Basal serum luteinising hormone cut-off, and its utility and cost-effectiveness for aiding the diagnosis of the onset of puberty in girls with early stages of breast development.

OBJECTIVE: To determine basal and gonadotrophin-releasing hormone analogue (GnRHa)-stimulated peak luteinising hormone (LH) cut-offs to diagnose onset of early or normal puberty in girls with each Tanner stage of breast (II and III). DESIGN, PATIENTS AND MEASUREMENTS: A retrospective study of 601 girls with breast onset before 8 years of age who underwent GnRHa test was conducted. Patients were categorized as CPP and premature thelarche. Each group was divided into two subgroups; Tanner II and III. Cost-effectiveness analysis was performed. RESULTS: In comparison with basal LH cut-off of 0.3 IU/L, basal LH cut-off of 0.2 IU/L had comparable specificity (Tanner II: 98.0% vs 94.8%, Tanner III: 98.8% vs 93.8%), but greater sensitivity (Tanner II: 28.3% vs 41.7%, Tanner III: 45.2% vs 59.3%). Specificity of basal LH cut-off of 0.2 IU/L was not inferior to that of the traditionally used peak LH of 5 IU/L. Using basal LH cut-off of 0.2 IU/L followed by GnRHa test in girls with negative basal LH was more cost-saving when compared with using the cut-off of 0.3 IU/L. Moreover, using basal LH cut-off of 0.2 IU/L followed by GnRHa test provided a cost reduction when compared with performing GnRHa test in all patients. CONCLUSIONS: Basal serum LH cut-off of 0.2 IU/L could be a simple and cost-saving tool for initial diagnosis of onset of early or normal puberty in girls with Tanner II and III before proceeding to GnRH testing.

Microwave Assisted Synthesis of N-Doped Carbon Dots: an Easy, Fast and Cheap Sensor for Determination of Aspartic Acid in Sport Supplements.

In this work, determination of aspartic acid by N-doped carbon dots (N-CDs) was studied at optimum condition. Characterization and morphology of surface of N-CDs were carried out by FT-IR and HRTEM. N-doped carbon dots size was 10 nm. Quenching was very fast after addition of aspartic acid that is an important property of this sensor. Optimum conditions for pH and excitation wavelength were 8 and 360 nm, respectively. Linear dynamic range and limit of detection for aspartic acid were 0.5-50 µM and 90 nM, respectively. This method was used for aspartic acid determination in human serum and sport supplement powder as real samples. Performance of this sensor was also compared with other fluorescent sensors.

Plasmon-coupled 3D porous hotspot architecture for super-sensitive quantitative SERS sensing of toxic substances on real sample surfaces.

This paper reports a facile, fast, and cost-effective method for the synthesis of three-dimensional (3D) porous AgNPs/Cu composites as SERS substrates for the super-sensitive and quantitative detection of food organic contaminations. Due to the 3D porous hotspot architecture and the strong plasmonic coupling between Ag and Cu, the porous AgNPs/Cu substrate achieves ultrasensitive detection of multiple analytes as low as 10-11 M (crystal violet, CV), 10-9 M (malachite green, MG), 10-11 M (acephate), and 10-9 M (thiram) even with a portable Raman device. Moreover, this 3D solid substrate has good signal uniformity (RSD < 11%) and superior stability (<14% signal loss), allowing for practical SERS detections. Importantly, by simply wiping the real sample surface using the substrate, it successfully detects CV and MG residues on crayfish, and the limit of detection (LOD) of CV and MG is determined to be 1.14 × 10-9 M and 0.94 × 10-7 M, respectively. Further, the substrate can also be applied to detect acephate on eggplant with a LOD of 1.41 × 10-9 M and thiram on an apple surface with a LOD of 1.04 × 10-7 M. Note that all these SERS detections on real samples have a broad dynamic concentration range and a good linear dependence. As a "proof of concept", multi-component detection on a real sample has also been demonstrated. This 3D solid substrate possesses excellent detection sensitivity, diversity, and accuracy, which allows rapid and reliable determination of toxic substances in foods.

