University of North Florida
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Stuart Chalk, Ph.D.
Department of Chemistry
University of North Florida
Phone: 1-904-620-1938
Fax: 1-904-620-3535
Email: schalk@unf.edu
Website: @unf

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Sample valve manipulation

Classification: Manifold component -> Sample valve manipulation

Citations 8

"Automated Simultaneous Determination Of Nitrate And Nitrite By Pre-valve Reduction Of Nitrate In A Flow Injection System"
Anal. Chim. Acta 1982 Volume 138, Issue 1 Pages 403-408
Jacobus F. Van Staden

Abstract: Nitrate is reduced to nitrite by using the pre-valve in-valve reduction technique prior to the sampling system. One loop of a two-position sampling valve is replaced by a copperised cadmium column. Nitrite from the samples as well as nitrite formed in the reduction procedure is sampled by a second valve and introduced into the flow system. The two sampling valves are synchronised in such a way that two peaks are obtained, one corresponding to the nitrate plus nitrite and the other to the nitrite only. The method is suitable for the simultaneous determination of nitrate and nitrite at a sampling rate of up to 72 determinations per hour with coefficients of variation better than 1.96% for nitrate and 0.83% for nitrite.
Nitrite Nitrate Environmental Spectrophotometry

"Recent Developments In Flow Injection Analysis: Gradient Techniques And Hydrodynamic Injection"
Anal. Chim. Acta 1983 Volume 145, Issue 1 Pages 1-15
J. Rika and E. H. Hansen

Abstract: Some of the most exciting recent advances in flow injection analysis (f.i.a.) have involved gradient techniques, which, founded on the key role of the dispersion controlled in space and time, are based on the feasibility of identifying and selecting reproducibly suitable sections of the dispersed sample zone and exploiting the specific concentrations at these points for analytical purposes. A comprehensive review of these techniques is given; in addition to the well established f.i.a. titrations and stopped-flow reaction rate procedures, methods have been developed for gradient dilution and calibration, gradient scanning, and selectivity evaluation. Finally, a detailed description of the most recent development within f.i.a., a hydrodynamic injector with no moving parts and zero dead volumes, is presente.
Spectrophotometry

"Microsample-filtering Device For Liquid Chromatography Or Flow Injection Analysis"
Anal. Chem. 1982 Volume 54, Issue 12 Pages 2129-2130
Wayne S. Gardner and Henry A. Vanderploeg

Abstract: A micro-filtering device was interfaced with a loop injector to filter small (1 mL) samples before liquid chromatography or flow-injection anal. The device has an active filtering area of 3 mm2 and an internal dead volume of 0.04 mL. The filter holder was designed for convenient filter changing between sample injections.
HPLC

"Comparison Of Sample Injection Systems For Flow Injection Analysis"
Anal. Chem. 1983 Volume 55, Issue 14 Pages 2461-2464
Jeffrey J. Harrow and Jiri Janata

Abstract: In flow-injection anal. the technol. for injection can be improved by using a system based on 4 solenoid pinch valves, which is very inexpensive, precise, and compatible with either pumps or gas propulsion. The system was evaluated and compared to other methods for sample injection.
pH Water Conductometry Electrode Field effect transistor

"Direct Liquid Sample Introduction For Flow Injection Analysis And Liquid Chromatography With Inductively Coupled Argon Plasma Spectrometric Detection"
Anal. Chem. 1984 Volume 56, Issue 2 Pages 289-292
Kimberly E. Lawrence, Gary W. Rice, and Velmer A. Fassel

Abstract: A micro-concentric nebulizer is described, use of which enables the solution from a flow injection analysis system, or the eluent from a HPLC column, to be analyzed directly by ICP-AES Detection limits by flow injection analysis - ICP ranged from 0.32 ppb for Mg to 140 ppb for Se, these being poorer, by factors ranging from 1.1 to 4.6, than those obtained by continuous nebulization with a cross-flow nebulizer. When Cr and As species were determined by HPLC - ICP, detection limits (ppm) were Cr(III) 0.44, Cr(VI) 0.43, As(V) 1.8 and As, as methanearsonic acid, 0.64. The very high linear velocity of the nebulizing gas and the excessive solvent loading were responsible for the poorer detection limits, and improvements to the nebulizer design are being investigated.
Arsenic(5+) Chromium(III) Chromium(VI) Magnesium methanearsonic acid Selenium HPLC Spectrophotometry

"Automated Prevalve Sample Filtration In Flow Injection Analysis. Determination Of Sulfate In Water Removing Suspended Solids And Color Before Sampling"
Fresenius J. Anal. Chem. 1982 Volume 312, Issue 5 Pages 438-440
Jacobus F. van Staden

Abstract: Suspended solids and the presence of organic substances and color are the main interferences in the turbidimetric spectrophotometric determination of sulphate at 420 nm in water. An automated flow-injection procedure is proposed in which these interferences are automatically removed by using an active carbon filter, which is incorporated in the flow system between the sampler and the sampling valve system. With this automated prevalve sample filter the proposed turbidimetric method gives the same results as a standard flow injection and an automated segmented method where the above mentioned interferences are manually removed prior to sampling. The method is applicable for the analysis of sulphate in surface, ground and domestic waters in the concentration range up to 200 mg/l at a sampling rate of up to 60 samples per hour with a coefficient of variation of better than 1%.
Sulfate Ground Surface Water Turbidimetry

"Rapid Sample Pretreatment And Analysis Using Automated FIA"
Am. Lab. 1982 Volume 14, Issue 1 Pages 56-68
Ranger, C.B.

Abstract: A review with 15 references. The use of flow injection analysis (FIA) for complex sample treatment functions, such as dilution, filtration, dialysis, distillation, extraction, and for development of reactions to determine a wide range of analytes in diverse sample matrixes is discussed. (SFS)

"Sample Pretreatment System For Atomic Absorption Using Flow Injection Analysis"
Lab. Pract. 1981 Volume 30, Issue 7 Pages 719-723
Mindel, B.D.;Karlberg, B.

Abstract: The use of flow injection analysis (FIA) techniques for the preparation of solutions prior to their aspiration into an atomic absorption spectrometer is described. FIA techniques can be used to process liquid samples automatically in order to bring the concentration. of the analyte and of interfering substances to the most suitable level for anal.; it can be used to reduce or increase sensitivity, and to handle samples with high dissolved solids. (SFS)
Metals Spectrophotometry