Network polymers derived from the integration of flexible organic polymers an...Berkay AKKOÇ
Network polymers derived from the integration of flexible organic polymers and rigid metal organic frameworks. My class notes about a kind of inorganic polymer. Review.
2024 State of Marketing Report – by HubspotMarius Sescu
https://www.hubspot.com/state-of-marketing
· Scaling relationships and proving ROI
· Social media is the place for search, sales, and service
· Authentic influencer partnerships fuel brand growth
· The strongest connections happen via call, click, chat, and camera.
· Time saved with AI leads to more creative work
· Seeking: A single source of truth
· TLDR; Get on social, try AI, and align your systems.
· More human marketing, powered by robots
ChatGPT is a revolutionary addition to the world since its introduction in 2022. A big shift in the sector of information gathering and processing happened because of this chatbot. What is the story of ChatGPT? How is the bot responding to prompts and generating contents? Swipe through these slides prepared by Expeed Software, a web development company regarding the development and technical intricacies of ChatGPT!
Product Design Trends in 2024 | Teenage EngineeringsPixeldarts
The realm of product design is a constantly changing environment where technology and style intersect. Every year introduces fresh challenges and exciting trends that mold the future of this captivating art form. In this piece, we delve into the significant trends set to influence the look and functionality of product design in the year 2024.
How Race, Age and Gender Shape Attitudes Towards Mental HealthThinkNow
Mental health has been in the news quite a bit lately. Dozens of U.S. states are currently suing Meta for contributing to the youth mental health crisis by inserting addictive features into their products, while the U.S. Surgeon General is touring the nation to bring awareness to the growing epidemic of loneliness and isolation. The country has endured periods of low national morale, such as in the 1970s when high inflation and the energy crisis worsened public sentiment following the Vietnam War. The current mood, however, feels different. Gallup recently reported that national mental health is at an all-time low, with few bright spots to lift spirits.
To better understand how Americans are feeling and their attitudes towards mental health in general, ThinkNow conducted a nationally representative quantitative survey of 1,500 respondents and found some interesting differences among ethnic, age and gender groups.
Technology
For example, 52% agree that technology and social media have a negative impact on mental health, but when broken out by race, 61% of Whites felt technology had a negative effect, and only 48% of Hispanics thought it did.
While technology has helped us keep in touch with friends and family in faraway places, it appears to have degraded our ability to connect in person. Staying connected online is a double-edged sword since the same news feed that brings us pictures of the grandkids and fluffy kittens also feeds us news about the wars in Israel and Ukraine, the dysfunction in Washington, the latest mass shooting and the climate crisis.
Hispanics may have a built-in defense against the isolation technology breeds, owing to their large, multigenerational households, strong social support systems, and tendency to use social media to stay connected with relatives abroad.
Age and Gender
When asked how individuals rate their mental health, men rate it higher than women by 11 percentage points, and Baby Boomers rank it highest at 83%, saying it’s good or excellent vs. 57% of Gen Z saying the same.
Gen Z spends the most amount of time on social media, so the notion that social media negatively affects mental health appears to be correlated. Unfortunately, Gen Z is also the generation that’s least comfortable discussing mental health concerns with healthcare professionals. Only 40% of them state they’re comfortable discussing their issues with a professional compared to 60% of Millennials and 65% of Boomers.
Race Affects Attitudes
As seen in previous research conducted by ThinkNow, Asian Americans lag other groups when it comes to awareness of mental health issues. Twenty-four percent of Asian Americans believe that having a mental health issue is a sign of weakness compared to the 16% average for all groups. Asians are also considerably less likely to be aware of mental health services in their communities (42% vs. 55%) and most likely to seek out information on social media (51% vs. 35%).
AI Trends in Creative Operations 2024 by Artwork Flow.pdfmarketingartwork
This article is all about what AI trends will emerge in the field of creative operations in 2024. All the marketers and brand builders should be aware of these trends for their further use and save themselves some time!
Network polymers derived from the integration of flexible organic polymers an...Berkay AKKOÇ
Network polymers derived from the integration of flexible organic polymers and rigid metal organic frameworks. My class notes about a kind of inorganic polymer. Review.
2024 State of Marketing Report – by HubspotMarius Sescu
https://www.hubspot.com/state-of-marketing
· Scaling relationships and proving ROI
· Social media is the place for search, sales, and service
· Authentic influencer partnerships fuel brand growth
· The strongest connections happen via call, click, chat, and camera.
