Chemiluminescent (CL) detection techniques for DNA assays and immunoassays have become very popular in recent years. This review discusses recent advances in those CL assays that have occurred over the last few years. In the monoplex assay section, different classes of CL labels including nanoparticle, DNAzyme, acridinium ester, enzyme and luminol-based CL assays are reviewed concerning the detection of DNAs and proteins. In the multiplex assay section, both spatial resolution and substrate zone-resolved techniques are discussed.

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A supersonic jet/resonance-enhanced multiphoton ionization/time-of-flight mass spectrum (SSJ/REMPI/TOF-MS) was measured for xylenols and ethylphenols. Sharp and intense peaks were observed in the REMPI spectrum of 2,4-xylenol, and the wavelength of the peak tentatively assigned to the 0-0 transition was the longest among xylenols and ethylphenols. These results suggest that 2,4-xylenol, designated as a Class II chemical substance in the Pollutant Release and Transfer Register (PRTR), can be measured sensitively and selectively even when numerous isomers are present in the sample.

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A simple and precise size measurement device of microparticles in liquid has been developed by using a narrow gap between a cylindrical lens and a flat glass wall, in which the distance of the gap is precisely determined by the diffraction Moiré pattern of irradiated light. Two different methods to transfer the particles toward the center line of the lens, a hydrodynamic flow mode and an electrophoretic mode, have been established. By using these methods, simultaneous size-determination and size-separation of small amounts of micrometer and sub-micrometer sized polystyrene particles in water have been attained with high precision. Novel advantages of the cylindrical nano-gap method were demonstrated for different surface types of polystyrene particles.

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The possibility of thermal lensing of dynamically emerging light-absorbing layers at cell surfaces was investigated. Analyte accumulation at a cell surface determines long-term changes in the thermal-lens signal that was used as a source of analytical information to enhance sensitivity of thermal lensing. Considering the rate of accumulation as an additional analytical signal, we achieved a threefold decrease in the limits of detection for 4-aminoazobenzene to the level of 7 µM in a batch mode with the same level of reproducibility. The details of observed thermal-lens signal behavior in cells are discussed. The possibilities to use thermal-lens detection for 4-aminoazobenzene determination in quartz capillaries in flow mode were discussed and a drastic thermal-lens signal enhancement was discovered. The corresponding limit of detection for 4-aminoazobenzene in a flow mode is further decreased to the level of 3 µM.

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The photochemical behaviors of a series of 9-phenanthreneacetamide (PA) derivatives were investigated using UV, fluorescence, and ¹H-NMR spectroscopy in acetonitrile solutions. To apply the electron transfer (ET) action of PA as a detecting moiety of chemosensors, 4′-(9-phenanthreneacetamido)-benzo-15-crown-5 (1) and 3′-methyl-4′-(9-phenanthreneacetamido)-benzo-15-crown-5 (2) were synthesized. After metal ion complex formation, the fluorescence intensity increased with increased concentration of the guest alkaline earth metal ions. The photochemical responses of the fluorescence intensity, as defined by the fluorescence intensity ratio (I_max/I₀) between free and complex of 1 for Ca²⁺, was determined to be 4.76. However, the addition of guest ions in a solution of 2 greatly enhanced the fluorescence intensity of 2. The I_max/I₀ of 2 was 16.6 for Ca²⁺. The efficiency of ET of PA can be tuned by adding an electron-donating group onto a suitable position; fluorescent 2 was able to read out metal ions as an “Off-On” fluorescence signal.

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The applicability of non-protected room temperature phosphorescence (NP-RTP) in real samples was demonstrated in the present work. In this methodology, only two reagents, potassium iodide and sodium sulfite, were used to obtain phosphorescent signals. Overlapping of the phosphorescence spectra was resolved by using first-derivative synchronous phosphorimetry. The synchronous first-derivative spectra of carbaryl and 1-naphthol in the mixture were completely separated by changing the synchronous wavelength interval; with 240 nm the first-derivative spectra of carbaryl were recorded, while with 200 nm those of 1-naphthol appeared. The intensities in the spectra were proportional to the concentration of carbaryl and 1-naphthol. The calibration graphs were linear up to at least 1.1 × 10^-5 mol L^-1 for carbaryl and 1.3 × 10^-5 mol L^-1 for 1-naphthol, and the correlation coefficients were 0.9971 and 0.9932, respectively. Carbaryl and 1-naphthol were successfully determined by the proposed method in a hydrolyzed sample of a commercial formulation.

