Ultraviolet Photometric Detection Research Articles

Open-Source Absorbance Detector with Multiple Deep UV-LEDs for On-Capillary Multiwavelength Detection at a Single Point.

On-capillary ultraviolet photometric detection (UV-PD) in a multiwavelength mode provides comprehensive analytical information. However, achieving single-point multiwavelength UV-PD for capillary-scale instruments typically requires high-cost and complex devices. This study presents the development of a cost-effective, open-source absorbance detector for on-capillary multiwavelength detection. The detector employs three deep UV light-emitting diodes emitting at 235, 255, and 278 nm as light sources, each coupled with its own photodetector for independent detection channels. The components are housed using 3D-printed parts, with an Arduino board used for data acquisition. Three individual optical paths, formed by three slits (60 μm width ×1 mm length), surround the measured capillary and converge at the same detection point. The detector demonstrates simultaneous multiwavelength detection of medicines for both HPLC and CE. This development represents an advancement in portable, low-cost analytical instrumentation, with broad implications for various fields of application.

Direct Measurement of Trace Elemental Mercury in Hydrocarbon Matrices by Gas Chromatography with Ultraviolet Photometric Detection.

We introduce a technique for the direct measurement of elemental mercury in light hydrocarbons such as natural gas. We determined elemental mercury at the parts-per-trillion level with high precision [<3% RSD (n = 20 manual injection)] using gas chromatography with ultraviolet photometric detection (GC-UV) at 254 nm. Our approach requires a small sample volume (1 mL) and does not rely on any form of sample preconcentration. The GC-UV separation employs an inert divinylbenzene porous layer open tubular column set to separate mercury from other components in the sample matrix. We incorporated a 10-port gas-sampling valve in the GC-UV system, which enables automated sampling, as well as back flushing capability to enhance system cleanliness and sample throughput. Total analysis time is <2 min, and the procedure is linear over a range of 2-83 μg/m(3) [correlation coefficient of R(2) = 0.998] with a measured recovery of >98% over this range.

Determination of the spectrum of low molecular mass organic acids in urine by capillary electrophoresis with contactless conductivity and ultraviolet photometric detection—An efficient tool for monitoring of inborn metabolic disorders

A mixture of 29 organic acids (OAs) occurring in urine was analyzed by capillary electrophoresis (CE) with capacitively coupled contactless conductivity detection (C 4D) and UV photometric detection. The optimized analytical system involved a 100 cm long polyacrylamide-coated capillary (50 μm i.d.) and the background electrolyte of 20 mM 2-morpholinoethanesulfonic acid (MES)/NaOH + 10% (v/v) methanol, pH 6.0 (pH is related to the 20 mM MES/NaOH buffer in water). The LOD values obtained by C 4D for the OAs which do not absorb UV radiation range from 0.6 μM (oxalic acid) to 6.8 μM (pyruvic acid); those obtained by UV photometry for the remaining OAs range from 2.9 μM (5-hydroxy-3-indoleacetic acid) to 10.2 μM (uric acid). The repeatability of the procedure developed is characterized by the coefficients of variation, which vary between 0.3% (tartaric acid) and 0.6% (5-hydroxy-3-indoleacetic acid) for the migration time and between 1.3% (tartaric acid) and 3.5% (lactic acid) for the peak area. The procedure permitted quantitation of 20 OAs in a real urine sample and was applied to monitoring of the occurrence of the inborn metabolic fault of methylmalonic aciduria.

Miniaturized capillary electrophoresis system with ultraviolet photometric detection combined with flow injection sample introduction using a modified falling-drop interface

Miniaturized capillary electrophoresis system with ultraviolet photometric detection combined with flow injection sample introduction using a modified falling-drop interface

Miniaturized capillary electrophoresis system with ultraviolet photometric detection combined with flow injection sample introduction using a modified falling-drop interface

A miniaturized capillary electrophoresis (CE) system with UV-Vis detection was coupled to a flow injection (FI) system for achieving high throughput continuous sample introduction. The cassette of a commercial CE instrument was modified to hold a 6.5 cm long silica capillary and a flow-through waste reservoir. The cassette was inserted into the flow-cell chamber of a commercial UV detector, with the light beam focused on the capillary and collected by two ball lenses on the cassette. The capillary inlet, left outside the cassette and detector, was positioned on the top of a vertical 3.5 mm diameter glass rod, in close contact with an electrode. Samples injected through the FI system dropped freely on top of the pillar, covering the capillary inlet and electrode. Continuous sample introduction was achieved for CE separations under non-interrupted separation voltage, which was isolated from the FI system through the discontinuity of droplets. The newly developed interface and UV detection system was used for fast separation of sulphamethoxazole (SMZ) and trimethoprim (TMP) in sulphatrim tablets, achieving a high throughput of over 48 h −1, and a low carryover of 2%. Separation efficiencies of 8 μm plate height and detection limits of 1.0 mg l −1 for SMZ and 0.5 mg l −1 (3 σ) for TMP were obtained.

