resolution of mixtures of cocaine, procaine and lidocaine in powder samples is proposed. The analytes are determined sequentially in the following order: 1st-Procaine, 2^nd-Cocaine and 3^rd-Lidocaine. The three determinations are carried out in phosphate buffer at pH 7.8. This solvent was selected as alternative to 0.1M HCl and NaOH, because the spectral characteristics, solutions stability and reproductibility were suitable.     

Development and validation of gas chromatography-mass spectroscopy method for determination of prilocaine HCl in human plasma using internal standard methodology

The accurate determination of prilocaine HCl levels in plasma is important in both clinical and pharmacological/toxicological studies. Prilocaine HCl is quickly hydrolyzed to o-toluidine, causing methemoglobinemia. For this, the present work describes the methodology and validation of a GC-MS assay for determination of prilocaine HCl with lidocaine HCl as internal standard in plasma. The validation parameters of linearity, precision, accuracy, recovery, specificity, limit of detection and limit of quantification were studied. The range of quantification for the GC-MS was 20-250 ng/mL in plasma. Within-day and between-day precision, expressed as the relative standard deviation (RSD) were less than 6.0%, and accuracy (relative error) was better than 9.0% (n = 6). The analytical recovery of prilocaine HCl and IS from plasma has averaged 94.79 and 96.8%, respectively. LOQ and LOD values for plasma were found to be 20 and 10 ng/mL, respectively. The GC-MS method can be used for determination from plasma of prilocaine HCl in routine measurement as well as in pharmacokinetic studies for clinical use.     

Covalent bonding of homochiral metal‐organic framework in capillaries for stereoisomer separation by capillary electrochromatography

In this work, a [Cu(mal)(bpy)]?H₂O (mal, l ‐(?)‐malic acid; bpy, 4,4′‐bipyridyl) homochiral metal‐organic frameworks (MOFs) was synthesized and used for modifying the inner walls of capillary columns by utilizing amido bonds to form covalent links between the MOFs particles and capillary inner wall. The synthesized [Cu(mal)(bpy)]?H₂O and MOFs‐modified capillary column were characterized by X‐ray diffraction, thermogravimetric analysis, particle size distribution analysis, nitrogen absorption characterization, FTIR spectroscopy, SEM, and energy‐dispersive X‐ray spectroscopy (EDX). The MOFs‐modified capillary column was used for the stereoisomer separation of some drugs. The LODs and LOQs of six analytes were 0.1 and 0.25 μg/mL, respectively. The linear range was 0.25–250 μg/mL for ephedrine, 0.25–250 μg/mL for pseudoephedrine, 0.25–180 μg/mL for d ‐penicillamine, 0.25–120 μg/mL for l ‐penicillamine, 0.25–180 μg/mL for d ‐phenylalanine, and 0.25–160 μg/mL for l ‐phenylalanine, all with R² > 0.999. Finally, the MOFs‐modified capillary column was applied for the analysis of active ingredients in a real sample of the traditional Chinese medicine ephedra.     

Simultaneous determination of caffeine,paracetamol, and ibuprofen in pharmaceutical formulations by high‐performance liquid chromatography with UV detection and by capillary electrophoresis with conductivity detection

Paracetamol, caffeine and ibuprofen are found in over‐the‐counter pharmaceutical formulations. In this work, we propose two new methods for simultaneous determination of paracetamol, caffeine and ibuprofen in pharmaceutical formulations. One method is based on high‐performance liquid chromatography with diode‐array detection and the other on capillary electrophoresis with capacitively coupled contactless conductivity detection. The separation by high‐performance liquid chromatography with diode‐array detection was achieved on a C₁₈ column (250×4.6 mm², 5 μm) with a gradient mobile phase comprising 20–100% acetonitrile in 40 mmol L^?1 phosphate buffer pH 7.0. The separation by capillary electrophoresis with capacitively coupled contactless conductivity detection was achieved on a fused‐silica capillary (40 cm length, 50 μm i.d.) using 10 mmol L^?1 3,4‐dimethoxycinnamate and 10 mmol L^?1 β‐alanine with pH adjustment to 10.4 with lithium hydroxide as background electrolyte. The determination of all three pharmaceuticals was carried out in 9.6 min by liquid chromatography and in 2.2 min by capillary electrophoresis. Detection limits for caffeine, paracetamol and ibuprofen were 4.4, 0.7, and 3.4 μmol L^?1 by liquid chromatography and 39, 32, and 49 μmol L^?1 by capillary electrophoresis, respectively. Recovery values for spiked samples were between 92–107% for both proposed methods.     