· Time saved with AI leads to more creative work
· Seeking: A single source of truth
· TLDR; Get on social, try AI, and align your systems.
· More human marketing, powered by robots
ChatGPT is a revolutionary addition to the world since its introduction in 2022. A big shift in the sector of information gathering and processing happened because of this chatbot. What is the story of ChatGPT? How is the bot responding to prompts and generating contents? Swipe through these slides prepared by Expeed Software, a web development company regarding the development and technical intricacies of ChatGPT!
Product Design Trends in 2024 | Teenage EngineeringsPixeldarts
The realm of product design is a constantly changing environment where technology and style intersect. Every year introduces fresh challenges and exciting trends that mold the future of this captivating art form. In this piece, we delve into the significant trends set to influence the look and functionality of product design in the year 2024.
How Race, Age and Gender Shape Attitudes Towards Mental HealthThinkNow
Mental health has been in the news quite a bit lately. Dozens of U.S. states are currently suing Meta for contributing to the youth mental health crisis by inserting addictive features into their products, while the U.S. Surgeon General is touring the nation to bring awareness to the growing epidemic of loneliness and isolation. The country has endured periods of low national morale, such as in the 1970s when high inflation and the energy crisis worsened public sentiment following the Vietnam War. The current mood, however, feels different. Gallup recently reported that national mental health is at an all-time low, with few bright spots to lift spirits.
To better understand how Americans are feeling and their attitudes towards mental health in general, ThinkNow conducted a nationally representative quantitative survey of 1,500 respondents and found some interesting differences among ethnic, age and gender groups.
Technology
For example, 52% agree that technology and social media have a negative impact on mental health, but when broken out by race, 61% of Whites felt technology had a negative effect, and only 48% of Hispanics thought it did.
While technology has helped us keep in touch with friends and family in faraway places, it appears to have degraded our ability to connect in person. Staying connected online is a double-edged sword since the same news feed that brings us pictures of the grandkids and fluffy kittens also feeds us news about the wars in Israel and Ukraine, the dysfunction in Washington, the latest mass shooting and the climate crisis.
Hispanics may have a built-in defense against the isolation technology breeds, owing to their large, multigenerational households, strong social support systems, and tendency to use social media to stay connected with relatives abroad.
Age and Gender
When asked how individuals rate their mental health, men rate it higher than women by 11 percentage points, and Baby Boomers rank it highest at 83%, saying it’s good or excellent vs. 57% of Gen Z saying the same.
Gen Z spends the most amount of time on social media, so the notion that social media negatively affects mental health appears to be correlated. Unfortunately, Gen Z is also the generation that’s least comfortable discussing mental health concerns with healthcare professionals. Only 40% of them state they’re comfortable discussing their issues with a professional compared to 60% of Millennials and 65% of Boomers.
Race Affects Attitudes
As seen in previous research conducted by ThinkNow, Asian Americans lag other groups when it comes to awareness of mental health issues. Twenty-four percent of Asian Americans believe that having a mental health issue is a sign of weakness compared to the 16% average for all groups. Asians are also considerably less likely to be aware of mental health services in their communities (42% vs. 55%) and most likely to seek out information on social media (51% vs. 35%).
AI Trends in Creative Operations 2024 by Artwork Flow.pdfmarketingartwork
This article is all about what AI trends will emerge in the field of creative operations in 2024. All the marketers and brand builders should be aware of these trends for their further use and save themselves some time!
A report by thenetworkone and Kurio.
