PRIORITY DOCUMENT

[0001] The present application claims priority from Australian Provisional Patent Application No. 2019902076 titled“SLURRY TASTER” and fded on 14 June 2019, the content of which is hereby incorporated by reference in its entirety.

TECHNICAL FIELD

[0002] The present disclosure relates generally to microfluidic devices for continuous process monitoring and, more specifically, devices for continuously sampling target solutes from complex sample matrices, such as mineral slurries.

BACKGROUND

[0003] In many industries, continuous process monitoring is a powerful tool that can be used to understand changes in chemical processes and to adjust process parameters so that a higher yield is achieved. For example, in recent times there has been a trend in fields like pharmaceuticals, food processing, petrochemicals, and mining to continuously monitor processes at several points along a production line. The main goal is to obtain high-quality data that can be reliably used for better understanding of the physical and chemical parameters leading to efficient use of resources manifested as higher quality yield at a lower cost and environmental impact.

[0004] A major challenge for continuous process monitoring systems is that suspensions or complex mixtures containing particulates are difficult to monitor. The particles in the stream are detrimental to most detection methods used in the analysis unless an extensive off-line sample pretreatment is performed. Conventional methods like centrifugation, filtration or solvent extraction are associated with increased cost and time pressure, demand for trained personnel, and high waste production. Alternatively, an on-line sample pretreatment unit that can be easily coupled with a suitable detection technique and remotely controlled will facilitate the wider implementation of process monitoring.

[0005] Microfluidic devices benefit from unique fluid behaviour on the microscale and therefore offer a powerful and versatile way for integration of several processes and automation. The main focus for the use of microfluidic devices has been for biomedical applications and to a lesser extent for chemical synthesis, environmental monitoring, and food processing control. ^1-2 However, despite the massive economic and environmental impact associated with mineral processing monitoring and control, the adoption of microfluidic devices has not been widespread. Current methods for mineral processing monitoring and control tend to rely on off-line sample preparation followed by analysis using

conventional techniques which is labour intensive and time-consuming.

[0006] For biomedical applications, separation of blood plasma prior to analysis constitutes a large part of the research and approaches vary between platforms that rely on external energy, like centrifugal, ³ and passive platforms that benefit from the unique behaviour of blood cells on the microscale. Passive platforms are preferred due to their lower energy consumption and simplified manufacturing. A common feature among them is that they rely on the differences between the behaviour of cells and other blood constituents in response to the flow stream lines and the inertial forces acting on the cells. The most famous of the designs is the H-filter, sometimes called T-sensor, introduced by the Yager group. ^4-6 An H- filter relies on differences in diffusion between constituents of different size. In its simplest form, a stream of the sample is in parallel contact with a stream of clean buffer. After a certain distance, small ions will be able to diffuse to more distance into the buffer stream while larger size components will diffuse less. By adjusting the length of the channel, ions can be separated from blood cells and plasma proteins and collected at the buffer outlet. Channel geometry and flow resistance can be adjusted to achieve hydrodynamic filtration. ⁷ Plasma separation and cell sorting can be achieved through

optimization of the inertial forces acting on the cells to permit/prevent them from flowing into side channels. Both approaches require a fully enclosed system where the sample is introduced into the microchannel. This can be problematic in cases where there is a wide particle size distribution as some particles may block the microchannels.

[0007] There is thus a need to provide devices and processes for continuous process monitoring that overcome or ameliorate one or more of the problems associated with known devices and processes. Alternatively, or in addition, there is a need to provide devices and processes for continuous process monitoring that provide an alternative to known devices and processes.

SUMMARY

[0008] According to a first aspect, there is provided a microfluidic device for extraction of one or more target soluble component from a complex sample matrix, the device comprising:

a substrate;

a collector solution path disposed within the substrate, the collector solution path comprising: a collector microfluidic channel configured for flow of a collector solution therein, an inlet port on a surface of the substrate and in fluidic contact with the collector microfluidic channel for introducing the collector solution to the collector microfluidic channel, an outlet port on a surface of the substrate and in fluidic contact with the collector microfluidic channel for removing the collector solution from the collector microfluidic channel;

a slit channel disposed within the substrate and configured so that it can be brought into fluidic contact with the complex sample matrix to be sampled and prevent ingress of at least some of any non- soluble matter present in the complex sample matrix into the collector solution path.

[0009] The device of the first aspect employs a slit channel to interface the outside turbulent, mixed, laminar or static complex sample matrix environment with laminar flow of the collector solution inside the microfluidic device. The device can be used for a range of sampling processes in the pharmaceuticals, food processing, petrochemicals, and mining industries, such as (but not limited to) the analysis of soluble metal ion complexes in mineral slurries for on-line continuous monitoring.

[0010] The non-soluble matter present in the bulk complex sample matrix may include any one or more of: bubbles, microparticles, nanoparticles, droplets, large molecules, solutes, and surfactants.

[0011] According to a second aspect, there is provided a microfluidic apparatus for extraction of one or more soluble component from a complex sample matrix, the apparatus comprising:

a microfluidic device of the first aspect; and

a first pump adapted to be operably connected to the inlet port for introducing the collector solution to the collector microfluidic channel, the additional microfluidic channels and/or the network of microfluidic channels.

[0012] In certain embodiments of the second aspect, the apparatus further comprises a second pump adapted to be operably connected to the outlet port for removing the collector solution from the collector microfluidic channel.

