ฝึกพูดภาษาอังกฤษด้วยเทคนิค Shadowing จากวิดีโอ: Introduction to HPLC - Lecture 1: HPLC Basics

เลือกโหมดฝึก

แต่ละโหมดจะเปิดห้องฝึกแบบเต็มจอ

339 ประโยค

หากประโยคสั้นหรือยาวเกินไป กดที่ Edit เพื่อปรับแก้

Hello, everybody.

Welcome to another ChemComplete lecture series.

And today's lecture series, we are going to be introducing an introduction course to HPLC chromatography.

So HPLC stands for High Performance Liquid Chromatography.

And in this first lecture, we're going to take an overview of HPLC

and learn some of the basics and then we will get into more detailed parts as the lecture series continues,

into different types of columns and how to manipulate mobile phases and things of that nature.

So let's go ahead and get started with a general overview.

The first thing that we want to have an understanding of is what chromatography is.

So when we use the term chromatography, we're talking about a separation of compounds.

Now traditionally when chromatography was first discovered,

it was through basically just a separation on silica or alumina type gel.

And you could literally see the colors separating out from these different organic compounds.

And that's where the name chromatography comes from.

The chroma part with the color is referring to that separation where you could visually see colors.

Now in today's more modern labs, we usually have two options when it comes to instrumentation.

The first one is gas chromatographs, which is GC, gas chromatography.

And then the second one, which we will be talking about, is obviously HPLC.

Now, the difference between these is when you want to use GC, certainly you're going to be dealing with things going into a gas phase.

But one of the distinctions is that you need whatever you are putting through the GC to be volatile.

So whatever compounds you're going to work with, they have to be volatile compounds.

And that means that GC tends to be better situated for compounds that have a lower molecular weight.

And that's simply because due to the volatility, compounds with lower molecular weight have fewer intermolecular forces, and therefore they tend to be more volatile.

And then obviously GC is going to be operating at higher temperatures, because whatever volatile compounds we put in there,

we are going to need to push them into the gas phase.

And that requires a higher temperature, both internally in the column and at the injection port where we are injecting our samples.

So on the other hand, if we take a look at HPLC,

HPLC is acceptable for both volatile and you can do non-volatile compounds in HPLC.

Because we're not trying to push things into the gas phase, it's liquid chromatography.

The only thing you really need to worry about is solubility.

Now, solubility is going to be important, especially when we start talking about mobile phases and picking out solvents,

how things adhere to columns and how they are washed off of the columns and how that affects retention time.

One of the other benefits of this is that it's less destructive than gas chromatography is.

You can recover your samples most of the time

if you only have a small amount and you're attempting to purify something by HPLC, that is possible.

And one of the reasons it's also less destructive is most of the time you can run these at room temperature, so around 25 degrees Celsius.

There are no high temperature requirements where you have to move these compounds into a gas phase.

So that's sort of an overview of chromatography, the different methods we have available, and which one might be useful in which case.

So the next thing that we want to ask is how does HPLC actually work?

So now that we know some of the parameters, we want to take a look at how HPLC actually separates compounds and works.

And the way that this occurs is there are two phases that we consider,

and this is usually true of any type of benchtop chromatography as well.

So when we're talking about column chromatography, the original chromatography we mentioned, this is true.

So you're going to have a mobile phase, and as the name implies,

this is going to be a phase involved in the movement of compounds through the column.

And your mobile phase in HPLC is going to be a liquid,

and usually it's some sort of solvent or a mixture of water and organic solvents.

And you can manipulate the polarity of the mobile phase by mixing and matching.

So certainly water, alcohols, those are going to lead to more polar mobile systems, and that will mobilize polar compounds, whereas you can scale it back.

You could go mid-range with something like ethyl acetate or methylene chloride

and then you could scale back even further and

if you really want to get more into the non-polar region you could start working with maybe some hexanes

or some of your ethers where you would have a better movement of your non-polar compounds in a situation like that.

All right so you have the mobile phase and then the other phase that you have is known as the stationary phase.

Now the stationary phase, again by the name, is going to be a phase that is not involved with movement.

It is going to be keeping compounds sort of adhered or stuck where they are.

So this is usually going to be a solid chemical phase,

and this is the material that you're going to find in your column.