The contributing experts and agencies are (in an alphabetical order): Sylwia Rytel, Social Media Supervisor, 180heartbeats + JUNG v MATT (PL), Sharlene Jenner, Vice President - Director of Engagement Strategy, Abelson Taylor (USA), Alex Casanovas, Digital Director, Atrevia (ES), Dora Beilin, Senior Social Strategist, Barrett Hoffher (USA), Min Seo, Campaign Director, Brand New Agency (KR), Deshé M. Gully, Associate Strategist, Day One Agency (USA), Francesca Trevisan, Strategist, Different (IT), Trevor Crossman, CX and Digital Transformation Director; Olivia Hussey, Strategic Planner; Simi Srinarula, Social Media Manager, The Hallway (AUS), James Hebbert, Managing Director, Hylink (CN / UK), Mundy Álvarez, Planning Director; Pedro Rojas, Social Media Manager; Pancho González, CCO, Inbrax (CH), Oana Oprea, Head of Digital Planning, Jam Session Agency (RO), Amy Bottrill, Social Account Director, Launch (UK), Gaby Arriaga, Founder, Leonardo1452 (MX), Shantesh S Row, Creative Director, Liwa (UAE), Rajesh Mehta, Chief Strategy Officer; Dhruv Gaur, Digital Planning Lead; Leonie Mergulhao, Account Supervisor - Social Media & PR, Medulla (IN), Aurelija Plioplytė, Head of Digital & Social, Not Perfect (LI), Daiana Khaidargaliyeva, Account Manager, Osaka Labs (UK / USA), Stefanie Söhnchen, Vice President Digital, PIABO Communications (DE), Elisabeth Winiartati, Managing Consultant, Head of Global Integrated Communications; Lydia Aprina, Account Manager, Integrated Marketing and Communications; Nita Prabowo, Account Manager, Integrated Marketing and Communications; Okhi, Web Developer, PNTR Group (ID), Kei Obusan, Insights Director; Daffi Ranandi, Insights Manager, Radarr (SG), Gautam Reghunath, Co-founder & CEO, Talented (IN), Donagh Humphreys, Head of Social and Digital Innovation, THINKHOUSE (IRE), Sarah Yim, Strategy Director, Zulu Alpha Kilo (CA).
Trends In Paid Search: Navigating The Digital Landscape In 2024Search Engine Journal
The search marketing landscape is evolving rapidly with new technologies, and professionals, like you, rely on innovative paid search strategies to meet changing demands.
It’s important that you’re ready to implement new strategies in 2024.
Check this out and learn the top trends in paid search advertising that are expected to gain traction, so you can drive higher ROI more efficiently in 2024.
You’ll learn:
- The latest trends in AI and automation, and what this means for an evolving paid search ecosystem.
- New developments in privacy and data regulation.
- Emerging ad formats that are expected to make an impact next year.
Watch Sreekant Lanka from iQuanti and Irina Klein from OneMain Financial as they dive into the future of paid search and explore the trends, strategies, and technologies that will shape the search marketing landscape.
If you’re looking to assess your paid search strategy and design an industry-aligned plan for 2024, then this webinar is for you.
5 Public speaking tips from TED - Visualized summarySpeakerHub
From their humble beginnings in 1984, TED has grown into the world’s most powerful amplifier for speakers and thought-leaders to share their ideas. They have over 2,400 filmed talks (not including the 30,000+ TEDx videos) freely available online, and have hosted over 17,500 events around the world.
With over one billion views in a year, it’s no wonder that so many speakers are looking to TED for ideas on how to share their message more effectively.
The article “5 Public-Speaking Tips TED Gives Its Speakers”, by Carmine Gallo for Forbes, gives speakers five practical ways to connect with their audience, and effectively share their ideas on stage.
Whether you are gearing up to get on a TED stage yourself, or just want to master the skills that so many of their speakers possess, these tips and quotes from Chris Anderson, the TED Talks Curator, will encourage you to make the most impactful impression on your audience.
See the full article and more summaries like this on SpeakerHub here: https://speakerhub.com/blog/5-presentation-tips-ted-gives-its-speakers
See the original article on Forbes here:
http://www.forbes.com/forbes/welcome/?toURL=http://www.forbes.com/sites/carminegallo/2016/05/06/5-public-speaking-tips-ted-gives-its-speakers/&refURL=&referrer=#5c07a8221d9b
ChatGPT and the Future of Work - Clark Boyd Clark Boyd
Everyone is in agreement that ChatGPT (and other generative AI tools) will shape the future of work. Yet there is little consensus on exactly how, when, and to what extent this technology will change our world.
Businesses that extract maximum value from ChatGPT will use it as a collaborative tool for everything from brainstorming to technical maintenance.
For individuals, now is the time to pinpoint the skills the future professional will need to thrive in the AI age.
Check out this presentation to understand what ChatGPT is, how it will shape the future of work, and how you can prepare to take advantage.
A brief introduction to DataScience with explaining of the concepts, algorithms, machine learning, supervised and unsupervised learning, clustering, statistics, data preprocessing, real-world applications etc.
It's part of a Data Science Corner Campaign where I will be discussing the fundamentals of DataScience, AIML, Statistics etc.
