Determination of 3-hydroxyanthranilic acid in the sweat of healthy older adults.

3-Hydroxyanthranillic acid (3HAA) is one of the key metabolites from the tryptophan (TRP) metabolism pathway and is associated with aging, age-associated diseases, and healthy lifespan extension. This study aims to detect 3HAA in the sweat of healthy older adults using simple, high-performance liquid chromatography (HPLC) method. Chromatographic separation using 20 mmol/L sodium acetate, 3 mmol/L zinc acetate, and 7% (v/v) acetonitrile as mobile phase is possible to simultaneous detect 3HAA, KYN, and TRP with UV and fluorescence detection, respectively, under 6 min.

Carbon dots derived from citric acid and urea as fluorometric probe for determining melamine contamination in infant formula sample.

Melamine has been intentionally added into food products to increase the protein count at less cost, especially in dairy products for infant resulting in serious adverse effects on health of consumers. Therefore, this study aimed to develop a method to quantify melamine in dairy products based on the change of fluorescent properties of carbon dots (CDs) as sensing probe. CDs with green-fluorescent emission were synthesized from citric acid and urea under microwave irradiation.

Microfluidic paper-based analytical device for determination of sucrose in sugarcane juice using Benedict's reagent.

This work presents a microfluidic paper-based analytical device (μPAD) for the determination of sucrose using the Benedict's test. An asymmetric dumbbell-shaped hydrophobic barrier was produced by rubber stamping the barrier pattern onto a laboratory filter paper. Hydrochloric acid and solution containing sucrose were successively deposited onto the sample reservoir of the μPAD attached to a glass slide.

An application of miniaturized electrochemical sensing for determination of arsenic in herbal medicines.

This study aimed to create a miniaturized electrochemical platform for detecting As(III) contamination in herbal medicines. To reduce the operational steps of modification and determination, only a single drop of mixed standard Au(III) and sample solution is proposed to perform the electrochemical measurements using a screen-printed graphene electrode (SPGE). Square wave anodic stripping voltammetry was employed to integrate the simultaneous modification and determination processes.

Dual-Purpose Photometric-Conductivity Detector for Simultaneous and Sequential Measurements in Flow Analysis.

This work presents a new dual-purpose detector for photometric and conductivity measurements in flow-based analysis. The photometric detector is a paired emitter-detector diode (PEDD) device, whilst the conductivity detection employs a capacitively coupled contactless conductivity detector (C4D). The flow-through detection cell is a rectangular acrylic block (ca.

Contactless conductivity detector from printed circuit board for paper-based analytical systems.

This work presents a capacitively coupled contactless conductivity detector (CD) etched out from a printed circuit board (PCB) as potential sensor for paper-based analytical systems. Two lines of any desirable pattern forming 35-μm thick planar copper electrodes were produced on a PCB plate (40 mm × 60 mm) by photolithography. The final PCB plate was covered with polypropylene film to serve as the insulating layer for the CD detector.

Simultaneous and direct determination of urea and creatinine in human urine using a cost-effective flow injection system equipped with in-house contactless conductivity detector and LED colorimeter.

This work presents a cost-effective and simple flow injection analysis (FIA) system for simultaneous and direct determination of urea and creatinine in human urine. The FIA system comprises two in-house detectors, a contactless conductivity detector and a light emitting diode (LED) detector. The contactless detector was built as a flow-through detection cell with axial electrodes, commonly known as capacitively coupled contactless conductivity detector (C4D) and the diode detector was fabricated based on the concept of paired emitter detector diodes (PEDD).

Temperature-dependent schlieren effect in liquid flow for chemical analysis.

In flow analysis, such as flow injection analysis, liquid lens is formed at the boundary between two adjacent liquid media which have different refractive indices. Light refraction at the liquid interface gives the so-called 'schlieren signal'. Schlieren effect is both concentration-dependent and temperature-dependent.

Development of flow systems incorporating membraneless vaporization units and flow-through contactless conductivity detector for determination of dissolved ammonium and sulfide in canal water.

Use of membraneless vaporization (MBL-VP) unit with two cone-shaped reservoirs is presented for on-line separation and detection of non-volatile species. A flow system comprising two sets of MBL-VP units with a single in-house capacitively coupled contactless conductivity detector (C4D) was developed for dual determination of ammonium and sulfide ions. Using the continuous-flow section, two zones (280μL) of a sample, either mixed with sodium hydroxide (for ammonium) or hydrochloric acid (for sulfide), are separately delivered into the donor reservoir of the MBL-VP units.

Simultaneous determination of iodide and creatinine in human urine by flow analysis with an on-line sample treatment column.

This work presents the first flow system for direct analysis of iodide and creatinine suitable for screening of human urine samples. The system had a mini-column packed with strong anion exchange resin for on-line extraction of iodide. After injection of a sample on the column the unretained urine sample was analyzed for creatinine in one section of the flow system using the Jaffe's reaction with spectrometric detection at 520 nm.

Cross injection analysis: concept and operation for simultaneous injection of sample and reagents in flow analysis.

This work presents a new flow injection strategy, called 'cross injection analysis' or CIA, an alternative cost-effective approach in flow analysis. The flow platform is made from a rectangular acrylic block, approximately 5×3×1.5 cm (x×y×z), with crossing cylindrical channels drilled out along the x- and y-axis of the block.

Enantiomeric separation of some common controlled stimulants by capillary electrophoresis with contactless conductivity detection.

CE methods with capacitively coupled contactless conductivity detection (C(4)D) were developed for the enantiomeric separation of the following stimulants: amphetamine (AP), methamphetamine (MA), ephedrine (EP), pseudoephedrine (PE), norephedrine (NE) and norpseudoephedrine (NPE). Acetic acid (pH 2.5 and 2.