Concentration of nonylphenol and its polyethoxylated derivatives by polymer-mediated extraction

Polymer-mediated extraction based on thermoresponsive precipitation of poly( N-isopropylacrylamide) [PNIPAAm] was applied to the concentration of amphiphilic compounds, nonylphenyl polyethoxylates (NPnEOs), in water. Among these nonionic surfactants, NPnEOs possessing the number, n, of ethoxy unit less than 5 were quantitatively recovered in polymer precipitates when a 0.100-g portion of PNIPAAm was used for a 10 ml sample solution. Torelance limit (30 ppm) against a typical industrial anionic surfactant, sodium dodecylsulfate, strongly suggests the potential to use the present method for practical purposes. After preconcentration, trace nonylphenol and mono-ethoxylated nonylphenol (ppb-level) in a river water sample were successfully determined by high-performance liquid chromatography with ultra-violet photometric detection.

Micelle-mediated extraction for concentrating hydrophobic organic compounds

An extraction method based on polymer-induced phase separation of aqueous micellar solutions of octyl-β- d-thioglucoside (OTG) was assessed for concentrating hydrophobic analytes. Various hydrophobic compounds such as polycyclicaromatic hydrocarbons, alkylbenzenes, alkylphenols, chlorobenzenes, chlorophenols, phthalic esters, pesticides, and steroid hormones could be efficiently concentrated into a small volume of surfactant-rich phase, while hydrophilic matrix components remained in the bulk aqueous phase. The surfactant-rich phase containing concentrated OTG could be directly introduced into the hygro-organic mobile phase of high-performance liquid chromatography with ultra-violet photometric detection. The application of this method greatly enhanced the signal intensity in the chromatogram while reducing the interference of matrix components.

Simultaneous determination of cotinine and trans-3′-hydroxycotinine in human serum by high-performance liquid chromatography

A high-performance liquid chromatographic method with ultraviolet photometric detection has been developed for the quantitation of cotinine and trans-3′-hydroxycotinine in human serum. A solid-phase extraction procedure was performed for the analytes and the internal standard, N-ethylnorcotinine, before chromatography. The use of a 30-cm reversed-phase column and a mobile phase of water—methanol—0.1 M sodium acetate—acetonitrile (67:24.5:6.5:2, v/v), pH 4.3, prevented the co-elution of caffeine with cotinine. The limit of quantitation observed with this method was 5 ng/ml for both cotinine and trans-3′-hydroxycotinine. The present method proved useful for the determination of serum levels of these metabolites, correlating with nicotine daily intake.

Elimination of caffeine interference in high-performance liquid chromatographic determination of cotinine in human plasma

A high-performance liquid chromatographic method with ultraviolet photometric detection for the determination of cotinine in human plasma was described. The use of a 30-cm reversed-phase column and of a mobile phase consisting of water—methanol—0.1 M sodium acetate—acetonitrile (72:21:5.6:1.4, v/v), pH 4.1, eliminated caffeine interference. A simplified solid-phase extraction procedure was also performed for plasma samples.

Isotachophoretic analyser equipped with a scanning ultraviolet photometric detection system

An isotachophoretic analyser with a scanning ultraviolet (UV) photometric detection system was constructed in order to study separation processes. A fused-silica capillary (I.D. 0.53 mm, O.D. 0.66 mm) was scanned over a length of 32 cm with an assembly of a UV lamp and a detector. The assembly was driven by a linear head with a stepping motor. One scanning cycle took 7.027 s and 5333 photometric signals (a UV position spectrum) were acquired. The practical resolution was 0.15 mm. The detection limit of picric acid was 20 pmol. Using the apparatus, the separation of a four-component mixture (SPADNS, monochloroacetic acid, picric acid and acetic acid) was studied using different electrolyte systems and the effect of the pH of leading electrolyte on the separation efficiency is briefly discussed.

