NOVEL DRUG DELIVERY SYSTEM

 

C) Condensation nucleus counters (CNC)
Condensation nucleus counters (CNC) serve to measure the numerical concentrations of particles. They are also called condensation particle counters (CPC) or Aitken nucleus counters (ANC). This technique is applicable to the detection of particles ranging from 2 nm to 3000 nm. Their generally slow response time means that the number of concentration peaks is underestimated. However, their integrated values remain reliable. Table 2 lists some commercially available devices and their range of use.

Table: 2 Commercial condensation nucleus counter

Manufacturer

 Device

Analytical range (nm)

BGI

 Pollack counter

>2.8 (1)

Environmental One

 Rich 200

 

Gardner

 CNC

 >3.8 (1)

TSI

 CPC 3007 (in real time)

 10 to >1000

TSI

 CPC 3022

 > 6 (2)

TSI

 UCPC 3025

 > 3 (2)

TSI

 P-Trak 8525 (in real time)

 20 to > 1000

TSI

CNC, model 3760

 > 14 (1)

MET

 CNC, model 1100

 > 10 (1)

KAN

CNC, model 3851

> 10 (1)

ACT

CNC, model 5000

> 50 (1)

D) Electrical mobility analysers
Devices using electrical mobility make it possible to classify particles or deposit them onsurfaces. They use the drift of a charged particle in an electrical field to classify or deposit it. Electrical aerosol analyzers (EAA) and differential mobility analyzers (DMA) classify particles. Electrostatic precipitators (ESP) allow deposition for subsequent laboratory analysis, by microscopy, for example. Apart from electrostatic precipitators, these devices must be used in series with different detection devices to determine the granulometry of an ultrafine or nanofine aerosol. Thus, an electrostatic precipitator or an electrical aerosol sampler (EAS) must be combined with an electrometer, while a differential mobility analyzer (DMA) must be used with a condensation nucleus counter or an electrometer to obtain a granulometry. All these devices require precisely controlled sampling of the aerosol to be analyzed before the mobility analyses and their conversion into granulometry measurements. These techniques are difficult to apply for particles smaller than 10 nm because these particles are difficult to charge. The scanning mobility particle sizer (SMPS) and the differential mobility particle sizer (DMPS) are very bulky and barely portable. However, they rank among the best devices available for analysis of particles between 5 and 800 nm or between 8 and 200 nm. The SMPS is an EAA combined with a CNC, while the DMPS is a DMA connected in series with a CNC. The main devices and techniques and their range of application are listed in Table 3.

Table: 3 Main electrical mobility analysers

Manufacturer

 Device or technique

 Analytical range (nm)

 

SMPS

5 to 800 (1)

In Tox Products

ESP (with an electrometer)

> 30 (2)

Hauke KG

 Hauke-Aeras(SAAS3/150)

3 to 150 (2)

University of Vienna

EMS VIE-06(requires a CNC)

 

TSI

 SMPS model 3071

 10 to 350 (3)

 

            MAS

 < 100

TSI

 EAS model 3100

 < 500

TSI

DMPS model 3092

 10 to 1000 (4)

TSI

DMPS model 3932

10 to 1000 (2)

E) Cascading impactors
Impactors allow separation of aerosol particles into different granulometry brackets. Each granulometry bracket is associated with a stage of the impactor, on which a collection substrate or a detection element is placed. Impactors offer the advantage of allowing subsequent analysis of particles on the collection substrates and gravimetric determinations. In general, the most common impactors have a range of use between 50 and 30,000 nm.

A wide range of impactors exist but some have been developed specifically for ultrafine particles. They have a lower detection limit. Among them, the micro-orifice uniform deposition impactor (MOUDI), model 110 can classify particles from diameters of 56 nm to 15000 nm while the nano-MOUDI allows three-stage collection of 32, 18 and 10 nm nanoparticles. Table 4 presents some commercial impactors usable for nanoparticles.

Table: 4 Some commercial impactors usable for nanoparticles

Manufacturer

 Device

 Analytical range (nm)

Atmospheric Technology

 Low pressure impactor

 50-4000 (1)

Andersen Samplers Inc

 Low pressure impactor

80-35000 (1)

Hauke KG

 Berner impactor

63-16700 (1)

MSP corporation

MOUDI

 56-18000 (1)

MSP corporation

Nano-MOUDI

 10 – 32

PIXE International Corp.

 Orifice impactor (model 1L-CI)

 60-16000 (1)

Dekati

 Electrical low pressure impactor (instantaneous measurements)

7- 10 000

F) Direct surface measurement devices
No instrument is fully adapted to personal or fixed station surface measurements for aerosols. The epiphaniometer is the only instrument developed for nanoparticles and specifically for this type of measurement. It can provide the total surface measurement of particles between 10 and 1000 nm. This instrument is bulky and has the disadvantage of using radioactive source, which complicates and restricts its use in the work environment. However, an aerosol’s specific surface can be measured from an aerosol’s granulometric distribution by assuming a specific geometry of the particles. Surface measurements can also be performed from samples collected by the Brunauer Emmett Teller (BET) adsorption method, using nitrogen or CO2. This technique allows measurement of all the inner surfaces of the pores. It thus gives a better estimate of the total surface presented by an aerosol than the measurement based on SEM or TEM electron microscopy.  However, this method requires the use of large sample quantities and does not allow nanoparticles to be differentiated from other particles. The few commercially available devices are presented in Table 5.

Manufacturer

 Device

 Analytical range

Micromeritics Instruments Co

 FlowSorb III 2305/2310 (B.E.T.)

 > 0.01 m²/g

Paul Scherrer Institute

Epiphaniometer4

 0.003 μm² /cm³

Ecochem

 Standard Particulate Monitor LQ1-DC

 

Table: 5 Particle surface determination devices

There is consensus on the current limitations of industrial hygiene measuring instruments and the need to develop new instruments adapted to nanoparticle specificities, as well as the absence of reference standard nanoparticles that can be used to calibrate instruments. Simultaneously, the availability of nanomaterials will allow development of new measuring tools applicable to a wide range of environmental situations, in the work environment, in the medical field, etc.

NOW YOU CAN ALSO PUBLISH YOUR ARTICLE ONLINE.

SUBMIT YOUR ARTICLE/PROJECT AT articles@pharmatutor.org

Subscribe to Pharmatutor Alerts by Email

FIND OUT MORE ARTICLES AT OUR DATABASE


Pages

FIND MORE ARTICLES