Water Research Vol. 14. pp. 1645 to 1650 0043-1354 80 1101- I ,~IS~)2AX)0 C~ Pergamon Press Ltd 1980. Printed in Great Britain USE OF AN OXIDATIVE DESTRUCTION AND QUADRUPOLE MASS SPECTROMETRIC(QMS) DETECTION FOR THE DETERMINATION OF THE ORGANIC ELEMENTAL COMPOSITION OF SUSPENDED MATTER IN SURFACE WATER H. F. R. REIJNDERS l, D. ONDERDELINDEN 1, M. G. VISSER 2 and B. GRIEPINK 2 t National Institute of Public Health, Anthonie van Leeuwenhoeklaan 7, 2560 BA Bilthoven and 2Laboratory for Analytical Chemistry, Utrecht University, The Netherlands (Received May 1980) Abstraet--A study was made of the applicability of a system consisting of a combustion followed by QMS-detection for the determination of the elemental composition of organic matter suspended in surface water. The solid material obtained from several types of water was collected by centrifugation. The results show possible applications e.g. in the field of water characterization. A complete elemental analysis including pretreatment takes about 30 rain. Znltmmtffssmmg--Die Anwendung einer Kombination yon Verbrennung und Detektion der Verbren- nungsprodukte mittels QMS zur Ermittlung der Elementzusammensetzung von in Wasser suspendier- tern organischen Maierial wurde studiert. Die FestkSrper wurden mittels Centrifugation abgetrennt. Die Ergebnisse weisen mtigliche Anwendungen auf, z.B. bei der Wasserkennzeichnung. Eine Elementarana- lyse inkl. Vorbehandlung ftirdert etwa 30 Min. The elemental composition of organic parts of the For both research objects the analysis should meet insoluble matter in surface water is of increasing certain demands. The first demand is that various ele- interest in the study of water pollution and the eluci- ments should be determined. Sulphur for example is dation of the various mechanisms involved in the an important constituent of certain proteins and their metabolization of waste and natural organic material, metabolites and should therefore be determined. The composition of the organic material is rather Another demand is that the determinations can be complex, because many industrial co~npounds and carried out on a routine basis to be able to analyse a metabolites of fats, proteins and carbohydrates may large amount of samples necessary for correlation and occur. Therefore a complete structural analysis giving model studies. For a first investigation the demands the type of compounds and their concentration is with regard to the accuracy of the method are less unpractical and nearly impossible, rigid than in usual elemental analysis of organic corn- Elemental analysis, however, may give useful infor- pounds. mation on the type of the compounds, e.g. fats or These considerations lead us to investigate the use proteins, present. Recently Baumeister (1978) per- of the destruction/QMS-combination recently pub- formed CHN-analyses on the suspended matter lished by van Leuven(1970, 1973). present in surface water. He found a rather uniform C/N-ratio in the particles from various samples. This may indicate a merely biogenic origin. EXPERIMENTAL As micro-organisms and pollutants have a tendency to grow resp. to be adsorbed on solid particles, the Reagents amount of organic material on the solid particles and For calibration of the apparatus S-benzyl-thiuromium hydrochloride and 4-chlorobenzoic acid are used. These its composition may be useful to characterize the type reagents are abbreviated as PTU and CBA respectively. of water. So in our first investigation we sampled completely different water sources (Table 1). Apparatus The tempot'al behaviour of the elemental compo- A diagram of the apparatus is given in Fig. 1. The com- sition might also provide a means to obtain a better bustion tube (i.d. 24 mm) is heated to a temperature of knowledge and understanding of the chemical and approx. 1000°C in a furnace (Heraeus ROK 30 and biological processes in the water. The direct study of REK 19120). The tube is separated in two compartments I these mechanisms in surface water may be too corn- and II by means of a partition of quartz glass provided with an opening of 10 mm allowing passage of gasses. plicated yet. For the study of these processes in con- The sample is weighed in a platinum boat with an elec- trollable model systems, elemental analysis could be trical microbalance (Cahn 270). The boat is introduced on useful, a quartz spoon(s) in compartment I. Organic material is 1645 W.R. 14/11--1: 1646 H.F.R. RELIIqDEKSet al. Table 1. Origin of the samples, corresponding amount of suspended matter, inorganic fraction (w/w) and suspected source of organic material Suspected source Suspended Sample of the organic matter Inorganic number Origin material (mg 1- t ) fraction