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This paper described an FTIR spectrometer coupled to an auto-sampler and some attendant methodologies for a direct free fatty acid (FFA) method and triphenylphosphine (TPP)-based method for determination of FFA and peroxide value (PV) of edible oils by FTIR spectroscopy using spectral reconstitution. The viscosity of oil samples is reduced by mixing them with a diluent; such lowered viscosity allows them to be readily loaded into a flow-through transmission cell. The spectra of the neat oil samples are then reconstituted from those of the diluted samples by using the absorption of a spectral marker present in the diluent to determine the dilution ratio. For the direct FFA analysis, quantification is achieved using the (COO^-) band at 1712 cm^-1, while PV is determined using triphenylphosphine oxide (TPPO) absorption bands at 542 cm^-1. Calibration procedures and data are presented. Validation and performance data obtained with this automated system demonstrate that it is capable of analyzing ∼90 samples/h, a rate commensurate with the throughput required by commercial contract or high-volume process control laboratories.

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A simple and sensitive methodology for the simultaneous determination of levodopa and carbidopa in pharmaceutical samples is described. The method combines the advantages of fluorescence with partial least-squares (PLS) analysis, and requires no previous separation steps. The developed method is based on the oxidation of levodopa and carbidopa by cerium(IV) in a sulfuric acid medium and monitoring the fluorescence of the formed Ce(III) at λ_exc = 255 nm and λ_em = 355 nm. PLS uses differences in the reaction rates as a discriminatory parameter, and regresses the data of fluorescence vs. time onto the concentrations of the standards. Eight validation samples and seven commercial tablets were studied, using a nine-sample aqueous calibration set. The analyte recoveries from pharmaceuticals ranged from 98 to 101% for levodopa and from 100 to 108% for carbidopa. The results obtained by the developed method were statistically comparable to those obtained with high-performance liquid chromatography.

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Electrothermal atomic absorption spectrometry (ETAAS) is considered the most common and advanced technique to determine trace lithium in biological fluids. However, chloride existing in samples has been reported to create serious interferences. Nitric acid was verified as a chemical modifier to eliminate the interference of chloride in determining trace lithium in urine samples and the possible mechanism was also elucidated. The influence of chloride was completely eliminated by using 0.5% (v/v) HNO₃ as a chemical modifier. Confidence interval analysis on the difference for the slopes of linear regression curves indicated no significant difference between the slopes of aqueous and of urine-matched standard curves with and without 30 mmol/L NaCl in the presence of 0.5% (v/v) HNO₃ (P = 0.146). Thus the direct standardization with an aqueous calibration curve could be used instead of the standard-addition method. We conclude that the developed method is accurate and easily applicable for both routine use and research investigations.

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We demonstrated the imaging of local electron transfer-rate differences on a flat conductive carbon substrate, attributed to only surface functional groups, by using a scanning electrochemical microscopy (SECM) technique. These differences were clearly imaged by using a redox mediator with surface state sensitive electron transfer rates, even if the conductivity of each imaging area were almost identical. The carbon electrode surface was masked with a patterned photoresist, and selectively introduced oxygen functional groups using an oxygen plasma treatment. This patterned surface exhibited hardly any topographical features when observed by scanning electron microscopy (SEM), and a height difference of only 1.0 nm was observed with atomic force microscopy (AFM). However, the SECM feedback mode and substrate generation-tip collection (SG-TC) mode are able to distinguish these interfaces with an almost micrometer order resolution by utilizing the difference in the electron transfer rate for the Fe^2+/3+ mediator, and the current ratios for regions rich and poor in oxygen containing groups were 1.5 and 2.0, respectively. This technique could be employed for imaging and monitoring the electron transfer rates on various electrode surfaces, including fluorine and nitrogen terminated surfaces and a monolayer film patterned with micro or nano contact printing techniques.