[0013] In certain embodiments of the second aspect, the apparatus further comprises a fluid flow control unit to provide inlet and outlet fluid flow at a predetermined flow rate.

[0014] In certain embodiments of the second aspect, the apparatus further comprises a detector operable to determine the presence and/or concentration of the target soluble components in the collector solution.

[0015] In certain embodiments of the second aspect, the apparatus further comprises an analyser operable to perform one or more analysis on the collector solution removed from the microfluidic channel. [0016] In certain embodiments of the second aspect, the apparatus further comprises a chamber for bulk complex sample matrix pre -treatment. The complex sample matrix pre-treatment carried out in the chamber may be a chemical pre-treatment such as oxidation/reduction, complex formation, pH adjustment, etc., or a physical pre -treatment such as stirring, etc.

[0017] According to a third aspect, there is provided a process for extracting one or more target soluble component from a complex sample matrix, the process comprising:

sampling the complex sample matrix by bringing the slit channel of the microfluidic device of the first aspect or the second aspect into fluidic contact with the complex sample matrix that is under static, laminar, mixed or turbulent bulk conditions to introduce a fraction of the complex sample matrix into the slit channel and prevent ingress of at least some of any non-soluble matter present in the complex sample matrix into the collector solution path; and

flowing a collector solution through the collector solution path of the microfluidic device of the first aspect or the second aspect under conditions to provide fluidic contact between the fraction of the complex sample matrix and the collector solution and transfer at least some of any one or more target soluble component present in the complex sample matrix from the fraction of the complex sample matrix to the collector solution.

[0018] In certain embodiments of the third aspect, the process further comprises obtaining the collector solution from the outlet port of the microfluidic device of the first aspect or the second aspect.

[0019] In certain embodiments of the third aspect, the process further comprises pumping the collector solution into the collector microfluidic channel via the inlet port under conditions to maintain a predetermined flow rate of the collector solution in the collector microfluidic channel.

[0020] In certain embodiments of the third aspect, the process further comprises pumping the collector solution out of the collector microfluidic channel via the outlet port under conditions to maintain a predetermined flow rate of the collector solution in the collector microfluidic channel.

[0021] In certain embodiments of the third aspect, the process further comprises operating a fluid flow control unit to provide inlet and outlet fluid flow at a predetermined flow rate.

[0022] In certain embodiments of the third aspect, the process further comprises determining the presence and/or concentration of any target soluble components in the collector solution.

[0023] In certain embodiments of the third aspect, the process further comprises pre -treating the complex sample matrix prior to sampling. The complex sample matrix pre-treatment may be a chemical pre-treatment such as oxidation/reduction, complex formation, pH adjustment, etc., or a physical pre- treatment such as stirring, etc.

[0024] According to a fourth aspect, there is provided a use of the microfluidic device of the first aspect or the microfluidic apparatus of the second aspect in an analyte extraction process.

BRIEF DESCRIPTION OF THE FIGURES

[0025] Embodiments will be discussed with reference to the accompanying figures wherein:

[0026] Figure 1 is a schematic diagram showing the microfluidic device design. The slit channel was created at a lower depth than the collector microfluidic channel to allow interfacing the laminar flow of the collector solution with the turbulent bulk complex sample matrix while preventing non-soluble matter from blocking the device;

[0027] Figure 2 is a schematic diagram of a microfluidic apparatus comprising the microfluidic device of Figure 1 ;

[0028] Figure 3 is a plot showing the effect of different inlet/outlet flow rate ratios on the extraction of iron (III) from a 3% EDTA solution;

[0029] Figure 4 shows experimental results supported with simulation data for the extraction mechanism through the microfluidic device at different flow rates and flow rate ratios; and

[0030] Figure 5 shows experimental results for the extraction of iron (III) from the Dugald river slurry at 0.5 and 1.0 mL/h, respectively. Values are the average of 3 experiments.

DESCRIPTION OF EMBODIMENTS

[0031] A microfluidic device was designed for the extraction of soluble components from a complex sample matrix containing non-soluble matter under turbulent conditions and followed by optical detection. The design employs a slit channel to interface the outside turbulent environment with laminar flow of a collector solution inside the microfluidic device. By way of a non-limiting example of the use of the device, it was used in the analysis of soluble metal ion complexes in mineral slurries for on-line continuous monitoring. This example application enables better understanding of the factors affecting flotation in mineral processing leading to higher yield and lower environmental impact. The microfluidic device described herein provides an opportunity for automation and remote control which will greatly enhance safety for workers in mining and other industries. [0032] Figure 1 shows a microfluidic device 10 suitable for use in extraction of one or more soluble component from a complex sample matrix 12. The bulk complex sample matrix 12 may be under static, laminar, mixed or turbulent conditions. The device 10 comprises a substrate 14. A collector solution path 16 is disposed within the substrate 14. The collector solution path 16 comprises a collector microfluidic channel 18 configured for flow of a collector solution within the microfluidic channel 18. The collector solution path 16 also comprises an inlet port 20 on a surface 22 of the substrate 14 and in fluidic contact with the collector microfluidic channel 18 for introducing the collector solution to the collector microfluidic channel 18. The collector solution path 16 also comprises an outlet port 24 on the surface 22 of the substrate 14 and in fluidic contact with the collector microfluidic channel 18 for removing the collector solution from the collector microfluidic channel 18. A slit channel 26 is configured so that it can be brought into fluidic contact with the complex sample matrix 12 to be sampled and prevent ingress of at least some of any non-soluble matter 28 present in the complex sample matrix 12 into the collector solution path 16. Specifically, the slit channel 26 allows fluidic contact between the complex sample matrix 12 to be sampled in the slit channel 26 and the collector solution in the collector solution path 16.