Time Management & Productivity - Best PracticesVit Horky
Here's my presentation on by proven best practices how to manage your work time effectively and how to improve your productivity. It includes practical tips and how to use tools such as Slack, Google Apps, Hubspot, Google Calendar, Gmail and others.
The six step guide to practical project managementMindGenius
The six step guide to practical project management
If you think managing projects is too difficult, think again.
We’ve stripped back project management processes to the
basics – to make it quicker and easier, without sacrificing
the vital ingredients for success.
“If you’re looking for some real-world guidance, then The Six Step Guide to Practical Project Management will help.”
Dr Andrew Makar, Tactical Project Management
Unlocking the Power of ChatGPT and AI in Testing - A Real-World Look, present...Applitools
During this webinar, Anand Bagmar demonstrates how AI tools such as ChatGPT can be applied to various stages of the software development life cycle (SDLC) using an eCommerce application case study. Find the on-demand recording and more info at https://applitools.info/b59
Key takeaways:
• Learn how to use ChatGPT to add AI power to your testing and test automation
• Understand the limitations of the technology and where human expertise is crucial
• Gain insight into different AI-based tools
• Adopt AI-based tools to stay relevant and optimize work for developers and testers
* ChatGPT and OpenAI belong to OpenAI, L.L.C.
More than Just Lines on a Map: Best Practices for U.S Bike Routes
This session highlights best practices and lessons learned for U.S. Bike Route System designation, as well as how and why these routes should be integrated into bicycle planning at the local and regional level.
Presenters:
Presenter: Kevin Luecke Toole Design Group
Co-Presenter: Virginia Sullivan Adventure Cycling Association
Ride the Storm: Navigating Through Unstable Periods / Katerina Rudko (Belka G...DevGAMM Conference
Has your project been caught in a storm of deadlines, clashing requirements, and the need to change course halfway through? If yes, then check out how the administration team navigated through all of this, relocating 160 people from 3 countries and opening 2 offices during the most turbulent time in the last 20 years. Belka Games’ Chief Administrative Officer, Katerina Rudko, will share universal approaches and life hacks that can help your project survive unstable periods when there seem to be too many tasks and a lack of time and people.
A report by thenetworkone and Kurio.
The contributing experts and agencies are (in an alphabetical order): Sylwia Rytel, Social Media Supervisor, 180heartbeats + JUNG v MATT (PL), Sharlene Jenner, Vice President - Director of Engagement Strategy, Abelson Taylor (USA), Alex Casanovas, Digital Director, Atrevia (ES), Dora Beilin, Senior Social Strategist, Barrett Hoffher (USA), Min Seo, Campaign Director, Brand New Agency (KR), Deshé M. Gully, Associate Strategist, Day One Agency (USA), Francesca Trevisan, Strategist, Different (IT), Trevor Crossman, CX and Digital Transformation Director; Olivia Hussey, Strategic Planner; Simi Srinarula, Social Media Manager, The Hallway (AUS), James Hebbert, Managing Director, Hylink (CN / UK), Mundy Álvarez, Planning Director; Pedro Rojas, Social Media Manager; Pancho González, CCO, Inbrax (CH), Oana Oprea, Head of Digital Planning, Jam Session Agency (RO), Amy Bottrill, Social Account Director, Launch (UK), Gaby Arriaga, Founder, Leonardo1452 (MX), Shantesh S Row, Creative Director, Liwa (UAE), Rajesh Mehta, Chief Strategy Officer; Dhruv Gaur, Digital Planning Lead; Leonie Mergulhao, Account Supervisor - Social Media & PR, Medulla (IN), Aurelija Plioplytė, Head of Digital & Social, Not Perfect (LI), Daiana Khaidargaliyeva, Account Manager, Osaka Labs (UK / USA), Stefanie Söhnchen, Vice President Digital, PIABO Communications (DE), Elisabeth Winiartati, Managing Consultant, Head of Global Integrated Communications; Lydia Aprina, Account Manager, Integrated Marketing and Communications; Nita Prabowo, Account Manager, Integrated Marketing and Communications; Okhi, Web Developer, PNTR Group (ID), Kei Obusan, Insights Director; Daffi Ranandi, Insights Manager, Radarr (SG), Gautam Reghunath, Co-founder & CEO, Talented (IN), Donagh Humphreys, Head of Social and Digital Innovation, THINKHOUSE (IRE), Sarah Yim, Strategy Director, Zulu Alpha Kilo (CA).