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Due to the strong cation-exchange ability of Nafion and the excellent properties of multi-walled carbon nanotubes (MWCNTs), a highly sensitive and mercury-free method of determining trace levels of In³⁺ has been established based on the bifunctionality of a MWCNTs/Nafion modified glassy carbon electrode (GCE). The MWCNTs/Nafion modified GCE detects In³⁺ in a 0.01 M HAc-NaAc buffer solution at pH 5.0 using anodic stripping voltammetry (ASV). The experimental results suggest that a sensitive anodic stripping peak appears at -0.58 V on anodic stripping voltammograms, which can be used as an analytical signal for the determination of In³⁺. A good linear relationship between the stripping peak currents and the In³⁺ concentration is obtained, covering the concentration range from 5.0 × 10^-10 to 2.0 × 10^-7 M, with a correlation coefficient of 0.999; the detection limit is 1.0 × 10^-11 M. This proposed method has been applied to detect In³⁺ as a new way.

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A sensitive sensor for the determination of hydrogen peroxide (H₂O₂) was fabricated by immobilizing cytochrome c (cyt c) on binary self-assembled monolayers (SAMs) of 5-(1,2-dithiolan-3-yl)valeric acid (thioctic acid, T-COOH) and 5-(1,2-dithiolan-3-yl)valeramide (thioctic acid amide, T-NH₂) on gold electrodes. The electrochemical characteristics of immobilized cyt c were investigated by cyclic voltammetry, electrochemical impedance spectroscopy and chronoamperometry. The modified electrode showed good electrocatalytic activity towards the reduction of H₂O₂. The catalytic current is linear with the H₂O₂ concentration ranging from 10.0 to 300 µM with a correlation coefficient of 0.9996. The apparent Michaelis-Menten constant (K_m^app) was found to be 619 µM. The sensor achieved 95% of the steady-state current within 10 s, exhibiting high sensitivity (1.7 nA µM^-1 cm^-2).

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A new optode membrane for the sensitive and selective determination of thiocyanate ion, based on a change in the absorption spectrum of a polymer film, is proposed. A membrane composed of plasticized poly vinyl chloride (PVC), an Fe(III) Schiff-base complex as a chromoionophore and hexadecyl trimethyl ammoniuom bromide (HDTMABr) as a cationic additive was prepared. The influence of different plasticizers was studied concerning the sensitivity, linear range and selectivity of the membrane film. Satisfactory analytical sensing characteristics for determining thiocyanate ion were obtained in terms of the selectivity, reversibility and reproducibility with a good detecting range. In addition, the optical film responds to thiocyanate ion reversibly over a wide dynamic range 1.0 × 10^-8 to 1.0 × 10^-3 M with fast response and recovery times. The optode membrane has been applied to determine the thiocyanate ion in urine samples.

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We report on a hybridization assay using DNA microarrays for the quantification of amplification products of the uidA gene of E. coli. Using the stopped-PCR strategy, the amplified target DNA was strongly dependent on the applied gene copies. The quantification was carried out by a flow-through chemiluminescence microarray readout system. The DNA microarrays were based on a poly(ethylene glycol)-modified glass substrate. The probes on the surface were 18 or 25 nucleotides long and the quantified PCR product was 60 nucleotides. The amplification was stopped after 25 cycles; at this point amplification was in the middle of the logarithmical phase, and the spread between different DNA starting concentrations reached the maximum. A conjugate of streptavidin and horseradish peroxidase (HRP) bound to the biotinylated strands on the microarray surface and catalyzed the reaction of luminol and hydrogen peroxide. The generated light emission was recorded by a sensitive charge-coupled device (CCD) camera. The detection limit for the gene uidA (β-galactosidase) of E. coli was 1.1 × 10⁵ copies/mL. This system allowed for a sensitive detection and quantification of E. coli in a concentration range from 10⁶ to 10⁹ copies/mL.