[0033] As used herein, the term "microfluidic", and variants thereof, means that a substrate, chip, device or apparatus containing fluid control features that have at least one dimension that is sub- millimetre and, typically less than 100 mm, and greater than 1 mm. Furthermore, the terms "microfluidic channel", "microchannel", and variants thereof, means a channel having at least one dimension that is sub-millimetre and, typically less than 100 mm, and greater than 1 mm.

[0034] The substrate 14 may take any suitable form, can be made from any suitable material and can be fabricated using any suitable fabrication process. Materials suitable for the manufacture of substrates for microfluidic devices are known in the art and may be chosen based on considerations such as cost, inertness or reactivity toward fluids and other materials that will be in contact with the devices, etc. Some examples of suitable substrate materials include glass, quartz, metal (e.g. stainless steel, copper), silicon, and polymers. In certain embodiments, the substrate 14 is a glass substrate. For example, Pyrex glass substrates may be suitable. Suitable polymeric substrates 14 include polydimethylsiloxane (PDMS), polytetrafluoroethylene (PTFE), other perfluoropolyether (PFPE) based elastomers,

polymethylmethacrylate (PMMA), silicone, and the like. Polymer substrates 14 may be used when the collector solution is to be analysed colorimetrically. Quartz substrates 14 may be used when the collector solution is to be analysed by UV-vis spectroscopy. The substrate 14 in the illustrated embodiments is rectangular in plan view but it is envisaged that it can be other shapes in plan view, such as circular, square, etc. The substrate 14 has a thickness adequate for maintaining the integrity of the microfluidic device 10. In the illustrated embodiments, the substrate 14 is about 2.2 mm thick. By way of example, a glass substrate 14 can be fabricated from two thin, rectangular glass plates using standard wet etching procedures and subsequent bonding in a face to face manner under vacuum to form the substrate 14. [0035] A design comprising the collector microfluidic channel 18 connected to the slit channel 26 can be etched onto each of two plates that are subsequently bonded in face-to-face manner to form the substrate 14 comprising the collector microfluidic channel 18 connected to the slit channel 26.

Complimentary parts of each channel 18 and 26 may be formed on a face of each of the plates and the plates and the faces then brought together to form the substrate 14 having the collector microfluidic channel 18 and the slit channel 26 extending into each plate. Alternatively, each channel 18 and 26 may be formed on a face of one of the plates and the respective channels 18, 26 capped by bonding the second plate to the first plate in a face to face manner.

[0036] Methods for forming microfluidic channel networks are known in the art. For example, microfluidic substrates or chips can be fabricated using standard photolithographic and etching procedures including soft lithography techniques (e.g. see Shi J., et al., Applied Physics Letters 91,

153114 (2007); Chen Q., et al., Journal of Microelectromechanical Systems, 16, 1 193 (2007); or Duffy et al., Rapid Prototyping of Microfluidic Systems in Poly(dimethylsiloxane), Anal. Chem., 70 (23), 4974- 4984 (1998)), such as near-field phase shift lithography, microtransfer molding, solvent-assisted microcontact molding, microcontact printing, and other lithographic microfabrication techniques employed in the semiconductor industry. Direct machining or forming techniques may also be used as suited to the particular substrate 14. Such techniques may include hot embossing, cold stamping, injection molding, direct mechanical milling, laser etching, chemical etching, reactive ion etching, physical and chemical vapour deposition, and plasma sputtering. The particular methods used will depend on the function of the particular microfluidic network, the materials used as well as ease and economy of production.

[0037] Advantageously, the slit channel 26 is etched at a lower depth relative to the collector microfluidic channel 18. The depth of the slit channel 26 may be equal or less than the depth of the collector microfluidic channel 18. For example, collector microfluidic channel 18 may have a depth of 60 mm and the slit channel 26 may have a depth of 25 mm. The low depth of the slit channel 26 provides sufficient flow resistance to stop any turbulence in the fraction of the complex sample matrix that enters the slit channel 26 and allow for very small but controlled pressure at an outlet slit opening 30 between the slit channel 26 and the collector microfluidic channel 18 to extract part of the solution and soluble components from the complex sample matrix 12 without being blocked by any non-soluble matter 28 present in the complex sample matrix 12 (see Figure 1).

[0038] The collector solution path 16 is disposed within the substrate 14 and comprises the collector microfluidic channel 18, the inlet port 20 and the outlet port 24 as described earlier and as shown in Figure 1. The collector microfluidic channel 18 can take any shape in cross section. The collector microfluidic channel 18 may have a depth (i.e. height) of 1 to 500 mm, such as 10 to 100 mm. In certain embodiments, the collector microfluidic channel 18 has a depth of 60 mm. The collector microfluidic channel 18 can also take any configuration in plan view. In the embodiment illustrated in Figure 1 , the collector microfluidic channel 18 is generally U shaped in plan view. However, it is contemplated that the collector microfluidic channel 18 can take any shape and have any suitable length provided that a portion of the collector microfluidic channel 18 is in fluidic contact with the slit channel 26 at some point along the length of the collector microfluidic channel 18.

