Preparation of a multi-hapten antigen and broad specificity polyclonal antibodies for a multiple pesticide immunoassay

A multi-determinant artificial antigen was prepared by haptens of four pesticides (chlorpyrifos, triazophos, carbofuran and parathion methyl) conjugating to the carrier protein BSA in turn. Male New Zealand white rabbits were immunized with this multi-determinant immunogen to produce the polyclonal antibodies (PAbs), which can recognize the four pesticides. The PAbs displayed high level for each relative hapten-OVA conjugate, with the favorable titers of 4.49 × 10⁴, 8.98 × 10⁴, 2.24 × 10⁴ and 1.86 × 10⁴, for CHBu-OVA, THHe-OVA, BFNB-OVA and MP5-OVA, respectively. Characterization studies of the PcAbs showed that it has high affinity and specificity to the four relative pesticides. An indirect competitive ELISA was developed for multi-residue determination. The I₅₀ value for the four pesticides was 0.290, 0.065, 0.582 and 2.824 μg mL⁻¹, with the detection limit (I₁₀) of 0.022, 0.005, 0.015 and 0.115 μg mL⁻¹ for carbofuran, triazophos, chlorpyrifos and parathion methyl, respectively. The linear rang was 0.016-2.000, 0.005-0.500, 0.010-2.000 and 0.063-5.000 μg mL⁻¹, respectively, for carbofuran, triazophos, chlorpyrifos and parathion methyl. Results indicated that, this study provided a new strategy to develop immunoassays through artificial antigen design for pesticides multi-residue determination.     

A reversed-phase high performance liquid chromatography coupled with resonance Rayleigh scattering detection for the determination of four tetracycline antibiotics

A new reversed-phase high performance liquid chromatography with resonance Rayleigh scattering detection (HPLC-RRS) was developed for simultaneous separation and determination of four tetracycline antibiotics (TCs). A good chromatographic separation among the compounds was achieved using a Synergi Fusion-RP column (150 mm × 4.6 mm; 4 μm) and a mobile phase consisting of methanol-acetonitrile-oxalic acid (5 mM) at the flow rate of 0.8 mL min⁻¹. Column temperature was 30 °C. The RRS signal was detected at λ_ex = λ_em = 370 nm. The recoveries of sample added standard ranged from 95.3% to 103.5%, and the relative standard deviation was below 2.79%. A detection limit of 2.12-5.12 μg mL⁻¹ was reached and a linear range was found between peak height and concentration in the range of 10.36-518.0 μg mL⁻¹ for oxytetracycline (OTC), 12.11-605.5 μg mL⁻¹ for tetracycline (TC), 11.79-589.5 μg mL⁻¹ for chlortetracycline (CTC) and 10.32-516.0 μg mL⁻¹ for doxycycline (DC). The linear regression coefficients were all above 0.999. The method has been applied successfully to the determination of OTC, TC, CTC, DC in pharmaceutical formulations and in honey. The method was simple, rapid and showed a better linear relation and high repeatability.     

Determination of indole-3-acetic acid and indole-3-butyric acid in mung bean sprouts using high performance liquid chromatography with immobilized Ru(bpy)3-KMnO4 chemiluminescence detection

A novel method for determination of indole-3-acetic acid (IAA) and indole-3-butyric acid (IBA) in an extract from mung bean sprouts using high performance liquid chromatography (HPLC) with chemiluminescence (CL) detection is described. The method is based on the CL reaction of auxin (indole-3-acetic acid and indole-3-butyric acid) with acidic potassium permanganate (KMnO₄) and tris(2,2′-bipyridyl)ruthenium(II), which was immobilized on the cationic ion-exchange resin. The chromatographic separation was performed on a Nucleosil RP-C18 column (i.d.: 250 mm × 4.6 mm, particle size: 5 μm, pore size: 100) with an isocratic mobile phase consisting of methanol-water-acetic acid (45:55:1, v/v/v). At a flow rate of 1.0 mL min⁻¹, the total run time was 20 min. Under the optimal conditions, the linear ranges were 5.0 × 10⁻⁸ to 5.0 × 10⁻⁶ g mL⁻¹ and 5.0 × 10⁻⁷ to 1.0 × 10⁻⁵ g mL⁻¹ for IAA and IBA, respectively. The detection limits were 2.0 × 10⁻⁸ g mL⁻¹ and 2.0 × 10⁻⁷ g mL⁻¹ for IAA and IBA, respectively. The relative standard deviation (RSD) of intra-day were 3.1% and 2.3% (n = 11) for 2 × 10⁻⁶ g mL⁻¹ IAA and 2 × 10⁻⁶ g mL⁻¹ IBA; The relative standard deviations of inter-day precision were 6.9% and 4.9% for 2 × 10⁻⁶ g mL⁻¹ IAA and 2 × 10⁻⁶ g mL⁻¹ IBA. The proposed method had been successfully applied to the determination of auxin in mung bean sprouts.     