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Real-time quantitative PCR (QPCR) has been proven to be a powerful tool for quantifying specific target DNA sequences. Compared to relative quantification, absolute quantification has the advantage of determining the absolute copy number of a given target, such as pathogen or plasmid DNA in vivo. However, matrix or impurities remaining in a DNA sample after various sample treatment procedures may influence a subsequent DNA analysis. In this work, we have compared methods of sample processing and validated the use of tissue genomic DNA as a universal external standard to facilitate quantification of plasmid DNA in biological matrix, especially addressing the amplification inhibition due to matrix effect and sample complexity. Also, we applied our high-throughput sample preparation and absolute quantification method to determine the distribution of an HIV plasmid DNA vaccine in vivo. Successful application showed the validity and reliability of the method in absolute quantification of a particular gene in vivo.

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A flow-through optosensor implemented with photochemically induced fluorescence (PIF) is reported for the simultaneous determination of thiabendazole (TBZ) and metsulfuron methyl (MET). TBZ is determined by measuring its native fluorescence once retained on the solid support filling the flow-cell of a FI-system. On the other hand, a strongly fluorescent photoproduct from MET is generated on-line in micellar medium by UV irradiation and monitored in a similar way to TBZ. MET photoproduct and TBZ are separated by placing in the flow-system a minicolumn, filled with C₁₈ silica gel, which allows their sequential arrival to the detection area. The sorption of the species on the solid support in the detection area provides a noticeable improvement in sensitivity and selectivity when comparing with their determination in homogeneous solution. The detection limits and RSDs for TBZ and MET are 2.5 and 3.3 ng ml^-1 and 1.1 and 2.4%, respectively. The method is successfully applied to environmental water samples.

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The present work describes a comparative study involving two sequential injection enzymatic procedures for the spectrophotometric determination of glucose in milk samples. The determinations were based on the use of the enzymes, glucose oxidase and peroxidase, in solution or immobilized, and 4-aminophenazone and phenol as chromogenic reagents. In the first procedure, 8.4 IU of glucose oxidase and 0.5 IU of peroxidase were consumed in each determination. In the second procedure, 107 IU of glucose oxidase and 105 IU of peroxidase, immobilized in glass beads, were sequentially packed into the same reactor. The reactor allowed us to perform about 600 continuous determinations with no activity loss. The proposed systems allowed the determination of glucose up to 120 mg L^-1 in milk samples with a precision, considering the RSD (%) values, lower than 3.5%. The results obtained for the two systems were comparatively evaluated against a routine enzymatic method, showing a relative deviation of less than 3%.

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A highly sensitive and simple method for the analysis of chlorothalonil was presented using a liquid chromatograph/mass spectrometer equipped with an atmospheric pressure photoionization (APPI) source. Chlorothalonil is one of the most extensively used fungicides. The major degraded product of chlorothalonil, 4-hydroxy-2,5,6-trichloroisonaphthonitrile (4OH-TPN), was also quantified with sensitivity similar to that of chlorothalonil. The method was applied to the determination of chlorothalonil in aqueous environment and food samples. The method detection limits (MDLs) of chlorothalonil for aqueous samples and cucumber were determined to be 0.18 and 3.2 ng g^-1, respectively. At several estuarial locations, chlorothalonil was detected with a maximum of 1.1 ng L^-1. On the other hand, 4OH-TPN was detected not from estuaries but from rivers with a maximum of 14 ng L^-1.

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Dibutyldi(4-chlorobenzohydroxamato)tin(IV) is a new diorganotin(IV) arylhydroxamate complex with 4-chloro-benzohydroxamic acid as ligand which shows high in vivo and in vitro antitumor activity. A high performance liquid chromatographic (HPLC) method using a Diamonsil ODS column was first validated in the pharmacokinetic studies in rat plasma. The plasma was deproteinized with methanol that contained acetanilide as the internal standard. The mobile phase was a mixture of methanol and 0.5% trifluoroacetic acid (TFA) in water (30:70) (pH 3.0). The detection wavelength was set at 238 nm. A linear curve over the concentration range 0.1 - 25 µg/ml (r = 0.9992) was obtained. The method was used to determine the concentration-time profiles for dibutyldi(4-chlorobenzohydroxamato)tin(IV) in the plasma after a single intravenous dose of 2, 5, and 12 mg/kg to rats. The pharmacokinetics parameter calculations and modeling were carried out using the 3p97 pharmacokinetics software. A nonlinear pharmacokinetics was found in rats at doses from 2 to 12 mg/kg. The results showed that the concentration-time curves of dibutyldi(4-chlorobenzohydroxamato)-tin(IV) in rat plasma could be fitted to two-compartment model.

