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NQS

About: NQS is a research topic. Over the lifetime, 337 publications have been published within this topic receiving 4226 citations.


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TL;DR: In this paper, a simple spectrophotometric method for determination of hydrogen sulfide in wastewater and hot spring samples was developed based on the reaction between hydrogen sulfides and sodium 1,2-naphthoquinone-4-sulfonate (NQS).
Abstract: A simple spectrophotometric method for determination of hydrogen sulfide in wastewater and hot spring samples was developed. The method is based on the reaction between hydrogen sulfide and sodium 1,2-naphthoquinone-4-sulfonate (NQS). The effect of various experimental factors on the reaction between hydrogen sulfide and NQS was investigated and optimized using central composite design. The optimal values of the factors were 5.00 × 10−4 mol L−1 for concentration of NQS and 1.00 × 10−2 mol L−1 for concentration of hydrochloric acid. The wavelength of the maximum absorption of the reaction product was 320 nm. Constructed calibration curve for hydrogen sulfide determination was linear in the range of 0.5–20.0 mg L−1 with the detection limit of 0.16 mg L−1. The method was free from interferences. Percent relative errors below 2 % were obtained for determination of hydrogen sulfide in environmental samples.

12 citations

Journal ArticleDOI
TL;DR: In this article, the authors derived the governing equations and the associated boundary conditions which describe the small-signal minority carrier transport in the quasi-neutral base region at arbitrary injection levels.
Abstract: In this paper a study of small-signal operation of bipolar transistors is presented. Firstly, we derive the governing equations and the associated boundary conditions which describe the small-signal minority carrier transport in the quasi-neutral base region at arbitrary injection levels. Analytical solutions of the transport equations are then discussed. A consequence of the linearity of the transport equations is that the minority carrier currents at the device terminals can be expressed in terms of infinite polynomials of the complex variable. It is then shown that all the hitherto proposed non-quasi-static (NQS) models can be simply obtained by different approximations of the general current expressions. As a consequence, the differences between the various models are clarified, and models previously developed for the low-injection regime are extended to high-injection conditions. The dependence of fundamental model parameters such as the transit time, the partitioning factor, etc., on the injection level is analyzed in detail, and a simple analytical formulation is proposed. Limitations of previous approaches are outlined. Finally, selected NQS models are compared.

12 citations

Journal ArticleDOI
TL;DR: In this article, a simple and sensitive spectrophotometric method for the quantitative analysis of pyri- methamine (PYM) in pharmaceutical formulations has been described, which is based on the formation of colored product between PYM and 1,2-naphthoquinone-4-sulfonate (NQS) at 60 nm.

12 citations

01 Jan 2014
TL;DR: In this article, a simple, rapid and sensitive spectrofluorimertic method was developed for the determination of certain proton pump inhibitors (PPIs) belonging to benzimidazole drugs omeprazole (OMZ), RAB, PAN and LAN.
Abstract: A simple, rapid and sensitive spectrofluorimertic method was developed for the determination of certain proton pump inhibitors (PPIs) belonging to benzimidazole drugs omeprazole (OMZ), rabeprazole (RAB), pantoprazole (PAN) and lansoprazole (LAN). The method depends on coupling with sodium 1, 2-naphthoquinone-4-sulphonate (NQS) in presence of methanolic solution of iodine and alkaline medium to yield an intensely fluorescent derivative measured at λ exc. = 340 nm and λ em. = 480 nm. A linear relationship was achieved between measured relative fluorescence intensity and concentration of each of the studied drug in the ranges 5-60, 10-80, 10-65 and 10-85 ng ml -1 for OMZ, LAN, PAN and RAB, respectively with good correlation coefficients. The limits of detection and quantification, intra-day, inter-day precision, and accuracy of the method have been evaluated. The proposed method was successfully applied to the assay of the studied PPIs in dosage forms and the results were statistically agree well with those of reported methods.

12 citations

Journal ArticleDOI
TL;DR: In this paper, a spectrophotometric method based on the reaction of prazosin hydrochloride with 1,2-naphthoquinone-4-sulphonic acid (NQS) via its amino group on the side chain attached to the 2-position of the dihydropyridine ring is presented.
Abstract: Prazosin (1) 1-(4-amino-6,7-dimethoxy-2-quizanolinyl)-4-(2-furanylcarbonyl) piperazine is an antihypertensive and a potent vasodilatory agent in the quinazoline family and also has been found to be value in the treatment of heart failure. The drug and its formulations are official in the British Pharmacopeia and United States Pharmacopoeia. There are fluorimetric, UV spectrophotometric, GLC, TLC, voltametric, and differential pulse polarographic13−15 methods in the literature for the assay of the drug. The official USP XXII method uses a HPLC technique for the determination of 1 in capsules . There is no conventional method for the tablets. HPLC is widely used for the assay of the drug in body fluids16−18 and biological samples. There is only one visible-range spectrophotometric method in the literature, and so a simple, time-saving and sensitive method for the assay of prazosin hydrochloride in pharmaceuticals and bulk sample formulations is needed. This paper describes a spectrophotometric method based on the reaction of prazosin hydrochloride with 1,2-naphthoquinone-4-sulphonic acid (NQS) via its amino group on the side chain attached to the 2-position of the dihydropyridine ring. NQS was previously reported to be a sensitive colour reagent for several primary and secondary amines21−23. ∗Corresponding author

11 citations


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Performance
Metrics
No. of papers in the topic in previous years
YearPapers
20221
202114
20208
201912
20185
201715