Determination of beta-lactam antibiotics in milk using micro-flow chemiluminescence system with on-line solid phase extraction

In this paper, a chemiluminescence (CL) micro-flow system combined with on-line solid phase extraction (SPE) is presented for determination of β-lactam antibiotics (penicillin, cefradine, cefadroxil, cefalexin) in milk. It is based on the enhancement effect of β-lactam antibiotics on the luminol-K₃Fe(CN)₆ CL system. The micro-flow system was fabricated from two polymethyl methacrylate (PMMA) plates (50 mm × 40 mm × 5 mm) with the microchannels of 200 μm wide and 150 μm deep. C₁₈-modified silica gel was packed into the microchannel (length: 10 mm; width: 1 mm; depth: 500 μm) to serve as SPE device. Extraction and preconcentration of the analytes were carried out using on-line SPE micro-flow system and the selectivity of CL detection was improved. The detection limits were 0.5 μg mL⁻¹ of penicillin, 0.04 μg mL⁻¹ of cefradine, 0.08 μg mL⁻¹ of cefadroxil and 0.1 μg mL⁻¹ of cefalexin. The proposed method was also applied to analyze the β-lactam antibiotics in milk. Experimental results were in good agreement with those obtained by high performance liquid chromatography (HPLC) method with UV detection.     

Simultaneous determination of salbutamol sulphate, bromhexine hydrochloride and etofylline in pharmaceutical formulations with the use of four rapid derivative spectrophotometric methods

Four simple, rapid, accurate, precise, reliable and economical spectrophotometric methods have been proposed for simultaneous determination of salbutamol sulphate (SS), bromhexine hydrochloride (BH) and etofylline (ET) in pure and commercial formulations without any prior separation or purification. They were first derivative zero crossing spectrophotometry (method 1), simultaneous equation method (method 2), derivative ratio spectra zero crossing method (method 3) and double divisor ratio spectra derivative method (method 4). The ranges for SS, BH and ET were found to be 1-35 μg mL⁻¹, 4-40 μg mL⁻¹ and 5-80 μg mL⁻¹. For methods 1 and 2, the values of limit of detection (LOD) were 0.2314 μg mL⁻¹, 0.4865 μg mL⁻¹ and 0.2766 μg mL⁻¹ and the values of limit of quantitation (LOQ) were 0.7712 μg mL⁻¹, 1.6217 μg mL⁻¹ and 0.9221 μg mL⁻¹ for SS, BH and ET, respectively. For method 3, LOD values were 0.3297 μg mL⁻¹, 0.2784 μg mL⁻¹ and 0.7906 μg mL⁻¹ and LOQ values were 0.9325 μg mL⁻¹, 0.9282 μg mL⁻¹ and 2.6352 μg mL⁻¹ for SS, BH and ET, respectively. For method 4, LOD values were 0.3161 μg mL⁻¹, 0.2495 μg mL⁻¹ and 0.2064 μg mL⁻¹ and LOQ values were 0.9869 μg mL⁻¹, 0.8317 μg mL⁻¹ and 0.6879 μg mL⁻¹ for SS, BH and ET. The precision values were less then 2% R.S.D. for all four methods. The common excipients and additives did not interfere in their determinations. The results obtained by the proposed methods have been statistically compared by means of Student t-test and by the variance ratio F-test.     