So it's solid chemicals that are going to be bound into a column.

Now you may have heard if you've ever experienced HPLC or GC because we use columns in GC as well.

You may have heard of the term column.

The column itself is just a very long tube

and then the columns properties depend on what has been coded inside of the column.

So maybe you've heard of things, and we'll show an example later, something like a C18 column, a C8 column, a C4 column, an ion exchange column.

All of those types of columns are going to have a different interior makeup or a different interior stationary phase,

and that will be responsible for binding the compounds as they're moving through

and you really have sort of a give

and take between the mobile phase and the stationary phase so

when you're doing this you will take your sample it will

be loaded with the auto injector into the column along with some mobile phase

and then your sample will adhere to the stationary phase

so it almost like glue

or some sort of a sticky pad the compounds will adhere to the stationary phase

and then they will slowly be washed along depending on their

preference or their binding to the stationary phase so the mobile phase is pumped through at a steady rate.

And then depending on the polarity of that mobile phase and the polarity of the stationary phase, that will determine how quickly your materials move along the column.

And the goal with HPLC is you want to separate these materials out as best you can.

You don't want them clustering together.

Again, going back to something like a column

that you would be running on a benchtop in an organic synthesis type of manner.

When you have a column like that, the goal is to separate the compounds out into different sort of aliquots of solvent.

You don't want to just bleed all of them down together, otherwise you haven't really done any type of chromatography and separation.

All right, so to do a very simple picture, and we will have a larger visual as we wrap this first lecture portion up in a little bit.

But to give a very simple diagram here, the way that this would work is you have your mobile phase.

Now I'm just going to draw a single container of solvent.

Many times in HPLC, you're going to end up having several different solvents

and the HPLC pumps can mix and match them at different rates.

So let's say it's called a solvent gradient.

I want to start with 50% methanol,

50% water, and then I want to move to 75% methanol five minutes into the run for better separation at that point.

You can tell or program your HPLC to pick

and choose different amounts that it puts through the pump at a given time, all right?

But in general, you're going to have your bottles filled with mobile phase, and the mobile phase is going to be connected, okay, into the HPLC.

It'll go through the pumps.

It also goes through something called a degasser, which we will talk about in a couple of minutes.

But the idea is that eventually, okay, along with your compound that is injected,

it's going to find its way onto the stationary phase, which is your column.

Okay, and in the stationary phase, it's going to, as we described travel along

and separate out at different times

100

and once it comes off of the column it's going to hit the detector

101

so the detector is going to be using usually we use

102

a lot of uv vis you can use a fluorometry type of detector where you're doing fluorescence

103

if you have the proper derivatives and materials

104

but you have to have some way of detecting what's coming off of that stationary phase.

105

And then that is what will be output into a chromatogram.

106

So that's where we see the actual graph.

107

And you've got the peaks as they go along.

108

And those peaks have different tension times.

109

Okay.

110

And again, we'll talk about all of this in a little bit more detail.

111

But the key here is that the compounds are going to travel at different rates.

112

And therefore, they hit the detector at different time periods.

113

And those different times, referred to as retention times is how we can really identify what is coming off of the stationary phase or the column.

114

All right, so a mobile phase is oftentimes going to be a mixture of water

115

and organic solvents when we take a look at it.

116

And the polarity of the mixture or the lack thereof, because you could certainly be working with non-polar ones as well,

117

that will determine how long the compounds are going to stay on the column or adhere to the column, and that's known as retention time.

118

And then the stationary phase, the columns are packed with different materials, usually some sort of organic materials often applied to a silica bed.

119

And those will bind to the compounds that are being separated

120

and sort of spread them out as the mobile phase is going through doing its thing.

121

All right.

122

So one of the things I mentioned here was there are different types of material that get packed in your columns.

123

And as the chemist, you have to decide what type of column you want to pick out in order to get the best separation.

124

And each of those can go into their own lecture.

125

So we can talk about, and we will make a list,

126

but we can talk about things such as ion exchange or reverse phase or normal phase HPLC.

127

Those all have different meanings.

128

They have different type of mobile phase and stationary phase setups.

