Jorge Sáiz

Portable Capillary Electrophoresis Instrument with Automated Injector and Contactless Conductivity Detection

A portable capillary electrophoresis instrument featuring an automated, robust, valve-based injection system was developed. This significantly facilitates operation in the field compared to previous injection approaches. These generally required delicate manual operations which are difficult to perform outside the laboratory environment. The novel system relies on pressurized air for solution delivery and a micromembrane pump for sample aspiration. Contactless conductivity detection was employed for its versatility and low power requirement. The instrument has a compact design, with all components arranged in a briefcase with dimensions of 45 × 35 × 15 cm (w × d × h) and a weight of about 8 kg. It can operate continuously for 9 h in the battery-powered mode. Depending on the task at hand, the injection system allows easy optimization for high separation efficiency, for fast separations, or for low limits of detection. To illustrate these features, the separation of four anions within 16 s is demonstrated as well as the determination of nitrite below 1 μM. The determination of phosphate at a sewage treatment plant was carried out to demonstrate a field application.

Simple semi-automated portable capillary electrophoresis instrument with contactless conductivity detection for the determination of β-agonists in pharmaceutical and pig-feed samples.

An inexpensive, robust and easy to use portable capillary electrophoresis instrument with miniaturized high-voltage capacitively coupled contactless conductivity detection was developed. The system utilizes pneumatic operation to manipulate the solutions for all flushing steps. The different operations, i.e. capillary flushing, interface rinsing, and electrophoretic separation, are easily activated by turning an electronic switch. To allow the analysis of samples with limited available volume, and to render the construction less complicated compared to a computer-controlled counterpart, sample injection is carried out hydrodynamically directly from the sample vial into the capillary by manual syphoning. The system is a well performing solution where the financial means for the highly expensive commercial instruments are not available and where the in-house construction of a sophisticated automated instrument is not possible due to limited mechanical and electronic workshop facilities and software programming expertise. For demonstration, the system was employed successfully for the determination of some β-agonists, namely salbutamol, metoprolol and ractopamine down to 0.7ppm in pharmaceutical and pig-feed sample matrices in Vietnam.

Instrumentino: An open-source modular Python framework for controlling Arduino based experimental instruments

Instrumentino is an open-source modular graphical user interface framework for controlling Arduino based experimental instruments. It expands the control capability of Arduino by allowing instruments builders to easily create a custom user interface program running on an attached personal computer. It enables the definition of operation sequences and their automated running without user intervention. Acquired experimental data and a usage log are automatically saved on the computer for further processing. The use of the programming language Python also allows easy extension. Complex devices, which are difficult to control using an Arduino, may be integrated as well by incorporating third party application programming interfaces into the Instrumentino framework

Determination of nitrogen mustard degradation products in water samples using a portable capillary electrophoresis instrument

In this work, a new purpose‐made portable CE instrument with a contactless conductivity detector was used for the determination of degradation products of nitrogen mustards in different water samples. The capillary was coated with poly(1‐vinylpyrrolidone‐co‐2‐dimethylaminoethyl methacrylate) to avoid analyte‐wall interactions. The coating procedure was studied to obtain the best repeatability of the migration time of the analytes. Four different coating procedures were compared; flushing the capillary with the copolymer at 100 psi for 2 min at 60°C provided the best RSD values (<4%). The analytical method was also optimized. The use of 20 mM of MES adjusted to pH 6.0 with His as running buffer allowed a good baseline separation of the three analytes in different water samples without matrix interferences. The method permitted the detection of the three degradation products down to 5 μM.

Concurrent determination of anions and cations in consumer fireworks with a portable dual-capillary electrophoresis system.

A new automated portable dual-channel capillary electrophoresis instrument was built and applied to the concurrent determination of cations and anions. The system uses a single buffer and hydrodynamic injection of the sample is performed autonomously. A novel engraved flow-cell interface is used at the injection ends of the capillaries allowing the autonomous operation of the system. The engraved flow-cell replaces traditionally used split injectors in purpose made capillary electrophoresis systems and makes the system design easier. A new software package with graphical user interface was employed to control the system, making its operation simple and increasing its versatility. The electrophoretic method was optimized to allow the baseline separation of 12 cations and anions commonly found in fireworks. The system was proven to be useful for the analysis of consumer fireworks, saving time and expenses compared to separate analyses for anions and cations. This is the first time that cationic and anionic compositions of fireworks are investigated together. The analysis of samples revealed several inaccuracies between the declared compositions for the fireworks and the obtained results, which could be attributed to cross-contamination during their manufacture or to a transfer between other components of the pyrotechnic item. The presence of certain unexpected peaks, however, had no apparent reason and might represent an irregularity in the manufacture of some devices.