Validation of HPLC stability-indicating method for Vitamin C in semisolid pharmaceutical/cosmetic preparations with glutathione and sodium metabisulfite, as antioxidants

HPLC stability-indicating method was validated for Vitamin C (ascorbic acid) in semisolid pharmaceutical/cosmetic formulations containing glutathione and sodium metabisulfite, as antioxidants. The described procedure included a reliable, precise, accurate and specific method determination employing a 250 mm × 4.6 mm C₁₈ column, 0.2% metaphosphoric acid/methanol/acetonitrile (90:8:2, v/v/v) as the mobile phase and detection at 254 nm. Nicotinic and ascorbic acids were employed as standards, both presenting purity of 99.0%. Linearity was established for the ascorbic acid concentrations ranging form 1.0 to 12 μg mL⁻¹, accuracy/recovery percentage was 95.46-101.54%, precision values were 0.38 (intra-day) and 1.22% (inter-days), and LOD and LOQ were found to be 0.05 and 0.17 μg mL⁻¹, respectively. The working mobile phase elevated the ascorbic acid retention time to ≈3.5 min at a flow rate of 1.0 mL min⁻¹ and provided resolution of the active from the nicotinic acid (internal standard), degradation product (oxalic acid) and other excipients from the pharmaceutical/cosmetic preparations.     

Determination of pKa values of some antihypertensive drugs by liquid chromatography and simultaneous assay of lercanidipine and enalapril in their binary mixtures

In this study, pK_a values were determined using the dependence of the retention factor on the pH of the mobile phase for three ionizable substances, namely, enalapril, lercanidipine and ramipril (IS). The effect of the mobile phase composition on the ionization constant was studied by measuring the pK_a at different methanol-water mixtures, ranging between 50 and 65% (v/v), using LC-DAD method. Two simple, accurate, precise and fully validated analytical methods for the simultaneous determination of enalapril and lercanidipine in combined dosage forms have been developed. Separation was performed on an X-Terra RP-18 column (250 mm × 4.60 mm ID × 5 μm) at 40 °C with the mobile phase of methanol-water 55:45 (v/v) adjusted to pH 2.7 with 15 mM orthophosphoric acid. Isocratic elution was performed in less than 12 min with a flow rate of 1.2 mL min⁻¹. Good sensitivity for the analytes was observed with DAD detection. The LC method allowed quantitation over the 0.50-20.00 μg mL⁻¹ range for enalapril and lercanidipine. The second method depends on first derivative of the ratio-spectra by measurements of the amplitudes at 219.7 nm for enalapril and 233.0 nm for lercanidipine. Calibration graphs were established for 1-20 μg mL⁻¹ for enalapril and 1-16 μg mL⁻¹ lercanidipine, using first derivative of the ratio spectrophotometric method. Both methods have been extensively validated. These methods allow a number of cost and time saving benefits. The described methods can be readily utilized for analysis of pharmaceutical formulations. The methods have been applied, without any interference from excipients, for the simultaneous determination of these compounds in tablets. There was no significant difference between the performance of the proposed methods regarding the mean values and standard deviations.     

Fluorescence enhancement of CdTe/CdS quantum dots by coupling of glyphosate and its application for sensitive detection of copper ion

A novel fluorescent probe for Cu²⁺ determination based on the fluorescence quenching of glyphosate (Glyp)-functionalized quantum dots (QDs) was firstly reported. Glyp had been used to modify the surface of QDs to form Glyp-functionalized QDs following the capping of thioglycolic acid on the core–shell CdTe/CdS QDs. Under the optimal conditions, the response was linearly proportional to the concentration of Cu²⁺ between 2.4 × 10⁻² μg mL⁻¹ and 28 μg mL⁻¹, with a detection limit of 1.3 × 10⁻³ μg mL⁻¹ (3δ). The Glyp-functionalized QDs fluorescent probe offers good sensitivity and selectivity for detecting Cu²⁺. The fluorescent probe was successfully used for the determination of Cu²⁺ in environmental samples. The mechanism of reaction was also discussed.     

