One novel electrochemical immunosensor was constructed by immobilizing capture antibody of alpha-fetoprotein (AFP Ab(1)) on a nafion/nanogold-particle modified glassy carbon electrode. With a sandwich immunoassay, one DNA-derived magnetic nanoprobe, simplified as DNA/(ZMPs-HRP-AFP Ab(2))(n), was employed for the detection of AFP. The fabricated procedure of the proposed biosensor was characterized by cyclic voltammetry and electrochemical impedance spectroscopy. The performance and factors influencing the performance of the biosensor were also evaluated. Under optimal conditions, the developed biosensor exhibited a well-defined electrochemical behavior toward the reduction of AFP ranging from 0.01 to 200 ng/mL with a detection limit of 4 pg/mL (S/N = 3). The biosensor was applied to the determination of AFP in serum with satisfactory results. It is important to note that the sandwich nanochainmodified electro-immunosensor provided an alternative substrate for the immobilization of other tumor markers.

In this study, a method for the determination of low concentrations of lead in beer samples using solid-phase extraction with a flow injection analysis system and detection by flame atomic absorption spectrometry (FAAS) was developed. Moringa oleifera seeds were used as a biosorbent material. Chemical and flow variables of the online preconcentration system, such as sample pH, preconcentration flow rate, eluent flow rate, eluent concentration, particle size, and sorbent mass, were studied. The optimum extraction conditions were obtained using a sample pH of 6.0, sample flow rate of 6.0 mL min(-1), 63.0 mg of sorbent mass, and 2.0 mol L(-1) HNO(3) at a flow rate of 2.0 mL min(-1) as the eluent. With the optimized conditions, the preconcentration factor, precision, detection limit, consumption index, and sample throughput were estimated as 93, 0.3% (10.0 μg L(-1), n = 7), 7.5 μg L(-1), 0.11 mL, and 23 samples per hour, respectively. The method developed was successfully applied to beer samples and recovery tests, with recovery ranging from 80% to 100%.

We report the design and operation of a Virtual Instrument (VI) system based on LabVIEW 2009 for laser-induced fluorescence experiments. This system achieves synchronous control of equipment and acquisition of real-time fluorescence data communicating with a single computer via GPIB, USB, RS232, and parallel ports. The reported VI system can also accomplish data display, saving, and analysis, and printing the results. The VI system performs sequences of operations automatically, and this system has been successfully applied to obtain the excitation and dispersion spectra of α-methylnaphthalene. The reported VI system opens up new possibilities for researchers and increases the efficiency and precision of experiments. The design and operation of the VI system are described in detail in this paper, and the advantages that this system can provide are highlighted.

A study was conveyed to produce estolide ester using ricinoleic acid as the backbone. The ricinoleic acid reacted with saturated fatty acid from C8-C18. These reactions were conducted under vacuum at 60°C for 24 h without solvent. The reaction used acid catalyst, sulphuric acid. The new saturate ricinoleic estolide esters show superior low-temperature properties (-52 ± 0.08°C) and high flash point (>300°C). The yield of the neat estolide esters ranged from 52% to 96%. The viscosity range was 51 ± 0.08 to 86 ± 0.01 cp. These new saturated estolide esters were also compared with saturated branched estolide esters.

A fast and efficient automated method using a sequential injection analysis (SIA) system, based on the Griess, reaction was developed for the determination of nitrate and nitrite in infant formulas and milk powder. The system enables to mix a measured amount of sample (previously constituted in the liquid form and deproteinized) with the chromogenic reagent to produce a colored substance whose absorbance was recorded. For nitrate determination, an on-line prereduction step was added by passing the sample through a Cd minicolumn. The system was controlled from a PC by means of a user-friendly program. Figures of merit include linearity (r(2) > 0.999 for both analytes), limits of detection (0.32 mg kg(-1) NO(3)-N, and 0.05 mg kg(-1) NO(2)-N), and precision (s(r)%) 0.8-3.0. Results were statistically in good agreement with those obtained with the reference ISO-IDF method. The sampling frequency was 30 hour(-1) (nitrate) and 80 hour(-1) (nitrite) when performed separately.