Paper-Based Analytical Biosensor Chip Designed from Graphene-Nanoplatelet-Amphiphilic-diblock-co-Polymer Composite for Cortisol Detection in Human Saliva.

Cortisol has been identified as a biomarker in saliva to monitor psychological stress. In this work, we report a label-free paper-based electrical biosensor chip to quantify salivary cortisol at a point-of-care (POC) level. A high specificity of the sensor chip to detect cortisol with a detection limit of 3 pg/mL was achieved by conjugating anticortisol antibody (anti-CAB) on top of gold (Au) microelectrodes using 3,3'-dithiodipropionic acid di(N-hydroxysuccinimide ester (DTSP) as a self-assembled monolayer (SAM) agent. The electrode design utilized poly(styrene)-block-poly(acrylic acid) (PS67-b-PAA27) polymer and graphene nanoplatelets (GP) suspension coated on filter paper to increase the sensitivity of the immune response. A biosensor chip was then integrated with a lab-built low-cost miniaturized printed circuit board (PCB) to provide an electrical connection and to wirelessly transmit/receive electrical signals using MATLAB. This fully integrated proposed hand-held device successfully exhibited a wide cortisol-detection range from 3 pg/mL to 10 µg/mL, with a sensitivity of 50 Ω (pg mL-1)-1. The performance of the proposed cortisol sensor chip was validated using an enzyme-linked immunosorbent assay (ELISA) technique with a regression value of 0.9951. The advantages of the newly developed cortisol immune biosensor over previously reported chips include an improved limit of detection, no need for additional redox medium for electron exchange, faster response to achieve stable data, excellent shelf life, and its economical production.

Quick, easy, cheap, effective, rugged, and safe sample preparation approach for pesticide residue analysis using traditional detectors in chromatography: A review.

In pesticide residue analysis, relatively low-sensitivity traditional detectors, such as UV, diode array, electron-capture, flame photometric, and nitrogen-phosphorus detectors, have been used following classical sample preparation (liquid-liquid extraction and open glass column cleanup); however, the extraction method is laborious, time-consuming, and requires large volumes of toxic organic solvents. A quick, easy, cheap, effective, rugged, and safe method was introduced in 2003 and coupled with selective and sensitive mass detectors to overcome the aforementioned drawbacks. Compared to traditional detectors, mass spectrometers are still far more expensive and not available in most modestly equipped laboratories, owing to maintenance and cost-related issues. Even available, traditional detectors are still being used for analysis of residues in agricultural commodities. It is widely known that the quick, easy, cheap, effective, rugged, and safe method is incompatible with conventional detectors owing to matrix complexity and low sensitivity. Therefore, modifications using column/cartridge-based solid-phase extraction instead of dispersive solid-phase extraction for cleanup have been applied in most cases to compensate and enable the adaptation of the extraction method to conventional detectors. In gas chromatography, the matrix enhancement effect of some analytes has been observed, which lowers the limit of detection and, therefore, enables gas chromatography to be compatible with the quick, easy, cheap, effective, rugged, and safe extraction method. For liquid chromatography with a UV detector, a combination of column/cartridge-based solid-phase extraction and dispersive solid-phase extraction was found to reduce the matrix interference and increase the sensitivity. A suitable double-layer column/cartridge-based solid-phase extraction might be the perfect solution, instead of a time-consuming combination of column/cartridge-based solid-phase extraction and dispersive solid-phase extraction. Therefore, replacing dispersive solid-phase extraction with column/cartridge-based solid-phase extraction in the cleanup step can make the quick, easy, cheap, effective, rugged, and safe extraction method compatible with traditional detectors for more sensitive, effective, and green analysis.

Thermoseparating aqueous two-phase systems: Recent trends and mechanisms.

Having the benefits of being environmentally friendly, providing a mild environment for bioseparation, and scalability, aqueous two-phase systems (ATPSs) have increasingly caught the attention of industry and researchers for their application in the isolation and recovery of bioproducts. The limitations of conventional ATPSs give rise to the development of temperature-induced ATPSs that have distinctive thermoseparating properties and easy recyclability. This review starts with a brief introduction to thermoseparating ATPSs, including its history, unique characteristics and advantages, and lastly, key factors that influence partitioning. The underlying mechanism of temperature-induced ATPSs is covered together with a summary of recent applications. Thermoseparating ATPSs have been proven as a solution to the demand for economically favorable and environmentally friendly industrial-scale bioextraction and purification techniques.