Simultaneous cloud point extraction and spectrophotometric determination of carmoisine and brilliant blue FCF in food samples

A novel simultaneous cloud point extraction method for the determination of carmoisine and brilliant blue FCF by spectrophotometry has been developed. The method is based on the cloud point extraction of carmoisine and brilliant blue FCF from aqueous solution using Triton X-100, diluting the extracted surfactant rich phase with water and measuring the absorbance at 522 and 640 nm for carmoisine and brilliant blue FCF, respectively. The effects of different parameters such as pH, concentration of surfactant and temperature on the cloud point extraction of both dyes were investigated and optimum conditions were established. Linear calibration curves were obtained in the range of 0.02-3.50 μg mL⁻¹ for carmoisine and 0.05-3.50 μg mL⁻¹ for brilliant blue FCF under optimum conditions. Detection limit based on three times the standard deviation of the blank (3S_b) was 0.017 and 0.016 μg mL⁻¹ (n = 10) for carmoisine and brilliant blue FCF, respectively. The relative standard deviation (RSD) for 0.1 μg mL⁻¹ was 4.14 and 3.30% (n = 10), for carmoisine and brilliant blue FCF, respectively. The method was applied to the simultaneous determination of the dyes in different food samples.     

Liquid chromatographic determination of sitagliptin either alone or in ternary mixture with metformin and sitagliptin degradation product

Two reversed-phase liquid chromatographic (RP-LC) methods have been developed for the determination of sitagliptin phosphate monohydrate (STG). The first method comprised the determination of STG alone in bulk and plasma; and in its pharmaceutical preparation. This method was based on isocratic elution of STG using a mobile phase consisting of potassium dihydrogen phosphate buffer pH (7.8)-acetonitrile (70:30, v/v) at a flow rate of 1 mL min⁻¹ with flourometric detection. The flourometric detector was operated at 267 nm for excitation and 575 nm for emission. In the second method, the simultaneous determination of STG and metformin (MET) in the presence of sitagliptin alkaline degradation product (SDP) has been developed. In this method, the ternary mixture of STG, MET and SDP was separated using a mobile phase consisting of potassium dihydrogen phosphate buffer pH (4.6)-acetonitrile-methanol (30:50:20, v/v/v) at a flow rate of 1 mL min⁻¹ with UV detection at 220 nm. Chromatographic separation in the two methods was achieved on a Symmetry^® Waters C18 column (150 mm × 4.6 mm, 5 μm). Linearity, accuracy and precision were found to be acceptable over the concentration ranges of 0.25-200 μg mL⁻¹ for STG with the first method and 5-160 μg mL⁻¹, 25-800 μg mL⁻¹ for STG and MET, respectively with the second method. The optimized methods were validated and proved to be specific, robust and accurate for the quality control of the cited drugs in pharmaceutical preparations.     

Determination of nateglinide in human plasma by high-performance liquid chromatography with pre-column derivatization using a coumarin-type fluorescent reagent

A sensitive and selective high-performance liquid chromatographic method has been developed and validated for the determination of nateglinide in human plasma. Nateglinide and the internal standard, undecylenic acid, were extracted from plasma by liquid-liquid extraction using a mixture of ethyl acetate-diethyl ether, 50:50 (v/v). Pre-column derivatization reaction was performed using a coumarin-type fluorescent reagent, N-(7-methoxy-4-methyl-2-oxo-2H-6-chromenyl)-2-bromoacetamide. The derivatization proceeded in acetone in the presence of potassium carbonate and catalyzed by 18-crown-6 ether. The fluorescent derivatives were separated under isocratic conditions on a Hypersil BDS-C8 analytical column (250.0 mm × 2.1 mm i.d., particle size 5 μm) with a mobile phase that consisted of 65% acetonitrile in water and pumped at a flow rate of 0.50 mL min⁻¹. The excitation and emission wavelengths were set at 345 and 435 nm, respectively. The assay was linear over a concentration range of 0.05-16.00 μg mL⁻¹ for nateglinide with a limit of quantitation of 0.05 μg mL⁻¹. Quality control samples (0.05, 4.50 and 16.00 μg mL⁻¹) in five replicates from five different runs of analysis demonstrated intra-assay precision (%coefficient of variation <6.8%), inter-assay precision (%coefficient of variation <1.6%) and an overall accuracy (%relative error) less than −3.4%. The method can be used to quantify nateglinide in human plasma covering a variety of pharmacokinetic or bioequivalence studies.     

