Study on the interrelated effects of capillary diameter, background electrolyte concentration, and flow rate in pressure assisted capillary electrophoresis with contactless conductivity detection

Portable capillary electrophoresis coupled with swab-based extraction device for cleaning validation in pharmaceutical facilities

All pharmaceutical manufacturers are required to verify that their production equipment is free from contaminants. Here, we report the capability of a fully automated portable capillary electrophoresis instrument with an integrated sample swab extraction - the Grey Scan ETD-100 - for the detection of pharmaceutical residues on surfaces of manufacturing equipment. Lidocaine was used as a model compound and could be recovered from a surface by swabbing, extracted from the swab, and analysed within 1 min. The recovery of lidocaine from a stainless-steel coupon was 81.3 %, with a LOD of 0.13 µg/swab. This fast, sensitive, and simple method implemented on a user-friendly portable CE instrument without the need for manual sample pre-treatment provides the possibility for on-site rapid determination of equipment cleanliness in the pharmaceutical industry.

Low-cost automated capillary electrophoresis instrument assembled from commercially available parts

A CE instrument that can be assembled from commercially available components with minimal construction effort is described. Except for the electronic control circuitry no specially made parts are required. It is based on a flexible design of microfluidic, electropneumatic, and electronic sections and different configurations can easily be implemented. Automated injection into the capillary is performed hydrodynamically by the application of a pressure for a controlled length of time. The performance of the device was tested with a contactless conductivity detector by separating different metal ions. In addition, nine metal cations related to the quality of honey were separated in 2.3 min and four honey samples were analysed quantitatively to demonstrate the applicability of the method.

Low-cost and versatile analytical tool with purpose-made capillary electrophoresis coupled to contactless conductivity detection: Application to antibiotics quality control in Vietnam

In this study, the development of our purpose-made capacitively coupled contactless conductivity detection (C⁴ D) for CE is reported. These systems have been employed as a simple, versatile, and cost-effective analytical tool. CE-C⁴ D devices, whose principle is based on the control of the ion movements under an electrical field, can be constructed even with a modest financial budget and limited infrastructure. A featured application was developed for quality control of antimicrobial drugs using CE-C⁴ D, with most recent work on determination of aminoglycoside and glycopeptide antibiotics being communicated. For aminoglycosides, the development of CE-C⁴ D methods was adapted to two categories. The first one includes drugs (liquid or powder form) for intravenous injection, containing either amikacin, streptomycin, kanamycin A, or kanamycin B. The second one covers drugs for eye drops (liquid or ointment form), containing either neomycin, tobramycin, or polymyxin. The CE-C⁴ D method development was also made for determination of some popular glycopeptide antibiotics in Vietnam, including vancomycin and teicoplanin. The best detection limit achieved using the developed CE-C⁴ D methods was 0.5 mg/L. Good agreement between results from CE-C⁴ D and the confirmation method (HPLC- Photometric Diode Array ) was achieved, with their result deviations less than 8% and 13% for aminoglycoside and glycopeptide antibiotics, respectively.

Determination of carbapenem antibiotics using a purpose-made capillary electrophoresis instrument with contactless conductivity detection

In this study, the employment of a purpose-made capillary electrophoresis (CE) instrument with capacitively coupled contactless conductivity detection (C⁴D) as a simple and cost-effective approach for simultaneous determination of different carbapenem antibiotics is reported. The developed CE-C⁴D approach was for the first time applied for quality control of various pharmaceutical formulations in Vietnam, as well as for therapeutic monitoring of these antibiotics in plasma samples from patients under intensive care. Four of the most popular carbapenems in Vietnam, doripenem, meropenem, imipenem and ertapenem, were determined using an electrolyte composed of 10 mM Tris adjusted to pH 8.0 with acetic acid. The best detection limits achieved using the developed CE-C⁴D method were 0.36 mg/L and 0.45 mg/L for pharmaceutical and plasma samples, respectively. Good agreement between results from CE-C⁴D and the confirmation method (HPLC-PDA) was achieved, with a coefficient of determination (r²) for the two pairs of data of 0.9967.