l Effluent of a wastewater treatment plant Sewage water 134.0 0~25 2 Effluent of a wastewater treatment plant , Sewage water 103.0 0.24 3 Lek (river) Various 38.0 0.80 4 Ditch Various 54.4 0.64 5 Vecht (river) Various 9.4 0.58 6 Amsterdam-Rijnkanaal (canal) Various 13.3 0.75 7 Merwedekanaal (canal) Various 20.0 0.78 8 Vaartse Rijn (canalised river) Various 8.5 0.69 9 Catharijnesingel Utrecht (canal) Sewage water 15.1 0.65 10 Kromme Rijn (canalised river) Industrial wastes 14.2 0.66 11 Nieuwe Gracht Utrecht (canal) Various 12.6 0.65 12 Biltse Grift (brook) Sewage water 14.7 0.55 combusted in an oxygen atmosphere. The oxygen, deliv- the ions pass the mass filter and are selected to mass to ered via flow rator R I (80 ml/min- i) not only supplies oxy- charge ratio. gen for combustion but also avoids entry of ambient air by Masses are scanned by varying the a.c.-voltage applied flushing oxygen through the entrance (el The combustion to the mass filter+ A computer program (CAMAC-proces- is catalysed by Pt-wool (w) which is squeezed in the open- sor} controls the detection in such a way that the ion cur- ing in the partition. In compartment II the combustion is rent at a sequence of twelve different mass units ~s completed. Tim oxygen is supplied via flow rator R2 (25 mi measured repeatedly and recorded. The time needed for the min-+)andflowrator R3ffml/min-t).The oxygen stream measurement at every mass to charge ratio amounts to through R3 is humidified prior to passage in a gas washing 70 ms which includes step,time, dead time. sampling time. bottle filled with water. This gas washing bottle is thermo- converting time and computation time. During the corn- stated in a water bath (temp. approx. 25°C). From com- plete combustion every mass fraction is measured 270 partment II the gasses enter the gnsspfitteT (gs) via the first times. The ion current on combustion of a sample at one pressure reduction device Pt. The pressure reduction is mass to charge ratio ]s presented in Fig• 2. The actual variable and eanbe set manually by cock c. The pressure is measurement takes about 210s. The background current is maintained by a rotati+ng vacuum pump. The gasses are measured during 105 s before and after the combustion introduced in the quadrupole mass spectrometer (QMS) (t,-t2, t3-t4 resp.). via the second pressure reduction device P2 consisting of a The CAPRO-sys~em sums the several collected ion cur- capillary (i.d. 0.5 mini and Pt.wire. The pressure reduction rent values per mass to obtain the area under the time can be set by varying the length of Pt-wire in the capillary, curve. These values from the CAPRO-system are read out The pressure in the QM$ is maintained with a turbomole- via a terminal on paper tape. The processing of data is cular pump (Pfeilfer TPU 200). The mass spectrometer is a carried out by a 21 MX computer after reading the data Balzers QMG 311. The QMS has a thorium-iridium cath- from paper tape. The signal from the QMS-electronics may ode for the electron-impact ionization. After accelerating+ he monitored on an oscilloscope. ,, , i t z ¢ i"~ i as-~ I .......... /I I,I Fig. 1. Scheme of the analyser. Composition of suspended matter in surface water 1647 I % I *'%. ion -current I t 1 t 2 t 3 t 4 time it background Fig. 2. Ion current (output multiplier) on combustion of a sample at one mass to charge ratio. Samplino metal salt containing S or C. So we concluded that no Five litres of surface water were sampled with an matrix effects for sulphur and carbon occur in this system. aluminium device. Whirling of the silt on the bottom of the sampling site was carefully avoided. The sample was trans- ported in a metal container. The sample storage time was RESULTS always less than two days. Table 1 gives an indication of water type and origin Procedure together with the amount of suspended matter and The sample is divided in 1 I. aliquots. Th~e aliquots are the inorganic fraction. The variation in" these two par- centrifuged at 2400rpm during 5min. The liquid is decanted. The solid residues are gathered and centrifuged ameters indicates the large difference in water quality once more. The solid is dried in a dessicator above silicagel at the several sampling sites. Results obtained by ana- to constant weight. Subsamples containing about I mg of iysing samples from various origins are presented in organic material are taken. Subsamples are burned in the Table 2. The results for chlorine were under its lower combustion tube. Ion currents (at mass to charge ratios of 18, 44, 14, 64 and 36) are measured for determination of H, limit of detection (15 #g). As a consequence they are C, N, S and CI. After a combustion the weight of the omitted.