Trends In Paid Search: Navigating The Digital Landscape In 2024Search Engine Journal
The search marketing landscape is evolving rapidly with new technologies, and professionals, like you, rely on innovative paid search strategies to meet changing demands.
It’s important that you’re ready to implement new strategies in 2024.
Check this out and learn the top trends in paid search advertising that are expected to gain traction, so you can drive higher ROI more efficiently in 2024.
You’ll learn:
- The latest trends in AI and automation, and what this means for an evolving paid search ecosystem.
- New developments in privacy and data regulation.
- Emerging ad formats that are expected to make an impact next year.
Watch Sreekant Lanka from iQuanti and Irina Klein from OneMain Financial as they dive into the future of paid search and explore the trends, strategies, and technologies that will shape the search marketing landscape.
If you’re looking to assess your paid search strategy and design an industry-aligned plan for 2024, then this webinar is for you.
5 Public speaking tips from TED - Visualized summarySpeakerHub
From their humble beginnings in 1984, TED has grown into the world’s most powerful amplifier for speakers and thought-leaders to share their ideas. They have over 2,400 filmed talks (not including the 30,000+ TEDx videos) freely available online, and have hosted over 17,500 events around the world.
With over one billion views in a year, it’s no wonder that so many speakers are looking to TED for ideas on how to share their message more effectively.
The article “5 Public-Speaking Tips TED Gives Its Speakers”, by Carmine Gallo for Forbes, gives speakers five practical ways to connect with their audience, and effectively share their ideas on stage.
Whether you are gearing up to get on a TED stage yourself, or just want to master the skills that so many of their speakers possess, these tips and quotes from Chris Anderson, the TED Talks Curator, will encourage you to make the most impactful impression on your audience.
See the full article and more summaries like this on SpeakerHub here: https://speakerhub.com/blog/5-presentation-tips-ted-gives-its-speakers
See the original article on Forbes here:
http://www.forbes.com/forbes/welcome/?toURL=http://www.forbes.com/sites/carminegallo/2016/05/06/5-public-speaking-tips-ted-gives-its-speakers/&refURL=&referrer=#5c07a8221d9b
ChatGPT and the Future of Work - Clark Boyd Clark Boyd
Everyone is in agreement that ChatGPT (and other generative AI tools) will shape the future of work. Yet there is little consensus on exactly how, when, and to what extent this technology will change our world.
Businesses that extract maximum value from ChatGPT will use it as a collaborative tool for everything from brainstorming to technical maintenance.
For individuals, now is the time to pinpoint the skills the future professional will need to thrive in the AI age.
Check out this presentation to understand what ChatGPT is, how it will shape the future of work, and how you can prepare to take advantage.
A brief introduction to DataScience with explaining of the concepts, algorithms, machine learning, supervised and unsupervised learning, clustering, statistics, data preprocessing, real-world applications etc.
It's part of a Data Science Corner Campaign where I will be discussing the fundamentals of DataScience, AIML, Statistics etc.
Time Management & Productivity - Best PracticesVit Horky
Here's my presentation on by proven best practices how to manage your work time effectively and how to improve your productivity. It includes practical tips and how to use tools such as Slack, Google Apps, Hubspot, Google Calendar, Gmail and others.
The six step guide to practical project managementMindGenius
The six step guide to practical project management
If you think managing projects is too difficult, think again.
We’ve stripped back project management processes to the
basics – to make it quicker and easier, without sacrificing
the vital ingredients for success.
“If you’re looking for some real-world guidance, then The Six Step Guide to Practical Project Management will help.”
Dr Andrew Makar, Tactical Project Management
Unlocking the Power of ChatGPT and AI in Testing - A Real-World Look, present...Applitools
During this webinar, Anand Bagmar demonstrates how AI tools such as ChatGPT can be applied to various stages of the software development life cycle (SDLC) using an eCommerce application case study. Find the on-demand recording and more info at https://applitools.info/b59
Key takeaways:
• Learn how to use ChatGPT to add AI power to your testing and test automation
• Understand the limitations of the technology and where human expertise is crucial
• Gain insight into different AI-based tools
• Adopt AI-based tools to stay relevant and optimize work for developers and testers
* ChatGPT and OpenAI belong to OpenAI, L.L.C.
