Report for Analytical Chemists
For determining the safety of water for drinking and general use EVERYTHING NECESSARY FOR MULTIPLE TUBE DILUTION METHOD COLIFORM BACTERIA TESTS
Now there is no need to sterilize media, sample tubes, glassware, dilution water and pipets for multiple tube Coliform determinations. Hach furnishes everything to meet U. S. Public Health Service standards including Lactose and Brilliant Green fermentation tubes completely sealed for protection. Order whatever items you need—individual tubes, glassware, incubator or the works. Write for list of supplies, prices, catalog and procedures today.
HACH CHEMICAL
COMPANY
HACH
P.O. BOX 907 / Ames, Iowa 50010 USA / 515-232-2533 Products for water analysis and pollution control CIRCLE 1 0 0 O N READER SERVICE CARD
Let ISCO high pressure you
ISCO instruments for high pressure l i q u i d c h r o m a t o g r a p h y give you high speed separation at low speed cost. Metering and gradient pumps operate at 2000 psi with single stroke piston construction to eliminate pulsation and dissolved gas; stainless steel columns have non-clogging supports and fittings with no dead volume or mixing. Effluent is monitored by a dual beam, high sensitivity UV photometer with seven absorbance ranges from 0.02 A to 2.0 A full scale, and instant wavelength selection of 254 nm, 280 nm or other wavelengths to 950 n m . The w h o l e chromatograph as pictured —pump, column (unpacked), photometer, recorder, sample injection valve, and degasser, with gauge and other hardware, costs under $3,450. Plug your present recorder into the photometer and save $750; or add less than $2500 more to include a fraction collector and electronic digital integrator with fully automatic c o m pensation for peak shape and baseline drift. Many additional features and options are available, all described in our current catalog. Send for your copy now.
INSTRUMENTATION ISCO
BOX 5347
SPECIALTIES
LINCOLN, NEBRASKA 68505
PHONE (402) 434-0231
CIRCLE 1 0 8 O N READER SERVICE CARD
36 A ·
ANALYTICAL CHEMISTRY, VOL. 44, NO. 8, JULY 1972
COMPANY TELEX 48-6453
sample. Many automated analytical procedures require that the sample be preclarified to a significant degree for the protection of the analyzer. Therefore, the analyses obtained are biased by any removal of materials of interest through clarification. Automated monitoring stations usually require the transfer of a sample by pumping through a transfer line. It is difficult to acomplish this transfer without a detectable change in the character of the sample. Deposition on walls and pipes, changes in size of suspended solids, and absorption of soluble materials on walls of pipes may have a significant effect on the representative nature of the sample as delivered to the sensors of the monitoring system. From an admissible evidence point of view, recorded data by a monitoring system are difficult to qualify, because the status of operation of the monitoring station can only be testified to for those brief periods of time when direct supervision and calibration of the system are made. Therefore, currently, enforcement data by EPA are developed from manually collected samples. Utilization of monitoring data in enforcement actions is a practical consideration for the future, but as yet, it is untried. EPA considers that examination of flowing water in a stream does not represent a total approach to water quality. Sediment samples from the bottom of streams should be examined also. The sediments represent deposits from previous stream transport or precipitation of solids. If toxic materials are present in the sediment which may transfer into the food chain and hence to aquatic life or may be lifted by turbulences to the main flow of the stream, the sediment is a hazard ,to water quality. The analytical quality control laboratory of EPA is also very much concerned with the quality
