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In mineral processing, iron oxidation species formed on the mineral surface play a dominant role in depressing mineral flotation and must be monitored. Current analytical methods rely on off-line sample preparation followed by conventional analytical techniques, which are labour intensive and time delayed. This paper reports the successful application of an open microfluidic chip for real-time continuous monitoring of ethylenediaminetetra acetic acid (EDTA) extractable iron (derived from iron oxidation species) in mineral slurries. A detailed mineralogical study of the mineral ore before and after leaching by EDTA has been undertaken to understand the leaching behaviour of the EDTA-slurry extraction system, showing good agreement with solution analysis. Refereed/Peer-reviewed

High solids content complicates in situ analysis of chemical processing, biological suspensions, and environmental streams. In most cases, analytical methods require at least one pre‐treatment step of a small volume of sample before a particle‐free fluid can be analyzed. We have developed a continuous in situ sampler that can “sip” particle‐free solution from a turbulent high solids content stream (a slurry). An open microfluidic chip with an extended slit opening shields the internal laminar flow from the turbulence outside. Unlike other open chips, our chip does not require close proximity to a solid surface and operates in turbulent environments for hours without maintenance. Two applications are demonstrated: monitoring iron (III) in a stirred slurry of mixed ore particles at high solids loading (4%wt) and paracetamol tablet dissolution profiles for two different formulations. Refereed/Peer-reviewed

Removal of organic solvent from sample extracts is required before analysis by reversed phase HPLC to preserve chromatographic performance and allow for bigger injection volumes, boosting sensitivity. Herein, an automated on-line extraction evaporation procedure is integrated with HPLC analysis. The evaporation occurs inside a 200 μm microfluidic channel confined by a vapor permeable membrane. A feedback control algorithm regulates evaporation rate keeping the output flow rate constant. The evaporation process across this membrane was firstly characterized with water/solvent mixtures showing organic solvent removal capabilities. This system allowed continuous methanol, ethanol and acetonitrile removal from samples containing up to 80% organic solvent. An evaporative injection procedure was developed demonstrating the use of the device for fully integrated extract reconstitution coupled to HPLC analysis, applied to analysis of the antibiotic chloramphenicol in milk samples. Sample reconstitution and collection was performed in less than 10 min and can be executed simultaneously to HPLC analysis of the previous sample in a routine workflow, thus having minimal impact on the total sample analysis time when run in a sequence. Refereed/Peer-reviewed

One of the most cited limitations of capillary and microchip electrophoresis is the poor sensitivity. This review continues to update this series of biannual reviews, first published in Electrophoresis in 2007, on developments in the field of online/in‐line concentration methods in capillaries and microchips, covering the period July 2016–June 2018. It includes developments in the field of stacking, covering all methods from field‐amplified sample stacking and large‐volume sample stacking, through to isotachophoresis, dynamic pH junction, and sweeping. Attention is also given to online or in‐line extraction methods that have been used for electrophoresis. Refereed/Peer-reviewed

An accurate and precise 3 μL blood collection and dispensing system is presented for the preparation of dried blood spot (DBS) samples. Using end-to-end glass capillaries in conjugation with pre-punched DBS pads, a blood micro collection system was developed to eliminate the haematocrit dispersion, widely associated with DBS technology, while providing better levels of accuracy and precision during sample preparation. This methodology is compared to traditional micro-volume blood collection systems, such as a pipette and a digitally controlled analytical syringe. Results showed that % of recovery for the capillary methodology was closer to 100% across the three haematocrit (HCT) levels tested and when prepared by two users (98 to 100% for capillaries, 78 to 104% for pipette and 93 to 97% for digital syringe) attesting a higher accuracy. Additionally, by taking advantage of the capillary action mechanism to collect and dispense autonomously the desired volume of blood onto the DBS pad, coefficients of variation between two individuals were significantly lower than with standard methodologies (capillaries-0.05 to 0.77%, pipette-12.71 to 18.53% and digital syringe-0.72 to 1.77%). This alternate aspiration and dispensing methodology could be used by different users without compromising accuracy or precision when handling low volumes of blood during the pre-analytical steps. Graphical abstract Comparison of novel capillary dispensing methodology for dried blood spot sample preparation with pipette and digital syringe methodologies through accuracy and precision measurements of caffeine.