Preparation and evaluation of a novel molecularly imprinted SPE monolithic capillary column for the determination of auramine O in shrimp

A novel method combining molecular imprinting and SPE was developed in a capillary column for the determination of auramine O in shrimp. The capillary monolithic column was prepared by UV‐initiated in situ polymerization, using auramine O as template and methacrylic acid and ethylene dimethacrylate as functional monomer and cross‐linker, respectively. The properties of the prepared capillary monolithic column were investigated under the optimized conditions coupled with HPLC, and then the morphologies of the inner polymers were characterized by SEM. The calibration curve was expressed as A = 103C + 19.8 (r = 0.9992) with a linear range of 0.25–25.0 μg/mL, and the recoveries of auramine O at different concentrations in shrimp ranged from 90.5 to 92.4% with RSDs ranging from 2.1 to 4.4%. The capacities of the molecularly imprinted polymer and nonimprinted polymer columns were 0.722 and 0.147 μg/mg, respectively, and the LOD (S/N = 3) of auramine O in shrimp was 17.85 μg/kg. Under the selected conditions, the enrichment factors obtained were higher than 70‐fold. The results indicate that the prepared molecularly imprinted capillary monolithic column was reliable and applicable to the analysis of auramine O in shrimp.     

Development and validation of a generic RP‐HPLC PDA method for the simultaneous separation and quantification of active ingredients in cold and cough medicines

A novel generic reverse phase high performance liquid chromatography (RP‐HPLC) method is developed and validated for simultaneous determination of seven pharmaceutically active ingredients, namely, acetaminophen, dextromethorphan, doxylamine, phenylephrine, guaifenesin, caffeine and aspirin. All seven ingredients were quantified in soft gel, syrup and tablet formulations of the over‐the‐counter US‐marketed products, as per the guidelines of the International Conference on Harmonization. The separation was achieved in a 16 min run time on an Agilent Zorbax Phenyl column using a gradient method with two mobile phases. Mobile phase A was 0.15% trifluoro acetic acid in purified water and while mobile phase B was a mixture of acetonitrile and methanol (750:250 v/v) with 0.02% trifluoro acetic acid. The flow rate was 1.0 mL min^?1 and injection volume was 10 μL. Detection was performed at 280 nm using a photodiode array detector. As part of the method validation, specificity, linearity, precision and recovery parameters were verified. The concentration and area relationships were linear (R² > 0.999), over the concentration ranges 20–120 μg mL^?1 for acetaminophen, 75–450 μg mL^?1 for dextromethorphan, 31.25–187.5 μg mL^?1 for doxylamine, 25–150 μg mL^?1 for phenylephrine, 25–150 μg mL^?1 for aspirin, 6.5–39 μg mL^?1 for caffeine and 12–72 μg mL^?1 for guaifenesin. The relative standard deviations for precision and intermediate precision were <1.5%. The proposed RP‐HPLC generic method is applicable for routine analysis of cold and cough over‐the‐counter products.     

Microtubules of polyaniline doped with HCl and HBF4

Microtubules of polyaniline (PANI) doped with HCl, HBF₄, and β-naphthalene sulfonic acid (NSA) were synthesized by an improved in situ doping polymerization method. Ultraviolet-visible spectra, scanning electron microscopy, ESR, and X-ray diffraction characterized the molecular structure of the resulting PANI microtubules. These microtubules had a diameter of 1 ∼ 10 μm and a conductivity at room temperature of 0.2 ∼ 3.5 S/cm, depending on the molecular structure and concentration of the dopant. The degree of crystallinity of the PANI microtubules was enhanced by increasing the molecular size of the dopant; that is, the order PANI-NSA > PANI-HBF₄ > PANI-HCl was observed in the crystallinity of the microtubules. © 1999 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 37: 4605–4609, 1999     

Enhanced HPLC‐MS/MS method for the quantitative determination of the co‐administered drugs ceftriaxone sodium and lidocaine hydrochloride in human plasma following an intramuscular injection and application to a pharmacokinetic study

