Although not the sexiest of instrument techniques, refractometry is a useful method that is widely applied in routine analyses. Its low cost and simplicity make it attractive for applications as distinct as beer brewing and the hydration levels of athletes. Growth in demand tends to be slower but more stable than many other analytical techniques, and it is a market in which numerous smaller and more focused vendors compete heavily.

The refractive index (RI) of a substance, typically a liquid, is a measurement of how visible light propagates through it and can be calculated by measuring the critical angle using a refractometer. RI is a unitless number and is between 1 and 2 for most transparent media. The RI of a solution does not provide any chemometric information, such as compound identification or structure, but does provide a quick and easy method to calculate the density or concentration of a solution. The RI, in turn, can be converted into sugar concentration (Brix), specific gravity or another concentration value. RI is affected by temperature but more advanced portable refractometers have built-in temperature correction. Simpler instruments are designated for use at specified temperatures. Portable refractometers are typically available to measure a specific measurement range for a given application. They are generally very simple instruments, which makes them generally rugged and inexpensive.

The capabilities of refractometers make them popular in the agriculture and food industry, where they are used for checking the sugar concentration of drinks including juices, soda, beer and wine. In fact, refractometers are so widely used for such applications that RI is converted to degrees Brix (°Bx), which translates into the number of grams of sucrose per 100 grams of solution.

Portable refractometers are also used in the chemicals industry, specifically to analyze a wide range of automotive-related chemicals, like the freezing point of antifreezes and the quality of brake fluid. Portable refractometers are also used in the hospital and clinical sector to measure urine-specific gravity and total protein in blood plasma or serum. Although neither of these measurements provide specific diagnoses, they can indicate potential health problems.

The market for portable and handheld refractometers was more than $40 million in 2011 and tends to average low to mid-single digit annual growth. Although it is a very mature technology that lacks the potential for technological advances to stimulate growth, demand is heavily tied to relatively stable industries. This will help to limit any contraction in the market in what is expected to be a weak 2013, while also capping the potential for a later dramatic jump in demand. There are dozens of small competitors in the market, as refractometers are quite simple to manufacture, although quality can vary significantly. Distributors play a significant role in the market, as such low-cost instruments are often sold via catalogs.

Portable and Handheld Refractometers at a Glance:

Leading Suppliers

• ATAGO

• Hanna Instruments

• Bellingham+Stanley (Xylem)

Largest Markets

• Agriculture and Food

• Chemicals

• Hospital/Clinic

Instrument Cost

• $24–$2,600