Automated dual capillary electrophoresis system with hydrodynamic injection for the concurrent determination of cations and anions.

The capillary electrophoresis instrument developed for the concurrent determination of cations and anions features two separate capillaries and individual detectors to allow independent optimization for each group of ions. The capillaries are joined in a common injector block. The sample is drawn into the injector with a small membrane pump and automated simultaneous injection into both capillaries is achieved by pressurization of the fluid with compressed air. Flushing of the injector and of the capillaries with the background electrolyte is also carried out automatically by the same means. The buffer consisted of 12mM histidine and 2mM 18-crown-6 adjusted to pH 4 with acetic acid and was suitable for the contactless conductivity detection employed. The system was optimized for the determination of cationic NH4(+) and anionic NO3(-) and NO2(-), and linear calibration curves from about 20μM up to about 1.5mM were obtained for these ions. In a test run over 8h, the reproducibility for the peak areas was within ±7%. For demonstration, the instrument was successfully applied to the concurrent monitoring of the concentrations of the three ions during the biological removal of ammonium from contaminated groundwater in a sequencing batch reactor, where NO3(-) and NO2(-) are formed as intermediate products.

Rapid determination of scopolamine in evidence of recreational and predatory use

In recent years, scopolamine has become a drug of common use for recreational and predatory purposes and several ways of administration have been devised. A method for the rapid analysis of suspicious samples was developed, using a portable capillary electrophoresis with contactless conductivity detection. The method allows the separation of scopolamine from atropine which has a similar structure and is present along with scopolamine in some samples. The method was demonstrated to be useful for the fast analysis of several types of evidential items which have recently been reported to have been abused with fatal consequences or employed for criminal purposes. An infusion of Datura stramonium L., in which scopolamine and atropine naturally coexist, was analyzed for being frequently consumed for recreational purposes. A spiked moisturizing cream and six spiked alcoholic beverages were also analyzed. In spite of the complexity of the specimens, the sample pre-treatment methods developed were simple and fast.

Screening determination of pharmaceutical pollutants in different water matrices using dual-channel capillary electrophoresis coupled with contactless conductivity detection

In this study, the employment of purpose-made dual-channel compact capillary electrophoresis (CE) instrument with capacitively coupled contactless conductivity detection (C(4)D) as a simple and inexpensive solution for screening determination of various pharmaceutical pollutants frequently occurring in surface water and hospital wastewater in Hanoi, Vietnam is reported. Five negatively charged pharmaceutically active compounds, namely ibuprofen, diclofenac, bezafibrate, ketoprofen and mefenamic acid were determined using the first channel whereas three positively charged ones, namely diphenhydramine, metoprolol and atenolol were determined with the second channel of the CE-C(4)D instrument. Two different background electrolytes (BGEs) were used in these two CE channels independently. The best detection limits achieved were in the range of 0.2-0.8mg/L without sample pre-concentration. Enrichment factors up to 200 were obtainable with the inclusion of a solid phase extraction step. Good agreement between results obtained from CE-C(4)D and those with the standard confirmation method (HPLC-DAD) was achieved, with correlation coefficients higher than 0.98.

Simultaneous separation of cations and anions in capillary electrophoresis - recent applications

In this review, the simultaneous determination of anionic and cationic species in capillary electrophoresis for different applications such as water quality analysis, medical diagnosis, pharmaceutical analysis, forensic science and food control is discussed. The simplicity and electronic nature of capillary electrophoresis allow the easy modification of custom made set-ups in order to realise various techniques for the simultaneous separation of different ionic analytes. As a continuation of our earlier review, in which the details of the working principles were described, this report is focussed on the applications of the simultaneous electrokinetic separation methods reported during the last five years (2011–2015).

Screening determination of four amphetamine-type drugs in street-grade illegal tablets and urine samples by portable capillary electrophoresis with contactless conductivity detection

A simple and inexpensive method for the identification of four substituted amphetamines, namely, 3,4-methylenedioxy methamphetamine (MDMA), methamphetamine (MA), 3,4-methylenedioxy amphetamine (MDA) and 3,4-methylenedioxy-N-ethylamphetamine (MDEA) was developed using an in-house constructed semi-automated portable capillary electrophoresis instrument (CE) with capacitively coupled contactless conductivity detection (C(4)D). Arginine 10mM adjusted to pH4.5 with acetic acid was found to be the optimal background electrolyte for the CE-C(4)D determination of these compounds. The best detection limits achieved with and without a sample preconcentration process were 10ppb and 500ppb, respectively. Substituted amphetamines were found in different seized illicit club drug tablets and urine samples collected from different suspected users. Good agreement between results from CE-C(4)D and those with the confirmation method (GC-MS) was achieved, with correlation coefficients for the two pairs of data of more than 0.99.