[0039] Optionally, the collector solution path 16 and/or the device 10 may have one or more additional microfluidic channel (not shown) and/or a network of microfluidic channels (not shown) in fluidic contact with the collector microfluidic channel 18. The additional microfluidic channels and/or a network of microfluidic channels may be configured for a variety of purposes, such as to flow the collector solution into or out of the collector micro fluidic channel 18 and/or to introduce one or more reagent into the collector microfluidic channel 18.

[0040] An inlet port 20 and outlet port 24 are formed on a surface 22 of the substrate 14 and each port 20, 24 is in fluidic contact with the collector microfluidic channel 18. The collector solution is introduced into the collector microfluidic channel 18 via the inlet port 20. A tube (not shown) can be fitted to the inlet port 20 using methods known in the art, such as by use of an aluminium holder. The tube may be connected to a source of collector solution. PEEK adaptors and FEP, or any other suitable material, tubing can be used for this purpose. The collector solution can be introduced into the collector microfluidic channel 18 using a suitable pump, syringe or other suitable fluid delivery device. For example, commercially available precision syringe pumps can be used to introduce the collector solution into the collector microfluidic channel 18 via the inlet port 20.

[0041] In certain embodiments, a pump is connected to the outlet port 24 and configured to draw the collector solution from the microfluidic channel 18 via the outlet port 24. A tube (not shown) can be fitted to the outlet port 24 using methods known in the art, such as by use of an aluminium holder. PEEK adaptors and FEP, or any other suitable material, tubing and a commercially available syringe pump can be used for this purpose. In these embodiments, the flow rate of the collector solution can be maintained at a predetermined rate with a high level of control using a combination of positive and negative pressures for the inlet and the outlet, respectively. The inlet pump and the outlet pump can be set to equal flow rates or they can be set at different flow rates so as to have a lower flow rate at the inlet, such as a 20% lower flow rate for the inlet for example. The flow rate of the collector solution may be from about 0.1 mL/h to about 1.5 mL/h. Advantageously, the present inventors have found that increasing the percentage offset in the outlet flow rate results in an increase in the amount of target soluble component that is extracted. Without intending to be bound by theory, a higher negative pressure is expected at the outlet slit opening 30 when using higher percentage offset outlet flow rates compared to equal flow rates. [0042] In use, the collector solution flows through the collector microfluidic channel 18 and, in doing so, passes the outlet slit opening 30 where it comes into fluidic contact with a fraction of the complex sample matrix 12 present in the slit channel 26. Flow of the collector solution through the collector microfluidic channel 18 is laminar.

[0043] Typically, when the complex sample matrix 12 is aqueous, the collector solution will be aqueous or a non-aqueous soluble liquid or solvent, such as an organic solvent. The collector solution may contain a ligand or other agent that binds the target soluble component of interest. Organic solvents that could be used include alkanes, alkenes, alkynes, alcohols, aldehydes, ketones, acids, esters, aromatics and their halogen, sulfur, phosphorous, and nitrogen-containing derivatives, silicone oils and their halogen, sulfur, phosphorous, and nitrogen-containing derivatives, petroleum (all commercial grades) and petroleum-based products, and mixtures thereof. In embodiments in which at least one of the solutions comprises an organic liquid, the organic phase is a non-aqueous fluid phase that is at least partially immiscible with the aqueous phase. The solubility of a metal or metal complex in a particular solvent may guide the choice of solvent.

[0044] When the collector solution flow comes into fluidic contact with the fraction of the complex sample matrix 12 in the slit channel 26, the collector solution continues laminar flow but is in intimate contact with the fraction of the complex sample matrix 12 and transfer of at least some of target soluble components from the complex sample matrix 12 to the collector solution occurs to form a collector solution containing extracted target soluble components. This occurs under continuous flow conditions.

[0045] The collector solution containing extracted target soluble components then flows further along the collector micro fluidic channel 18 to the outlet port 24 from which the collector solution is removed from the substrate 14. The outlet port 24 may be connected to suitable tubing in a similar way to the inlet port 20.

[0046] The collector solution that is removed from the substrate 14 may be analysed to determine the presence and/or concentration of one or more target soluble component. For example, the collector solution can be analysed by online UV-vis absorption to determine the concentration of metal complexes in the collector solution. This can be achieved by using a Z-flow cell with quartz windows connected to the outlet port 24. Other methods of analysis include electrochemical, conductivity, pH, colorimetry, optical, and separation analytical techniques such as CE and HPLC.

[0047] The target soluble component could be any target analyte of interest that is in solution in the complex sample matrix 12. The target analyte may be any chemical entity of interest, such as an inorganic substance, an organic substance or a biological substance. In one non-limiting example, the complex sample matrix 12 may be a mineral slurry pre- or post-flotation, a leach solution (e.g. a leach solution derived from an ore sample), mineral tailings, a refinery waste stream, an industrial waste stream (e.g. a tannery waste stream) or similar containing metal ions of interest. The device 10 and processes described herein may be used to assay for the presence and/or concentration of the metal ions in the complex sample matrix 12.

[0048] The metal ion may be selected from one or more ions of the group of metals consisting of: Be, Mg, Al, Sc, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Zn, Ga, Ge, As, Se, Rb, Sr, Y, Zr, Nb, Mo, Tc, Ru, Rh, Pd,

Ag, Cd, In, Sn, Sb, Te, Cs, Ba, Hf, Ta, W, Re, Os, Ir, Pt, Au, Hg, Tl, Pb, Bi, Po, At, Rn, Fr, Ra, La, Ce,

Pr, Nd, Sm, Eu, Gd, Tb, Dy, Er, Tm, Yb, Lu, Ac, Th, Pr, U, Np, Pu, Am, Cm, Bk, and Cf. In certain embodiments, the metal ion is an Fe ion.