An evaporative membrane modulator was developed, built and evaluated to avoid loss of performance in the second dimension when coupling two-dimensional liquid chromatography systems. The automated interface reduces the volume after 1 D elution on-line by a pre-determined factor, regardless of the separation gradient. This volume reduction ensures that the injection volume in the 2 D is appropriate for the second column, avoiding the detrimental effects of overloading. In addition, the fraction solvent composition is constant over the length of the separation increasing reproducibility of 2 D separations. The evaporative membrane modulator was demonstrated with a 10-fold reduction, reducing the injection volume from 50 to 5 μL. A consequence of the EMM device is a reduction in the capacity of the first dimension, which is decreased by a factor of 2.4, but the peak width at half maximum was reduced by up to 22% in the second dimension. When band broadening is considered, the corrected peak capacity with the modulator was only 10% lower than that without the modulator, but with a gain in peak height of 2-3, and a decrease in retention time between subsequent peak-slices reduced from 4s to be negligible. This improves peak shape and shows potential to facilitate peak identification and quantification in more complex applications. Refereed/Peer-reviewed

Multimaterial 3D printing facilitates the rapid production of complex devices with integrated materials of varying properties and functionality. Herein, multimaterial fused deposition modeling (MM-FDM) 3D printing was applied to the fabrication of low-cost passive sampler devices with integrated porous membranes. Using MM-FDM 3D printing, the device body was produced using black polylactic acid, with Poro-Lay Lay-Felt filament used for the printing of the integrated porous membranes (rubber-elastomeric polymer, porous after removal of a water-soluble poly(vinyl alcohol) component). The resulting device consisted of two interlocking circular frames, each containing the integrated membrane, which could be efficiently sealed together without the need for additional O-rings, and prevented loss of enclosed microparticulate sorbent. Scanning electron microscopy (SEM) analysis of the purified composite filament confirmed the porous properties of the material, an average pore size of ∼30 nm. The printed passive samplers with various membrane thicknesses, including 0.5, 1.0, and 1.5 mm, were evaluated for their ability to facilitate the extraction of atrazine as the model solute onto the internal sorbent, under standard conditions. Gas chromatography-mass spectrometry was used to determine the uptake of atrazine by the device from standard water samples and also to evaluate any chemical leaching from the printed materials. The sampler with 0.5 mm thick membrane showed the best performance with 87% depletion and a sampling rate of 0.19 Ld -1 (n = 3, % RSD = 0.59). The results obtained using these printed sampling devices with integrated membranes were in close agreement to devices fitted with a standard poly(ether sulfone) membrane. usc Refereed/Peer-reviewed

The extraction of target analytes from biological samples is a bottleneck in analysis. A microfluidic device featuring an electrokinetic size and mobility trap was formed by two nanojunctions of different pore size to extract and concentrate analytical targets from complex samples. The trap was seamlessly coupled with electrophoretic separation for quantitative analysis. The device was applied to the analysis of ampicillin levels in blood within 5min and a linear response over the range of 2.5-20μg mL -1 . This covers the recommended levels for treating sepsis, a critical condition with 30 to 50 % mortality and unpredicted drug levels. The device provides a new opportunity for on-site therapeutic drug monitoring, which should enable quick and accurate dosing and may save lives in such critical conditions. Refereed/Peer-reviewed