More than Just Lines on a Map: Best Practices for U.S Bike Routes
This session highlights best practices and lessons learned for U.S. Bike Route System designation, as well as how and why these routes should be integrated into bicycle planning at the local and regional level.
Presenters:
Presenter: Kevin Luecke Toole Design Group
Co-Presenter: Virginia Sullivan Adventure Cycling Association
Ride the Storm: Navigating Through Unstable Periods / Katerina Rudko (Belka G...DevGAMM Conference
Has your project been caught in a storm of deadlines, clashing requirements, and the need to change course halfway through? If yes, then check out how the administration team navigated through all of this, relocating 160 people from 3 countries and opening 2 offices during the most turbulent time in the last 20 years. Belka Games’ Chief Administrative Officer, Katerina Rudko, will share universal approaches and life hacks that can help your project survive unstable periods when there seem to be too many tasks and a lack of time and people.
Ride the Storm: Navigating Through Unstable Periods / Katerina Rudko (Belka G...
Hplc
1. Berkay AKKOÇ Sayfa 1 / 7
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HPLC
Yüksek performans sıvı kromotografisi (High Performance Liquid Chromatography : HPLC) ; en yaygın
olarak kullanılan analitik tekniklerden bir tanesidir.
Kromatografik prosesler, durgun ve hareketli fazlar arasında kütle transferini kapsayan ayırma teknikleri
olarak tanımlanırlar.
HPLC; bir karışımdaki bileşenlerin ayrılmasında sıvı hareketli fazı kullanır. Bu bileşenler ilk olarak
çözgende çözünürleştirilirler ve daha sonra yüksek basınç altında kromatografi kolonundan geçmeye
zorlanırlar.
Başlangıçta basınç; modern sıvı kromatografisinin temel kriteri olarak düşünülmekteydi ve bu nedenle
“Yüksek Basınç Sıvı Kromatografisi” olarak adlandırılmaktaydı.
Ancak bu günümüzde geçersiz kabul edilmektedir. Çünkü yüksek performans yalnız basıncın değil bir
çok faktörün birleşmesiyle ortaya çıkmaktadır.
Bu faktörler ;
-Dar bir dağılım aralığında çok küçük partiküllerin kullanılması,
- Uniform gözenek boyutu ve dağılımı,
- Yüksek basınçta kolon paketleme,
- Doğru, düşük hacimli örnek enjektörleri, - Duyarlı dedöktörler,
- İyi pompalama sistemi kullanımı,
olarak sınıflandırılır. Bu nedenlerden dolayı Yüksek Performans Sıvı Kromatografisi terimi
kullanılmaktadır.
HPLC’nin avantajları
• HPLC kolonu, rejenerasyon gerekmeksizin pek çok kez kullanılabilir.
• HPLC tekniği kullanıcının becerisine daha az bağımlıdır ve tekrarlanabilirlik daha yüksektir.
• Nicel analiz kullanılabilir.
• Analiz süresi kısadır.
• Duyarlık yüksektir.
Pompa Sistemleri
HPLC cihazlarının çoğundaki pompaların çıkış basıncı 1000 psi (libre/inc2) den büyüktür, dakikada 3 ml
hızla akış sağlayan 4000-6000 psi lik pompalar tercih edilir. Akış hızı % 2 lik bir toleransla sabit
olmalıdır. Bu amaçla kullanılabilen iki mekanik pompa tipi vardır; bunlar:
Vidalı (screw-driven) şırınga tipi pompalar
2. Berkay AKKOÇ Sayfa 2 / 7
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Pistonlu pompalar
Birinci tip pompalarda kolaylıkla kontrol edilebilen, darbesiz bir akım alınır; ancak kapasitede düşme ve
çözgen oranlarının değiştirilmesinde sorunlarla karşılaşılır. Pistonlu pompaların kullanım alanları daha
geniştir, kademeli olarak azaltılan miktarlarda darbeli bir akım verir. Pistonlu pompaların avantajı
istenildiği kadar çözgen basabilmesidir; ayrıca iç hacminin küçük olması dereceli sıyırma işlemi için
ideal bir durumdur (Şekil-4).
HPLC cihazlarında pnömatik pompalar da kullanılabilir; en basitinde hareketli faz, sıkıştırılmış hava ile
basınçlandırılan bir kabın içindeki portatif bir rezervuarda bulunur. Basittir, ucuzdur ve darbesiz akım
verirler; kapasiteleri ve çıkış basınçları sınırlıdır, çözgenin viskozitesine göre akış hızı değişir. Ancak
dereceli sıyırma işlemi için uygun değildir.
