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Pipet-Aid® XL


Advanced


Ergonomics for Working Under a Hood


Reduce Strain Longer lightweight handle enables lower, more comfortable arm position


Extend Uninterrupted Operation Periods Quiet more efficient pump can be charged while in use to eliminate downtime


Excellent Control Three speed settings enable precise volume control for both aspiration and dispensing operations


The Pipet-Aid® XL is designed specifically to reduce the strain involved when pipetting under a hood.


For a copy of our new 2013 catalog or more information on the Pipet-Aid XL visit drummondsci.com.


From the Developers of the Original Pipet-Aid®


MADE IN USA


500 Parkway, Box 700 Broomall, PA 19008


RAPID FOOD SAFETY SCREENING continued


(BN) gate (3). After the mobility-based separation in the drift region (4), the ions are detected at a Faraday plate detector (5). Table 1 provides the HPIMS instrument settings used for the experiments discussed.


Figure 1 conceptually demonstrates HPIMS. The gas phase ions of a sample’s components are separated in the drift region (4) based on their differences in structural size and shape that cause them to “move” differently based on collision interactions with a counter-flowing neutral drift gas as an electric field guides them. Smaller, more compact ions (green shapes) arrive at the detector before larger, bulkier ones do (red and orange shapes), analogous to time-of-flight (TOF) methods. This separation mechanism is orthogonal to both mass spectrometry (MS) separation based on mass-to-charge ratio (m/z), and LC, which separates by polarity. Consequently, HPIMS gives valuable information about the molecules in a sample in a very short time, requiring only milliseconds for ions to travel the length of the drift tube, with complete averaged spectra obtained in under 60 sec.


To achieve its performance metrics in Table 2,14 HPIMS leverages advances


in ion mobility instrument construction to provide the speed and simplicity of IMS with figures-of-merit comparable to high-performance and ultra- high-performance liquid chromatography (HPLC and UHPLC) methods traditionally used in food screening. The resolving power, R, for IMS can be defined as the ratio of the drift time, td wh = Δ1/2td.4,14


, to the peak width at half-maximum, HPIMS routinely gives R of 60 to 70, comparable to HPLC and


UHPLC methods. Similarly, the number of theoretical plates (N) for HPIMS using the ratio14


5.55(td/wh)2


LC methods. However, the HPIMS analysis typically completes in as little as 10 sec, giving almost 200-fold improvement in throughput (N/sec) vs LC.


ESI-HPIMS detection of phthalates, additives,


and residues Phthalate plasticizers are commonly used in the manufacture of ev- eryday items such as personal care products (PCPs), toys, and food packaging.15


compounds is mounting16


Concern over frequent, long-term exposure to these because of evidence supporting their role


as endocrine disruptors that increase developmental abnormalities and impair reproduction and development.17–19


Phthalates have further


been used as illicit clouding agents in food and drinks produced outside of the United States.20


has been demonstrated using ESI-HPIMS.11


Previous proof-of-concept experiments show that ESI-HPIMS is adept at detecting the main phthalate compounds banned internationally, even in food matrices.11


An array of 12 phthalates could be detected to ppb


levels with a 1.5 order-of-magnitude linear response range, producing [M+nH]n+


and [M+Na]+ peaks. The previous work has used a traditional


infusion-type ESI source, requiring long times to clean the capillary lines between analyses.11


Therefore, Directspray ESI has alternatively been


used to detect dicyclohexyl phthalate (DCHP, ULTRA Scientific, North Kingstown, RI) in cola for faster sample analysis.


First, a blank 90:10 methanol:water ESI solvent was analyzed with the Directspray ESI-HPIMS in positive ion mode. Next, 100 µL of off-the-shelf cola was diluted with 900 µL of methanol, and the mobility spectrum for the blank cola matrix was measured. The same dilution with another 100


AMERICAN LABORATORY • 12 • JUNE/JULY 2013 Therefore, detection of phthalates in beverages is up to 27,000, again very similar to the two


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