CE methods have been developed for the analysis of organic and peroxide-based explosives. These methods have been developed for deployment on portable, in-field instrumentation for rapid screening. Both classes of compounds are neutral and were separated using micellar electrokinetic chromatography (MEKC). The effects of sample composition, separation temperature, and background electrolyte composition were investigated. The optimised separation conditions (25mM sodium tetraborate, 75mM sodium dodecyl sulfate at 25°C, detection at 200nm) were applied to the separation of 25 organic explosives in 17min, with very high efficiency (typically greater than 300,000 platesm-1) and high sensitivity (LOD typically less than 0.5mgL-1; around 1-1.5μM). A MEKC method was also developed for peroxide-based explosives (10mM sodium tetraborate, 100mM sodium dodecyl sulfate at 25°C, detection at 200nm). UV detection provided LODs between 5.5 and 45.0mgL-1 (or 31.2-304μM), which is comparable to results achieved using liquid chromatography. Importantly, no sample pre-treatment or post-column reaction was necessary and the peroxide-based explosives were not decomposed to hydrogen peroxide. Both MEKC methods have been applied to pre-blast analysis and for the detection of post-blast residues recovered from controlled, small scale detonations of organic and peroxide-based explosive devices. Refereed/Peer-reviewed

CE has been alive for over two decades now, yet its sensitivity is still regarded as being inferior to that of more traditional methods of separation such as HPLC. As such, it is unsurprising that overcoming this issue still generates much scientific interest. This review continues to update this series of reviews, first published in Electrophoresis in 2007, with updates published in 2009 and 2011 and covers material published through to June 2012. It includes developments in the field of stacking, covering all methods from field amplified sample stacking and large volume sample stacking, through to isotachophoresis, dynamic pH junction and sweeping. Attention is also given to online or inline extraction methods that have been used for electrophoresis. Refereed/Peer-reviewed

A simple sequential injection capillary electrophoresis (SI-CE) instrument with capacitively coupled contactless conductivity detection (C4D) has been developed for the rapid separation of anions relevant to the identification of inorganic improvised explosive devices (IEDs). Four of the most common explosive tracer ions, nitrate, perchlorate, chlorate, and azide, and the most common background ions, chloride, sulfate, thiocyanate, fluoride, phosphate, and carbonate, were chosen for investigation. Using a separation electrolyte comprising 50 mM tris(hydroxymethyl)aminomethane, 50 mM cyclohexyl-2-aminoethanesulfonic acid, pH 8.9 and 0.05% poly(ethyleneimine) (PEI) in a hexadimethrine bromide (HDMB)-coated capillary it was possible to partially separate all 10 ions within 90 s. The combination of two cationic polymer additives (PEI and HDMB) was necessary to achieve adequate selectivity with a sufficiently stable electroosmotic flow (EOF), which was not possible with only one polymer. Careful optimization of variables affecting the speed of separation and injection timing allowed a further reduction of separation time to 55 s while maintaining adequate efficiency and resolution. Software control makes high sample throughput possible (60 samples/h), with very high repeatability of migration times [0.63-2.07% relative standard deviation (RSD) for 240 injections]. The separation speed does not compromise sensitivity, with limits of detection ranging from 23 to 50 μg•L-1 for all the explosive residues considered, which is 10× lower than those achieved by indirect absorbance detection and 2× lower than those achieved by C 4D using portable benchtop instrumentation. The combination of automation, high sample throughput, high confidence of peak identification, and low limits of detection makes this methodology ideal for the rapid identification of inorganic IED residues. en-aus Refereed/Peer-reviewed