High-performance liquid chromatographic determination of some polar phospholipids in serum

The experimental conditions have been optimized for high-performance liquid chromatographic determination of phosphatidylethanolamine (PE), phosphatidylcholine (PC) and sphingomyelin (SM) in serum. The phospholipids are separated on a silica gel column, using a mobile phase of acetonitrile-methanol-water (100:10:18, v/v), with ultraviolet photometric detection at 200 nm. The limit of detection was 0.2 μg (in 20 μl) for natural phospholipids and 2.5 μg for synthetic phospholipids; the relative standard deviation was ca. 5%. An alternative detection is tensammetry at a mercury electrode, at a potential of -1.8 V, with an a.c. current frequency of 60 Hz and an amplitude of 20 mV. The tensammetric detection has an advantage in its independence of the structure of the phospholipids. In measurements without a column (flow-injection analysis), the tensammetric detection also yields a somewhat lower limit of detection than photometry (0.15 μg per 20 μl), but this value increases more than ten times in chromatographic detection. The precision is poorer and is more susceptible to interferences. The method was applied to the determination of the above substances in the blood of obese children, as a function of physical stress and spa treatment. It was shown that physical exercise causes a decrease in the contents of PE and PC in the patients. On the other hand, the spa treatment has no pronounced effect on the phospholipid content in the blood.

High-performance liquid chromatography of s-triazines and their degradation products using ultraviolet photometric and amperometric detection

The chromatographic behaviour of eighteen s-triazine derivatives has been studied in a reversed-phase system with a Separon SIC 18 stationary phase and a mobile phase of aqueous sodium dihydrogenphosphate and methanol. The dependences of the capacity factors on the methanol content, the pH and the ionic strength have been obtained. Ultraviolet photometric detection can generally be used whereas amperometric detection with a carbon-fibre array electrode is useful for selective detection of is-triazine hydroxy derivatives, but with a sensitivity poorer than that of photometric detection. The method has been applied to a study of the photolysis of s-triazines and the effect of the substituents and the pH on the photolysis rate.

A new technique for collection, concentration and determination of gaseous tropospheric formaldehyde

This article describes an improved technique for making in situ measurements of gaseous tropospheric formaldehyde (CH 2O). The new technique is based on nebulization/reflux principles that have proved very effective in quantitatively scrubbing water soluble trace gases (e.g. CH 2O) into aqueous mediums, which are subsequently analyzed. Atmospheric formaldehyde extractions and analyses have been performed with the nebulization/reflux concentrator using an acidified dinitrophenylhydrazine solution that indicate that quantitative analysis of CH 2O at global background levels (∼ 0.1 ppbv) is feasible with 20-min extractions. Analysis of CH 2O, once concentrated, is accomplished using high performance liquid chromatography (HPLC) with ultraviolet photometric detection. The CH 2O-hydrazone derivative, produced by the reaction of 2,4-dinitrophenylhydrazine in H 2SO 4 acidified aqueous solution, is detected as CH 2O.

Monitoring of aromatic amines by hplc with electrochemical detection: Comparison of methods for destruction of carcinogenic aromatic amines in laboratory wastes

A new chemical method for destruction of carcinogenic aromatic amines in laboratory wastes has been developed. The method is based on enzymatic oxidation of the amines in solution (with hydrogen peroxide and horseradish peroxidase), followed by oxidation of the solid residues with permanganate in sulphuric acid medium. To monitor the efficiency of destruction, a reversed-phase HPLC system has been developed, with voltammetric detection with a carbon-fibre detector, which is substantially more sensitive (detection limits from a few ng down to a few pg of amine) than the commonly used ultraviolet photometric detection. It has been demonstrated that the proposed method of destruction is highly efficient (≫99.8% destruction).

Improvement of ion chromatography with ultraviolet photometric detection and comparison with conductivity detection for the determination of serum cations

Studies were made of the anlaytical conditions required for indirect photometric ion chromatography using ultraviolet photometric detection (UV method) for the determination of serum cations following a previously developed serum pre-treatment. The sensitivities of the conductivity detection (CD) and UV methods and the amounts of serum cations determined by both methods were compared. Attempts to improve the sensitivity of the conventional UV method are reported. It was found that the mobile phase previously reported by Small and Miller showed no quantitative response when more than 4 m M copper (II) sulphate pentahydrate was used. As a result, there was no significant difference in the amounts of serum cations shown by the CD and UV methods. However, by adding 0.5–5 m M cobalt(II) sulphate heptahydrate, nickel(II) sulphate hexahydrate, zinc(II) sulphate heptahydrate or cobalt(II) diammonium sulphate hexahydrate to 0.5–1.5 m M copper(II) sulphate pentahydrate, higher sensitivity and a quantitative response were attained.

Determination of free and conjugated bile acidsas ultraviolet-absorbing lon pairs by reverse-phase high-performance liquid chromatography

A method for the determination of free and conjugated bile acids as uv-absorbing ion pairs was developed. Ultraviolet photometric detection was more sensitive than differential refractometer detection. Improved resolution of positional isomers was also achieved. Distinctions were made between free and conjugated bile acids and between tauro- and glyco-conjugated bile acids. This was accomplished by adjusting the pH of the mobile phase to selectively form ion pairs.