Corrin-based chemosensors for the ASSURED detection of endogenous cyanide.

Cassava (Manihot esculenta Crantz) is a staple food for more than 500 million people, especially in Africa and South America. However, its consumption bears risks as it contains cyanogenic glycosides that convert enzymatically to toxic cyanide during cell damage. To avoid serious health problems by unintentional cyanide intake, this dangerous product of decomposition must be removed before consumption. For monitoring such food processing procedures and for controlling the quality and safety of cassava products on the market, a convenient and reliable analytical method for routine applications without laboratory equipment is required. This Perspective summarizes the authors' work on corrin-based chemosensors for the ('naked-eye') detection of endogenous cyanide in cassava samples. Considering selectivity, sensitivity, handling and speed of detection, these systems are superior to currently applied methods. Based on these properties, the development of a test kit for application by rural farmers in remote locations is proposed.

Reducing the cost of evaluating the committor by a fitting procedure.

Correct identification of reaction coordinates in complex systems is essential for understanding the mechanisms of their reaction dynamics. Existing methods for identifying reaction coordinates typically require knowledge of the committor--the probability of a given configuration to reach the product basin. The high computational cost of evaluating committors has limited applications of methods for identifying reaction coordinates. We proposed a fitting procedure that can reduce the cost of evaluating committors by an order of magnitude or more. The method only requires evaluating the committors of a few configurations in a transition path by the standard and costly shooting procedure. The committors of the other configurations are then estimated with great accuracy by a sigmoid function derived from fitting the few numerically evaluated committors. The method has been systematically tested on a model system of a Brownian particle moving in a one-dimensional double-well potential, and a small biomolecular system--the isomerization of alanine dipeptide in vacuum and in explicit water.

Isolation, cytotoxic evaluation, and simultaneous quantification of eight bioactive secondary metabolites from Cicer microphyllum by high-performance thin-layer chromatography.

Chemical investigation of Cicer microphyllum resulted in the isolation and characterization of eight natural products viz. Stigmasterol, Oleanolic acid-3-acetate, Oleanolic acid, Biochanin A, Genistein, Pratensein, Chrysoeriol, and Luteolin. Herein, we report a novel, accurate, and cost-effective high-performance thin-layer chromatography method for the simultaneous quantification of the isolated natural products on silica-gel 60F254 plates using the solvent system n-hexane/ethyl acetate/formic acid (9.0:6.5:0.8, v/v/v). Natural products were quantified after postchromatographic derivatization with ceric ammonium sulfate. The method was validated as per the International Conference on Harmonization guidelines. All calibration curves showed a good linear relationship (r > 0.9943) within the test range. Precision was assessed by intra- and interday tests with relative standard deviations <1.82%, accuracy validation recovery 98.38-99.57% with relative standard deviations <1.00%. On quantification, Pratensein was a major constituent (0.921%). The screening for cytotoxic activity using a 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide assay resulted into identification of Luteolin as potent molecule with IC50 3.5 and 25.6 µg/mL against murine melanoma and human epidermoid carcinoma cell lines, respectively.

Accuracy, precision, usability, and cost of free chlorine residual testing methods.

Chlorine is the most widely used disinfectant worldwide, partially because residual protection is maintained after treatment. This residual is measured using colorimetric test kits varying in accuracy, precision, training required, and cost. Seven commercially available colorimeters, color wheel and test tube comparator kits, pool test kits, and test strips were evaluated for use in low-resource settings by: (1) measuring in quintuplicate 11 samples from 0.0-4.0 mg/L free chlorine residual in laboratory and natural light settings to determine accuracy and precision; (2) conducting volunteer testing where participants used and evaluated each test kit; and (3) comparing costs. Laboratory accuracy ranged from 5.1-40.5% measurement error, with colorimeters the most accurate and test strip methods the least. Variation between laboratory and natural light readings occurred with one test strip method. Volunteer participants found test strip methods easiest and color wheel methods most difficult, and were most confident in the colorimeter and least confident in test strip methods. Costs range from 3.50-444 USD for 100 tests. Application of a decision matrix found colorimeters and test tube comparator kits were most appropriate for use in low-resource settings; it is recommended users apply the decision matrix themselves, as the appropriate kit might vary by context.