A sensitive HPLC–MS/MS method was established for the quantification of ceftriaxone sodium (CFT) and lidocaine HCl (LDC) in human plasma utilizing cefixime (CFX) and tadalafil (TDA) as internal standards. The analytes were extracted from human plasma by protein precipitation using acetonitrile. Chromatographic separation was performed on Kinetex C₁₈ (50.0 × 4.6 mm, 5 μm particle size) column with methanol–0.01 M ammonium acetate pH 6.4 (70: 30, v/v) as mobile phase. Multiple reaction monitoring involving the transitions 555.10 → 396.20, 235.20 → 86.00, 454.20 → 284.80 and 390.20 → 268.20 was utilized to quantify CFT, LDC, CFX and TDA, respectively, using a triple quadrupole mass spectrometer which was operated in positive ion mode. The method revealed linearity in the concentration range of 3.0–300.0 μg/mL for CFT and 3.0–300.0 ng/mL for LDC. The validation of the method was achieved in accordance to the US Food and Drug Administration guidelines. A pharmacokinetic study was performed on healthy Egyptian volunteers after intramuscular injection of sterile ceftriaxone sodium (1 g CFT dissolved in 3.5 mL of 1% LDC) after approval from the ethics committee. The pharmacokinetic parameters were: C_max 141.15 ± 39.84 (μg/mL) and 55.02 ± 9.36 (ng/mL); t_max (h) 2.50 ± 0.50 and 1.5 ± 0.50; t_½ (h) 7.30 ± 2.98 and 4.23 ± 1.96; and K_el (h⁻¹) 0.10 ± 0.04 and 0.20 ± 0.13 for CFT and LDC, respectively.     

HPLC Separation of Theophylline,Paraxanthine, Theobromine,Caffeine and Other Caffeine Metabolites in Biological Fluids

Abstract

An HPLC method is described for rapid analysis of caffeine and seven of its metabolites in plasma, urine, milk and saliva in a single operation using a 5 μ C₁₈ reverse phase column. The metabolites are extracted with chloroform - iso-propanol (85:15) from 100 μL samples added to NH₄HCO₃. No interference from normal blood, urine, milk or saliva constituents was observed. The method is accurate and precise and separates 1,7-dimethylxanthine (paraxanthine) from 1,3-dimethylxanthine (theophylline). Sensitivity for most metabolites is in the range of 0.1 to 0.3 μg/mL and the detectability is at the nanogram level.     

Simple Strategy for Selective Determination of Levamisole in Seized Cocaine and Pharmaceutical Samples Using Disposable Screen‐printed Electrodes

Levamisole is the most common adulterant found in cocaine samples and its electrochemical determination in cocaine seized samples is a challenge due to peak overlapping with cocaine. Herein, we propose a deconvolution procedure for levamisole determination in seized cocaine samples using screen‐printed carbon electrodes (SPE). Square‐wave voltammetry in 0.04 mol L^?1 Britton Robinson buffered solution (pH 8.0) was selected in combination with optimized SWV parameters (f=8 s^?1, a=10 mV and ΔE_s=1 mV) to result in the best peak resolution to apply the deconvolution procedure. Deconvoluted responses of levamisole in the presence of cocaine were similar to untreated signals of standard levamisole solutions in absence of cocaine. A linear response was obtained in the range of 20–100 μmol L^?1 (r=0.995). The results obtained for the analysis of a seized cocaine sample was statistically similar to that obtained by gas chromatography. Other adulterants found in cocaine street samples (paracetamol, glucose, phenacetin, caffeine, boric acid and lidocaine) did not affect the treated of voltammetric responses of levamisole. A pharmaceutical sample containing levamisole was also analyzed on SPEs and a recovery of 93±2 % was obtained (no deconvolution required for this sample), showing great applicability of SPEs for forensic and pharmaceutical analyses.     

TLC Determination of Amitriptyline HCl,Trifluoperazine HCl,Risperidone and Alprazolam in Pharmaceutical Products

A simple, sensitive, and precise thin layer chromatographic (TLC) method for simultaneous analysis of psychopharmacological drugs like amitriptyline HCl, trifluoperazine HCl, risperidone and alprazolam in their single dosage forms has been developed, validated, and used for determination of the compounds in commercial pharmaceutical products. The TLC separation was carried out on Merck TLC aluminium sheets of silica gel 60 F254 using carbon tetrachloride:acetone:triethylamine (8:2:0.3, v/v/v), as mobile phase. Densitometric measurements of their spots were achieved at 250 nm over the concentration range for amitriptyline HCl (50–1,200 ng spot⁻¹), trifluoperazine HCl (50–1,200 ng spot⁻¹), risperidone (100–2,400 ng spot⁻¹) and alprazolam (25–600 ng spot⁻¹). Limit of detection (LOD) for amitriptyline HCl (20 ng spot⁻¹), trifluoperazine HCl (20 ng spot⁻¹), risperidone (40 ng spot⁻¹) and alprazolam (5 ng spot⁻¹) was obtained. The study showed that TLC was sensitive and selective for determination of amitriptyline HCl, trifluoperazine HCl, risperidone and alprazolam using a single mobile phase. This proposed method is able for simultaneous determination of psychopharmacological drugs and also applicable for analysis of pharmaceutical formulations.