This paper presents the automatic discrimination of geographical origins of milks from Western Yunnan Plateau areas and eastern China by excitation-emission fluorescence spectrometry and chemometrics. Genuine plateau milks (n = 60) and milks from eastern China (n = 89) are scanned in the regions of 180-300 nm for excitation and 200-800 nm for emission. Different options of data analysis are investigated and compared in terms of their performance in discriminating milks of different geographical origins: (1) two-way partial least squares discriminant analysis (PLSDA) based on excitation and emission spectra, respectively; (2) two-way PLSDA based on fusion of excitation and emission spectra; (3) three-way PLSDA based on excitation-emission matrix spectra. The two-way PLSDA methods with excitation spectra, emission spectra, and fusion of excitation and emission spectra correctly classify 91.3%, 88.6%, and 95.3% of the milk samples, respectively; while the total accuracy of three-way PLSDA is 96.0%. The results demonstrate the two-way data combining excitation and emission spectra are sufficient to characterize and identify the plateau milks. Considering both model accuracy and the analytical time required, two-way PLS-DA with fusion of excitation and emission spectra is recommended as a reliable and quick method to discriminate plateau milks from ordinary milks.

A preparative gas chromatography (pGC) method was developed for the separation of volatile components from the methanol extract of Curcuma rhizome. The compounds were separated on a stainless steel column packed with 10% OV-101 (3 m × 6 mm, i.d.), and then, the effluent was split into two gas flows. One percent of the effluent passed to the flame ionization detector (FID) for detection and the remaining 99% were directed to the fraction collector. Five volatile compounds were collected from the methanol extract of Curcuma rhizome (5 g/mL) after 83 single injections (20 uL) with the yield of 5.1-46.2 mg. Furthermore, the structures of the obtained compounds were identified as β-elemene, curzerene, curzerenone, curcumenol, and curcumenone by MS and NMR spectra, respectively.

A new method for Ag determination in water samples using solid phase extraction (SPE) coupled to a flow injection system and flame atomic absorption spectrometry was developed. The sorbent used for Ag preconcentration and extraction was the termite digestion product. Flow and chemical variables of the system were optimized through a multivariate procedure. The factors selected were adsorbent mass, buffer type and concentration, sample pH, and sample flow rate. The detection limit and precision were 3.4 μg L(-1) and 3.8% (n = 6, 15 μg L(-1)), respectively. The enrichment factor and the linear working range were, respectively, 21 and 10-50 μg L(-1). Results for recovery tests using different water samples were between 96 and 107%. The proposed methodology was applied with success for the determination of Ag in water used to wash clothes impregnated with silver nanoparticles, supplied by a factory located in Santa Catarina, Brazil.

An automated multiparametric water analyser was developed and evaluated. The system was based on Sequential Injection Analysis and featured a photometric detection system comprising a tricolour RGB LED source and a photodiode. A program compiled in Visual Basic was used to control the SIA flow system, the LEDs, and the data acquisition and processing. The program loads and executes methods written in ASCII and stored as text files. The system was capable of handling up to four methods simultaneously. When used to carry out methods based on the APHA standard methods, the figures of merit obtained were considered satisfactory for the purpose. The total cost was under US $4600. It was concluded that the analyser is appropriate for routine use and has potential for an increased number of simultaneous methods and for enhanced capabilities if new versions of the software are developed.

