Author Archives: Rachel Kohn

About Rachel Kohn

So how did an MIT Ph.D. end up selling refrigerators? When I figured out that a lot more scientists buy lab refrigerators than innovative leading-edge instruments. I hope that my many years of lab experience will help you find the right equipment for your work. Before co-founding Tovatech I worked in business development and project management at Smiths Detection, Photon-X, Cardinal Health, and Hoechst Celanese. And before that I spent 12 years as an R&D chemist at Hoechst Celanese and Aventis working on advanced drug delivery systems, polymer films and membranes, optical disks, and polysaccharides. Some day, eventually, I’ll make enough money to develop an innovative technology that will change the world.

How to Select the Best Flammable Liquid Ultrasonic Cleaner

Ultrasonic Cleaning with Flammable LiquidsFlammable liquid ultrasonic cleaners may often be required when contaminants are difficult to remove and where residues that may remain after using conventional water-based biodegradable cleaning solutions are unacceptable.  Flammable liquid (also called volatile solvent) ultrasonic cleaners can overcome these challenges as we will explain later in this post.

But first a short tutorial.

What is a Flammable Liquid?

They are not all exactly the same.  Flammable liquids have different flashpoints. In brief, the lower the flashpoint the more flammable they are, which is an important consideration when specifying an ultrasonic cleaner for flammable liquids.  

The American Chemical Society publishes a table of  common organic solvents that includes flash points.  Examples of low flash point volatile solvents are 1-propanol at 59⁰F, acetone at -4⁰F and toluene at 39⁰F.  Solvents with higher flashpoints include NEP (N-Ethyl-2-pyrrolidone) or NMP (N -Methyl-2-pyrrolidone) at or above 131˚F.

It’s the Fumes, Stupid!

In chemical terms … Read the rest

How to Choose a Lab Refrigerator or Freezer

How to Choose a Lab Refrigerator or FreezerSelecting a laboratory refrigerator or laboratory freezer is not the same as visiting the local appliance store to pick out a unit for your kitchen.  There are substantial differences.  Not only that, there is a tremendous variety of models available in terms of capacity and performance features. 

This post quickly describes differences between household and laboratory refrigerators and freezers. Then we’ll looks into the many feature options available and help you select the model that meets your requirements.

How to Pick the Best Ultrasonic Cleaner

Selecting the Best Ultrasonic CleanerTips on Selecting the Best Ultrasonic Cleaner

So, you’ve landed here because you’ve heard about ultrasonic cleaning and how wondrous it works in removing almost any contaminant from almost any surface that can be immersed in an aqueous cleaning solution.  The task you have now is how to select the best ultrasonic cleaner for the cleaning challenges you have in mind. 

Here we offer some useful suggestions.

Why Selecting an Ultrasonic Cleaner is Important

If you’re interested in selecting an ultrasonic cleaner for your cleaning operations you’ve probably done a bit of research and found that choices seem endless.  The range of sizes, shapes, features and pricing is further complexified (our word) by prices for the units.  How do you select an ultrasonic cleaner and be assured that it will do the job you expect of it?  

This post does not get into pricing.  What we hope to do here … Read the rest

How to Select an Ultrasonic Cleaning Solution

ultrasonic_cleaing_solution_selection_v3Benchtop and industrial ultrasonic cleaners provide outstanding cleaning results in thoroughness and speed for applications from watch making to jet engine components and virtually anything in between that can be safely wetted.  Largely responsible for this is the variety of ultrasonic cleaning solutions provided by manufactures to target both broadly defined and highly targeted cleaning challenges. Selecting the right ultrasonic cleaning fluid is not a hit-or-miss proposition.  Several considerations come into play.  

Ultrasonic Cleaning Solution Selection Tip No.1

What is the contaminant?  Put another way, what do you want to remove by an ultrasonic cleaning process?  Examples include

  • grease, grime and grit on engine and drive train components
  • salt and other residues on scuba gear
  • soldering residues and other contaminants on PCBs
  • burned on plastic injection mold deposits
  • grit and grime on cherished vinyl LP records
  • contaminants on surgical and dental instruments
  • tarnish or old paint on brass, copper and
Read the rest

How a Digital HPLC Liquid Flow Meter Works

HPLC Liquid Flow MeterBefore explaining how HPLC liquid flow meters work here’s an explanation of what digital HPLC flow meters do:  Digital HPLC flowmeters are used to measure the accuracy of High Performance Liquid Chromatography pumping systems in order to meet FDA and other regulations regarding installation qualification (IQ), operational qualification (OQ) and performance qualification (PQ) of equipment used in the pharmaceutical and biopharmaceutical industries as well as other analytical labs.