129

all right but for example

130

if we were to talk about using a c18 column a

131

c18 column I'm drawing the inside of the column here okay

132

so imagine that this is the inside of the column what you would find is a silica binding portion

133

that sort of lines the bed of the column okay now a lot of times

134

when we do wet bench sort of a desktop chromatography we use silica gel right

135

or alumina so you have this as the base

136

and then once you have your silica gel you can adhere other types of organic material to the side

137

so what you end up with is in a c18 column, you get very long 18 membered carbon chains.

138

So what I'm going to write here is CH2.

139

We have 17 of those, and then the 18th is going to be a CH3, right?

140

And then you would see that at every single silica site, all right?

141

So it's going to get a little crowded here, but I'll draw another one, all right?

142

So you'd go like this.

143

You have the silica with the two methyl groups, and then you would have a CH2, right?

144

And you have 17 of those and a methyl.

145

So you have these very, very long hydrophobic, and that's important in a case like this, okay, hydrophobic chains.

146

And I mentioned that that's important because you could also have a hydrophilic or a polar type of chain.

147

This one in particular is going to have better adherence to other nonpolar compounds.

148

All right.

149

And it would sort of go on where throughout the column you would have this type of a binding site.

150

And as the materials come through, they interact through intermolecular forces with these other compounds here,

151

right, these long chains that are hydrophobic.

152

And that sort of adheres your organic materials to the column.

153

And the mobile phase will sort of push them along

154

and depending on how strongly they adhere to it

155

that is going to be what determines how quickly they will come off of the column

156

which is relating to retention time there so

157

for something like a c18 you're dealing with a highly non-polar column

158

so non-polar analytes are going to be retained at a longer

159

rate right they're going to stay on the column longer before they get pushed off onto the detector.

160

Now this is very important the choice of column

161

and solvent phases will always play a role in your separations

162

and you want to basically maximize the efficiency of those separations

163

which again could be its own lecture in terms of how

164

do we maximize retention time how do we get good resolution

165

so the peaks aren't too clustered together and we'll address that as we go along in this course.

166

So what are some of the modes of HPLC

167

that we can talk about because if you remember I mentioned

168

that there are several modes

169

and each one of them could have their own lecture in terms of what's involved

170

so the first mode that we would talk about is just normal okay

171

and for a normal phase you would usually be talking about

172

a situation where the column is more polar than the mobile phase

173

so the mobile phase is going to be non-polar in that case

174

and the column is going to be more polar okay one of the other very common ones is reverse phase

175

okay c18s tend to be used in reverse phase a lot

176

and with a reverse phase HPLC it's just the opposite of what we said

177

so something like a c18 you have a very non-polar column

178

but then your mobile phase tends to be more polar

179

so you might have methanol acetonitrile water things of

180

that nature in different ratios okay then you've got some other ones when you start dealing with ion pair.

181

Okay, so you can have an ion pair and you can also have an ion exchange phase.

182

And then one of the last ones that sometimes gets mentioned is you can also have a size exclusion chromatography.

183

Okay, so each of these has their own unique way of dealing with stuff.

184

So sometimes when you're dealing with the ion exchange columns, you might be using some sort of a buffer, like a sodium buffer at different concentrations.

185

Whereas when you're doing just the regular phase or the reverse phase, you're using water and organic solvents instead of a salt or a buffer system.

186

All right, so each of these is its own lecture, as I mentioned, but I did want to list these here so that we could sort of talk about them briefly

187

and give you an idea of some of the upcoming content.

188

We will cover each of these in its own right, but it'll be its own probably 20-minute,

189

30-minute lecture dealing with everything that goes into each one of these types of phases.

190

So with that being said, what I want to do, I want to bring up an image here

191

as we get ready to start wrapping up this first lecture

192

and really go through each of the parts of an HPLC

193

because it's one thing to talk about it in theory with

194

this sort of like simple drawing I have up here in blue.

195

But it's another thing when you actually walk into a lab and you see the HPLC,

196

there's a lot of containers or boxes for this instrument that are sort of stacked on top of one another.

197

So I made a rough sketch of an HPLC setup.

198

It's very generalized, but it'll get the point across as we're talking about this.