Acetaldehyde (ethanal) is a genotoxic carcinogen, which may occur naturally or as an added flavour in foods. We have developed an efficient method to analyze the compound in a wide variety of food matrices. The analysis is conducted using headspace (HS) gas chromatography (GC) with flame ionization detector. Using a robot autosampler, the samples are digested in full automation with simulated gastric fluid (1 h at 37°C) under shaking, which frees acetaldehyde loosely bound to matrix compounds. Afterwards, an aliquot of the HS is injected into the GC system. Standard addition was applied for quantification to compensate for matrix effects. The precision of the method was sufficient (<3% coefficient of variation). The limit of detection was 0.01 mg/L and the limit of quantification was 0.04 mg/L. 140 authentic samples were analyzed. The acetaldehyde content in apples was 0.97 ± 0.80 mg/kg, orange juice contained 3.86 ± 2.88 mg/kg. The highest concentration was determined in a yoghurt (17 mg/kg). A first-exposure estimation resulted in a daily acetaldehyde intake of less than 0.1 mg/kg bodyweight from food, which is considerably lower than the exposures from alcohol consumption or tobacco smoking.

Parallel liquid handling systems are widely used in different applications of life sciences. In order to avoid false positive or negative results which lead to higher costs due to the replication of the experiments it is necessary to monitor the process and success of liquid delivery. An easy method for the determination of the liquid levels in microplates has been developed and evaluated. The optical method bases on the measurement of the liquid level using CCD cameras followed by special algorithms for the evaluation and visualization of the measured data. The proposed method was tested in changing environmental lighting for two different liquids. These tests confirm our approach towards optical liquid level determination for smallest volumes in microplates and also show the challenges regarding environmental lighting and different physical properties of fluids.

A simple flow injection with flame photometric detection has been developed for determination of sodium, potassium, and total alkalies in portland cement, fly ash, admixtures, and water of concrete. A liquid sample or a digest of solid sample was injected into a water carrier stream which flowed to a flame photometer. A change in emission intensity at a selected wavelength was recorded as a peak. An amplifier circuit was fabricated, which helped improve sensitivity of the flame photometer. Calibration graphs in the range of 0.05-1.0 mg L(-1) and 1.0-20.0 mg L(-1) were obtained with a detection limit of 0.02 mg L(-1), for both potassium and sodium determination. Relative standard deviations for 11 replicates of injecting of 10 mg L(-1) potassium and sodium solutions were 1.69 and 1.79%, respectively. Sample throughput of 120 h(-1) was achieved. The proposed method was successfully applied to portland cement, fly ash, admixtures, and water samples validated by the ASTM standard method and certified reference materials of portland cement.

A photometric procedure for the determination of ClO(-) in tap water employing a miniaturized multicommuted flow analysis setup and an LED-based photometer is described. The analytical procedure was implemented using leucocrystal violet (LCV; 4,4',4''-methylidynetris (N,N-dimethylaniline), C(25)H(31)N(3)) as a chromogenic reagent. Solenoid micropumps employed for solutions propelling were assembled together with the photometer in order to compose a compact unit of small dimensions. After control variables optimization, the system was applied for the determination of ClO(-) in samples of tap water, and aiming accuracy assessment samples were also analyzed using an independent method. Applying the paired t-test between results obtained using both methods, no significant difference at the 95% confidence level was observed. Other useful features include low reagent consumption, 2.4 μg of LCV per determination, a linear response ranging from 0.02 up to 2.0 mg L(-1) ClO(-), a relative standard deviation of 1.0% (n = 11) for samples containing 0.2 mg L(-1) ClO(-), a detection limit of 6.0 μg L(-1) ClO(-), a sampling throughput of 84 determinations per hour, and a waste generation of 432 μL per determination.

Lithol Rubine B (LRB; the disodium salt of 3-hydroxy-4-[(4-methyl-2-sulfophenyl) azo]-2-naphthalenecarboxylic acid) was detected using high-performance liquid chromatography with an electrochemical (antimony film on silver) detector (HPLC-ECD). For direct current (DC) mode, with the current at a constant potential, and measurements with suitable experimental parameters, a linear concentration from 0.125 to 1.80 μg/mL was found. The detection limit of our method was approximately 2.0 ng/mL. An antimony-modified silver detector was used to demonstrate that LRB is electrochemically reduced in acidic media and to analyze commercial cosmetics to determine their LRB content. Findings using HPLC-ECD and HPLC with an ultraviolet detector were comparable.