Speciation analysis of arsenic by selective hydride generation-cryotrapping-atomic fluorescence spectrometry with flame-in-gas-shield atomizer: achieving extremely low detection limits with inexpensive instrumentation.

This work describes the method of a selective hydride generation-cryotrapping (HG-CT) coupled to an extremely sensitive but simple in-house assembled and designed atomic fluorescence spectrometry (AFS) instrument for determination of toxicologically important As species. Here, an advanced flame-in-gas-shield atomizer (FIGS) was interfaced to HG-CT and its performance was compared to a standard miniature diffusion flame (MDF) atomizer. A significant improvement both in sensitivity and baseline noise was found that was reflected in improved (4 times) limits of detection (LODs). The yielded LODs with the FIGS atomizer were 0.44, 0.74, 0.15, 0.17 and 0.67 ng L(-1) for arsenite, total inorganic, mono-, dimethylated As and trimethylarsine oxide, respectively. Moreover, the sensitivities with FIGS and MDF were equal for all As species, allowing for the possibility of single species standardization with arsenate standard for accurate quantification of all other As species. The accuracy of HG-CT-AFS with FIGS was verified by speciation analysis in two samples of bottled drinking water and certified reference materials, NRC CASS-5 (nearshore seawater) and SLRS-5 (river water) that contain traces of methylated As species. As speciation was in agreement with results previously reported and sums of all quantified species corresponded with the certified total As. The feasibility of HG-CT-AFS with FIGS was also demonstrated by the speciation analysis in microsamples of exfoliated bladder epithelial cells isolated from human urine. The results for the sums of trivalent and pentavalent As species corresponded well with the reference results obtained by HG-CT-ICPMS (inductively coupled plasma mass spectrometry).

Application of response function methodology for the simultaneous determination of potential fragrance allergens and preservatives in personal care products using micellar electrokinetic chromatography.

A micellar electrokinetic chromatography method was developed for determination of 15 suspected fragrance allergens and preservatives. The target compounds are widely used as ingredients in many personal care products, and all of them are included in the European Regulation concerning cosmetic products. The method was optimized by using a central composite experimental design and response surface methodology. A modified chromatographic response function was defined to weigh the terms in the response function adequately. After optimization of experimental conditions, a background electrolyte of 100 mM sodium dodecyl sulphate and 24 mM sodium tetraborate and pH 9.0 was selected for the separation of the analytes. The developed methodology was evaluated in terms of linearity, limits of detection and quantification, precision and accuracy, showing appropriate values (i.e., R (2) = ≥0.99 and accuracy of 89-115 %). Finally, applicability of the micellar electrokinetic chromatography method was assessed by successfully quantifying fragrance allergens and preservatives in commercial personal care products. The most commonly found analyte was linalool (48.3 % of samples) followed by benzoic acid (37.6 %). All samples contained at least one of the target compounds, thus confirming the ubiquity of fragrance allergens and preservatives in personal care products.

Evaluation of a rapid colorimetric field test to assess the effective life of long-lasting insecticide-treated mosquito nets in the Lao PDR.