[0049] Metal ions of interest may be partitioned in to the collector solution using a ligand for the metal of interest. For example, a complex sample matrix 12 containing Fe ³⁺ may be contacted with a collector solution containing ethylenediaminetetraacetic acid (EDTA). The ligand used will depend on the metal ion of interest but may be selected from the group consisting of (but not limited to): alkyl sulfides, alkyl phosphates, alkyl amines, alkyl phosphoric acids, ketoximes, aldoximes, and derivatives of any of the aforementioned.

[0050] As described earlier and shown in Figure 1, the slit channel 26 is disposed within the substrate 14 and is configured to provide fluidic contact between the complex sample matrix 12 and the collector microfluidic channel 18. The dimensions of the slit channel 26 are such that the slit channel 26 prevents or minimised ingress of at least some of any non-soluble matter 28 present in the complex sample matrix 12 into the collector micro fluidic channel 18 and, hence, the collector solution path 16. Thus, the device 10 can be used to sample complex sample matrices containing a wide range of non-soluble matter 28 and at least some of the non-soluble matter 28 is prevented from entering the device 10. In other words, some of the non-soluble matter 28 is fdtered from the complex sample matrix 12 at the slit channel 26. The non-soluble matter 28 present in the bulk complex sample matrix 12 may include any one or more of: bubbles, microparticles, nanoparticles, droplets, large molecules, solutes, and surfactants.

[0051] As described herein, ingress of some of the non-soluble matter 28 into the collector micro fluidic channel 18 is prevented or minimised by the slit channel 26. It is contemplated in some embodiments, that some of any non-soluble matter 28 in the complex sample matrix 12 may pass through the slit channel 26 and reach the collector microfluidic channel 18. For example, in some applications the dimensions of the slit channel 26 may allow nanoparticles of non-soluble matter through the slit channel 26 whilst still preventing the larger particles of non-soluble matter from entering. The selection of non soluble matter 28 that passes through the slit channel 26 and what doesn't can be based on size, hydrophobicity, polarity, etc. This may have applications in environmental sensing, quality assurance, health, etc. [0052] In certain embodiments, the slit channel 26 is dimensioned to provide flow resistance in the slit channel 26 to minimise turbulence in the complex sample matrix 12 in the slit channel 26. In certain of these embodiments, the slit channel 26 has an aspect ratio of width to depth of at least 100:1, such as 100:1, 101:1, 102:1, 103:1, 104:1, 105:1, 106:1, 107:1, 108:1, 109:1, 110:1, 111:1, 112:1, 113:1, 114:1,

115:1, 116:1, 117:1, 118:1, 119:1, 120:1, 121:1, 122:1, 123:1, 124:1, 125:1, 126:1, 127:1, 128:1, 129:1,

130:1, 131:1, 132:1, 133:1, 134:1, 135:1, 136:1, 137:1, 138:1, 139:1, 140:1, 141:1, 142:1, 143:1, 144:1,

145:1, 146:1, 147:1, 148:1, 149:1, 150:1, 151:1, 152:1, 153:1, 154:1, 155:1, 156:1, 157:1, 158:1, 159:1,

160:1, 161:1, 162:1, 163:1, 164:1, 165:1, 166:1, 167:1, 168:1, 169:1, 170:1, 171:1, 172:1, 173:1, 174:1,

175:1, 176:1, 177:1, 178:1, 179:1, 180:1, 181:1, 182:1, 183:1, 184:1, 185:1, 186:1, 187:1, 188:1, 189:1,

190:1, 191:1, 192:1, 193:1, 194:1, 195:1, 196:1, 197:1, 198:1, 199:1,200:1,201:1,202:1,203:1,204:1,

205:1, 206:1, 207:1, 208:1, 209:1, 210:1, 211:1, 212:1, 213:1, 214:1, 215:1, 216:1, 217:1, 218:1, 219:1,

220:1, 221:1, 222:1, 223:1, 224:1, 225:1, 226:1, 227:1, 228:1, 229:1, 230:1, 231:1, 232:1, 233:1, 234:1,

235:1, 236:1, 237:1, 238:1, 239:1, 240:1, 241:1, 242:1, 243:1, 244:1, 245:1, 246:1, 247:1, 248:1, 249:1,

250:1, 251:1, 252:1, 253:1, 254:1, 255:1, 256:1, 257:1, 258:1, 259:1, 260:1, 261:1, 262:1, 263:1, 264:1,

265:1, 266:1, 267:1, 268:1, 269:1, 270:1, 271:1, 272:1, 273:1, 274:1, 275:1, 276:1, 277:1, 278:1, 279:1,

280:1, 281:1, 282:1, 283:1, 284:1, 285:1, 286:1, 287:1, 288:1, 289:1, 290:1, 291:1, 292:1, 293:1, 294:1,

295:1, 296:1, 297:1, 298:1, 299:1, 300:1, 301:1, 302:1, 303:1, 304:1, 305:1, 306:1, 307:1, 308:1, 309:1,