     

Hybrid Nanocomposite Based Graphene Sensor for Ultrasensitive Clomipramine HCl Detection

A potentiometric sensor modified with a nanocomposite of montmorillonite sheets decorated with polyaniline nanofibers (MT-PANI-NFs) as an efficient electroactive material and tricresyl phosphate (TCP) as a solvent mediator has been developed for the estimation of clomipramine HCl (CLP.HCl). The optimum potentiometric performance of the sensor was achieved by mixing of MT-PANI-NFs : TCP : graphene with a ratio of 2.69 : 30.11 : 67.20 (% wt/wt). The sensor exhibited a Nernstian slope of 59.0±0.1 mV decade⁻¹ over the concentration range of 1.0×10⁻⁵−1.0×10⁻² mol L⁻¹ with a theoretically calculated detection limit of 5.0×10⁻⁶ mol L⁻¹. The sensor performance was scrutinized in terms of several factors including thermal stability, pH effect, response time and selectivity. As, it displayed a high thermal stability at various temperature degrees (10–60 °C) with pH independency in the range of 3.5–8.5. Additionally, the developed sensor exhibited a very rapid performance for CLP.HCl detection with a fast response time of 4 s and reflecting a superior selectivity towards CLP.HCl over the other interfering species. SEM (scanning electron microscope) was used as a characteristic tool for the investigation of the proposed graphene sensor surface. Furthermore, the graphene sensor has been efficiently used for CLP.HCl estimation in its pharmaceutical formulations.     

Simultaneous Determination of Cephalexin and Carbocisteine from Capsules by Reverse Phase High Performance Liquid Chromatography (RP - HPLC).

Abstract

A new, simple, precise, accurate and rapid RP- HPLC method has been developed for the simultaneous determination of Cephalexin and Carbocisteine from capsules, using 0.025 M monobasic sodium phosphate: acetonitrile (87:13, v/v) as a mobile phase, and a C₈ Shodex column as the stationary phase. Detection was carried out using a UV detector at 210 nm. The linearity range for Cephalexin and Carbocisteine were 50 - 300 μg/mL and 40 - 200 μg/mL, respectively. Assay values for Cephalexin and Carbocisteine were 99.46% (R.S.D. - 1.30%) and 99.22% (R.S.D.-1.34%) for Brand 1. and 99.71% (R.S.D. - 1.68%) and 99.43% (R.S.D. - 1.78%) for Brand 2, respectively.     

Separation of catechins and methylxanthines in tea samples by capillary electrochromatography

In this paper, the simultaneous separation of several polyphenols such as (+)‐catechin, (–)‐epicatechin, (–)‐epigallocatechin, theophylline, caffeine in green and black teas by capillary electrochromatography (CEC) was developed. Several experimental parameters such as stationary phase type, mobile phase composition, buffer and pH, inner diameter of the columns, sample injection, were evaluated to obtain the complete separation of the analysed compounds. Baseline resolution of the studied polyphenols was achieved within 30 min by using a capillary column (id 100 μm) packed with bidentate C₁₈ particles for 24.5 cm and a mobile phase composed of 5 mM ammonium acetate buffer pH 4 with H₂O/ACN (80:20, v/v). The applied voltage and the temperature were set at 30 kV and 20°C. Precision, detection and quantification limits, linearity, and accuracy were investigated. A good linearity (R² > 0.9992) was achieved over a concentration working range of 2–100 μg/mL for all the analytes. LOD and LOQ were 1 and 2 μg/mL, respectively, for all studied compounds. The CEC method was applied to the analysis of those polyphenols in green and black tea samples after an extraction procedure. Good recovery data from accuracy studies ranged between 90% and 112% for all analytes.     

Validated LC Method, with a Chiral Mobile Phase, for Separation of the Isomers of Fexofenadine Hydrochloride

A rapid, simple and sensitive high-performance liquid chromatographic method (HPLC) has been developed to assay atomoxetine HCl in capsules. The HPLC analysis used a reversed phase C18 (150 × 4.6 mm i.d. 5 μm particle size) analytical column and a mobile phase consisting of monobasic potassium dihydrogen orthophosphate and acetonitrile (95:5 v/v), with UV detection at 269 nm. The validation data showed that the assay is sensitive, specific and reproducible for determination of atomoxetine HCl in this dosage form. Calibration curves were linear from 1 to 10 μg mL⁻¹ (R ² > 0.997). The accuracy of the method ranged from 98.13 to 101.5%. Mean inter- and intra-assay relative standard deviations (RSD) were less than 1.0%. The proposed method provided an accurate and precise analysis of atomoxetine HCl in its pharmaceutical dosage form.     