199

So let me bring that up and we'll take a look at

200

that together okay

201

so here we are we have the setup for what the HPLC would ideally look like

202

if we had the system

203

and we could kind of briefly look at the insides again this is still a simplified drawing

204

but it's more detailed than what I showed a few minutes ago

205

so the very top part here you can see the bottles

206

that are hanging out at the top this is where you're going to find your mobile phase components okay

207

so these are your solvents your water whatever it might be it could be your buffer solutions

208

but your mobile phase is usually found at the top of the HPLC instrument

209

and it will be in you know maybe four liter solvent

210

bottles it might be in a one liter plastic container again

211

most of the time you're going to see multiple containers

212

because many HPLC techniques use what's called a gradient solvent system where you're changing it over time

213

and either increasing or decreasing the polarity at certain time markings on the column.

214

So that's what's being hosted at the top there where you see the different colored bottles.

215

Those are your mobile phases.

216

So the mobile phases send the liquids into the next component, and that's the component we see right here,

217

and that is known as a degasser.

218

Now, a degasser has one simple job, and that is literally to degas the solution.

219

So the degasser, as it accepts the mobile phase, these solvents, it's attempting to remove any air bubbles

220

or any sort of air pockets that might be found in your mobile phase, because you cannot have,

221

or you certainly don't want to have air pockets as you're going along in your column

222

because that can disrupt the flow and the rate at which these components come out.

223

It can screw up your baseline particularly.

224

So having a good degassing system is crucial in making sure

225

that you establish a steady baseline and you have nice clean separation of peaks

226

when they finally hit the detector and you get your chromatogram.

227

So the mobile phase is pumped into the degasser and after any type of air is removed,

228

this liquid comes down and is sent to the pump system.

229

So these are the pumps.

230

Now, when you have your HPLC pumps, they use a back pressure in order to continuously,

231

and it is very important that it's continuous and at a steady rate,

232

move the mobile phase down through the rest of the HPLC system across the column and into the detector.

233

And it's important that your pumps are in good shape in order to maintain this regular flow, okay, which you could call the flow rate of solvent.

234

You can adjust how quickly these pumps are working and what pressure in order to change the flow rate.

235

When you change the flow rate, you obviously change how quickly or slowly things will come off of your column and hit the detector.

236

So changing any of your pump settings will be able to change the retention times for the compounds.

237

So sometimes that can be a good thing, sometimes that can be a bad thing.

238

But you've got your pumps, they are going to help mix these mobile phases

239

and then pump them down and get them ready to go into the stationary phase.

240

All right, so after the pumps have thoroughly mixed it, it's going to come in to the next part of the HPLC in

241

which we have the mixing for the auto sampler and the injector.

242

All right, so what you see on the left over here is your auto sampler, or at least my best representation of one.

243

and the auto sampler is going to take your samples.

244

So these little blue vials here are your samples.

245

You've processed them in a lab.

246

You've been given these samples.

247

You put them into a rack.

248

You load that into the auto sampler.

249

And then through the software, the auto sampler will come, pick up, give an amount.

250

You can choose the injection amount.

251

It's usually a tiny amount like five uh not 550 to 100 microliters excuse me

252

and that will send this material

253

and mix it right into the injection port where it will also meet up with the mobile phase

254

and that will be sent down into the column.

255

So that's the next part right here, right?

256

After everything is thoroughly mixed, it is sent down and your material from the autoloader is going to adhere to the column

257

and then your pump is doing its thing.

258

It's continuously pushing the mobile phase along.

259

so your materials will start traveling on the inside of your column at a given rate right

260

and we've talked about the inside of the column and how

261

that works the adherence

262

and then at some point they will come off of the column they will be sent down into the detector

263

so again your detector could be fluorescence it could be uv those are probably the two most common

264

but when you hit the detector

265

that is where the signals are going to be received

266

and then you can output into a chromatogram and

267

when you get to the chromatogram that's the actual printout

268

that you would be looking at where you have the peaks

269

and their retention times and that is the final step for the HPLC at

270

that point you would be using software in order to analyze your actual chromatogram okay

271

so a general chromatogram is going to look something like this you're going to have

272

so along the y-axis you're going to usually some see some

273

sort of a response okay usually it's just called abundance

274

or detector response or something of that nature and then on the x-axis you're going to see the time.