A novel application of immobilization on membranes for the separation and spectrofluorimetric quantification of amiloride and furosemide in pharmaceutical samples

A new, simple and highly sensitive method for spectrofluorimetric determination of amiloride (AMI) and furosemide (FUR) in pharmaceuticals is presented. The proposed method is based on the separation of AMI from FUR by solid-phase extraction using a nylon membrane, followed by spectrofluorimetric determination of both drugs, on the solid surface and the filtered aqueous solution, respectively. AMI shows low native fluorescence, but its separation-preconcentration by immobilization (solid-phase extraction) on nylon membrane surface provides a considerable enhancement in fluorescence intensity. The fluorescence determination is carried out at λ_ex = 237, λ_em = 415 nm for FUR; and λ_ex = 365, λ_em = 406 nm for AMI. The calibration graphs are linear in the range 3.20 × 10⁻⁴ to 0.8 μg mL⁻¹and 1.33 × 10⁻³ to 4.0 μg mL⁻¹, for AMI and FUR, respectively, with a detection limit of 9.62 × 10⁻⁵ and 4.01 × 10⁻⁴ μg mL⁻¹ (S/N = 3). The commonly found excipients in commercial pharmaceutical formulations do not interfere. The developed method is successfully applied to the determination of both drugs in pharmaceutical formulations.     

Ligandless dispersive liquid-liquid microextraction for the separation of trace amounts of silver ions in water samples and flame atomic absorption spectrometry determination

In this article, a new ligandless dispersive liquid-liquid microextraction method has been developed for preconcentration of trace quantities of silver as a prior step to its determination by flame atomic absorption spectrometry. In the proposed approach, carbon tetrachloride and ethanol were used as extraction and dispersive solvents. Several factors that may be affected on the extraction process, like, extraction solvent, disperser solvent, the volume of extraction and disperser solvent, pH of the aqueous solution and extraction time were optimized. Under the optimal conditions, the calibration curve was linear in the range of 5.0 ng mL⁻¹ to 2.0 μg mL⁻¹ of silver with R² = 0.9995 (n = 9) and detection limit based on three times the standard deviation of the blank (3S_b) was 1.2 ng mL⁻¹ in original solution. The relative standard deviation for eight replicate determination of 0.5 μg mL⁻¹ silver was ±1.5%. The high efficiency of dispersive liquid-liquid microextraction to carry out the determination of silver in complex matrices was demonstrated. The proposed method has been applied for determination of trace amount of silver in standard and water samples with satisfactory results.     

A rapid, acetonitrile-free, HPLC method for determination of melamine in infant formula

A simple, precise, accurate and validated, acetonitrile-free, reverse phase high performance liquid chromatography (HPLC) method is developed for the determination of melamine in dry and liquid infant formula. The separation is performed on a Kromasil C18 column (150 mm × 3.2 mm I.D., 5 μm particle size) at room temperature. The mobile phase (0.1% TFA/methanol 90:10) is pumped at a flow rate of 0.3 mL min⁻¹ with detection at 240 nm. Melamine elutes at 3.7 min. A linear response (r > 0.999) is observed for samples ranging from 1.0 to 80 μg mL⁻¹. The method provides recoveries of 97.2-101.2% in the concentration range of 5-40 μg mL⁻¹, intra- and inter-day variation in <1.0% R.S.D. The limit of detection (LOD) and limit of quantification (LOQ) values are 0.1 μg mL⁻¹ and 0.2 μg mL⁻¹, respectively.     