Leaching of Triazine Pesticides in Loamy Soil and their Determination by Reversed Phase HPLC

Abstract

The separation and identification of triazine pesticides (ametryn, atrazine, cyanazine and simazine) was carried out on Nova Pak C₁₈ column (150 × 3.9mm). The mobile phase used was acetonitrile-water (65:35, v/v) adjusted to pH 4.5 with acetic acid. The flow rate of the mobile phase used was 1.0mL/min. The detection of the pesticides was carried out at 250 nm. The values of the separation factor (α) were in the range of 1.49–5.32 and the values of the resolution factors (R _s) were ranged from 1.18 to 2.99 for the separated pesticides. The developed HPLC method was used to determine the concentrations of the reported pesticides in the loamy soil samples. The recovery of the pesticides from soil samples was found to be about 50%. The relative standard deviation and limit of detection were in the range of 0.01–0.02 and 0.5–1.0 μg/mL respectively.     

Application of a Validated, Stability-Indicating LC Method to Stress Degradation Studies of Ramipril and Moexipril.HCl

A stability-indicating reversed-phase liquid chromatographic (RPLC) method has been established for analysis of ramipril (RAM) and moexipril hydrochloride (MOEX.HCl) in the presence of the degradation products generated in studies of forced decomposition. The drug substances were subjected to stress by hydrolysis (0.1 m NaOH and 0.1 m HCl), oxidation (30% H₂O₂), photolysis (254 nm), and thermal treatment (80 °C). The drugs were degraded under basic and acidic conditions and by thermal treatment but were stable under other stress conditions investigated. Successful separation of the drugs from the degradation products was achieved on a cyanopropyl column with 40:60 (v/v) aqueous 0.01 m ammonium acetate buffer (pH 6)–methanol as mobile phase at a flow rate of 1 mL min⁻¹. Detection was by UV absorption at 210 nm. Response was a linear function of concentration over the range 5–50 μg mL⁻¹ (r > 0.9995), with limits of detection and quantitation (LOD and LOQ) of 0.04 and 0.09 μg mL⁻¹, respectively, for RAM and 0.014 and 0.32 μg mL⁻¹, respectively, for moexipril. The method was validated for specificity, selectivity, solution stability, accuracy, and precision. Statistical analysis proved the method enabled reproducible and selective quantification of RAM and MOEX as the bulk drug and in pharmaceutical preparations. Because the method effectively separates the drugs from their degradation products, it can be used as stability-indicating.     

Simultaneous Determination of Phenylpropanolamine Hydrochloride and Isopropamide in Capsule∗ by High Performance Liquid Chromatography Using CROWNPAK Column

Abstract

A procedure is described for the assay of phenylpropanolamine hydrochloride & isopropamide by HPLC using CROWNPAK column and detection at 200 nm. The system was aqueous perchloric acid as mobile phase containing 5 % methanol. Linearity studies were carried out using peak height measurements. There was > 99 % recovery and coefficient of variation was < 2% for formulation. The procedure was rapid, accurate, precise and specific for the assay of phenylpropanolamine HCl in presence of isopropamide.     

Spectrophotometric Determination of Certain Local Anaesthetics in Pharmaceutical Preparations

Abstract

A direct colorimetric method was described for the rapid, sensitive and accurate determination of dibucaine, lidocaine, bupivacaine, procaine and tetracaine in pharmaceutical preparations. The method involves the use of haematoxylin reagent in the presence of boric acid to give a reddish-violet chromogen (λ_max = 555 nm). Beer's law was obeyed in the range from 2–60 μg/ml. No interference was observed from the commonly present additives or agents in pharmaceutical formulations.     

Determination of Cefpodoxime Levels and Cefpodoxime Stability In Human Urine By Direct Injection HPLC with Column-Switching

Abstract

A semi-automated method providing on-line sample extraction and quantitative analysis for cefpodoxime in human urine, injected directly into the HPLC, is reported.

Samples were filtered by the analyst, injected into the HPLC system with an autosampler and loaded onto a 3 cm RP-18 precolumn with a mobile phase consisting of 10% methanol in 0.2% phosphoric acid and then automatically eluted onto a RP-18 analytical column using a mobile phase containing 7% acetonitrile in pH 5.2 sodium acetate buffer. the mean between-day precision of the standards was ± 4.29%. Spiked urine control recovery averaged 96 ± 6% for controls ranging from 1.0 to 20.0 μg/mL. the limit of quantitation for the method was 0.11 μg/mL.