275

This is typically in minutes.

276

It could be in a different unit depending on how you set it up, but it's almost always seen in minutes.

277

And so you have your baseline.

278

Again, to have a steady baseline, you need to make sure that you've got a good degasser for your mobile phase.

279

And then at some point, you're going to see, if you have compound, peaks that start coming off.

280

Okay, now you might just have one peak if it's a pure substance, but most of the time

281

when you're doing HPLC it's to separate out several components from one another right

282

so you can see an example like this now there's two important parts here

283

and that is you have what's called T naught or T zero

284

which is the initial amount of time that it takes for anything

285

that has not adhered to the column to just come out

286

and directly be flushed okay so there is a compound called uracil

287

that is typically utilized in order to detect when this hits however again t-naught is going to be the elution time

288

for anything that was not retained so for unretained material

289

and when you have that sometimes you'll hear it called

290

or referred to as dead time again this is simply time

291

that elapses when you have essentially the first dump of mobile phase into the detector

292

that did not have any type of adherence to the column.

293

All right, so the other important thing that we've been talking about over and over again is the retention time.

294

Now, this goes certainly beyond the dead time that we have there out to whatever peak you're currently looking at.

295

So let's say that we're looking at this last peak right here,

296

the amount of time that it takes to go from the dead time out here is TR,

297

and that is considered to be the time of retention.

298

Now, when we start talking about things like resolution and the distance between peaks, it's going to be important to understand both of these,

299

because both of these components are used in calculating how to improve things like resolution okay

300

but retention time okay and what's important about retention time

301

and i know i mentioned this once earlier is

302

that this is really we can identify compounds by retention time

303

so the compound identity is associated by retention time and that's really how we look at compounds when we do HPLC.

304

Now one of the other things that we discuss with HPLC is we do discuss the area under the peak.

305

So the retention time kind of identifies what compound we're working with.

306

The area under the peak is going to tell us how much of that compound there is.

307

Okay so there's essentially the area under the peak is going to be proportional to the analyte amount.

308

Now the way that you determine this

309

because you have to have something to compare it to is that you would need to use a calibration curve.

310

So let's say that I'm working with amino acids and I want to analyze the amount of lysine.

311

So if I'm going to analyze the amount of lysine, I need to have a calibration curve of lysine at several different concentrations.

312

And then ideally, I want

313

that range to cover from min to max any type of sample of lysine that I might be expecting.

314

So it can be a little bit of trial and error

315

when you're first setting up your calibration curve if you don't know a whole lot about your samples.

316

But once you have a reliable one, you'll know the area under the peak for the various concentrations of your lysine,

317

and therefore you would be able to determine the amount based on any sort of unknown sample going through.

318

And you always know that it's lysine based on the retention time.

319

So that would just be a example there.

320

All right, so we're closing in on half an hour.

321

I think I'm going to wrap it up there in terms of the introduction to HPLC,

322

and we will continue forward with these lessons and start to outline some more detailed parts to the HPLC,

323

particularly the different types of phases that we can undergo, as well as some troubleshooting stuff.

324

So what happens if all my peaks are too close together?

325

How can I improve that?

326

Things of that nature.

327

So hopefully everybody found this introduction course to be useful.

328

I hope that we will see you for continued courses as always remember to hit the like button

329

because that really helps with the YouTube out YouTube algorithms

330

and promoting the content so I can get more out to you the more

331

that the channel is supported and head over to chem complete calm

332

because we have guides that I have personally written over there

333

and you can pick them up just for a few dollars it helps to support the channel

334

so I can keep bringing you guys free content like this.

335

So other than that, I hope everybody has a fantastic rest of the day.

336

Please don't be afraid to leave comments if you have any questions

337

and hit the subscribe notification bell if you want to be up to date anytime I release these lectures.

338

So I will see everybody for the next lecture.

339

Thanks a lot, guys.