This study describes the development of a novel fluorescent tag, O-2-[aminoethyl]fluorescein, for the separation of sugars by capillary electrophoresis with fluorescence detection using an argon ion laser. The tag was synthesised using three consecutive steps namely: esterification, alkylation and hydrolysis, specifically designed to offer a flexible way in which to make an assortment of fluorescent tags from cheap and readily available starting reagents (typically less than $1 per g of fluorescent tag). Via this flexible synthetic pathway, O-2-[aminoethyl]fluorescein was designed and synthesised with a spacer group to lower steric effects between the fluorescein backbone and the reducing end of the carbohydrate which were anticipated to improve the reactivity of the tag. The newly synthesised tag, O-2-[aminoethyl]fluorescein was evaluated against structurally similar commercial fluorescent motifs namely fluorescent 5-aminomethylfluorescein and non-fluorescent 5-aminofluorescein. Kinetic studies indicated that O-2-[aminoethyl]fluorescein showed similar labeling efficiencies as 5-aminomethylfluorescein, but were achieved in only 30 min, supporting the notion of improved reactivity of the spacer group. The sensitivity of O-2-[aminoethyl]fluorescein was evaluated using maltoheptaose with a detection limit of 1 nM obtained, which was slightly higher than that of 0.3 nM obtained with 5-aminomethylfluorescein, and was due to its lower quantum yield (0.24) when conjugated to the sugar. The separation performance of the tag was also benchmarked with the two commercial reagents using a range of corn syrup oligosaccharides, from 4 to 10 glucose units, typically found in rice starch. Separations were performed using an electrolyte containing 100 mM boric acid, tris at pH 8.65 as background electrolyte, 30 kV applied voltage, 50 μm I.D. × 40 cm (30 cm effective length) capillary. The novel tag showed better resolution of small oligosaccharides, G3 and G4, than the other two reagents, but slightly worse resolution for the longer oligosaccharides, most likely due to the monovalent charge state of the O-2-[aminoethyl]fluorescein compared to the divalent charge of the other two tags. Refereed/Peer-reviewed

Novel CE methods have been developed on portable instrumentation adapted to accommodate a capacitively coupled contactless conductivity detector for the separation and sensitive detection of inorganic anions and cations in post-blast explosive residues from homemade inorganic explosive devices. The methods presented combine sensitivity and speed of analysis for the wide range of inorganic ions used in this study. Separate methods were employed for the separation of anions and cations. The anion separation method utilised a low conductivity 70mM Tris/70mM CHES aqueous electrolyte (pH 8.6) with a 90 cm capillary coated with hexadimethrine bromide to reverse the EOF. Fifteen anions could be baseline separated in 7 min with detection limits in the range 27-240 μg/L. A selection of ten anions deemed most important in this application could be separated in 45 s on a shorter capillary (30.6 cm) using the same electrolyte. The cation separation method was performed on a 73 cm length of fused-silica capillary using an electrolyte system composed of 10mM histidine and 50mM acetic acid, at pH 4.2. The addition of the complexants, 1 mM hydroxyisobutyric acid and 0.7mM 18-crown-6 ether, enhanced selectivity and allowed the separation of eleven inorganic cations in under 7 min with detection limits in the range 31-240 μg/L. The developed methods were successfully field tested on post-blast residues obtained from the controlled detonation of homemade explosive devices. Results were verified using ion chromatographic analyses of the same samples. Refereed/Peer-reviewed

An optimised packing procedure for the production of high efficiency, short, particle-packed ion-exchange columns is reported. Slurry-packing techniques were applied to a series of interconnected short columns, with the columns situated intermediate between the inlet and outlet ends of the series being used for separations. The fast separation and determination of inorganic anions was achieved using short (4 mm ID, 30 mm long) columns packed with Dionex AS20 high-capacity anion-exchange stationary phase. Seven inorganic anions (bromate, chloride, chlorate, nitrate, sulfate, chromate and perchlorate) are separated in 2.6 min using a hydroxide gradient and a flow-rate of 1.8 mL/min (total analysis time including re-equilibration was 3.5 min). Under isocratic conditions, the home-packed columns exhibited efficiency values of 43,000 N/m for chloride at a flow-rate of 0.3 mL/min, compared to 54,000 N/m for a commercial 250 mm AS20 column at the same flow-rate. However, the short columns gave approximately a threefold higher sample throughput. The short, home-packed columns could be produced reproducibly and gave consistent performance over extended periods of usage. Refereed/Peer-reviewed