Pompalarla yüksek basınçlara çıkılmasının herhangi bir tehlike yaratmayacağını belirtmek gerekir,
sıvılar fazla sıkıştırılamadıklarından sistemin bir parçasında meydana gelebilecek kopma veya açılma
sadece çözgen sızıntısına yol açar.
Ön Kolonlar
Bazı HPLC cihazlarında çok bilinen ön kolonlar vardır. Ön kolonlardaki dolgu maddesi analitik
kolondaki dolgu maddesi ile kimyasal yapı bakımından aynidir, fakat tanecik boyutları daha büyüktür.
Böylece ön kolon boyunca olan basınç düşmesi, sistemin geri kalan kısmındakine kıyasla ihmal edilebilir
bir düzeydedir. Ön kolonun amacı, çözgendeki safsızlıkları tutarak analitik kolonun kirlenmesini
önlemektir. Ayrıca ön kolon hareketli fazı sıvı ile doyurarak sabit fazı oluşturur; böyle bir durumda
analitik kolondaki dolgu maddesinden sabit fazın sıyrılması işlemine gerek olmaz.
Örnek İnjeksiyon Sistemleri
HPLC'de en çok döner örnek valf sistemi kullanılır. Bazan kızak valflerde de kullanılmaktadır. (Şekil-
5b). Kızak, Kel-F'den üretilmiştir ve iki tetrafluoroetilen parçası arasındaki düzlemde hareket eder
3. Berkay AKKOÇ Sayfa 3 / 7
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konumdadır. Örnek valfe bir şırınga ile çekilir, sonra kızak soldan sağa doğru hareket ederek örneğin
solvent akımı içine girmesini sağlar.
Örnek injeksiyonu bir şırıngayla da yapılabilir. İnjektör İgnesi silikon, neopren veya teflondan yapılmış
bir conta (septum)'ya batırılarak sisteme verilir; injektör çekildiğinde conta kendi kendini kapatır.
Dedektörler
4. Berkay AKKOÇ Sayfa 4 / 7
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HPLC'de, gaz kromatografide olduğu gibi çok hassas dedektör sistemlerine gereksinim olmaz. Bu
nedenle örneğe bağlı olarak çeşitli dedektörler kullanılabilir. Tablo-1'de çok kullanılan dedektörler ve
özellikleri verilmiştir.
Ultraviole ve Görünür Işık Dedektörler
En çok kullanılan dedektörler ultraviyole veya görünür ışın absorbsiyonuna daya- nan dedektörlerdir.
Fotometreler ve spektrofotometreler ticari cihazlardır. Foto- metrelerde bir civa kaynaklan alınan 254 ve
280 nm bandları kullanılır; bu dalga boylarında pek çok organik fonksiyonel grup absorbsiyon yapar.
Spektrofotometrik dedektörler fotometrelerden daha elverişlidir, çünkü bunlarda örnekteki maddelerin
absorbsiyon yapacağı dalga boylarını seçme olanağı vardır. Fotometrik dedektörlerde cihazın dalga boyu
aralığında, örnekteki maddelerin ışığı absorblaması, fakat çözgenin herhangi bir absorbsiyona neden
olmaması gerekir. Asagida ultraviyole fotometrik bir dedektörün şematik diyagramı verilmiştir.
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Refraktif İndeks Dedektörler
Refraktif indeks bir bulk özelliğidir, dolayısıyla refraktif indeks dedektörünün algı- laması hareketli
fazdaki tüm komponentlerin toplam refraktif indeksine dayanır.
Refraktif indeks dedektörü en az hassas sıvı kromatografisi dedektörüdür; çevre sıcaklığı, basınç, akış
hızı değiştiğinde dedektörün algılaması da değişir. Çeşitli dezavantajlarına rağmen, refraktif indeks
dedektörleri, noniyonikler, UV bölgede absorbsiyon yapamayan maddeler ve flüoresans olmayan
bileşikler için çok uy- gun dedektörlerdir. Refraktif indeks dedektörleri çeşitlidir; diferansiyel refraktif
indeks, Fresnel metodu, Christiansen etki, interferometre, termal lens, dielektrik sabiti dedektörler gibi.