310:1,311:1,312:1,313:1,314:1,315:1,316:1,317:1,318:1,319 :1,320:1,321:1,322:1,323:1,324:1, 325:1, 326:1, 327:1, 328:1, 329:1, 330:1, 331:1, 332:1, 333:1, 334:1, 335:1, 336:1, 337:1, 338:1, 339:1,

340:1, 341:1, 342:1, 343:1, 344:1, 345:1, 346:1, 347:1, 348:1, 349:1, 350:1, 351:1, 352:1, 353:1, 354:1,

355:1, 356:1, 357:1, 358:1, 359:1, 360:1, 361:1, 362:1, 363:1, 364:1, 365:1, 366:1, 367:1, 368:1, 369:1,

370:1, 371:1, 372:1, 373:1, 374:1, 375:1, 376:1, 377:1, 378:1, 379:1, 380:1, 381:1, 382:1, 383:1, 384:1,

385:1, 386:1, 387:1, 388:1, 389:1, 390:1, 391:1, 392:1, 393:1, 394:1, 395:1, 396:1, 397:1, 398:1, 399:1,

400:1,401:1,402:1,403:1,404:1,405:1,406:1,407:1,408:1,409 :1,410:1,411:1,412:1,413:1,414:1, 415:1,416:1,417:1,418:1,419:1,420:1,421:1,422:1,423:1,424:1, 425:1,426:1,427:1,428:1,429:1, 430:1,431:1,432:1,433:1,434:1,435:1,436:1,437:1,438:1,439:1, 440:1,441:1,442:1,443:1,444:1, 445:1, 446:1, 447:1, 448:1, 449:1, 450:1, 451:1, 452:1, 453:1, 454:1, 455:1, 456:1, 457:1, 458:1, 459:1,

460:1, 461:1, 462:1, 463:1, 464:1, 465:1, 466:1, 467:1, 468:1, 469:1, 470:1, 471:1, 472:1, 473:1, 474:1,

475:1, 476:1, 477:1, 478:1, 479:1, 480:1, 481:1, 482:1, 483:1, 484:1, 485:1, 486:1, 487:1, 488:1, 489:1,

490:1, 491:1, 492:1, 493:1, 494:1, 495:1, 496:1, 497:1, 498:1, 499:1 or 500:1. In certain embodiments, the slit channel 26 has an aspect ratio of width to depth of 200: 1.

[0053] The depth of the slit channel 26 may be from about 1 mm to about 100 mm, for example about 25 mm to about 50 mm. The depth of the slit channel 26 may be about 1 mm, about 2 mm, about 3 mm, about 4 mm, about 5 mm, about 6 mm, about 7 mm, about 8 mm, about 9 mm, about 10 mm, about 11 mm, about 12 mm, about 13 mm, about 14 mm, about 15 mm, about 16 mm, about 17 mm, about 18 mm, about 19 mm, about 20 mm, about 21 mm, about 22 mm, about 23 mm, about 24 mm, about 25 mm, about 26 mm, about 27 mm , about 28 mm , about 29 mm , about 30 mm , about 31 mm, about 32 mm , about 33 mm , about 34 mm , about 35 mm , about 36 mm , about 37 mm , about 38 mm , about 39 mm , about 40 mm , about 41 mm , about 42 mm , about 43 mm , about 44 mm , about 45 mm , about 46 mm , about 47 mm , about 48 mm , about 49 mm , about 50 mm, about 51 mm , about 52 mm , about 53 mm , about 54 mm , about 55 mm, about 56 mm , about 57 mm, about 58 mm , about 59 mm , about 60 mm , about 61 mm , about 62 mm , about 63 mm , about 64 mm , about 65 mm , about 66 mm , about 67 mm , about 68 mm , about 69 mm , about 70 mm , about 71 mm , about 72 mm, about 73 mm , about 74 mm , about 75 mm , about 76 mm , about 77 mm, about 78 mm , about 79 mm , about 80 mm , about 81 mm , about 82 mm, about 83 mm , about 84 mm , about 85 mm, about 86 mm , about 87 mm , about 88 mm , about 89 mm, about 90 mm, about 91 mm , about 92 mm , about 93 mm, about 94 mm, about 95 mm , about 96 mm , about 97 mm , about 98 mm , about 99 mm, or about 100 mm . In practice, it was found that by decreasing the depth of the slit channel 26 from 50 mm to 25 mm, the extent of the turbulence from the bulk solution decreased, thus lowering its effect on the laminar flow.

[0054] The slit channel 26 may contain additional features for support or to further control the flow within the slit channel 26. For example, the slit channel 26 may contain one or more support post that extends between lower and upper surfaces of the slit channel 26. As another example, one or more inner surface of the slit channel 26 could include surface features to control or alter the flow of liquid within the channel. Surface features that could be used include corrugations, dimples, etc. The person skilled in the art will be familiar with a range of features that can be incorporated into microfluidic channels and may be used in the slit channel 26. These features can be but not limited to any shape, dimensions, spacing, and number.

[0055] Optionally, the slit channel 26 can be modified to change surface properties of the channel. For example, the wettability, surface charge, etc may be modified to take into account properties of the complex sample matrix 12, such as pH, ionic strength, temperature, etc.

[0056] Optionally, one or more force may be applied to the slit channel 26 to control the selectivity of the slit channel 26 and/or minimise ingress of non-soluble matter 28. For example, magnetic, electric and/or acoustic forces or fields can be applied to the slit channel 26 to control passage of either the target soluble component or the non-soluble matter 28 in the slit channel 26.