This study explores the use of pH stacking in conjunction with 5-aminofluorescein as a derivatization agent for the sensitive analysis of simple sugars such as glucose, lactose and maltotriose by capillary electrophoresis (CE). The derivatization agent was selected on the basis of its extremely high molar absorptivity, its compatibility with a 488 nm light-emitting diode (LED) and the fact that it has two ionizable groups making it compatible with on-line stacking using a dynamic pH junction. The influence of both acetic and formic acids at concentrations of 0.19, 0.019 and 0.0019 mol L-1 were investigated with regard to both derivatization efficiency and the ability to stack using a dynamic pH junction. Superior sensitivity and resolution was obtained in formic acid over acetic acid. Substantially lower peaks were obtained with 0.19 mol L-1 formic acid when compared to 0.019 and 0.0019 mol L-1 concentrations, which was confirmed by computer simulation studies to be due to the inadequate movement of the pH boundary for stacking. Further simulation studies combined with experimental data showed the separation with the best resolution and greatest sensitivity when the carbohydrates were derivatized with the 0.095 mol L-1 formic acid. Utilisation of stacking via dynamic pH junction mode in conjunction with LED detection enabled efficiencies of 150,000 plates and detection limits in the order of 8.5 × 10-8 mol L-1 for simple sugars such as glucose, lactose and maltotriose hydrate. The current system also demonstrates a 515 times improvement in sensitivity when compared to using a normal deuterium lamp, and 16 times improvement over other systems using LEDs. Refereed/Peer-reviewed

Anions and cations of interest for the post-blast identification of homemade inorganic explosives were separated and detected by ion chromatographic (IC) methods. The ionic analytes used for identification of explosives in this study comprised 18 anions (acetate, benzoate, bromate, carbonate, chlorate, chloride, chlorite, chromate, cyanate, fluoride, formate, nitrate, nitrite, perchlorate, phosphate, sulfate, thiocyanate and thiosulfate) and 12 cations (ammonium, barium(II), calcium(II), chromium(III), ethylammonium, magnesium(II), manganese(II), methylammonium, potassium(I), sodium(I), strontium(II), and zinc(II)). Two IC separations are presented, using suppressed IC on a Dionex AS20 column with potassium hydroxide as eluent for anions, and non-suppressed IC for cations using a Dionex SCS 1 column with oxalic acid/acetonitrile as eluent. Conductivity detection was used in both cases. Detection limits for anions were in the range 2-27.4 ppb, and for cations were in the range 13-115 ppb. These methods allowed the explosive residue ions to be identified and separated from background ions likely to be present in the environment. Linearity (over a calibration range of 0.05-50 ppm) was evaluated for both methods, with r2 values ranging from 0.9889 to 1.000. Reproducibility over 10 consecutive injections of a 5 ppm standard ranged from 0.01 to 0.22% relative standard deviation (RSD) for retention time and 0.29 to 2.16%RSD for peak area. The anion and cation separations were performed simultaneously by using two Dionex ICS-2000 chromatographs served by a single autoinjector. The efficacy of the developed methods was demonstrated by analysis of residue samples taken from witness plates and soils collected following the controlled detonation of a series of different inorganic homemade explosives. The results obtained were also confirmed by parallel analysis of the same samples by capillary electrophoresis (CE) with excellent agreement being obtained. Refereed/Peer-reviewed

An electrophoretic method for the separation of derivatised mono- and di-saccharides with on-line concentration via dynamic pH junction has been developed and optimised in capillaries. Dynamic pH junction is perfectly suited for on-line concentration of derivatised sugars due to the acidic derivatisation conditions, however, most reagents for carbohydrates are not ionisable, requiring the use of the novel reagent, O-2-[aminoethyl]fluorescein. Optimisation of the separation selectivity yielded best separations with 170 mM ammonium borate buffer at pH 8.60 in an acrylamide coated capillary. When using an injection comprising 7% of the capillary volume and detection via laser induced fluorescence (LIF) with an argon ion laser, limits of detection as low as 0.13 nM for maltose were obtained, which was 10 times lower than could be achieved without on-line concentration. In order to implement this system in a glass/PDMS microchip, the low pH sample was introduced into the microchannels via a cathodic pH independent electro-osmotic flow (EOF) generated using a poly(dimethyldiallylmethyl-ammonium chloride) (PDADMAC)/poly(styrene sulfonate) (PSS) polyelectrolyte multilayer coating. Optimisation of the injection volume in capillaries greatly simplified translation to the microchip platform, with the optimum capillary sample volume of 7%, dictating the use of an off-set cross with a volume 7% of the separation channel. Microchip separations of maltose, glucose, galactose and allose with dynamic pH junction, were achieved within 120 s, with the limit of detection of maltose using a light emitting diode induced fluorescence (LEDIF) detection system being 790 nM. This is 10 times lower than that achieved without concentration, and is lower than other reports of derivatised sugars using LEDIF detection. This is the first implementation of on-line concentration via a dynamic pH junction in a microchip, and significantly, the improvement in sensitivity achieved when translated to the microchip was equivalent to that achieved in capillaries. Refereed/Peer-reviewed