Şekil-8’da bir diferansiyel refraktif indeks dedektörünün şematik diyagramı veril- miştir. Burada çözgen
ve analit çözeltileri bir cam levha ile birbirinden ayrılmıştır. Cam levha, iki çözeltinin refraktif
indeksleri birbirinden farklı olduğunda gelen ışının sapmasını sağlayacak bir açı ile yerleştirilmiştir. Bir
ışık demeti optik mas- keden geçerek hücre bölmesine gelir. Mercekler demeti yönlendirerek örnek ve
referans hücrelerden geçmesini ve düz aynaya gelmesini sağlarlar. Ayna demeti yansıtarak tekrar örnek
ve referans hücrelerine gönderir. Mercekten geçen demet bir fotosel üzerine odaklanır. Demetin yerini
şiddeti değil, açısal sapması belirler; sapma, iki hücredeki maddeler arasındaki refraktif indeks farkının
bir sonucudur.
Fotoelektrik hücrede demetin odak konumu (yeri) değiştiğinde çıkış da değişir ve fark sinyal elektronik
olarak modifiye edilerek örnek hücresindeki madde konsant- rasyonuyla orantılı bir sinyal şekline
dönüştürülür.
Transport Dedektör
Tansport dedektör metal zincir, tel veya disk gibi bir taşıyıcıdır. Sürekli olarak kolon akımından geçer,
örneğin bulunduğu hareketli fazdan örneği ekstrakt eder ve yüzeyinde ince bir film tabakası halinde
biriktirir; film üzerinde kalan hareketli faz buharlaştırılarak uzaklaştırılır. Bu işlemden sonra taşıyıcı,
üzerinde biriken maddenin saptanması için uygun bir algılama sistemiyle taranır. Bu amaçla, ör- neğin,
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piroliz ürünlerinin saptanması istendiğinde alev iyonizasyon dedektörü (FID) kullanılır; bunun için
taşıyıcı ısıtılır, örnekteki piroliz ürünleri açığa çıkar ve ürünler çoğunlukla karbon içerdiğinden FID ile
algılanır.
Hareketli fazda uçucu olmayan maddeler bulunması halinde doğru sonuç vermez, ayrıca kullanılan
solventin uçucu ve çok saf olması gerekir.
transport dedektörlere bir örnek olarak hareketli tel (moving wire) dedektörün şematik diyagramı
verilmiştir. Bu tip bir dedektörde, sürekli hareket eden bir tel halka ile sıyırıcının bir kısmı bir alev
iyonizasyon dedektörüne taşınır. Tel önce sıyırıcıdan geçer, onu bir fırına taşır ve burada sıyırıcının
çözgeni buhar- laşır. Buradan azot atmosferi altında tutulan piroliz fırınına gelen örnek piroliz olur;
piroliz ürünleri azot gazıyla taşınarak alev iyonizasyon dedektörü (FID) için- deki merkez tüpe taşınır ve
bileşenler iyonizasyon dedektörü tarafından algılanır. FID, hareketli fazdaki solventten etkilenmeyen bir
dedektördür.
Elektrokimyasal Dedektör
Elektrokimyasal dedektör uygun elektrotların bulunduğu bir hücrede analitin oksit- lenme/indirgenme
reaksiyonları sonucunda oluşan akımın ölçülmesi esasına göre çalışır. Doğan akımın seviyesi doğrudan
analit konsantrasyonuyla orantılı olduğundan bu tip dedektörler kantitatif tayine olanak verir.
Elektrokimyasal dedektölerin uygulama alanı fazla geniş değildir; fakat hassasiye- tinin yüksek olması
nedeniye özellikle doğal ürünler ve yiyecek maddeleri incel- melerinde kullanılır. Oksijen, metal
kirlilikleri ve halojenler ölçmelerde önemli hata- lara neden olurlar.
Elektrokimyasal dedektörlerde üç elektrot bulunur; oksitlenme veya indirgenme reaksiyonunun olduğu
iş elektrodu, yardımcı elektrot ve referans elektrot. Referans elektrot hareketli fazın taban iletkenliğinde
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olabilecek değişiklikleri dengeler. Elektrotlar çeşitli geometrik şekillerde yerleştirilebilir; ince tabaka
hücrelerde en çok kullanılan yerleşimler şekil-10(b) ve (c)’degörüldüğü gibidir.