Determination of thiomersal by flow injection coupled with microwave-assisted photochemical online oxidative decomposition of organic mercury and cold vapor atomic fluorescence spectroscopy

We developed a flow injection (FI) method for the determination of thiomersal (sodium ethylmercurithiosalicylate, C₉H₉HgNaO₂S) based on the UV/microwave (MW) photochemical, online oxidation of organic mercury, followed by cold vapor generation atomic fluorescence spectrometry (CVG-AFS) detection. Thiomersal was quantitatively converted in the MW/UV process to Hg(II), with a yield of 97 ± 3%. This reaction was followed by the reduction of Hg(II) to Hg(0) performed in a knotted reaction coil with NaBH₄ solution, and AFS detection in an Ar/H₂ miniaturized flame. The method was linear in the 0.01–2 μg mL⁻¹ range, with a LOD of 0.003 μg mL⁻¹. This method has been applied to the determination of thiomersal in ophthalmic solutions, with recoveries ranging between 97% and 101%. We found a mercury concentration in commercial ophthalmic solutions ranging between 7.5 and 59.0 μg mL⁻¹.     

Flow injection chemiluminescence determination of nitrofurazone in pharmaceutical preparations and biological fluids based on oxidation by singlet oxygen generated in N-bromosuccinimide-hydrogen peroxide reaction

A simple flow injection chemiluminescence (FI-CL) method was proposed for the determination of nitrofurazone. Strong CL signal was generated during the reaction of nitrofurazone with H₂O₂ and N-bromosuccinimide (NBS) in alkaline condition. The CL signal was proportional to the nitrofurazone concentration in the range 1.0 × 10⁻⁷ to 1.0 × 10⁻⁵ g mL⁻¹. The detection limit was 2 × 10⁻⁸ g mL⁻¹ nitrofurazone and the relative standard deviation was less than 4% (6.0 × 10⁻⁶ g mL⁻¹ nitrofurazone, n = 11). The proposed method was successfully applied to the determination of nitrofurazone in compound furacillin nasal drops, human plasma and urine samples. The CL reaction mechanism was also discussed briefly. Singlet oxygen generated in the reaction between H₂O₂ and NBS was suggested to be participated in the CL reaction.     

Ligandless-dispersive liquid-liquid microextraction of trace amount of copper ions

In the present work, a new ligandless-dispersive liquid-liquid microextraction (LL-DLLME) method has been developed for preconcentration trace amounts of copper as a prior step to its determination by flame atomic absorption spectrometry. In the proposed approach 1,2-dicholorobenzene and ethanol were used as extraction and dispersive solvents, respectively. Some factors influencing on the extraction efficiency of copper and its subsequent determination were studied and optimized, such as the extraction and dispersive solvent type and volume, pH of sample solution, extraction time and salting out effect. Under the optimal conditions, the calibration curve was linear in the range of 1.0 ng mL⁻¹-0.6 μg mL⁻¹ of copper with R² = 0.9985. Detection limit was 0.5 ng mL⁻¹ in original solution (3S_b/m) and the relative standard deviation for seven replicate determination of 0.2 μg mL⁻¹ copper was ±1.4%. The proposed method has been applied for determination of copper in standard and water samples with satisfactory results.     

Optimization and comparison of chemical and electrochemical hydride generation for optical emission spectrometric determination of arsenic and antimony using a novel miniaturized microwave induced argon plasma exiting the microstrip wafer

Continuous flow (CF) chemical hydride generation (CHG) and electrochemical hydride generation (ECHG) directly coupled to a novel 40 W, atmospheric pressure, 2.45 GHz microwave microstrip Ar plasma exiting a microstrip wafer has been developed for the emission spectrometric determination of As and Sb using a miniaturized optical fiber spectrometer and a CCD-array detector. The experimental conditions for both procedures were optimized with respect to the relative net intensities of the As I 228.8 nm and Sb I 252.8 nm lines and their signal-to-background intensity ratios. Additionally, the susceptibility to interferences from Cd, Co, Cr, Cu, Fe, Ni, Pb and Zn and other hydride-forming elements in the determination of As and Sb using the CHG and ECHG techniques was investigated in detail. Under the optimized conditions, it was found that ECHG is more prone to interferences compared to CHG. The detection limits (3σ) of As (6 ng mL⁻¹) and Sb (7 ng mL⁻¹) obtained for the ECHG-MSP-OES method are about three times lower than in the case of the CHG-MSP-OES method due to a two-fold lower amount of H₂ introduced into the MSP in case of the ECHG, resulting in a better plasma stability and reduced background level. The linearity ranges for both calibration curves to a concentration of up to 5 μg mL⁻¹ and a precision between 2% and 7% (2 μg mL⁻¹ and 0.050 μg mL⁻¹ of As and Sb, respectively) were found for both methods. The developed ECHG-MSP-OES method was validated for As through the analysis of a certified coal fly ash standard reference material (NIST SRM 1633a) after sample dissolution. The derived concentration (140 ± 8 μg g⁻¹) was found to agree well with the certified data (145 ± 15 μg g⁻¹). The method was also successfully applied to the analysis of both a galvanic bath sample, which contained Sb and was spiked with As, and a tap water sample spiked with both analytes. Recovery rates of 99-101% and a Sb concentration of 6.6 μg mL⁻¹ in the galvanic bath sample were revealed. The latter value showed a good agreement with the data obtained from ICP-OES analysis, which was also used for validation purpose.     