BACKGROUND: Malaria morbidity and mortality have been significantly reduced through the proper use of insecticide-treated mosquito nets, but the extra protection afforded by the insecticide diminishes over time. The insecticide depletion rates vary according to location where wash frequency and wear are influenced by cultural habits as well as the availability of water. Monitoring of available insecticides on the net surface is essential for determining the effective life of the net. Therefore, a rapid and inexpensive colorimetric field test for cyanopyrethroids (Cyanopyrethroid Field Test or CFT) was used to measure surface levels of deltamethrin on insecticide-coated polyester nets (PowerNets™) in rural Lao PDR over a two-year period. METHODS: Net surface levels of deltamethrin were measured by wiping the net with filter paper and measuring the adsorbed deltamethrin using the CFT. A relationship between surface levels of deltamethrin and whole net levels was established by comparing results of the CFT with whole levels assayed by high-performance liquid chromatography (HPLC). An effective deltamethrin surface concentration (EC80) was determined by comparing mosquito mortality (WHO Cone Test) with CFT and HPLC results. Five positions (roof to bottom) on each of 23 matched nets were assayed for deltamethrin surface levels at 6, 12, and 24 months. Mosquito mortality assays (WHO Cone Tests) were performed on a subset of eleven 24-month old nets and compared with the proportion of failed nets as predicted by the CFT. RESULTS: At six months, the nets retained about 80% of the baseline (new net) levels of deltamethrin with no significant differences between net positions. At 12 months, ~15-40%, and at 24 months <10% of deltamethrin was retained on the nets, with significant differences appearing between positions. Results from the CFT show that 93% of the nets failed (deltamethrin surface levels

Colorimetric sensing strategy for mercury(II) and melamine utilizing cysteamine-modified gold nanoparticles.

A quantitative colorimetric sensing strategy utilizing cysteamine modified gold nanoparticles (CA-AuNPs) as reporters for Hg(2+) and melamine was demonstrated. Cysteamine is a cheap and commercially available aminothiol and is also the most important chelating ligand in coordination chemistry possessing the ability to coordinate to Hg(2+) and melamine. The terminal thiol group in cysteamine is used to bind to AuNPs and another terminal amine group is used as a colorimetric probe either for Hg(2+) or melamine. By adjusting the pH, protonation of cysteamine's terminal amine groups allows for tuning of the surface charge on the cysteamine-modified gold nanoparticles. At acidic pH, the CA-AuNPs are positively charged due to the protonated amine groups, which may electrostatically bind melamine resulting in aggregation of CA-AuNPs, while at alkaline pH, the amine groups are deprotonated, and if Hg(2+) is present, they may form an N-Hg(2+)-N structure to induce the aggregation of CA-AuNPs. The detection limits (S/N = 3) of Hg(2+) and melamine were 30 nM and 80 nM respectively, which were comparable with or even lower than those of other single analyte methods. The proposed sensing mechanisms, which are based on electrostatic attraction for melamine and the N-Hg(2+)-N structure for Hg(2+), were validated by zeta potential measurements. The facile one-step surface modification strategy for AuNPs is suitable for the effective analysis of large numbers of samples, which would open new opportunities for development of miniaturized Hg(2+) and melamine sensors.

Disposable screen-printed sensors for the electrochemical detection of TNT and DNT.

Due to the heightened level of national security currently prevalent due to the possibility of terrorist incidents, highly portable, miniaturised and sensitive monitoring devices for trace levels of injurious materials, such as explosives are now of the upmost importance. One method that offers a possible route for the development of a detection system for such species is via an electrochemical regime, coupled to the use of disposable sensor technology. Within this study, the use of carbon screen-printed sensors for the detection and analysis of the classical explosive trinitrotoluene (TNT) and the related dinitrotoluene (DNT) is described, with the eventual objective to develop an inexpensive, accurate and sensitive detection system for trace quantities of explosives in field settings. Commercially available screen-printed carbon sensors have been used as the base platform for this investigation and the electrochemistry of both TNT and DNT studied at these surfaces. Two reductive peaks and one oxidative peak were observed for both analytes. The best linear fits and sensitivities were obtained using the reductive peak at -0.72 V vs. Ag/AgCl. A linear range from 1 to 200 µM could be obtained for TNT and DNT in pH 7.0 phosphate buffer with limits of detection as low as 0.4 µM (TNT) and 0.7 µM (DNT). A second system which utilised the addition of the enzyme, nitroreductase, and the coenzyme, NADPH, into the solution matrix prior to electrochemical interrogations with screen-printed carbon electrodes was found to increase the resulting signal magnitude at the oxidation peak at +0.3 V, improving the performance of the sensor at these values.

[Survey of analytical works for drugs at emergency and critical care centers with high-performance instruments provided by the Ministry of Health and Welfare (at present: Ministry of Health, Labour, and Welfare) in fiscal 1998--continuation of survey with 2008 survey results as point of reference].