ดาวน์โหลดแอป

ทุกอย่างที่ต้องใช้เพื่อพูดได้คล่อง

AI ให้คะแนนการออกเสียงให้คะแนนทุกประโยค

ฝึก IPAเชี่ยวชาญทุกเสียง

คำศัพท์สร้างคลังคำของคุณ

เกมคำศัพท์เล่นไปเรียนไป

สแกน QR

Download on theApp Store Get it onGoogle Play

FOR YOU

วิดีโอแนะนำ

76 ประโยค

Module 1: What is Supply Chain Management? (ASU-WPC-SCM) - ASU's W. P. Carey School

Daily ConversationUniversity Students

21 ประโยค

Introduction

Daily ConversationUniversity Students

162 ประโยค

Introduction to PLC | Siemens PLC Training Course

Daily ConversationUniversity Students

72 ประโยค

Overview of Fluid and Electrolyte Physiology (Fluid Compartment)

Daily ConversationUniversity Students

195 ประโยค

VETERINARY BASICS: How to read a blood test! CBC & Haematology

Daily ConversationUniversity Students

81 ประโยค

What are substances made of ? | Lesson 5: MOLECULES—SIMPLE SUBSTANCES&COMPOUNDS | Science in English

Daily ConversationUniversity Students

105 ประโยค

What are Capital Markets? | Intro to Capital Markets (Part 1)

Daily ConversationUniversity Students

คำศัพท์และข้อสังเกตด้านการพูดสำหรับบทเรียนนี้

วิดีโอนี้มี 339 ประโยค และ 4721 คำ สำหรับฝึกพูดตาม ช่วงที่มีเสียงพูดยาว 30:07 ผู้พูดพูดด้วยความเร็วเป็นธรรมชาติ ประมาณ 157 คำต่อนาที ใกล้เคียงกับบทสนทนาในชีวิตประจำวัน 83% ของคำอยู่ใน 3,000 คำที่ใช้บ่อยที่สุดในภาษาอังกฤษ ส่วนที่เหลือควรดูไว้ก่อนเริ่มฝึก

คำศัพท์สำคัญในวิดีโอนี้

คำที่ควรเรียนรู้ 15 คำจากวิดีโอ พร้อมคำอ่านและความหมาย:

คำศัพท์	คำอ่าน	ความหมาย
column คำนาม	/ˈkɒləm/	เสา
compound คำนาม	/ˈkɑmpaʊnd/	สารประกอบ
pump คำนาม	/pʌmp/	เครื่องสูบลม, เครื่องสูบน้ำ
lecture คำนาม	/ˈlɛk.t͡ʃə/	การบรรยาย, เล็กเชอร์
adhere คำกริยา	/ædˈhɪə/	ติด
organic คำคุณศัพท์	/ɔːˈɡænɪk/	อินทรีย์
automobile คำนาม	/ˈɔː.tə.məˌbil/	รถยนต์, รถ
volatile คำคุณศัพท์	/ˈvɑ.lə.təl/	ลบเลือนได้
liquid คำนาม	/ˈlɪk.wɪd/	ของเหลว
steady คำคุณศัพท์	/ˈstɪdi/	มั่นคง
container คำนาม	/kənˈteɪ.nəɹ/	บรรจุภัณฑ์, หีบห่อ
wrap คำกริยา	/ɹæp/	ห่อ
injection คำนาม	/ɪnˈd͡ʒɛk.ʃən/	การฉีดยา, ฉีดยา
analyze คำกริยา	/ˈæn.əˌlaɪz/	วิเคราะห์
pocket คำนาม	/ˈpɑ.kɪt/	กระเป๋า

กริยาวลีที่คุณจะได้ยิน

คำศัพท์	ความหมาย
bring up คำกริยา	เลี้ยงดู, ฟูมฟัก
pick up คำกริยา	ยก, หยิบ

ไวยากรณ์ในวิดีโอนี้

โครงสร้างที่ผู้พูดใช้บ่อยที่สุด พร้อมคำพูดจริงจากวิดีโอ:

โครงสร้าง	ในวิดีโอ
Passive voice be + กริยาช่อง 3 — เน้นสิ่งที่เกิดขึ้น ไม่ใช่ผู้กระทำ	are washed · have is known · is not involved
Present perfect have/has + กริยาช่อง 3 — เหตุการณ์ในอดีตที่ยังเกี่ยวข้องกับปัจจุบัน	you've ever experienced · has been coded · you've heard
Relative clauses who / which + อนุประโยค — ข้อมูลเพิ่มเติมเกี่ยวกับคนหรือสิ่งของ	chromatographs, which is · phase, which is