Simultaneous chemiluminescence determination of promazine and fluphenazine using support vector regression

In this work, chemiluminescence (CL) behaviors of two selected phenothiazines, namely promazine and fluphenazine hydrochloride, were investigated for their simultaneous determination using oxidation of Ru(bipy)₃²⁺ by Ce⁴⁺ ions in acidic media. This method is based on the kinetic distinction of the CL reactions of fluphenazine and promazine with Ru(bipy)₃²⁺ and Ce⁴⁺ system in a sulfuric acid medium. Least square support vector regression models were constructed for relating concentrations of both compounds to their CL profiles. The parameters of the model consisting of σ² and γ were optimized using all possible combinations of σ² and γ to select the model with the minimum root mean square cross validation. Under optimized conditions, the univariate calibration curve was linear over the concentration ranges of 0.4-30.0 μg mL⁻¹ and 0.07-5.0 μg mL⁻¹ with detection limits of 0.1 μg mL⁻¹ and 0.04 μg mL⁻¹ for promazine and fluphenazine, respectively. The influence of potential interfering substances on the determination of promazine and fluphenazine were studied. The proposed method was used for simultaneous determination of both compounds in synthetic mixtures and in spiked human plasma.     

Determination of lead by hydride generation inductively coupled plasma mass spectrometry (HG-ICP-MS): On-line generation of plumbane using potassium hexacyanomanganate(III)

A hydride generation (HG) procedure has been described for determination of Pb by ICP-MS using potassium hexacyanomanganate(III), K₃Mn(CN)₆, as an additive to facilitate the generation of plumbane (PbH₄). Potassium hexacyanomanganate(III) was prepared in acidic medium as it was unstable in water. The stability of hexacyanomanganate(III) was examined in dilute solutions of HCl, HNO₃ and H₂SO₄. The solutions prepared in 1% v/v H₂SO₄ were found to be stable for over a period of 24 h. The least suitable medium was 1% v/v HNO₃. For generation of plumbane, acidic hexacyanomanganate(III) and sample solutions were mixed on-line along a 5-cm long tygon tubing (1.14 mm i.d.) and then reacted with 2% m/v sodium borohydride (NaBH₄). A concentration of 0.5% m/v K₃Mn(CN)₆ facilitated the generation of PbH₄ remarkably. In comparison to H₂SO₄, HCl provided broader working range for which optimum concentration was 1% v/v. No significant interferences were noted from transition metals and hydride forming elements, up to 0.5 μg mL⁻¹ levels, except Cu which depressed the signals severely. The depressive effects in the presence of 0.1 μg mL⁻¹ Cu were alleviated by increasing the concentration of K₃Mn(CN)₆ to 2% m/v. Under these conditions, the sensitivity was enhanced by a factor of at least 42 to 48. The detection limit (3 s) was 0.008 μg L⁻¹ for ²⁰⁸Pb isotope. Average signal-to-noise ratio (S/N) ranged between 18 and 20 for 1.0 μg mL⁻¹ Pb solution. The accuracy of the method was verified by analysis of several certified reference materials, including Nearshore seawater (CASS-4), Bone ash (SRM 1400), and Mussel tissue (SRM 2976). The procedure was also successfully applied to the determination of Pb in coastal seawater samples by ICP-MS.