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Nanofluids, i.e., colloidal dispersions of nanoparticles in a base liquid (solvent), have received considerable attention in the last years due to their potential applications. One attractive feature of these systems is that their thermal conductivity can exceed the corresponding values of the base fluid and of the fluid with large particles of the same chemical composition. However, there is a lack of agreement between published results and the suggested mechanisms which explain the thermal conductivity enhancement. Here we show the possibilities of the inverse photopyroelectric method for the determination of the effective thermal effusivity of the system constituted by small ZnO nanoparticles dispersed in dimethyl sulfoxide, as a function of the nanoparticles volumetric fraction. Using a phenomenological model we estimated the thermal conductivity of these colloidal samples without observing any significant enhancement of this parameter above effective medium predictions.

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A new modified silica gel doped with 5-(4-dimethylaminobenzylidene)-rhodanine was prepared for separation, preconcentration and determination of silver ion by atomic absorption spectrometry. This new modified silica gel was used as an effective adsorbent for the solid phase extraction of Ag⁺ from aqueous solutions. The variables that influence the adsorption/desorption of trace levels of Ag⁺ were optimized in the column process. The preconcentration factor and capacity of the adsorbent at optimum conditions were found as 220 and 420 µg Ag⁺ per gram of adsorbent, respectively. The relative standard deviation and the detection limit for measurement of Ag⁺ in our experiments were less than 1.5% (n = 10) and 0.02 µg L^-1, respectively. Common coexisting ions did not interfere with the separation and determination of silver ion. The proposed method was successfully applied for preconcentration and determination of silver ion in some spiked water samples.

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In order to establish a standard analytical method for the determination of trace amounts of tin and lead in magnesium and its alloys, which could be found in neither JIS nor ISO standards, an interlaboratory testing with inductively coupled plasma atomic emission spectrometry (ICP-AES) has been put into practice. Simple dissolution with nitric and hydrochloric acids and sample nebulization procedures were finally concluded to be suitable for standardization. The analytical methods, proposed in this study have been provided as newly established JIS standards.

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Anionic surfactant solutions of sodium dodecylbenzenesulfonate (SDBS) and sodium dodecylsulfate (SDS) separate into two phases through cooling of the solution and the addition of salts. Thiourea (TU) reacts with many metals to form cationic complexes of [M(TU)_n]^m+; some of them extract into the SDBS phase. The separation was examined for lead and tin in commercially purchased solders. More than 95% lead was extracted into the SDBS phase, while tin remained in the aqueous phase. An abnormal decrease in extractability was observed for the [M(TU)_n]^m+ of noble metal complexes at low metal concentrations. The surfactant phases of SDBS and SDS were confirmed as lamellar structures using small angle X-ray scattering (SAXS), and the stability and rigidity of this structure influenced the extractability of the [Au(TU)_n]³⁺ complex. The separation of gold(III) and palladium(II) was examined for the SDS system.

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Electrostatic interactions of calf thymus DNA (ct-DNA) with a positive charged polymer were investigated based on measurements of enhanced resonance light scattering (RLS) signals, and were proved by scanning electron microscopy (SEM). The optimal pH value was 7.0 in a phosphate-buffered saline solution (PBS) and the maximum RLS peak located at 344.8 nm. The RLS signal enhancement (ΔI_RLS) could be linearly correlated with the concentration of ct-DNA in the range of 0.0900 to 2.70 µg mL^-1, and the detection limit (S/N = 3) was 17.0 ng mL^-1. The binding ratio and the binding constant between DNA and polymer were also provided.

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This article was retracted.

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