The process demands accurate, reproducible column retention time as an analyte (what is being analyzed) is pumped through the HPLC system.

These precision instruments are not to be likened to flow meters used on process lines measuring flow rates in, for example, thousands of gallons per minute but instead in fractions of milliliters per minute.

Why HPLC Pump System Accuracy is Important

As suggested above, meeting regulations (and protecting a company’s reputation) is the reason.  Consistent accurate performance is an absolute necessity. … Read the rest

How to Calibrate Precision Scales and Analytical Balances

Control panel for the Kern HCN Hanging Scale

Control panel for the Kern HCN Digital Hanging Scale

Before we describe how to calibrate precision scales and analytical balances we’ll tell you why you need to calibrate these precision weighing devices.  In many instances it’s required by law but in all cases calibrating these instruments, especially those used in R&D labs and other demanding applications, should be conducted on a regular basis as a part of good laboratory practices (GLP).

Calibration exercises apply to other types of scales for many of the same reasons.  Buyers and sellers of products want to get and give “fair measure.”  For the purpose of this post we’ll focus on precision scales and analytical balances where deviations between actual weight and displayed weight can be unacceptable.  Calibration exercises are aimed at making the scales as accurate as possible.  

In addition to explaining how to calibrate these weighing instruments this post first goes into detail … Read the rest

Avoiding Errors with Analytical Balances

Avoiding Errors with Analytical Balances

Avoiding errors when using analytical balances – or for that matter any weighing instrument – involves the coming together of several practices on the part of the user.  This post focuses on assuring accurate weighing results when using analytical balances with readouts (what is displayed on the instrument) to milligrams.    For an analytical balance such as the KERN ABT 120-4M available from Tovatech it is 0.1 milligram.   Semi-micro balances can display to micrograms or 0.01 milligram.

Accuracy is paramount when weighing to these levels with analytical balances and is often subject to regulation by organizations such as the FDA and professional trade associations.  Technicians must institute practices and procedures to avoid weighing errors and to insure that the displayed weight precisely reflects the weight of the sample.

Ultrasonic Cleaners for Flammable Solvents

ultrasonic cleaning using flammable solvent

Ultrasonic cleaners are widely recognized as providing outstanding cleaning action thanks to the cavitation produced by the equipment’s generator powered ultrasonic transducers.  But when cleaning with flammable solvents it is imperative that explosion resistant ultrasonic cleaners are employed in the shop, and that the equipment be located in an area equipped with an adequate exhaust system to vent fumes to an exterior location.

Flammable solvents are often preferred for tough cleaning jobs such as degreasing and removing tenacious contaminants like paint and adhesive residues.  Special care must be exercised when cleaning with flammable solvents under any circumstance, but especially when using an ultrasonic cleaner to both speed the process and improve cleaning results.   Unless they are specially constructed, ultrasonic cleaners present two risks:  sparks from internal electronics igniting spilled solvents and fumes, and vapors from solvent evaporation creating a hazardous area in the vicinity of the unit.   … Read the rest

Selecting and Using Precision Scale Test Weights

Calibrating Scales with Test Weights

Weighing accuracy is a primary criterion for precision scales, analytical balances and moisture analyzers where readout (the smallest weight difference displayed) and linearity (the ± deviation from the actual weight) are governed by GLP, ISO and other standards.  Test weights have a critical role to play when scales  with capacities from milligrams to tons are not automatically internally (see below) calibrated . The type of calibration, whether internal or external, is indicated on scales’ spec sheets.

Selection Tips for Precision Digital Scales

10 Selection Tips for Precision Digital Scales

Today’s precision digital scales, also referred to as digital balances, perform a broad range of weighing-related functions in R&D, quality control, and similar applications where accuracy and precision are key criteria to meeting government, trade association, and industry-promulgated standards.  For purposes of discussion this post focuses on weighing equipment used in comparatively protected environments vs. scales found on manufacturing floors, shipping and receiving departments.  Let us hasten to add, however, that the need for precision and accuracy is important for any application, and equipment is available to meet required standards regardless of where scales are employed.

Precision and Accuracy Defined

Certain of our posts discussing precision digital scales and analytical balances harp on an important difference between precision and accuracy as selection criteria.  Allow us to cite an example:  A $5,000 wristwatch may be precise, but if the hands are set wrong it does not show the accurate time.  More … Read the rest