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.

In-house-made capillary electrophoresis instruments coupled with contactless conductivity detection as a simple and inexpensive solution for water analysis: a case study in Vietnam

A simple and inexpensive method for the determination of various ionic species in different water matrices is discussed in this study. The approach is based on the employment of in-house-made capillary electrophoresis (CE) instruments with capacitively coupled contactless conductivity detection (C(4)D), which can be realized even when only a modest financial budget and limited expertise are available. Advantageous features and considerations of these instruments are detailed following their pilot deployment in Vietnam. Different categories of ionic species, namely major inorganic cations (K(+), Na(+), Ca(2+), Mg(2+), and NH4(+)) and major inorganic anions (Cl(-), NO3(-), NO2(-), SO4(2-), and phosphate), in different water matrices in Vietnam were determined using these in-house fabricated instruments. Inorganic trivalent arsenic (As(iii)), which is the most abundant form of arsenic in reducing groundwater, was determined by CE-C(4)D. The effect of some interfering ions in groundwater on the analytical performance was investigated and is highlighted. The results from in-house-made CE-C(4)D-instruments were cross-checked with those obtained using the standard methods (AAS, AES, UV and IC), with correlation coefficients r(2) ≥ 0.9 and deviations from the referenced results less than 15%.

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.

Impact of Taylor-Aris diffusivity on analyte and system zone dispersion in CZE assessed by computer simulation and experimental validation

Application of pressure-driven laminar flow has an impact on zone and boundary dispersion in open tubular CE. The GENTRANS dynamic simulator for electrophoresis was extended with Taylor-Aris diffusivity which accounts for dispersion due to the parabolic flow profile associated with pressure-driven flow. Effective diffusivity of analyte and system zones as functions of the capillary diameter and the amount of flow in comparison to molecular diffusion alone were studied for configurations with concomitant action of imposed hydrodynamic flow and electroosmosis. For selected examples under realistic experimental conditions, simulation data are compared with those monitored experimentally using modular CE setups featuring both capacitively coupled contactless conductivity and UV absorbance detection along a 50 μm id fused-silica capillary of 90 cm total length. The data presented indicate that inclusion of flow profile based Taylor-Aris diffusivity provides realistic simulation data for analyte and system peaks, particularly those monitored in CE with conductivity detection.

Effects of ion pairing on the capillary electrophoretic separation and ultraviolet-absorption detection of quaternary ammonium cations using meso-octamethylcalix[4]pyrrole as the background electrolyte additive

Five quaternary ammonium cations, including tetramethylammonium, tetraethylammonium, hexadecyltrimethylammonium, benzyltrimethylammonium, and 1-butyl-3-methylimidazolium, have been separated by capillary electrophoresis. A direct ultraviolet method has been achieved when tetrabutylammonium fluoride was the background electrolyte and meso-octamethylcalix[4]pyrrole was the background electrolyte additive. The ultraviolet spectra of meso-octamethylcalix[4]pyrrole and cation mixtures showed that redshifts can be attributed to the size of cations, and the maximum absorption wavelength shifted from 218 to 230 nm when tetrabutylammonium cation was substituted with tetramethylammonium cation or tetraethylammonium cation. Conductivity measurements were performed to evaluate the ion-pairing effect of tetrabutylammonium fluoride in a mixture of acetonitrile/ethanol (80:20, v/v), and the ion-pairing formation constant, Kip, was calculated (Kip = 14.8 ± 0.3 L/mol) using the Fuoss extended model. Ion pairing also occurs between cations of the analytes and counterion, a fluoride complex of meso-octamethylcalix[4]pyrrole. The tetramethylammonium cations associate more strongly with this counterion than the tetraethylammonium cation that contributes to the change of selectivity in capillary electrophoresis separation. The effective mobilities of the cations with trimethyl groups, such as tetramethylammonium cation, benzyltrimethylammonium cation, and hexadecyltrimethylammonium cation, decreased faster than others with the increase of meso-octamethylcalix[4]pyrrole concentration, highlighting the fact that the ion-pairing effect played an important role in this method.