[0057] Based on the above, it can be seen that the non-soluble matter 28 can be excluded from the extraction through the slit channel 26 based on any one or more properties, including (but not limited to) density, size, elasticity, wettability, etc.

[0058] Optionally, the collector microfluidic channel 18 and/or the slit channel 26 may be formed from or lined with a functional material, such as a hydrophilic material or a hydrophobic material. For example, a hydrophilic surface may be suitable for use with an aqueous stream whilst a hydrophobic surface may be suitable for use with an organic stream. An inner surface of the collector microfluidic channel 18 and/or the slit channel 26 may be modified to minimise or prevent adsorption of particles to the surface. For example, the inner surface may be modified with a chemical agent, such as an antifouling agent. Suitable chemical agents are known in the art and include, for example, poly( ethylene glycol), chlorosilanes, methoxysilanes, hydroxysilanes, and their amine, hydroxy, fluorine, carboxylic, derivatives, amine compounds, polyelectrolytes such as poly(methacrylic acid), poly(allylamine), poly(N- vinylpyrrolidone) etc.

[0059] The device 10 can be used for a range of sampling processes in the pharmaceuticals, food processing, petrochemicals, and mining industries, such as (but not limited to) the analysis of soluble metal ion complexes in mineral slurries for on-line continuous monitoring.

[0060] A plurality of devices 10 may be connected together and used to sample either the same target soluble component or each device 10 in a plurality of devices 10 could be used to sample a different target soluble components.

[0061] Also provided herein is a microfluidic apparatus 32 for extraction of one or more soluble component from a complex sample matrix 12. The apparatus comprises a microfluidic device 10 as described herein and a first pump 34 adapted to be operably connected to the inlet port 20 for introducing the collector solution to the collector microfluidic channel 18. The first pump 34 may also be operably connected to any additional microfluidic channels and/or the network of microfluidic channels present in the device 10.

[0062] A second pump 36 may be operably connected to the outlet port 24 for removing the collector solution from the collector microfluidic channel 18, as described earlier.

[0063] The first pump 34 or second pump 36 may be operably connected to a fluid flow control unit 38. The fluid flow control unit 38 can be used to provide inlet and outlet fluid flow at a predetermined flow rate.

[0064] The apparatus may also comprise a detector 40 that is operable to determine the presence and/or concentration of any one or more of the target soluble component present in the collector solution. Non- limiting examples of detectors 40 include UV-vis absorption spectrometers, electrochemical measurement devices, conductivity measurement devices, pH measurement devices, colorimetry measurement devices, optical measurement devices. The detector 40 may also comprise an analytical separation device such as CE and HPLC. Thus, the detector 40 may be an analyser operable to perform one or more analysis on the collector solution removed from the microfluidic channel 18. [0065] Optionally, the apparatus further may comprise a chamber 42 for bulk complex sample matrix 12 pre -treatment. The complex sample matrix 12 pre -treatment carried out in the chamber 42 may be a chemical pre-treatment such as oxidation/reduction, complex formation, pH adjustment, etc., or a physical pre-treatment such as stirring, etc. Any suitable chamber 42 can be used for this purpose.

[0066] Also provided herein is a process for extracting one or more target soluble component from a complex sample matrix, the process comprising:

sampling the complex sample matrix by bringing the slit channel of a microfluidic device or a microfluidic apparatus as described herein into fluidic contact with the complex sample matrix that is under static, laminar, mixed or turbulent bulk conditions to introduce a fraction of the complex sample matrix into the slit channel and prevent ingress of at least some of any non-soluble matter present in the complex sample matrix into the collector solution path; and

flowing a collector solution through the collector solution path of the microfluidic device or a microfluidic apparatus as described herein under conditions to provide fluidic contact between the fraction of the complex sample matrix and the collector solution and transfer at least some of any one or more target soluble component present in the complex sample matrix from the fraction of the complex sample matrix to the collector solution.

[0067] The process may further comprise obtaining the collector solution from the outlet port 24 of the microfluidic device 10.

[0068] The process may further comprise pumping the collector solution into the collector microfluidic channel 18 via the inlet port 20 under conditions to maintain a predetermined flow rate of the collector solution in the collector microfluidic channel 18.

[0069] The process may further comprise pumping the collector solution out of the collector microfluidic channel 18 via the outlet port 24 under conditions to maintain a predetermined flow rate of the collector solution in the collector microfluidic channel 18.

[0070] The process may further comprise operating a fluid flow control unit to provide inlet and outlet fluid flow at a predetermined flow rate.

[0071] The process may further comprise determining the presence and/or concentration of any target soluble components in the collector solution.

[0072] The process may further comprise pre-treating the complex sample matrix prior to sampling. The complex sample matrix pre-treatment may be a chemical pre-treatment such as oxidation/reduction, complex formation, pH adjustment, etc., or a physical pre-treatment such as stirring, etc. [0073] Also provided herein is a use of a microfluidic device or a microfluidic apparatus as described herein in an analyte extraction process.

EXAMPLES

[0074] Microfluidic devices configured as shown in Figure 1 were fabricated in BF-33 glass using standard photolithography and wet etching with HF solution. The etching was done on the two halves of the device to achieve microchannel depth of 60 mm and slit depth of 25 mm. Inlet and outlet ports of 600 mm diameter were made using laser drilling. The surfaces were piranha cleaned and bonded under vacuum. During the experiments, solutions were introduced using precision syringe pumps (KD

Scientific) and glass syringes (Hamilton, 2.5 mL) fitted with PEEK adaptors and FEP tubing (Upchurch Scientific, 800 mm i.d.) and connected to the microchip through an aluminium holder.