A method based on indirect photometric detection (IPD) in CE employing a blue LED (473 nm) as a light source and the highly absorbing (478 nm) anionic dye, Orange G, as the probe ion was developed for the sensitive analysis of inorganic and organic anions. The use of nonaqueous solvents was examined as a simple way to reduce the adsorption of the dye onto the capillary wall and to thereby improve the baseline stability. The benefits of this approach were confirmed by experiments using BGEs in methanol (MeOH) and DMSO in which superior baselines were obtained relative to those achieved using aqueous electrolyte systems. A range of commercial LEDs was tested to improve the detection performance, with a difference of 25% in sensitivity being observed between the best and worst performing LED. The final system (4 mM Orange G, 0.05% w/v hydroxypropylcellulose (HPC), 20 mM triethanolamine (TEA) in pure MeOH) exhibited stable baselines and very low LODs (0.10-0.18 μM) for a test mixture comprising nine inorganic and organic anions. These values represent a two- to six-fold improvement over previous studies and the proposed method provides the most sensitive IPD method for the determination of anions using CE published to date. RSDs for ten replicates were in the ranges of 0.42-0.62% for migration time, 1.41-3.46% for peak area and 3.20-5.78% for peak height. Refereed/Peer-reviewed

Control of the dielectric breakdown of PDMS was achieved by limiting the current during the breakdown process. This enabled tuning of the nanochannel pore size and hence their permeability for molecules of different molecular weights. This method enabled the analysis of the drug quinine from whole blood in 3 min using a simple, disposable microfluidic device. Refereed/Peer-reviewed

A laser-patterned microchip electrophoresis device with integrated polymer electrodes for DC high voltages and AC capacitively-coupled contactless conductivity detection was developed. Electrophoresis separations comparable to devices with metal electrodes were obtained, at approximately 20 times lower cost. Refereed/Peer-reviewed

Many of the channels and reservoirs in microfluidic systems are used simply to allow liquids with different compositions to be delivered to where they are needed. An alternative approach is to use dissolved photochemicals and variable intensity LEDs to generate composition changes in situ. We applied this approach to generate concentration gradients of HCl for gradient ion chromatography. Refereed/Peer-reviewed

This work describes the development of a fully polymeric microchip with integrated polymeric electrodes suitable for performing microchip electrophoresis. The polymer electrodes were fabricated in a thin film of the conducting polymer, polyaniline (PANI), by flash lithography using a studio camera flash and a transparency mask. During flash welding, exposed regions welded into non-conducting regions forming a conducting polymer circuit in the non-exposed regions. Using a structured layer of dry film photoresist for sealing, a polydimethylsiloxane (PDMS) substrate containing channels and reservoirs was bound to the PANI film to form an integrated microfluidic device. The conducting regions of the PANI film were shown to be capable of carrying the high voltages of up to 2000 V required for chip electrophoresis, and were stable for up to 30 minutes under these conditions. The PANI electrodes were used for the electrophoretic separation of three sugars labelled with 8-amino-1,3,6-pyrenetrisulfonic acid (APTS) in the dry film resist - PDMS hybrid device. Highly efficient separations comparable to those achieved in similar microchips using platinum electrodes confirm the potential of polyaniline as a new material suitable for high voltage electrodes in Lab-on-a-chip devices. Refereed/Peer-reviewed