In a 2008 survey of the 73 emergency and critical care centers around the nation that were equipped with the drug and chemical analytical instrument provided by the Ministry of Welfare (currently the Ministry of Health, Labour, and Welfare) in 1998, 36 of those facilities were using the analytical instruments. Of these 36 facilities, a follow-up survey of the 17 facilities that recorded 50 or analyses per year. Responses were gained from 16 of the facilities and we learned that of those, 14 facilities (87.5%) were conducting analyses using the instrument. There was a positive mutual correlation between the annual number of cases of the 14 facilities conducting analyses with the instrument and the number of work hours. Depending on the instrument in use, average analytical instrument parts and maintenance expenses were roughly three million yen and consumables required a maximum three million yen for analysis of 51-200 cases per year. From this, we calculate that such expenses can be covered under the allowed budget for advanced emergency and critical care centers of 5,000 NHI points (1 point = 10 yen). We found there were few facilities using the instrument for all 15 of the toxic substances recommended for testing by the Japanese Society for Clinical Toxicology. There tended to be no use of the analytical instrument for compounds with no toxicology cases. However, flexible responses were noted at each facility in relation to frequently analyzed compounds. It is thought that a reevaluation of compounds subject to analysis is required.

Implementation of field detection devices for antimalarial quality screening in Lao PDR-A cost-effectiveness analysis.

Substandard and falsified (SF) antimalarials have devastating consequences including increased morbidity, mortality and economic losses. Portable medicine quality screening devices are increasingly available, but whether their use for the detection of SF antimalarials is cost-effective is not known. We evaluated the cost-effectiveness of introducing such devices in post-market surveillance in pharmacies in Laos, conservatively focusing on their outcome in detecting SF artemisinin-based combination therapies (ACTs). We simulated the deployment of six portable screening devices: two handheld near-infrared [MicroPHAZIR RX, NIR-S-G1], two handheld Raman [Progeny, TruScan RM]; one portable mid-infrared [4500a FTIR] spectrometers, and single-use disposable paper analytical devices [PADs]. We considered two scenarios with high and low levels of SF ACTs. Different sampling strategies in which medicine inspectors would test 1, 2, or 3 sample(s) of each brand of ACT were evaluated. Costs of inspection including device procurement, inspector time, reagents, reference testing, and replacement with genuine ACTs were estimated. Outcomes were measured as disability adjusted life years (DALYs) and incremental cost-effectiveness ratios were estimated for each device compared with a baseline of visual inspections alone. In the scenario with high levels of SF ACTs, all devices were cost-effective with a 1-sample strategy. In the scenario of low levels of SF ACTs, only four devices (MicroPHAZIR RX, 4500a FTIR, NIR-S-G1, and PADs) were cost-effective with a 1-sample strategy. In the multi-way comparative analysis, in both scenarios the NIR-S-G1 testing 2 samples was the most cost-effective option. Routine inspection of ACT quality using portable screening devices is likely to be cost-effective in the Laos context. This work should encourage policy-makers or regulators to further investigate investment in portable screening devices to detect SF medicines and reduce their associated undesired health and economic burdens.

Terbium-macrocycle complexes as chemical sensors: detection of an aspirin metabolite in urine using a salicylurate-specific receptor site.

Salicylurate (SU) is the major metabolite in urine of acetylsalicylic acid (aspirin) and can be used as a metric to monitor aspirin pharmacokinetics and as an indicator of appendicitis, anemia, and liver disease. Detection in urine and plasma currently requires solvent extraction or other sample handling prior to analysis. We present a simple method to quantify SU in urine via chelation to a terbium binary complex with the macrocycle 1,4,7,10-tetraazacyclododecane-1,7-bisacetate (DO2A). Binding of SU to form the [Tb(DO2A)(SU)](-) ternary complex triggers intense luminescence under UV excitation due to an absorbance-energy transfer-emission mechanism. Here we report characterization of the [Tb(DO2A)(SU)](-) ternary complex and application of this sensitized lanthanide luminescence method to quantify SU in urine samples following a low-dose aspirin regimen.