[0075] The experiments were done using a total sample volume of 150 mL in a beaker. A beaker cover cut in polystyrene was used to provide access of the microfluidic device to the solution in the beaker. An impeller operated at 500 rpm was used to stir the slurry in the beaker and prevent sedimentation. The microchip experiments were monitored optically. Different flow rates (up to ~1.5 mL/h) were used.

[0076] Online UV-vis absorption (Ocean Optics QE65000) was used to determine the concentration of metal complexes. A Z-Flow Cell (10-mm path length, quartz windows) was directly connected to the outlet of the microchip using FEP tubing. Absorbance measurements were taken at 258 nm for EDTA complexes and interpreted according to Beer's law. Standard aqueous iron solutions (100 mM) were prepared using AR grade FeCl ₃ .6H ₂ O and pure water (18.2 MWcm , Barnstead). Ethylene diamine tetracetic acid disodium salt (EDTA) was obtained from Sigma-Aldrich.

[0077] The slurry sample was a Dugald river lead/zinc ore, with a head grade of 1% lead (as galena),

11% zinc (as sphalerite), and 4% iron (some of which is pyrite and pyrrhotite). The P80 was about 60 mm.

[0078] The slit depth and the flow rate inside the microfluidic channel are the two main factors in determining the cut-off size of the fdter. The slit depth was chosen based on simulation results from ANSYS computational fluid dynamics (CFD) software. By decreasing the slit depth from 50 mm to 25 mm, the extent of the turbulence from the bulk solution decreased, thus lowering its effect on the laminar flow. All experiments were carried out using a slit depth of 25 mm. Lower depths were not explored as roof collapse occurred during the bonding process. In the experiment setup, the flow rate was maintained using two syringe pumps with positive and negative pressures for the inlet and the outlet, respectively. The effect of the flow rate was studied over the range 0.1 -1.5 mL/h with equal flow rates for the inlet and outlet and with up to 20% lower flow rate for the inlet. [0079] Flow rate characterization experiments were done using a 3% ethylene diamine tetracetic acid disodium salt (EDTA) that was spiked with a standard iron III solution every 15 minutes or more depending on the flow rate. The microfluidic device was filled with 3% solution of EDTA. Under the experimental conditions, iron III forms stable complex with EDTA that can be measured at 258 nm using a spectrophotometer and detection in a 10-mm path length quartz cell. Experiments with equal flow rates for the inlet and outlet showed the lowest extraction percentage as demonstrated by the slope in Figure 3 and Table 1. By increasing the % offset in the flow rate from 5 to 20%, the amount of iron extracted increased accordingly. We expect that the difference between the two flow rates was directly withdrawn from the external solution. Consequently, a higher negative pressure is expected at the slit entrance when using high % offset compared to the equal flow rates setup. Experiments with equal flow rates for the inlet and outlet also showed constant response regardless of the flow rate value over the range 0.2- 1.5 mL/h. This means that small variations in the flow rate will not affect the method performance as long as both flows kept similar.

[0080] Table 1 - % Extraction of iron III from 3% EDTA at different flow rates

[0081] Simulations for the different flow rates and experiments using coloured dye as shown in Figure 4 demonstrates the similar behaviour observed when using equal flow rates for the inlet and outlet regardless of the flow rate over the range 0.5-1.5 mL/h. Under flow rate offset conditions, the outlet showed higher velocities and dynamic pressures than the inlet which were proportional to the increase in the % offset.

[0082] The method presented herein can efficiently extract soluble ions from complex samples containing a wide range particle size distribution. We applied the method for the on-line monitoring of iron III content in mineral slurry. In mineral processing, rocks are crushed and ground to a fine powder using steel or ceramic grinding media. While steel grinding media are cheaper to use, the impact during the process leads to high iron III content in the product. Iron III can have detrimental effects on the following flotation process to separate the valuable minerals from waste components. Currently, the operation is majorly based on the judgement of experienced personnel but the exact parameters are not fully monitored or controlled and the processes are not fully understood. Timely decisions based on high quality data will save up to a million dollars per year while decreasing the environmental impact. Using our device, changes in the iron III content can be monitored within 15 minutes, and corrective actions can be taken quickly. Results from spiking a slurry from the Dugald River pulp with standard iron III are shown in Figure 5. The results are for equal flow rates for inlet and outlet at 0.5 and 1.0 mL/h. The results for extraction from slurry align well with the results for the extraction from 3% EDTA.

[0083] Throughout the specification and the claims that follow, unless the context requires otherwise, the words“comprise” and“include” and variations such as“comprising” and“including” will be understood to imply the inclusion of a stated integer or group of integers, but not the exclusion of any other integer or group of integers.

[0084] The reference to any prior art in this specification is not, and should not be taken as, an acknowledgement of any form of suggestion that such prior art forms part of the common general knowledge.

[0085] It will be appreciated by those skilled in the art that the invention is not restricted in its use to the particular application described. Neither is the present invention restricted in its preferred embodiment with regard to the particular elements and/or features described or depicted herein. It will be appreciated that the invention is not limited to the embodiment or embodiments disclosed, but is capable of numerous rearrangements, modifications and substitutions without departing from the scope of the invention as set forth and defined by the following claims.

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