การออกเสียงที่ควรระวัง

ผู้พูดใช้รูปย่อและรูปลดเสียง 68 ครั้ง เช่น you're, we're, you've ให้พูดแบบสั้นตามที่ได้ยิน

เสียง “th”: thoroughly /ˈθʌɹ.ə.li/, algorithm /ˈælɡəɹɪðm̩/, synthesis /ˈsɪnθəsɪs/, thereof /ðɛˈɹʌv/, methanol /ˈmɛθənɒl/
เสียง “sh” และ “zh”: retention /ɹɪˈtɛnʃən/, stationary /ˈsteɪʃəˌnɛɹi/, separation /ˌsɛp.əˈɹeɪ.ʃən/, concentration /ˌkɑn.sənˈtɹeɪ.ʃən/, injection /ɪnˈd͡ʒɛk.ʃən/
คำยาว — ลงเสียงหนักให้ถูกพยางค์: stationary /ˈsteɪʃəˌnɛɹi/, separation /ˌsɛp.əˈɹeɪ.ʃən/, automobile /ˈɔː.tə.məˌbil/, concentration /ˌkɑn.sənˈtɹeɪ.ʃən/, essentially /ɪˈsɛnʃəli/

วิธีฝึกกับวิดีโอนี้

ฟังวิดีโอให้จบหนึ่งรอบโดยยังไม่ต้องพูด แล้วจดคำที่ยังไม่รู้จัก
เริ่มที่ความเร็ว 0.75× พูดตามทีละประโยค แล้วกลับไปใช้ความเร็วปกติเมื่อเริ่มคล่อง
อัดเสียงตัวเองแล้วเทียบกับต้นฉบับ โดยสังเกตคำอย่าง column, compound, pump เป็นพิเศษ

เทคนิค Shadowing คืออะไร?

Shadowing เป็นเทคนิคการเรียนรู้ภาษาที่ได้รับการรับรองทางวิทยาศาสตร์ พัฒนาขึ้นสำหรับการฝึกนักแปลมืออาชีพ วิธีการนี้เรียบง่ายแต่ทรงพลัง: คุณฟังเสียงภาษาอังกฤษจากเจ้าของภาษาและพูดตามทันที — เหมือนเงาที่ตามผู้พูดด้วยช่วงเวลาห่าง 1-2 วินาที การวิจัยแสดงว่าเทคนิคนี้ปรับปรุงความแม่นยำในการออกเสียง ทำนองเสียง จังหวะ การเชื่อมเสียง การฟังเข้าใจ และความคล่องแคล่วในการพูดได้อย่างมีนัยสำคัญ

เทคนิค shadowing: อ่านคู่มือฉบับเต็มทีละขั้นตอน →

ฝึกพูดภาษาอังกฤษด้วยเทคนิค Shadowing จากวิดีโอ: Introduction to HPLC - Lecture 1: HPLC Basics

เลือกโหมดฝึก

ดาวน์โหลดแอป

GC FID Operational Tutorial

Phonetics and Phonology: Introduction

How Distillation Columns Separate Chemicals

Free CCNA | VLANs (Part 2) | Day 17 | CCNA 200-301 Complete Course

Glycolysis

Module 1: What is Supply Chain Management? (ASU-WPC-SCM) - ASU's W. P. Carey School

Introduction

Introduction to PLC | Siemens PLC Training Course

Overview of Fluid and Electrolyte Physiology (Fluid Compartment)

VETERINARY BASICS: How to read a blood test! CBC & Haematology

What are substances made of ? | Lesson 5: MOLECULES—SIMPLE SUBSTANCES&COMPOUNDS | Science in English

What are Capital Markets? | Intro to Capital Markets (Part 1)

คำศัพท์และข้อสังเกตด้านการพูดสำหรับบทเรียนนี้

คำศัพท์สำคัญในวิดีโอนี้

กริยาวลีที่คุณจะได้ยิน

ไวยากรณ์ในวิดีโอนี้

การออกเสียงที่ควรระวัง

วิธีฝึกกับวิดีโอนี้

เทคนิค Shadowing คืออะไร?